SQuIGG$\vec{L}$E Survey: Massive z$\sim$0.6 Post-Starburst Galaxies Exhibit Flat Age Gradients

Abstract

We present Gemini GMOS IFU observations of six massive ($M_\star\geq10^{11} \ M_\odot$) A-star dominated post-starburst galaxies at $z\sim0.6$. These galaxies are a subsample of the SQuIGG$\vec{L}$E 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 $H\delta_A$ absorption as a proxy for stellar age, we constrain five of the galaxies to have young ($\sim 600$ 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 $H\delta_A$ 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.