TY - JOUR
T1 - Are All Post-starbursts Mergers? HST Reveals Hidden Disturbances in the Majority of PSBs
AU - Sazonova, Elizaveta
AU - Alatalo, Katherine
AU - Rowlands, Kate
AU - Deustua, Susana E.
AU - French, K. Decker
AU - Heckman, Timothy
AU - Lanz, Lauranne
AU - Lisenfeld, Ute
AU - Luo, Yuanze
AU - Medling, Anne
AU - Nyland, Kristina
AU - Otter, Justin A.
AU - Petric, Andreea O.
AU - Snyder, Gregory F.
AU - Urry, Claudia Megan
N1 - Publisher Copyright:
© 2021. The American Astronomical Society. All rights reserved..
PY - 2021/10/1
Y1 - 2021/10/1
N2 - 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) 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 >3σ 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 2.8σ 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.
AB - 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) 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 >3σ 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 2.8σ 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.
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U2 - 10.3847/1538-4357/ac0f7f
DO - 10.3847/1538-4357/ac0f7f
M3 - Article
AN - SCOPUS:85117150982
SN - 0004-637X
VL - 919
JO - Astrophysical Journal
JF - Astrophysical Journal
IS - 2
M1 - 134
ER -