Ubiquitous Molecular Outflows in z > 4 Massive, Dusty Galaxies. I. Sample Overview and Clumpy Structure in Molecular Outflows on 500 pc Scales
Justin Spilker, Kedar A. Phadke, Manuel Aravena, M. Béthermin, S. C. Chapman, Chenxing Dong, Anthony H. Gonzalez, Christopher C. Hayward, Yashar Hezaveh, Sreevani Jarugula, Katrina C. Litke, Matthew A. Malkan, Daniel P. Marrone, Desika Narayanan, C. Reuter, J. D. Vieira, A. Weiß
Abstract
Massive galaxy-scale outflows of gas are one of the most commonly-invoked\nmechanisms to regulate the growth and evolution of galaxies throughout the\nuniverse. While the gas in outflows spans a large range of temperatures and\ndensities, the cold molecular phase is of particular interest because molecular\noutflows may be capable of suppressing star formation in galaxies by removing\nthe star-forming gas. We have conducted the first survey of molecular outflows\nat z > 4, targeting 11 strongly-lensed dusty, star-forming galaxies (DSFGs)\nwith high-resolution Atacama Large Millimeter Array (ALMA) observations of OH\n119um absorption as an outflow tracer. In this first paper, we give an overview\nof the survey, focusing on the detection rate and structure of molecular\noutflows. We find unambiguous evidence for outflows in 8/11 (73%) galaxies,\nmore than tripling the number known at z > 4. This implies that molecular winds\nin z > 4 DSFGs must have both a near-unity occurrence rate and large opening\nangles to be detectable in absorption. Lensing reconstructions reveal that\n500pc-scale clumpy structures in the outflows are common. The individual clumps\nare not directly resolved, but from optical depth arguments we expect that\nfuture observations will require 50-200pc spatial resolution to do so. We do\nnot detect high-velocity [CII] wings in any of the sources with clear OH\noutflows, indicating that [CII] is not a reliable tracer of molecular outflows.\nOur results represent a first step toward characterizing molecular outflows at\nz > 4 at the population level, demonstrating that large-scale outflows are\nubiquitous among early massive, dusty galaxies.