Examinando por Autor "Yee H.K.C."
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Ítem 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.Ítem 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..Ítem The GOGREEN survey: Post-infall environmental quenching fails to predict the observed age difference between quiescent field and cluster galaxies at z > 1(Oxford University Press, 2020-11) Webb K.; Balogh M.L.; Leja J.; van der Burg R.F.J.; Rudnick G.; Muzzin A.; Boak K.; Cerulo P.; Gilbank D.; Lidman C.; Old L.J.; Pintos-Castro I.; McGee S.; Shipley H.; Biviano A.; Chan J.C.C.; Cooper M.; de Lucia G.; Demarco R.; Forrest B.; Jablonka P.; Kukstas E.; McCarthy I.G.; McNab K.; Nantais J.; Noble A.; Poggianti B.; Reeves A.M.M.; Vulcani B.; Wilson G.; Yee H.K.C.; Zaritsky D.We study the star formation histories (SFHs) and mass-weighted ages of 331 UVJ-selected quiescent galaxies in 11 galaxy clusters and in the field at 1 < z < 1.5 from the Gemini Observations of Galaxies in Rich Early ENvironments (GOGREEN) survey. We determine the SFHs of individual galaxies by simultaneously fitting rest-frame optical spectroscopy and broadband photometry to stellar population models. We confirm that the SFHs are consistent with more massive galaxies having on average earlier formation times. Comparing galaxies found in massive clusters with those in the field, we find galaxies with M∗ < 1011.3 M in the field have more extended SFHs. From the SFHs we calculate the mass-weighted ages, and compare age distributions of galaxies between the two environments, at fixed mass. We constrain the difference in mass-weighted ages between field and cluster galaxies to 0.31+0.51−0.33 Gyr, in the sense that cluster galaxies are older. We place this result in the context of two simple quenching models and show that neither environmental quenching based on time since infall (without pre-processing) nor a difference in formation times alone can reproduce both the average age difference and relative quenched fractions. This is distinctly different from local clusters, for which the majority of the quenched population is consistent with having been environmentally quenched upon infall. Our results suggest that quenched population in galaxy clusters at z > 1 has been driven by different physical processes than those at play at z = 0. © 2020 The Author(s)Ítem VLT/MAGELLAN SPECTROSCOPY of 29 STRONG LENSING SELECTED GALAXY CLUSTERS(Institute of Physics Publishing, 2017-01) Carrasco, Mauricio; Barrientos, L. Felipe; Anguita, Timo; García-Vergara, Cristina; Bayliss, Matthew; Gladders, Michael; Gilbank, David; Yee H.K.C.; West, MichaelWe present an extensive spectroscopic follow-up campaign of 29 strong lensing (SL) selected galaxy clusters discovered primarily in the Second Red-Sequence Cluster Survey (RCS-2). Our spectroscopic analysis yields redshifts for 52 gravitational arcs present in the core of our galaxy clusters, which correspond to 35 distinct background sources that are clearly distorted by the gravitational potential of these clusters. These lensed galaxies span a wide redshift range of 0.8 ≤ z ≤ 2.9, with a median redshift of z s = 1.8 ± 0.1. We also measure reliable redshifts for 1004 cluster members, allowing us to obtain robust velocity dispersion measurements for 23 of these clusters, which we then use to determine their dynamical masses by using a simulation-based σ DM - M 200 scaling relation. The redshift and mass ranges covered by our SL sample are 0.22 ≤ z ≤ 1.01 and , respectively. We analyze and quantify some possible effects that might bias our mass estimates, such as the presence of substructure, the region where cluster members are selected for spectroscopic follow-up, the final number of confirmed members, and line-of-sight effects. We find that 10 clusters of our sample with N mem 20 show signs of dynamical substructure. However, the velocity data of only one system is inconsistent with a uni-modal distribution. We therefore assume that the substructures are only marginal and not of comparable size to the clusters themselves. Consequently, our velocity dispersion and mass estimates can be used as priors for SL mass reconstruction studies and also represent an important step toward a better understanding of the properties of the SL galaxy cluster population. © 2017. The American Astronomical Society. All rights reserved.