TY - JOUR
T1 - ALMA measures rapidly depleted molecular gas reservoirs in massive quiescent galaxies at z~1.5
AU - Williams, Christina C.
AU - Spilker, Justin S.
AU - Whitaker, Katherine E.
AU - Davé, Romeel
AU - Woodrum, Charity
AU - Brammer, Gabriel
AU - Bezanson, Rachel
AU - Narayanan, Desika
AU - Weiner, Benjamin
N1 - accepted for publication in ApJ
PY - 2021/2/11
Y1 - 2021/2/11
N2 - We present Atacama Large Millimeter/submillimeter Array (ALMA) CO(2–1) spectroscopy of six massive (log10/ > 11.3) quiescent galaxies at z ∼ 1.5. These data represent the largest sample using CO emission to trace molecular gas in quiescent galaxies above z > 1, achieving an average 3σ sensitivity of ∼ 1010. We detect one galaxy at 4σ significance and place upper limits on the molecular gas reservoirs of the other five, finding molecular gas mass fractions (3σ
upper limits). This is 1–2 orders of magnitude lower than coeval
star-forming galaxies at similar stellar mass, and comparable to
galaxies at z = 0 with similarly low specific star formation rate
(sSFR). This indicates that their molecular gas reservoirs were rapidly
and efficiently used up or destroyed, and that gas fractions are
uniformly low (<6%) despite the structural diversity of our sample.
The implied rapid depletion time of molecular gas (<
0.6 Gyr) disagrees with extrapolations of empirical scaling relations
to low sSFR. We find that our low gas fractions are instead in agreement
with predictions from both the recent simba cosmological simulation, and from analytical "bathtub" models for gas accretion onto galaxies in massive dark matter halos (log at z = 0). Such high mass halos reach a critical mass of log by z ∼ 4
that halt the accretion of baryons early in the universe. Our data are
consistent with a simple picture where galaxies truncate accretion and
then consume the existing gas at or faster than typical main-sequence
rates. Alternatively, we cannot rule out that these galaxies reside in
lower mass halos, and low gas fractions may instead reflect either
stronger feedback, or more efficient gas consumption.
AB - We present Atacama Large Millimeter/submillimeter Array (ALMA) CO(2–1) spectroscopy of six massive (log10/ > 11.3) quiescent galaxies at z ∼ 1.5. These data represent the largest sample using CO emission to trace molecular gas in quiescent galaxies above z > 1, achieving an average 3σ sensitivity of ∼ 1010. We detect one galaxy at 4σ significance and place upper limits on the molecular gas reservoirs of the other five, finding molecular gas mass fractions (3σ
upper limits). This is 1–2 orders of magnitude lower than coeval
star-forming galaxies at similar stellar mass, and comparable to
galaxies at z = 0 with similarly low specific star formation rate
(sSFR). This indicates that their molecular gas reservoirs were rapidly
and efficiently used up or destroyed, and that gas fractions are
uniformly low (<6%) despite the structural diversity of our sample.
The implied rapid depletion time of molecular gas (<
0.6 Gyr) disagrees with extrapolations of empirical scaling relations
to low sSFR. We find that our low gas fractions are instead in agreement
with predictions from both the recent simba cosmological simulation, and from analytical "bathtub" models for gas accretion onto galaxies in massive dark matter halos (log at z = 0). Such high mass halos reach a critical mass of log by z ∼ 4
that halt the accretion of baryons early in the universe. Our data are
consistent with a simple picture where galaxies truncate accretion and
then consume the existing gas at or faster than typical main-sequence
rates. Alternatively, we cannot rule out that these galaxies reside in
lower mass halos, and low gas fractions may instead reflect either
stronger feedback, or more efficient gas consumption.
KW - astro-ph.GA
U2 - 10.3847/1538-4357/abcbf6
DO - 10.3847/1538-4357/abcbf6
M3 - Article
SN - 0004-637X
VL - 908
SP - 1
EP - 15
JO - Astrophysical Journal
JF - Astrophysical Journal
IS - 1
M1 - 54
ER -