Mon. Not. R. Astron. Soc. 362, 127Ð166 (2005) doi:10.1111/j.1365-2966.2005.09274.x
GHASP: an Hα kinematic survey of spiral and irregular galaxies – IV. 44 new velocity fields. Extension, shape and asymmetry of Hα rotation curves
, O. Garrido,1 2 M. Marcelin,2 P. Amram,2 C. Balkowski,1 J. L. Gach2 and J. Boulesteix2 1Observatoire de Paris, section Meudon, GEPI, CNRS UMR 8111, Universite Paris 7, 5 Place Jules Janssen, 92195 Meudon, France 2 Observatoire Astronomique de Marseille Provence, Laboratoire d’Astrophysique de Marseille, 2 Place Le Verrier, 13248 Marseille Cedex 04 France Downloaded from https://academic.oup.com/mnras/article/362/1/127/1339746 by guest on 30 September 2021
Accepted 2005 June 3. Received 2005 May 26; in original form 2004 August 24
ABSTRACT We present FabryÐPerot observations obtained in the frame of the GHASP survey (Gassendi HAlpha survey of SPirals). We have derived the Hα map, the velocity field and the rotation curve for a new set of 44 galaxies. The data presented in this paper are combined with the data published in the three previous papers providing a total number of 85 of the 96 galaxies observed up to now. This sample of kinematical data has been divided into two groups: isolated (ISO) and softly interacting (SOFT) galaxies. In this paper, the extension of the Hα discs, the shape of the rotation curves, the kinematical asymmetry and the TullyÐFisher relation have been investigated for both ISO and SOFT galaxies. The Hα extension is roughly proportional to R25 for ISO as well as for SOFT galaxies. The smallest extensions of the ionized disc are found for ISO galaxies. The inner slope of the rotation curves is found to be correlated with the central concentration of light more clearly than with the type or the kinematical asymmetry, for ISO as well as for SOFT galaxies. The outer slope of the rotation curves increases with the type and with the kinematical asymmetry for ISO galaxies but shows no special trend for SOFT galaxies. No decreasing rotation curve is found for SOFT galaxies. The asymmetry of the rotation curves is correlated with the morphological type, the luminosity, the (B − V ) colour and the maximal rotational velocity of galaxies. Our results show that the brightest, the most massive and the reddest galaxies, which are fast rotators, are the least asymmetric, meaning that they are the most efficient with which to average the mass distribution on the whole disc. Asymmetry in the rotation curves seems to be linked with local star formation, betraying disturbances of the gravitational potential. The TullyÐFisher relation has a smaller slope for ISO than for SOFT galaxies. Keywords: catalogues Ð galaxies: dwarf Ð galaxies: interactions Ð galaxies: irregular Ð galax- ies: kinematics and dynamics Ð galaxies: spiral.
cal and photometric axes are confused. GHASP galaxies were first 1 INTRODUCTION chosen to cover the ‘galaxy massÐgalaxy morphological type’ plane This paper is the fourth of a series presenting and analysing the for a large range of luminosity (−15 Mb −22) and morpholog- observational data obtained in the frame of the GHASP survey ical types (from Sa to irregular). We estimate that a total sample of (acronym for Gassendi Hα survey of SPirals). This survey consists about 200 galaxies is necessary (see Garrido et al. 2002) to cover in mapping the distribution of the ionized hydrogen of field galaxies the whole ‘MB–type’ plane. Furthermore, they were chosen in low- using a scanning FabryÐPerot interferometer at the 1.93-m telescope density environments, excluding cluster, group or pair galaxies. This of the Observatoire de Haute-Provence (OHP). High-resolution 2D survey will provide a homogeneous reference sample at z = 0of velocity fields (with a sampling about 5 km s−1 in velocity and 3 2D Hα velocity fields (the largest by now after that of Schommer arcsec in spatial resolution) in the Hα line of hydrogen are derived. et al. 1993, which concerns cluster galaxies in the southern hemi- Velocity fields enable us to deduce rotation curves in a more robust sphere) and will allow us to study the mass distribution all along the way than slit spectra, which most often assume that both kinemati- Hubble sequence for various luminosities, the evolution of galaxies when comparing 2D kinematics of distant galaxies (Flores et al. 2004) with nearby ones, the environmental effects and the inner E-mail: [email protected] kinematics with the help of simulations.
C 2005 RAS 128 O. Garrido et al.
The search for links between the shape of rotation curves (RCs) and physical properties of galaxies has been the subject of many studies. Tully & Fisher (1977) have shown that both luminosity and maximal velocity are tightly linked. Rubin et al. (1985) then showed that in fact the maximal rotational velocity is linked both with the luminosity and the morphological type. Persic, Salucci & Stel (1991) noted that both the shape of the RCs and luminosity are linked, and derived a universal rotation curve (1996) which mainly depends on the luminosity. However, Verheijen (1997) and Sofue et al. (1999) showed that the URC is not able to reproduce systematically the inner and outer parts of their RCs. Galaxies mainly belong to large-scale aggregations (Vettolani, de
Souza & Chincarini 1986) providing environments of different den- Downloaded from https://academic.oup.com/mnras/article/362/1/127/1339746 by guest on 30 September 2021 sity. The environment is responsible for the morphological evolution of galaxies through dynamical modifications (Moore, Lake & Katz 1998; Dubinski 1999) resulting in a morphologicalÐdensity relation (Dressler et al. 1997). But it is possible to find galaxies in low-density Figure 1. Histogram of the 96 GHASP galaxies according to the isolation environments which have not suffered from recent interactions and criterion. which have therefore evolved in a secular way for the last billion years. A great number of studies based on large samples of RCs (e.g. gramme and only a few pairs or groups of galaxies have been ob- Rubin, Waterman & Kenney 1999; Marquez et al. 2002; Dale & served. The degree of isolation of the GHASP galaxies has been Uson 2003; Varela et al. 2004; Vogt et al. 2004a,b,c) concerns the accurately estimated using the logarithmic ratio f between external gravitational effects on the shape of the RCs. But, in order to discrim- and internal forces (equation 1) defined from numerical simulations inate a secular from an external origin for any dynamical peculiar- (Athanassoula 1984): ity, it is necessary to investigate deeply all the possible relationships F R M between kinematical properties and fundamental quantities which f =log external = 3 log + log C (1) F b M characterize isolated and non-isolated galaxies. For this purpose, internal G we have clearly defined in Section 2.1 the degree of interaction for where R is the radius of the galaxy, b the impact parameter, MC the each galaxy, differentiating the isolated galaxies from the galaxies mass of the companion and MG the mass of the galaxy. subjected to faint interactions or strong interactions. The results of simulation works (Varelaet al. 2004, and references In this paper, we mainly discuss the 1D properties extracted therein) show that if, for a given galaxy, f −2 then the galaxy from the 1D derived rotation curves. The 2D information is only has not been affected by gravitational interaction for at least 2 × used to derive kinematically determined position angles of the ma- 109 yr. In this case, the galaxy can be considered as isolated. jor axis and inclinations. Galaxies experiencing strong interactions Varela et al. (2004) have redefined this parameter replacing the have been excluded from this analysis since they are not numerous estimation of the masses by the luminosity, and the impact parameter enough. In forthcoming papers, the impact of the environment (in b by the projected distance between a galaxy and its companion. The alow-density environment) on the kinematical properties of nearby expression for f then becomes galaxies will be investigated together with a detailed analysis of the R velocity fields. f = 3 log + 0.4(m − m ) (2) D G C The goal of this article is to evaluate the kinematical properties p of a sample of 85 galaxies divided into two groups: undisturbed where R is the radius measured along the major axis of the galaxy, and softly interacting. Studying all the links between parameters Dp the projected distance in the plane of the sky between the galaxy reflecting the dynamical state of a galaxy will help us to have a and the companion, and mG and mC, respectively, are the apparent better understanding of the evolution of galaxies. In this paper, we magnitudes of the galaxy and the companion. present a new set of 44 velocity fields providing 43 RCs. Including We computed the f values, from equation (2), for the GHASP the previous papers, the GHASP survey now totals reduced FabryÐ galaxies, using the ALADIN, NED and HyperLEDA data bases. Perot data for 96 galaxies, uniformly covering the ‘magnitude–type’ The values of f are given in Table B1 (see Appendix B). For each plane (Fig. 1). In Section 2, the properties of the sample and the galaxy, the investigation of the companions has been made within analysis of the isolation criterion are described. In Section 3, we a radius of 20 times the diameter of the considered galaxy (which describe the data reduction processing. In Section 4, we analyse the is the criterion used by Karachentseva 1973) and in the range of kinematical properties of the sample. More precisely, we study the ±700 km s−1 around the systemic velocity of the galaxy. variation of the Hα disc extension and the shape of the RCs (in terms The interest in using such a parameter is to provide a degree of of inner and outer slopes and degree of asymmetry of the RCs). In non-isolation for each galaxy since f ranges from −5 for isolated Section 5, a summary is given. Kinematical data are presented with galaxies to ∼1 for pair galaxies or compact group galaxies. Fig. 1 comments for each object in the appendices. gives the number of GHASP galaxies according to bins of f values within the phase space explored (20 diameters and ±700 km s−1). For the galaxies with no companion, we adopted f =−5. Studying 2PROPERTIES OF THE SAMPLE the distribution of the f values for Coma cluster galaxies, Varela et al. (2004) adopted as a criterion for isolated galaxies that f should 2.1 Isolation criterion be less than −4.5. Nevertheless, Varela et al. (2004) were led to The GHASP galaxies have been chosen in low-density environ- use this low value of the cut-off since they did not have additional ments since cluster galaxies have been excluded from this pro- kinematical information. Indeed, from a qualitative analysis of the
C 2005 RAS, MNRAS 362, 127Ð166 GHASP – IV. 44 new velocity fields 129
Hα (GHASP) and H I (WHISP) velocity fields, we found that 51 Table2. Results of the KolmogorovÐSmirnov test comparing the subsample galaxies, with f less than −3.5 (classified as ISO below), present to the total GHASP sample. no kinematical disturbances, neither of the Hα disc nor of the H I disc and furthermore can be considered as isolated or experiencing (0.5Ð2.5) (2.5Ð4.5) (4.5Ð7.5) (7.5Ð10) − − very faint perturbations without major consequences on their kine- ( 22, 20) 0.00 0.26 0.85 matics. Some of the galaxies with −3.5 f −1.5 (classified as (−20,−18) 0.00 0.00 0.00 0.00 − − SOFT below) present perturbations in their morphology or/and in ( 18, 16) 0.00 0.00 the H I kinematics, but their optical velocity field is not affected in Column: bin of morphological type. Row: bin of total B magnitude.The these cases. Therefore, galaxies with −3.5 f −1.5 (34 galax- numbers represent the probability that the subsample is not representative of ies) can been considered as softly interacting galaxies. Most of the the total GHASP sample (values above 0.7 suggest that the corresponding galaxies with −1.5 f suffered from strong interactions (e.g. the class of galaxies is not sufficiently represented). UGC 5931/35 pair) and present Hα (and also H I) disturbances. Albada; http://www.astro.rug.nl/∼whisp). Unfortunately, it is not Then, we excluded the 11 GHASP galaxies with −1.5 f from Downloaded from https://academic.oup.com/mnras/article/362/1/127/1339746 by guest on 30 September 2021 possible to compare the kinematics of neutral and ionized gas since the analysis of this paper since the impact of the environment on most of the WHISP data are not yet published (except for a sample the Hα kinematical properties will be investigated in a forthcoming of dwarf galaxies studied by Swaters & Balcells 2002, and for which paper. the comparison has been made). 2.2 Main properties Fig. 2 summarizes the actual state of the survey: all morphological types from Sa to irregular galaxies have been observed and isolated The GHASP sample aims at covering the ‘luminosity– as softly interacting galaxies (first line). Comparing the distribution morphological type’ plane in the ranges −16 MB −22 and of ISO and SOFT galaxies, we note that only a few very luminous 1 t 10. Bins of 2 in type and 1 in magnitude have been de- or very faint isolated galaxies have been observed (second line). fined in this plane; each bin containing eight galaxies, a total of Fig. 2 (line 3) shows that the 96 GHASP galaxies considered in this around 200 galaxies (4 × 6 × 8) had to be observed to cover the analysis are uniformly distributed in the ‘magnitude–type’ plane: a whole plane. The selection procedure of the GHASP galaxies has majority of barred galaxies has been observed since two-thirds of been made in order to have the whole GHASP data set representa- the galaxies are barred. There is, however, a bias in the two ISO tive of the LEDA sample (where only galaxies corresponding to the and SOFT subsamples since the SOFT sample contains early-type −1 GHASP criteria have been kept: δ 0, V sys 9000 km s ,1t galaxies more luminous than in the ISO sample. Note also that, more 10) as much as possible. The KolmogorovÐSmirnov test in 2D generally, the SOFT galaxies seem to be systematically brighter than was applied to the total GHASP sample considered as a subsample the ISO galaxies, whatever the type. of the LEDA sample. The results (Table 1) are given in terms of the In Fig. 3 the global properties of the sample are studied distin- probability that the GHASP sample could not be representative of guishing isolated and softly interacting galaxies; the colour or the the LEDA sample. This test shows that the total GHASP sample is central surface brightness show the same variations with the lumi- well representative of the LEDA sample except for luminous and nosity or the type in both cases. normal Sc/Scd galaxies. The journal of the observations for the 44 new galaxies (in fact 43 The KolmogorovÐSmirnov test has also been applied to the sub- since UGC 11300 has already been observed with the old camera, sample analysed here. The results given in Table 2 show that the see Paper II) is given in Table 3. GHASP subsample studied here is well representative of the total GHASP sample except for luminous Sc/Sd galaxies. 3 THE DATA The data gathered with the first four observing runs have been published in Garrido et al. (2002, 2003); Garrido, Marcelin & 3.1 The data reduction Amram (2004) (Papers I, II and III). We present here the results The principles and characteristics of the instrument are the same of the fifth, sixth and seventh runs, representing a sample of 44 as for Papers I, II and III but the detector, a new image photon galaxies observed in October 2000 and May and November 2001. counting system (IPCS), is a more efficient one (see Gach et al. 86 of the 96 GHASP galaxies discussed here have been selected 2002) and can achieve a quantum efficiency of 23 per cent due to from the WHISP catalog (a survey carried out at the Westerbork a GaAs photocathode (which is five times more efficient than the interferometer which consists in mapping the distribution of the previous one). As a consequence, the pixel size and the field of view neutral gas for about 400 galaxies, Principal Investigator: T.S. van have been modified: the pixel size is now 0.68 arcsec (however the angular resolution of our data is limited by the seeing, about 3 Table 1. Results of the KolmogorovÐSmirnov test comparing the total arcsec), and the field of view is now 5.8 arcmin2. The data processing GHASP sample to the LEDA sample. and the measurements of the kinematical parameters remain the same (see Garrido et al. 2002). The acquisition of a new set of (0.5Ð2.5) (2.5Ð4.5) (4.5Ð7.5) (7.5Ð10) filters with a FWHM of 2 nm allowed us to observe galaxies with (−22,−21) 0.37 0.49 0.76 recession velocities up to 9000 km s−1. Note that when a galaxy (−21,−20) 0.34 0.00 0.63 0.00 (−20,−19) 0.24 0.00 0.89 0.00 has been observed twice, with different filters, the difference of (−19,−18) 0.00 0.07 0.00 0.07 exposure time through the two filters is mainly due to the difference (−18,−17) 0.09 0.70 0.69 of transmission of the filters or/and in transparency of the sky during (−17,−16) 0.00 the observations.
Column: bin of morphological type. Row: bin of total B magnitude. The 3.2 Description of the figures numbers represent the probability that the total GHASP sample is not representative of the LEDA sample (values above 0.7 suggest that the For each galaxy (see Figs A1ÐA27, B1ÐB16 in appendices), we corresponding class of galaxies is not sufficiently represented). present two frames per figure: isovelocity lines superimposed on
C 2005 RAS, MNRAS 362, 127Ð166 130 O. Garrido et al. Downloaded from https://academic.oup.com/mnras/article/362/1/127/1339746 by guest on 30 September 2021
Figure 2. First line: distribution of morphological types distinguishing ISO (left) and SOFT (right) galaxies. Second line: distribution of magnitudes distin- guishing ISO (left) and SOFT (right) galaxies. Third line: distribution of our sample in the ‘magnitude–type’ plane distinguishing barred from unbarred galaxies (left) and ISO from SOFT galaxies (right). the Hα image of the galaxy (left) and the rotation curve of the the internal motions since the size of the smoothing (3 pixels = 2 galaxy (right) with the model fit superimposed. arcsec) is smaller than the seeing at the OHP (never below 2 arcsec, all the more since we have rather long exposure times). In order to get smooth contours, the isovelocities were drawn after a strong 3.2.1 Velocity field spatial Gaussian smoothing (7 arcsec) of the original velocity field, A colour-coded version of the original velocity field is available sometimes reiterated when the diffuse emission of the disc was too on the Web site of GHASP: http//www.oamp.fr/interferometrie/ faint or when the coverage of the galaxy by H II regions was too poor GHASP/ghasp.html. Before deriving the velocity field, a Gaussian to get continuous lines. The data smoothing is made on the velocity smoothing is first applied on the Hα profiles in order to increase data file itself (not on the complete data cube) with the same weight the signal-to-noise ratio (S/N) in the faint regions. The smoothing for each pixel, so that the final pattern of the isovelocity lines is applied on the data cubes has no incidence on the determination of not too biased by the bright H II regions. In the areas lacking Hα
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Figure 3. Top: distribution of the colour versus MB and morphological type distinguishing isolated and non-isolated galaxies. Bottom: distribution of the central surface brightness versus MB and morphological type with the same distinction. emission, the continuity of the lines has been artificially achieved To obtain the Hα flux inside each pixel, first, the continuum level by eye-estimate and a dashed line plotted to make the reading of the was taken to be the mean of the channels which do not contain the velocity field easier. In cases where only a few isolated H II regions line. The Hα integrated flux map was obtained by integrating the were measured in a galaxy (e.g. UGC 3384, 9992), it was not possi- monochromatic profile in each pixel above the threshold defined by ble to draw any isovelocity line; then we directly wrote the average the continuum level. The scanning of the interferometer samples velocity value found for each H II region on the map. the point spread function (PSF) of the instrument sufficiently(the The FabryÐPerot technique provides an Hα profile inside each Airy function convolved by the surface and transmission defects) pixel, so that a typical velocity field of a GHASP galaxy contains and covers the free spectral range through 24 scanning steps. When thousands of velocity points. For most of the galaxies observed with the profiles are structureless and the S/N high, the lines can be easily GHASP,the velocity field is not limited to the H II regions but covers fitted by the convolution of the observed PSF (given by the narrow most of the diffuse emission of the disc, as can be seen on the original neon 6598.95-nm emission line) with a single Gaussian function. colour-coded velocity fields on the GHASP Web site. The detection When the profile is more complex, multiple Gaussian components limit of our device is 10−9 Jm−2 s−1 sr−2 (Amram et al. 1991), which are needed. Nevertheless, since the number of scanning steps and is 2.4 × 10−17 erg cm−2 s−1 arcsec−2, with a S/N ratio between 1 the baseline of the continuum emission are relatively low, and the and 2 for a 15-min exposure time. As a result, our typical exposure structure of the profile is often complex (asymmetries, multiple com- times of2hensure a good detection of the Hα diffuse emission ponents, low S/N), we do not fit a function to the profile to extract of the disc of most galaxies since most of the Hα emission found the first-order momentum. Instead, the heliocentric radial velocity below 1.6 × 10−16 erg cm−2 s−1 arcsec−2 may be considered as for a given pixel is directly given by the position of the barycentre filamentary and/or diffuse according to Ferguson et al. (1996). This of the line. Furthermore, we do not have to make assumptions on is all the more true with our new IPCS detector (used since October the fit used when the data are dominated by Poisson or receptor 2000) because of its more sensitive GaAs photocathode (Gach et al. noise at low S/N levels. However, at high S/N, since we have a good 2002) offering a five-fold gain in quantum efficiency. knowledge of the PSF, the barycentre of the emission line profile may be measured with an accuracy much better than the sampling step, hence giving a precision of about 3 km s−1 for a S/N = 5. For 3.2.2 Hα line each pixel, the S/N level is given by the y-axis of the barycentre The Hα image is derived from the analysis of the Hα line pro- of the line normalized by the rms of the continuum level. Velocity files, by measuring the flux found inside the line for each pixel. It maps were then obtained from the intensity weighted means of the gives a pure monochromatic image of the galaxy (continuum free). Hα peaks for each pixel.
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Table 3. Log of the observations.
◦ ◦ N N αδλc FWHM Date Exposure time Seeing UGC NGC (2000) (2000) (Å) (Å) (s) (arcsec) (1) (2) (3) (4) (5) (6) (7) (8) (9)
508 266 00h49m47.8s 32◦01 40 6665 23.1 Oct 26, 2000 7200 3.4 6662 21.4 Nov 20, 2001 3960 3 763 428 01h12m55.6s 00◦58 54 6587 11.2 Oct 31, 2000 5760 4.1 1117 598 01h33m50.9s 30◦39 37 6561 8.8 Oct 27, 2000 5760 4 1736 864 02h15m27.7s 06◦00 8.2 6597 10.3 Oct 23, 2000 7560 6.1 1886 02h26m00.5s 06◦00 8.2 6662 21.4 Nov 20, 2001 6480 4 1913 925 02h27m17s 33◦34 43 6576 11.4 Oct 24, 2000 5400 3.4 2045 972 02h34m12.9s 29◦18 47 6596 10.3 Nov 1, 2000 9360 4.8 Downloaded from https://academic.oup.com/mnras/article/362/1/127/1339746 by guest on 30 September 2021 2141 1012 02h39m14.9s 30◦09 06 6585 11.2 Nov 17, 2001 5160 3 2183 1056 02h42m48.4s 28◦34 27 6595 10.3 Oct 27, 2000 7920 4.8 2193 1058 02h43m30s 37◦20 29 6574 11.4 Nov 19, 2001 9360 4 2503 1169 03h03m34.7s 46◦23 11 6615 11.1 Nov 17, 2001 7200 4.4 3013 1530 04h23m27.1s 75◦17 44 6615 11.1 Nov 16, 2001 3840 3.7 3273 05h17m44.4s 53◦33 05 6575 11.4 Nov 9, 2001 5040 5.8 3384 05h59m47.7s 62◦09 29 6634 21.7 Oct 26, 2000 9360 4 3429 2146 06h18m37.7s 78◦21 25 6574 13.6 Nov 17, 2001 6480 3.5 3691 07h08m1.3s 15◦10 42 6611 10.2 Oct 28, 2000 8640 4.4 3734 2344 07h12m28.6s 47◦10 00 6585 11.2 Nov 9, 2001 5280 6.5 4273 2543 08h12m58s 36◦15 16 6615 11.1 Nov 21, 2001 7200 4.4 6702 3840 11h43m59s 20◦04 37 6725 50 May 26, 2001 5280 3.7 9366 5676 14h32m46.8s 49◦27 28 6606 12 May 24, 2001 1680 2.4 6606 12 May 25, 2001 3600 3 9649 5832 14h57m45.7s 71◦40 56 6576 11.4 May 27, 2001 6000 2.4 9753 5879 15h09m46.8s 57◦00 01 6576 11.4 May 23, 2001 3120 3 6586 11.2 2160 2.4 9858 15h26m41.5s 40◦33 52 6621 9.1 May 31, 2001 5280 2.7 9992 15h41m47.8s 67◦15 15 6576 11.4 May 27, 2001 5760 3 10359 6140 16h20m58.1s 65◦23 26 6587 11.2 May 28, 2001 4800 3 10445 16h33m47.6s 28◦59 06 6587 11.2 May 26, 2001 4320 3.4 10470 6217 16h32m39.2s 78◦11 53 6597 10.3 May 25, 2001 7920 3.7 10502 16h37m37.7s 72◦22 29 6650 21.7 May 31, 2001 3360 3.5 10546 6236 16h44m34.6s 70◦46 49 6587 11.2 May 30, 2001 5280 3.4 10564 6248 16h46m22s 70◦21 32 6587 11.2 May 28, 2001 4560 3.4 11124 18h07m26.9s 35◦33 31 6597 10.3 May 28, 2001 3600 3 11300 6689/90 18h34m50.2s 70◦31 26 6576 11.4 May 31, 2001 5040 3 11429 6792 19h20m57.4s 43◦07 57 6663 21.4 May 29, 2001 1920 3 6663 21.4 May 30, 2001 3600 3.4 11557 20h23m58.3s 60◦11 33 6597 10.3 May 29, 2001 4320 2.4 11707 21h14m31.7s 26◦44 04 6582 11.2 Nov 20, 2001 5400 3.7 11852 21h55m59.3s 27◦53 55 6687 23.1 Oct 31, 2000 7920 4.1 11861 21h56m24s 73◦15 39 6595 10.3 Nov 9, 2001 5280 6.1 11909 22h06m16.2s 47◦15 04 6585 11.2 Nov 10, 2001 4080 3 11914 7217 22h07m52.5s 31◦21 33 6587 11.2 Oct 26, 2000 7200 4.8 12101 7320 22h36m3.5s 33◦56 54.2 6587 11.2 Oct 29, 2000 2880 3.4 6576 11.4 2160 3.4 12276 7440 22h58m32.5s 35◦48 09 6683 23.1 Oct 27, 2000 7200 4.8 12276c 22h58m41.3s 35◦48 33.6 6683 23.1 Oct 27, 2000 7200 4.8 12343 7479 23h04m56.6s 12◦19 22 6614 11.1 Nov 12, 2001 5760 5.5 12632 23h29m58.7s 40◦59 25 6571 13.7 Nov 16, 2001 6120 3.7
(1) Name of the galaxy in the UGC catalog. (2) Name in the NGC catalog when available. (3) and (4) Coordinates of the galaxy in 2000. (5) Central wavelength of the interference filter used. (6) FWHM of the interference filter. (7) Date of the observations. (8) Total exposure time in s. (9) Seeing in arcsec (FWHMofa Gaussian fit of foreground stars).
The relative intensity of the Hα map is coded here through grey they are easy to distinguish from normal field stars. It is important levels. The Hα images are sometimes markedly offset with respect to get rid of them in the case of bright H II regions since they will to the centre of the image when we had to shift a bright star out produce a symmetric diffuse patch with the same velocity, as shown of the field to prevent any damage to the microchannel plate of by Georgelin (1970). Hence the interest of offsetting the galaxy in the IPCS as well as to prevent ghosts. Such ghosts are parasitic the field to prevent any parasitic ghost to be superposed on the galaxy reflections of bright objects inside the instrument, between FabryÐ itself. Ghost reflections may also be deflected to the edge of the field Perot plates and the interference filter; those ghosts are out of focus by tilting the etalon with respect to the optical axis, at the price of and symmetrically located with respect to the optical axis, so that adegraded resolution limit at the detector edge (Bland & Tully
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1989). In a few cases, when the velocity amplitude is comparable or higher than the width of the interference filter, the interference filter is not centred on the systemic velocity and one side of the galaxy may be better transmitted than the other side, leading to an artificial asymmetry in the intensity of the Hα emission. This is specified in the cases when it occurs.
3.2.3 Rotation curve The rotation curve is drawn as explained in Paper I, using the ve- locity field obtained after a Gaussian smoothing of 3 arcsec. The set of kinematical parameters is adjusted through an iterative process minimizing the dispersion of the points along the rotation curve. Downloaded from https://academic.oup.com/mnras/article/362/1/127/1339746 by guest on 30 September 2021 The starting set of parameters is chosen as follows. The centre of rotation is supposed to be the nucleus identified on our continuum image (when no nucleus can be seen, neither on our images nor in other bands, it is chosen as the centre of symmetry of our veloc- ity field; four out of the 45 galaxies presented in this new set have a significant offset between the photometric and kinematic centre, and less than 10 out of the 96 GHASP galaxies studied up to now), the inclination is derived from the axis ratio found in the litera- ture, the position angle is defined by the outer parts of our velocity field, and the systemic velocity is adjusted in order to symmetrize at best both sides of the rotation curve. For well-behaved galaxies, the iterative process was quite easy and rapidly converged. However, for some irregular galaxies with asymmetric rotation curves it was hard to converge and we had a strong uncertainty on the kinemat- ical parameters, more especially the inclination which is the less constrained. The typical accuracy we reach is about 1 arcsec for the position of the rotation centre, 2Ð3 km s−1 for the systemic velocity, 2◦ for the position angle of the major axis, but only 5◦Ð10◦ for the inclination. The curve is plotted with both sides superimposed in the same quadrant, using different symbols for the receding (crosses) and approaching (dots) sides (with respect to the centre). The rota- tion curves are sampled with bins of 3Ð6 pixels (∼2Ð4 arcsec). The choice of the width of the bin depends on the distance of the galaxy, the quality of the data, the inner gradient and the extension of the rotation curve. The error bars on our plot give the dispersion of the rotation velocities computed for all the pixels found inside each el- liptical ring defined by the successive bins. Rotation curves for the barred galaxies of our sample have been plotted without corrections for non-circular motions along the bar. For each rotation curve, a fit has been obtained using the analytical function defined by Kravtsov et al. (1998; see section 4). This model of the RCs is included in the plot as a full black line.
3.3 Kinematical parameters 2D velocity fields enables us to find accurately the position angle (PA) of the major axis of galaxies, providing they are regular rotative discs. They may be differences, however, with the photometrical values because of warps or strong spiral arms that could bias the outermost isophotal contours. Figure 4. Top: kinematical position angles obtained for the GHASP sam- In Fig. 4 (top), the kinematical PAs obtained by GHASP are ple versus photometric position angles found in the HyperLEDA data base. Middle: kinematical inclination versus photometric inclination found in the compared with the photometric PAs (found in HyperLEDA). On = NED. Bottom: difference between GHASP and HyperLEDA systemic ve- average, the difference between both position angles is abs( PA) locity versus the scanning wavelength. 15◦ ± 19◦ and can be as large as 75◦.With long-slit spectrographs, the slit position is based on the photometry; the maximum velocity will hence be missed for many galaxies, leading to a systematic In Fig. 4 (middle), kinematical and photometric inclinations underestimating. We found no correlation between the largest PA (HyperLEDA) are also compared. The inclinations found in and the morphological type, neither with the inclination nor with HyperLEDA take into account the thickness of the disc. On average, the degree of interaction. the difference between both inclinations is abs(i) = 9◦ ± 9◦, and
C 2005 RAS, MNRAS 362, 127Ð166 134 O. Garrido et al. does not depend on the morphological type, nor on the degree of The function of Kravstov et al. (1998) is similar to other multipa- interaction. The low inclinations are apparently systematically un- rameter functions used by Rix et al. (1997) or Courteau (1997): rt derestimated by the photometry, whereas the high inclinations are and Vt are the radius and the velocity of the turnover (rt =∞for overestimated. In the cases of edge-on galaxies, the determination solid body rotation curve), g is linked to the inner slope (V (r rt) = g = / b of the type is hard and then the thickness correction (which depends r ) and b to the outer slope [V (r rt) 1 rt ], and a characterizes on the type) can be false. the sharpness of the turnover. This analytical function derives from As emphasized in Paper I, our systemic velocities suffer from a the family profiles of dark haloes and then has a physical origin. In systematic bias, negligible when the recession velocity is close to fact, the term g is directly connected with the inner slope of the dark 1650 km s−1 (then the Hα emission line of the galaxy is coincident halo profile and the goal using this function is to check, at the end with the neon line at 659.895 nm used for the calibration) but in- of this survey, whether our RCs (which are well constrained in the creasing with departure from the calibration wavelength, reaching inner parts) are best fitted with cuspy or core haloes. − − −10 km s 1 for recession velocities around 0 km s 1 and, symmetri- The fits were carried out by minimizing the χ 2 using the MINUIT − − cally, +10 km s 1 for velocities around 3300 km s 1. This is because package, with the simplex search routine (Nelder & Mead 1965). For Downloaded from https://academic.oup.com/mnras/article/362/1/127/1339746 by guest on 30 September 2021 the interferometer does not behave the same for calibration and ob- each fit, we measured the χ 2 and kept only rotation curves for which servation since the coating layers behave differently depending on the probability that the fit is representative of the data is greater than the wavelength. This theoretical trend is clearly found when plotting 50 per cent (comprised in the interval at 3σ ). the velocity difference between GHASP and LEDA as a function The global shape of a rotation curve is defined by an inner in- of the shifted Hα wavelength for each galaxy (Fig. 4, bottom). The creasing slope, a turnover (at rt) and a plateau more or less constant resulting equation is (with a correlation coefficient of 0.7): with a given slope (the outer slope). We have evaluated the inner and outer slopes of the rotation curves and correlated them with fun- V = (−2077 ± 227) + (0.31 ± 0.03)λscan. (3) damental parameters. We have also measured the extension of the ionized hydrogen disc and the asymmetry of our RCs. The galaxies The dispersion is quite large and the phase shift effect due to the larger than our field of view, those observed with a badly centred interferometer is typically of the same order as the dispersion of the filter or affected by a warp on the optical part of the disc (see Table systemic velocities found in HyperLEDA. That is why we decided B1, below) are, of course, excluded from this analysis (five galax- to give our values of systemic velocity without correcting from the ies: UGC 528, 1117, 2855, 4284, 6537) since, in these cases, the phase shift, all the more since we do not use it in our analysis of studied parameters are badly evaluated. Also, the 11 non-isolated the rotation curves for which knowledge of the absolute value of galaxies (UGC 1249, 1256, 2045, 3851, 4499, 5931, 5935, 7278, the velocities is not necessary. Indeed, the relative velocities we 9969, 10310, 12276c), for which f values larger than −1.5 have are looking for inside a given galaxy are almost not biased by the been found (see Section 2.2), are excluded from this analysis. phase shift effect because the wavelength change is not significant between the receding side and approaching side. 4.1 Extension of the Hα discs Table 4 gives the values that we found for the main kinematical parameters, together with some fundamental parameters compiled 4.1.1 Results from the literature. For each galaxy, we measured the outermost point of our Hα rotation curves (Rlast) which corresponds to the maximal extension of the 4ANALYSIS: EXTENSION OF THE Hα DISCS ionized disc since we take into account velocity points in a large AND SHAPE OF OUR ROTATION CURVES sector around the major axis. In Fig. 5, we plot Rlast as a function of −2 R25, the isophotal radius at a surface brightness of 25 mag arcsec In order to classify and analyse each rotation curve, we fitted our data in the B band. These two quantities are linked by a linear relation (giving the rotational velocity averaged inside elliptical annuli) with which shows that, on average, the size of the Hα disc is proportional the following analytical function containing five free parameters to R25. Fig. 5 also shows that isolated galaxies present Hα discs as (Kravtsov et al. 1998) which presents the advantage of fitting every large as softly interacting galaxies. shape of curve: In order not to induce a bias due to the distance, we studied the / g variation of the ratio R last/R 25 as a function of the morphological = (r rt ) . V (r) Vt (g+b)/a (4) type, t (Fig. 6). This ratio has already been studied in a previous + / a 1 (r rt ) paper (Garrido et al. 2004) and we have actualized it taking into account the new galaxies presented here but also distinguishing the Different modellings of RCs are available in the literature: the points according to the nature of the emission (diffuse Hα emission arctan function, the universal rotation curve (URC) and multipa- or H II region). Globally, we note the following. rameter functions. The arctan function has the advantage of having the smallest number of free parameters but it cannot reproduce RCs (i) ISO galaxies present the smallest Hα discs (around 0.6 R25), with a bump at the turnover or RCs with a peculiar shape (Courteau and in these cases the Hα emission has a diffuse origin (by contrast, 1997). The URC (Persic et al. 1991; Persic, Salucci & Stel 1996) the largest discs are reached with H II regions). From Sb to Sdm takes into account the component of the disc and the halo. It is a galaxies, the R last/R 25 ratio varies between 0.6 and 1.6. The presence physical model of RCs but several authors tried to use it without of H II regions beyond R25 means that massive star formation can great success. One-third of the sample of Ursa Major cluster galax- take place at the edge of the optical disc and beyond for isolated ies of Verheijen (1997) cannot be correctly reproduced with the galaxies. URC; Sofue et al. (1999) cannot fit correctly the inner parts of their (ii) SOFT galaxies cover a smaller range of Rlast values, between RCs with the URC; Courteau (1997) has also applied the URC as 0.8 and 1.2 R25,except for ScÐSd types where it reaches higher a model for 131 RCs and found non-satisfying results for 40 RCs. values. In contrast to ISO galaxies, the last points of the detected Therefore, we decided not to use the URC for modelling our RCs. emission are mainly produced by diffuse emission.
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Table 4. Galaxy parameters.
◦ N t Type D25/2 Mb V sys D i PA V max Rlast 1/2 SA annuli UGC (arcsec) (mag) (km s−1) (Mpc) (◦)(◦) (km s−1) (arcsec) (◦) (arcsec) (1) (2) (3) (4) (5) (6) (7) (8) (9) (10) (11) (12) (13)
508 1.5 SB(rs)ab 88.3 −22 4670±3 61.9 45±3 298±1 363 +185 60 3.4 763 8.7 SAB(s)m 108.9 −19.4 1145±2 15.1 50±5 295±2 109 +193.5 50 4.8 1117 6 S(s)cd 1982 −19.3 −191±2 0.9 50±323±361+47.4 50 4.8 1736 5.1 SAB(rs)c 137.1 −20.5 1522±3 71.3 42±1 201±1 179 +116.9 60 3.4 1886 3.6 SAB(rs)bc 70.2 −19.8 4867±2 66.1 60±5 215±5 279 −134.8 50 3.4 1913 7 SAB(s)d 336.6 −20 552±3 20.8 58±5 100±2 −158.2 30 4.8 2045 2 Sab 97.8 −20.4 1529±2 9.1 55±1 145±2 141 −89.5 40 3.4 2141 0.3 SO/a 74.5 −18 961±2 12.9 68±10 18±5 136 −154.9 35 3.4 2183 1 Sa 69.8 −19.6 1542±22162±1 338±2 122 +61.9 40 3.4 Downloaded from https://academic.oup.com/mnras/article/362/1/127/1339746 by guest on 30 September 2021 2193 5.3 S(rs)c 82.1 −18.2 510±1 10.6 21±1 138±357 −88.5 40 3.4 2503 2.6 SAB(r)b 125.6 −21.8 2403±1 31.4 53±5 216±1 284 −169.3 45 3.4 3013 3.1 SB(rs)b 124.2 −21.5 2465±1 33.4 50±18±5 209 −93.2 15 3.4 3273 8.8 Sm 75.4 −17.7 608±2 8.1 55±1 225±183 +96.4 50 2.7 3384 8.8 SB(rs)a 22.9 −14.8 3429 2.3 SB(s)abpec 164.9 −20.6 868 11.7 60±5 135±2 343.8 +167.6 40 3.4 3691 6 Scd 65.5 −20.3 2212 29.1 62±363±3 136.2 −62.9 50 2.7 3734 4 S(rs)c 57 −18.4 978 12.4 25±5 315±3 174.8 −101 45 2.7 4273 3.8 SB(s)b 75.7 −20.7 2475 32.7 56±533±2 193.6 +81.8 40 3.4 6702 1.3 Sa 30.1 −20.7 7420 98.6 43±10 68±6 178 +34.1 50 1.4 9366 4.7 S(rs)bc 114.8 −21.5 2110 28.8 62±10 43±3 238.2 +98.8 50 3.4 9649 3.1 SB(rs)b 95.3 452 5.2 54±645±3 110.8 −122.3 35 3.4 9753 3.6 S(rs)bc 118.6 −19.4 764 10.8 72±4 180±2 144.5 −116.4 30 3.4 9858 4 SABbc 128.6 −20.4 2626 35.8 79±5 252±2 178.7 −164.9 45 3.4 9992 9.8 Im 48.9 48.9 10359 5.6 SB(s)cdpec 146.6 −19.3 913 11.6 44±10 93±5 147.1 −201.9 40 3.4 10445 6 SBc 70.2 −17.5 957 12.5 60±5 280±1 72.4 −105.6 45 3.4 10470 4 SB(rs)bc 92.1 −20.2 1350 18.5 34±10 115±5 144 −96.2 40 3.4 10502 5.3 S(rs)c 66.1 −20.8 4315 57.5 35±5 275±5 313.8 +121.3 55 3.4 10546 6 SAB(s)cd 75.5 −18.3 1267 16.9 65±5 350±2 160 −110.3 45 3.4 10564 6.5 SBd 72.3 −17.4 1130 15.5 60±5 330±5 80.4 −103.3 50 3.4 11124 5.9 SB(s)cd 75.5 −18.6 1609 21.5 30±5 345±5 131 −71.4 45 3.4 11300 6.4 SBcd 118.3 480 6.3 65±3 348±3 103.9 +113.7 45 3.4 11429 3.1 SBc 65.2 −21.9 4718 61.8 60±324±4 187 +69.2 50 3.4 11557 7.8 SAB(s)dm 64.7 −18.5 1385 18.5 37±592±2 58.9 +66.5 50 3.4 11707 7.9 Sdm 75.4 −16.3 900 12 55±10 238±5 91.8 −160.7 30 3.4 11852 1 SBa 32 −20.2 5871 78 58±313±4 201.4 +25.2 40 2.1 11861 7.8 SABdm 79.8 −19.8 1484 19.8 50±733±381 −123 50 3.4 11909 4.5 Spec 74 −18.5 1100 14.7 77±10 0±1 164.2 +113.3 25 3.4 11914 2.5 S(r)ab 109.9 −20.5 947 12.9 35±588±7 262.4 +105.6 60 3.4 12101 6.6 S(s)d 57.3 −18.1 750 10.8 50±10 132±8 135.8 +50.2 40 2.7 12276 1.1 SB(r)a 39.4 −20.6 5688 75.5 38±10 140±3 120.1 −30.4 60 2.7 12276c 5707.5 76.1 35±10 150±5 +8.3 50 0.7 12343 4.4 SB(s)c 124.2 −21.6 2375 31.3 45±10 25±2 239.3 −139.9 60 3.4 12632 8.7 Sm 134 420 5.6 45∗ 210±5 58.1 −160.9 40 3.4
(1) Name in the UGC catalog. (2) Morphological type from the de Vaucouleurs classification (de Vaucouleurs 1979) in the HyperLEDA data base (Lyon-Meudon Extragalactic Data base). (3) Morphological type from the RC3 catalog. (4) Isophotal radius in arcseconds at the limiting surface brightness of 25 B mag arcsec−2, from HyperLEDA (Paturel et al. 1991). (5) Absolute B magnitude from HyperLEDA, corrected from galactic and internal extinction. (6) Systemic velocity deduced from our velocity field. (7) Distance D, deduced from the systemic velocity taken in the NED (and not corrected −1 −1 from the Virgo inflow), assuming H 0 = 75 km s Mpc ,except for UGC 1117 and 1913 for which accurate measurements of the distance were available (Paturel et al. 2002). (8) Inclination deduced from the analysis of our velocity field except for UGC 12632 (adopted values from the literature). (9) Position angle of the major axis deduced from our velocity field. (10) Maximum velocity, V max, derived from the fit of the rotation curve. NB: In Papers I and II it was a rough estimate from our rotation curve and named V max/2. (11) Outermost point reached on the rotation curve. (12) Half sector around the major axis taken into account for computing the rotation curve. (13) Size, in arcsec, adopted for the annuli to derive the rotations curves.
(iii) For irregular galaxies, we note a faint decrease of the max- We excluded the following from this analysis. imum values (around 1.2) reached by the ratio, but ionized gas re- mains present all over the optical disc. Hunter & Elmegreen (2003) (i) UGC 11951, which seems to be a badly classified galaxy. did not find H II complexes beyond R25 in irregular galaxies. Our Indeed, it is classified as Sa; however, it exhibits a solid-body H I data are consistent with their result since the GHASP galaxies hav- rotation curve and its maximal velocity is around 180 km s−1 (Paper ing a R last/R 25 ratio larger than 1.0 exhibit diffuse emission in the III), typical of a later type (Sb/Sc galaxy); indeed, if we plot this outer parts. point with t = 3, then it belongs to the main cloud.
C 2005 RAS, MNRAS 362, 127Ð166 136 O. Garrido et al.
Studying the variation of the mean H I surface density, it ap- pears that it reaches its minimum value for early-type galaxies, then increases up to Sc galaxies and then remains constant (fig. 3d of Roberts & Haynes 1994, fig. 5a of Broeils & Rhee 1997 and fig. 6 of Martin 1998). Finally, early-type galaxies barely have regions of massive star formation beyond R25. Thus, they have minimal sizes of the ionized disc. They also have low values of mean H I surface density sug- gesting that it is not sufficient at the edge of the discs of early-type galaxies for star formation to begin (Kennicutt 1989), whereas, for late-type galaxies, star formation can take place all over the optical disc, up to 1.5 R25. They exhibit the largest ionized discs together
with high H I surface density, consistent with the maximum value Downloaded from https://academic.oup.com/mnras/article/362/1/127/1339746 by guest on 30 September 2021 of the star formation rate observed in these galaxies (James et al. 2004). The thickness of the discs (Ma 2002; Zhao, Peng & Wang 2004) decreases along the Hubble sequence (Sc galaxies are 40 per Figure 5. Extension of the Hα disc, Rlast in kpc, versus R25 in kpc (for cent thinner than Sab galaxies), then Sbc to Sd galaxies have thin a total of 73 galaxies). The line represents a linear fit of all the points for discs, hence low velocity dispersion and high density of neutral gas; which the equation is y = 0.99x + 0.16 (the correlation coefficient is 0.91). they are certainly the most efficient for forming stars in the opti- cal disc and even beyond. Irregular and dwarf galaxies do not have (ii) UGC 12060 and UGC 11707. They exhibit an abnormally significantly more extended ionized discs compared with early-type / high R last R 25 ratio (4.0 and 2.2). We think that the determinations galaxies although their mean H I surface density is higher. Irregu- of R25 are erroneous since the values proposed by HyperLEDA are lar and dwarf galaxies are 2Ð5 times thicker than spirals (Brinks, clearly higher than those deduced from surface brightness profiles Walter & Ott 2002) and present a velocity dispersion of the same (Swaters & Balcells 2002) available in the literature. Even when order as spirals, but their gravitational potential is not sufficient to taking into account these last values, the two galaxies are markedly form massive stars at high rate, particularly in the outer disc. out of the cloud of points. This should be due to the peculiar class of these two galaxies which have low surface brightness and then must be the object of a separate analysis. 4.2 Rotation curves shapes Two parameters which characterize the global shape of a RC are the 4.1.2 Discussion inner and outer slopes of the rotation curves. Both parameters, as well as the degree of asymmetry of the RC, are studied here for the Why do late-type galaxies present larger Hα discs than early-type ISO and SOFT groups. galaxies? Since star formation is directly linked with the reservoir / of neutral gas, we checked if a similar trend existed for R HI R 25. / But when plotting the ratio R HI R 25 as a function of the type for the 4.2.1 The inner slope galaxies of our sample for which we could find values in the litera- ture, no clear trend can be seen. Also, Broeils & Rhee (1997) found In the case of solid-body rotation curves, the slope is defined unam- no special trend with a sample of 108 galaxies, a result confirmed biguously by the ratio by Martin (1998) who studied a sample of 116 galaxies and found V S = last no relation between the H I extent and the morphological type. in Rlast
Figure 6. Extension of the Hα disc, Rlast in units of R25 versus the morphological type t (for a total of 73 galaxies) distinguishing isolated (left) and softly interacting (right) galaxies. The points are coded differently according to the nature of Hα emission providing the outermost velocity point: triangles for diffuse emission, circles for H II regions.
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Figure 7. First line: inner slope versus the morphological type. Second line: inner slope versus the asymmetry of the RCs. Third line: inner slope versus the outer slope. The open square between parentheses corresponds to UGC 11914 which has an inner slope of 526 km s−1 kpc−1, the highest of the sample. where Rlast and V last represent, respectively, the radius and the ve- Barred galaxies exhibit, on average, smaller values of the inner locity of the outermost point of the rotation curve. slope than unbarred galaxies (also with a lower dispersion) for ISO In the other cases, the radius of the turnover of the rotation curve, as well as for the SOFT group: r , which corresponds to the transition zone between the inner in- t = ± crease and the plateau, was deduced from our fit. In order not to Sin/barred/ISO 39 18 contaminate the determination of the inner slope by the transition = ± zone, we take into account only 70 per cent of the inner slope and Sin/unbarred/ISO 135 157 define the inner slope as: Sin/barred/SOFT = 45 ± 37 V (0.7rt ) Sin = . 0.7rt Sin/unbarred/SOFT = 83 ± 99. We plotted it as a function of the morphological type, the asym- metry (see Section 4.2.3 for the definition) and the outer slope of Studying the graphs of Fig. 7, we note the following for ISO the rotation curve (Fig. 7). galaxies.
C 2005 RAS, MNRAS 362, 127Ð166 138 O. Garrido et al.
(i) There is no large variation of the inner slope of the RCs for barred galaxies, and no correlation can be seen with none of the con- 4.2.2 The outer slope sidered parameters (type, kinematical asymmetry and outer slope). Optical RCs are not well suited for determining this parameter since (ii) For unbarred galaxies, the range of variation of the inner we obtain a plateau for a low percentage of galaxies (exactly 27 slope (as well as the average inner slope itself) increases when we galaxies). To measure the outer slope, we considered the formula: consider earlier types. We note an increase of S when considering in V − V (1.3r ) galaxies with bulges. Late-type galaxies never exhibit an inner slope S = last t . out − . above 60 km s−1 kpc−1. Note that we obtain the same graphs when Rlast 1 3rt replacing t by MB. If Sout is: (iii) For unbarred galaxies, the range of variation of the inner (i) less than −2, the RC is decreasing; slope rises for symmetric RCs (see Section 4.2.3; log A −0.75). D (ii) between −2 and +2, the RC marks a plateau; However, galaxies exhibiting a high value of AD have faint values of − − (iii) larger than +2, the RC is increasing. the inner slope (50 km s 1 kpc 1) showing that only less massive Downloaded from https://academic.oup.com/mnras/article/362/1/127/1339746 by guest on 30 September 2021 galaxies are likely to exhibit asymmetric RCs. We plot, in Fig. 9, Sout versus the type and the degree of asymmetry (iv) No correlation appears between the inner and outer slope for (see Section 4.2.3 for the definition) of the RC (note that, for the the ISO group. luminosity, a graph similar to that with the type has been obtained). First of all, no decreasing RC has been found in the SOFT group; For the inner slope of the RCs of SOFT galaxies, we note the decreasing RCs concern only early-type ISO galaxies, but there are following. only two clearly decreasing RCs (one with a large error bar) and it is (i) There is no clear correlation with the type for barred or for hard to tell whether this is significant or not. No correlation can be unbarred. seen with the type or the kinematical asymmetry for the SOFT group. (ii) The tendency to decrease when the kinematical asymmetry For the ISO group, however, the outer slope seems to increase with increases, already observed for the unbarred galaxies of the ISO the type and, more clearly, with the kinematical asymmetry. Also, group, is observed here for both barred and unbarred. no significant difference can be seen between barred and unbarred (iii) The inner and outer slope seem to be correlated, with the galaxies. This is not surprising since bars are expected to have an outer slope increasing when the inner parts rotate faster. effect only in the inner regions. Inner slopes of the RCs have been the object of few studies. In areview paper about RCs, Sofue & Rubin (2001) concluded that: 4.2.3 Kinematical asymmetries ‘inner RCs have greater individuality’. Marquez et al. (2002) found Lopsidedness is a common feature of galaxies and affects both op- the same trend as us for a sample of 111 isolated galaxies (adopting, tical and H I discs of field galaxies. Asymmetry is mainly seen in as a definition of the inner slope, S = V /r where r and V in G G G G morphology (distribution of gas, distribution of light, extension of are, respectively, the radius and the velocity of the inner region of the disc) or dynamics (warps with U-shape, asymmetric velocity solid-body rotation). In fact, the inner velocity gradient seems to be profiles) and reflects the degree of symmetry of the gravitational better correlated with the bulge-to-disc luminosity ratio as shown potential of a galaxy. There are different ways to measure the degree by Marquez & Moles (1999) for 13 galaxies. In Fig. 8, we plot the of asymmetry related to morphology or dynamics: 50 per cent of central surface brightness in the R-band (available in the literature) the H I profiles are not symmetric (Richter & Sancisi 1994; Haynes versus the inner slope of the rotation curve and find a correlation et al. 1998) reflecting non-symmetry in the distribution of the neu- between these two quantities. This result confirms the conclusions tral hydrogen; Conselice (1997) has measured the asymmetry of the of Marquez & Moles (1999) that the inner gradient of rotational light distribution and found that it is strongly correlated with both velocities is strongly correlated with the concentration of light in the morphological type and colour. In this paper, we study lopsided kine- central parts of the galaxies rather than with the total luminosity. matics measuring the degree of asymmetry of our rotation curves. Nishiura et al. (2000) have developed the following formula: 0.5 N 2 1 V (r ) − V (−r ) A = j j N V (r j ) + V (−r j ) j=1 where N represents the number of annuli of the rotation curve, and V (rj) and V (− rj) the velocity in the jth annulus of the approach- ing (receding) side. Dale & Uson (2003) have refined this formula taking into account the dispersion of the velocity points within each annulus: N V (r ) − V (−r ) V (r ) + V (−r ) A = j j 0.5 × j j σ (r )2 − σ (−r )2 σ (r )2 − σ(−r )2 j=1 j j j j
where σ (rj) and σ (−rj) represent the velocity dispersion in the jth annulus of the approaching (receding) side. The parameter AD has been calculated adopting the DaleÐUson formula which is more representative of the asymmetry in the repar- Figure 8. Central surface brightness in the R-band versus the inner slope tition of mass since it frees us from the dispersion of the motion. of the RCs for 18 galaxies (the correlation coefficient of the fit is 0.65). We consider the whole initial rotation curve to compute AD, then
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Figure 9. Top: outer slope versus morphological type. Bottom: outer slope versus asymmetry of the RC defined by Dale & Uson (2003). The numbers between parentheses represent the number of galaxies for each case. take into account kinematical asymmetry both in the inner and outer the fact that the less massive galaxies have a lower disc mass fraction. parts. Indeed, intrinsic asymmetries in discs may exist as a consequence Non-axisymmetric disturbances, such as bars, oval distortions, of torques induced by triaxial haloes. Such a torque is more efficient spiral structures in the disc are observable in two-dimensional ve- in a galaxy with a faint disc and a massive halo than in a galaxy with locity fields but are usually ignored and azimuthally averaged in the a massive disc and a faint halo. rotation curves. These effects may introduce errors in the rotation No clear influence of the presence of a bar on the asymmetry of curves and contribute, for instance, to shallower inner slopes or ro- the RCs has been found. tation curves. On the other hand, intrinsic asymmetries in the disc (i) For isolated galaxies: are observed. These asymmetries are lower values as long as they are minimized during the standard process of symmetrization of the log(AD/BARRED) =−0.80 ± 0.27 (5) rotation curve. In Fig. 10, we have plotted the variation of the loga- rithm of A versus the morphological type, the luminosity, the (B − D log(AD/UNBARRED) =−0.72 ± 0.29. (6) V ) colour and the maximal velocity of the galaxies, distinguishing barred and unbarred galaxies for both isolated and softly interact- (ii) For softly interacting galaxies: ing groups. Correlations appear more or less clearly with the four log(AD/BARRED) =−0.90 ± 0.24 (7) quantities: the most asymmetric RCs are found for late-type galax- ies, fainter and bluer galaxies. Interestingly, Conselice, Bershady & log(A / ) =−0.77 ± 0.19. (8) Jangren (1997, 2000) find similar correlations between the asym- D UNBARRED metry of light distribution (in R and J bands) and the morphological Note that kinematical asymmetry has been measured on the type as well as the colour. We conclude that the asymmetry in light whole Hα disc and then inner and outer asymmetries are aver- distribution is well correlated with the asymmetry in mass distribu- aged. In a forthcoming paper, kinematical asymmetry should be tion deduced from the warm gas kinematics. measured for different aperture radii notably at the ends of the Fig. 10 also shows that the brightest and the most massive galaxies bars. (fast rotators) are less asymmetric than the fainter ones. This result Fig. 10 shows no clear difference in the behaviour of the asym- is consistent with the data extracted from Schoenmakers (1999), metry between ISO and SOFT galaxies except with the type: the presented by Bosma (2004), showing that the scatter in the disc kinematical asymmetry increases almost linearly with the type for elongation and in the disc mass fraction is larger for slow rotators. ISO galaxies whereas it remains constant for early SOFT galaxies This may mean that fast rotators have rounder discs than slower and increases erratically for the late SOFT galaxies. What physi- rotators. In other words, massive galaxies average more efficiently cal process can explain such relations? In the case of optical discs, the mass distribution in the disc than slow rotators. Massive discs, since the correlation with asymmetry and colour is clear, the origin which are dynamically more evolved, are close to an equilibrium is most probably massive star formation linked with local pertur- state, which is not the case for fainter discs. This is consistent with bations affecting both kinematics and light distribution. Mayya &
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Figure 10. First line: kinematical asymmetry versus morphological type for the isolated (left) and the softly interacting galaxies (right). Second line: kinematical asymmetry versus absolute magnitude for the isolated (left) and the softly interacting galaxies (right). Third line: kinematical asymmetry versus colour for the isolated (left) and the softly interacting (right) galaxies. Fourth line: kinematical asymmetry versus maximal rotational velocity for the isolated (left) and the softly interacting (right) galaxies. UGC 11429 (point between parenthesis) does not belong to the main clouds. In this case, the origin of such a huge kinematical asymmetry seems to be due not to galaxyÐgalaxy interaction ( f =−3.5) but to galaxyÐcluster potential interaction (see comments). The reference line at AD =−0.75 is the visual reference for asymmetry (galaxies above are the most asymmetric).
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Romano (2001) found that the asymmetry in light distribution is cluding seven galaxies with inclination less than 30◦ (equation 11). correlated with the star formation. Haynes et al. (1998) found that The resulting equations show that the maximal velocity tends to be 50 per cent of isolated galaxies present asymmetric H I profiles. overestimated when we include low-inclination galaxies: When studying spiral galaxies in clusters, Dale et al. (2001) found =− . − . − . no relationship between the asymmetry of the RCs and the cluster- MB 5 8[log(WMAX) 2 5] 19 8 (10) centric distance. In addition, no difference is seen in the asymmetry of the RCs between early and late types for cluster galaxies (Rubin MB =−6.1[log(WMAX) − 2.5] − 19.8. (11) et al. 1999; Dale et al. 2001) contrary to field galaxies (Conselice et al. 2000). Therefore, the asymmetry in mass distribution of field Then, in the final analysis, low-inclination galaxies have been galaxies seems to be an intrinsic parameter and to have a secular excluded. We confirm that the agreement is good with the relation origin. Of course, interactions are also likely to induce important found by Tully & Pierce (2000), as well for the isolated and for asymmetries but in the cases where interactions dominate dynami- the softly interacting galaxies, although we find a slightly differ- cal evolution, the galaxies do not follow the previous relations and ent slope. On our plot, we used different symbols to distinguish Downloaded from https://academic.oup.com/mnras/article/362/1/127/1339746 by guest on 30 September 2021 present larger asymmetries (Conselice et al. 2000). In addition, the the different shapes of rotation curves: decreasing, flat (plateau), inverse correlation should be found (asymmetry decreasing along increasing, solid-body and undefined (for which we just reach the the Hubble sequence) if asymmetry in field galaxies were due to turnover). We also confirm that there is no significant difference in external perturbations (accretion, interaction, merger, harassment, the behaviour of both types of rotation curves (solid body or not) ram-pressure stripping) since the morphology (and the brightness) thus confirming that our Hα observations enable us to reach the max- depends on the environment in the sense that blue late-type galax- imum of the rotation curve in most cases. We found the following ies are more frequent in an isolated environment (Dressler 1980; relations. Whitmore, Gilmore & Jones 1993; Tanaka et al. 2004; Varela et al. = 2004). (i) For isolated galaxies (correlation coefficient 0.80):
In conclusion, since isolated and softly interacting galaxies follow MB = (−5.6 ± 0.8)[log(WMAX) − 2.5] − (19.6 ± 0.2). the same correlations, Hα kinematical asymmetries are probably = due to inhomogeneous mass distribution linked with massive star (ii) For softly interacting galaxies (correlation coefficient formation regions in both cases. 0.87):
MB = (−6.2 ± 0.7)[log(WMAX) − 2.5] − (19.8 ± 0.2). 4.3 The Tully–Fisher relation The agreement with Tully & Pierce (2000) is not as good for ISO as for SOFT galaxies, probably because of the lack of both massive In Fig. 11, we plot MB as a function of log(W max) (where and small galaxies in the ISO sample. No difference can be noticed W max = 2 V max)inorder to check the consistency of our data with the TullyÐFisher relation determined by Tully & Pierce (2000): concerning the scatter of the TullyÐFisher relation between the ISO and SOFT galaxies.
MB =−7.27[log(WMAX) − 2.5] − 20.11. (9) TullyÐFisher relations for barred and unbarred galaxies are simi- lar; the presence of a bar does not significantly affect the maximum This plot had been analysed in Paper III with 39 galaxies and is rotational velocity at a given luminosity. This result is in complete extended now to 66 objects. First of all, the impact of the low incli- agreement with that of Courteau (2003). nations on the deduction of maximal velocities has been evaluated. Other authors working on optical kinematical data (e.g. Rubin For this purpose, the equation of the TullyÐFisher relation has been et al. 1999; Marquez et al. 2002) also find a smaller slope for the first determined considering the 66 galaxies (equation 10), then ex- TullyÐFisher relation than Tully and Pierce. It seems that optical studies systematically lead to smaller slopes than H I studies, as
Figure 11. TullyÐFisher relation for our isolated and softly interacting samples of galaxies. The solid line represents the TullyÐFisher relation determined by Tully & Pierce (2000) from nearby galaxies. Different symbols distinguish galaxies with different shapes of RCs. The ? symbol refers to RCs for which the turnover is just reached (then the shape of the RCs is unknown).
C 2005 RAS, MNRAS 362, 127Ð166 142 O. Garrido et al. already found by Courteau (1997) from a sample of 304 galaxies. No when we consider bluer, fainter, later-type galaxies showing that explanation has been found by now to understand such a difference slow rotators are not able to homogenize the distribution of mass. between optical and radio studies. Nevertheless, the determination In addition, the lopsidedness of the kinematics is correlated with of the TullyÐFisher relation at optical wavelengths is essential to the asymmetry of the light distribution (both are correlated with study the mass-dependent luminosity evolution of mass galaxies the colour) and seems to be due to local recent massive star for- since at high redshift the TullyÐFisher relation is obtained from mation. As already emphasized by Conselice et al. (2000), the redshifted optical lines emitted by the warm gas (Barden et al. 2003; asymmetryÐcolour or the asymmetryÐtype relations can be used for Boehm et al. 2004). distant galaxies to distinguish disturbed from undisturbed galaxies. No difference was found between isolated and softly interacting galaxies. 5 SUMMARY AND CONCLUSION Our measurements of maximal velocity are in agreement with the TullyÐFisher relation calibrated by Tully & Pierce (2000) show-
We present in this paper a new set of 44 velocity fields (providing 43 ing that the maximal velocity is reached in the optical. The scat- Downloaded from https://academic.oup.com/mnras/article/362/1/127/1339746 by guest on 30 September 2021 rotation curves) which, added to the three previous sets already ob- ter of the points is the same for the isolated and softly inter- tained in the frame of our GHASP survey, enable us to analyse a total acting galaxies, but the slope is smaller for ISO than for SOFT of 96 rotation curves. For each galaxy, the level of the interactions galaxies. has been determined in order to distinguish three cases: isolated The presence of a bar does not seem to affect the outer velocity (ISO), softly (SOFT) and strongly interacting galaxies. Only the 85 slope, neither the degree of asymmetry of the distribution of matter, galaxies belonging to the first two groups have been studied. First nor the maximal velocity determination. However, barred galaxies of all, we have studied the extension of the ionized disc and found exhibit a smaller range of variation of the inner slope of the RCs, that: and no correlation can be seen either with the type, or with the asymmetry, or with the outer slope, whereas, for unbarred, the inner (i) the Hα extension is roughly proportional to R25 (isophotal − slope decreases with increasing type or asymmetry. radius at a surface brightness of 25 B mag arcsec 2) for ISO as well as for SOFT galaxies; (ii) the lowest values of the size of the ionized disc are obtained for ISO galaxies. Warm gas could be present in the outer disc as far ACKNOWLEDGMENTS as 1.5 R in the form of H II regions or diffuse clouds from Sb to 25 The authors wish to thank the anonymous referee who helped im- Sdm types for ISO galaxies, and from Sc to Sdm types for SOFT prove the paper. This work is based on observations collected at the galaxies. Observatoire de Haute-Provence. The authors thank the Groupement In forthcoming papers relative to the environment, we will check de Recherche Galaxies (now Programme National Galaxies) for al- if the strong interactions have an impact on the extension of the Hα location of observing time and the Observatoire de Haute-Provence disc in terms of truncation as emphasized by Koopmann & Kenney team for its technical assistance during the observations. They also (2004) and as can be seen in galaxy clusters. thank O. Boissin for his help during the observing runs and their stu- Studying the shape of the rotation curves, we have found that: dent D. Maresca for his help in computing the f values. This research has made use of the NASA/IPAC Extragalactic Data base (NED) (i) the inner slope of the RCs of barred galaxies does not vary which is operated by the Jet Propulsion Laboratory, California In- significantly for the ISO group; stitute of Technology, under contract with the National Aeronautics (ii) the inner slope of the RCs clearly decreases when the asym- and Space Administration. The authors have also made an extensive metry (or the type) decreases for barred and unbarred galaxies; use of the HyperLEDA data base (http://leda.univ-lyon1.fr) and of (iii) the strength of the inner slope is directly linked with the cen- the ALADIN data base (http://aladin.u-strasbg.fr/aladin.gml). tral concentration of light rather than with the type or the luminosity; (iv) no correlation is found between the outer slope and the mor- phological type, nor the asymmetry for the softly interacting galax- ies, whereas the outer slope seems to increase when considering REFERENCES later-type or asymmetric isolated galaxies; Amram P., Boulesteix J., Georgelin Y. M., Laval A., Le Coarer E., Marcelin (v) no relation seems to exist between the inner and outer slope M., Rosado M., 1991, The Messenger, 64, 44 showing the impossibility of deriving a universal shape for RCs Athanassoula E., 1984, Phys. Rep., 114, 321 (even when the light distribution is known); Barden M., Lehnert M. 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The recent Richter O.-G., Sancisi R., 1994, A&A, 290, L9 CO rotation curve by Corbelli (2003) also shows that there is an −1 Rix H.-W., Guhatakhurka P., Colless M., Ing K., 1997, MNRAS, 285, 779 intermediate plateau around 60 km s between 0.6 kpc and 1 kpc Roberts M. S., Haynes M. P., 1994, ARA&A, 32, 115 (corresponding to the outer part of our Hα rotation curve since Rubin V. C., Graham J., 1987, ApJ, 316, 67 1 kpc is 3.8 arcmin when adopting a distance of 0.9 Mpc for M33) Rubin V.C., Burstein D., Ford W.K., Jr., Thonnard N., 1985, ApJ, 289, 81 before climbing up to 100 km s−1 at 3 kpc where the true plateau
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Figure A1. UGC 1117. Left: GHASP monochromatic image with Hα radial isovelocities superimposed (in km s−1). Right: Hα rotation curve (crosses for receding side and dots for approaching) with the fit superimposed.
Figure A2. UGC 1736. Left: GHASP monochromatic image with Hα radial isovelocities superimposed (in km s−1). Right: Hα rotation curve (crosses for receding side and dots for approaching) with the fit superimposed. begins. Corbelli & Salucci (2000) have drawn the rotation curve out 1530Ð1560 km s−1 located far enough from the major axis. The to 16 kpc (80 arcmin) from H I observations. Their H I curve shows resulting rotation curve is fairly symmetric and has been computed − a turnover around 10 arcmin, then gently rises up to 135 km s 1 at assuming an inclination of 42◦ deduced from the axis ratio. Marquez the very end. et al. (2002), however, find a much lower rotation curve, with a plateau at 105 km s−1, from slit spectrography adopting the same inclination (strangely, their outermost point on the approaching side, at 110 arcsec, is in agreement with our rotation curve, at about UGC 1736 (NGC 864) 170 km s−1). The interference filter used for the observation cuts a large part of the redshifted emission, so that our monochromatic image and velocity field are rapidly cut for the receding side. The resulting cut-off is all the more strong since the northern side is already less extended UGC 1913 (NGC 925) and less rich in H II regions than the southern (approaching) side. This galaxy has a strong bar. It belongs to the same group as Despite this problem, we could draw the rotation curve almost as NGC 891 and IC 239. The southern arm is better defined than the far for the receding side than for the approaching side, thanks to northern one by the H II regions and contains more of them. The the peculiar position of regions with radial velocities in the range velocity field obtained with GHASP confirms the general pattern
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Figure A3. UGC 1913. Left: GHASP monochromatic image with Hα radial isovelocities superimposed (in km s−1). Right: Hα rotation curve (crosses for receding side and dots for approaching) with the fit superimposed.
Figure A4. UGC 2183. Left: GHASP monochromatic image with Hα radial isovelocities superimposed (in km s−1). Right: Hα rotation curve (crosses for receding side and dots for approaching) with the fit superimposed. previously observed by Marcelin, Boulesteix & Courtes (1982) and difference between the approaching and receding side appears to be offers a much better resolution. The rotation curve remains strongly smoothed in H I because of the beam smearing. asymmetric whatever the set of kinematical parameters adopted. The largest discrepancy is found between 110 and 150 arcsec where the spiral arms exhibit completely opposite motions, the northern arm UGC 2183 (NGC 1056) marking a strong minimum in the rotation curve for the receding Our Hα rotation curve is in good agreement with the positionÐ side, while the southern arm displays a maximum for the approach- velocity plot of WHISP, also showing that the approaching side is ing side. The H I observations by WHISP confirm that the velocity more extended in H I. The H I velocity field shows that the disc is field is more disturbed on the redshifted side and shows an exten- warped with a U-shape. sion of the H I emission toward the south-west, with odd velocities. The H I positionÐvelocity plot along the major axis confirms that a plateau is reached at about 3 arcmin with the same amplitude as ob- UGC 2193 (NGC 1058) − served at Hα. Pisano & Wilcots (1998) have obtained an H I rotation The rotation curve reaches a plateau around 60 km s 1 at about 30 curve from VLA observations, with a 400-arcsec extension. Their arcsec. The H I velocity field (Dickey, Murray & Helou 1990) is also curve around 130 arcsec is in agreement with our Hα curve, but the regular and shows that the outermost isovelocity lines are closed.
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Figure A5. UGC 2193. Left: GHASP monochromatic image with Hα radial isovelocities superimposed (in km s−1). Right: Hα rotation curve (crosses for receding side and dots for approaching) with the fit superimposed.
Figure A6. UGC 3013. Left: GHASP monochromatic image with Hα radial isovelocities superimposed (in km s−1). Right: Hα rotation curve (crosses for receding side and dots for approaching) with the fit superimposed.
The maximum of the rotation curve is more typical of an Sd or Sdm smaller inclination (45◦ against 50◦ for GHASP). Adopting their in- type and suggest that this galaxy has been misclassified. clination we find the same Hα rotation curve. Their H I curve peaks at 220 km s−1 around 30 arcsec, then gently decreases down to 195 km s−1. Marquez et al. (2002) obtained the optical rotation curve UGC 3013 (NGC 1530) from slit spectrography, but placed the slit with a position angle of ◦ ◦ − Our velocity field is fairly regular and a strong central gradient can 23 (instead of 8 ) and found a plateau at 160 km s 1 only. The be seen in the bulge itself. Non-circular motions along the bar led us most recent study of this galaxy is that by Zurita et al. (2004) using to take into account only the points close to the major axis (within Taurus II on the William Herschel Telescope (WHT). They find a − − 15◦) when drawing the rotation curve, otherwise it is completely bi- systemic velocity V = 2466 ± 4kms 1 (we find 2465 ± 1kms 1), ◦ ◦ ◦ ased. Indeed, the rotation curve rapidly reaches a plateau, oscillating the same PA of the major axis (8 ) and an inclination of 53 ± 8 ◦ around 200 km s−1 and very slightly decreasing. Regan et al. (1996) but adopted 50 (as we did) for deriving the rotation curve. In spite have made observations at both Hα (also with the FabryÐPerot tech- of the good agreement for the whole set of kinematical parameters, − nique) and 21-cm wavelengths (at Westerbork) and found the same their rotation curve exhibits a higher plateau, about 30 km s 1 above position angle as we found for the major axis (8◦)but concluded a our curve.
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Figure A7. UGC 3273. Left: GHASP monochromatic image with Hα radial isovelocities superimposed (in km s−1). Right: Hα rotation curve (crosses for receding side and dots for approaching) with the fit superimposed.
Figure A8. UGC 3384. Left: GHASP monochromatic image. Right: Hα velocity field with grey-scale for radial velocities.
UGC 3273 ing the rotation curve at best. The inclination was found to be about The velocity field shows that the position angle of the major axis 62◦, close to the value given by the axis ratio (60◦). The difference in changes with radius, suggesting a warp of the disc. No clear nucleus behaviour between the two sides of the galaxy is probably linked to can be seen on our continuum image, so that we adopted the centre the asymmetry already emphasized, the receding side being mostly seen on a red digital sky survey (DSS) image. The curve obtained is composed of diffuse Hα emission (probably more significant of the fairly symmetric up to 50 arcsec, with a solid-body rotation. How- average rotation of the disc) while the approaching side shows a very ever, both sides behave quite differently beyond. bright and strong spiral arm which is likely to induce non-circular motions, thus explaining the odd behaviour. Our rotation curve is in good agreement with that found by Sofue et al. (1998) from Hα UGC 3384 and [N II] emission lines. However, Sofue et al. (1999) find a CO The amplitude in radial velocities is very low and the scatter is rotation curve extended up to 50 arcsec, with an overall shape com- relatively high because of the face-on appearance of the disc. No parable to the Hα curve but velocities about 20 km s−1 higher beyond α satisfactory rotation curve could be derived from our H velocity 35 arcsec. field.
UGC 3691 UGC 3734 (NGC 2344) There is no clear nuclear component, as already emphasized by So- Our Hα velocity field is in very good agreement with the cen- fue et al. (1998) and we determined the rotation centre by symmetriz- tral parts of the H I velocity field found by WHISP. The axis
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Figure A9. UGC 3691. Left: GHASP monochromatic image with Hα isovelocities superimposed (in km s−1). Right: Hα rotation curve (crosses for receding side and dots for approaching) with the fit superimposed.
Figure A10. UGC 3734. Left: GHASP monochromatic image with Hα isovelocities superimposed (in km s−1). Right: Hα rotation curve (crosses for receding side and dots for approaching) with the fit superimposed.
ratio suggests that this galaxy is seen perfectly face-on, which WHISP shows the same radial velocity range as we observe at Hα is clearly not the case from the amplitude of the radial veloc- wavelength. ities across its disc. We adopted 25◦ for the inclination, pro- viding a fairly symmetric rotation curve, although others prefer smaller values (12◦ for WHISP). Our curve reaches a plateau around 175 km s−1 beyond 1 arcmin, quite typical of this type of UGC 9753 (NGC 5879) galaxy. The rotation curve is fairly symmetric, reaching a plateau at 150 km s−1 as soon as 20 arcsec. Fillmore, Boroson & Dressler (1986) have traced an optical rotation curve from slit spectroscopy but their curve remains systematically below ours by about 20 km s−1, which could UGC 9649 (NGC 5832) be due to a different positioning of their slit or the choice of a higher No nucleus can be seen on our continuum image and we adopted the inclination (none of these parameters is given in their paper). The centre seen on a DSS image for deriving the rotation curve, which H I velocity field observed by WHISP is quite odd, showing a large is found to be of solid-body type. The H I velocity field observed by extension of the H I emission toward the east, beyond the optical
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Figure A11. UGC 9649. Left: GHASP monochromatic image with Hα isovelocities superimposed (in km s−1). Right: Hα rotation curve (crosses for receding side and dots for approaching) with the fit superimposed.
Figure A12. UGC 9753. Left: GHASP monochromatic image with Hα isovelocities superimposed (in km s−1). Right: Hα rotation curve (crosses for receding side and dots for approaching) with the fit superimposed. disc. Furthermore, the orientation of the minor axis is completely s−1, and we could not derive any satisfactory rotation curve from our changed there, as well as the overall shape of the isovelocity lines. Hα data. Nevertheless, Swaters (1999) could derive a rotation curve from the WHISP data, with a maximum rotation velocity of 35 km s−1. Mac Gaugh, Rubin & de Block (2001), using slit spectroscopy, UGC 9858 could plot the line-of-sight heliocentric velocity measured along −1 The Hα emission of this galaxy is rather faint as is the S/N ratio the slit, finding a total amplitude of about 30 km s ,but could not of our data, so that we have a rather chaotic rotation curve with derive any rotation curve. large error bars, despite the broad velocity range. Our curve is quite asymmetric beyond 50 arcsec. The H I velocity field observed by WHISP is much more regular, except for a slight warp toward the UGC 10445 −1 east. The H I radial velocity range is about 100 km s higher than The isovelocity lines crossing the strong northern spiral arm show α the amplitude observed at H wavelength. the classical distortions produced by the density wave. The rotation velocity is rather low for an Sc-type galaxy, suggesting that its mor- UGC 9992 phological type could be later than that found in the literature. The No clear velocity gradient can be seen on our velocity field, or in the H I velocity field observed by WHISP shows that the position angle H I WHISP data where the velocity range does not exceed 30 km of the major axis is changing with the radius, suggesting a warp of
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Figure A13. UGC 9858. Left: GHASP monochromatic image with Hα isovelocities superimposed (in km s−1). Right: Hα rotation curve (crosses for receding side and dots for approaching) with the fit superimposed.
UGC 10546 (NGC 6236) Both sides of our rotation curve behave quite differently. The ap- proaching side roughly rotates as a solid body whereas the receding side is much more chaotic. The outermost velocity points on that side should not be taken into account, however, since they are pro- duced by an H II complex lying to the south-east of UGC 10546 which seems to be actually a dwarf galaxy. Indeed, this object has its own velocity field with a marked gradient (that can be seen on the colour-coded velocity field on the Web site of GHASP), suggesting that it is self-gravitating.
UGC 11300 (NGC 6689/90) This SBcd galaxy has been observed twice in the frame of our sur- vey, once with the old photon counting camera and then with the new one. The data obtained with the first camera have been published in Paper II. The second data set enables us to trace the rotation curve further out, at least for the receding side (now reaching 110 arcsec against 90 arcsec previously), owing to the higher sensitivity of the new camera that enabled us to detect faint H II regions to the south. Figure A14. UGC 9992. Left: GHASP monochromatic image with mean The error bars are smaller and the rotation curve is not so asym- α H radial velocities indicated. No rotation curve could be derived. metric as in Paper II, although we confirm that both sides behave differently. The gain is especially remarkable for the outer parts of the disc, but the Hα emission is not sufficiently extended to check the galaxy, where we detect faint H II regions, as well as for the that on our data. diffuse emission in the centre. The kinematical parameters remain the same, within the error bars. The resulting rotation curve sug- gests that the maximum is actually reached. As already mentioned in Paper II, this is confirmed by the H I data from WHISP. UGC 10470 (NGC 6217) The isovelocity lines exhibit wiggles when crossing the spiral arms but also in the centre where S-shaped distortions betray the presence of a bar. Indeed, Martin and Friedli (1997) find that this galaxy has a UGC 11557 ◦ rather strong bar. The signature of the bar cannot be seen on the H I The position angle of the major axis changes from 92 in the centre velocity field (WHISP; van Driel & Buta, 1991), probably because up to 105◦ on the edge of the optical disc. We adopted the first value of the lack of spatial resolution. Our Hα rotation curve is in good (perpendicular to the minor axis) for deriving our rotation curve. agreement (although less extended) with their H I curve when we The H I velocity field obtained by WHISP confirms this behaviour ◦ adopt the same inclination (29 ). Our data led us to adopt a slightly of the major axis. Swaters (1999) has derived the H I rotation higher inclination (34◦), providing a fairly symmetric rotation curve. curve from the WHISP data. When adopting the same kinematical
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Figure A15. UGC 10445. Left: GHASP monochromatic image with Hα isovelocities superimposed (in km s−1). Right: Hα rotation curve (crosses for receding side and dots for approaching) with the fit superimposed.
Figure A16. UGC 10470. Left: GHASP monochromatic image with Hα isovelocities superimposed (in km s−1). Right: Hα rotation curve (crosses for receding side and dots for approaching) with the fit superimposed.
parameters we find an Hα rotation curve in perfect agreement with and with the central part of the H I curve when adopting the same his H I curve. kinematical parameters.
UGC 11707 UGC 11852 On our Hα rotation curve, the receding side does not extend be- There is a lack of Hα emission in the central part for the approaching yond 100 arcsec whereas the approaching side extends out to 160 side and the signature of the bar is not evident on our velocity − arcmin where it reaches 100 km s 1. The H I rotation curve de- field. Our rotation curve is consistent with the positionÐvelocity − rived by Swaters (1999) from the WHISP data reaches 95 km s 1 at plot found by WHISP in H I, suggesting that a maximum is rapidly − 100 arcsec, then slowly increases up to 100 km s 1 at 200 arcsec. reached and followed by a plateau slightly below. Also, the H I The inclination adopted by WHISP is 68◦ whereas our Hα velocity velocity field suggests that the disc is warped, which can be guessed field suggests a fainter inclination of 55◦.Swaters et al. (2003a) have at from the shape of our outermost isovelocity lines. Because of obtained an Hα rotation curve from slit spectrography and derived the relatively high inclination of the galaxy, we took into account a rotation curve mainly traced with the receding side and limited only the points lying within 40◦ from the major axis (otherwise the to 40 arcsec. Our Hα curve is in good agreement with their data dispersion increases rapidly).
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Figure A17. UGC 10546. Left: GHASP monochromatic image with Hα isovelocities superimposed (in km s−1). Right: Hα rotation curve (crosses for receding side and dots for approaching) with the fit superimposed.
Figure A18. UGC 11300. Left: GHASP monochromatic image with Hα isovelocities superimposed (in km s−1). Right: Hα rotation curve (crosses for receding side and dots for approaching) with the fit superimposed.
UGC 11861 If we adopt his position angle, then the discrepancy between both The isovelocity lines in the centre do not show any clear signature rotation curves is worse. It seems that warm and cold gas behave of the bar, probably because it is seen aligned along the minor axis. differently. The resulting rotation curve is fairly symmetric and gently rising up to a final plateau around 165 km s−1 reached at some 100 arcsec. However, we have no information beyond 80 arcsec for the receding side. The maximum of the rotation curve is closer to the value ex- UGC 11909 pected for an Sc-type galaxy than a Magellanic one; furthermore the H II regions are aligned along a bar-like structure in the centre of spiral structure is clearly seen on DSS optical images, suggesting this galaxy, classified as peculiar. Indeed, the isovelocity lines of our that its classification as an Sdm galaxy is exaggerated and should be Hα velocity field show the classical S-shape distortions observed corrected into an Sc type. Marchesini et al. (2002) have derived an across the bars. This bar appears off-centred by about 12 arcsec to optical rotation curve in agreement with ours whereas their position the north with respect to the bulge seen on the continuum image (as ◦ ◦ angle is 28 instead of 33 . The H I rotation curve derived by Swaters well as on DSS or 2MASS images). The dynamical centre deduced (1999) is, on average, 10Ð20 km s−1 below our Hα rotation curve. from our velocity field corresponds to the centre of the bar and not
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Figure A19. UGC 11557. Left: GHASP monochromatic image with Hα isovelocities superimposed (in km s−1). Right: Hα rotation curve (crosses for receding side and dots for approaching) with the fit superimposed.
Figure A20. UGC 11707. Left: GHASP monochromatic image with Hα isovelocities superimposed (in km s−1). Right: Hα rotation curve (crosses for receding side and dots for approaching) with the fit superimposed.
to the bulge (otherwise the rotation curve appears asymmetric and The inner gradient, 526 km s−1 kpc−1,isthe strongest of the strongly perturbed). The position angle of the major axis changes sample of galaxies studied in this paper. Marquez et al. (2002) with the radius on the southern side, suggesting a warp of the disc. have obtained an Hα curve with a lower plateau (around 150 We adopted the position of the major axis symmetrizing at best km s−1) because they have adopted a markedly higher inclination the rotation curve (it corresponds to the axis of symmetry of the (46◦ instead of 35◦ for GHASP). Furthermore, their position an- isovelocity lines for the approaching side). The asymmetry in the gle of the major axis is 12◦ higher than ours. Conversely, Verdes- outer parts of the curve (beyond 1 arcmin) is likely to be explained Montenegro, Bosma & Athanassoula (1995) have obtained an H I by the warp of the disc. rotation curve with a higher plateau (around 300 km s−1) because they adopted a lower inclination (28◦ instead of 35◦ for GHASP). The H I data of WHISP are no more extended than our Hα data UGC 11914 (NGC 7217) (2 arcmin in radius) and the positionÐvelocity plot along the ma- Although we miss the departure of the rotation curve, because of jor axis is in good agreement with our rotation curve, showing a − an Hα hole in the centre, we see that it is rapidly climbing up plateau at the same level (∼250 km s 1) when adopting the same ◦ to a plateau at about 250 km s−1 and almost reaches 110 arcsec. inclination (35 ).
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Figure A21. UGC 11852. Left: GHASP monochromatic image with Hα isovelocities superimposed (in km s−1). Right: Hα rotation curve (crosses for receding side and dots for approaching) with the fit superimposed.
Figure A22. UGC 11861. Left: GHASP monochromatic image with Hα isovelocities superimposed (in km s−1). Right: Hα rotation curve (crosses for receding side and dots for approaching) with the fit superimposed.
the axis ratio suggests an inclination around 60◦ we adopted a value UGC 12101 (NGC 7320) of 50◦ to make the comparison easier with Williams, Yun & Verdes- ◦ This spiral galaxy is in the foreground of the famous Stephan’s Montenegro (2002) who found 48 from H I observations at the quintet. We observed it with bad weather, so that the Hα emission VLA. Our Hα rotation curve is significantly higher than their H I − of the disc was detected with a rather low signal-to-noise ratio, ex- curve (peaking at 99 km s 1 at 60 arcsec), although they have simi- ◦ cept for one bright H II complex found to the north (on the minor lar kinematical parameters (position angle of the major axis at 129 ◦ ◦ ◦ axis) and two bright H II complexes to the north-west (on the ma- instead of 132 and inclination of 48 instead of 50 ). The dis- jor axis). No nucleus can be seen on our continuum image and the crepancy between our Hα curve and the H I curve can be partly rotation centre was determined from images found in the literature, explained by the choice of their rotation centre (significantly off- showing the location of the central bulge. The rotation curve de- set with ours by about 7 arcsec to the west) but the main cause rived from our velocity field, taking into account the points lying is probably a beam-smearing effect, explaining why, in any case, within 40◦ from the major axis, is twice as extended for the reced- our optical curve reaches more rapidly rotation velocities around −1 ing side (mainly because of the outermost H II complexes on the 100 km s .Asfor the outer part of our curve (beyond 30 arcsec) − north-west side but also because the approaching side is severely which exhibits velocities significantly higher than 100 km s 1,we polluted by the bright OH night-sky-line at 657.7 nm). Although think that it is due to anomalous velocities of the outermost H II
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Figure A23. UGC 11909. Left: GHASP monochromatic image with Hα isovelocities superimposed (in km s−1). Right: Hα rotation curve (crosses for receding side and dots for approaching) with the fit superimposed.
Figure A24. UGC 11914. Left: GHASP monochromatic image with Hα isovelocities superimposed (in km s−1). Right: Hα rotation curve (crosses for receding side and dots for approaching) with the fit superimposed. complexes to the north-west, since this part of the curve is only who give radial velocities observed along five different positions of traced by these regions. a slit; however they do not go as far out as we go because of their rather short slit. Marquez et al. (2002) find a rotation curve from slit spectroscopy with a plateau significantly lower than ours (they find UGC 12343 (NGC 7479) − 160 km s 1) because their slit was misplaced (with a position angle The shape of the isovelocity lines shows that the central parts of 45◦ instead of 25◦). of the disc are dominated by non-circular motions, probably due to the strong bar. As a consequence, the position angle of the ma- jor axis changes with the radius and we finally adopted the value UGC 12632 symmetrizing at best the rotation curve (25◦) which is close to the photometrically derived PA (25◦ in RC3 and 29◦ in LEDA). Duval The amplitude observed in radial velocity is rather faint: 60 km & Monnet (1985) have obtained a rotation curve from slit spec- s−1 only. No nucleus can be seen on our continuum image and we trography with the slit positioned at 15◦. Our velocity field leads used R-band images (from the XDSS and from Swaters & Balcells to a curve in good agreement with theirs when adopting the same 2002) to find its position. Our Hα rotation curve is quite chaotic, position angle for the major axis. The agreement is good also with especially for the approaching side. In order to limit the dispersion, the Hα velocities found by Wilke, Mollenhoo & Matthias (2000) we only took into account the points found within 35◦ from the
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Figure A25. UGC 12101. Left: GHASP monochromatic image with Hα isovelocities superimposed (in km s−1). Right: Hα rotation curve (crosses for receding side and dots for approaching) with the fit superimposed.
Figure A26. UGC 12343. Left: GHASP monochromatic image with Hα isovelocities superimposed (in km s−1). Right: Hα rotation curve (crosses for receding side and dots for approaching) with the fit superimposed.
Figure A27. UGC 12632. Left: GHASP monochromatic image with Hα isovelocities superimposed (in km s−1). Right: Hα rotation curve (crosses for receding side and dots for approaching) with the fit superimposed.
C 2005 RAS, MNRAS 362, 127Ð166 GHASP – IV. 44 new velocity fields 157 major axis. We adopted the same inclination as WHISP since it is 15◦, which would lead to an incredible rotation velocity around hard to derive it from our data. Despite the large dispersion of the 800 km s−1.However, the isophotes of the red plate of the XDSS individual points it is clear that our curve is below the H I rotation survey (Second-generation Digital Sky Survey) found on the CADC curve (Swaters 1999; Stil & Israel 2002), increases rapidly up to server clearly suggest a larger inclination, most probably between 60 km s−1 at 90 arcsec, then goes on increasing slowly up to about 40◦ and 45◦.Wefinally adopted an inclination of 45◦ for this galaxy, 80 km s−1. whereas the value adopted by WHISP is only 12◦.Nevertheless, their H I positionÐvelocity plot along the major axis is in good agreement − APPENDIX B: SOFTLY INTERACTING with our Hα data since it shows that a plateau above 200 km s 1 − GALAXIES in radial velocity is rapidly reached, which is about 300 km s 1 in terms of rotation velocity when assuming an inclination of 45◦. Table B1, which contains all the kinematical parameters measured for this work, is located at the end of this appendix.
UGC 763 (NGC 278) Downloaded from https://academic.oup.com/mnras/article/362/1/127/1339746 by guest on 30 September 2021 UGC 508 (NGC 266) The velocity field in the central part shows distortions of the isove- This barred early-type galaxy exhibits a strong velocity gradient locity lines looking like the signature of a bar. Indeed, it is most and we had to use two different interference filters. The values of often classified as barred although no bar can be clearly seen, even the axis ratio found in the literature suggest an inclination around on IR surveys, such as 2MASS, just showing a sort of elongated
Figure B1. UGC 508. Left: GHASP monochromatic image with Hα radial isovelocities superimposed (in km s−1). Right: Hα rotation curve (crosses for receding side and dots for approaching) with the fit superimposed.
Figure B2. UGC 763. Left: GHASP monochromatic image with Hα radial isovelocities superimposed (in km s−1). Right: Hα rotation curve (crosses for receding side and dots for approaching) with the fit superimposed.
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Figure B3. UGC 2045. Left: GHASP monochromatic image with Hα radial isovelocities superimposed (in km s−1). Right: Hα rotation curve (crosses for receding side and dots for approaching) with the fit superimposed.
Figure B4. UGC 2141. Left: GHASP monochromatic image with Hα radial isovelocities superimposed (in km s−1). Right: Hα rotation curve (crosses for receding side and dots for approaching) with the fit superimposed. bulge. No clear nucleus could be found on our data and the rota- centre, characteristic of the kinematical signature of a bar. Indeed, an tion centre was found by symmetrizing the rotation curve at best, elongated central structure can be seen on the 2MASS images, with so that the dynamical centre appears slightly offset (about 5 arcsec) a southÐnorth orientation. On a larger scale, a clear warp of the disc with respect to the centre of the central bulge determined from a can be seen on the velocity field pattern, with a position angle of the red XDSS image. Our velocity field is in good agreement with the major axis changing from 145◦ in the centre to 155◦ in the outer parts H I velocity field observed by Smoker, Davis & Axon (1996). They of the optical disc. UGC 2045 is surrounded by dwarf spheroidal ◦ give a rotation curve combining their H I data with optical data from galaxies likely to explain the warp. We adopted the value 145 to a slit spectrum obtained with ISIS on the William Herschel Tele- draw the rotation curve, with an inclination of 59◦ as suggested scope (WHT). Their Hα data are in good agreement with ours when by the axis ratio. The rotation curve is fairly symmetric, but the adopting the same kinematical parameters. best result for superposing both sides, receding and approaching, was obtained when choosing a rotation centre slightly offset with respect to the nucleus (about 1.5 arcsec toward the south-west). Our UGC 2045 (NGC 972) Hα velocity field is in good agreement with the H I velocity field This galaxy, classified up to now as a normal spiral, is a barred obtained by WHISP within the optical limits. However, the H I field galaxy. Our Hα velocity field shows S-shaped distortions in the appears quite disturbed beyond these limits.
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Figure B5. UGC 2503. Left: GHASP monochromatic image with Hα radial isovelocities superimposed (in km s−1). Right: Hα rotation curve (crosses for receding side and dots for approaching) with the fit superimposed.
Figure B6. UGC 3429. Left: GHASP monochromatic image with Hα radial isovelocities superimposed (in km s−1). Right: Hα rotation curve (crosses for receding side and dots for approaching) with the fit superimposed.
UGC 2141 (NGC 1012) the central part. The H I velocity field shows purely circular mo- The Hα velocity field is quite regular and the rotation curve is of tions and a flat rotation curve, with a plateau at 265 km s−1.Even solid-body type. The H I velocity field provided by WHISP shows the when adopting the same inclination and position of the major axis same radial velocity amplitude as in Hα and the positionÐvelocity as van Driel et al., our plateau remains significantly higher; further- diagram shows that the whole H I disc is rotating as a solid body. more, our Hα rotation curve then becomes markedly asymmetric. However, the outer parts of the H I velocity field suggest a warp of This suggests that both hydrogen components (neutral and ionized) the disc beyond the optical limit. behave differently.
UGC 2503 (NGC 1169) UGC 3429 (NGC 2146) There is no Hα emission in the central parts (within 20 arcsec from The distribution of the ionized gas is markedly asymmetric in this the centre) so that we miss the rising part of the rotation curve SBab galaxy. The Hα emission is very bright in the central bulge, which rapidly reaches a plateau with velocities higher than 250 km along the bar and in the middle of a spiral arm to the north. Faint − s 1. Observations made at Westerbork (van Driel & van Woerden H II regions are scattered along a spiral arm to the south-west. The 1994) show that the neutral gas distribution also exhibits a hole in diffuse emission that can be seen to the south-east of the bar on
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Figure B7. UGC 4273. Left: GHASP monochromatic image with Hα isovelocities superimposed (in km s−1). Right: Hα rotation curve (crosses for receding side and dots for approaching) with the fit superimposed.
Figure B8. UGC 6702. Left: GHASP monochromatic image with Hα isovelocities superimposed (in km s−1). Right: Hα rotation curve (crosses for receding side and dots for approaching) with the fit superimposed. our monochromatic image is due to out-of-focus ghost images of Wallin et al. (1992), they conclude that UGC 3429 collided with a bright H II regions located on the opposite side of the bar. The fainter gas-rich galaxy which has been destroyed during the merging velocity field in the central part is fairly regular, however the ra- process. Anyway it is clear that the central part of the galaxy does dial velocities observed in the arms are much higher than expected not seem to be perturbed, while the spiral arms around it do not take from the extrapolation of the inner velocity lines (more than 100 km part in the rotation of the disc. s−1) suggesting that the spiral arms are probably out of the plane of the central disc. This is in agreement with the study of the kinemat- ics of the ionized gas by Young et al. (1988). Forgetting the spiral UGC 4273 (NGC 2543) arms we could draw a fairly symmetric rotation curve, reaching a The velocity field is fairly regular and the isovelocity lines are dis- plateau around 350 km s−1 at about 80 arcsec. X ray observations torted in the centre, because of the bar. We drew the rotation curve by Della Ceca et al. (1999) reveal that it is a starburst galaxy with by taking into account the points within 40◦ from the major axis an outflow of gas along the minor axis. The H I map obtained by (considering points any further would bias the rotation curve be- Taramopoulos, Payne & Briggs (2001) with the VLA shows an ex- cause of non-circular motions along the bar). The resulting curve − tended H I distribution with two tails (toward the north and toward is fairly symmetric and reaches a plateau around 200 km s 1 at the south) looking like tidal tails. From numerical simulations by 40 arcsec. The receding and approaching sides follow the same
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Figure B9. UGC 9366. Left: GHASP monochromatic image with Hα isovelocities superimposed (in km s−1). Right: Hα rotation curve (crosses for receding side and dots for approaching) with the fit superimposed.
Figure B10. UGC 10359. Left: GHASP monochromatic image with Hα radial isovelocities superimposed (in km s−1). Right: Hα rotation curve (crosses for receding side and dots for approaching) with the fit superimposed. wavesonthe plateau, showing that the spiral arms motions are per- UGC 6702 (NGC 3840) − fectly symmetric. The H I observations, by WHISP, show that the The rotation curve rapidly reaches a plateau around 180 km s 1,at6 H I disc is three times more extended than our Hα emission, with arcsec. Both sides behave symmetrically up to about 20 arcsec, then avery regular velocity field (however, there are some H I clouds they are clearly separated, with the approaching side systematically to the south with a peculiar motion). Marquez et al. (2002) have 30 km s−1 above the receding one. Such behaviour is probably due observed this galaxy with a slit spectrograph and find here again to non-circular motions of the arms (or motions out of the plane of alower plateau (around 160 km s−1). When adopting their kine- the central disc). Let us note also that the rotation velocity is rather matical parameters and simulating a slit at a position angle of 45◦ low for this type of galaxy, generally expected around 300 km s−1. (which is the photometric value) on our data we find the same result; however the resulting curve rapidly becomes chaotic when we take into account the points far from the adopted major axis. The best UGC 9366 (NGC 5676) RC is obtained with a position angle of 33◦, which is 12◦ smaller The central wavelength of our interference filter was slightly shifted than the photometric position angle, underlining the problem of slit with respect to the redshifted Hα line of the galaxy, so that its re- spectroscopy, where the slit is placed a priori along the photometric ceding side was almost cut off by our filter. As a result the southern position angle, whereas with a FabryÐPerot the kinematical position side appears washed out on our monochromatic image. Despite this angle is deduced a posteriori from the analysis of the 2D velocity problem, our velocity field is fairly regular and symmetric (like field. the H I velocity field observed by WHISP). The accuracy of the
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Figure B11. UGC 10502. Left: GHASP monochromatic image with Hα isovelocities superimposed (in km s−1). Right: Hα rotation curve (crosses for receding side and dots for approaching) with the fit superimposed.
Figure B12. UGC 10564. Left: GHASP monochromatic image with Hα isovelocities superimposed (in km s−1). Right: Hα rotation curve (crosses for receding side and dots for approaching) with the fit superimposed. velocities measured on the southern side of the galaxy is good arcsec for the approaching side, because of the spiral structure being enough and our rotation curve has the same extension on both the much more extended on that side. The H I velocity field obtained receding and approaching side and looks fairly symmetric, reaching by WHISP is very regular, with a slight warp of the disc toward the − a plateau around 240 km s 1 at 30 arcsec. Rubin & Graham (1987) west. The H I positionÐvelocity plot along the major axis is in good have derived an optical rotation curve which is in good agreement agreement with our Hα rotation curve. with ours although they adopted a major axis with a slightly different ◦ position angle (5 of difference). UGC 10502 The inclination deduced from the axis ratio (24◦, the value also UGC 10359 (NGC 6140) adopted by WHISP) leads to a rotation velocity higher than 300 km s−1 for the plateau, which is clearly too high for this type of galaxy. Our isovelocity lines show wiggles when crossing the northern spi- ◦ ral arm, suggesting a strong density wave inducing non-circular We finally adopted 35 for the inclination, a value giving the least motions (the same wiggles can be seen on the H I velocity field ob- dispersion for the points of our rotation curve. served by WHISP). No clear nucleus can be found on our continuum image, so that we adopted the centre found on DSS images to de- UGC 10564 (NGC 6248) rive the rotation curve. The curve cannot be traced further out than Although this galaxy is classified as barred, no clear signature of 120 arcsec for the receding side whereas it can be traced out to 200 a bar can be seen on our velocity field. The rotation curve has, on
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Figure B13. UGC 11124. Left: GHASP monochromatic image with Hα isovelocities superimposed (in km s−1). Right: Hα rotation curve (crosses for receding side and dots for approaching) with the fit superimposed.
Figure B14. UGC 11429. Left: GHASP monochromatic image with Hα isovelocities superimposed (in km s−1). Right: Hα rotation curve (crosses for receding side and dots for approaching) with the fit superimposed. average, a solid-body behaviour. However, both sides behave quite the major axis in the outer part of the disc, toward the north. This differently, oscillating around the average curve with, most often, change is clearly visible on the H I velocity field observed by WHISP, opposite tendencies. The H I velocity field observed by WHISP is suggesting that the disc is warped. This warp can hardly be explained fairly regular and shows the same amplitude as our Hα velocity by an interaction with another galaxy, since the closest companion, field (∼150 km s−1). However it is much more extended and shows UGC 11430, is found more than 10 arcmin to the north. However, awarp of the disc. UGC 11429 is moving in the densest part of the local supercluster, in Hercules, which could explain its asymmetry. UGC 11124 The maximum of the rotation curve seems to be reached within the UGC 12276 (NGC 7440) optical limit of the disc. The H I velocity field obtained by WHISP The pattern of the isovelocity lines observed in the northern arm suggests a slight warp at the edge of the H I disc. suggests a gradient along the spiral arm which is not consistent with the expected position of the major axis (160◦ from the LEDA data UGC 11429 (NGC 6792) base). Indeed, this strange pattern is fully confirmed by the H I ve- Our velocity field shows classical distortions of the isovelocity lines locity field observed by WHISP and is probably the signature of the when crossing the strong southern spiral arm and the pattern of these strong central bar, with the well known tendency of the isovelocity lines for the receding side shows a change in the position angle of lines to follow the main axis of the bar. Adopting an inclination of
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Figure B15. UGC 12276. Left: GHASP monochromatic image with Hα isovelocities superimposed (in km s−1). Right: Hα rotation curve (crosses for receding side and dots for approaching) with the fit superimposed.
Figure B16. UGC 12276c. Left: GHASP monochromatic image with Hα radial isovelocities superimposed (in km s−1). Right: Hα rotation curve (crosses for receding side and dots for approaching) with the fit superimposed.
38◦ (as suggested by the axis ratio) and a position angle of 140◦ for satisfactory rotation curve, assuming an inclination of 35◦ (deduced the major axis, we find a satisfactory rotation curve. The approach- from the axis ratio) and a position angle of 150◦ for the major axis ing side gives velocity points only between 20 and 30 arcsec, which (we took into account the points lying within 50◦ from the major is sufficient, however, to confirm the symmetry of the plateau and axis). We find that the rotation centre is significantly offset (about 4 to adjust the systemic velocity. Our results are consistent with the arcsec to the south-east) with respect to the nucleus of this galaxy as H I velocity plot by WHISP, at least for the amplitude of the curve, identified on the continuum image (we also note that the nucleus is although no clear plateau can be guessed at on the H I data. coincident with the maximum of the Hα emission of the disc). This offset, which can be guessed at from the pattern of the isovelocity lines, is enormous since it is more than half the radius of the galaxy! UGC 12276 companion Anyway, the rising parts of both sides, receding and approaching, This companion of UGC 12276 is found almost 2 arcmin to the are fairly symmetric and our rotation curve rises up to a maximum north of this last one. It is a small compact galaxy, about 12 arcsec of 70 km s−1 at 5 arcsec. Then it is slowly decreasing down to in diameter, rich in Hα emission, with a systemic velocity close to 50 km s−1 at 8 arcsec, the declining part being traced only by the that of its large neighbour, so that we unexpectedly got its veloc- receding side. This companion can be seen as a small spot on the ity field while observing UGC 12276. Despite its small size and H I map of WHISP, without any detail, so that no useful informa- faint inclination, it has a rather large velocity amplitude, with radial tion can be obtained about the kinematics of the neutral gas in this velocities ranging from 5670 to 5750 km s−1.Wecould derive a object.
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Table B1. Galaxy parameters.
◦ N R25 Rlast V MAX Sin Sout AD µRo B − Vf Notes UGC kpc kpc km s−1 km s−1 kpc−1 km s−1 kpc−1 mag arcsec−2 mag mag (1) (2) (3) (4) (5) (6) (7) (8) (9) (10) (11)
508 26.5 25.5 363 0.09 0.82 −2.8 fit not reliable 528 2.2 1.1 69 0.45 I peculiar 763 8 10.1 109 23.5 −0.4 0.1 19.33±0.1 0.44 −2.6 1117 8.7 0.8 60.7 0.47 −5.1 cut 1249 4.4 4 70 0.50 −0.9 interacting 1256 5.4 4.6 97 0.45 −1.3 interacting 1736 13.8 10.3 179 0.15 0.48 I fit not reliable 1886 25.1 36.7 279 69.1 2.4 0.11 I 1913 14.8 8.4 135 0.35 0.50 −4.8 fit not reliable Downloaded from https://academic.oup.com/mnras/article/362/1/127/1339746 by guest on 30 September 2021 2023 2.8 3.1 59 0.25 0.53 −4fitnot reliable 2034 3.1 2.4 37 0.36 0.42 −3fitnot reliable 2045 4.3 4.4 141 101.2 6.6 16.8±0.2 0.64 0.0 interacting 2053 0.30 −3.1 no RC 2080 8.7 8 129 111 8.3 0.08 0.63 −3.3 2082 7.3 5.5 74 0.27 I fit not reliable 2141 4.7 4.8 136 28.4 0.13 −2.8 2183 7 4.6 122 97.8 −6 0.07 −4.1 2193 4.2 4.1 57 56.7 5.9 0.19 18.4±0.9 0.55 −4 2455 2.3 1.5 24 35.1 0.79 20±0.2 0.41 I 2503 19.1 17 284 42.9 0.6 0.07 17.9±0.2 0.64 −2.1 2800 5.7 4.5 88 19.7 0.16 −3.2 2855 9.6 9.4 285 −2.8 warped 3013 20.1 22.9 209 55.5 −1.6 0.08 0.55 −4.9 3273 3 3.8 83 25.5 0.17 21±0.05 I 3384 InoRC 3429 9.3 9.4 343 78.6 9.7 0.1 18.6±0.5 0.63 −3.2 3574 9.6 11.2 106 0.13 −3.8 fit not reliable 3691 9.2 8.6 136 0.10 I fit not reliable 3734 3.4 6 175 191.1 9.1 0.13 0.7 I 3809 26.1 22.8 255 72.4 1.7 0.06 17.4±0.5 0.49 −2.6 3851 3.4 2.6 67 17.8±0.7 0.54 −1 interacting 4273 12 12.9 194 35.1 1 0.07 −3 4274 2.7 1.5 67 54.7 0.35 20±0.1 0.59 −4.2 4278 5 4.5 0.19 0.4 −2.1 impossible to fit 4284 6.3 5.1 113 0.37 −4.5 cut 4305 4.4 2.9 34 0.66 0.42 −4.8 fit not reliable 4325 3.3 2.5 115 0.36 0.39 −4.5 fit not reliable 4499 3.1 3.5 61 40.2 0.3 0.24 20.6±0.4 −0.4 4543 8.3 11.9 81 0.26 −2.4 fit not reliable 4936 19.8 18.2 98 25.1 2.5 0.18 0.44 −2.6 5253 10.6 8.2 254 178.4 2.6 0.06 0.63 −3.5 5272 2 2.2 51 0.28 0.39 −2.1 fit not reliable 5316 8.2 10.7 166 15.4 0.17 0.4 −2.2 5414 3.9 3.6 51 0.40 −2.9 fit not reliable 5721 1.9 2.6 92 35 0.21 19.2±0.2 0.36 −2.2 5789 8.2 8.8 105 0.22 0.37 −3.6 fit not reliable 5829 5.6 6.6 50 0.53 0.2 −2.6 fit not reliable 5931 6.8 8.8 106 0.28 −0.4 interacting 5935 8.3 3.1 0.3 interacting 5982 12.4 15.1 203 147.3 5.3 0.07 0.57 −1.8 6537 8.4 9.9 165 0.44 −4.5 cut 6628 4.4 5.2 59 0.45 −4fitnot reliable 6702 14.4 16.1 178 58.2 −0.6 0.09 0.6 −2.3 6778 7.6 6.7 202 48.1 0.08 18.5±0.1 −1.7 7278 −0.8 no RC
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Table B1 Ð continued
◦ N R25 Rlast V MAX Sin Sout AD µRo B − V f notes UGC kpc kpc km s−1 km s−1 kpc−1 km s−1 kpc−1 mag arcsec−2 mag (1) (2) (3) (4) (5) (6) (7) (8) (9) (10) (11)
7323 4.8 4.7 89 18.9 0.19 19.7±0.2 0.54 −3.2 7524 7.4 3.7 63 0.23 0.46 −3.9 fit not reliable 7592 2.4 −4.3 no RC 7971 2.2 1.9 0.70 0.48 −4.4 impossible to fit 8490 1.8 1.6 82 52 0.14 19.8±0.3 0.41 −3.1 9366 16 13.5 238 122.3 1.9 0.08 17.9±0.7 0.55 −3.5 9649 2.4 3.1 111 45.1 0.14 I 9753 6.2 6.2 145 124.7 −2.1 0.09 17.5±0.4 0.47 −4.6 9858 22.3 27.8 179 0.21 −3.9 fit not reliable Downloaded from https://academic.oup.com/mnras/article/362/1/127/1339746 by guest on 30 September 2021 9969 25.1 22.2 288 50.9 0.7 0.65 −1.4 interacting 9992 InoRC 10310 3.9 2.9 72 0.42 −1.1 interacting 10359 8.2 11.4 147 19.4 0.2 19.5±0.4 0.48 −2.8 10445 4.3 6.4 72 29 0.4 0.14 20.2±0.1 I 10470 8.3 8.7 144 42.6 −2.4 0.08 0.56 I 10502 18.4 21.8 319 42.5 0.15 −2.3 10546 6.2 9 160 0.28 −3.7 fit not reliable 10564 5.4 7.7 80 8.5 0.22 −3.2 10897 5.4 3.9 97 0.22 0.46 I fit not reliable 11124 7.9 7.3 131 17.9 0.21 −2.7 11218 13.3 9 201 134.1 9.8 0.07 0.5 I 11283 6.3 4.2 186 61.8 0.08 0.5 −3.4 11283c 0.74 −2.7 impossible to fit 11300 3.6 3.5 104 38.9 0.17 0.59 I 11429 19.5 20.9 187 0.28 −3.5 fit not reliable 11557 5.8 6 59 15.2 0.17 20±0.2 I 11707 4.4 9.4 92 0.23 I fit not reliable 11852 12.1 9.5 201 43.6 0.06 I 11861 7.7 11.9 169 14.3 0.11 I 11891 3.6 2.9 81 0.24 I fit not reliable 11909 5.3 8 164 25.9 0.15 I 11914 6.9 6.6 262 526 0.06 0.77 I 11951 3.8 6.1 205 0.20 I 12060 5.1 9.1 111 0.25 21.4±0.9 I fit not reliable 12101 3 2.7 136 0.30 0.51 I fit not reliable 12212 3.3 3.1 43 13.9 0.14 −3.4 12276 14.4 11.1 120 29.2 0.7 0.06 0.73 −2.5 12276c 3.0 63 0.08 −1.2 interacting 12343 18.8 21.1 239 0.12 0.66 I fit not reliable 12632 3.1 4.4 58 0.36 0.55 I fit not reliable 12754 5.9 5.7 138 39.2 0.13 0.46 −2.5
(1) Name of the galaxy in the UGC catalog. (2) Isophotal radius in kpc at the limiting surfce brightness of 25 B mag arcsec−2 adopting the distance given in Table 2. (3) Extension of the ionized disc in kpc adopting the distance given in Table 2. (4) Maximal rotational velocity deduced from our RCs. (5) Inner slope of the RC. (6) Outer slope of the RC. (7) Asymmetry of the RC. (8) Central surface brightness in the R-band. (9) Colour of the galaxy. (10) f values (I means isolated). (11) Explanation of the reason why a galaxy has not been taken into account in the analysis: cut when the galaxy has been cut by the field of view or by a filter; peculiar when kinematics of the galaxy is very disturbed (e.g. counter-rotation motions).
This paper has been typeset from a TEX/LATEX file prepared by the author.
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