We present a sample of 42 high-mass low-metallicity outliers from the mass–metallicity relation of star-forming galaxies. These galaxies have stellar masses that span log(M⋆/M⊙) ∼ 9.4 to 11.1 and are offset from the mass–metallicity relation by −0.3 to −0.85dex in 12+ log(O/H). In general, they are extremely blue, have high star formation rates for their masses, and are morphologically disturbe...

Using mid-IR and optical data, we deduce the total infrared (IR) luminosities of galaxies in the Coma cluster and present their infrared luminosity function (LF). The shape of the overall Coma IR LF does not show significant differences from the IR LFs of the general field, which indicates the general independence of global galaxy star formation on environment up to densities ∼ 40 times greater...

We consider the massive star formation properties, radial profiles, and atomic gas masses of those galaxies in our Hα Galaxy Survey that have close companion galaxies, in comparison with a matched control sample of galaxies without companions. Our analysis is based on Hα and continuum images of 327 disk galaxies that form a representative sample of the local Universe. We find that the presence ...

Recent morphological studies of QSO host galaxies by the Hubble Space Telescope (HST) have revealed that a sizable fraction of QSO host galaxies possess close small companion galaxies. It is however not clear why and how these companion galaxies are physically associated with the activation of QSO nucleus and the formation of QSO hosts. We here demonstrate that QSO companion galaxies are tidall...

We have used optical spectroscopy to investigate the active galaxy populations in a sample of 20 nearby Abell clusters. The targets were identified on the basis of 1.4 GHz radio emission, which identifies them as either AGN or galaxies forming stars at rates comparable to or greater than that of the Milky Way. The spectra were used to characterize the galaxies via their emission and absorption ...

From a sample of 50 predominantly inactive galaxies with direct supermassive black hole mass measurements, it has recently been established that barred galaxies tend to reside rightward of the Mbh-σ relation defined by non-barred galaxies. Either black holes in barred galaxies tend to be anaemic or the central velocity dispersions in these galaxies have a tendency to be elevated by the presence...

The energy fed by active galactic nuclei to the surrounding diffuse baryons changes the latter’s amount, temperature, and distribution; so in groups and in member galaxies it affects the X-ray luminosity and also the Sunyaev-Zel’dovich effect. Here we compute how the latter is enhanced by the transient blastwave driven by a shining quasar, and is depressed when the equilibrium is recovered with...

We examine the distribution of stellar masses of galaxies in MS 1054.4-0321 and CL 0152.7-1357, two X-ray-selected clusters of galaxies at z = 0.83. Our stellar mass estimates, from spectral energy distribution fitting, reproduce the dynamical masses as measured from velocity dispersions and halflight radii with a scatter of 0.2 dex in the mass for early-type galaxies. When we restrict our samp...

Using photometric and redshift data for the Virgo and Coma clusters, we present evidence for a correlation between the light concentration of elliptical galaxies (including dwarf ellipticals) and the local 3–D (i.e. non–projected) density of the clusters: more concentrated ellipticals are located in denser regions. The null hypothesis (i.e. the absence of any relation) is rejected at a signific...

The variation of the mass-to-light ratios M/L of early type galaxies as function of their luminosities L is investigated. It is shown that the tilt β = 0.27 (in the B–band) of the fundamental plane relation M/L ∝ L can be understood as a combination of two effects: about one-quarter (i.e. ∆β = 0.07) is a result of systematic variations of the stellar population properties with increasing lumino...