An ALMA survey of submillimetre galaxies in the Extended Chandra Deep Field South: high-resolution 870 mu m source counts
Journal article, 2013
We report the first counts of faint submillimetre galaxies (SMGs) in the 870-mu m band derived from arcsecond-resolution observations with the Atacama Large Millimeter Array (ALMA). We have used ALMA to map a sample of 122 870-mu m-selected submillimetre sources drawn from the 0 degrees.5x0 degrees.5 the Large Apex BOlometer CAmera (LABOCA) Extended Chandra Deep Field South submillimetre survey (LESS). These ALMA maps have an average depth of sigma 870(mu m) similar to 0.4 mJy, some approximately three times deeper than the original LABOCA survey and critically the angular resolution is more than an order of magnitude higher, FWHM of similar to 1.5 arcsec compared to similar to 19 arcsec for the LABOCA discovery map. This combination of sensitivity and resolution allows us to precisely pinpoint the SMGs contributing to the submillimetre sources from the LABOCA map, free from the effects of confusion. We show that our ALMA-derived SMG counts broadly agree with the submillimetre source counts from previous, lower resolution single-dish surveys, demonstrating that the bulk of the submillimetre sources are not caused by blending of unresolved SMGs. The difficulty which well-constrained theoretical models have in reproducing the high surface densities of SMGs, thus remains. However, our observations do show that all of the very brightest sources in the LESS sample, S-870 (mu m) greater than or similar to 12 mJy, comprise emission from multiple, fainter SMGs, each with 870-mu m fluxes of less than or similar to 9 mJy. This implies a natural limit to the star formation rate in SMGs of less than or similar to 10(3) M-circle dot yr(-1), which in turn suggests that the space densities of z > 1 galaxies with gas masses in excess of similar to 5 x 10(10) M-circle dot is <10(-5) Mpc(-3). We also discuss the influence of this blending on the identification and characterization of the SMG counterparts to these bright submillimetre sources and suggest that it may be responsible for previous claims that they lie at higher redshifts than fainter SMGs.
starburst galaxies
galaxy abundances
star formation
galaxy evolution
submillimetre galaxies
galaxy formation
Author
A. Karim
Durham University
A. M. Swinbank
Durham University
J. A. Hodge
Max Planck Society
I. Smail
Durham University
F. Walter
Max Planck Society
A. D. Biggs
European Southern Observatory (ESO)
J. M. Simpson
Durham University
A. L. R. Danielson
Durham University
D. M. Alexander
Durham University
F. Bertoldi
University of Bonn
C. De Breuck
European Southern Observatory (ESO)
S. C. Chapman
University of Cambridge
K. E. K. Coppin
McGill University
H. Dannerbauer
University of Vienna
A. C. Edge
Durham University
T. R. Greve
University College London (UCL)
R. J. Ivison
University of Edinburgh
Royal Observatory
Kirsten Kraiberg Knudsen
Chalmers, Earth and Space Sciences, Radio Astronomy and Astrophysics
K. M. Menten
Max Planck Society
E. Schinnerer
Max Planck Society
J. L. Wardlow
University of California at Irvine (UCI)
A. Weiss
Max Planck Society
P. van der Werf
Leiden University
Monthly Notices of the Royal Astronomical Society
0035-8711 (ISSN) 1365-2966 (eISSN)
Vol. 432 1 2-9Subject Categories
Astronomy, Astrophysics and Cosmology
Roots
Basic sciences
DOI
10.1093/mnras/stt196