Kavli Affiliate: Michael A. McDonald
| First 5 Authors: Keunho J. Kim, Matthew B. Bayliss, Allison G. Noble, Gourav Khullar, Ethan Cronk
| Summary:
The environments where galaxies reside play a key role in shaping their star
formation histories over cosmic time, yet such environmental effects remain
elusive at high redshifts. We update this environmental process by adopting an
advanced measure for cluster in-fall time using kinematics and reveal that
galaxies experience a gradual decline of star formation after they fall into
cluster environments up to $z sim 1$. This conclusion is drawn from a uniform
analysis of a remarkably large sample of 105 clusters and 1626
spectroscopically-confirmed member galaxies from the SPT and ACT
Sunyaev-Zel’dovich surveys at 0.26 $< z <$ 1.13. Intriguingly, we find clear
evidence for a gradual increase in the mean age ($sim$ 0.71 $pm$ 0.4 Gyr
based on a 4000 Angstrom break, $rm D_{rm n}4000$) of the galaxy’s stellar
populations with the time spent in the cluster environment. This environmental
quenching effect is found regardless of galaxy luminosity (faint or bright) and
redshift (low-$z$ or high-$z$), although the exact stellar age of galaxies
depends on both parameters at fixed environmental effect. Such a systematic
increase of $rm D_{rm n}4000$ with in-fall proxy would suggest that galaxies
that were accreted into hosts earlier were quenched earlier, due to longer
exposure to environmental effects such as ram pressure stripping and
strangulation. Thus, our results provide new insights into environmental
quenching effects spanning a large range in cosmic time ($sim 5.2$ Gyr,
$z=0.26-1.13$) and demonstrate the power of using a kinematically-derived
in-fall time proxy.
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