TY - JOUR
T1 - The Ages of Passive Galaxies in a z = 1.62 Protocluster
AU - Lee-Brown, Donald B.
AU - Rudnick, Gregory H.
AU - Momcheva, Ivelina G.
AU - Papovich, Casey
AU - Lotz, Jennifer M.
AU - Tran, Kim Vy H.
AU - Henke, Brittany
AU - Willmer, Christopher N.A.
AU - Brammer, Gabriel B.
AU - Brodwin, Mark
AU - Dunlop, James
AU - Farrah, Duncan
N1 - Publisher Copyright:
© 2017. The American Astronomical Society. All rights reserved.
PY - 2017/7/20
Y1 - 2017/7/20
N2 - We present a study of the relation between galaxy stellar age and mass for 14 members of the z = 1.62 protocluster IRC 0218, using multiband imaging and HST G102 and G141 grism spectroscopy. Using UVJ colors to separate galaxies into star-forming and quiescent populations, we find that, at stellar masses M∗ ≥ 1010.85 M⊙, the quiescent fraction in the protocluster is fQ = 1.0-0.37 +0.00, consistent with a ∼ 2× enhancement relative to the field value, fQ = 0.45-0.03 +0.03. At masses 1010.2 M⊙ ≤ M∗ ≤ 1010.85 M⊙, fQ in the cluster is fQ = 0.40-0.18 +0.20, consistent with the field value of fQ = 0.28-0.02 +0.02. Using galaxy Dn (4000)values derived from the G102 spectroscopy, we find no relation between galaxy stellar age and mass. These results may reflect the impact of merger-driven mass redistribution - which is plausible, as this cluster is known to host many dry mergers. Alternately, they may imply that the trend in fQ in IRC 0218 was imprinted over a short timescale in the protocluster's assembly history. Comparing our results with those of other high-redshift studies and studies of clusters at z ∼ 1, we determine that our observed relation between fQ and stellar mass only mildly evolves between z ∼ 1.6 and z ∼ 1, and only at stellar masses M∗ ≤ 1010.85 M⊙. Both the z ∼ 1 and z ∼ 1.6 results are in agreement that the red sequence in dense environments was already populated at high redshift, z ≳ 3, placing constraints on the mechanism(s) responsible for quenching in dense environments at z ≥ 1.5.
AB - We present a study of the relation between galaxy stellar age and mass for 14 members of the z = 1.62 protocluster IRC 0218, using multiband imaging and HST G102 and G141 grism spectroscopy. Using UVJ colors to separate galaxies into star-forming and quiescent populations, we find that, at stellar masses M∗ ≥ 1010.85 M⊙, the quiescent fraction in the protocluster is fQ = 1.0-0.37 +0.00, consistent with a ∼ 2× enhancement relative to the field value, fQ = 0.45-0.03 +0.03. At masses 1010.2 M⊙ ≤ M∗ ≤ 1010.85 M⊙, fQ in the cluster is fQ = 0.40-0.18 +0.20, consistent with the field value of fQ = 0.28-0.02 +0.02. Using galaxy Dn (4000)values derived from the G102 spectroscopy, we find no relation between galaxy stellar age and mass. These results may reflect the impact of merger-driven mass redistribution - which is plausible, as this cluster is known to host many dry mergers. Alternately, they may imply that the trend in fQ in IRC 0218 was imprinted over a short timescale in the protocluster's assembly history. Comparing our results with those of other high-redshift studies and studies of clusters at z ∼ 1, we determine that our observed relation between fQ and stellar mass only mildly evolves between z ∼ 1.6 and z ∼ 1, and only at stellar masses M∗ ≤ 1010.85 M⊙. Both the z ∼ 1 and z ∼ 1.6 results are in agreement that the red sequence in dense environments was already populated at high redshift, z ≳ 3, placing constraints on the mechanism(s) responsible for quenching in dense environments at z ≥ 1.5.
KW - galaxies: clusters: individual (CLG 0218.3-0510)
KW - galaxies: evolution
KW - galaxies: high-redshift
KW - galaxies: star formation
UR - http://www.scopus.com/inward/record.url?scp=85026394251&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=85026394251&partnerID=8YFLogxK
U2 - 10.3847/1538-4357/aa7948
DO - 10.3847/1538-4357/aa7948
M3 - Article
AN - SCOPUS:85026394251
SN - 0004-637X
VL - 844
JO - Astrophysical Journal
JF - Astrophysical Journal
IS - 1
M1 - 43
ER -