Revealing an Energetic Galaxy-Wide Outflow in a z~2 Ultraluminous Infrared Galaxy

TL;DR

This study presents evidence of a large-scale energetic outflow in a z~2 ultraluminous infrared galaxy, supporting models where such outflows regulate galaxy and black hole growth at high redshift.

Contribution

First direct observation of a galaxy-wide outflow in a z~2 ULIRG with an AGN, indicating such outflows may be common and influential in galaxy evolution.

Findings

Large-scale outflow extends 4-8 kpc from the galaxy.

Outflow energy (~10^59 ergs) can be driven by AGN winds or supernovae.

Outflow energy is comparable to the galaxy's binding energy.

Abstract

Leading models of galaxy formation require large-scale energetic outflows to regulate the growth of distant galaxies and their central black holes. However, current observational support for this hypothesis at high redshift is mostly limited to rare z>2 radio galaxies. Here we present Gemini-North NIFS Intregral Field Unit (IFU) observations of the [O III]5007 emission from a z~2 ultraluminous infrared galaxy (ULIRG; L_IR>10^12 L_sol) with an optically identified Active Galactic Nucleus (AGN). The spatial extent (~4-8 kpc) of the high velocity and broad [O III] emission are consistent with that found in z>2 radio galaxies, indicating the presence of a large-scale energetic outflow in a galaxy population potentially orders of magnitude more common than distant radio galaxies. The low radio luminosity of this system indicates that radio-bright jets are unlikely to be responsible for driving the outflow. However, the estimated energy input required to produce the large-scale outflow signatures (of order ~10^59 ergs over ~30 Myrs) could be delivered by a wind radiatively driven by the AGN and/or supernovae winds from intense star formation. The energy injection required to drive the outflow is comparable to the estimated binding energy of the galaxy spheroid, suggesting that it can have a significant impact on the evolution of the galaxy. We argue that the outflow observed in this system is likely to be comparatively typical of the high-redshift ULIRG population and discuss the implications of these observations for galaxy formation models.