2D Kinematics and Physical Properties of z~3 Star-Forming Galaxies

TL;DR

This study investigates the kinematic structures and physical properties of four star-forming galaxies at redshift z~3 using integral-field spectroscopy, revealing irregular velocity fields and high velocity dispersions that suggest they are not dynamically cold rotating disks.

Contribution

First detailed kinematic analysis of z~3 star-forming galaxies combining optical nebular lines and UV data, highlighting their irregular dynamics and high velocity dispersions.

Findings

VVDS-20463884 has an irregular velocity field.

VVDS-20298666 shows a clear velocity gradient.

All galaxies exhibit high local velocity dispersions.

Abstract

We present results from a study of the kinematic structure of star-forming galaxies at redshift z~3 selected in the VVDS, using integral-field spectroscopy of rest-frame optical nebular emission lines, in combination with rest-frame UV spectroscopy, ground-based optical/near-IR and Spitzer photometry. We also constrain the underlying stellar populations to address the evolutionary status of these galaxies. We infer the kinematic properties of four galaxies: VVDS-20298666, VVDS-020297772, VVDS-20463884 and VVDS-20335183 with redshifts z = 3.2917, 3.2878, 3.2776, and 3.7062, respectively. While VVDS-20463884 presents an irregular velocity field with a peak in the local velocity dispersion of the galaxy shifted from the centre of the galaxy, VVDS-20298666 has a well-resolved gradient in velocity over a distance of ~4.5 kpc with a peak-to-peak amplitude of v = 91 km/s . We discovered that the nearby galaxy, VVDS-020297772 (which shows traces of AGN activity), is in fact a companion at a similar redshift with a projected separated of 12 kpc. In contrast, the velocity field of VVDS-020335183 seems more consistent with a merger on a rotating disk. However, all of the objects have a high local velocity dispersion (sigma ~ 60-70 km/s), which gives v/sigma < 1. It is unlikely that these galaxies are dynamically cold rotating disk of ionized gas.