ZFIRE: 3D Modeling of Rotation, Dispersion, and Angular Momentum of Star-forming Galaxies at z ~ 2

Abstract

We perform a kinematic and morphological analysis of 44 star-forming galaxies at z ~ 2 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 Hα emission lines. Hα 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/σ 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 $\mathrm{log}({S}_{0.5})=(0.38\pm 0.07)\mathrm{log}(M/{M}_{\odot }-10)+(2.04\pm 0.03)$ with no significant offset between morphological populations and similar levels of scatter (~0.16 dex). Additionally, we identify a correlation between M sstarf and V 2.2/σ g for the total sample, showing an increasing level of rotation dominance with increasing M sstarf, 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 0.36 ± 0.12, shallower than predicted without mass-dependent disk growth, but this result is possibly due to measurement uncertainty at M sstarf < 9.5 However, through a Kolmogorov–Smirnov test we find irregular galaxies to have marginally higher j disk values than regular galaxies, and high scatter at low masses in both populations. Show more