We have formed “composite spectra” by combining the integrated–light spectra of individual galaxies in 8 intermediate–redshift and 12 low–redshift clusters of galaxies. Because these composite spectra have much higher signal–to–noise ratios than individual galaxy spectra, they are particularly useful in quantifying general trends in star formation for galaxy populations in distant clusters, z >...

We present H-band (1.65μm) surface photometry of 57 galaxies drawn from the Local Sphere of Influence (LSI) with distances of less than 10 Mpc from the Milky Way. The images with a typical surface brightness limit 4 mag fainter than 2MASS (24.5 mag arcsec−2 < μlim < 26 mag arcsec−2 ) have been obtained with IRIS2 on the 3.9 m Anglo-Australian Telescope. A total of 22 galaxies that remained prev...

It is shown that the low-mass groups obey the Lx ∼ σ 4 v law deduced for galaxy clusters. The impression of the more shallow slope of the Lx − σv correlation for groups is created not by enhanced X-ray emission, but by underestimation of the radial velocity dispersion of some groups. Subject headings: galaxies: clusters : general – X-rays: galaxies

Tidal forces acting on galaxies in clusters lead to a strong dynamical evolution. In order to quantify the amount of evolution, I run self-consistent N-body simulations of disk galaxies for a variety of models in the hierarchically forming clusters. The tidal field along the galactic orbits is extracted from the simulations of cluster formation in the Ω0 = 1; Ω0 = 0.4; and Ω0 = 0.4, ΩΛ = 0.6 co...

We combine Spitzer 24 μm observations with data from the COMBO-17 survey for ∼15,000 0.2 < z ≤ 1 galaxies to determine how the average star formation rates (SFR) have evolved for galaxy sub-populations of different stellar masses. In the determination of we consider both the ultraviolet (UV) and the infrared (IR) luminosities, and account for the contributions of galaxies that are individ...

Stellar bars are important internal drivers of secular evolution in disk galaxies. Using a sample of nearby spiral galaxies with weak and strong bars, we explore the relationships between the star formation feature and stellar bars in galaxies. We find that galaxies with weak bars tend to be coincide with low concentrical star formation activity, while those with strong bars show a large scatte...

We reanalyze the galaxy-mass correlation function measured by the Sloan Digital Sky Survey to obtain host dark matter halo masses at galaxy and galaxy group scales. We extend the data to galaxy clusters in the 2MASS catalog and study the relation between central galaxy luminosity and halo mass. While the central galaxy luminosity scales as ∼ M0.7−0.8 at low masses, the relation flattens to ∼ M<...

We have studied the radio and far-infrared (FIR) emission from 114 galaxies in the 7 nearest clusters (< 100 Mpc) with prominent X-ray emission to investigate the impact of the cluster environment on the star formation and AGN activity in the member galaxies. The X-ray selection criterion is adopted to focus on the most massive and dynamically relaxed clusters. A large majority of cluster galax...

We report upper limits on the masses of black holes that can be present in the centers of sixteen nearby galaxy bulges. These limits Mlim BH for our statistically complete sample were derived from the modeling of the central emission-line widths ([N II] or [S II]), observed over a 0.′′25× 0.2 (R <∼ 9 pc) aperture. The experiment has a mean detection sensitivity of ∼ 3.9×106 M⊙. For three sample...

It has been established that virial masses for black holes in low-redshift active galaxies can be estimated from measurements of the optical continuum strength and the width of the broad Hβ line. Under various circumstances, however, both of these quantities can be challenging to measure or can be subject to large systematic uncertainties. To mitigate these difficulties, we present a new method...