Morphological Evolution of the Hosts of Far-Infrared/Submillimeter Galaxies

TL;DR

This study analyzes the morphological evolution of far-infrared and submillimeter galaxy hosts across redshifts, revealing a transition from irregular/interacting to disk galaxies around z≈1.25, indicating changing galaxy formation mechanisms.

Contribution

It provides a detailed morphological analysis of a large sample of FIRGs and SMGs, highlighting a redshift-dependent transition in host galaxy types and insights into galaxy evolution processes.

Findings

Most FIRG/SMG hosts are disk or irregular/interacting galaxies.

A morphological transition occurs at z≈1.25, with irregular/interacting dominating above and disks below.

The transition suggests a shift from merger-driven to secular galaxy growth.

Abstract

We present a host morphological study of 1266 far-infrared galaxies (FIRGs) and submillimeter galaxies (SMGs) in the Cosmic Evolution Survey field using the F160W and F814W images obtained by the Hubble Space Telescope. The FIRGs and SMGs are selected from the Herschel Multi-tiered Extragalactic Survey and the SCUBA-2 Cosmology Legacy Survey, respectively. Their precise locations are based on the interferometry data from the Atacama Large Millimeter/submillimeter Array and the Very Large Array. These objects are mostly at $0.1\lesssim z\lesssim 3$. The SMGs can be regarded as the population at the high-redshift tail of the FIRGs. Most of our FIRGs/SMGs have a total infrared luminosity ($L_{\rm IR}$) in the regimes of luminous and ultraluminous infrared galaxies (LIRGs, $L_{\rm IR} = 10^{11-12}L_\odot$; ULIRGs, $L_{\rm IR}>10^{12}L_\odot$). The hosts of the SMG ULIRGs, FIRG ULIRGs, and FIRG LIRGs are of sufficient numbers to allow for detailed analysis, and they are only modestly different in their stellar masses. Their morphological types are predominantly disk galaxies (type D) and irregular/interacting systems (type Irr/Int). There is a morphological transition at $z\approx 1.25$ for the FIRG ULIRG hosts, above which the Irr/Int galaxies dominate and below which the D and Irr/Int galaxies have nearly the same contributions. The SMG ULIRG hosts seem to experience a similar transition. This suggests a shift in the relative importance of galaxy mergers/interactions versus secular gas accretions in "normal" disk galaxies as the possible triggering mechanisms of ULIRGs. The FIRG LIRG hosts are predominantly D galaxies over $z=$ 0.25--1.25, where they are of sufficient statistics.