Compact E+A Galaxies as a Progenitor of Massive Compact Quiescent Galaxies at 0.2<z< 0.8

TL;DR

This study identifies and analyzes compact E+A galaxies at 0.2<z<0.8, proposing they are a key progenitor population for the formation of massive compact quiescent galaxies, based on spectral, size, and age data.

Contribution

It provides a new catalog of compact E+A galaxies and links their properties to the formation of massive compact quiescent galaxies at intermediate redshifts.

Findings

Compact E+A galaxies have stellar ages <1 Gyr.

They are likely progenitors of massive compact quiescent galaxies.

The number density of compact E+A galaxies can account for a significant fraction of the population at 0.2<z<0.8.

Abstract

We search the Sloan Digital Sky Survey and the Baryon Oscillation Sky Survey to identify ~5500 massive compact quiescent galaxy candidates at 0.2<z<0.8. We robustly classify a subsample of 438 E+A galaxies based on their spectral properties and make this catalog publicly available. We examine sizes, stellar population ages and kinematics of galaxies in the sample and show that the physical properties of compact E+A galaxies suggest that they are a progenitor of massive compact quiescent galaxies. Thus, two classes of objects-compact E+A and compact quiescent galaxies-may be linked by a common formation scenario. The typical stellar population age of compact E+A galaxies is <1 Gyr. The existence of compact E+A galaxies with young stellar populations at 0.2<z<0.8 means that some compact quiescent galaxies first appear at intermediate redshifts. We derive a lower limit for the number density of compact E+A galaxies. Assuming passive evolution, we convert this number density into an appearance rate of new compact quiescent galaxies at 0.2<z<0.8. The lower limit number density of compact quiescent galaxies which may appear at z<0.8 is comparable to the lower limit of the total number density of compact quiescent galaxies at these intermediate redshifts. Thus, a substantial fraction of the z<0.8 massive compact quiescent galaxy population may descend from compact E+A galaxies at intermediate redshifts.