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1601. S2COSMOS: bright SCUBA-2 submm sources in COSMOS
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.
1602. SCUBA-2 Ambitious Sky Survey
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.
1603. SCUBA-2 cosmology legacy survey
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.
1604. SCUBA-2 Cosmology Legacy Survey
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 .
1605. SCUBA-2 EGS deep field
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.
1606. SCUBA Half-Degree Extragalactic Survey. I.
ID:
ivo://CDS.VizieR/J/MNRAS/363/563
Title:
SCUBA Half-Degree Extragalactic Survey. I.
Short Name:
J/MNRAS/363/563
Date:
21 Oct 2021
Publisher:
CDS
Description:
The Submillimetre Common-User Bolometer Array (SCUBA) Half-Degree Extragalactic Survey (SHADES) is a major new blank-field extragalactic submillimetre (submm) survey currently underway at the James Clerk Maxwell Telescope (JCMT). Ultimately, SHADES aims to cover half a square degree at 450 and 850um to a 4 depth of 8umJy at 850um. Two fields are being observed, the Subaru/XMMNewton Deep Field (SXDF) (02h18m +05{deg}) and the Lockman Hole East (10h52m+ 57{deg}). The survey has three main aims: (i) to investigate the population of high-redshift submm galaxies and the cosmic history of massive dust-enshrouded star formation activity; (ii) to investigate the clustering properties of submm-selected galaxies in order to determine whether these objects could be progenitors of present-day massive ellipticals; and (iii) to investigate the fraction of submm-selected sources that harbour active galactic nuclei. To achieve these aims requires that the submm data be combined with co-spatial information spanning the radio-to-X-ray frequency range. Accordingly, SHADES has been designed to benefit from ultra-deep radio imaging obtained with the Very Large Array (VLA), deep mid-infrared observations from the Spitzer Space Telescope, submm mapping by the Balloon-borne Large Aperture Submillimetre Telescope (BLAST), deep near-infrared imaging with the United Kingdom Infrared Telescope, deep optical imaging with the Subaru Telescope and deep X-ray observations with the XMMNewton observatory.
1607. SCUBA Half-Degree Extragalactic Survey. II
ID:
ivo://CDS.VizieR/J/MNRAS/372/1621
Title:
SCUBA Half-Degree Extragalactic Survey. II
Short Name:
J/MNRAS/372/1621
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present maps, source catalogue and number counts of the largest, most complete and unbiased extragalactic submillimetre survey: the 850-m SCUBA Half-Degree Extragalactic Survey (SHADES). Using the Submillimetre Common-User Bolometer Array (SCUBA) on the James Clerk Maxwell Telescope (JCMT), SHADES mapped two separate regions of sky: the Subaru/XMM-Newton Deep Field (SXDF) and the Lockman Hole East (LH). Encompassing 93 per cent of the overall acquired data (i.e. data taken up to 2004 February 1), these SCUBA maps cover 720arcmin^2^ with a rms noise level of about 2mJy and have uncovered >100 submillimetre galaxies. In order to ensure the utmost robustness of the resulting source catalogue, data reduction was independently carried out by four subgroups within the SHADES team, providing an unprecedented degree of reliability with respect to other SCUBA catalogues available from the literature. Individual source lists from the four groups were combined to produce a robust 120-object SHADES catalogue; an invaluable resource for follow-up campaigns aiming to study the properties of a complete and consistent sample of submillimetre galaxies. For the first time, we present deboosted flux densities for each submillimetre galaxy found in a large survey. Extensive simulations and tests were performed separately by each group in order to confirm the robustness of the source candidates and to evaluate the effects of false detections, completeness and flux density boosting. Corrections for these effects were then applied to the data to derive the submillimetre galaxy source counts. SHADES has a high enough number of detected sources that meaningful differential counts can be estimated, unlike most submillimetre surveys which have to consider integral counts. We present differential and integral source number counts and find that the differential counts are better fit with a broken power law or a Schechter function than with a single power law; the SHADES data alone significantly show that a break is required at several mJy, although the precise position of the break is not well constrained. We
1608. SDSS and DES long-term extreme variability QSOs
ID:
ivo://CDS.VizieR/J/ApJ/854/160
Title:
SDSS and DES long-term extreme variability QSOs
Short Name:
J/ApJ/854/160
Date:
21 Oct 2021
Publisher:
CDS
Description:
We perform a systematic search for long-term extreme variability quasars (EVQs) in the overlapping Sloan Digital Sky Survey and 3 Year Dark Energy Survey imaging, which provide light curves spanning more than 15 years. We identified ~1000 EVQs with a maximum change in g-band magnitude of more than 1 mag over this period, about 10% of all quasars searched. The EVQs have L_bol_~10^45^-10^47^erg/s and L/L_Edd_~0.01-1. Accounting for selection effects, we estimate an intrinsic EVQ fraction of ~30%-50% among all g<~22 quasars over a baseline of ~15yr. We performed detailed multi-wavelength, spectral, and variability analyses for the EVQs and compared them to their parent quasar sample. We found that EVQs are distinct from a control sample of quasars matched in redshift and optical luminosity: (1) their UV broad emission lines have larger equivalent widths; (2) their Eddington ratios are systematically lower; and (3) they are more variable on all timescales. The intrinsic difference in quasar properties for EVQs suggests that internal processes associated with accretion are the main driver for the observed extreme long-term variability. However, despite their different properties, EVQs seem to be in the tail of a continuous distribution of quasar properties, rather than standing out as a distinct population. We speculate that EVQs are normal quasars accreting at relatively low rates, where the accretion flow is more likely to experience instabilities that drive the changes in flux by a factor of a few on multi-year timescales.
1609. SDSS automated morphology classification
ID:
ivo://CDS.VizieR/J/A+A/525/A157
Title:
SDSS automated morphology classification
Short Name:
J/A+A/525/A157
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present an automated morphological classification in 4 types (E, S0, Sab, Scd) of ~700 000 galaxies from the SDSS DR7 spectroscopic sample based on support vector machines. The main new property of the classification is that we associate a probability to each galaxy of being in the four morphological classes instead of assigning a single class. The classification is therefore better adapted to nature where we expect a continuous transition between different morphological types. The algorithm is trained with a visual classification and then compared to several independent visual classifications including the Galaxy Zoo first-release catalog. We find a very good correlation between the automated classification and classical visual ones.
1610. SDSS/BOSS/TDSS CIV BAL quasars
ID:
ivo://CDS.VizieR/J/ApJ/824/130
Title:
SDSS/BOSS/TDSS CIV BAL quasars
Short Name:
J/ApJ/824/130
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present results from the largest systematic investigation of broad absorption line (BAL) acceleration to date. We use spectra of 140 quasars from three Sloan Digital Sky Survey programs to search for global velocity offsets in BALs over timescales of ~2.5-5.5 years in the quasar rest frame. We carefully select acceleration candidates by requiring monolithic velocity shifts over the entire BAL trough, avoiding BALs with velocity shifts that might be caused by profile variability. The CIV BALs of two quasars show velocity shifts consistent with the expected signatures of BAL acceleration, and the BAL of one quasar shows a velocity-shift signature of deceleration. In our two acceleration candidates, we see evidence that the magnitude of the acceleration is not constant over time; the magnitudes of the change in acceleration for both acceleration candidates are difficult to produce with a standard disk-wind model or via geometric projection effects. We measure upper limits to acceleration and deceleration for 76 additional BAL troughs and find that the majority of BALs are stable to within about 3% of their mean velocities. The lack of widespread acceleration/deceleration could indicate that the gas producing most BALs is located at large radii from the central black hole and/or is not currently strongly interacting with ambient material within the host galaxy along our line of sight.

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