The SCUBA-2 Cosmology Legacy Survey: Multi-wavelength Properties of ALMA-identified Submillimeter Galaxies in UKIDSS UDS

Abstract

The full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-prot purposes provided that:• a full bibliographic reference is made to the original source • a link is made to the metadata record in DRO • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders.Please consult the full DRO policy for further details. AbstractWe present a multi-wavelength analysis of 52 submillimeter galaxies (SMGs), identified using ALMA 870 μm continuum imaging in a pilot program to precisely locate bright SCUBA-2-selected submillimeter sources in the UKIDSS Ultra Deep Survey (UDS) field. Using the available deep (especially near-infrared) panoramic imaging of the UDS field at optical-to-radio wavelengths we characterize key properties of the SMG population. The median photometric redshift of the bright ALMA/SCUBA-2 UDS (AS2UDS) SMGs that are detected in a sufficient number of wavebands to derive a robust photometric redshift is z=2.65±0.13. However, similar to previous studies, 27% of the SMGs are too faint at optical-to-near-infrared wavelengths to derive a reliable photometric redshift. Assuming that these SMGs lie at z  3 raises the median redshift of the full sample to z=2.9±0.2. A subset of 23 unlensed, bright AS2UDS SMGs have sizes measured from resolved imaging of their rest-frame farinfrared emission. We show that the extent and luminosity of the far-infrared emission are consistent with the dust emission arising from regions that are, on average, optically thick at a wavelength of 75 m 0  l m (1σ dispersion of 55-90 μm). Using the dust masses derived from our optically thick spectral energy distribution models, we determine that these galaxies have a median hydrogen column density of N H =9.8 0.7 -+ ×1023 cm −2 , or a corresponding median V-band obscuration of A v =540 40 80 -+ mag, averaged along the line of sight to the source of their rest-frame ∼200 μm emission. We discuss the implications of this extreme attenuation by dust for the multiwavelength study of dusty starbursts and reddening-sensitive tracers of star formation.

The Dust and [C ii] Morphologies of Redshift ∼4.5 Sub-millimeter Galaxies at ∼200 pc Resolution: The Absence of Large Clumps in the Interstellar Medium at High-redshift

“…Figure 2 shows the moment-zero maps with a uv-taper of 500 kλ (0 17×0 16) and compares the recovered [C II] emission to the spectra from the lower-resolution observations from ALMA Cycles 0 and 1 (Swinbank et al 2012;De Breuck et al 2014). Emission from [C II] was detected for UDS 47.0 as a very broad line at ∼351 GHz in the shallower 0 3 data from ALMA Cycle 1 (Simpson et al 2015b(Simpson et al , 2017. In our deeper 0 03 resolution observations, we detect a broad ∼4σ [C II] emission line.…”

“…A pilot study observed the 30 brightest SCUBA-2 sources in the ∼1 deg 2 UKIDSS/UDS field (Simpson et al 2015a(Simpson et al , 2015b(Simpson et al , 2017. These 0 3 resolution ALMA observations revealed a serendipitous detection of [C II] emission at 350.78 GHz, establishing the redshift as z=4.420.…”

“…We adopt an average dust temperature of T d =50±4 K, a dust emissivity index of 19 The numerical identifier for this SCUBA-2 source from Simpson et al (2017) changed in the final version of the S2CLS UDS catalog (Geach et al 2017) with the source corresponding to UDS0051 in that work. This ALMA identified SMG is cataloged as AS2UDS0051.0 in S. Stach et al (2018, in preparation) 2 β=1.5, and assume the dust is optically thick at λ=70 μm.…”

A Machine-learning Method for Identifying Multiwavelength Counterparts of Submillimeter Galaxies: Training and Testing Using AS2UDS and ALESS

“…Although such strongly star-forming galaxies are rare in the local universe, the space density of bright SMGs (i.e., S 850μm >1 mJy, corresponding to a far-infrared luminosity, L IR 10 12 L  ) increases rapidly with look-back time and appears to peak at z∼2-3 (e.g., Barger et al 1999;Chapman et al 2005;Smolčić et al 2012;Yun et al 2012;Simpson et al 2014). Due to their potentially rapid formation, SMGs have been proposed to be the progenitors of spheroidal galaxies in the local universe (e.g., Lilly et al 1999;Swinbank et al 2006;Simpson et al 2014Simpson et al , 2017. They are also thought to be linked to quasi-stellar object (QSO) activity due the similarity of their redshift distribution to that of luminous QSOs (e.g., Coppin et al 2008), as well as being linked to compact red galaxies seen at z∼1-2 (e.g., Cimatti et al 2008;Whitaker et al 2012;Toft et al 2014).…”

“…With angular resolution better than 1″ and thus subarcsecond positional precision, we are starting to obtain a more complete understanding of the multiwavelength characteristics of SMGs (e.g., Hodge et al 2013;Swinbank et al 2014Swinbank et al , 2015Thomson et al 2014;Aravena et al 2016;Walter et al 2016;Danielson et al 2017;Dunlop et al 2017;Simpson et al 2017;Wardlow et al 2017). However, for single-dish submillimeter surveys of fields in the northern sky, it is not possible to perform ALMA follow-up, and so we must rely instead on the use of the Submillimeter Array (SMA) or IRAM's Northern Extended Millimetre Array (NOEMA) to obtain interferometric identifications (e.g., Smolčić et al 2012;Hill et al 2018).…”