Structural and morphological properties of ultraluminous infrared galaxies at $1<z<3$

TL;DR

This study uses HST/WFC3 imaging to analyze the morphology of 502 ultraluminous infrared galaxies at redshifts 1 to 3, revealing diverse structures and formation processes including mergers and disk instabilities.

Contribution

It provides a detailed morphological classification of high-redshift ULIRGs and investigates their size evolution, highlighting the roles of mergers and disk instabilities in their formation.

Findings

High-redshift ULIRGs are a mix of mergers, irregulars, disks, and ellipticals.

Most ULIRGs are merging systems or late-type galaxies with specific morphological parameters.

ULIRG sizes decrease with redshift following a power-law relation.

Abstract

Using the Hubble Space Telescope (HST)/Wide Field Camera 3 (WFC3) near-infrared high-resolution imaging from the 3D-HST survey, we analyze the morphology and structure of 502 ultraluminous infrared galaxies (ULIRGs; $L_{\rm IR}>10^{12}L_{\odot}$) at $1<z<3$. Their rest-frame optical morphologies show that high-redshift ULIRGs are a mixture of mergers or interacting systems, irregular galaxies, disks, and ellipticals. Most of ULIRGs in our sample can be roughly divided into merging systems and late-type galaxies (Sb$-$Ir), with relatively high $M_{20}$ ($>-1.7$) and small S\'{e}rsic index ($n<2.5$), while others are elliptical-like (E/S0/Sa) morphologies with lower $M_{20}$ ($<-1.7$) and larger $n$ ($>2.5$). The morphological diversities of ULIRGs suggest that there are different formation processes for these galaxies. Merger processes between galaxies and disk instabilities play an important role in the formation and evolution of ULIRGs at high redshift. In the meantime, we also find that the evolution of the size ($r_{\rm e}$) with redshift of ULIRGs at redshift $z\sim1-3$ follows $r_{\rm e}\propto(1+z)^{-(0.96\pm0.23)}$.