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J.M. Simpson ; I. Smail ; A.M. Swinbank ; S.C. Chapman ; J.E. Geach ; R.J. Ivison ; A.P. Thomson ; I. Aretxaga ; A.W. Blain ; W.I. Cowley ; C.C. Chen ; K.E.K. Coppin ; J.S. Dunlop ; A.C. Edge ; D. Farrah ; E. Ibar ; A. Karim ; Kirsten Kraiberg Knudsen (Institutionen för rymd- och geovetenskap, Radioastronomi och astrofysik) ; R. Meijerink ; M.J. Michałowski ; D. Scott ; M. Spaans ; P.P. van der Werf
Astrophysical Journal (0004-637X). Vol. 807 (2015), 2,
[Artikel, refereegranskad vetenskaplig]

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.

Nyckelord: galaxies: abundances , galaxies: high-redshift , galaxies: star formation , galaxies: starburst , submillimeter: galaxies

Denna post skapades 2015-07-28. Senast ändrad 2015-11-13.
CPL Pubid: 220001


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