Examinando por Autor "Foltz R."

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    ALMA Observations of Gas-rich Galaxies in z ∼ 1.6 Galaxy Clusters: Evidence for Higher Gas Fractions in High-density Environments
    (Institute of Physics Publishing, 2017-06) Noble A.G.; Donald M.; Muzzin A.; Nantais J.; Rudnick G.; Van Kampen E.; Webb T.M.A.; Wilson G.; Yee H.K.C.; Boone K.; Cooper M.C.; DeGroot A.; Delahaye A.; Demarco R.; Foltz R.; Hayden B.; Lidman C.; Manilla-Robles A.; Perlmutter S.
    We present ALMA CO (2-1) detections in 11 gas-rich cluster galaxies at z ∼ 1.6, constituting the largest sample of molecular gas measurements in z > 1.5 clusters to date. The observations span three galaxy clusters, derived from the Spitzer Adaptation of the Red-sequence Cluster Survey. We augment the >5σ detections of the CO (2-1) fluxes with multi-band photometry, yielding stellar masses and infrared-derived star formation rates, to place some of the first constraints on molecular gas properties in z ∼ 1.6 cluster environments. We measure sizable gas reservoirs of 0.5-2 × 1011 M in these objects, with high gas fractions (f gas) and long depletion timescales (τ), averaging 62% and 1.4 Gyr, respectively. We compare our cluster galaxies to the scaling relations of the coeval field, in the context of how gas fractions and depletion timescales vary with respect to the star-forming main sequence. We find that our cluster galaxies lie systematically off the field scaling relations at z = 1.6 toward enhanced gas fractions, at a level of ∼4σ, but have consistent depletion timescales. Exploiting CO detections in lower-redshift clusters from the literature, we investigate the evolution of the gas fraction in cluster galaxies, finding it to mimic the strong rise with redshift in the field. We emphasize the utility of detecting abundant gas-rich galaxies in high-redshift clusters, deeming them as crucial laboratories for future statistical studies. © 2017. The American Astronomical Society. All rights reserved.
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    The Evolution of Environmental Quenching Timescales to z ∼ 1.6: Evidence for Dynamically Driven Quenching of the Cluster Galaxy Population
    (Institute of Physics Publishing, 2018-10) Foltz R.; Wilson G.; Muzzin A.; Cooper M.C.; Nantais J.; Van Der Burg R.F.J.; Cerulo P.; Chan J.; Fillingham S.P.; Surace J.; Webb T.; Noble A.; McDonald M.; Rudnick G.; Lidman C.; Demarco R.; Hlavacek-Larrondo J.; Yee H.K.C.; Perlmutter S.; Hayden B.
    Using a sample of four galaxy clusters at 1.35 < z < 1.65 and 10 galaxy clusters at 0.85 < z < 1.35, we measure the environmental quenching timescale, t Q, corresponding to the time required after a galaxy is accreted by a cluster for it to fully cease star formation. Cluster members are selected by a photometric-redshift criterion, and categorized as star-forming, quiescent, or intermediate according to their dust-corrected rest-frame colors and magnitudes. We employ a "delayed-then-rapid" quenching model that relates a simulated cluster mass accretion rate to the observed numbers of each type of galaxy in the cluster to constrain t Q. For galaxies of mass M ∗ 1010.5 M o, we find a quenching timescale of t Q = Gyr in the z ∼ 1.5 cluster sample, and Gyr at z ∼ 1. Using values drawn from the literature, we compare the redshift evolution of t Q to timescales predicted for different physical quenching mechanisms. We find t Q to depend on host halo mass such that quenching occurs over faster timescales in clusters relative to groups, suggesting that properties of the host halo are responsible for quenching high-mass galaxies. Between z = 0 and z = 1.5, we find that t Q evolves faster than the molecular gas depletion timescale and slower than an estimated star formation rate-outflow timescale, but is consistent with the evolution of the dynamical time. This suggests that environmental quenching in these galaxies is driven by the motion of satellites relative to the cluster environment, although due to uncertainties in the atomic gas budget at high redshift, we cannot rule out quenching due to simple gas depletion. © 2018. The American Astronomical Society. All rights reserved..