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The average submillimetre properties of Lyman α blobs at z = 3

Hine, N.K.; Geach, J.E.; Matsuda, Y.; Lehmer, B.D.; Michałowski, M.J.; Farrah, D.; Spaans, M.; Oliver, S.J.; Smith, D.J.B.; Chapman, S.C.; Jenness, T.; Alexander, D.M.; Robson, I.; van der Werf, P.

The average submillimetre properties of Lyman α blobs at z = 3 Thumbnail


N.K. Hine

J.E. Geach

Y. Matsuda

B.D. Lehmer

M.J. Michałowski

D. Farrah

M. Spaans

S.J. Oliver

D.J.B. Smith

S.C. Chapman

T. Jenness

I. Robson

P. van der Werf


Ly α blobs (LABs) offer insight into the complex interface between galaxies and their circumgalactic medium. Whilst some LABs have been found to contain luminous star-forming galaxies and active galactic nuclei that could potentially power the Ly α emission, others appear not to be associated with obvious luminous galaxy counterparts. It has been speculated that LABs may be powered by cold gas streaming on to a central galaxy, providing an opportunity to directly observe the ‘cold accretion’ mode of galaxy growth. Star-forming galaxies in LABs could be dust obscured and therefore detectable only at longer wavelengths. We stack deep Submillimetre Common User Bolometer Array 2 (SCUBA-2) observations of the Small Selected Area 22h field to determine the average 850 μm flux density of 34 LABs. We measure S850 = 0.6 ± 0.2 mJy for all LABs, but stacking the LABs by size indicates that only the largest third (area ≥1794 kpc2) have a mean detection, at 4.5σ, with S850 = 1.4 ± 0.3 mJy. Only two LABs (1 and 18) have individual SCUBA-2 >3.5σ detections at a depth of 1.1 mJy beam−1. We consider two possible mechanisms for powering the LABs and find that central star formation is likely to dominate the emission of Ly α, with cold accretion playing a secondary role.

Journal Article Type Article
Acceptance Date May 16, 2016
Online Publication Date Jun 8, 2016
Publication Date Aug 21, 2016
Deposit Date Jun 21, 2017
Publicly Available Date Jun 30, 2017
Journal Monthly Notices of the Royal Astronomical Society
Print ISSN 0035-8711
Electronic ISSN 1365-2966
Publisher Royal Astronomical Society
Peer Reviewed Peer Reviewed
Volume 460
Issue 4
Pages 4075-4085
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Copyright Statement
© The Author 2016. Published by Oxford University Press on behalf of The Royal Astronomical Society. This is an Open Access article distributed under the
terms of the Creative Commons Attribution License (, which permits unrestricted reuse, distribution, and
reproduction in any medium, provided the original work is properly cited.

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