The Environments of Local Luminous Infrared Galaxies: Star Formation Rates increase with Density

TL;DR

This study reveals that local luminous infrared galaxies (LIRGs) are found in denser environments and have higher star formation rates with increasing density, suggesting a link between environment and star formation activity.

Contribution

It demonstrates a strong correlation between environment density and IR luminosity in local LIRGs, highlighting a transition point at L_IR=10^11 h^-2 L_sun and comparing their properties to high-redshift galaxies.

Findings

LIRGs reside in denser environments than non-LIRG IR galaxies.

Star formation rates in LIRGs increase with local density.

LIRGs may be survivors or products of processes active at z~1.

Abstract

This work studies the environments and star formation relationships of local luminous infrared galaxies (LIRG) in comparison to other types of local and distant (z~1) galaxies. The infrared (IR) galaxies are drawn from the IRAS sample. The density of the environment is quantified using 6dF and Point Source Catalogue redshift survey (PSCz) galaxies in a cylinder of 2h^-1 Mpc radius and 10h^-1 Mpc length. Our most important result shows the existence of a dramatic density difference between local LIRGs and local non-LIRG IR galaxies. LIRGs live in denser environments than non-LIRG IR galaxies implying that L_IR=10^11 h^-2 L_sun marks an important transition point among IR-selected local galaxies. We also find that there is a strong correlation between the densities around LIRGs and their L_IR luminosity, while the IR-activity of non-LIRG IR galaxies does not show any dependence on environment. This trend is independent of mass-bin selection. The SF-density trend in local LIRGs is similar to that found in some studies of blue cloud galaxies at z~1 which show a correlation between star formation and local density (the reversal of the relation seen for local galaxies). This, together with the rapid decline of the number count of LIRGs since z~1, could mean that local LIRGs are survivors of whatever process transformed blue cloud galaxies at z~1 to the present day or local LIRGs came into existence by similar process than high redshift LIRGs but at later stage.