IROCKS: Spatially resolved kinematics of z~1 star forming galaxies

TL;DR

This study uses high-resolution observations to analyze the kinematics and morphology of z~1 star-forming galaxies, revealing persistent turbulence, diverse galaxy dynamics, and evolving star-forming clumps linked to gas content.

Contribution

First spatially resolved kinematic analysis of z~1 galaxies using adaptive optics, distinguishing disk and merger-like systems, and examining star-forming clump properties and evolution.

Findings

Elevated velocity dispersions persist at z~1.

One-third of galaxies are disk candidates, two-thirds are mergers or irregulars.

Clump properties scale with redshift, indicating evolution in star formation processes.

Abstract

We present results from IROCKS (Intermediate Redshift OSIRIS Chemo-Kinematic Survey) for sixteen z~1 and one z~1.4 star-forming galaxies. All galaxies were observed with OSIRIS with the laser guide star adaptive optics system at Keck Observatory. We use rest-frame nebular Ha emission lines to trace morphologies and kinematics of ionized gas in star-forming galaxies on sub-kiloparsec physical scales. We observe elevated velocity dispersions (sigma > 50 km/s) seen in z > 1.5 galaxies persist at z~1 in the integrated galaxies. Using an inclined disk model and the ratio of v/sigma, we find that 1/3 of the z~1 sample are disk candidates while the other 2/3 of the sample are dominated by merger-like and irregular sources. We find that including extra attenuation towards HII regions derived from stellar population synthesis modeling brings star formation rates (SFR) using Ha and stellar population fit into a better agreement. We explore properties of compact Ha sub-component, or "clump," at z~1 and find that they follow a similar size-luminosity relation as local HII regions but are scaled-up by an order of magnitude with higher luminosities and sizes. Comparing the z~1 clumps to other high-redshift clump studies, we determine that the clump SFR surface density evolves as a function of redshift. This may imply clump formation is directly related to the gas fraction in these systems and support disk fragmentation as their formation mechanism since gas fraction scales with redshift.