Coppin, K. E. K. and Smail, Ian and Alexander, D. M. and Weiss, A. and Walter, F. and Swinbank, A. M. and Greve, T. R. and Kovacs, A. and De Breuck, C. and Dickinson, M. and Ibar, E. and Ivison, R. J. and Reddy, N. and Spinrad, H. and Stern, D. and Brandt, W. N. and Chapman, S. C. and Dannerbauer, H. and van Dokkum, P. and Dunlop, J. S. and Frayer, D. and Gawiser, E. and Geach, J. E. and Huynh, M. and Knudsen, K. K. and Koekemoer, A. M. and Lehmer, B. D. and Menten, K. M. and Papovich, C. and Rix, H.-W. and Schinnerer, E. and Wardlow, J. L. and van der Werf, P. P. (2009) A submillimetre galaxy at z = 4.76 in the LABOCA survey of the Extended Chandra Deep Field-South. Monthly Notices of the Royal Astronomical Society, 395 (4). pp. 1905-1914. ISSN 0035-8711
0902.4464.pdf - Accepted Version
Available under License Creative Commons Attribution-NonCommercial.
Download (565kB)
Abstract
We report on the identification of the highest redshift submillimetre-selected source currently known LESSJ033229.4-275619. This source was detected in the Large Apex Bolometer Camera (LABOCA) Extended Chandra Deep Field-South (ECDF-S) Submillimetre Survey (LESS), a sensitive 870-μm survey (σ870μm ~ 1.2mJy) of the full 30 × 30arcmin2 ECDF-S with the LABOCA on the Atacama Pathfinder Experiment telescope. The submillimetre emission is identified with a radio counterpart for which optical spectroscopy provides a redshift of z = 4.76. We show that the bolometric emission is dominated by a starburst with a star formation rate of ~1000Msolaryr-1, although we also identify a moderate luminosity active galactic nucleus (AGN) in this galaxy. Thus it has characteristics similar to those of z ~ 2 submillimetre galaxies (SMGs), with a mix of starburst and obscured AGN signatures. This demonstrates that ultraluminous starburst activity is not just restricted to the hosts of the most luminous (and hence rare) quasi-stellar objects at z ~ 5, but was also occurring in less extreme galaxies at a time when the Universe was less than 10 per cent of its current age. Assuming that we are seeing the major phase of star formation in this galaxy, then we demonstrate that it would be identified as a luminous distant red galaxy at z ~ 3 and that the current estimate of the space density of z > 4 SMGs is only sufficient to produce >~10 per cent of the luminous red galaxy population at these early times. However, this leaves open the possibility that some of these galaxies formed through less intense, but more extended star formation events. If the progenitors of all of the luminous red galaxies at z ~ 3 go through an ultraluminous starburst at z >~ 4 then the required volume density of z > 4 SMGs will exceed that predicted by current galaxy formation models by more than an order of magnitude.