The Occurrence of Compact Groups of Galaxies Through Cosmic Time

Abstract

We use the outputs of a semi-analytical model of galaxy formation run on the Millennium Simulation to investigate the prevalence of 3D compact groups (CGs) of galaxies from $z=11$ to 0. Our publicly available code identifies CGs using the 3D galaxy number density, the mass ratio of secondary+tertiary to the primary member, mass density in a surrounding shell, the relative velocities of candidate CG members, and a minimum CG membership of three. We adopt "default" values for the first three criteria, representing the observed population of Hickson CGs at $z=0$. The percentage of non-dwarf galaxies ($M>5\times 10^8{h}^{-1}{M}_{\odot }$) in CGs peaks near $z\sim 2$ for the default set, and between $z\sim 1-3$ for other parameter sets. This percentage declines rapidly at higher redshifts ($z\gtrsim 4$), consistent with the galaxy population as a whole being dominated by low-mass galaxies excluded from this analysis. According to the most liberal criteria, $\lesssim 3\%$ of non-dwarf galaxies are members of CGs at the redshift where the CG population peaks. Our default criteria result in a population of CGs at $z<0.03$ with number densities and sizes consistent with Hickson CGs. Tracking identified CG galaxies and merger products to $z=0$, we find that $\lesssim 16\%$ of non-dwarf galaxies have been CG members at some point in their history. Intriguingly, the great majority ($96\%$) of $z=2$ CGs have merged to a single galaxy by $z=0$. There is a discrepancy in the velocity dispersions of Millennium Simulation CGs compared to those in observed CGs, which remains unresolved.

Revised version to match published version. Uses likeapj.cls (v1.1.5), likeapj.bst style files, 11 pages, 7 figures, 1 table. Compact group detection code available at https://github.com/cdw9bf/CompactGroup ; LaTex style files available at https://github.com/qtast/likeapj/releases/latest ; Data acquisition code available at https://github.com/tvwenger/millennium-tap-query

References in corpus (17)

• Cosmic Star Formation History
• The hierarchical formation of the brightest cluster galaxies
• Compact groups in theory and practice - III. Compact groups of galaxies in the Sixth Data Release of the Sloan Digital Sky Survey
• The Infrared Properties of Hickson Compact Groups
• A Comparison of Galaxy Merger History Observations and Predictions from Semi-Analytic Models
• Compact Groups of Galaxies selected by stellar mass: The 2MASS Compact Group Catalogue
• Compact groups in theory and practice - I. The spatial properties of compact groups
• Where are compact groups in the local Universe?
• The H$\alpha$ kinematics of interacting galaxies in 12 compact groups
• Evolution of compact and fossil groups of galaxies from semi-analytical models of galaxy formation
• The role of molecular gas in galaxy transition in compact groups
• Hierarchical Formation in Action: Characterizing Accelerated Galaxy Evolution in Compact Groups Using Whole-Sky WISE Data
• Compact groups in theory and practice - II. Comparing the observed and predicted nature of galaxies in compact groups
• The Ultraviolet and Infrared Star Formation Rates of Compact Group Galaxies: An Expanded Sample
• On the properties of compact groups identified in different photometric bands
• Comparing galaxy populations in compact and loose groups of galaxies III. Effects of environment on star formation
• Cosmic Pathways for Compact Groups in the Milli-Millennium Simulation

Cited by in corpus (4)

• A Complex Multiphase DLA Associated with a Compact Group at z=2.431 Traces Accretion, Outflows, and Tidal Streams
• Compact groups from semi-analytical models of galaxy formation -- III: purity and completeness of Hickson-like catalogues
• Compact groups from semi-analytical models of galaxy formation -- II: Different assembly channels
• Compact Groups in GDM Cosmological Simulations