The average submillimetre properties of Lyman-alpha Blobs at z=3

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

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Ly-alpha 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-alpha 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 SCUBA-2 observations of the SSA22 field to determine the average 850um flux density of 34 LABs. We measure S_850 = 0.6 +/- 0.2mJy for all LABs, but stacking the LABs by size indicates that only the largest third (area > 1794 kpc^2) have a mean detection, at 4.5 sigma, with S_850 = 1.4 +/- 0.3mJy. Only two LABs (1 and 18) have individual SCUBA-2 > 3.5 sigma detections at a depth of 1.1mJy/beam. We consider two possible mechanisms for powering the LABs and find that central star formation is likely to dominate the emission of Ly-alpha, with cold accretion playing a secondary role.
Original languageEnglish
Pages (from-to)4075-4085
Number of pages11
JournalMonthly Notices of the Royal Astronomical Society
Issue number4
Early online date8 Jun 2016
Publication statusPublished - 21 Aug 2016


  • astro-ph.GA


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