Z-FIRE: ISM properties of the z = 2.095 COSMOS Cluster

Abstract

We investigate the ISM properties of 13 star-forming galaxies within the z~2 COSMOS cluster. We show that the cluster members have [NII]/Ha and [OIII]/Hb emission-line ratios similar to z~2 field galaxies, yet systematically different emission-line ratios (by ~0.17 dex) from the majority of local star-forming galaxies. We find no statistically significant difference in the [NII]/Ha and [OIII]/Hb line ratios or ISM pressures among the z~2 cluster galaxies and field galaxies at the same redshift. We show that our cluster galaxies have significantly larger ionization parameters (by up to an order of magnitude) than local star-forming galaxies. We hypothesize that these high ionization parameters may be associated with large specific star formation rates (i.e. a large star formation rate per unit stellar mass). If this hypothesis is correct, then this relationship would have important implications for the geometry and/or the mass of stars contained within individual star clusters as a function of redshift.

11 pages, 5 figures, accepted for publication in ApJ

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• ZFIRE: Similar Stellar Growth in H$\alpha$-emitting Cluster and Field Galaxies at z~2
• ZFIRE: 3D Modeling of Rotation, Dispersion, and Angular Momentum of Star-Forming Galaxies at z~2
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