High velocity outflows from young star-forming galaxies in the UKIDSS Ultra-Deep Survey

TL;DR

This study reveals that high velocity galactic outflows are prevalent in star-forming galaxies at redshifts 0.71 to 1.63, with outflow velocities linked to stellar mass and youth, driven mainly by star formation processes.

Contribution

It provides the first comprehensive analysis of outflow velocities across various galaxy properties in this redshift range using stacked spectra from the UKIDSS UDS.

Findings

Outflows are present in nearly all galaxy spectra analyzed.

Outflow velocities range from 100 to 1000 km/s.

Higher velocities (>500 km/s) are associated with more massive and younger galaxies.

Abstract

We investigate galactic-scale outflows in the redshift range 0.71 < z < 1.63, using 413 K-band selected galaxies observed in the spectroscopic follow-up of the UKIDSS Ultra-Deep Survey (UDSz). The galaxies have an average stellar mass of ~10^9.5 solar masses and span a wide range in rest-frame colours, representing typical star-forming galaxies at this epoch. We stack the spectra by various galaxy properties, including stellar mass, [OII] equivalent width, star-formation rate, specific star-formation rate and rest-frame spectral indices. We find that outflows are present in virtually all spectral stacks, with velocities ranging from 100-1000 km s^-1, indicating that large-scale outflowing winds are a common property at these redshifts. The highest velocity outflows (>500 km s^-1) are found in galaxies with the highest stellar masses and the youngest stellar populations. Our findings suggest that high velocity galactic outflows are mostly driven by star-forming processes rather than AGN, with implied mass outflow rates comparable to the rates of star formation. Such behaviour is consistent with models required to reproduce the high-redshift mass-metallicity relation.