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Recently, Buta etal. (2009) examined the question "Do Bars Drive Spiral Density Waves?", an idea supported by theoretical studies and also from a preliminary observational analysis Block etal (2004). They estimated maximum bar strengths Q_b, maximum spiral strengths Q_s, and maximum m=2 arm contrasts A_2s for 23 galaxies with deep AAT K_s-band images. These were combined with previously published Q_b and Q_s values for 147 galaxies from the OSUBSGS sample and with the 12 galaxies from Block etal(2004). Weak correlation between Q_b and Q_s was confirmed for the combined sample, whereas the AAT subset alone showed no significant correlations between Q_b and Q_s, nor between Q_b and A_2s. A similar negative result was obtained in Durbala etal. (2009) for 46 galaxies. Based on these studies, the answer to the above question remains uncertain. Here we use a novel approach, and show that although the correlation between the maximum bar and spiral parameters is weak, these parameters do correlate when compared locally. For the OSUBSGS sample a statistically significant correlation is found between the local spiral amplitude, and the forcing due to the bar's potential at the same distance, out to 1.6 bar radii (the typical bar perturbation is then of the order of a few percent). Also for the sample of 23 AAT galaxies we find a significant correlation between local parameters out to 1.4 bar radii. Our new results confirm that, at least in a statistical sense, bars do indeed drive spiral density waves., Comment: Accepted to ApJL

The origin of S0 galaxies is discussed in the framework of early mergers in a Cold Dark Matter cosmology, and in a scenario where S0s are assumed to be former spirals stripped of gas. From an analysis of 127 early-type disk galaxies (S0-Sa), we find a clear correlation between the scale parameters of the bulge (r_eff) and the disk (h_R), a correlation which is difficult to explain if these galaxies were formed in mergers of disk galaxies. However, the stripping hypothesis, including quiescent star formation, is not sufficient to explain the origin of S0s either, because it is not compatible with our finding that S0s have a significantly smaller fraction of bars (46$\pm$6 %) than their assumed progenitors, S0/a galaxies (93$\pm$5 %) or spirals (64-69 %). Our conclusion is that even if a large majority of S0s were descendants of spiral galaxies, bars and ovals must play an important role in their evolution. The smaller fraction particularly of strong bars in S0 galaxies is compensated by a larger fraction of ovals/lenses (97$\pm$2 % compared to 82-83 % in spirals), many of which might be weakened bars. We also found massive disk-like bulges in nine of the S0 galaxies, bulges which might have formed at an early gas-rich stage of galaxy evolution., 12 pages, include 4 .eps figures, Accepted to ApJL

NGC 6782 is an early-type barred spiral galaxy exhibiting a rich and complex morphology with multiple ring patterns. To provide a physical understanding of its structure and kinematical properties, two-dimensional hydrodynamical simulations have been carried out. Numerical calculations reveal that the striking features in NGC 6782 can be reproduced provided that the gas flow is governed by the gravitational potential associated with a slowly rotating strong bar. In particular, the response of the gaseous disk to the bar potential leads to the excitation of spiral density waves at the inner Lindblad resonance giving rise to the appearance of a nearly circular nuclear ring with a pair of dust lanes. For a sufficiently strong bar potential, the inner 4:1 spiral density waves are also excited. The interaction of the higher harmonic waves with the waves excited at the inner Lindblad resonance and confined by the outer Lindblad resonance results in the observed diamond-shaped (or pointy oval) inner ring structure. The overall gas morphology and kinematical features are both well reproduced by the model provided that the pattern speed of the bar is $\sim 25$ km s$^{-1}$ kpc$^{-1}$., Comment: 35 pages, 14 figures

K_s-band images of 20 barred galaxies show an increase in the peak amplitude of the normalized m=2 Fourier component with the R_25-normalized radius at this peak. This implies that longer bars have higher $m=2$ amplitudes. The long bars also correlate with an increased density in the central parts of the disks, as measured by the luminosity inside 0.25R_25 divided by the cube of this radius in kpc. Because denser galaxies evolve faster, these correlations suggest that bars grow in length and amplitude over a Hubble time with the fastest evolution occurring in the densest galaxies. All but three of the sample have early-type flat bars; there is no clear correlation between the correlated quantities and the Hubble type., Comment: ApJ Letters, 670, L97, preprint is 7 pages, 4 figures

The southern S0+ galaxy NGC 7020 presents an unusual morphology: it includes a very regular outer ring which is completely detached and which envelops an inner ring/lens zone with an exotic hexagonal shape. The ring has a high contrast compared with those usually observed in barred galaxies, yet NGC 7020 is not obviously barred. In this paper, the structure of this galaxy is studied by means of UBVRI CCD surface photometry. The photometry reveals a complex system and shows that most of the recent star formation in the galaxy has taken place in the outer ring. Two bright knots are found on the major axis of the hexagonal zone that appear to be true enhancements of old stars rather than young associations. Between these knots and the bulge there are dips in the surface brightness and a clear zone of rectangular isophotes. 56 refs.

Four extreme examples illustrate the diverging characteristics of bright galactic rings. The galaxies are studied by means of multicolor CCD surface photometry. The ringed Seyfert galaxy NGC 3081 is an S0/a system possessing an unusually high contrast inner ring enveloping a weak bar. The structure of this galaxy is described using BVR(C)I(C) surface photometry. The observations reveal a complex system which shares many properties in common with NGC 1433, a prototype SB(r) type spiral with a strong bar. Significant azimuthal variations in the color indices occur around the ring which are probably due to the elongated shape. It is suggested that while many properties of the three rings in this galaxy can be explained in terms of orbit resonance theory, the extreme shape of the inner ring and the weakness of the bar are contradictions to the theory that need to be addressed. It is suggested that NGC 3081 is a possible example of an object where secular dissolution of the bar is occurring. 60 refs.

The extragalactic distance scale derived in previous papers of this series from the diameters of inner ring structures (r) in galaxies is applied to the determination of the distances of six groups and clusters, and one supercluster, in the distance range 10< or =..delta..< or =112 Mpc. The clusters are well distributed on the sky and are used to derive a value of the Hubble constant free of the perturbing effects of the Local Supercluster. Several definitions of the Hubble ratio, for bound and unbound systems, and several frames of reference are introduced and used. Radial velocities V/sub c/ corrected for solar motion in a frame of reference defined by the nearby galaxies (2< or =..delta..< or =32 Mpc) are shown to yield a Hubble ratio which is substantially independent of direction. An analysis of four bound groups and one unbound grouping in the distance interval 10< or =..delta..< or =16 Mpc yields a mean Hubble ratio H/sub c/ = 92 +- 4 (internal m.e.) km s/sup -1/ Mpc/sup -1/. A similar analysis of two more distant bound systems, the IC 4329 Group at ..delta.. = 45 Mpc and the Hercules Supercluster at ..delta.. = 112 Mpc, yields H/sub c/more » = 96 +- 5, or 93 +- 5 when plausible cosmological corrections are considered. The constancy of the Hubble ratio over the distance range 10< or =..delta..< or =112 Mpc gives no support to nonlinear concepts of the redshift-distance relation and demonstrates the absence of Malmquist bias in the ..mu../sub 0/(r) scale. The value of the Hubble constant derived from the rings over this range is H/sub 0/ = 93 +- 4 (internal m.e.) km s/sup -1/ Mpc/sup -1/ and +- 10 (external m.e.) when the zero point error of our tertiary indicators is included.« less

A high quality optical spectrum of the 1981 Type I supernova in NGC 4536 at maximum light is well represented by a synthetic consisting of resonance scattering lines of Ca II, Si II, S II, Mg II, and O I, superposed on a continuum. The assumption of LTE at the photosphere leads to relative abundnces of Ca, Si, S, Mg, and O that are consistent with solar abundances for a range of continuum temperatures. The spectrum is inconsistent with models such as the ''double-detonation'' model in which material with v = (12--15) x 10/sup 3/ km s/sup -1/ is burned completely to Ni/sup 56/.