THE SCUBA-2 COSMOLOGY LEGACY SURVEY: ALMA RESOLVES the BRIGHT-END of the SUB-MILLIMETER NUMBER COUNTS
Journal article, 2015
We present high-resolution 870 μm Atacama Large Millimeter/sub-millimeter Array (ALMA) continuum maps of 30 bright sub-millimeter sources in the UKIDSS UDS field. These sources are selected from deep, 1 degree2 850 μm maps from the SCUBA-2 Cosmology Legacy Survey, and are representative of the brightest sources in the field (median SSCUBA-2= 8.7 ± 0.4 mJy). We detect 52 sub-millimeter galaxies (SMGs) at >4σ significance in our 30 ALMA maps. In 61-15+19% of the ALMA maps the single-dish source comprises a blend of ≥2 SMGs, where the secondary SMGs are Ultra-luminous Infrared Galaxies (ULIRGs) with LIR ≳ 1012 L⊙. The brightest SMG contributes on average 80-2+6% of the single-dish flux density, and in the ALMA maps containing ≥2 SMGs the secondary SMG contributes 25-5+1% of the integrated ALMA flux. We construct source counts and show that multiplicity boosts the apparent single-dish cumulative counts by 20% at S870 > 7.5 mJy, and by 60% at S870 > 12 mJy. We combine our sample with previous ALMA studies of fainter SMGs and show that the counts are well-described by a double power law with a break at 8.5 ± 0.6 mJy. The break corresponds to a luminosity of ∼6 × 1012 L⊙ or a star formation rate (SFR) of ∼103 M⊙ yr-1. For the typical sizes of these SMGs, which are resolved in our ALMA data with Re = 1.2 ± 0.1 kpc, this yields a limiting SFR density of ∼100 M⊙ yr-1 kpc-2 Finally, the number density of S870 ≳ 2 mJy SMGs is 80 ± 30 times higher than that derived from blank-field counts. An over-abundance of faint SMGs is inconsistent with line-of-sight projections dominating multiplicity in the brightest SMGs, and indicates that a significant proportion of these high-redshift ULIRGs are likely to be physically associated.
galaxies: starburst
submillimeter: galaxies
galaxies: abundances
galaxies: high-redshift
galaxies: star formation
Author
J. M. Simpson
Durham University
I. Smail
Durham University
A.M. Swinbank
Durham University
S.C. Chapman
Dalhousie University
J.E. Geach
University of Hertfordshire
R.J. Ivison
University of Edinburgh
European Southern Observatory (ESO)
A. P. Thomson
Durham University
I. Aretxaga
National Institute of Astrophysics, Optics and Electronics
A.W. Blain
University Of Leicester
W.I. Cowley
Durham University
C. C. Chen
Durham University
K. E. K. Coppin
University of Hertfordshire
J.S. Dunlop
University of Edinburgh
A. C. Edge
Durham University
D. Farrah
Virginia Polytechnic Institute and State University
E. Ibar
University of Valparaíso
A. Karim
University of Bonn
Kirsten Kraiberg Knudsen
Chalmers, Earth and Space Sciences, Radio Astronomy and Astrophysics
R. Meijerink
Leiden University
M. J. Michalowski
University of Edinburgh
D. Scott
University of British Columbia (UBC)
M. Spaans
University of Groningen
P.P. van der Werf
Leiden University
Astrophysical Journal
0004-637X (ISSN) 1538-4357 (eISSN)
Vol. 807 2 128Subject Categories (SSIF 2011)
Astronomy, Astrophysics and Cosmology
Roots
Basic sciences
DOI
10.1088/0004-637X/807/2/128