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Register a new userZFIRE: Similar Stellar Growth in H$alpha$-emitting Cluster and Field Galaxies at z~2
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We compare galaxy scaling relations as a function of environment at $zsim2$ 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 $log(r_{eff})sim0.1$ larger than in the field. Approximately 19% of the H$alpha$-emitters in the cluster and 26% in the field are IR-luminous ($L_{IR}>2times10^{11} L_{odot}$). Because the LIRGs in our combined sample are $sim5$ times more massive than the low-IR galaxies, their radii are $sim70$% 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$(M_{star})=pm0.2$ 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 $zsim2$ 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 $sim2$ which seems to be a common problem for simulations across environment.
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We present a sample of 33 spectroscopically confirmed z ~ 3.1 Ly$alpha$-emitting galaxies (LAEs) in the Cosmological Evolution Survey (COSMOS) field. This paper details the narrow-band survey we conducted to detect the LAE sample, the optical spectroscopy we performed to confirm the nature of these LAEs, and a new near-infrared spectroscopic detection of the [O III] 5007 AA line in one of these LAEs. This detection is in addition to two [O III] detections in two z ~ 3.1 LAEs we have reported on previously (McLinden et al 2011). The bulk of the paper then presents detailed constraints on the physical characteristics of the entire LAE sample from spectral energy distribution (SED) fitting. These characteristics include mass, age, star-formation history, dust content, and metallicity. We also detail an approach to account for nebular emission lines in the SED fitting process - wherein our models predict the strength of the [O III] line in an LAE spectrum. We are able to study the success of this prediction because we can compare the model predictions to our actual near-infrared observations both in galaxies that have [O III] detections and those that yielded non-detections. We find a median stellar mass of 6.9 $times$ 10$^8$ M$_{odot}$ and a median star formation rate weighted stellar population age of 4.5 $times$ 10$^6$ yr. In addition to SED fitting, we quantify the velocity offset between the [O III] and Ly$alpha$ lines in the galaxy with the new [O III] detection, finding that the Ly$alpha$ line is shifted 52 km s$^{-1}$ redwards of the [O III] line, which defines the systemic velocity of the galaxy.
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We discovered an over-density of H-alpha-emitting galaxies associated with a Planck compact source in the COSMOS field (PHzG237.0+42.5) through narrow-band imaging observations with Subaru/MOIRCS. This Planck-selected dusty proto-cluster at z=2.16 has 38 H-alpha emitters including six spectroscopically confirmed galaxies in the observed MOIRCS 4x7 field (corresponding to ~2.0x3.5~Mpc^2 in physical scale). We find that massive H-alpha emitters with log(M*/Msun)>10.5 are strongly clustered in the core of the proto-cluster (within ~300-kpc from the density peak of the H-alpha emitters). Most of the H-alpha emitters in this proto-cluster lie along the star-forming main sequence using H-alpha-based SFR estimates, whilst the cluster total SFR derived by integrating the H-alpha-based SFRs is an order of magnitude smaller than those estimated from Planck/Herschel FIR photometry. Our results suggest that H-alpha is a good observable for detecting moderately star-forming galaxies and tracing the large-scale environment in and around high-z dusty proto-clusters, but there is a possibility that a large fraction of star formation could be obscured by dust and undetected in H-alpha observations.
We perform a kinematic and morphological analysis of 44 star-forming galaxies at $zsim2$ in the COSMOS legacy field using near-infrared spectroscopy from Keck/MOSFIRE and F160W imaging from CANDELS/3D-HST as part of the ZFIRE survey. Our sample consists of cluster and field galaxies from $2.0 < z < 2.5$ with K band multi-object slit spectroscopic measurements of their H$alpha$ emission lines. H$alpha$ rotational velocities and gas velocity dispersions are measured using the Heidelberg Emission Line Algorithm (HELA), which compares directly to simulated 3D data-cubes. Using a suite of simulated emission lines, we determine that HELA reliably recovers input S$_{0.5}$ and angular momentum at small offsets, but $V_{2.2}/sigma_g$ values are offset and highly scattered. We examine the role of regular and irregular morphology in the stellar mass kinematic scaling relations, deriving the kinematic measurement S$_{0.5}$, and finding $log(S_{0.5}) = (0.38pm0.07)log(M/M_{odot}-10) + (2.04pm0.03)$ with no significant offset between morphological populations and similar levels of scatter ($sim0.16$ dex). Additionally, we identify a correlation between M$_{star}$ and $V_{2.2}/sigma_g$ for the total sample, showing an increasing level of rotation dominance with increasing M$_{star}$, and a high level of scatter for both regular and irregular galaxies. We estimate the specific angular momenta ($j_{disk}$) of these galaxies and find a slope of $0.36pm0.12$, shallower than predicted without mass-dependent disk growth, but this result is possibly due to measurement uncertainty at M$_{star}$ $<$ 9.5. However, through a K-S test we find irregular galaxies to have marginally higher $j_{disk}$ values than regular galaxies, and high scatter at low masses in both populations.
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