574 research outputs found

    On the evolution of clustering of 24um-selected galaxies

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    This paper investigates the clustering properties of a complete sample of 1041 24um-selected sources brighter than F[24um]=400 uJy in the overlapping region between the SWIRE and UKIDSS UDS surveys. We have concentrated on the two (photometric) interval ranges z=[0.6-1.2] (low-z sample) and z>1.6 (high-z sample) as it is in these regions were we expect the mid-IR population to be dominated by intense dust-enshrouded activity such as star formation and black hole accretion. Investigations of the angular correlation function produce a correlation length are r0~15.9 Mpc for the high-z sample and r0~8.5 Mpc for the low-z one. Comparisons with physical models reveal that the high-z sources are exclusively associated with very massive (M>~10^{13} M_sun)haloes, comparable to those which locally host groups-to-clusters of galaxies, and are very common within such (rare) structures. Conversely, lower-z galaxies are found to reside in smaller halos (M_min~10^{12} M_sun) and to be very rare in such systems. While recent studies have determined a strong evolution of the 24um luminosity function between z~2 and z~0, they cannot provide information on the physical nature of such an evolution. Our clustering results instead indicate that this is due to the presence of different populations of objects inhabiting different structures, as active systems at z<~1.5 are found to be exclusively associated with low-mass galaxies, while very massive sources appear to have concluded their active phase before this epoch. Finally, we note that the small-scale clustering data seem to require steep profiles for the distribution of galaxies within their halos. This is suggestive of close encounters and/or mergers which could strongly favour both AGN and star-formation activity.Comment: 13 pages, 8 figures, to appear in MNRA

    Evolution of cosmic star formation in the SCUBA-2 Cosmology Legacy Survey

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    We present a new exploration of the cosmic star formation history and dust obscuration in massive galaxies at redshifts 0.5 1010M⊙ galaxies at 0.5 10. One third of this is accounted for by 450-μm-detected sources, while one-fifth is attributed to UV-luminous sources (brighter than L∗UV), although even these are largely obscured. By extrapolating our results to include all stellar masses, we estimate a total SFRD that is in good agreement with previous results from IR and UV data at z ≲ 3, and from UV-only data at z ∼ 5. The cosmic star formation history undergoes a transition at z ∼ 3–4, as predominantly unobscured growth in the early Universe is overtaken by obscured star formation, driven by the build-up of the most massive galaxies during the peak of cosmic assembly

    The stellar mass function of the most massive galaxies at 3<=z<5 in the UKIDSS Ultra Deep Survey

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    We have analysed a sample of 1292 4.5 micron-selected galaxies at z>=3, over 0.6 square degrees of the UKIRT Infrared Deep Survey (UKIDSS) Ultra Deep Survey (UDS). Using photometry from the U band through 4.5 microns, we have obtained photometric redshifts and derived stellar masses for our sources. Only two of our galaxies potentially lie at z>5. We have studied the galaxy stellar mass function at 3<=z<5, based on the 1213 galaxies in our catalogue with [4.5]<= 24.0. We find that: i) the number density of M > 10^11 Msun galaxies increased by a factor > 10 between z=5 and 3, indicating that the assembly rate of these galaxies proceeded > 20 times faster at these redshifts than at 0<z<2; ii) the Schechter function slope alpha is significantly steeper than that displayed by the local stellar mass function, which is both a consequence of the steeper faint end and the absence of a pure exponential decline at the high-mass end; iii) the evolution of the comoving stellar mass density from z=0 to 5 can be modelled as log10 (rho_M) =-(0.05 +/- 0.09) z^2 - (0.22 -/+ 0.32) z + 8.69. At 3 10^11 Msun galaxies would be missed by optical surveys with R<27 or z<26. Thus, our study demonstrates the importance of deep mid-IR surveys over large areas to perform a complete census of massive galaxies at high z and trace the early stages of massive galaxy assembly.Comment: 16 pages, 15 figures, 2 tables. Accepted for publication in MNRA

    An ALMA Survey of the SCUBA-2 Cosmology Legacy Survey UKIDSS/UDS Field: Number Counts of Submillimeter Galaxies

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    We report the first results of AS2UDS, an 870 μm continuum survey with the Atacama Large Millimeter/Submillimeter Array (ALMA) of a total area of ~50 arcmin2 comprising a complete sample of 716 submillimeter sources drawn from the SCUBA-2 Cosmology Legacy Survey (S2CLS) map of the UKIDSS/UDS field. The S2CLS parent sample covers a 0.96 degree2 field at σ 850 = 0.90 ± 0.05 mJy beam−1. Our deep, high-resolution ALMA observations with σ 870 ~ 0.25 mJy and a 0farcs15–0farcs30 FWHM synthesized beam, provide precise locations for 695 submillimeter galaxies (SMGs) responsible for the submillimeter emission corresponding to 606 sources in the low-resolution, single-dish map. We measure the number counts of SMGs brighter than S 870 ≥ 4 mJy, free from the effects of blending and show that the normalization of the counts falls by 28% ± 2% in comparison with the SCUBA-2 published counts, but that the shape remains unchanged. We determine that 4414+16{44}_{-14}^{+16}% of the brighter single-dish sources with S 850 ≥ 9 mJy consist of a blend of two or more ALMA-detectable SMGs brighter than S 870 ~ 1 mJy (corresponding to a galaxy with a total-infrared luminosity of L IR gsim 1012 L ⊙), in comparison with 28% ± 2% for the single-dish sources at S 850 ≥ 5 mJy. Using the 46 single-dish submillimeter sources that contain two or more ALMA-detected SMGs with photometric redshifts, we show that there is a significant statistical excess of pairs of SMGs with similar redshifts (<1% probability of occurring by chance), suggesting that at least 30% of these blends arise from physically associated pairs of SMGs

    Multiwavelength characterization of faint ultra steep spectrum radio sources: a search for high-redshift radio galaxies

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    Context. Ultra steep spectrum (USS) radio sources are one of the efficient tracers of powerful high-z radio galaxies (HzRGs). In contrast to searches for powerful HzRGs from radio surveys of moderate depths, fainter USS samples derived from deeper radio surveys can be useful in finding HzRGs at even higher redshifts and in unveiling a population of obscured weaker radio-loud AGN at moderate redshifts. Aims. Using our 325 MHz GMRT observations (5σ ∼ 800 μJy) and 1.4 GHz VLA observations (5σ ∼ 80−100 μJy) available in two subfields (VLA-VIMOS VLT Deep Survey (VLA-VVDS) and Subaru X-ray Deep Field (SXDF)) of the XMM-LSS field, we derive a large sample of 160 faint USS radio sources and characterize their nature. Methods. The optical and IR counterparts of our USS sample sources are searched using existing deep surveys, at respective wavelengths. We attempt to unveil the nature of our faint USS sources using diagnostic techniques based on mid-IR colors, flux ratios of radio to mid-IR, and radio luminosities. Results. Redshift estimates are available for 86/116 (∼74%) USS sources in the VLA-VVDS field and for 39/44 (∼87%) USS sources in the SXDF fields with median values (zmedian) ∼1.18 and ∼1.57, respectively, which are higher than estimates for non-USS radio sources (zmedian non−USS ∼ 0.99 and ∼0.96), in the two subfields. The MIR color–color diagnostic and radio luminosities are consistent with most of our USS sample sources at higher redshifts (z > 0.5) being AGN. The flux ratio of radio to mid-IR (S 1.4 GHz/S 3.6 μm) versus redshift diagnostic plot suggests that more than half of our USS sample sources distributed over z ∼ 0.5 to 3.8 are likely to be hosted in obscured environments. A significant fraction (∼26% in the VLA-VVDS and ∼13% in the SXDF) of our USS sources without redshift estimates mostly remain unidentified in the existing optical, IR surveys, and exhibit high radio to mid-IR flux ratio limits similar to HzRGs, and so, can be considered as potential HzRG candidates. Conclusions. Our study shows that the criterion of ultra steep spectral index remains a reasonably efficient method to select high-z sources even at sub-mJy flux densities. In addition to powerful HzRG candidates, our faint USS sample also contains populations of weaker radio-loud AGNs potentially hosted in obscured environments

    The SCUBA-2 Cosmology Legacy Survey: ALMA resolves the bright-end of the submillimeter number counts

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    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 = 8.7 ± 0.4 mJy). We detect 52 sub-millimeter galaxies (SMGs) at >4σ significance in our 30 ALMA maps. In 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 1012 . The brightest SMG contributes on average of the single-dish flux density, and in the ALMA maps containing ≥2 SMGs the secondary SMG contributes 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 or a star formation rate (SFR) of ~103 . For the typical sizes of these SMGs, which are resolved in our ALMA data with = 1.2 ± 0.1 kpc, this yields a limiting SFR density of ~100 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

    Focused Analysis of Exome Sequencing Data for Rare Germline Mutations in Familial and Sporadic Lung Cancer

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    AbstractIntroductionThe association between smoking-induced chronic obstructive pulmonary disease (COPD) and lung cancer (LC) is well documented. Recent genome-wide association studies (GWAS) have identified 28 susceptibility loci for LC, 10 for COPD, 32 for smoking behavior, and 63 for pulmonary function, totaling 107 nonoverlapping loci. Given that common variants have been found to be associated with LC in genome-wide association studies, exome sequencing of these high-priority regions has great potential to identify novel rare causal variants.MethodsTo search for disease-causing rare germline mutations, we used a variation of the extreme phenotype approach to select 48 patients with sporadic LC who reported histories of heavy smoking—37 of whom also exhibited carefully documented severe COPD (in whom smoking is considered the overwhelming determinant)—and 54 unique familial LC cases from families with at least three first-degree relatives with LC (who are likely enriched for genomic effects).ResultsBy focusing on exome profiles of the 107 target loci, we identified two key rare mutations. A heterozygous p.Arg696Cys variant in the coiled-coil domain containing 147 (CCDC147) gene at 10q25.1 was identified in one sporadic and two familial cases. The minor allele frequency (MAF) of this variant in the 1000 Genomes database is 0.0026. The p.Val26Met variant in the dopamine β-hydroxylase (DBH) gene at 9q34.2 was identified in two sporadic cases; the minor allele frequency of this mutation is 0.0034 according to the 1000 Genomes database. We also observed three suggestive rare mutations on 15q25.1: iron-responsive element binding protein neuronal 2 (IREB2); cholinergic receptor, nicotinic, alpha 5 (neuronal) (CHRNA5); and cholinergic receptor, nicotinic, beta 4 (CHRNB4).ConclusionsOur results demonstrated highly disruptive risk-conferring CCDC147 and DBH mutations

    The SCUBA-2 Cosmology Legacy Survey : The EGS deep field I - Deep number counts and the redshift distribution of the recovered Cosmic Infrared Background at 450 and 850 um

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    This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society. ©: 2016 The Author (s). Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.We present deep observations at 450 um and 850 um 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 σ450=1.2\sigma_{450}=1.2 mJy/beam and σ850=0.2\sigma_{850}=0.2 mJy/beam. We detect 57 sources at 450 um and 90 at 850 um with S/N > 3.5 over ~70 sq. arcmin. From these detections we derive the number counts at flux densities S450>4.0S_{450}>4.0 mJy and S850>0.9S_{850}>0.9 mJy, 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 um-selected galaxies through a stacking technique, which add a total of 0.26±0.030.26\pm0.03 and 0.07±0.010.07\pm0.01 MJy/sr, at 450 um and 850 um, respectively. These surface brightnesses correspond to 60±2060\pm20 and 50±2050\pm20 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 um-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 z1z\sim1 for 450 um and at z2z\sim2 for 850um, consistent with previous observations and theoretical models.Peer reviewedFinal Published versio

    A Physical Model for z~2 Dust Obscured Galaxies

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    We present a physical model for the origin of z~2 Dust-Obscured Galaxies (DOGs), a class of high-redshift ULIRGs selected at 24 micron which are particularly optically faint (24/R>1000). By combining N-body/SPH simulations of high redshift galaxy evolution with 3D polychromatic dust radiative transfer models, we find that luminous DOGs (with F24 > 0.3 mJy at z~2 are well-modeled as extreme gas-rich mergers in massive (~5x10^12-10^13 Msun) halos, with elevated star formation rates (~500-1000 Msun/yr) and/or significant AGN growth (Mdot > 0.5 Msun/yr), whereas less luminous DOGs are more diverse in nature. At final coalescence, merger-driven DOGs transition from being starburst dominated to AGN dominated, evolving from a "bump" to a power-law shaped mid-IR (IRAC) spectral energy distribution (SED). After the DOG phase, the galaxy settles back to exhibiting a "bump" SED with bluer colors and lower star formation rates. While canonically power-law galaxies are associated with being AGN-dominated, we find that the power-law mid-IR SED can owe both to direct AGN contribution, as well as to a heavily dust obscured stellar bump at times that the galaxy is starburst dominated. Thus power-law galaxies can be either starburst or AGN dominated. Less luminous DOGs can be well-represented either by mergers, or by massive ($M_{\rm baryon} ~5x10^11 Msun) secularly evolving gas-rich disc galaxies (with SFR > 50 Msun/yr). By utilising similar models as those employed in the SMG formation study of Narayanan et al. (2010), we investigate the connection between DOGs and SMGs. We find that the most heavily star-forming merger driven DOGs can be selected as Submillimetre Galaxies (SMGs), while both merger-driven and secularly evolving DOGs typically satisfy the BzK selection criteria.Comment: Accepted by MNRAS; major changes include better description of dependency on ISM specification and updated models allowing dust to evolve with metallicity