arXiv:astro-ph/0306497v1 24 Jun 2003 h sado aPlab N nteSaihObservatorio Astrof´ısica Spanish d de the Instituto the in of ING Muchachos Canarias Los by de Palma Roque La del of island the ucay&Rgn19)o hte necs fbars 1995, of Rieke excess & an McLeod whether 1995, or al. 1997) Regan et & Moles Mulchaey 1980, Simkim 1980, al. (Heckman galaxies et barred Seyfert gas in for occur preference the to fuel- no make nuclei is the there to facilitate Whether 1991) therefore mechanism. ing and Hernquist momentum & angular Barnes lose 1989, Shlosman 1980, al. potential al. et et axisymmetric (Simkin non works the theoretical in provide induced invoked bar torques In galactic gravitational (AGN). a nucleus and by galactic shocks active the to the down particular, ef- fuel scale galaxy an to the nucleus as from the gas invoked the transport frequently to of way been ficient components has non-axisymmetric potential galactic of existence The Introduction 1. edopitrqet to requests offprint Send ⋆ DI ilb netdb adlater) hand by inserted be will (DOI: Astrophysics & Astronomy h eeto fselrvlct iprindosi h ce the in drops dispersion velocity stellar of detection The .M´arquezI. ae nosrain aewt h H prtdon operated WHT the with made observations on Based 1 2 3 aais niiul C14 G 23 G 69 G 84 N 6814, NGC 2639, NGC 3223, UGC 184, IC individual: galaxies: 4 rmorpeiu aa,b sn ogsi pcrsoyi t in spectroscopy UG slit 184, long IC using paper, by this data), in previous presented our data from new with (four sample Abstract. Accepted / Received e words. m Key the constraining confirm help if could drops; properties the whose gala to s population, spatially 5 they values, corresponding our EW(CaT) regions for constant the lines with ep consistent triplet an formally Calcium during be formed the disk t of circumnuclear due widths probably a Existin equivalent most in 6951. is accreted NGC drop gas a and cold such 6814 that Evi NGC predict drops. formation are kinematical star exceptions the only of The are scales cases. drops, the at dispersion available structures velocity The inner reported 6814). with (NGC th galaxies galaxy in remaining nine dispersions the velocity in the hinted of and drop A telescope. 4m-class nttt eAto´sc eAdlcı CSIC) Apart Andaluc´ıa (C.S.I.C.), Astrof´ısica de de Instituto ntttdAtohsqed ai,CR,9bsB rg,F- Arago, Bd 98bis CNRS, Paris, de d’Astrophysique Institut eatmnod srnmı,Uiesddd hl,Casill Chile, de Astronom´ıa, Universidad de Departamento bevtre fteCrei nttto fWsigo,8 Washington, of Institution Carnegie the of Observatories 1 .Masegosa J. , eaayeteknmtc ftecnrlrgoso v isola five of regions central the of kinematics the analyze We aais prl–glxe:knmtc n yais–gala – dynamics and kinematics galaxies: – spiral galaxies: ein ffieioae efr spirals. Seyfert isolated five of regions .M´arquez ( I. : aucitn.drops˙astro no. manuscript 1 .Durret F. , [email protected]) 2 ..Gonz´alez Delgado R.M. , .Roth M. e d 04,E100Gaaa Spain Granada, E-18080 , 3004 ado t iprini he fte Esle ta.2001). al. this veloc- reproduce et the properly (Emsellem of not drop them could a models of as their three well Although in as dispersion region, kinemat- nuclear ity decoupled the of in existence ISAAC ics and the VLT shown the recently with have obtained AGNs of hosts galaxy to channels the engine. of central one the into be and gas to ubiquitous, feed proposed not are are spirals bars nuclear nuclear 2003b) & such 2003a, that Martini al. shown et 1999, has Circinus Martini Mulchaey 2000, HST galaxy, al. P´erez & the 2 et 1999, of (Regan Pogge Seyfert analysis Seyferts the a 2782 of However, in images NGC 2000). and al. in et starburst 1999) (Maiolino central al. intense et molec- & an (Jogee fuel Heller into to suggested 1994; gas al. been Combes ular et has 1993; which (Shlosman one 1994), Martinet bars regions; Shlosman central nested & very of Friedli the that 1989; is to is mechanism gas mechanism another the bar, such drive scale to large Nevertheless, needed the issue. to open addition an still in is exists, Seyferts among loue oivsiaetepeec fmorphological of presence the investigate to used also innermost e d hswudipytepeec fadffrn stellar different a of presence the imply would this ed, ec o iklk hpsi on n1 u fte14 the of out 12 in found is shapes disk-like for dence odels. ishv enmaue.Ee ftepolscould profiles the if Even measured. been have xies eCI rpe ag (at range triplet CaII he 4 3BraaSre,Psdn,CA91101 Pasadena, Street, Barbara 13 6,Snig,Chile Santiago, 36D, a e oidct h rsneo oa aiu in maximum local a of presence the indicate to eem tla ieaia rfie ffu obebarred double four of profiles kinematical Stellar on tla ouainbr rmdynamically from born population stellar young a o sd fcnrlgsaceindie yabr The bar. a by driven accretion gas central of isode S mgsfrorsml oehrwt another with together sample our for images HST 51 ai,France Paris, 75014 23 G 69 G 84 n G 6951 NGC and 6814, NGC 2639, NGC 3223, C C6951 GC -oysmltosicuigsas a and gas stars, including simulations N-body g e efr prlglxe rmteDEGAS the from galaxies spiral Seyfert ted 1 ± .Moles M. , is tutr aais neato – interaction galaxies: – structure xies: 13 rsci bevdi oro them, of four in observed is arcsec (1-3) 1 .Maza J. , ≈ 8600 )otie iha with obtained A) ˚ ⋆ 3 .P´erez E. , coe 9 2018 29, October ntral 1 and , 2 M´arquez et al.: Stellar velocity dispersion drops in isolated Seyfert spirals drop, Emsellem et al. suggested that it was due to a tran- Table 1. Detailed log of the spectroscopic observations sient cold nuclear disk fueled by gas inflow along the bar, which has recently formed new stars. Models by Wozniak & Michel-Dansac (2003) have recently succeeded in ac- Galaxy Date Spectral
Fig. 1. IC 184. Top left: velocity curve of the gas (open circles, from M´arquez et al. 2003) and stars (black circles) along PA=7◦. Top middle: FWHM of the stellar component along PA=7◦. Top right: FWHM of the stellar component along PA=97◦. Bottom left: HST image of IC 184 in the F606W band with the two slits superimposed; the ellipses correspond (PA and ellipticities) to the two bars detected in the infrared (M´arquez et al. 1999). Bottom middle: sharp divided image of the center.
The errors refer to the dispersion in the velocity shifts the last two columns the central rest frame wavelength of measured with respect to the different template stars. For each continuum band is given (the width used is 15 A).˚ clarity, error bars in the stellar velocity distributions are The differences in the continuum bands used may be the not plotted, but they typically amount to ±50 km s−1, reason why we measure systematically lower equivalent with median values of ±35 km s−1 for NGC 6951, and up widths (EW) than those reported in TDT90 for the same to ±70 km s−1 for NGC 2639. The systemic velocity has types of active galaxies. As TDT90 pointed out, to obtain been chosen as that of the section with the maximum con- conclusions on the stellar population based on CaII triplet tinuum level, except for IC 184, for which the kinematical measurements, exactly the same method has to be used. center (the point that allows the best symmetrization of For our data the results are specially tricky due to the fact the rotation curve) is shifted by about 0.8 arcsec to the that the TiO and VO bands contaminate the “red” con- South with respect to the continuum maximum. tinuum. In order to quantify the uncertainty due to the choice of the continuum level, we have used three differ- The Calcium triplet equivalent width has been mea- ent “red” continua and measured the corresponding EW; sured following the method described by Terlevich et al. the error bars in Fig. 6 are calculated as the dispersion of (1990, hereafter, TDT90), which uses two specific contin- these three values, and therefore represent lower limits to uum bands on either side of the CaT region, after Doppler the true error bars. The minimum uncertainty obtained shift corrections for each section. Due to a shorter spectral for the best cases with a flat continuum is 0.5 A˚ but in range coverage than TDT90, slight modifications of the most of the galaxies the uncertainty can be larger than central wavelength of the “blue” continuum were adopted 1.5 A.˚ for all the galaxies except NGC 2639. For the “red” con- tinuum, we had to use much shorter wavelengths than CaT equivalent widths have also been measured using TDT90. The resulting equivalent widths for the inner re- the method by Cenarro et al. (2001). The comparison be- gions of each galaxy (see Sect. 3) are given in Table 3. In tween this method and that of TDT90 has shown that, in 4 M´arquez et al.: Stellar velocity dispersion drops in isolated Seyfert spirals
Fig. 2. UGC 3223. Top left: velocity curve of the gas (open circles, from M´arquez et al. 2003) and stars (black circles) along PA=80◦. Top right: FWHM of the stellar component along PA=80◦. Bottom left: HST image of UGC 3223 in the F606W band with the two slits superimposed; the ellipses correspond (PA and ellipticities) to the two bars detected in the infrared (M´arquez et al. 1999). Bottom right: sharp divided image of the center.
Table 3. CaT Equivalent widths are drawn on the figures, together with the bar sizes and ellipticities as determined in M´arquez et al. (1999), for the primary bar in single-barred galaxies (NGC 6814 and
Galaxy PA EW EW EW “blue” “red” NGC 6951) and for primary and secondary (inner) bars in Ca2 Ca3 CaII cont. cont. double-barred ones (IC 184, NGC 2639 and UGC 3223). IC 184 7 3.5 (0.3) 2.8 (0.6) 6.3 (1.8) 8458 8680 The results for the CaII triplet EW measurements of each 97 4.0 (0.3) 2.7 (0.4) 6.7 (0.6) 8458 8680 galaxy are presented in Table 3. Since we are interested UGC 3223 80 3.5 (0.1) 2.8 (0.3) 6.3 (0.7) 8458 8700 NGC 2639 45 3.0 (0.1) 2.6 (0.1) 5.7 (0.3) 8455 8700 in searching for the properties of stellar populations in 135 3.5 (0.1) 2.6 (0.2) 6.1 (0.5) 8455 8700 the regions where the dips have been detected, the values NGC 6814 30 3.5 (0.2) 2.5 (0.5) 6.1 (1.3) 8484 8700 120 3.5 (0.2) 2.5 (0.5) 6.0 (1.3) 8484 8700 given in Table 3 refer to the whole region occupied by the NGC 6951 48 3.7 (0.1) 3.3 (0.1) 7.0 (0.3) 8482 8750 drops. 138 3.4 (0.1) 3.1 (0.3) 6.6 (0.7) 8482 8750 Ca2 = CaT line at 8542A˚ Ca3 = CaT line at 8662A˚ EW(CaII) = EW(Ca2) + EW(Ca3) 3.1. IC 184 the case of dilution due to an important underlying old ◦ stellar population, TDT90 seem to be less sensitive to the The rotation curves along PA=7 (major axis) (Fig. 1) ◦ contamination by TiO and VO lines. Therefore, since our and 97 show that the rotation of the gas and stars are ◦ sample galaxies are all early type spirals, we have adopted strongly decoupled along PA=7 within ±4 arcsec of the the TDT90 method. center, with a central region of stellar counter-rotation ◦ For our five sample galaxies and for nine of the eleven within 1 arcsec, which is also visible along PA=97 (not galaxies with velocity dispersion drops reported in the lit- shown here). In order to know if such kinematics are due erature (see Sect. 4) the available archival WFPC2 HST2 to the presence of a counter rotating core, as it is the optical images (see Table 2 for details) have been used case for NGC 4621 (Wernli et al. 2002) integral field spec- −1 to identify features which, according to numerical mod- troscopy is required. A small dip of about 20 km s with els, could possibly be related to the kinematics. To trace respect to the maximum value is observed in the veloc- the presence of morphological features in the innermost ity dispersion in the innermost ±2 arcsec. The stellar ve- ◦ few arcseconds, both raw and sharp–divided images3 have locity distribution along PA=97 shows structure within been used. Sharp–divided images are very useful to trace the innermost ±9 arcsec, with a wavy central shape sim- ◦ asymmetries in the light distribution, such as bars, spiral ilar to that observed along PA=7 . This extension corre- arms, dust lanes and rings. This technique allows the sub- sponds to that of the primary bar, which extends along ◦ ◦ traction of the diffuse background in a very convenient way PA=170 (M´arquez et al. 2000), i.e. only 17 from the to look for subtle, small-scale variations and discuss the disk major axis. We note that the secondary bar extends ◦ possible presence of both dust extinguished and more lu- ±4 arcsec along PA=30 (M´arquez et al. 2000) and there- minous regions (Sofue et al. 1994; M´arquez & Moles 1996; fore the velocity difference between the stellar and gas Erwin & Sparke 1999; Laine et al. 1999; M´arquez et al. components in this region is most likely due to the non- 1999; Erwin & Sparke 2002). circular motions caused by the secondary bar. EW(CaT) shows a slight tendency for central values to be higher along both PAs, particularly along PA=97◦(Fig. 6a). 3. Results
The kinematical data and the images used in the analysis The HST image of IC 184 (Fig. 1) shows a structure of the data are displayed in Figs. 1 to 4. The points corre- in the innermost 1 arcsec elongated along PA ≈ 50◦, very sponding to gas kinematics are given for comparison (for close to the position angle of the inner bar in the same further details on the gas kinematics see M´arquez et al. image (PA ≈ 40◦); although this feature is detected in a 2003). The slit positions (measured from North to East) much smaller region, its PA is consistent with that of the 2 Based on observations collected with the NASA/ESA HST, small inner bar already detected in the infrared (M´arquez obtained at STScI which is operated by AURA Inc., under et al. 1999). A structure resembling two straight dust lanes NASA contract NAS5-26555 may be seen in the sharp-divided image running along ◦ 3 The result of dividing the original images by median– about PA ≈ 45 , below the center to the SW and above filtered ones. the center to the NE, respectively. M´arquez et al.: Stellar velocity dispersion drops in isolated Seyfert spirals 5
Fig. 3. NGC 2639. Top left: velocity curve of the gas (open circles, from M´arquez et al. 2003) and stars (black circles) along PA=45◦. Top middle: FWHM of the stellar component along PA=45◦. Top right: FWHM of the stellar component along PA=135◦. Bottom left: HST image of NGC 2639 in the F606W band with the two slits superimposed; the ellipses correspond (PA and ellipticities) to the two bars detected in the infrared (M´arquez et al. 1999). Bottom middle: sharp divided image of the center.
3.2. UGC 3223 3.3. NGC 2639
◦ NGC 2639 is a galaxy optically classified as unbarred, The rotation curve of UGC 3223 along PA=80 (very close ◦ but barred at NIR wavelengths (M´arquez et al. 1999). to the bar major axis, PA=75 ), although rather noisy, The stellar and gas rotation curves of NGC 2639 along shows that the overall rotation of the gas follows, within ◦ PA=135 (disk and main bar major axis, not shown here) the error bars, that of the stars (Fig. 2). Positive stellar −1 show that both components have different velocities (up velocities are systematically lower (down to 80 km s ) − to 100 km s 1) in the region inside the bar (inner ±8 than their negative counterparts for radii between 2 and −1 arcsec) (M´arquez et al. 2003). The gaseous velocity distri- 20 arcseconds. A small dip (≈ 10 kms ) may be observed ◦ − bution along PA=0 shows departures of 50 km s 1from in the velocity dispersion in the innermost ± 1 arcsec, but pure rotation in the region within r<4 arcsec (M´arquez needs to be confirmed with data of higher signal to noise. ◦ et al. 2003). Along PA=45 the velocity distribution is In spite of the low S/N ratio of the spectra, an increase quite flat, as expected along a position angle close to the in EW(CaT) is detected in the innermost ±1 arcsec, cor- minor axis, whereas clear non-circular motions are traced responding to the extension of the detected dip (see Fig. by the gas kinematics in the central 2 − 3 arcsec radius 6b). − (Fig. 3). A velocity dispersion drop of ≈ 20 km s 1 is The HST image of UGC 3223 (Fig. 2) shows an detected along the two PAs in the innermost ±2 arcsec, ◦ asymmetric structure in the innermost 1 arcsec elongated being more clearly detected along PA=45 (Fig. 3). A hint ◦ mainly along PA=80◦, and more extended to the West, of an increase in EW(CaT) is detected along PA=45 and ◦ consistent with that of the small inner bar already de- 135 (Fig. 6c). tected in the infrared (M´arquez et al. 1999). Another ex- The HST image of NGC 2639 (Fig. 3) shows a struc- tension can be seen to the NE along PA∼55◦, resembling ture elongated along PA=135◦ in the innermost ±1 arc- what could be an incomplete ring at r=0.9 arcsec. sec (consistent with the thin inner bar detected in the 6 M´arquez et al.: Stellar velocity dispersion drops in isolated Seyfert spirals
Fig. 4. NGC 6814. Top left: velocity curve of the gas (open circles, from M´arquez et al. 2003) and stars (black circles) along PA=120◦. Top middle: FWHM of the stellar component along PA=120◦. Top right: FWHM of the stellar component along PA=30◦. Bottom left: HST image of NGC 6814 in the F606W band with the two slits superimposed; the ellipse corresponds (PA and ellipticity) to the bar detected in the infrared (M´arquez et al. 1999). Bottom middle: sharp divided image of the center. infrared, M´arquez et al. 1999), which is somewhat more PA=120◦ in the innermost 1.5 arcsec and a dust lane extended and curved towards the NW. along PA≈ 60◦ within 1 arcsec (Fig. 4).
3.4. NGC 6814 3.5. NGC 6951
NGC 6814 has a small inclination and it is therefore dif- The stellar velocity distributions of NGC 6951 are given ficult to derive its kinematical parameters accurately. It in P´erez et al. (2000). We recall that two stellar compo- is a single barred galaxy, with a ±12 arcsec bar extend- nents have been clearly detected, with amplitude differ- ◦ ences up to 50 km s−1along PA=84◦ and PA=138◦. A ing along PA=25 (M´arquez et al. 1999). Note that the ◦ innermost ±3 arcsec show velocity dispersions about 30 similar behavior is observed along PA=48 in the region km s−1lower than the average values out to about 8 arc- between r=5 and 10 arcsec, which corresponds to stellar sec along PA=120◦, an effect which also seems to be de- velocity dispersion peaks (Fig. 5). Higher S/N data would tected along PA=30◦. Higher S/N data are needed in or- be required to obtain FWHM measurements for the two der to confirm the presence of this drop. Although noiser, separate components, but their physical connection with this profile resembles that of NGC 6951, both showing the FWHM peaks seems to be hinted by our data. The en- a broader central drop than the other three galaxies in hancement of EW(CaT) in the central region was already our sample. As shown in Fig. 6d, a slight enhancement in reported and discussed in P´erez et al. (2000). EW(CaT) has been detected along the extension of the dip along PA=30◦. 4. Discussion and conclusions The HST sharp-divided image of NGC 6814 shows a small (r < 2 arcsec) several-armed spiral structure (in New stellar kinematics for a sample of four active galaxies dark grey), with a clear elongation to the West along using the Calcium triplet have been obtained and we have M´arquez et al.: Stellar velocity dispersion drops in isolated Seyfert spirals 7
telescopes. It is worth noticing that the velocity dispersion drops have been detected in three double-barred galaxies and in two single-barred ones, already indicating that the presence of nested bars is not a necessary condition; the drops in the later cases seem to be broader than in the former. Note that such a dip is until now a rarely observed phe- nomenon, reported so far only for eleven nearby galaxies (most of them listed in Wozniak et al. 2003b; see references below), three of them from recent VLT observations using the 12CO bands in the near IR (Emsellem et al. 2001). This is most probably due to the difficulty of estimating the FWHM of the stellar component with a sufficient sig- nal to noise ratio and spatial resolution. Michel-Dansac & Wozniak (2003) have recently mod- eled the evolution of isolated galaxies over several Gyrs Fig. 5. NGC 6951. FWHM of the stellar component along ◦ using a self-consistent N-body code including stars, gas PA=48 . and star formation. With such models, they succeeded in accounting for the drop in velocity dispersion observed by Emsellem et al. (2001) in three double-barred and one single-barred active galaxies, with a young stellar popu- lation born from dynamically cold gas which is accreted in a circumnuclear disk and creates the dip (Wozniak et al. 2003a, Wozniak & Michel-Dansac 2003). We note that their simulations do not require the presence of embedded bar structures, since such processes can be induced by the primary bar itself (see also Wozniak et al. 2003b). Since under these circumstances a luminosity domi- nating young stellar component is expected in the region where the drops are observed, it is worth trying to detect such a component in order to better validate the model. We have attempted to do so by analyzing the equivalent widths of the CaT lines along the dips and by inspect- ing the inner structure in high resolution HST images. The analysis of HST images for the target galaxies shows that structure is indeed present in the regions where the dips occur in IC 184, UGC 3223 and NGC 26394. The same conclusion is valid when inspecting the sharp-divided frames of those galaxies with available HST archive images Fig. 6. Spatial distribution of the CaT equivalent width and with velocity dispersion drops reported in the litera- ◦ (EW) in the central regions of: a) IC 184 (PA=7 as full ture, namely NGC 1365 and NGC 1808 (Emsellem et al. ◦ ◦ line, PA=97 as dotted line), b) UGC 3223, PA=80 , 2001; for the Sy1 NGC 1097 there are only F218W images, ◦ ◦ c) NGC 2639 (PA=45 as full line, PA=135 as dotted that do not allow to detect such structures), NGC 6503 ◦ ◦ line) and d) NGC 6814 (PA=30 as full line, PA=120 as (Bottema 1993), NGC 3627, NGC 4303, NGC 4579 dotted line). The corresponding plot for NGC 6951 is given (H´eraudeau & Simien 1998), NGC 4725 (H´eraudeau et in P´erez et al. (2000). al. 1999; diffraction spikes impede a reliable determina- tion of the hinted central elongated structure), NGC 4477 (Jarvis et al. 1988), NGC 3623 (de Zeeuw et al. 2002) shown that reliable stellar velocity curves can be traced. and NGC 3412 (Aguerri et al. 2003). Note that the im- Three of these galaxies show double bar-like confirmed ages are at a wavelength range that does not include the structure at optical and/or near IR frequencies. The previ- CaT, so we do not expect to find exactly the same struc- ously reported data for NGC 6951 (a single-barred galaxy ture. Also the spectroscopic structure is diluted because with a nuclear spiral, P´erez et al. 2000) have been added of the poorer ground-based spatial resolution. Therefore, to the present study, in particular the velocity dispersion the presence of structure in HST images at the scales of curve. We have observed a dip in the stellar velocity disper- 4 With our small sample (5 galaxies) we find no dependence sion in the innermost ±(1-3) arcsec of these five active of the drop sizes with respect to those of the outer/inner bars; galaxies based on observations made with 4 meter class a larger sample should be needed in order to analyze this point. 8 M´arquez et al.: Stellar velocity dispersion drops in isolated Seyfert spirals the velocity dispersion drops is only a consistency check. for the first time in this work – 15 host AGNs5, either The existence of a direct correlation between the two ob- Seyfert 1 (3), Seyfert 2 (7), LINERs (2), or intermedi- servables needs further investigation with similar spatial ate type LINER/Sy2 (3); the only galaxy with no evident resolution data. signs of nuclear activity is NGC 3412 (Ho et al. 1995). The velocity dispersion drop in NGC 6814 seems to be The DEGAS sample is particularly well adapted for this as broad as that in NGC 6951, and it is only for NGC 6814 purpose, since it is well defined and comprises only iso- and NGC 6951 (LINER/Sy2) that the drops seem to be lated galaxies, where the complicating effects of galaxy present with no associated elongation in the images. This interactions are not present. may indicate that such structures either are seen face-on in these cases or are absent. For the other galaxies, if the Acknowledgements. We thank the referee, Eric Emsellem, for elongations are interpreted as intrinsically circular disks, his excellent report, which has largely helped us improve the these disks would be placed almost perpendicular to the clarity of the paper. I.M. acknowledges financial support from ◦ the IAA and the Spanish Ministerio de Ciencia y Tecnolog´ıa main disk in NGC 2639 (iinner disk ≈ 74 ), at intermediate ◦ through a Ram´on y Cajal fellowship. This work is financed angle for IC 184 (iinner disk ≈ 40 ) and coplanar with the by DGICyT grants PB93-0139, PB96-0921, PB98-0521, PB98- main disk in UGC 3223. 0684, ESP98-1351, AYA2001-2089, AYA2001-3939-C03-01 and The Calcium triplet equivalent width, EW(CaT), is ex- the Junta de Andaluc´ıa grant TIC-144. We acknowledge finan- pected to increase for younger populations. Unfortunately, cial support from the Picasso Programme d’Actions Integr´ees the comparison with stellar population models to test the of the French and Spanish Ministries of Foreign Affairs. F.D. age of such a population is rather risky, due to the al- acknowledges financial support from CNRS-INSU for several ready mentioned problem with the determination of the observing trips. E.P. acknowledges financial support from the continuum bands which impedes a quantitative compari- CONACYT (M´axico) grant 36132-E. J. Maza gratefully ac- son with other authors (for instance, the models developed knowledges support from the Chilean Centro de Astrof´ısica by Garc´ıa-Vargas et al. 1998 require EWs higher than FONDAP 15010003. We acknowledge Ignacio Marrero for those we have measured to invoke an important contri- his collaboration in some data acquisition and calibration. This research has made use of the NASA/IPAC extragalac- bution of super-giant stars). The variations on the values tic database (NED), which is operated by the Jet Propulsion of the EWs can still be compared but, due to the accu- Laboratory under contract with the National Aeronautics and racy achievable by using EW(CaT) measurements on our Space Administration. data, the analysis is not straightforward since we expect the relative differences in the EW(CaT) to be compara- ble to our accuracy (from 1 to 1.5 A),˚ and consequently References such variations can, strictly speaking, correspond to a con- Aguerri J.A.L, Debattista V.P., Corsini E.M. 2003, MNRAS stant value. Nevertheless, a hint of a local enhancement 338, 465 in the drop region is suggested by the data, a behavior Barnes J.E., Hernquist L.E., 1991, ApJ 370, 65 that could be due to the presence in these regions of a Bottema, R. 1993, A & A 275, 16 population different from that of the bulge. Cenarro A.J., Cardiel N., Gorgas J. et al. 2001, MNRAS 326, To confirm or discard Wozniak et al.’s models the 959 analysis of higher S/N spectra in a much broader wave- Colina L., Gonz´alez Delgado R.M., Mas-Hesse J.M., Leitherer length range is needed to constrain the age of the ob- C., Jim´enez-Bail´on E. 2002, ApJ 579, 545 served stellar populations detected in the central dips. On Combes F., 1994 in Mass Transfer Induced Activity in galaxies, this respect, we notice that some of the galaxies show evi- Cambridge University Press, 170 dence for the presence of an intermediate (NGC 3627 and Emsellem E., Greusard D., Combes F. et al. 2001, A&A 368, NGC 6503, Gonz´alez Delgado et al., in preparation) or 52 Erwin, P. & Sparke, L. 1999, ApJ 521, 37 young (NGC 4303, Colina et al. 2002) population in the Erwin P. & Sparke L.S. 2002, AJ 124, 65 regions where the dispersion drops take place and where Friedli D., Martinet L., 1993, A&A 277, 27 elongations are seen in the HST sharp-divided images. Garc´ıa-Vargas M.L., Moll´aM., Bressan A. 1998, A&AS 130, The case of NGC 6951 is specially interesting since 513 an alternative explanation for the presence of the appar- Heckman, T.M., 1980, A&A 87, 142 ent drop within r=5 arcsec in this galaxy would be the Heller C.H. & Shlosman I. 1994, ApJ 424, 84 existence of two stellar kinematic components. This ap- H´eraudeau Ph. & Simien F. 1998, A&AS 133, 317 pears as a possibility to be checked in the other four H´eraudeau Ph., Simien F., Maubon, G., Prugniel, Ph. 1999, galaxies with higher spectral resolution and S/N data. A&AS 136, 509 It would therefore be of particular interest to re-observe Ho L. C., Filippenko A. V., Sargent W. L. 1995, ApJS 98, 477 these five galaxies with an 8 meter class telescope, to de- Jarvis B. J., Dubath, P., Martinet L., Bacon, R. 1988, A&AS fine with better precision the characteristics of the dip, 74, 513 in particular its disk nature (for which several position Knapen J.H., Shlosman I., Peletier R.F., 2000, ApJ 529, 93 angles are required), and also to observe a larger sample Jogee S., Kenney J.D.P., Smith B.J., 1999, ApJ 526, 665 of galaxies with and without an AGN. Note that among 5 Their nuclear classification has been taken from NED and the 16 galaxies with reported drops – 5 of them presented is given in Table 2. M´arquez et al.: Stellar velocity dispersion drops in isolated Seyfert spirals 9
Laine S., Knapen J.H., P´erez-Ram´ırez D., Doyon R., Nadeau D., 1999, MNRAS 302, L33 Laine S., Shlosman I., Knapen J.H., Peletier R. 2002, ApJ 567, 97 Maiolino R., Alonso-Herrero A., Anders S. et al., 2000, ApJ 531, 219 M´arquez I., Moles M., 1996, A&AS 120, 1 M´arquez I., Durret F., Gonz´alez Delgado R.M. et al. 1999, A&AS 140, 1 M´arquez I., Durret F., Masegosa J. et al. 2000, A&A 360, 431 M´arquez I., Masegosa J., Moles M., Varela J., Bettoni D., Galletta, G. 2002, A&A 393, 389 M´arquez I., Durret F., Masegosa J. et al. 2003, in preparation Martini P., Pogge R.W., 1999, AJ 118, 2646 Martini P., Regan M.W., Mulchaey J.S., Pogge R.W. 2003a, ApJS 146, 353 Martini P., Regan M.W., Mulchaey J.S., Pogge R.W. 2003b, ApJ 589, 774 McLeod K.K., Rieke G.H., 1995, ApJ 441, 96 Michel-Dansac L. & Wozniak H. 2003, Proc. Symposium “The evolution of galaxies. III. From simple approaches to self- consistent models”, Kiel, Germany, July 16-20, 2002 Moles M., M´arquez I., P´erez E., 1995, ApJ 438, 604 Mulchaey J.S., Regan M.W., 1997, ApJL 482, L135 P´erez E., M´arquez I., Marrero I. et al., 2000, A&A 353, 893 Regan M.W., Mulchaey J.S., 1999, AJ 117, 2676 Shlosman I., Frank J. and Begelman, M. 1989, Nature 338, 45 Shlosman I., Peletier R.F., Knapen J.H. 2000, ApJ 565, 921 Simkim S.M., Su H.J, Schwarz M.P., 1980, ApJ 237, 404 Sofue Y., Yoshida S., Aoki T. et al., 1994, PASJ 46, 1 Terlevich E., D´ıaz A.I., Terlevich R. 1990, MNRAS 242, 271 Wernli F., Emsellem E., Copin Y. 2002, A&A 396, 73 Wozniak H. & Michel-Dansac L. 2003, Proc. Symposium “The evolution of galaxies. III. From simple approaches to self- consistent models”, Kiel, Germany, July 16-20, 2002 Wozniak H., Combes F., Emsellem E. et al. 2003a, Proc. Symposium “Active galactic nuclei, from central engine to host galaxy”, Observatoire de Paris-Meudon July 23-27, 2002 Wozniak H., Combes F., Emsellem E., Friedli, D. 2003b, A&A, in press de Zeeuw T., Bureau M., Emsellem E. et al. 2002, MNRAS 329, 513 This figure "marquez_fig1.jpg" is available in "jpg" format from:
http://arxiv.org/ps/astro-ph/0306497v1 This figure "marquez_fig2.jpg" is available in "jpg" format from:
http://arxiv.org/ps/astro-ph/0306497v1 This figure "marquez_fig3.jpg" is available in "jpg" format from:
http://arxiv.org/ps/astro-ph/0306497v1 This figure "marquez_fig4.jpg" is available in "jpg" format from:
http://arxiv.org/ps/astro-ph/0306497v1