Merger Signatures are Common, but not Universal, In Massive, Recently-Quenched Galaxies at z~0 7 by Margaret Verrico et al. on Wednesday 30 November

We present visual classifications of merger-induced tidal disturbances in 143

$\rm{M}_* \sim 10^{11}\rm{M}_\odot$ post-starburst galaxies at z$\sim$0.7

identified in the SQuIGG$\vec{L}$E Sample. This sample spectroscopically

selects galaxies from the Sloan Digital Sky Survey that have stopped their

primary epoch of star formation within the past $\sim$500 Myrs. Visual

classifications are performed on Hyper Suprime Cam (HSC) i-band 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 of $3.6^{+2.9}_{-1.3}$ times the

disturbance rate of older quiescent galaxies and $2.1^{+1.9}_{-.73}$ times the

disturbance rate of star-forming galaxies. Assuming tidal features persist for

$\lesssim500$ 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 ten young ($\lesssim150$ Myr since quenching)

undisturbed galaxies 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.

arXiv: http://arxiv.org/abs/http://arxiv.org/abs/2211.16532v1