ZFIRE: Similar Stellar Growth in H$\alpha$-emitting Cluster and Field Galaxies at z~2

Abstract

We compare galaxy scaling relations as a function of environment at $z\sim 2$ with our ZFIRE survey where we have measured H$\alpha$ fluxes for 90 star-forming galaxies selected from a mass-limited [$\log (M_{\star }/M_{\odot })>9$] sample based on ZFOURGE. The cluster galaxies (37) are part of a confirmed system at z=2.095 and the field galaxies (53) are at $1.9<z<2.4$; all are in the COSMOS legacy field. There is no statistical difference between H$\alpha$-emitting cluster and field populations when comparing their star formation rate (SFR), stellar mass ($M_{\star }$), galaxy size ($r_{eff}$), SFR surface density [$\Sigma$(H${\alpha }_{star}$)], and stellar age distributions. The only difference is that at fixed stellar mass, the H$\alpha$-emitting cluster galaxies are $\log (r_{eff})\sim 0.1$ larger than in the field. Approximately 19% of the H$\alpha$-emitters in the cluster and 26% in the field are IR-luminous ($L_{IR}>2\times 10^{11}{L}_{\odot }$). Because the LIRGs in our combined sample are $\sim 5$ times more massive than the low-IR galaxies, their radii are $\sim 70$% larger. To track stellar growth, we separate galaxies into those that lie above, on, and below the H$\alpha$ star-forming main sequence (SFMS) using $\Delta$SFR$(M_{\star })=\pm 0.2$ dex. Galaxies above the SFMS (starbursts) tend to have higher H$\alpha$ SFR surface densities and younger light-weighted stellar ages compared to galaxies below the SFMS. Our results indicate that starbursts (+SFMS) in the cluster and field at $z\sim 2$ are growing their stellar cores. Lastly, we compare to the (SFR-$M_{\star }$) relation from RHAPSODY cluster simulations and find the predicted slope is nominally consistent with the observations. However, the predicted cluster SFRs tend to be too low by a factor of $\sim 2$ which seems to be a common problem for simulations across environment.

ApJ in press; full version of Table 1 available from ApJ and upon request. Survey websites are http://zfire.swinburne.edu.au and http://zfourge.tamu.edu

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