Ubiquitous Molecular Outflows in z > 4 Massive, Dusty Galaxies. II. Momentum-driven Winds Powered by Star Formation in the Early Universe
Justin Spilker, Manuel Aravena, Kedar A. Phadke, M. Béthermin, S. C. Chapman, Chenxing Dong, Anthony H. Gonzalez, Christopher C. Hayward, Yashar Hezaveh, Katrina C. Litke, Matthew A. Malkan, Daniel P. Marrone, Desika Narayanan, C. Reuter, J. D. Vieira, A. Weiß
Abstract
Galactic outflows of molecular gas are a common occurrence in galaxies and\nmay represent a mechanism by which galaxies self-regulate their growth,\nredistributing gas that could otherwise have formed stars. We previously\npresented the first survey of molecular outflows at z > 4 towards a sample of\nmassive, dusty galaxies. Here we characterize the physical properties of the\nmolecular outflows discovered in our survey. Using low-redshift outflows as a\ntraining set, we find agreement at the factor-of-two level between several\noutflow rate estimates. We find molecular outflow rates 150-800Msun/yr and\ninfer mass loading factors just below unity. Among the high-redshift sources,\nthe molecular mass loading factor shows no strong correlations with any other\nmeasured quantity. The outflow energetics are consistent with expectations for\nmomentum-driven winds with star formation as the driving source, with no need\nfor energy-conserving phases. There is no evidence for AGN activity in our\nsample, and while we cannot rule out deeply-buried AGN, their presence is not\nrequired to explain the outflow energetics, in contrast to nearby obscured\ngalaxies with fast outflows. The fraction of the outflowing gas that will\nescape into the circumgalactic medium (CGM), though highly uncertain, may be as\nhigh as 50%. This nevertheless constitutes only a small fraction of the total\ncool CGM mass based on a comparison to z~2-3 quasar absorption line studies,\nbut could represent >~10% of the CGM metal mass. Our survey offers the first\nstatistical characterization of molecular outflow properties in the very early\nuniverse.