On the Shapes and Structures of High-Redshift Compact Galaxies

TL;DR

This study compares the shapes of high-redshift compact galaxies to local galaxies, finding they do not closely resemble any single local galaxy type, suggesting they may be a unique or mixed class.

Contribution

It provides a detailed comparison of high-redshift compact galaxies' structures with local galaxy populations, challenging previous assumptions about their morphology.

Findings

High-redshift galaxies have ellipticity distributions similar to local early-type galaxies.

Their Sersic index distribution resembles local disk-dominated galaxies.

High-redshift compact galaxies likely do not match any single local galaxy population.

Abstract

Recent deep Hubble Space Telescope WFC3 imaging suggests that a majority of compact quiescent massive galaxies at z~2 may contain disks. To investigate this claim, we have compared the ellipticity distribution of 31 carefully selected high-redshift massive quiescent compact galaxies to a set of mass-selected ellipticity and Sersic index distributions obtained from 2D structural fits to ~40,000$ nearby galaxies from the Sloan Digital Sky Survey. A Kolmogorov-Smirnov test shows that the distribution of ellipticities for the high-redshift galaxies is consistent with the ellipticity distribution of a similarly chosen sample of massive early-type galaxies. However the distribution of Sersic indices for the high-redshift sample is inconsistent with that of local early-type galaxies, and instead resembles that of local disk-dominated populations. The mismatch between the properties of high-redshift compact galaxies and those of both local early-type and disk-dominated systems leads us to conclude that the basic structures of high-redshift compact galaxies probably do not closely resemble those of any single local galaxy population. Any galaxy population analog to the high-redshift compact galaxies that exists at the current epoch is either a mix of different types of galaxies, or possibly a unique class of objects on their own.