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A submillimeter galaxy illuminating its circumgalactic medium : Lyα scattering in a cold, clumpy outflow.

Geach, J.E. and Bower, R.G. and Alexander, D.M. and Blain, A.W. and Bremer, M.N. and Chapin, E.L. and Chapman, S.C. and Clements, D.L. and Coppin, K.E.K. and Dunlop, J.S. and Farrah, D. and Jenness, T. and Koprowski, M.P. and Micha\lowski, M.J. and Robson, E.I. and Scott, D. and Smith, D.J.B. and Spaans, M. and Swinbank, A.M. and van der Werf, P. (2014) 'A submillimeter galaxy illuminating its circumgalactic medium : Lyα scattering in a cold, clumpy outflow.', Astrophysical journal., 793 (1). p. 22.


We report the detection at 850 μm of the central source in SSA22-LAB1, the archetypal "Lyman-α Blob" (LAB), a 100 kpc scale radio-quiet emission-line nebula at z = 3.1. The flux density of the source, S 850 = 4.6 ± 1.1 mJy, implies the presence of a galaxy or group of galaxies with a total luminosity of L IR ≈ 1012 L ☉. The position of an active source at the center of a ~50 kpc radius ring of linearly polarized Lyα emission detected by Hayes et al. suggests that the central source is leaking Lyα photons preferentially in the plane of the sky, which undergo scattering in H I clouds at a large galactocentric radius. The Lyα morphology around the submillimeter detection is reminiscent of a biconical outflow, and the average Lyα line profiles of the two "lobes" are dominated by a red peak, which is expected for a resonant line emerging from a medium with a bulk velocity gradient that is outflowing relative to the line center. Taken together, these observations provide compelling evidence that the central active galaxy (or galaxies) is responsible for a large fraction of the extended Lyα emission and morphology. Less clear is the history of the cold gas in the circumgalactic medium being traced by Lyα: is it mainly pristine material accreting into the halo that has not yet been processed through an interstellar medium (ISM), now being blown back as it encounters an outflow, or does it mainly comprise gas that has been swept-up within the ISM and expelled from the galaxy?

Item Type:Article
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Keywords:Galaxies: active, Galaxies: formation, Galaxies: high-redshift.
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Publisher statement:© 2014. The American Astronomical Society. All rights reserved.
Date accepted:21 July 2014
Date deposited:21 May 2015
Date of first online publication:September 2014
Date first made open access:No date available

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