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 H α emission lines. H α 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 with no significant offset between morphological populations and similar levels of scatter (∼0.16 dex). Additionally, we identify a correlation between M ⋆ and V 2.2 / σ g for the total sample, showing an increasing level of rotation dominance with increasing M ⋆ , 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 ⋆  < 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.