THE UNIVERSITY OF ALABAMA University Libraries Dynamics of Ringed Barred Spiral Galaxies. I. Surface Photometry and Kinematics of NGC 1433 and NGC 6300 Ronald J. Buta – University of Alabama et al. Deposited 06/21/2019 Citation of published version: Buta, R., et al. (2001): Dynamics of Ringed Barred Spiral Galaxies. I. Surface Photometry and Kinematics of NGC 1433 and NGC 6300. The Astronomical Journal, 121(1). DOI: 10.1086/318024 © 2001. The American Astronomical Society. All rights reserved. Printed in U.S.A. THE ASTRONOMICAL JOURNAL, 121:225È243, 2001 January ( 2001. The American Astronomical Society. All rights reserved. Printed in U.S.A. DYNAMICS OF RINGED BARRED SPIRAL GALAXIES. I. SURFACE PHOTOMETRY AND KINEMATICS OF NGC 1433 AND NGC 6300 R. BUTA,1,2 STUART D. RYDER,2,3 GREGORY J. MADSEN,2,4 KAREN WESSON,5 D. A. CROCKER,1,2 AND F. COMBES6 Received 2000 July 11; accepted 2000 October 10 ABSTRACT This paper presents new near-infrared images and surface photometry and Ha Fabry-Perot radial velocities for NGC 1433 and NGC 6300, two large and previously well-studied nearby ringed barred spiral galaxies. Stellar absorption-line radial velocities and new optical surface photometry are also pre- sented for NGC 1433. The data are intended to set the stage for dynamical modeling of the two galaxies, with the principal goals being to derive mass distributions, bar mass-to-light ratios, bar pattern speeds, and resonance locations, parameters which have been derived for very few ringed disk galaxies. The pres- ence of strong rings and pseudorings in the two galaxies allows the possibility to link speciÐc orbital resonances with the observed rings. The new data allow us to derive a fairly complete composite rota- tion curve of NGC 1433, leading us to make some interesting preliminary judgments about the structure of the galaxy. The new data also verify the previous Ðnding that the radial velocity of the Seyfert nucleus in NGC 6300 di†ers from the actual systemic velocity of the galaxy by nearly 100 km s~1. We demon- strate in this paper that the o†set is not an artifact of signiÐcant extinction in the inner regions of the galaxy. Key words: galaxies: individual (NGC 1433, NGC 6300) È galaxies: kinematics and dynamics È galaxies: structure 1. INTRODUCTION axies, NGC 1433 and NGC 6300. Our goals are to simulate the structure of these galaxies using a test-particle code and Ringed disk galaxies are an important subgroup of the from the simulations derive the pattern speed of the bar, the barred spiral galaxy population. Rings are thought to form locations of orbital resonances, and the mass-to-light ratio by gas accumulation at resonances, under the continuous of the bar. Here all we do is present the supporting obser- action of gravity torques from the bar pattern (Buta & vational data needed for the simulations. This includes new Combes 1996). This association with orbital resonances Fabry-Perot velocity Ðelds, near-infrared images, long-slit makes rings in barred galaxies useful tracers of internal spectroscopy, and new optical surface photometry. The dynamics, and given the relative abundance of rings in simulations will be presented in Buta & Combes 2001 barred galaxies, means that studies of ringed galaxies could (Paper II). A preliminary discussion of these simulations is shed light on the dynamics of the disk galaxy population as provided by Buta & Combes (2000). a whole. However, very few ringed barred galaxies have ever been the subject of a detailed dynamical analysis. An excep- 2. SUMMARY OF PREVIOUS OBSERVATIONS OF NGC 1433 tion is IC 4214, for which a successful model was obtained AND 6300 by Salo et al. (1999). Dynamical models can be used to derive not only the mass distribution in a ringed barred The galaxies we analyze here are well studied, excellent spiral, but also the pattern speed of the bar and the location examples of ringed barred spiral galaxies. NGC 1433 is a of corotation relative to the ends of the bar. Such models classic ““ theta ÏÏ spiral Ðrst studied in great detail by Buta can also be used to test the idea that rings are connected (1986, hereafter B86). It is the nearest example of a ringed with speciÐc orbital resonances with the bar. Since bar barred spiral of de Vaucouleurs typeSB(rs)ab.- The inner pattern speeds are one of the fundamental unknowns of ring in this case is actually a pseudoring made up of tightly galaxy dynamics, studies of ringed galaxies could be partic- wrapped spiral arms that wind into an oval shape aligned ularly useful for determining trends in this parameter. along the bar axis. The galaxy also has an outer pseudoring In this paper, we set the stage for a dynamical analysis of about twice the diameter of the bar and a nuclear ring two large and somewhat dissimilar ringed barred disk gal- about 0.1 times the diameter of the bar. Just beyond the inner ring, on the leading sides of the bar, the galaxy also shows two striking partial spiral arcs (““ plumes ÏÏ) that are ÈÈÈÈÈÈÈÈÈÈÈÈÈÈÈ 1 Department of Physics and Astronomy, University of Alabama, rarely seen in barred galaxies (Buta 1984). Tuscaloosa, Alabama 35487-0324. Other early studies of NGC 1433 include that of Baum- 2 Visiting Astronomer, Cerro Tololo Inter-American Observatory, gart & Peterson (1986), who presented some photographic National Optical Astronomy Observatories, operated by the Association information on the near-infrared properties of the bar and of Universities for Research in Astronomy (AURA), Inc., under coopera- noted isophote twisting in the inner regions and a Freeman tive agreement with the National Science Foundation. 3 Anglo-Australian Observatory, P.O. Box 296, Epping, NSW 1710, (1970) type II exponential disk proÐle. Simien & de Vaucou- Australia. leurs (1986) used standard decomposition techniques to 4 Department of Astronomy, University of Wisconsin, 475 North derive a bulge contribution of 13% in blue light, uncertain Charter Street, Madison, WI 53706. because of the strong bar. Harnett (1987) mapped the radio 5 School of Environment, Duke University, Box 900328, Durham, NC 27708. continuum emission from NGC 1433 and found a slight 6 DEMIRM, Observatoire de Paris, 61 Avenue de lÏObservatoire, elongation of emission along the bar axis. Maia, da Costa, F75014 Paris, France. & Latham (1989) have placed NGC 1433 into a large group 225 226 BUTA ET AL. Vol. 121 (G13) including more than 40 other large, nearby southern CIRIM was used to observe NGC 6300 in 1997 July, also galaxies. The mean Virgocentric velocity of the group is on the CTIO 1.5 m telescope. In this case, it was only neces- only 753 km s~1. sary to observe two mosaic positions. At each mosaic posi- NGC 6300 is a well-known Seyfert 2 galaxy (Phillips, tion, we obtained two sets of Ðve dithered frames based on Charles, & Baldwin 1983) and hence has been the subject of 10 internal coadds of 6 s each. The Ðnal mosaic constructed many studies. It is an excellent SB(rs)Ètype spiral that pro- has a Ðeld of view of8.2@ ] 5.6.@ Since the observations were vides an interesting contrast with NGC 1433. First studied made with some clouds present, and no H-band aperture in global detail by Buta (1987, hereafter B87), NGC 6300 is photometry is available, we could not reliably calibrate this characterized by a relatively weak bar and strong spiral image. inner pseudoring. On deprojecting the galaxy, B87 noticed that the inner pseudoring is misaligned with the bar axis by 3.2. Optical Fabry-Perot Interferometry nearly 80¡. This misalignment is unusual for ringed barred The optical velocity data of NGC 1433 and NGC 6300 galaxies and in this case suggests the possibility that the were obtained in 1997 November and July with the Rutgers spiral arms in the inner pseudoring have a di†erent pattern Fabry-Perot (RFP) interferometer attached to the CTIO 1.5 speed from that of the bar. m and 4 m telescopes, respectively. The broad etalon with a The distribution and velocity Ðeld of atomic hydrogen in full width at half-maximum (FWHM) of 2.4Ó was used for NGC 1433 and 6300 were obtained by Ryder et al. (1996). all of the observations, and the Ha line was the only emis- These observations provided well-determined estimates of sion line used for the radial velocity measurements. the orientation parameters of the two galaxies. For NGC For NGC 1433, the velocity interval needed to cover the 1433, Ryder et al. determined a (receding) kinematic line of velocity Ðeld into the continuum was from 830 to 1290 km nodes position angle of 201¡ and favored an inclination of s~1. Two sequences of nine frames each and separated by 33¡ based on ellipse Ðts to outer isophote shapes by B86. 1.2Ó on average were used to cover this interval. Two We will not be able to improve much on these estimates sequences were used because the Ðeld of view of the RFP is here, so we will adopt them for some of our analysis. For 7.8@ at f/7.5 on the CTIO 1.5 m telescope, so the galaxy just NGC 6300, Ryder et al. found evidence for warping in the Ðts into the Ðeld. The Ðrst sequence had the galaxy centered outer H I disk, but in the inner optically bright part of the on the west half of the bar, while the second sequence had disk the velocities are consistent with a line of nodes posi- the galaxy centered near the east half of the bar. The two tion angle of 109¡ and an inclination of 50¡, similar to sequences gave us two separate velocity Ðelds which are values derived by B87.