Integral Field Spectroscopy of High-Redshift Star Forming Galaxies with Laser Guided Adaptive Optics: Evidence for Dispersion-Dominated Kinematics

TL;DR

This study uses advanced adaptive optics integral-field spectroscopy to analyze the kinematic structures of high-redshift star-forming galaxies, revealing mostly dispersion-dominated dynamics with some evidence of velocity gradients.

Contribution

First detailed kinematic maps of high-redshift galaxies obtained with laser guide star adaptive optics, showing dispersion-dominated velocity fields and limited rotational features.

Findings

Most galaxies show dispersion-dominated kinematics with little large-scale structure.

One galaxy exhibits a velocity gradient inconsistent with a cold rotating disk.

Kinematic properties are related to physical parameters like stellar mass and star formation rate.

Abstract

We present early results from an ongoing study of the kinematic structure of star-forming galaxies at redshift z ~ 2 - 3 using integral-field spectroscopy of rest-frame optical nebular emission lines in combination with Keck laser guide star adaptive optics (LGSAO). We show kinematic maps of 3 target galaxies Q1623-BX453, Q0449-BX93, and DSF2237a-C2 located at redshifts z = 2.1820, 2.0067, and 3.3172 respectively, each of which is well-resolved with a PSF measuring approximately 0.11 - 0.15 arcsec (~ 900 - 1200 pc at z ~ 2-3) after cosmetic smoothing. Neither galaxy at z ~ 2 exhibits substantial kinematic structure on scales >~ 30 km/s; both are instead consistent with largely dispersion-dominated velocity fields with sigma ~ 80 km/s along any given line of sight into the galaxy. In contrast, DSF2237a-C2 presents a well-resolved gradient in velocity over a distance of ~ 4 kpc with peak-to-peak amplitude of 140 km/s. It is unlikely that DSF2237a-C2 represents a dynamically cold rotating disk of ionized gas as the local velocity dispersion of the galaxy (sigma = 79 km/s) is comparable to the observed shear. Using extant multi-wavelength spectroscopy and photometry we relate these kinematic data to physical properties such as stellar mass, gas fraction, star formation rate, and outflow kinematics and consider the applicability of current galaxy formation models.[Abridged]