Related papers: Compact groups in theory and practice - I. The spa…
Galaxy groups and clusters are the most massive collapsed structures in the Universe. Those structures are formed by collapsing with other smaller structures. Groups and cluster mergers provide an appropriate environment for the evolution…
In two recent papers, we developed a powerful technique to link the distribution of galaxies to that of dark matter haloes by considering halo occupation numbers as function of galaxy luminosity and type. In this paper we use these…
We examine the possibility that galactic halos are collisionless ensembles of scalar field ``massive compact halo objects'' (MACHOs). Using mass constraints from MACHO microlensing and from theoretical arguments on halos made up of massive…
This paper presents the results of a pilot redshift survey of 18 candidate compact groups from the distant DPOSS survey that extends the available surveys of compact groups of galaxies to z ~0.2 in redshift, mainly Hickson Compact Groups…
In cold dark matter cosmological models, structures form and grow by merging of smaller units. Numerical simulations have shown that such merging is incomplete; the inner cores of halos survive and orbit as "subhalos" within their hosts.…
We investigate the atomic gas (HI) content of galaxies in groups using early data from the FAST All Sky HI survey (FASHI). Taking advantage of FAST's blind, wide-area coverage and uniform sensitivity, we assemble a sample of $230$ group…
We use the Millennium Galaxy Catalogue (MGC) to study the effect of compact galaxies on the local field galaxy luminosity function. Here we observationally define as `compact' galaxies that are too small to be reliably distinguished from…
Our Galaxy, Andromeda and their companion dwarf galaxies form the Local Group. Most of the mass in and around it is believed to be dark matter rather than gas or stars, so its distribution must be inferred from the effect of gravity on the…
Observations show that galaxies in galaxy clusters are strongly influenced by their environment. There is growing evidence that some galaxies in groups show similar properties to galaxies in clusters, such as redder colours and gas…
We present an all-sky catalogue of 395 nearby galaxy groups revealed in the Local Supercluster and its surroundings. The groups and their associations are identified among 10914 galaxies at |b|>15deg with radial velocities VLG<3500 km/s.…
Collisionless particles, such as cold dark matter, interact only by gravity and do not have any associated length scale, therefore the dark halos of galaxies should have negligible core radii. This expectation has been supported by…
We present the Complete Local-Volume Groups Sample (CLoGS), a statistically complete optically-selected sample of 53 groups within 80 Mpc. Our goal is to combine X-ray, radio and optical data to investigate the relationship between member…
We explore the properties of central galaxies living in voids using the EAGLE cosmological hydrodynamic simulations. Based on the minimum void-centric distance, we define four galaxy samples: inner void, outer void, wall, and skeleton. We…
The properties of substructure in galaxy clusters, exquisitely probed by gravitational lensing, offer a stringent test of dark matter (DM) models. Combining strong- and weak-lensing data for massive clusters, we map their total mass --…
Analyses of B and R band observations of four compact groups reveal the presence of a considerable amount of diffuse, intergalactic light in two of them (HCG 79 and HCG 95). The diffuse component is presumably due to stellar material that…
Galaxy groups likely to be virialized are identified within the CNOC2 intermediate redshift galaxy survey using an iterative method. The number-velocity dispersion relation is in agreement with the low-mass extrapolation of the cluster…
We investigate the clustering and dark matter halo mass for a sample of $\sim$16,000 central galaxies selected from the SDSS/DR7 group catalog. We select subsamples of central galaxies on three two-dimensional planes, each formed by stellar…
We consider the possibility that the dark matter in the halos of galaxies may be in the form of clusters of \macho s within which are embedded cold, dense gas clouds. Microlensing experiments have found evidence that the Galactic halo…
Combining our knowledge of halo structure and internal kinematics from cosmological dark matter simulations and the distribution of halo interlopers in projected phase space measured in cosmological galaxy simulations, we develop MAGGIE, a…
We find that the fraction of early-type galaxies in poor groups (containing from 4 to 10 members) is a weakly increasing function of the number of the group members and is about two times higher than in a sample of isolated galaxies. We…