Luminous Starbursts in the Redshift Desert at z~1-2: Star Formation Rates, Masses & Evidence for Outflows

TL;DR

This study presents a spectroscopic catalog of 40 luminous starburst galaxies at redshifts 0.7-1.7, revealing their star formation rates, dynamical masses, and evidence of large-scale outflows, filling a gap in the redshift desert.

Contribution

It provides new spectroscopic data on luminous starburst galaxies at z~1-2, including submillimetre and radio selected samples, and analyzes their outflows and dynamical properties.

Findings

Star formation rates range from 50 to 500 M_sun/yr.

Galaxies show evidence of large-scale outflows with blueshifted absorption lines.

Dynamical masses are similar to those at z~2, indicating little evolution.

Abstract

We present a spectroscopic catalogue of 40 luminous starburst galaxies at z=0.7--1.7 (median z=1.3). 19 of these are submillimetre galaxies (SMGs) and 21 are submillimetre-faint radio galaxies (SFRGs). This sample helps to fill in the redshift desert at z=1.2--1.7 in previous studies as well as probing a lower luminosity population of galaxies. Radio fluxes are used to determine star-formation rates for our sample which range from around 50 to 500 M$_\odot$ yr$^{-1}$ and are generally lower than those in z$\sim$2 SMGs. We identify nebular [OII] 3727 emission in the rest-UV spectra and use the linewidths to show that SMGs and SFRGs in our sample have larger linewidths and therefore dynamical masses than optically selected star-forming galaxies at similar redshifts. The linewidths are indistinguishable from those measured in the z$\sim$2 SMG populations suggesting little evolution in the dynamical masses of the galaxies between redshift 1--2. [NeV] and [NeIII] emission lines are identified in a subset of the spectra indicating the presence of an active galactic nucleus (AGN). In addition, a host of interstellar absorption lines corresponding to transitions of MgII and FeII ions are also detected. These features show up prominently in composite spectra and we use these composites to demonstrate that the absorption lines are present at an average blueshift of $-240\pm$50 kms$^{-1}$ relative to the systemic velocities of the galaxies derived from [OII]. This indicates the presence of large-scale outflowing interstellar gas in these systems (Abridged)