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Searching for evidence of energetic feedback in distant galaxies: a galaxy wide outflow in a z ≈ 2 ultraluminous infrared galaxy




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 Near-Infrared Field Spectrometer (NIFS) observations of the [O iii] λ5007 emission from a z≈ 2 ultraluminous infrared galaxy (ULIRG; LIR > 1012 L) with an optically identified active galactic nuclei (AGN). The spatial extent (≈4–8 kpc) of the high velocity and broad [O iii] emission is 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 the order of ≈1059 erg over ≈30 Myr) 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.