The KMOS^3D Survey: Demographics and Properties of Galactic Outflows at z = 0.6 - 2.7

TL;DR

This study provides a comprehensive census of ionized gas outflows in 599 galaxies at redshifts 0.6-2.7, revealing how outflow properties vary with galaxy mass, star formation, and AGN activity, and their potential role in galaxy evolution.

Contribution

It offers the first large, homogeneous analysis of ionized outflows across a wide galaxy mass range at high redshift, distinguishing between star formation and AGN-driven winds.

Findings

Approximately one-third of galaxies exhibit outflows.

Star formation-driven winds have velocities around 450 km/s.

AGN-driven winds reach velocities of 1000-2000 km/s, especially in massive galaxies.

Abstract

We present a census of ionized gas outflows in 599 normal galaxies at redshift 0.6<z<2.7, mostly based on integral field spectroscopy of Ha, [NII], and [SII] line emission. The sample fairly homogeneously covers the main sequence of star-forming galaxies with masses 9.0<log(M*/Msun)<11.7, and probes into the regimes of quiescent galaxies and starburst outliers. About 1/3 exhibits the high-velocity component indicative of outflows, roughly equally split into winds driven by star formation (SF) and active galactic nuclei (AGN). The incidence of SF-driven winds correlates mainly with star formation properties. These outflows have typical velocities of ~450 km/s, local electron densities of n_e~380 cm^-3, modest mass loading factors of ~0.1-0.2 at all galaxy masses, and energetics compatible with momentum driving by young stellar populations. The SF-driven winds may escape from log(M*/Msun)<10.3 galaxies but substantial mass, momentum, and energy in hotter and colder outflow phases seem required to account for low galaxy formation efficiencies in the low-mass regime. Faster AGN-driven outflows (~1000-2000 km/s) are commonly detected above log(M*/Msun)~10.7, in up to ~75% of log(M*/Msun)>11.2 galaxies. The incidence, strength, and velocity of AGN-driven winds strongly correlates with stellar mass and central concentration. Their outflowing ionized gas appears denser (n_e~1000 cm^-3), and possibly compressed and shock-excited. These winds have comparable mass loading factors as the SF-driven winds but carry ~10 (~50) times more momentum (energy). The results confirm our previous findings of high duty cycle, energy-driven outflows powered by AGN above the Schechter mass, which may contribute to star formation quenching.