Evidence for Wide-Spread AGN Driven Outflows in the Most Massive z~1-2 Star Forming Galaxies

TL;DR

This study provides strong evidence that massive star-forming galaxies at z~1-2 frequently host AGN-driven outflows, with a sharp increase in outflow incidence above a certain stellar mass, impacting galaxy evolution during peak cosmic star formation.

Contribution

It expands the sample size of massive galaxies studied for nuclear outflows and demonstrates the widespread presence of AGN-driven outflows across the main sequence at z~1-2.

Findings

Approximately two thirds of galaxies above log(M*/Msun) ~ 10.9 show broad nuclear emission.

Nuclear outflows are prevalent both above and below the main sequence at z~1-2.

Line ratios indicate excitation by AGN, shocks, or photoionization.

Abstract

In this paper we follow up on our previous detection of nuclear ionized outflows in the most massive (log(M*/Msun) >= 10.9) z~1-3 star-forming galaxies (Forster Schreiber et al.), by increasing the sample size by a factor of six (to 44 galaxies above log(M*/Msun) >= 10.9) from a combination of the SINS/zC-SINF, LUCI, GNIRS, and KMOS^3D spectroscopic surveys. We find a fairly sharp onset of the incidence of broad nuclear emission (FWHM in the Ha, [NII], and [SII] lines ~ 450-5300 km/s), with large [NII]/Ha ratios, above log(M*/Msun) ~ 10.9, with about two thirds of the galaxies in this mass range exhibiting this component. Broad nuclear components near and above the Schechter mass are similarly prevalent above and below the main sequence of star-forming galaxies, and at z~1 and ~2. The line ratios of the nuclear component are fit by excitation from active galactic nuclei (AGN), or by a combination of shocks and photoionization. The incidence of the most massive galaxies with broad nuclear components is at least as large as that of AGNs identified by X-ray, optical, infrared or radio indicators. The mass loading of the nuclear outflows is near unity. Our findings provide compelling evidence for powerful, high-duty cycle, AGN-driven outflows near the Schechter mass, and acting across the peak of cosmic galaxy formation.