The identification of post-starburst galaxies at z~1 using multiwavelength photometry: a spectroscopic verification

TL;DR

This paper develops and verifies a photometric technique to identify post-starburst galaxies at high redshift, enabling large-scale studies of galaxy evolution during the Universe's early epochs.

Contribution

The study introduces a new multiwavelength photometric method using spectral shape parameters to efficiently select post-starburst galaxies at z~1, validated by spectroscopic confirmation.

Findings

Over 900 candidate post-starbursts identified in UDS survey

Approximately 80% of spectroscopically observed candidates confirmed as post-starburst

Photometric selection effectively finds recently-quenched galaxies at high redshift

Abstract

Despite decades of study, we still do not fully understand why some massive galaxies abruptly switch off their star formation in the early Universe, and what causes their rapid transition to the red sequence. Post-starburst galaxies provide a rare opportunity to study this transition phase, but few have currently been spectroscopically identified at high redshift ($z>1$). In this paper we present the spectroscopic verification of a new photometric technique to identify post-starbursts in high-redshift surveys. The method classifies the broad-band optical-near--infrared spectral energy distributions (SEDs) of galaxies using three spectral shape parameters (super-colours), derived from a principal component analysis of model SEDs. When applied to the multiwavelength photometric data in the UKIDSS Ultra Deep Survey (UDS), this technique identified over 900 candidate post-starbursts at redshifts $0.5<z<2.0$. In this study we present deep optical spectroscopy for a subset of these galaxies, in order to confirm their post-starburst nature. Where a spectroscopic assessment was possible, we find the majority (19/24 galaxies; ~80 per cent) exhibit the strong Balmer absorption (H $\delta$ equivalent width $W_{\lambda}$ >5 Ang.) and Balmer break, characteristic of post-starburst galaxies. We conclude that photometric methods can be used to select large samples of recently-quenched galaxies in the distant Universe.