- ID:
- ivo://CDS.VizieR/J/A+A/582/A66
- Title:
- SABOCA NGC 3603 IRS 9A images
- Short Name:
- J/A+A/582/A66
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The formation of massive stars and their arrival on the zero-age main-sequence occurs hidden behind dense clouds of gas and dust. In the giant HII region NGC 3603, the radiation of a young cluster of OB stars has dispersed dust and gas in its vicinity. At a projected distance of 2.5pc from the cluster, a bright mid-infrared (mid-IR) source (IRS 9A) was identified as a massive young stellar object (MYSO), located on the side of a molecular clump (MM2) of gas facing the cluster. We investigated the physical conditions in MM2, based on APEX sub-mm observations using the SABOCA and SHFI instruments, and archival ATCA 3mm continuum and CS spectral line data. We resolved MM2 into several compact cores, one of them closely associated with IRS 9A. These are likely to be infrared dark clouds because they do not show the typical hot-core emission lines and are mostly opaque against the mid-IR background. The compact cores have masses of up to several hundred times the solar mass and gas temperatures of about 50K, without evidence of internal ionizing sources. We speculate that IRS 9A is younger than the cluster stars, but is in an evolutionary state after the compact cores.
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- ID:
- ivo://CDS.VizieR/J/A+A/631/A72
- Title:
- SABOCA 350um view of ATLASGAL-selected massive clumps
- Short Name:
- J/A+A/631/A72
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The structure formation of the dense interstellar material and the fragmentation of clumps into cores is a fundamental step to understand how stars and stellar clusters form. We aim to establish a statistical view of clump fragmentation at sub-parsec scales based on a large sample of massive clumps selected from the ATLASGAL survey. We used the APEX/SABOCA camera at 350um to image clumps at a resolution of 8.5", corresponding to physical scales of <0.2pc at a distance <5kpc. The majority of the sample consists of massive clumps that are weak or in absorption at 24um. We resolve spherical and filamentary structures and identify the population of compact sources. Complemented with archival Herschel data, we derive the physical properties, such as dust temperature, mass and bolometric luminosity of clumps and cores. We use association with mid-infrared 22-24 m and 70 m point sources to pin down the star formation activity of the cores. We then statistically assess their physical properties, and the fragmentation characteristics of massive clumps. We detect emission at 350um towards all targets and find that it typically exhibits a filamentary(-like) morphology and hosts a population of compact sources. Using Gaussclumps we identify 1120 compact sources and derive the physical parameters and star formation activity for 971 of these, 874 of which are associated with 444 clumps. We find a moderate correlation between the clump fragmentation levels with the clump gas density and the predicted number of fragments with pure Jeans fragmentation scenario. We find a strong correlation between the mass of the most massive fragment and the total clump mass, suggesting that the self-gravity may play an important role in the clumps' small scale structure formation. Finally, due to the improved angular resolution compared to ATLASGAL, we are able to identify 27 massive quiescent cores with M_core_>100M_{sun}_ within 5kpc; these are massive enough to be self-gravitating but do not yet show any sign of star-formation. This sample comprises, therefore, promising candidates of massive pre-stellar cores, or deeply embedded high-mass protostars. The submillimeter observations of the massive clumps that are weak or completely dark at 24um reveal rich filamentary structures and an embedded population of compact cores. The maximum core mass is likely determined by the self-gravity of the clump. The rarity of massive pre-stellar core candidates implies short collapse time-scales for dense structures.
- ID:
- ivo://CDS.VizieR/J/ApJ/820/82
- Title:
- S2CLS: multiwavelength counterparts to SMGs
- Short Name:
- J/ApJ/820/82
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present multiwavelength identifications for the counterparts of 1088 submillimeter sources detected at 850{mu}m in the SCUBA-2 Cosmology Legacy Survey (S2CLS) study of the UKIRT Infrared Deep Sky Survey-Ultra-Deep Survey (UDS) field. By utilizing an Atacama Large Millimeter Array (ALMA) pilot study on a subset of our bright SCUBA-2 sample as a training set, along with the deep optical-near-infrared (OIR) data available in this field, we develop a novel technique, Optical-IR Triple Color (OIRTC), using z-K, K-[3.6], [3.6]-[4.5] colors to select the candidate submillimeter galaxy (SMG) counterparts. By combining radio identification and the OIRTC technique, we find counterpart candidates for 80% of the Class = 1 >=4{sigma} SCUBA-2 sample, defined as those that are covered by both radio and OIR imaging and the base sample for our scientific analyses. Based on the ALMA training set, we expect the accuracy of these identifications to be 82%+/-20%, with a completeness of 69%+/-16%, essentially as accurate as the traditional p-value technique but with higher completeness. We find that the fraction of SCUBA-2 sources having candidate counterparts is lower for fainter 850{mu}m sources, and we argue that for follow-up observations sensitive to SMGs with S_850_>~1mJy across the whole ALMA beam, the fraction with multiple counterparts is likely to be >40% for SCUBA-2 sources at S_850_>~4mJy. We find that the photometric redshift distribution for the SMGs is well fit by a lognormal distribution, with a median redshift of z=2.3+/-0.1. After accounting for the sources without any radio and/or OIRTC counterpart, we estimate the median redshift to be z=2.6+/-0.1 for SMGs with S_850_>1mJy. We also use this new large sample to study the clustering of SMGs and the far-infrared properties of the unidentified submillimeter sources by stacking their Herschel SPIRE far-infrared emission.
- ID:
- ivo://CDS.VizieR/J/ApJ/880/43
- Title:
- S2COSMOS: bright SCUBA-2 submm sources in COSMOS
- Short Name:
- J/ApJ/880/43
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present sensitive 850{mu}m imaging of the Cosmological Evolution Survey (COSMOS) field using 640hr of new and archival observations taken with SCUBA-2 at the East Asian Observatory's James Clerk Maxwell Telescope. The SCUBA-2 COSMOS survey (S2COSMOS) achieves a median noise level of {sigma}_850{mu}m_=1.2mJy/beam over an area of 1.6deg^2^ (MAIN; Hubble Space Telescope/Advanced Camera for Surveys footprint), and {sigma}_850{mu}m_=1.7mJy/beam over an additional 1deg^2^ of supplementary (supp) coverage. We present a catalog of 1020 and 127 sources detected at a significance level of >4{sigma} and >4.3{sigma} in the main and supp regions, respectively, corresponding to a uniform 2% false-detection rate. We construct the single-dish 850{mu}m number counts at S_850_>2mJy and show that these S2COSMOS counts are in agreement with previous single-dish surveys, demonstrating that degree-scale fields are sufficient to overcome the effects of cosmic variance in the S_850_=2-10mJy population. To investigate the properties of the galaxies identified by S2COSMOS sources we measure the surface density of near-infrared-selected galaxies around their positions and identify an average excess of 2.0+/-0.2 galaxies within a 13" radius (~100kpc at z~2). The bulk of these galaxies represent near-infrared-selected submillimeter galaxies and/or spatially correlated sources and lie at a median photometric redshift of z=2.0+/-0.1. Finally, we perform a stacking analysis at submillimeter and far-infrared wavelengths of stellar-mass-selected galaxies (M_*_=10^10^-10^12^M_{sun}_) from z=0-4, obtaining high-significance detections at 850{mu}m in all subsets (signal-to-noise ratio, S/N=4-30), and investigate the relation between far-infrared luminosity, stellar mass, and the peak wavelength of the dust spectral energy distribution. The publication of this survey adds a new deep, uniform submillimeter layer to the wavelength coverage of this well-studied COSMOS field.
- ID:
- ivo://CDS.VizieR/J/MNRAS/468/250
- Title:
- SCUBA-2 Ambitious Sky Survey
- Short Name:
- J/MNRAS/468/250
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The SCUBA-2 Ambitious Sky Survey (SASSy) is composed of shallow 850-{mu}m imaging using the Submillimetre Common-User Bolometer Array 2 (SCUBA-2) on the James Clerk Maxwell Telescope. Here we describe the extraction of a catalogue of beam-sized sources from a roughly 120deg^2^ region of the Galactic plane mapped uniformly (to an rms level of about 40mJy), covering longitude 120{deg}<l<140{deg} and latitude |b|<2.9{deg}. We used a matched-filtering approach to increase the signal-to-noise ratio (S/N) in these noisy maps and tested the efficiency of our extraction procedure through estimates of the false discovery rate, as well as by adding artificial sources to the real images. The primary catalogue contains a total of 189 sources at 850{mu}m, down to an S/N threshold of approximately 4.6. Additionally, we list 136 sources detected down to S/N=4.3, but recognize that as we go lower in S/N, the reliability of the catalogue rapidly diminishes. We perform follow-up observations of some of our lower significance sources through small targeted SCUBA-2 images and list 265 sources detected in these maps down to S/N=5. This illustrates the real power of SASSy: inspecting the shallow maps for regions of 850-{mu}m emission and then using deeper targeted images to efficiently find fainter sources. We also perform a comparison of the SASSy sources with the Planck Catalogue of Compact Sources and the IRAS Point Source Catalogue, to determine which sources discovered in this field might be new, and hence potentially cold regions at an early stage of star formation.
- ID:
- ivo://CDS.VizieR/J/MNRAS/436/430
- Title:
- SCUBA-2 cosmology legacy survey
- Short Name:
- J/MNRAS/436/430
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We investigate the multiwavelength properties of a sample of 450-{mu}m-selected sources from the SCUBA-2 Cosmology Legacy Survey. A total of 69 sources were identified above 4{sigma} in deep SCUBA-2 450-{mu}m observations overlapping the UDS and COSMOS fields and covering 210arcmin^2^ to a typical depth of {sigma}_450_=1.5mJy. Reliable cross-identifications are found for 58 sources (84 percent) in Spitzer and Hubble Space Telescope WFC3/IR data. The photometric redshift distribution (dN/dz) of 450-{mu}m-selected sources is presented, showing a broad peak in the redshift range 1<z<3 and a median of z=1.4. Combining the SCUBA-2 photometry with Herschel SPIRE data from HerMES, the submm spectral energy distribution (SED) is examined via the use of modified blackbody fits, yielding aggregate values for the IR luminosity, dust temperature and emissivity of <L_IR_>=10^12^+/-0.8L_{sun}_, <T_D_>=42+/-11K and <{beta}_D_>=1.6+/-0.5, respectively. The relationship between these SED parameters and the physical properties of galaxies is investigated, revealing correlations between T_D_ and L_IR_ and between {beta}D and both stellar mass and effective radius. The connection between the star formation rate (SFR) and stellar mass is explored, with 24 percent of 450-{mu}m sources found to be `starbursts', i.e. displaying anomalously high specific SFRs. However, both the number density and observed properties of these `starburst' galaxies are found to be consistent with the population of normal star-forming galaxies.
- ID:
- ivo://CDS.VizieR/J/MNRAS/465/1789
- Title:
- SCUBA-2 Cosmology Legacy Survey
- Short Name:
- J/MNRAS/465/1789
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a catalogue of ~3000 submillimetre sources detected (>=3.5{sigma}) at 850um over ~5deg^2^ surveyed as part of the James Clerk Maxwell Telescope (JCMT) SCUBA-2 Cosmology Legacy Survey (S2CLS). This is the largest survey of its kind at 850um, increasing the sample size of 850um selected submillimetre galaxies by an order of magnitude. The wide 850um survey component of S2CLS covers the extragalactic fields: UKIDSS-UDS, COSMOS, Akari-NEP, Extended Groth Strip, Lockman Hole North, SSA22 and GOODS-North. The average 1{sigma} depth of S2CLS is 1.2mJy/beam, approaching the SCUBA-2 850um confusion limit, which we determine to be {sigma}_c_~=0.8mJy/beam. We measure the 850um number counts, reducing the Poisson errors on the differential counts to approximately 4 per cent at S850~=3mJy. With several independent fields, we investigate field-to-field variance, finding that the number counts on 0.5{deg}-1{deg} scales are generally within 50 per cent of the S2CLS mean for S850>3mJy, with scatter consistent with the Poisson and estimated cosmic variance uncertainties, although there is a marginal (2{sigma}) density enhancement in GOODS-North. The observed counts are in reasonable agreement with recent phenomenological and semi-analytic models, although determining the shape of the faint-end slope (S850<3mJy) remains a key test. The large solid angle of S2CLS allows us to measure the bright-end counts: at S850>10mJy there are approximately 10 sources per square degree, and we detect the distinctive up-turn in the number counts indicative of the detection of local sources of 850um emission, and strongly lensed high-redshift galaxies. All calibrated maps and the catalogue are made publicly available at https://zenodo.org/record/57792#.W41TsRg68eM .
- ID:
- ivo://CDS.VizieR/J/MNRAS/464/3369
- Title:
- SCUBA-2 EGS deep field
- Short Name:
- J/MNRAS/464/3369
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present deep observations at 450 and 850{mu}m in the Extended Groth Strip field taken with the SCUBA-2 camera mounted on the James Clerk Maxwell Telescope as part of the deep SCUBA-2 Cosmology Legacy Survey (S2CLS), achieving a central instrumental depth of {sigma}_450_=1.2mJy/beam and {sigma}_850_=0.2mJy/beam. We detect 57 sources at 450{mu}m and 90 at 850{mu}m with signal-to-noise ratio >3.5 over ~70arcmin^2^. From these detections, we derive the number counts at flux densities S_450_>4.0mJy and S_850_>0.9mJy, which represent the deepest number counts at these wavelengths derived using directly extracted sources from only blank-field observations with a single-dish telescope. Our measurements smoothly connect the gap between previous shallower blank-field single-dish observations and deep interferometric ALMA results. We estimate the contribution of our SCUBA-2 detected galaxies to the cosmic infrared background (CIB), as well as the contribution of 24{mu}m-selected galaxies through a stacking technique, which add a total of 0.26+/-0.03 and 0.07+/-0.01MJy/sr, at 450 and 850{mu}m, respectively. These surface brightnesses correspond to 60+/-20 and 50+/-20 per cent of the total CIB measurements, where the errors are dominated by those of the total CIB. Using the photometric redshifts of the 24{mu}m-selected sample and the redshift distributions of the submillimetre galaxies, we find that the redshift distribution of the recovered CIB is different at each wavelength, with a peak at z~1 for 450{mu}m and at z~2 for 850{mu}m, consistent with previous observations and theoretical models.
- ID:
- ivo://CDS.VizieR/J/ApJS/234/22
- Title:
- SCUBA-2 Galactic Center compact source catalog
- Short Name:
- J/ApJS/234/22
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present new JCMT SCUBA-2 observations of the Galactic Center region from 355{deg}<l<5{deg} and b<+/-1{deg}, covering 10x2 square degrees along the Galactic Plane to a depth of 43mJy/beam at 850{mu}m and 360mJy/beam at 450{mu}m. We describe the mapping strategy and reduction method used. We present ^12^CO(3-2) observations of selected regions in the field. We derive the molecular-line conversion factors (mJy/beam per K.km/s) at 850 and 450{mu}m, which are then used to obtain the amount of contamination in the continuum maps due to ^12^CO(3-2) emission in the 850{mu}m band. Toward the fields where the CO contamination has been accounted for, we present an 850{mu}m CO-corrected compact source catalog. Finally, we look for possible physical trends in the CO contamination with respect to column density, mass, and concentration. No trends were seen in the data despite the recognition of three contributors to CO contamination: opacity, shocks, and temperature, which would be expected to relate to physical conditions. These SCUBA-2 Galactic Center data are available via http://doi.org/10.11570/17.0009.
- ID:
- ivo://CDS.VizieR/J/MNRAS/458/4321
- Title:
- SCUBA-2 galaxies in 850um survey
- Short Name:
- J/MNRAS/458/4321
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We investigate the properties of the galaxies selected from the deepest 850-{mu}m survey undertaken to date with (Submillimetre Common-User Bolometer Array 2) SCUBA-2 on the James Clerk Maxwell Telescope as part of the SCUBA-2 Cosmology Legacy Survey. A total of 106 sources (>5{sigma}) were uncovered at 850{mu}m from an area of ~=150 arcmin^2^ in the centre of the COSMOS/UltraVISTA/Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey (CANDELS) field, imaged to a typical depth of {sigma}_850_~=0.25mJy. We utilize the available multifrequency data to identify galaxy counterparts for 80 of these sources (75 per cent), and to establish the complete redshift distribution for this sample, yielding . We have also been able to determine the stellar masses of the majority of the galaxy identifications, enabling us to explore their location on the star formation rate:stellar mass (SFR:M*) plane. Crucially, our new deep 850-{mu}m-selected sample reaches flux densities equivalent to SFR~=100M_{sun}_/yr, enabling us to confirm that sub-mm galaxies form the high-mass end of the 'main sequence' (MS) of star-forming galaxies at z>1.5 (with a mean specific SFR of sSFR=2.25+/-0.19Gyr^-1^ at z~=2.5). Our results are consistent with no significant flattening of the MS towards high masses at these redshifts. However, our results add to the growing evidence that average sSFR rises only slowly at high redshift, resulting in log_10_sSFR being an apparently simple linear function of the age of the Universe.
