D. A. Crocker

The Structure and Dynamics of the Early-Type Resonance Ring Galaxy IC 4214. II. Models

The first paper in this series presented optical (UBVI) and near-infrared (H) surface photometry and Hα Fabry-Perot interferometry of IC 4214, an excellent example of a multiringed galaxy with a weak bar. In the present paper, we analyze the nonaxisymmetric gravitational potential of IC 4214, as defined by the near-infrared data. The gas behavior is modeled with two-dimensional sticky particle simulations that employ a rigidly rotating nonaxisymmetric potential. Our goals are to interpret the morphology and velocity field of IC 4214 and to obtain a model from which the bar pattern speed, halo contribution, and relative bulge and disk masses can be deduced. We also study the orbital families in the derived IC 4214 model. A fairly good match, in both morphology and kinematics, is obtained for Ωbar ≈ 40 ± 5 km s-1 kpc-1, placing the bar corotation slightly beyond the end of the bar (rbar/rcr ≈ 0.72 ± 0.05). The deduced bar amplitude implies that the visible mass of the disk dominates over the unseen halo (Mdisk/Mhalo > 3–4). Moreover, our model accounts quantitatively for the large difference in the orientation of IC 4214 as derived in our first paper with photometric and kinematic methods.

An Optical, Near-Infrared, and Kinematic Study of Four Early-Type Resonance Ring Galaxies

?????We present optical and near-infrared surface photometry of four early-type galaxies considered to have resonance ring phenomena on the basis of morphology. We also present kinematics and rotation curves for three of the galaxies. The four galaxies are exceptional examples of resonance ring galaxies, and from these observations we derive the characteristic light distributions, the colors of the rings, and the near-infrared disk mass-to-light ratios. We also deproject the galaxies to examine intrinsic ring shapes and bar/ring alignments. From models of the rotation curves, we compute the Lindblad precession frequencies to examine resonance locations in the disks of the galaxies. Under the assumption that the outer rings and pseudorings seen in these galaxies are linked to the outer Lindblad resonance, we find that the inner rings of the sample galaxies lie near the inner 4:1 resonance and that the sharp ends of the bars lie on average at only 0.65 times the predicted radius of corotation.

Dynamics of Ringed Barred Spiral Galaxies. I. Surface Photometry and Kinematics of NGC 1433 and NGC 6300

This paper presents new near-infrared images and surface photometry and Hα 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 presented 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 presence of strong rings and pseudorings in the two galaxies allows the possibility to link specific orbital resonances with the observed rings. The new data allow us to derive a fairly complete composite rotation 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 finding that the radial velocity of the Seyfert nucleus in NGC 6300 differs from the actual systemic velocity of the galaxy by nearly 100 km s-1. We demonstrate in this paper that the offset is not an artifact of significant extinction in the inner regions of the galaxy.

The Structure and Dynamics of the Early-Type Resonance Ring Galaxy IC 4214. I. Observations

The southern galaxy IC 4214 is a bright, nearby example of a multiple ring early-type spiral galaxy with a weak bar. The galaxy shows three strong pseudoring features, including a nuclear ring, an inner ring, and a prominent R outer ring, each with distinctive characteristics. The galaxy is important because it is a classic resonance ring galaxy where the ring features can be linked to specific orbital resonances with the bar. We present in this paper a detailed UBVIH study of its photometric structure and a Fabry-Perot study of its kinematics to set the stage for a dynamical model in a separate paper. Despite the early Hubble type, ionized gas is well distributed in the inner disk regions, providing a well-sampled velocity field. Rapid rotation is found in the vicinity of the nuclear ring, where the rotation curve reaches a maximum, and the rotation velocities drop off somewhat with increasing radius in the outer regions. Noncircular motions are clearly seen in the observed velocity field. Analysis of both the velocity field and the shapes of isophotes give discrepant values for the inclination of the system, ranging from 47° to 50° from photometry to 55° to 58° from kinematics. A likely value of the inclination could be 52° if the inner and outer rings are intrinsically elongated and aligned perpendicular to each other.

The leading arm, ringed spiral galaxy NGC 4622 : a diagnostic case of a retrograde tidal encounter

The southern galaxy NGC 4622 is a rare example of a spiral with two sets of spiral arms winding in opposite senses : a single inner arm which opens counterclockwise, and two outer arms which open clockwise. The two sets of arms are linked by a nearly circular, off-centered inner ring of high contrast, and the presence of the two opposing senses means that NGC 4622 has at least one leading spiral arm, a phenomenon that up until now has never been firmly established in any galaxy. Here, some of the basic morphologic and photometric properties of this galaxy, which has recently been suggested to have experienced a retrograde tidal encounter, are described

A [ITAL]HUBBLE SPACE TELESCOPE[/ITAL][ITAL]Hubble Space Telescope[/ITAL] Optical and Ground-based Near-Infrared Study of the Giant Nuclear Ring in ESO 565-11

We present multiband Wide Field Planetary Camera 2 images of the central regions of ESO 565-11, a peculiar southern barred galaxy recently shown to have the largest known example of a circumnuclear starburst ring. We also present ground-based near-infrared H-band imaging and photometry of the galaxy. The results provide an interesting picture of the star-forming ring and its environment. Dust connected with the nuclear ring lies mainly in a symmetric two-armed spiral pattern. More than 700 point sources, mostly unresolved clusters, lie on a highly elliptical ring whose major axis is rotated by more than 20° from that of the isophotes of the background starlight. The luminosity function of these clusters follows a power law with slope a = -2.18 ± 0.06, typical of young cluster systems. Most of the clusters lie in the age range 4–6 Myr, and most may be metal-rich compared with the Sun. The nuclear ring is still clearly seen in the H band, revealing a knotty appearance indicating that young stars continue to have a significant impact on its brightness in this passband. Numerical simulations are used to show that the nuclear ring of ESO 565-11 has likely formed between two allowed inner Lindblad resonances with the relatively weak primary bar. The results indicate that the excessive size of the ring may be due to an extended hump in the variation of the parameter Ω - κ/2 with radius. The extreme elongation of the ring and its misalignment with the bar may indicate that it is in an early phase of development. At later times, the simulations suggest that the ring could evolve to a rounder shape. The models do not account for star formation or gas recycling.

A Hubble Space Telescope Optical and Ground-based Near-Infrared Study of the Giant Nuclear Ring in ESO 565-11*

We present multiband Wide Field Planetary Camera 2 images of the central regions of ESO 565-11, a peculiar southern barred galaxy recently shown to have the largest known example of a circumnuclear starburst ring. We also present ground-based near-infrared H-band imaging and photometry of the galaxy. The results provide an interesting picture of the star-forming ring and its environment. Dust connected with the nuclear ring lies mainly in a symmetric two-armed spiral pattern. More than 700 point sources, mostly unresolved clusters, lie on a highly elliptical ring whose major axis is rotated by more than 20° from that of the isophotes of the background starlight. The luminosity function of these clusters follows a power law with slope a = -2.18 ± 0.06, typical of young cluster systems. Most of the clusters lie in the age range 4–6 Myr, and most may be metal-rich compared with the Sun. The nuclear ring is still clearly seen in the H band, revealing a knotty appearance indicating that young stars continue to have a significant impact on its brightness in this passband. Numerical simulations are used to show that the nuclear ring of ESO 565-11 has likely formed between two allowed inner Lindblad resonances with the relatively weak primary bar. The results indicate that the excessive size of the ring may be due to an extended hump in the variation of the parameter Ω - κ/2 with radius. The extreme elongation of the ring and its misalignment with the bar may indicate that it is in an early phase of development. At later times, the simulations suggest that the ring could evolve to a rounder shape. The models do not account for star formation or gas recycling.

A Hubble SpaceTelescope Optical and Ground-basedNear-Infrared Studyof the Giant Nuclear Ring inESO 565-11*

We present multiband Wide Field Planetary Camera 2 images of the central regions of ESO 565-11, a peculiar southern barred galaxy recently shown to have the largest known example of a circumnuclear starburst ring. We also present ground-based near-infrared H-band imaging and photometry of the galaxy. The results provide an interesting picture of the star-forming ring and its environment. Dust connected with the nuclear ring lies mainly in a symmetric two-armed spiral pattern. More than 700 point sources, mostly unresolved clusters, lie on a highly elliptical ring whose major axis is rotated by more than 20° from that of the isophotes of the background starlight. The luminosity function of these clusters follows a power law with slope a = -2.18 ± 0.06, typical of young cluster systems. Most of the clusters lie in the age range 4–6 Myr, and most may be metal-rich compared with the Sun. The nuclear ring is still clearly seen in the H band, revealing a knotty appearance indicating that young stars continue to have a significant impact on its brightness in this passband. Numerical simulations are used to show that the nuclear ring of ESO 565-11 has likely formed between two allowed inner Lindblad resonances with the relatively weak primary bar. The results indicate that the excessive size of the ring may be due to an extended hump in the variation of the parameter Ω - κ/2 with radius. The extreme elongation of the ring and its misalignment with the bar may indicate that it is in an early phase of development. At later times, the simulations suggest that the ring could evolve to a rounder shape. The models do not account for star formation or gas recycling.