SDSS shocked post-starburst gal. with HST obs.

To answer this question, we analyzed a set of 26 gas-rich, shocked post-starburst galaxies with Hubble Space Telescope (HST) imaging in B, I, and H bands and Sloan Digital Sky Survey (SDSS) i-band imaging of similar depth but lower resolution. We found that post-starbursts in our sample have intermediate morphologies between disk- and bulge-dominated (Sersic n=1.7_-0.0_^+0.3^) and have red bulges, likely due to dust obscuration in the cores.

A majority of galaxies in our sample are more morphologically disturbed than regular galaxies (88%, corresponding to >3{sigma} significance) when observed with HST, with asymmetry and Sersic residual flux fraction being the most successful measures of disturbance. Most disturbances are undetected at the lower resolution of SDSS imaging. Although ~27% galaxies are clear merger remnants, we found that disturbances in another ~30% of the sample are internal, caused by small-scale perturbations or dust substructures rather than tidal features, and require high-resolution imaging to detect.