ZFIRE: SIMILAR STELLAR GROWTH IN H α -EMITTING CLUSTER AND FIELD GALAXIES AT z ∼ 2
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We compare galaxy scaling relations as a function of environment at z ∼ 2 with our ZFIRE survey12 where we have measured Hα fluxes for 90 star-forming galaxies selected from a mass-limited (log(Mz.astModot) > 9) sample based on ZFOURGE.13 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 Hα- emitting cluster and field populations when comparing their star formation rate (SFR), stellar mass (M∗), galaxy size (reff ), SFR surface density (σ(H star)), and stellar age distributions. The only difference is that at fixed stellar mass, the Hα-emitting cluster galaxies are log(reff ) ∼ 0.1 larger than in the field. Approximately 19% of the Hα-emitters in the cluster and 26% in the field are IR-luminous (LIR > 2>× 1011 L⊙). Because the luminous IR galaxies in our combined sample are ∼5 times more massive than the low-IR galaxies, their radii are ∼70% larger. To track stellar growth, we separate galaxies into those that lie above, on, or below the Hα star-forming main sequence (SFMS) using δSFR(M∗)=±0.2 dex. Galaxies above the SFMS (starbursts) tend to have higher Hα SFR surface densities and younger light-weighted stellar ages than galaxies below the SFMS. Our results indicate that starbursts (+SFMS) in the cluster and field at z ∼ 2 are growing their stellar cores. Lastly, we compare to the (SFR-M∗) relation from RHAPSODY-G cluster simulations and find that the predicted slope is nominally consistent with the observations. However, the predicted cluster SFRs tend to be too low by a factor of ∼2, which seems to be a common problem for simulations across environment.
author list (cited authors)
Tran, K., Alcorn, L. Y., Kacprzak, G. G., Nanayakkara, T., Straatman, C., Yuan, T., ... Tomczak, A.