Dynamical Properties of z~2 Star Forming Galaxies and a Universal Star Formation Relation

TL;DR

This study compares the dynamical properties of various z~2 star forming galaxy samples, revealing differences in angular momentum and density, and suggests a universal star formation relation applicable across different galaxy types and epochs.

Contribution

It provides the first detailed comparison of the dynamical properties of UV-selected, optically-selected, and submillimeter galaxies at z~2, highlighting their distinct formation processes and a universal star formation relation.

Findings

UV- and optically-selected galaxies follow a disk-like velocity-size relation.

SMGs have larger velocity widths, smaller sizes, and higher densities.

SMGs align with a universal Schmidt-Kennicutt relation with a slope of ~1.7.

Abstract

We present the first comparison of the dynamical properties of different samples of z~1.4-3.4 star forming galaxies from spatially resolved imaging spectroscopy from SINFONI/VLT integral field spectroscopy and IRAM CO millimeter interferometry. Our samples include 16 rest-frame UV-selected, 16 rest-frame optically-selected and 13 submillimeter galaxies (SMGs). We find that restframe UV- and optically bright (K<20) z~2 star forming galaxies are dynamically similar, and follow the same velocity-size relation as disk galaxies at z~0. In the theoretical framework of rotating disks forming from dissipative collapse in dark matter halos, the two samples require a spin parameter ranging from 0.06 to 0.2. In contrast bright SMGs have larger velocity widths and are much more compact. Hence, SMGs have lower angular momenta and higher matter densities than either of the UV- or optically selected populations. This indicates that dissipative major mergers may dominate the SMGs population, resulting in early spheroids, and that the majority of UV/optically bright galaxies have evolved less violently [...]. These early disks may later evolve into spheroids via disk instabilities or mergers. Because of their small sizes and large densities, SMGs lie at the high surface density end of a universal (out to z=2.5) "Schmidt-Kennicutt" relation between gas surface density and star formation rate surface density with a slope of ~1.7.