TY - JOUR
T1 - The Evolution of Star Formation Histories of Quiescent Galaxies
AU - Pacifici, Camilla
AU - Kassin, Susan A.
AU - Weiner, Benjamin J.
AU - Holden, Bradford
AU - Gardner, Jonathan P.
AU - Faber, Sandra M.
AU - Ferguson, Henry C.
AU - Koo, David C.
AU - Primack, Joel R.
AU - Bell, Eric F.
AU - Dekel, Avishai
AU - Gawiser, Eric
AU - Giavalisco, Mauro
AU - Rafelski, Marc
AU - Simons, Raymond C.
AU - Barro, Guillermo
AU - Croton, Darren J.
AU - Davé, Romeel
AU - Fontana, Adriano
AU - Grogin, Norman A.
AU - Koekemoer, Anton M.
AU - Lee, Seong-Kook
AU - Salmon, Brett
AU - Somerville, Rachel
AU - Behroozi, Peter
PY - 2016/11/18
Y1 - 2016/11/18
N2 - Although there has been much progress in understanding how galaxies
evolve, we still do not understand how and when they stop forming stars
and become quiescent. We address this by applying our galaxy spectral
energy distribution models, which incorporate physically motivated star
formation histories (SFHs) from cosmological simulations, to a sample of
quiescent galaxies at 0.2\lt z\lt 2.1. A total of 845 quiescent galaxies
with multi-band photometry spanning rest-frame ultraviolet through
near-infrared wavelengths are selected from the Cosmic Assembly Near-IR
Deep Extragalactic Legacy Survey (CANDELS) data set. We compute median
SFHs of these galaxies in bins of stellar mass and redshift. At all
redshifts and stellar masses, the median SFHs rise, reach a peak, and
then decline to reach quiescence. At high redshift, we find that the
rise and decline are fast, as expected, because the universe is young.
At low redshift, the duration of these phases depends strongly on
stellar mass. Low-mass galaxies ({log}({M}* /{M}⊙
)˜ 9.5) grow on average slowly, take a long time to reach
their peak of star formation (≳ 4 Gyr), and then the declining
phase is fast (≲ 2 Gyr). Conversely, high-mass galaxies
({log}({M}* /{M}⊙ )˜ 11) grow on average
fast (≲ 2 Gyr), and, after reaching their peak, decrease the star
formation slowly (≳ 3). These findings are consistent with galaxy
stellar mass being a driving factor in determining how evolved galaxies
are, with high-mass galaxies being the most evolved at any time (I.e.,
downsizing). The different durations we observe in the declining phases
also suggest that low- and high-mass galaxies experience different
quenching mechanisms, which operate on different timescales.
AB - Although there has been much progress in understanding how galaxies
evolve, we still do not understand how and when they stop forming stars
and become quiescent. We address this by applying our galaxy spectral
energy distribution models, which incorporate physically motivated star
formation histories (SFHs) from cosmological simulations, to a sample of
quiescent galaxies at 0.2\lt z\lt 2.1. A total of 845 quiescent galaxies
with multi-band photometry spanning rest-frame ultraviolet through
near-infrared wavelengths are selected from the Cosmic Assembly Near-IR
Deep Extragalactic Legacy Survey (CANDELS) data set. We compute median
SFHs of these galaxies in bins of stellar mass and redshift. At all
redshifts and stellar masses, the median SFHs rise, reach a peak, and
then decline to reach quiescence. At high redshift, we find that the
rise and decline are fast, as expected, because the universe is young.
At low redshift, the duration of these phases depends strongly on
stellar mass. Low-mass galaxies ({log}({M}* /{M}⊙
)˜ 9.5) grow on average slowly, take a long time to reach
their peak of star formation (≳ 4 Gyr), and then the declining
phase is fast (≲ 2 Gyr). Conversely, high-mass galaxies
({log}({M}* /{M}⊙ )˜ 11) grow on average
fast (≲ 2 Gyr), and, after reaching their peak, decrease the star
formation slowly (≳ 3). These findings are consistent with galaxy
stellar mass being a driving factor in determining how evolved galaxies
are, with high-mass galaxies being the most evolved at any time (I.e.,
downsizing). The different durations we observe in the declining phases
also suggest that low- and high-mass galaxies experience different
quenching mechanisms, which operate on different timescales.
KW - galaxies: evolution
KW - galaxies: formation
KW - galaxies: statistics
KW - galaxies: stellar content
U2 - 10.3847/0004-637X/832/1/79
DO - 10.3847/0004-637X/832/1/79
M3 - Article
SN - 0004-637X
VL - 832
SP - 79
JO - Astrophysical Journal
JF - Astrophysical Journal
IS - 1
ER -