Abstract
We present Keck/MOSFIRE observations of the role of environment in the
formation of galaxies at z~2. Using K-band spectroscopy of H-alpha and N II
emission lines, we have analyzed the metallicities of galaxies within and
around a z=2.3 protocluster discovered in the HS1700+643 field. Our main sample
consists of 23 protocluster and 20 field galaxies with estimates of stellar
masses and gas-phase metallicities based on the N2 strong-line metallicity
indicator. With these data we have examined the mass-metallicity relation (MZR)
with respect to environment at z~2. We find that field galaxies follow the
well-established trend between stellar mass and metallicity, such that more
massive galaxies have larger metallicities. The protocluster galaxies, however,
do not exhibit a dependence of metallicity on mass, with the low-mass
protocluster galaxies showing an enhancement in metallicity compared to field
galaxies spanning the same mass range. A comparison with galaxy formation
models suggests that the mass-dependent environmental trend we observed can be
qualitatively explained in the context of the recycling of "momentum-driven"
galaxy wind material. Accordingly, winds are recycled on a shorter timescale in
denser environments, leading to an enhancement in metallicity at fixed mass for
all but the most massive galaxies. Future hydrodynamical simulations of z~2
overdensities matching the one in the HS1700 field will be crucial for
understanding the origin of the observed environmental trend in detail.
Users
Please
log in to take part in the discussion (add own reviews or comments).