| 1. |
- Geach, J.E., et al.
(författare)
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The SCUBA-2 Cosmology Legacy Survey: 850 μm maps, catalogues and number counts
- 2017
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Ingår i: Monthly Notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 465:2, s. 1789-1806
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Tidskriftsartikel (refereegranskat)abstract
- We present a catalogue of similar to 3000 submillimetre sources detected (>= 3.5 sigma) at 850 mu m over similar to 5 deg(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 850 mu m, increasing the sample size of 850 mu m selected submillimetre galaxies by an order of magnitude. The wide 850 mu m 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 1s depth of S2CLS is 1.2 mJy beam(-1), approaching the SCUBA-2 850 mu m confusion limit, which we determine to be sigma(c) approximate to 0.8 mJy beam(-1). We measure the 850 mu m number counts, reducing the Poisson errors on the differential counts to approximately 4 per cent at S-850 approximate to 3 mJy. With several independent fields, we investigate field-to-field variance, finding that the number counts on 0.5 degrees-1 degrees scales are generally within 50 per cent of the S2CLS mean for S-850 > 3 mJy, 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 (S-850 < 3 mJy) remains a key test. The large solid angle of S2CLS allows us to measure the bright-end counts: at S-850 > 10 mJy 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 850 mu m emission
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| 2. |
- Geach, J.E., et al.
(författare)
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The SCUBA-2 Cosmology Legacy Survey: blank-field number counts of 450-mu m-selected galaxies and their contribution to the cosmic infrared background
- 2013
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Ingår i: Monthly Notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 432:1, s. 53-61
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Tidskriftsartikel (refereegranskat)abstract
- The first deep blank-field 450 mu m map (1 sigma approximate to 1.3 mJy) from the Submillimetre Common-User Bolometer Array-2 SCUBA-2 Cosmology Legacy Survey (S2CLS), conducted with the James Clerk Maxwell Telescope (JCMT) is presented. Our map covers 140 arcmin(2) of the Cosmological Evolution Survey field, in the footprint of the Hubble Space Telescope (HST) Cosmic Assembly Near-Infrared Deep Extragalactic Legacy Survey. Using 60 submillimetre galaxies detected at >= 3.75s, we evaluate the number counts of 450-mu m-selected galaxies with flux densities S-450 > 5 mJy. The 8 arcsec JCMT beam and high sensitivity of SCUBA-2 now make it possible to directly resolve a larger fraction of the cosmic infrared background (CIB, peaking at. similar to 200 mu m) into the individual galaxies responsible for its emission than has previously been possible at this wavelength. At S450 > 5 mJy, we resolve (7.4 +/- 0.7) x 10(-2) MJy sr(-1) of the CIB at 450 mu m (equivalent to 16 +/- 7 per cent of the absolute brightness measured by the Cosmic Background Explorer at this wavelength) into point sources. A further similar to 40 per cent of the CIB can be recovered through a statistical stack of 24 mu m emitters in this field, indicating that the majority (approximate to 60 per cent) of the CIB at 450 mu m is emitted by galaxies with S450 > 2 mJy. The average redshift of 450 mu m emitters identified with an optical/near-infrared counterpart is estimated to be = 1.3, implying that the galaxies in the sample are in the ultraluminous class (LIR approximate to 1.1 x 1012 L approximate to). If the galaxies contributing to the statistical stack lie at similar redshifts, then the majority of the CIB at 450 mu m is emitted by galaxies in the luminous infrared galaxy (LIRG) class with LIR > 3.6 x 1011 L-circle dot.
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| 3. |
- Hodge, J. A., et al.
(författare)
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An ALMA Survey of Submillimeter Galaxies in the Extended Chandra Deep Field South: Source Catalog and Multiplicity
- 2013
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Ingår i: Astrophysical Journal. - 1538-4357 .- 0004-637X. ; 768:1
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Tidskriftsartikel (refereegranskat)abstract
- We present an Atacama Large Millimeter/submillimeter Array (ALMA) Cycle 0 survey of 126 submillimeter sources from the LABOCA ECDFS Submillimeter Survey (LESS). Our 870 mu m survey with ALMA (ALESS) has produced maps similar to 3x deeper and with a beam area similar to 200x smaller than the original LESS observations, doubling the current number of interferometrically-observed submillimeter sources. The high resolution of these maps allows us to resolve sources that were previously blended and accurately identify the origin of the submillimeter emission. We discuss the creation of the ALESS submillimeter galaxy (SMG) catalog, including the main sample of 99 SMGs and a supplementary sample of 32 SMGs. We find that at least 35% (possibly up to 50%) of the detected LABOCA sources have been resolved into multiple SMGs, and that the average number of SMGs per LESS source increases with LESS flux density. Using the (now precisely known) SMG positions, we empirically test the theoretical expectation for the uncertainty in the single-dish source positions. We also compare our catalog to the previously predicted radio/mid-infrared counterparts, finding that 45% of the ALESS SMGs were missed by this method. Our similar to 1 ''.6 resolution allows us to measure a size of similar to 9 kpc x 5 kpc for the rest-frame similar to 300 mu m emission region in one resolved SMG, implying a star formation rate surface density of 80 M-circle dot yr(-1) kpc(-2), and we constrain the emission regions in the remaining SMGs to be
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| 4. |
- Hodge, J. A., et al.
(författare)
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Kiloparsec-Scale Dust Disks in High-Redshift Luminous Submillimeter Galaxies
- 2016
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Ingår i: Astrophysical Journal. - : American Astronomical Society. - 1538-4357 .- 0004-637X. ; 833:1
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Tidskriftsartikel (refereegranskat)abstract
- We present high-resolution (0 ''.6) 870 mu m Atacama Large Millimeter/submillimeter Array (ALMA) imaging of 16 luminous (LIR similar to 4 x 10(12) L-circle dot) submillimeter galaxies (SMGs) from the ALESS survey of the Extended Chandra Deep Field South. This dust imaging traces the dust-obscured star formation in these z similar to 2.5 galaxies on similar to 1.3 kpc scales. The emission has a median effective radius of R-e = 0 ''.24 +/- 0 ''.02, corresponding to a typical physical size of R-e= 1.8 +/- 0.2 kpc. We derive a median Sersic index of n = 0.9 +/- 0.2, implying that the dust emission is remarkably disk-like at the current resolution and sensitivity. We use different weighting schemes with the visibilities to search for clumps on 0 ''.12. (similar to 1.0 kpc) scales, but we find no significant evidence for clumping in the majority of cases. Indeed, we demonstrate using simulations that the observed morphologies are generally consistent with smooth exponential disks, suggesting that caution should be exercised when identifying candidate clumps in even moderate signal-to-noise ratio interferometric data. We compare our maps to comparable-resolution Hubble Space Telescope H-160-band images, finding that the stellar morphologies appear significantly more extended and disturbed, and suggesting that major mergers may be responsible for driving the formation of the compact dust disks we observe. The stark contrast between the obscured and unobscured morphologies may also have implications for SED fitting routines that assume the dust is co-located with the optical/near-IR continuum emission. Finally, we discuss the potential of the current bursts of star formation to transform the observed galaxy sizes and light profiles, showing that the z similar to 0 descendants of these SMGs are expected to have stellar masses, effective radii, and gas surface densities consistent with the most compact massive (M* similar to 1-2 x 10(11) M-circle dot) early-type galaxies observed locally.
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| 5. |
- Karim, A., et al.
(författare)
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An ALMA survey of submillimetre galaxies in the Extended Chandra Deep Field South: high-resolution 870 mu m source counts
- 2013
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Ingår i: Monthly Notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 432:1, s. 2-9
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Tidskriftsartikel (refereegranskat)abstract
- We report the first counts of faint submillimetre galaxies (SMGs) in the 870-mu m band derived from arcsecond-resolution observations with the Atacama Large Millimeter Array (ALMA). We have used ALMA to map a sample of 122 870-mu m-selected submillimetre sources drawn from the 0 degrees.5x0 degrees.5 the Large Apex BOlometer CAmera (LABOCA) Extended Chandra Deep Field South submillimetre survey (LESS). These ALMA maps have an average depth of sigma 870(mu m) similar to 0.4 mJy, some approximately three times deeper than the original LABOCA survey and critically the angular resolution is more than an order of magnitude higher, FWHM of similar to 1.5 arcsec compared to similar to 19 arcsec for the LABOCA discovery map. This combination of sensitivity and resolution allows us to precisely pinpoint the SMGs contributing to the submillimetre sources from the LABOCA map, free from the effects of confusion. We show that our ALMA-derived SMG counts broadly agree with the submillimetre source counts from previous, lower resolution single-dish surveys, demonstrating that the bulk of the submillimetre sources are not caused by blending of unresolved SMGs. The difficulty which well-constrained theoretical models have in reproducing the high surface densities of SMGs, thus remains. However, our observations do show that all of the very brightest sources in the LESS sample, S-870 (mu m) greater than or similar to 12 mJy, comprise emission from multiple, fainter SMGs, each with 870-mu m fluxes of less than or similar to 9 mJy. This implies a natural limit to the star formation rate in SMGs of less than or similar to 10(3) M-circle dot yr(-1), which in turn suggests that the space densities of z > 1 galaxies with gas masses in excess of similar to 5 x 10(10) M-circle dot is
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| 6. |
- Simpson, J. M., et al.
(författare)
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AN ALMA SURVEY OF SUBMILLIMETER GALAXIES IN THE EXTENDED CHANDRA DEEP FIELD SOUTH: THE REDSHIFT DISTRIBUTION AND EVOLUTION OF SUBMILLIMETER GALAXIES
- 2014
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Ingår i: Astrophysical Journal. - : American Astronomical Society. - 1538-4357 .- 0004-637X. ; 788:2
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Tidskriftsartikel (refereegranskat)abstract
- We present the first photometric redshift distribution for a large sample of 870 mu m submillimeter galaxies (SMGs) with robust identifications based on observations with ALMA. In our analysis we consider 96 SMGs in the Extended Chandra Deep Field South, 77 of which have 4-19 band photometry. We model the SEDs for these 77 SMGs, deriving a median photometric redshift of z(phot) = 2.3 +/- 0.1. The remaining 19 SMGs have insufficient photometry to derive photometric redshifts, but a stacking analysis of Herschel observations confirms they are not spurious. Assuming that these SMGs have an absolute H-band magnitude distribution comparable to that of a complete sample of z similar to 1-2 SMGs, we demonstrate that they lie at slightly higher redshifts, raising the median redshift for SMGs to zphot = 2.5 +/- 0.2. Critically we show that the proportion of galaxies undergoing an SMG-like phase at z >= 3 is at most 35% +/- 5% of the total population. We derive a median stellar mass of M star = (8 +/- 1) x 10(10) M circle dot, although there are systematic uncertainties of up to 5 x for individual sources. Assuming that the star formation activity in SMGs has a timescale of similar to 100 Myr, we show that their descendants at z similar to 0 would have a space density and MH distribution that are in good agreement with those of local ellipticals. In addition, the inferred mass-weighted ages of the local ellipticals broadly agree with the look-back times of the SMG events. Taken together, these results are consistent with a simple model that identifies SMGs as events that form most of the stars seen in the majority of luminous elliptical galaxies at the present day.
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| 7. |
- Stanley, Flora, 1990, et al.
(författare)
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The mean star formation rates of unobscured QSOs: searching for evidence of suppressed or enhanced star formation
- 2017
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Ingår i: Monthly Notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 472:2, s. 2221-2240
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Tidskriftsartikel (refereegranskat)abstract
- We investigate the mean star formation rates (SFRs) in the host galaxies of similar to 3000 optically selected quasi-stellar objects (QSOs) from the Sloan Digital Sky Survey within the Herschel-ATLAS fields, and a radio-luminous subsample covering the redshift range of z = 0.2-2.5. Using Wide-field Infrared Survey Explorer (WISE) and Herschel photometry (12-500 mu m) we construct composite spectral energy distributions (SEDs) in bins of redshift and active galactic nucleus (AGN) luminosity. We perform SED fitting to measure the mean infrared luminosity due to star formation, removing the contamination from AGN emission. We find that the mean SFRs show a weak positive trend with increasing AGN luminosity. However, we demonstrate that the observed trend could be due to an increase in black hole (BH) mass (and a consequent increase of inferred stellar mass) with increasing AGN luminosity. We compare to a sample of X-ray selected AGN and find that the two populations have consistent mean SFRs when matched in AGN luminosity and redshift. On the basis of the available virial BH masses, and the evolving BH mass to stellar mass relationship, we find that the mean SFRs of our QSO sample are consistent with those of main sequence star-forming galaxies. Similarly the radio-luminous QSOs have mean SFRs that are consistent with both the overall QSO sample and with star-forming galaxies on the main sequence. In conclusion, on average QSOs reside on the main sequence of star-forming galaxies, and the observed positive trend between the mean SFRs and AGN luminosity can be attributed to BH mass and redshift dependencies.
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| 8. |
- Swinbank, A. M., et al.
(författare)
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An ALMA survey of sub-millimetre Galaxies in the Extended Chandra Deep Field South: the far-infrared properties of SMGs
- 2014
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Ingår i: Monthly Notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 438:2, s. 1267-1287
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Tidskriftsartikel (refereegranskat)abstract
- We exploit Atacama Large Millimeter Array (ALMA) 870 mu m observations of sub-millimetre sources in the Extended Chandra Deep Field South to investigate the far-infrared properties of high-redshift sub-millimetre galaxies (SMGs). Using the precisely located 870 mu m ALMA positions of 99 SMGs, together with 24 mu m and radio imaging, we deblend the Herschel/SPIRE imaging to extract their far-infrared fluxes and colours. The median redshifts for ALMA LESS (ALESS) SMGs which are detected in at least two SPIRE bands increases with wavelength of the peak in their spectral energy distributions (SEDs), with z = 2.3 +/- 0.2, 2.5 +/- 0.3 and 3.5 +/- 0.5 for the 250, 350 and 500 mu m peakers, respectively. 34 ALESS SMGs do not have a >3 sigma counterpart at 250, 350 or 500 mu m. These galaxies have a median photometric redshift derived from the rest-frame UV-mid-infrared SEDs of z = 3.3 +/- 0.5, which is higher than the full ALESS SMG sample; z = 2.5 +/- 0.2. We estimate the far-infrared luminosities and characteristic dust temperature of each SMG, deriving L-IR = (3.0 +/- 0.3) x 10(12) L-circle dot (SFR = 300 +/- 30 M-circle dot yr(-1)) and T-d = 32 +/- 1 K. The characteristic dust temperature of these high-redshift SMGs is Delta T-d = 3-5K lower than comparably luminous galaxies at z = 0, reflecting the more extended star formation in these systems. We show that the contribution of S-870 mu m >= 1 mJy SMGs to the cosmic star formation budget is 20 per cent of the total over the redshift range z similar to 1-4. Adopting an appropriate gas-to-dust ratio, we estimate a typical molecular mass of the ALESS SMGs of M-H2 = (4.2 +/- 0.4) x 10(10) M-circle dot. Finally, we show that SMGs with S-870 mu m > 1 mJy (L-IR greater than or similar to 10(12) L-circle dot) contain similar to 10 per cent of the z similar to 2 volume-averaged H-2 mass density.
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| 9. |
- Wardlow, J. L., et al.
(författare)
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The LABOCA survey of the Extended Chandra Deep Field-South: a photometric redshift survey of submillimetre galaxies
- 2011
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Ingår i: Monthly Notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 415:2, s. 1479-1508
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Tidskriftsartikel (refereegranskat)abstract
- We derive photometric redshifts from 17-band optical to mid-infrared photometry of 78 robust radio, 24-mu m and Spitzer IRAC counterparts to 72 of the 126 submillimetre galaxies (SMGs) selected at 870 mu m by LABOCA observations in the Extended Chandra Deep Field-South (ECDF-S). We test the photometric redshifts of the SMGs against the extensive archival spectroscopy in the ECDF-S. The median photometric redshift of identified SMGs is z = 2.2 +/- 0.1, the standard deviation is sigma(z) = 0.9 and we identify 11 (similar to 15 per cent) high-redshift (z >= 3) SMGs. A statistical analysis of sources in the error circles of unidentified SMGs identifies a population of possible counterparts with a redshift distribution peaking at z = 2.5 +/- 0.2, which likely comprises similar to 60 per cent of the unidentified SMGs. This confirms that the bulk of the undetected SMGs are coeval with those detected in the radio/mid-infrared. We conclude that at most similar to 15 per cent of all the SMGs are below the flux limits of our IRAC observations and thus may lie at z greater than or similar to 3 and hence at most similar to 30 per cent of all SMGs have z greater than or similar to 3. We estimate that the full S(870 mu m) > 4mJy SMG population has a median redshift of 2.5 +/- 0.5. In contrast to previous suggestions, we find no significant correlation between submillimetre flux and redshift. The median stellar mass of the SMGs derived from spectral energy distribution fitting is (9.1 +/- 0.5) x 10(10)M(circle dot) although we caution that the uncertainty in the star formation histories results in a factor of similar to 5 uncertainty in these stellarmasses. Using a single temperature modified blackbody fit with beta = 1.5, the median characteristic dust temperature of SMGs is 37.4 +/- 1.4K. The infrared luminosity function shows that SMGs at z = 2-3 typically have higher far-infrared luminosities and luminosity density than those at z = 1-2. This is mirrored in the evolution of the star formation rate density (SFRD) for SMGs which peaks at z similar to 2. The maximum contribution of bright SMGs to the global SFRD (similar to 5 per cent for SMGs with S(870 mu m) greater than or similar to 4mJy or similar to 50 per cent extrapolated to SMGs with S(870 mu m) > 1mJy) also occurs at z similar to 2.
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