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  • Are All Post-starbursts Mer...
    Sazonova, Elizaveta; Alatalo, Katherine; Rowlands, Kate; Deustua, Susana E.; French, K. Decker; Heckman, Timothy; Lanz, Lauranne; Lisenfeld, Ute; Luo, Yuanze; Medling, Anne; Nyland, Kristina; Otter, Justin A.; Petric, Andreea O.; Snyder, Gregory F.; Urry, Claudia Megan

    Astrophysical journal/˜The œAstrophysical journal, 10/2021, Volume: 919, Issue: 2
    Journal Article

    Abstract How do galaxies transform from blue, star-forming spirals to red, quiescent early-type galaxies? 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 (Sérsic 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 σ significance) when observed with HST, with asymmetry and Sérsic 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. We found 2.8 σ evidence that asymmetry features fade on timescales ∼200 Myr, and may vanish entirely after ∼750 Myr, so we do not rule out a possible merger origin of all post-starbursts given that asymmetric features may have already faded. This work highlights the importance of small-scale disturbances, detected only in high-resolution imaging, in understanding structural evolution of transitioning galaxies.