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
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}* ≥slant {10}10.85
{M}⊙ , the quiescent fraction in the protocluster is
{f}Q={1.0}-0.37+0.00, consistent with a
˜ 2× enhancement relative to the field value,
{f}Q={0.45}-0.03+0.03. At masses
{10}10.2 {M}⊙ ≤slant {M}*
≤slant {10}10.85 {M}⊙ , f Q
in the cluster is
{f}Q={0.40}-0.18+0.20, consistent with
the field value of
{f}Q={0.28}-0.02+0.02. Using galaxy
{D}n(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 f Q 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 f Q and stellar mass
only mildly evolves between z˜ 1.6 and z˜ 1, and only at stellar
masses {M}* ≤slant {10}10.85 {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≥slant 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}* ≥slant {10}10.85
{M}⊙ , the quiescent fraction in the protocluster is
{f}Q={1.0}-0.37+0.00, consistent with a
˜ 2× enhancement relative to the field value,
{f}Q={0.45}-0.03+0.03. At masses
{10}10.2 {M}⊙ ≤slant {M}*
≤slant {10}10.85 {M}⊙ , f Q
in the cluster is
{f}Q={0.40}-0.18+0.20, consistent with
the field value of
{f}Q={0.28}-0.02+0.02. Using galaxy
{D}n(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 f Q 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 f Q and stellar mass
only mildly evolves between z˜ 1.6 and z˜ 1, and only at stellar
masses {M}* ≤slant {10}10.85 {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≥slant 1.5.
KW - galaxies: clusters: individual: CLG 0218.3-0510
KW - galaxies: evolution
KW - galaxies: high-redshift
KW - galaxies: star formation
U2 - 10.3847/1538-4357/aa7948
DO - 10.3847/1538-4357/aa7948
M3 - Article
VL - 844
JO - Astrophysical Journal
JF - Astrophysical Journal
SN - 0004-637X
IS - 1
ER -