Related papers: The Relation Between Activity and Environment in C…
Compact groups (CGs) of galaxies appear to be the densest galaxy systems containing a few luminous galaxies in close proximity to each other, which have a typical size of a few tens kilopacsec in observation. On the other hand, in the…
We study the relationship between the structure and star-formation rate (SFR) of X-ray selected low and moderate luminosity active galactic nuclei (AGNs) in the two Chandra Deep Fields, using Hubble Space Telescope imaging from the Cosmic…
We present optical spectroscopic observations of 93 galaxies taken from the infra-red selected COLA (Compact Objects in Low Power AGN) sample. The sample spans the range of far-IR luminosities from normal galaxies to LIRGs. Of the galaxies…
The incidence and properties of Active Galactic Nuclei (AGN) in the field, groups, and clusters can provide new information about how these objects are triggered and fueled, similar to how these environments have been employed to study…
Close encounters between galaxies are expected to be a viable mechanism, as predicted by numerical simulations, by which accretion onto supermassive black holes can be initiated. To test this scenario, we construct a sample of 562 galaxies…
We study the star-formation activity in a sample of $\sim$ 56,000 brightest cluster galaxies (BCGs) at $0.05 < z < 0.42$ using optical and infra-red data from SDSS and WISE. We estimate stellar masses and star-formation rates (SFR) through…
In this study we investigate 89 radio galaxies that are spectroscopically-confirmed to be members of five large scale structures in the redshift range of $0.65 \le z \le 0.96$. Based on a two-stage classification scheme, the radio galaxies…
We present the results of the study of the Star Formation Rates (SFRs) of a sample of disk galaxies in nearby compact groups compared with the SFRs of a sample of field galaxies. For this purpose, H$\alpha$ luminosities and equivalent…
We use an updated version of the halo-based galaxy group catalog of Yang et al., and take the surface brightness of the galaxy group ($\mu_{\rm lim}$) based on projected positions and luminosities of galaxy members as a compactness proxy to…
We analyzed a sample of $\sim$113,000 galaxies ($\rm z < 0.3$) from the Sloan Digital Sky Survey, divided into star-forming, composite, Seyfert, and LINER types, to explore the relationships between UV-to-optical colors ($\rm u-r$), star…
We use a complete sample of galaxies drawn from the SDSS to study how structure, star formation and nuclear activity depend on local density and on stellar mass. Local density is estimated by counting galaxies above a fixed absolute…
Recent studies have indicated that the HCN-to-CO(J=1-0) and HCO+-to-HCN(J=1-0) ratios are significantly different between galaxies with AGN (active galactic nucleus) and SB (starburst) signatures. In order to study the molecular gas…
Redshift Survey Compact Groups (RSCGs) are tight knots of N >= 3 galaxies selected from the CfA2+SSRS2 redshift survey. The selection is based on physical extent and association in redshift space alone. We measured 300 new redshifts of…
The very high apparent galaxy densities in Hickson compact groups (HCGs) should produce copious amounts of galaxy-galaxy interaction, if these groups are bound dynamical units. I examine the evidence for such interactions in HCG 94, a group…
Compact galaxy groups are at the extremes of the group environment, with high number densities and low velocity dispersions that likely affect member galaxy evolution. To explore the impact of this environment in detail, we examine the…
We have completed a spectroscopic survey of X-ray point sources in eight low-redshift clusters of galaxies (0.05<z<0.31) and have identified 40 cluster members with broad-band (0.3-8 keV) X-ray luminosities between L_X = 8x10^{40} and…
We identify compact groups of galaxies (CGs) within mock galaxy catalogues from the Millennium Simulation at z=0 with three semi-analytic models (SAMs) of galaxy formation. CGs are identified using the same 2D criteria as those visually…
We use a volume-limited galaxy sample from the SDSS Data Release 7 to explore the dependence of galactic conformity on the large-scale environment, measured on $\sim$ 4 Mpc scales. We find that the star formation activity of neighbour…
This is the first paper of a series on the investigation of stellar population properties and galaxy evolution of an observationally homogeneous sample of early-type galaxies in groups, field and isolated galaxies. We present high S/N…
Hickson Compact Groups (HCGs) constitute an interesting extreme in the range of environments in which galaxies are located, as the space density of galaxies in these small groups are otherwise only found in the centres of much larger…