Browsing by Author "Cooray, A."

Now showing 1 - 15 of 15
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    A massive, distant proto-cluster at z = 2.47 caught in a phase of rapid formation?
    (2015) Casey, C. M.; Treister, Ezequiel; Cooray, A.; Capak, P.; Fu, H.; Kovac, K.; Lilly, S.; Sanders, David B.; Scoville, Nick Z.
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    CONSTRAINING THE Lyα ESCAPE FRACTION WITH FAR- INFRARED OBSERVATIONS OF Lyα EMITTERS
    (2014) Wardlow, Julie L.; Malhotra, S.; Zheng, Z.; Finkelstein, S.; Bock, J.; Bridge, C.; Calanog, J.; Ciardullo, R.; Conley, A.; Cooray, A.; Farrah, D.; Gawiser, E.; Gronwall, C.; Heinis, S.; Ibar, E.; Ivison, R. J.; Marsden, G.; Oliver, S. J.; Rhoads, J.; Riechers, D.; Schulz, B.; Smith, A. J.; Viero, M.; Wang, L.; Zemcov, M.
    We study the far-infrared properties of 498 Ly alpha emitters (LAEs) at z = 2.8, 3.1, and 4.5 in the Extended Chandra Deep Field-South, using 250, 350, and 500 mu m data from the Herschel Multi-tiered Extragalactic Survey and 870 mu m data from the LABOCA ECDFS Submillimeter Survey. None of the 126, 280, or 92 LAEs at z = 2.8, 3.1, and 4.5, respectively, are individually detected in the far-infrared data. We use stacking to probe the average emission to deeper flux limits, reaching 1 sigma depths of similar to 0.1 to 0.4 mJy. The LAEs are also undetected at >= 3 sigma in the stacks, although a 2.5 sigma signal is observed at 870 mu m for the z = 2.8 sources. We consider a wide range of far-infrared spectral energy distributions (SEDs), including an M82 and an Sd galaxy template, to determine upper limits on the far-infrared luminosities and far-infrared-derived star formation rates of the LAEs. These star formation rates are then combined with those inferred from the Ly alpha and UV emission to determine lower limits on the LAEs' Lya escape fraction (f(esc)(Ly alpha)). For the Sd SED template, the inferred LAEs fesc(Ly alpha) are greater than or similar to 30% (1 sigma) at z = 2.8, 3.1, and 4.5, which are all significantly higher than the global fesc(Ly alpha) at these redshifts. Thus, if the LAEs fesc(Ly alpha) follows the global evolution, then they have warmer far-infrared SEDs than the Sd galaxy template. The average and M82 SEDs produce lower limits on the LAE fesc(Ly alpha) of similar to 10%-20% (1 sigma), all of which are slightly higher than the global evolution of fesc(Ly alpha), but consistent with it at the 2 sigma-3 sigma level.
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    Environment of the submillimeter-bright massive starburst HFLS3 at z similar to 6.34
    (2015) Laporte, Nicolás; Perez, I.; Calanog, J.; Cooray, A.; Wardlow, J.; Bock, J.; Bridge, C.; Burgarella, D.; Bussmann, R.; Cabrera, Alejandro Leopoldo; Casey, C.; Clements, D.; Conley, A.; Dannerbauer, H.; Farrah, D.; Fu, H.
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    GRAVITATIONAL LENS MODELS BASED ON SUBMILLIMETER ARRAY IMAGING OF HERSCHEL-SELECTED STRONGLY LENSED SUB-MILLIMETER GALAXIES AT z > 1.5
    (2013) Bussmann, R. S.; Perez-Fournon, I.; Amber, S.; Calanog, J.; Gurwell, M. A.; Dannerbauer, H.; De Bernardis, F.; Fu, Hai; Harris, A. I.; Krips, M.; Lapi, A.; Maiolino, R.; Omont, A.; Riechers, D.; Wardlow, J.; Baker, A. J.; Birkinshaw, M.; Bock, J.; Bourne, N.; Clements, D. L.; Cooray, A.; De Zotti, G.; Dunne, L.; Dye, S.; Eales, S.; Farrah, D.; Gavazzi, R.; Nuevo, J. Gonzalez; Hopwood, R.; Ibar, E.; Ivison, R. J.; Laporte, N.; Maddox, S.; Martinez-Navajas, P.; Michalowski, M.; Negrello, M.; Oliver, S. J.; Roseboom, I. G.; Scott, Douglas; Serjeant, S.; Smith, A. J.; Smith, Matthew; Streblyanska, A.; Valiante, E.; van der Werf, P.; Verma, A.; Vieira, J. D.; Wang, L.; Wilner, D.
    Strong gravitational lenses are now being routinely discovered in wide-field surveys at (sub-)millimeter wavelengths. We present Submillimeter Array (SMA) high-spatial resolution imaging and Gemini-South and Multiple Mirror Telescope optical spectroscopy of strong lens candidates discovered in the two widest extragalactic surveys conducted by the Herschel Space Observatory: the Herschel-Astrophysical Terahertz Large Area Survey (H-ATLAS) and the Herschel Multi-tiered Extragalactic Survey (HerMES). From a sample of 30 Herschel sources with S-500 > 100 mJy, 21 are strongly lensed (i.e., multiply imaged), 4 are moderately lensed (i.e., singly imaged), and the remainder require additional data to determine their lensing status. We apply a visibility-plane lens modeling technique to the SMA data to recover information about the masses of the lenses as well as the intrinsic (i.e., unlensed) sizes (r(half)) and far-infrared luminosities (L-FIR) of the lensed submillimeter galaxies (SMGs). The sample of lenses comprises primarily isolated massive galaxies, but includes some groups and clusters as well. Several of the lenses are located at z(lens) > 0.7, a redshift regime that is inaccessible to lens searches based on Sloan Digital Sky Survey spectroscopy. The lensed SMGs are amplified by factors that are significantly below statistical model predictions given the 500 mu m flux densities of our sample. We speculate that this may reflect a deficiency in our understanding of the intrinsic sizes and luminosities of the brightest SMGs. The lensed SMGs span nearly one decade in L-FIR (median L-FIR = 7.9 x 10(12) L-circle dot) and two decades in FIR luminosity surface density (median Sigma(FIR) = 6.0 x 10(11) L-circle dot kpc(-2)). The strong lenses in this sample and others identified via (sub-) mm surveys will provide a wealth of information regarding the astrophysics of galaxy formation and evolution over a wide range in redshift.
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    H2O emission in high-z ultra-luminous infrared galaxies
    (2013) Omont, A.; Yang, C.; Cox, P.; Neri, R.; Beelen, A.; Bussmann, R. S.; Gavazzi, R.; van der Werf, P.; Riechers, D.; Downes, D.; Krips, M.; Dye, S.; Ivison, R.; Vieira, J. D.; Weiss, A.; Aguirre, J. E.; Baes, M.; Baker, A. J.; Bertoldi, F.; Cooray, A.; Dannerbauer, H.; De Zotti, G.; Eales, S. A.; Fu, H.; Gao, Y.; Guelin, M.; Harris, A. I.; Jarvis, M.; Lehnert, M.; Leeuw, L.; Lupu, R.; Menten, K.; Michalowski, M. J.; Negrello, M.; Serjeant, S.; Temi, P.; Auld, R.; Dariush, A.; Dunne, L.; Fritz, J.; Hopwood, R.; Hoyos, C.; Ibar, E.; Maddox, S.; Smith, M. W. L.; Valiante, E.; Bock, J.; Bradford, C. M.; Glenn, J.; Scott, K. S.
    Using the IRAM Plateau de Bure interferometer (PdBI), we report the detection of water vapor in six new lensed ultra-luminous starburst galaxies at high redshift, discovered in the Herschel Astrophysical Terahertz Large Area Survey (H-ATLAS). The sources are detected either in the 2(02)-1(11) or 2(11)-2(02) H2O emission lines with integrated line fluxes ranging from 1.8 to 14 Jy km s(-1). The corresponding apparent luminosities are mu L-H2O similar to 3-12 x 10(8) L-circle dot, where mu is the lensing magnification factor (3 < mu < 12). These results confirm that H2O lines are among the strongest molecular lines in high-z ultra-luminous starburst galaxies, with intensities almost comparable to those of the high-J CO lines, and similar profiles and line widths (similar to 200-900 km s(-1)). With the current sensitivity of the PdBI, the water lines can therefore easily be detected in high-z lensed galaxies (with F(500 mu m) > 100 mJy) discovered in the Herschel surveys. Correcting the luminosities for amplification, using existing lensing models, L-H2O is found to have a strong dependence on the infrared luminosity, varying as similar to L-IR(1.2). This relation, which needs to be confirmed with better statistics, may indicate a role of radiative (infrared) excitation of the H2O lines, and implies that high-z galaxies with L-IR greater than or similar to 10(13) L-circle dot tend to be very strong emitters in water vapor, that have no equivalent in the local universe.
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    HerMES: CANDIDATE HIGH-REDSHIFT GALAXIES DISCOVERED WITH HERSCHEL/SPIRE
    (2014) Dowell, C. Darren; Conley, A.; Glenn, J.; Arumugam, V.; Asboth, V.; Aussel, H.; Bertoldi, F.; Bethermin, M.; Bock, J.; Boselli, A.; Bridge, C.; Buat, V.; Burgarella, D.; Cabrera-Lavers, A.; Casey, C. M.; Chapman, S. C.; Clements, D. L.; Conversi, L.; Cooray, A.; Dannerbauer, H.; De Bernardis, F.; Ellsworth-Bowers, T. P.; Farrah, D.; Franceschini, A.; Griffin, M.; Gurwell, M. A.; Halpern, M.; Hatziminaoglou, E.; Heinis, S.; Ibar, E.; Ivison, R. J.; Laporte, N.; Marchetti, L.; Martinez-Navajas, P.; Marsden, G.; Morrison, G. E.; Nguyen, H. T.; O'Halloran, B.; Oliver, S. J.; Omont, A.; Page, M. J.; Papageorgiou, A.; Pearson, C. P.; Petitpas, G.; Perez-Fournon, I.; Pohlen, M.; Riechers, D.; Rigopoulou, D.; Roseboom, I. G.; Rowan-Robinson, M.; Sayers, J.; Schulz, B.; Scott, Douglas; Seymour, N.; Shupe, D. L.; Smith, A. J.; Streblyanska, A.; Symeonidis, M.; Vaccari, M.; Valtchanov, I.; Vieira, J. D.; Viero, M.; Wang, L.; Wardlow, J.; Xu, C. K.; Zemcov, M.
    We present a method for selecting z > 4 dusty, star-forming galaxies (DSFGs) using Herschel/Spectral and Photometric Imaging Receiver 250/350/500 mu m flux densities to search for red sources. We apply this method to 21 deg(2) of data from the HerMES survey to produce a catalog of 38 high-z candidates. Follow-up of the first five of these sources confirms that this method is efficient at selecting high-z DSFGs, with 4/5 at z = 4.3-6.3 (and the remaining source at z = 3.4), and that they are some of the most luminous dusty sources known. Comparison with previous DSFG samples, mostly selected at longer wavelengths (e. g., 850 mu m) and in single-band surveys, shows that our method is much more efficient at selecting high-z DSFGs, in the sense that a much larger fraction are at z > 3. Correcting for the selection completeness and purity, we find that the number of bright (S-500 (mu m) >= 30 mJy), red Herschel sources is 3.3 +/- 0.8 deg(-2). This is much higher than the number predicted by current models, suggesting that the DSFG population extends to higher redshifts than previously believed. If the shape of the luminosity function for high-z DSFGs is similar to that at z similar to 2, rest-frame UV based studies may be missing a significant component of the star formation density at z = 4-6, even after correction for extinction.
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    HerMES: COSMIC INFRARED BACKGROUND ANISOTROPIES AND THE CLUSTERING OF DUSTY STAR-FORMING GALAXIES
    (2013) Viero, M. P.; Wang, L.; Zemcov, M.; Addison, G.; Amblard, A.; Arumugam, V.; Aussel, H.; Bethermin, M.; Bock, J.; Boselli, A.; Buat, V.; Burgarella, D.; Casey, C. M.; Clements, D. L.; Conley, A.; Conversi, L.; Cooray, A.; De Zotti, G.; Dowell, C. D.; Farrah, D.; Franceschini, A.; Glenn, J.; Griffin, M.; Hatziminaoglou, E.; Heinis, S.; Ibar, E.; Ivison, R. J.; Lagache, G.; Levenson, L.; Marchetti, L.; Marsden, G.; Nguyen, H. T.; O'Halloran, B.; Oliver, S. J.; Omont, A.; Page, M. J.; Papageorgiou, A.; Pearson, C. P.; Perez-Fournon, I.; Pohlen, M.; Rigopoulou, D.; Roseboom, I. G.; Rowan-Robinson, M.; Schulz, B.; Scott, D.; Seymour, N.; Shupe, D. L.; Smith, A. J.; Symeonidis, M.; Vaccari, M.; Valtchanov, I.; Vieira, J. D.; Wardlow, J.; Xu, C. K.
    We present measurements of the auto-and cross-frequency power spectra of the cosmic infrared background (CIB) at 250, 350, and 500 mu m (1200, 860, and 600 GHz) from observations totaling similar to 70 deg(2) made with the SPIRE instrument aboard the Herschel Space Observatory. We measure a fractional anisotropy delta I/I = 14% +/- 4%, detecting signatures arising from the clustering of dusty star-forming galaxies in both the linear (2-halo) and nonlinear (1-halo) regimes; and that the transition from the 2- to 1-halo terms, below which power originates predominantly from multiple galaxies within dark matter halos, occurs at k(theta) similar to 0.10-0.12 arcmin(-1) (l similar to 2160-2380), from 250 to 500 mu m. New to this paper is clear evidence of a dependence of the Poisson and 1-halo power on the flux-cut level of masked sources-suggesting that some fraction of the more luminous sources occupy more massive halos as satellites, or are possibly close pairs. We measure the cross-correlation power spectra between bands, finding that bands which are farthest apart are the least correlated, as well as hints of a reduction in the correlation between bands when resolved sources are more aggressively masked. In the second part of the paper, we attempt to interpret the measurements in the framework of the halo model. With the aim of fitting simultaneously with one model the power spectra, number counts, and absolute CIB level in all bands, we find that this is achievable by invoking a luminosity-mass relationship, such that the luminosity-to-mass ratio peaks at a particular halo mass scale and declines toward lower and higher mass halos. Our best-fit model finds that the halo mass which is most efficient at hosting star formation in the redshift range of peak star-forming activity, z similar to 1-3, is log( M-peak/M-circle dot) similar to 12.1 +/- 0.5, and that the minimum halo mass to host infrared galaxies is log(Mmin/M-circle dot) similar to 10.1 +/- 0.6.
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    HerMES: THE CONTRIBUTION TO THE COSMIC INFRARED BACKGROUND FROM GALAXIES SELECTED BY MASS AND REDSHIFT
    (2013) Viero, M. P.; Moncelsi, L.; Quadri, R. F.; Arumugam, V.; Assef, R. J.; Bethermin, M.; Bock, J.; Bridge, C.; Casey, C. M.; Conley, A.; Cooray, A.; Farrah, D.; Glenn, J.; Heinis, S.; Ibar, E.; Ikarashi, S.; Ivison, R. J.; Kohno, K.; Marsden, G.; Oliver, S. J.; Roseboom, I. G.; Schulz, B.; Scott, D.; Serra, P.; Vaccari, M.; Vieira, J. D.; Wang, L.; Wardlow, J.; Wilson, G. W.; Yun, M. S.; Zemcov, M.
    We quantify the fraction of the cosmic infrared background (CIB) that originates from galaxies identified in the UV/optical/near-infrared by stacking 81,250 (similar to 35.7 arcmin(-2)) K-selected sources (K-AB < 24.0) split according to their rest-frame U-V versus V-J colors into 72,216 star-forming and 9034 quiescent galaxies, on maps from Spitzer/MIPS (24 mu m), Herschel/PACS (100, 160 mu m), Herschel/SPIRE (250, 350, 500 mu m), and AzTEC (1100 mu m). The fraction of the CIB resolved by our catalog is (69% +/- 15%) at 24 mu m, (78% +/- 17%) at 70 mu m, (58% +/- 13%) at 100 mu m, (78% +/- 18%) at 160 mu m, (80% +/- 17%) at 250 mu m, (69% +/- 14%) at 350 mu m, (65% +/- 12%) at 500 mu m, and (45% +/- 8%) at 1100 mu m. Of that total, about 95% originates from star-forming galaxies, while the remaining 5% is from apparently quiescent galaxies. The CIB at lambda less than or similar to 200 mu m appears to be sourced predominantly from galaxies at z less than or similar to 1, while at. greater than or similar to 200 mu m the bulk originates from 1 less than or similar to z less than or similar to 2. Galaxies with stellar masses log(M/M-circle dot) = 9.5-11 are responsible for the majority of the CIB, with those in the log(M/M-circle dot) = 9.5-10 bin contributing mostly at lambda < 250 mu m, and those in the log(M/M circle dot) = 10-11 bin dominating at lambda > 350 mu m. The contribution from galaxies in the log(M/M-circle dot) = 9.0-9.5 (lowest) and log(M/M-circle dot) = 11.0-12.0 (highest) stellar-mass bins contribute the least-both of order 5%-although the highest stellar-mass bin is a significant contributor to the luminosity density at z greater than or similar to 2. The luminosities of the galaxies responsible for the CIB shifts from combinations of "normal" and luminous infrared galaxies (LIRGs) at lambda less than or similar to 160 mu m, to LIRGs at 160 less than or similar to lambda less than or similar to 500 mu m, to finally LIRGs and ultra-luminous infrared galaxies at lambda greater than or similar to 500 mu m. Stacking analyses were performed using SIMSTACK, a novel algorithm designed to account for possible biases in the stacked flux density due to clustering. It is made available to the public at www.astro.caltech.edu/similar to viero/viero_homepage/toolbox.html.
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    Herschel-ATLAS/GAMA: What determines the far-infrared properties of radio galaxies?
    (2013) Virdee, J. S.; Hardcastle, M. J.; Rawlings, S.; Rigopoulou, D.; Mauch, T.; Jarvis, M. J.; Verma, A.; Smith, D. J. B.; Heywood, I.; White, S. V.; Baes, M.; Cooray, A.; de Zotti, G.; Eales, S.; Michalowski, M. J.; Bourne, N.; Dariush, A.; Dunne, L.; Hopwood, R.; Ibar, E.; Maddox, S.; Smith, M. W. L.; Valiante, E.
    We perform a stacking analysis of Herschel Astrophysical Terahertz Large Area Survey (H-ATLAS) data in order to obtain isothermal dust temperatures and rest-frame luminosities at 250 mu m (L-250), for a well-defined sample of 1599 radio sources over the H-ATLAS Phase 1/Galaxy and Mass Assembly (GAMA) area. The radio sample is generated using a combination of NRAO VLA Sky Survey data and K-band United Kingdom Infrared Telescope Deep Sky Survey-Large Area Survey data, over the redshift range 0.01 < z < 0.8. The far-infrared (FIR) properties of the sample are investigated as a function of 1.4-GHz luminosity, redshift, projected radio-source size and radio spectral index. In order to search for stellar-mass-dependent relations, we split the parent sample into those sources which are below and above 1.5 L-K*.
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    HERSCHEL-ATLAS: A BINARY HyLIRG PINPOINTING A CLUSTER OF STARBURSTING PROTOELLIPTICALS
    (2013) Ivison, R. J.; Swinbank, A. M.; Smail, Ian; Harris, A. I.; Bussmann, R. S.; Cooray, A.; Cox, P.; Fu, H.; Kovacs, A.; Krips, M.; Narayanan, D.; Negrello, M.; Neri, R.; Penarrubia, J.; Richard, J.; Riechers, D. A.; Rowlands, K.; Staguhn, J. G.; Targett, T. A.; Amber, S.; Baker, A. J.; Bourne, N.; Bertoldi, F.; Bremer, M.; Calanog, J. A.; Clements, D. L.; Dannerbauer, H.; Dariush, A.; De Zotti, G.; Dunne, L.; Eales, S. A.; Farrah, D.; Fleuren, S.; Franceschini, A.; Geach, J. E.; George, R. D.; Helly, J. C.; Hopwood, R.; Ibar, E.; Jarvis, M. J.; Kneib, J. -P.; Maddox, S.; Omont, A.; Scott, D.; Serjeant, S.; Smith, M. W. L.; Thompson, M. A.; Valiante, E.; Valtchanov, I.; Vieira, J.; van der Werf, P.
    Panchromatic observations of the best candidate hyperluminous infrared galaxies from the widest Herschel extragalactic imaging survey have led to the discovery of at least four intrinsically luminous z = 2.41 galaxies across an approximate to 100 kpc region-a cluster of starbursting protoellipticals. Via subarcsecond interferometric imaging we have measured accurate gas and star formation surface densities. The two brightest galaxies span similar to 3 kpc FWHM in submillimeter/radio continuum and CO J = 4-3, and double that in CO J = 1-0. The broad CO line is due partly to the multitude of constituent galaxies and partly to large rotational velocities in two counter-rotating gas disks-a scenario predicted to lead to the most intense starbursts, which will therefore come in pairs. The disks have M-dyn of several x 10(11) M-circle dot, and gas fractions of similar to 40%. Velocity dispersions are modest so the disks are unstable, potentially on scales commensurate with their radii: these galaxies are undergoing extreme bursts of star formation, not confined to their nuclei, at close to the Eddington limit. Their specific star formation rates place them greater than or similar to 5x above the main sequence, which supposedly comprises large gas disks like these. Their high star formation efficiencies are difficult to reconcile with a simple volumetric star formation law. N-body and dark matter simulations suggest that this system is the progenitor of a B(inary)-type approximate to 10(14.6)-M-circle dot cluster.
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    Herschel-ATLAS: correlations between dust and gas in local submm-selected galaxies
    (2013) Bourne, N.; Dunne, L.; Bendo, G. J.; Smith, M. W. L.; Clark, C. J. R.; Smith, D. J. B.; Rigby, E. E.; Baes, M.; Leeuw, L. L.; Maddox, S. J.; Thompson, M. A.; Bremer, M. N.; Cooray, A.; Dariush, A.; de Zotti, G.; Dye, S.; Eales, S.; Hopwood, R.; Ibar, E.; Ivison, R. J.; Jarvis, M. J.; Michalowski, M. J.; Rowlands, K.; Valiante, E.
    We present an analysis of CO molecular gas tracers in a sample of 500 mu m-selected Herschel Astrophysical Terahertz Large Area Survey (H-ATLAS) galaxies at z < 0.05 (cz < 14990 km s(-1)). Using 22-500 mu m photometry from Wide-Field Infrared Survey Explorer, Infrared Astronomical Satellite and Herschel, with HI data from the literature, we investigate correlations between warm and cold dust, and tracers of the gas in different phases. The correlation between global CO(3-2) line fluxes and far-infrared (FIR)-submillimetre (submm) fluxes weakens with increasing infrared wavelength (lambda greater than or similar to 60 mu m), as a result of colder dust being less strongly associated with dense gas. Conversely, CO(2-1) and HI line fluxes both appear to be better correlated with longer wavelengths, suggesting that cold dust is more strongly associated with diffuse atomic and molecular gas phases, consistent with it being at least partially heated by radiation from old stellar populations. The increased scatter at long wavelengths implies that submm fluxes are a poorer tracer of star formation rate (SFR). Fluxes at 22 and 60 mu m are also better correlated with diffuse gas tracers than dense CO(3-2), probably due to very small grain emission in the diffuse interstellar medium, which is not correlated with SFR. The FIR/CO luminosity ratio and the dust mass/CO luminosity ratio both decrease with increasing luminosity, as a result of either correlations between mass and metallicity (changing CO/H-2) or between CO luminosity and excitation [changing CO(3-2)/CO(1-0)].
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    Herschel-ATLAS: modelling the first strong gravitational lenses
    (2014) Dye, S.; Negrello, M.; Hopwood, R.; Nightingale, J. W.; Bussmann, R. S.; Amber, S.; Bourne, N.; Cooray, A.; Dariush, A.; Dunne, L.; Eales, S. A.; Gonzalez-Nuevo, J.; Ibar, E.; Ivison, R. J.; Maddox, S.; Valiante, E.; Smith, M.
    We have determined the mass density radial profiles of the first five strong gravitational lens systems discovered by the Herschel Astrophysical Terahertz Large Area Survey. We present an enhancement of the semilinear lens inversion method of Warren & Dye which allows simultaneous reconstruction of several different wavebands and apply this to dual-band imaging of the lenses acquired with the Hubble Space Telescope. The five systems analysed here have lens redshifts which span a range 0.22 <= z <= 0.94. Our findings are consistent with other studies by concluding that: (1) the logarithmic slope of the total mass density profile steepens with decreasing redshift; (2) the slope is positively correlated with the average total projected mass density of the lens contained within half the effective radius and negatively correlated with the effective radius; (3) the fraction of dark matter contained within half the effective radius increases with increasing effective radius and increases with redshift.
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    Isothermal dust models of Herschel-ATLAS☆ galaxies
    (2013) Smith, D. J. B.; Hardcastle, M. J.; Jarvis, M. J.; Maddox, S. J.; Dunne, L.; Bonfield, D. G.; Eales, S.; Serjeant, S.; Thompson, M. A.; Baes, M.; Clements, D. L.; Cooray, A.; De Zotti, G.; Gonzalez-Nuevo, J.; van der Werf, P.; Virdee, J.; Bourne, N.; Dariush, A.; Hopwood, R.; Ibar, E.; Valiante, E.
    We use galaxies from the Herschel-ATLAS (H-ATLAS) survey, and a suite of ancillary simulations based on an isothermal dust model, to study our ability to determine the effective dust temperature, luminosity and emissivity index of 250 mu m selected galaxies in the local Universe (z < 0.5). As well as simple far-infrared spectral energy distribution (SED) fitting of individual galaxies based on chi(2) minimization, we attempt to derive the best global isothermal properties of 13 826 galaxies with reliable optical counterparts and spectroscopic redshifts. Using our simulations, we highlight the fact that applying traditional SED fitting techniques to noisy observational data in the Herschel Space Observatory bands introduces artificial anti-correlation between derived values of dust temperature and emissivity index. This is true even for galaxies with the most robust statistical detections in our sample, making the results of such fitting difficult to interpret. We apply a method to determine the best-fitting global values of isothermal effective temperature and emissivity index for z < 0.5 galaxies in H-ATLAS, deriving T-eff = 22.3 +/- 0.1 K and beta = 1.98 +/- 0.02 (or T-eff = 23.5 +/- 0.1 K and beta = 1.82 +/- 0.02 if we attempt to correct for bias by assuming that T-eff and beta(eff) are independent and normally distributed). We use our technique to test for an evolving emissivity index, finding only weak evidence. The median dust luminosity of our sample is log(10)(L-dust/L-circle dot) = 10.72 +/- 0.05, which (unlike T-eff) shows little dependence on the choice of beta used in our analysis, including whether it is variable or fixed. In addition, we use a further suite of simulations based on a fixed emissivity index isothermal model to emphasize the importance of the H-ATLAS PACS data for deriving dust temperatures at these redshifts, even though they are considerably less sensitive than the SPIRE data. Finally, we show that the majority of galaxies detected by H-ATLAS are normal star-forming galaxies, though with a substantial minority (similar to 31 per cent) falling in the Luminous Infrared Galaxy category.
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    The composite nature of Dust-Obscured Galaxies (DOGs) at z ∼ 2–3 in the COSMOS field – I. A far-infrared view.
    (2015) Riguccini, L; Treister, Ezequiel; Le Floc'h, E.; Mullaney, J.; Menéndez-Delmestre, K.; Aussel, H.; Berta, S.; Calanog, J.; Capak, P.; Cooray, A.; Ilbert, O.
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    The roles of star formation and AGN activity of IRS sources in the HerMES fields
    (2013) Feltre, A.; Hatziminaoglou, E.; Hernan-Caballero, A.; Fritz, J.; Franceschini, A.; Bock, J.; Cooray, A.; Farrah, D.; Solares, E. A. Gonzalez; Ibar, E.; Isaak, K. G.; Lo Faro, B.; Marchetti, L.; Oliver, S. J.; Page, M. J.; Rigopoulou, D.; Roseboom, I. G.; Symeonidis, M.; Vaccari, M.
    In this work, we explore the impact of the presence of an active galactic nucleus (AGN) on the mid- and far-infrared (IR) properties of galaxies as well as the effects of simultaneous AGN and starburst activity in the same galaxies. To do this, we apply a multicomponent, multiband spectral synthesis technique to a sample of 250 mu m selected galaxies of the Herschel Multi-tiered Extragalactic Survey (HerMES), with Infrared Spectrograph (IRS) spectra available for all galaxies. Our results confirm that the inclusion of the IRS spectra plays a crucial role in the spectral analysis of galaxies with an AGN component improving the selection of the best-fitting hot dust (torus) model.