What size halos do local LIRGs live in?

TL;DR

This study analyzes the environments of local LIRGs, revealing they predominantly reside in group-sized halos and that their IR luminosity correlates with proximity to halo centers, independent of halo mass.

Contribution

It provides new insights into the preferred dark matter halo environments of local LIRGs using a novel association technique.

Findings

LIRGs are most common in halos of about 10^13 solar masses.

High IR luminosity LIRGs are closer to halo centers.

LIRG environment preference confirmed using a different method.

Abstract

This work investigates the preferred environment of local Luminous IR Galaxies (LIRGs) in terms of the host halos that they inhabit, and in comparison to a control galaxy sample. The LIRGs are drawn from the IRAS Point Source Catalogue redshift survey (PSCz), while the control sample is drawn from the 2MASS redshift survey (2MRS). A friends-of-friends algorithm was run on the 2MRS sample to identify galaxies living in the same dark matter halos and the PSCz galaxies were then associated with these identified halos. We show that the relative probability of finding local LIRGs with respect to 2MASS galaxies is largest in approximately group size halos (Mhalo~10^13M_sun), and declines both in the cluster regime and in smaller halos. This confirms, using a different technique than in previous work, that local LIRGs are indeed more abundant in group environments than elsewhere. We also find a trend between the LIR values of LIRGs and their location within their host dark matter halos, such that the average location of LIRGs with high IR luminosity is closer to the halo centre than for low IR luminosity galaxies. Moreover, this trend does not seem to depend on halo mass.