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Title: Merger Signatures are Common, but not Universal, in Massive, Recently Quenched Galaxies at z ∼ 0.7

We present visual classifications of merger-induced tidal disturbances in 143M*∼ 1011Mpost-starburst galaxies atz∼ 0.7 identified in theSQuIGGLESample. This sample spectroscopically selects galaxies from the Sloan Digital Sky Survey that have stopped their primary epoch of star formation within the past ∼500 Myr. Visual classifications are performed on Hyper Suprime-Cam imaging. We compare to a control sample of mass- and redshift-matched star-forming and quiescent galaxies from the Large Early Galaxy Census and find that post-starburst galaxies are more likely to be classified as disturbed than either category. This corresponds to a factor of3.61.3+2.9times the disturbance rate of older quiescent galaxies and2.1.73+1.9times the disturbance rate of star-forming galaxies. Assuming tidal features persist for ≲500 Myr, this suggests merging is coincident with quenching in a significant fraction of these post-starbursts. Galaxies with tidal disturbances are younger on average than undisturbed post-starburst galaxies in our sample, suggesting tidal features from a major merger may have faded over time. This may be exacerbated by the fact that, on average, the undisturbed subset is fainter, rendering low-surface-brightness tidal features harder to identify. However, the presence of 10 young (≲150 Myr since quenching) undisturbed galaxies more » suggests that major mergers are not the only fast physical mechanism that shut down the primary epoch of star formation in massive galaxies at intermediate redshift.

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The Astrophysical Journal
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Article No. 5
DOI PREFIX: 10.3847
Sponsoring Org:
National Science Foundation
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