SQuIGG E Survey: Massive z ∼ 0.6 Post-starburst Galaxies Exhibit Flat Age Gradients

Abstract

We present Gemini Multi-Object Spectrograph (GMOS) integral field unit (IFU) observations of six massive ( M ⋆  ≥ 10 11 M ⊙ ) A-star dominated post-starburst galaxies at z  ∼ 0.6. These galaxies are a subsample of the  Survey, which selects intermediate-redshift post-starbursts from the Sloan Digital Sky Survey spectroscopic sample (DR14) with spectral shapes that indicate they have recently shut off their primary epoch of star formation. Using Hδ A absorption as a proxy for stellar age, we constrain five of the galaxies to have young (∼600 Myr) light-weighted ages at all radii and find that the sample on average has flat age gradients. We examine the spatial distribution of mass-weighted properties by fitting our profiles with a toy model including a young, centrally concentrated burst superimposed on an older, extended population. We find that galaxies with flat Hδ A profiles are inconsistent with formation via a central secondary starburst. This implies that the mechanism responsible for shutting off this dominant episode of star formation must have done so uniformly throughout the galaxy.