S. Eales

Publications (143)240.8 Total impact

• Article: {\em Herschel}-ATLAS/GAMA: The Environmental Density of Far-Infrared Bright Galaxies at $z \leq 0.5$

  C. S. Burton, Matt J. Jarvis, D. J. B. Smith, D. G. Bonfield, M. J. Hardcastle, J. A. Stevens, N. Bourne, M. Baes, S. Brough, A. Cava, [......], S. Eales, R. Hopwood, E. Ibar, R. J. Ivison, J. Liske, J. Loveday, S. J. Maddox, M. Negrello, M. W. L. Smith, E. Valiante
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  ABSTRACT: We compare the environmental and star formation properties of far-infrared detected and non--far-infrared detected galaxies out to $z \sim0.5$. Using optical spectroscopy and photometry from the Galaxy And Mass Assembly (GAMA) and Sloan Digital Sky Survey (SDSS), with far-infrared observations from the {\em Herschel}-ATLAS Science Demonstration Phase (SDP), we apply the technique of Voronoi Tessellations to analyse the environmental densities of individual galaxies. Applying statistical analyses to colour, $r-$band magnitude and redshift-matched samples, we show there to be a significant difference at the 3.5$\sigma$ level between the normalized environmental densities of these two populations. This is such that infrared emission (a tracer of star formation activity) favours underdense regions compared to those inhabited by exclusively optically observed galaxies selected to be of the same $r-$band magnitude, colour and redshift. Thus more highly star-forming galaxies are found to reside in the most underdense environments, confirming previous studies that have proposed such a correlation. However, the degeneracy between redshift and far-infrared luminosity in our flux-density limited sample means that we are unable to make a stronger statement in this respect. We then apply our method to synthetic light cones generated from semi-analytic models, finding that over the whole redshift distribution the same correlations between star-formation rate and environmental density are found.
  05/2013;
• Article: Towards understanding the relation between the gas and the attenuation in galaxies at kpc scales

  M. Boquien, A. Boselli, V. Buat, M. Baes, G. Bendo, S. Boissier, L. Ciesla, A. Cooray, L. Cortese, S. Eales, J. Koda, V. Lebouteiller, I. de Looze, M. W. L. Smith, L. Spinoglio, C. D. Wilson
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  ABSTRACT: [abridged] Aims. The aim of the present paper is to provide new and more detailed relations at the kpc scale between the gas surface density and the face-on optical depth directly calibrated on galaxies, in order to compute the attenuation not only for semi-analytic models but also observationally as new and upcoming radio observatories are able to trace gas ever farther in the Universe. Methods. We have selected a sample of 4 nearby resolved galaxies and a sample of 27 unresolved galaxies from the Herschel Reference Survey and the Very Nearby Galaxies Survey, for which we have a large set of multi-wavelength data from the FUV to the FIR including metallicity gradients for resolved galaxies, along with radio HI and CO observations. For each pixel in resolved galaxies and for each galaxy in the unresolved sample, we compute the face-on optical depth from the attenuation determined with the CIGALE SED fitting code and an assumed geometry. We determine the gas surface density from HI and CO observations with a metallicity-dependent XCO factor. Results. We provide new, simple to use, relations to determine the face-on optical depth from the gas surface density, taking the metallicity into account, which proves to be crucial for a proper estimate. The method used to determine the gas surface density or the face-on optical depth has little impact on the relations except for galaxies that have an inclination over 50d. Finally, we provide detailed instructions on how to compute the attenuation practically from the gas surface density taking into account possible information on the metallicity. Conclusions. Examination of the influence of these new relations on simulated FUV and IR luminosity functions shows a clear impact compared to older oft-used relations, which in turn could affect the conclusions drawn from studies based on large scale cosmological simulations.
  03/2013;
• Article: The Herschel PEP/HerMES Luminosity Function. I: Probing the Evolution of PACS selected Galaxies to z~4

  C. Gruppioni, F. Pozzi, G. Rodighiero, I. Delvecchio, S. Berta, L. Pozzetti, G. Zamorani, P. Andreani, A. Cimatti, O. Ilbert, [......], M. Zemcov, S. Bardelli, M. Carollo, T. Contini, O. Le Fevre, S. Lilly, V. Mainieri, A. Renzini, M. Scodeggio, E. Zucca
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  ABSTRACT: We exploit the deep and extended far infrared data sets (at 70, 100 and 160 um) of the Herschel GTO PACS Evolutionary Probe (PEP) Survey, in combination with the HERschel Multi tiered Extragalactic Survey (HerMES) data at 250, 350 and 500 um, to derive the evolution of the restframe 35 um, 60 um, 90 um, and total infrared (IR) luminosity functions (LFs) up to z~4. We detect very strong luminosity evolution for the total IR LF combined with a density evolution. In agreement with previous findings, the IR luminosity density increases steeply to z~1, then flattens between z~1 and z~3 to decrease at z greater than 3. Galaxies with different SEDs, masses and sSFRs evolve in very different ways and this large and deep statistical sample is the first one allowing us to separately study the different evolutionary behaviours of the individual IR populations contributing to the IR luminosity density. Galaxies occupying the well established SFR/stellar mass main sequence (MS) are found to dominate both the total IR LF and luminosity density at all redshifts, with the contribution from off MS sources (0.6 dex above MS) being nearly constant (~20% of the total IR luminosity density) and showing no significant signs of increase with increasing z over the whole 0.8<z<2.2 range. Sources with mass in the 10< log(M/Msun) <11 range are found to dominate the total IR LF, with more massive galaxies prevailing at the bright end of the high-z LF. A two-fold evolutionary scheme for IR galaxies is envisaged: on the one hand, a starburst-dominated phase in which the SMBH grows and is obscured by dust, is followed by an AGN dominated phase, then evolving toward a local elliptical. On the other hand, moderately starforming galaxies containing a low-luminosity AGN have various properties suggesting they are good candidates for systems in a transition phase preceding the formation of steady spiral galaxies.
  02/2013;
• Article: Galaxy And Mass Assembly (GAMA): Spectroscopic analysis

  A. M. Hopkins, S. P. Driver, S. Brough, M. S. Owers, A. E. Bauer, M. L. P. Gunawardhana, M. E. Cluver, M. Colless, C. Foster, M. A. Lara-Lopez, [......], M. Seibert, L. Staveley-Smith, W. Sutherland, E. Taylor, L. Van Waerbeke, J. A. Vazquez-Mata, S. Warren, D. B. Wijesinghe, V. Wild, S. Wilkins
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  ABSTRACT: The Galaxy And Mass Assembly (GAMA) survey is a multiwavelength photometric and spectroscopic survey, using the AAOmega spectrograph on the Anglo-Australian Telescope to obtain spectra for up to ~300000 galaxies over 280 square degrees, to a limiting magnitude of r_pet < 19.8 mag. The target galaxies are distributed over 0<z<0.5 with a median redshift of z~0.2, although the redshift distribution includes a small number of systems, primarily quasars, at higher redshifts, up to and beyond z=1. The redshift accuracy ranges from sigma_v~50km/s to sigma_v~100km/s depending on the signal-to-noise of the spectrum. Here we describe the GAMA spectroscopic reduction and analysis pipeline. We present the steps involved in taking the raw two-dimensional spectroscopic images through to flux-calibrated one-dimensional spectra. The resulting GAMA spectra cover an observed wavelength range of 3750<lambda<8850 A at a resolution of R~1300. The final flux calibration is typically accurate to 10-20%, although the reliability is worse at the extreme wavelength ends, and poorer in the blue than the red. We present details of the measurement of emission and absorption features in the GAMA spectra. These measurements are characterised through a variety of quality control analyses detailing the robustness and reliability of the measurements. We illustrate the quality of the measurements with a brief exploration of elementary emission line properties of the galaxies in the GAMA sample. We demonstrate the luminosity dependence of the Balmer decrement, consistent with previously published results, and explore further how Balmer decrement varies with galaxy mass and redshift. We also investigate the mass and redshift dependencies of the [NII]/Halpha vs [OIII]/Hbeta spectral diagnostic diagram, commonly used to discriminate between star forming and nuclear activity in galaxies.
  01/2013;
• Article: Inferring the mass of sub-millimetre galaxies by exploiting their gravitational magnification of background galaxies

  H. Hildebrandt, L. van Waerbeke, D. Scott, M. Bethermin, J. Bock, D. Clements, A. Conley, A. Cooray, J. S. Dunlop, S. Eales, [......], S. J. Oliver, M. J. Page, I. Perez-Fournon, A. J. Smith, M. Rowan-Robinson, I. Valtchanov, R. F. J. van der Burg, J. D. Vieira, M. Viero, L. Wang
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  ABSTRACT: Dust emission at sub-millimetre wavelengths allows us to trace the early phases of star formation in the Universe. In order to understand the physical processes involved in this mode of star formation, it is essential to gain knowledge about the dark matter structures - most importantly their masses - that sub-millimetre galaxies live in. Here we use the magnification effect of gravitational lensing to determine the average mass and dust content of sub-millimetre galaxies with 250mu flux densities of S_250>15mJy selected using data from the Herschel Multi-tiered Extragalactic Survey. The positions of hundreds of sub-millimetre foreground lenses are cross-correlated with the positions of background Lyman-break galaxies at z~3-5 selected using optical data from the Canada-France Hawaii Telescope Legacy Survey. We detect a cross-correlation signal at the 7-sigma level over a sky area of one square degree, with ~80% of this signal being due to magnification, whereas the remaining ~20% comes from dust extinction. Adopting some simple assumptions for the dark matter and dust profiles and the redshift distribution enables us to estimate the average mass of the halos hosting the sub-millimetre galaxies to be log(M_200/M_sun)=13.17+0.05-0.08(stat.) and their average dust mass fraction (at radii of >10kpc) to be M_dust/M_200~6x10^-5. This supports the picture that sub-millimetre galaxies are dusty, forming stars at a high rate, reside in massive group-sized halos, and are a crucial phase in the assembly and evolution of structure in the Universe.
  12/2012;
• Article: H-ATLAS: The cosmic abundance of dust from the far-infrared background power spectrum

  Cameron Thacker, Asantha Cooray, Joseph Smidt, Francesco de Bernardis, K. Mitchell-Wynne, A. Amblard, R. Auld, M. Baes, D. L. Clements, A. Dariush, [......], E. Ibar, M. Jarvis, S. Maddox, M. J. Michalowski, E. Pascale, D. Scott, S. Serjeant, M. W. L. Smith, E. Valiante, P. Van der Werf
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  ABSTRACT: We present a measurement of the angular power spectrum of the cosmic far-infrared background (CFIRB) anisotropies in one of the extragalactic fields of the Herschel Astrophysical Terahertz Large Area Survey (H-ATLAS) at 250, 350 and 500 \mu m bands. Consistent with recent measurements of the CFIRB power spectrum in Herschel-SPIRE maps, we confirm the existence of a clear one-halo term of galaxy clustering on arcminute angular scales with large-scale two-halo term of clustering at 30 arcminutes to angular scales of a few degrees. The power spectrum at the largest angular scales, especially at 250 \mu m, is contaminated by the Galactic cirrus. The angular power spectrum is modeled using a conditional luminosity function approach to describe the spatial distribution of unresolved galaxies that make up the bulk of the CFIRB. Integrating over the dusty galaxy population responsible for the background anisotropies, we find that the cosmic abundance of dust, relative to the critical density, to be between \Omega_dust=10^{-6} and 8 x 10^{-6} in the redshift range z ~ 0-3. This dust abundance is consistent with estimates of the dust content in the Universe using quasar reddening and magnification measurements in the SDSS.
  12/2012;
• Article: The SCUBA-2 Cosmology Legacy Survey: blank-field number counts of 450um-selected galaxies and their contribution to the cosmic infrared background

  J. E. Geach, E. L. Chapin, K. E. K. Coppin, J. S. Dunlop, M. Halpern, Ian Smail, P. van der Werf, S. Serjeant, D. Farrah, I. Roseboom, [......], M. J. Page, J. A. Peacock, D. Rigopoulou, E. I. Robson, M. Spaans, J. Stevens, T. M. A. Webb, C. Willott, C. D. Wilson, M. Zemcov
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  ABSTRACT: The first deep blank-field 450um map (1-sigma~1.3mJy) from the SCUBA-2 Cosmology Legacy Survey (S2CLS), conducted with the James Clerk Maxwell Telescope (JCMT) is presented. Our map covers 140 arcmin^2 of the COSMOS field, in the footprint of the HST CANDELS area. Using 60 submillimetre galaxies (SMGs) detected at >3.75-sigma, we evaluate the number counts of 450um-selected galaxies with flux densities S_450>5mJy. 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 ~200um) into the individual galaxies responsible for its emission than has previously been possible at this wavelength. At S_450>5mJy we resolve (7.4[+/-]0.7)x10^-2 MJy/sr of the CIB at 450um (equivalent to 16[+/-]7% of the absolute brightness measured by COBE at this wavelength) into point sources. A further ~40% of the CIB can be recovered through a statistical stack of 24um emitters in this field, indicating that the majority (~60%) of the CIB at 450um is emitted by galaxies with S_450>2mJy. The average redshift of 450um 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 (L_IR~1.1x10^12 L_sun). If the galaxies contributing to the statistical stack lie at similar redshifts, then the majority of the CIB at 450um is emitted by galaxies in the LIRG class with L_IR>3.6x10^11 L_sun.
  11/2012;
• Article: Herschel-ATLAS/GAMA: a difference between star-formation rates in strong-line and weak-line radio galaxies

  M. J. Hardcastle, J. H. Y. Ching, J. S. Virdee, M. J. Jarvis, S. M. Croom, E. M. Sadler, T. Mauch, D. J. B. Smith, J. A. Stevens, M. Baes, [......], S. Eales, R. Hopwood, J. Liske, S. Maddox, M. J. Michalowski, E. E. Rigby, A. S. G. Robotham, O. Steele, D. Thomas, E. Valiante
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  ABSTRACT: We have constructed a sample of radio-loud objects with optical spectroscopy from the Galaxy and Mass Assembly (GAMA) project over the Herschel-ATLAS Phase 1 fields. Classifying the radio sources in terms of their optical spectra, we find that strong-emission-line sources (`high-excitation radio galaxies') have, on average, a factor ~4 higher 250-micron Herschel luminosity than weak-line (`low-excitation') radio galaxies and are also more luminous than magnitude-matched radio-quiet galaxies at the same redshift. Using all five H-ATLAS bands, we show that this difference in luminosity between the emission-line classes arises mostly from a difference in the average dust temperature; strong-emission-line sources tend to have comparable dust masses to, but higher dust temperatures than, radio galaxies with weak emission lines. We interpret this as showing that radio galaxies with strong nuclear emission lines are much more likely to be associated with star formation in their host galaxy, although there is certainly not a one-to-one relationship between star formation and strong-line AGN activity. The strong-line sources are estimated to have star-formation rates at least a factor 3-4 higher than those in the weak-line objects. Our conclusion is consistent with earlier work, generally carried out using much smaller samples, and reinforces the general picture of high-excitation radio galaxies as being located in lower-mass, less evolved host galaxies than their low-excitation counterparts.
  11/2012;
• Article: Herschel-ATLAS/GAMA: spatial clustering of low-redshift sub-mm galaxies

  E. van Kampen, D. J. B. Smith, S. Maddox, A. M. Hopkins, I. Valtchanov, J. A. Peacock, M. J. Michalowski, P. Norberg, S. Eales, L. Dunne, [......], D. Hill, D. H. Jones, L. Kelvin, H. Parkinson, M. Prescott, R. Sharp, G. de Zotti, S. Serjeant, C. C. Popescu, R. J. Tuffs
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  ABSTRACT: We have measured the clustering properties of low-redshift (z < 0.3) sub-mm galaxies detected at 250 micron in the Herschel-ATLAS Science Demonstration Phase (SDP) field. We selected a sample for which we have high-quality spectroscopic redshifts, obtained from reliably matching the 250-micron sources to a complete (for r < 19.4) sample of galaxies from the GAMA database. Both the angular and spatial clustering strength are measured for all z < 0.3 sources as well as for five redshift slices with thickness delta z=0.05 in the range 0.05 < z < 0.3. Our measured spatial clustering length r_0 is comparable to that of optically-selected, moderately star-forming (blue) galaxies: we find values around 5 Mpc. One of the redshift bins contains an interesting structure, at z = 0.164.
  09/2012;
• Article: Herschel-ATLAS: the far-infrared properties and star-formation rates of broad absorption line quasi-stellar objects

  J. M. Cao Orjales, J. A. Stevens, M. J. Jarvis, D. J. B. Smith, M. J. Hardcastle, R. Auld, M. Baes, A. Cava, D. L. Clements, A. Cooray, [......], L. Dunne, S. Dye, S. Eales, R. Hopwood, C. Hoyos, E. Ibar, R. J. Ivison, S. Maddox, M. J. Page, E. Valiante
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  ABSTRACT: We have used data from the Herschel-ATLAS at 250, 350 and 500 \mu m to determine the far-infrared (FIR) properties of 50 Broad Absorption Line Quasars (BAL QSOs). Our sample contains 49 high-ionization BAL QSOs (HiBALs) and 1 low-ionization BAL QSO (LoBAL) which are compared against a sample of 329 non-BAL QSOs. These samples are matched over the redshift range 1.5 \leq z < 2.3 and in absolute i-band magnitude over the range -28 \leq M_{i} \leq -24. Of these, 3 BAL QSOs (HiBALs) and 27 non-BAL QSOs are detected at the > 5 sigma level. We calculate star-formation rates (SFR) for our individually detected HiBAL QSOs and the non-detected LoBAL QSO as well as average SFRs for the BAL and non-BAL QSO samples based on stacking the Herschel data. We find no difference between the HiBAL and non-BAL QSO samples in the FIR, even when separated based on differing BAL QSO classifications. Using Mrk 231 as a template, the weighted mean SFR is estimated to be \approx240\pm21 M_{\odot} yr^{-1} for the full sample, although this figure should be treated as an upper limit if AGN-heated dust makes a contribution to the FIR emission. Despite tentative claims in the literature, we do not find a dependence of {\sc C\,iv} equivalent width on FIR emission, suggesting that the strength of any outflow in these objects is not linked to their FIR output. These results strongly suggest that BAL QSOs (more specifically HiBALs) can be accommodated within a simple AGN unified scheme in which our line-of-sight to the nucleus intersects outflowing material. Models in which HiBALs are caught towards the end of a period of enhanced spheroid and black-hole growth, during which a wind terminates the star-formation activity, are not supported by the observed FIR properties.
  09/2012;
• Article: Herschel-ATLAS: Multi-wavelength SEDs and physical properties of 250 micron-selected galaxies at z < 0.5

  D. J. B. Smith, L. Dunne, E. da Cunha, K. Rowlands, S. J. Maddox, H. L. Gomez, D. G. Bonfield, S. Charlot, S. P. Driver, C. C. Popescu, [......], R. Hopwood, E. Ibar, R. J. Ivison, L. Kelvin, B. F. Madore, M. Pohlen, E. E. Rigby, A. Robotham, M. Seibert, P. Temi
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  ABSTRACT: We present a pan-chromatic analysis of an unprecedented sample of 1402 250 micron-selected galaxies at z < 0.5 (mean z = 0.24) from the Herschel-ATLAS survey. We complement our Herschel 100-500 micron data with UV-K-band photometry from the Galaxy And Mass Assembly (GAMA) survey and apply the MAGPHYS energy-balance technique to produce pan-chromatic SEDs for a representative sample of 250 micron selected galaxies spanning the most recent 5 Gyr of cosmic history. We derive estimates of physical parameters, including star formation rates, stellar masses, dust masses and infrared luminosities. The typical H-ATLAS galaxy at z < 0.5 has a far-infrared luminosity in the range 10^10 - 10^12 Lsolar (SFR: 1-50 Msolar/yr) thus is broadly representative of normal star forming galaxies over this redshift range. We show that 250 micron-selected galaxies contain a larger mass of dust at a given infra-red luminosity or star formation rate than previous samples selected at 60 micron from IRAS. We derive typical SEDs for H-ATLAS galaxies, and show that the emergent SED shape is most sensitive to specific star formation rate. The optical-UV SEDs also become more reddened due to dust at higher redshifts. Our template SEDs are significantly cooler than existing infra-red templates. They may therefore be most appropriate for inferring total IR luminosities from moderate redshift submillimetre selected samples and for inclusion in models of the lower redshift submillimetre galaxy populations.
  08/2012;
• Article: A Detailed Gravitational Lens Model Based on Submillimeter Array and Keck Adaptive Optics Imaging of a Herschel-ATLAS Sub-millimeter Galaxy at z=4.243

  R. S. Bussmann, M. A. Gurwell, Hai Fu, D. J. B. Smith, S. Dye, R. Auld, M. Baes, A. J. Baker, D. Bonfield, A. Cava, [......], E. Pascale, M. Pohlen, D. A. Riechers, E. Rigby, Douglas Scott, P. Temi, P. P. Van der Werf, A. Verma, J. Wardlow, D. Wilner
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  ABSTRACT: We present high-spatial resolution imaging obtained with the Submillimeter Array (SMA) at 880um and the Keck Adaptive Optics (AO) system at Ks-band of a gravitationally lensed sub-millimeter galaxy (SMG) at z=4.243 discovered in the Herschel-Astrophysical Terahertz Large Area Survey. The SMA data (angular resolution ~0.6") resolve the dust emission into multiple lensed images, while the Keck AO Ks-band data (angular resolution ~0.1") resolve the lens into a pair of galaxies separated by 0.3". We present an optical spectrum of the foreground lens obtained with the Gemini-South telescope that provides a lens redshift of z_lens = 0.595 +/- 0.005. We develop and apply a new lens modeling technique in the visibility plane that shows that the SMG is magnified by a factor of mu = 4.1 +/- 0.2 and has an intrinsic infrared (IR) luminosity of L_IR = (2.1 +/- 0.2) x 10^13 Lsun. We measure a half-light radius of the background source of r_s = 4.4 +/- 0.5 kpc which implies an IR luminosity surface density of Sigma_IR = (3.4 +/- 0.9) x 10^11 Lsun kpc^-2, a value that is typical of z > 2 SMGs but significantly lower than IR luminous galaxies at z~0. The two lens galaxies are compact (r_lens ~ 0.9 kpc) early-types with Einstein radii of theta_E1 = 0.57 +/- 0.01 and theta_E2 = 0.40 +/- 0.01 that imply masses of M_lens1 = (7.4 +/- 0.5) x 10^10 Msun and M_lens2 = (3.7 +/- 0.3) x 10^10 Msun. The two lensing galaxies are likely about to undergo a dissipationless merger, and the mass and size of the resultant system should be similar to other early-type galaxies at z~0.6. This work highlights the importance of high spatial resolution imaging in developing models of strongly lensed galaxies discovered by Herschel.
  07/2012;
• Source

  Available from: Glenn J. White

  Article: The JCMT Nearby Galaxies Legacy Survey VIII. CO data and the L(CO3-2)-L(FIR) correlation in the SINGS sample

  C. D. Wilson, B. E. Warren, F. P. Israel, S. Serjeant, D. Attewell, G. J. Bendo, H. M. Butner, P. Chanial, D. L. Clements, J. Golding, [......], E. Rosolowsky, E. R. Seaquist, K. Spekkens, N. Tanvir, J. M. van der Hulst, P. van der Werf, C. Vlahakis, T. M. Webb, B. Weferling, G. J. White
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  ABSTRACT: The James Clerk Maxwell Telescope Nearby Galaxies Legacy Survey (NGLS) comprises an HI-selected sample of 155 galaxies spanning all morphological types with distances less than 25 Mpc. We describe the scientific goals of the survey, the sample selection, and the observing strategy. We also present an atlas and analysis of the CO J=3-2 maps for the 47 galaxies in the NGLS which are also part of the Spitzer Infrared Nearby Galaxies Survey. We find a wide range of molecular gas mass fractions in the galaxies in this sample and explore the correlation of the far-infrared luminosity, which traces star formation, with the CO luminosity, which traces the molecular gas mass. By comparing the NGLS data with merging galaxies at low and high redshift which have also been observed in the CO J=3-2 line, we show that the correlation of far-infrared and CO luminosity shows a significant trend with luminosity. This trend is consistent with a molecular gas depletion time which is more than an order of magnitude faster in the merger galaxies than in nearby normal galaxies. We also find a strong correlation of the L(FIR)/L(CO3-2) ratio with the atomic to molecular gas mass ratio. This correlation suggests that some of the far-infrared emission originates from dust associated with atomic gas and that its contribution is particularly important in galaxies where most of the gas is in the atomic phase.
  06/2012;
• Article: The GALEX view of the Herschel Reference Survey - Ultraviolet structural properties of nearby galaxies

  L. Cortese, S. Boissier, A. Boselli, G. J. Bendo, V. Buat, J. I. Davies, S. Eales, S. Heinis, K. G. Isaak, S. C. Madden
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  ABSTRACT: We present GALEX far-ultraviolet (FUV) and near-ultraviolet (NUV) as well as SDSS g, r, i photometry and structural parameters for the Herschel Reference Survey, a magnitude-, volume-limited sample of nearby galaxies in different environments. We use this unique dataset to investigate the ultraviolet (UV) structural scaling relations of nearby galaxies and to determine how the properties of the UV disk vary with atomic hydrogen content and environment. We find a clear change of slope in the stellar mass vs. effective surface brightness relation when moving from the optical to the UV, with more massive galaxies having brighter optical but fainter UV surface brightnesses than smaller systems. A similar change of slope is also seen in the radius vs. surface brightness relation. By comparing our observations with the predictions of a simple multi-zone chemical model of galaxy evolution, we show that these findings are a natural consequence of a much more efficient inside-out growth of the stellar disk in massive galaxies. We confirm that isophotal radii are always a better proxy for the size of the stellar/star-forming disk than effective quantities and we show that the extent of the UV disk (normalized to the optical size) is strongly correlated to the integrated HI gas fraction. This relation still holds even when cluster spirals are considered, with HI-deficient systems having less extended star-forming disks than HI-normal galaxies. Interestingly, the star formation in the inner part of HI-deficient galaxies is significantly less affected by the removal of the atomic hydrogen, as expected in a simple ram-pressure stripping scenario. These results suggest that it is the amount of HI that regulates the growth of the star-forming disk in the outskirts of galaxies.
  06/2012;
• Article: HerMES: Candidate Gravitationally Lensed Galaxies and Lensing Statistics at Submillimeter Wavelengths

  Julie L. Wardlow, Asantha Cooray, Francesco De Bernardis, A. Amblard, V. Arumugam, H. Aussel, A. J. Baker, M. Béthermin, R. Blundell, J. Bock, [......], A. Strom, M. Symeonidis, M. Trichas, M. Vaccari, J. D. Vieira, M. Viero, L. Wang, C. K. Xu, L. Yan, M. Zemcov
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  ABSTRACT: We present a list of 13 candidate gravitationally lensed submillimeter galaxies (SMGs) from 95 square degrees of the Herschel Multi-tiered Extragalactic Survey, a surface density of 0.14\pm0.04deg^{-2}. The selected sources have 500um flux densities (S_500) greater than 100mJy. Gravitational lensing is confirmed by follow-up observations in 9 of the 13 systems (70%), and the lensing status of the four remaining sources is undetermined. We also present a supplementary sample of 29 (0.31\pm0.06deg^{-2}) gravitationally lensed SMG candidates with S_500=80--100mJy, which are expected to contain a higher fraction of interlopers than the primary candidates. The number counts of the candidate lensed galaxies are consistent with a simple statistical model of the lensing rate, which uses a foreground matter distribution, the intrinsic SMG number counts, and an assumed SMG redshift distribution. The model predicts that 32--74% of our S_500>100mJy candidates are strongly gravitationally lensed (mu>2), with the brightest sources being the most robust; this is consistent with the observational data. Our statistical model also predicts that, on average, lensed galaxies with S_500=100mJy are magnified by factors of ~9, with apparently brighter galaxies having progressively higher average magnification, due to the shape of the intrinsic number counts. 65% of the sources are expected to have intrinsic 500micron flux densities less than 30mJy. Thus, samples of strongly gravitationally lensed SMGs, such as those presented here, probe below the nominal Herschel detection limit at 500 micron. They are good targets for the detailed study of the physical conditions in distant dusty, star-forming galaxies, due to the lensing magnification, which can lead to spatial resolutions of ~0.01" in the source plane.
  05/2012;
• Article: Mining the Herschel-ATLAS: submillimeter-selected blazars in equatorial fields

  M. López-Caniego, J. González-Nuevo, M. Massardi, L. Bonavera, D. Herranz, M. Negrello, G. De Zotti, F. J. Carrera, L. Danese, S. Fleuren, [......], A. Dariush, L. Dunne, S. Dye, S. Eales, R. Hopwood, C. Hoyos, E. Ibar, R. J. Ivison, S. Maddox, E. Valiante
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  ABSTRACT: The Herschel Astrophysical Terahertz Large Area Survey (H-ATLAS) provides an unprecedented opportunity to search for blazars at sub-mm wavelengths. We cross-matched the FIRST radio source catalogue with the 11655 sources brighter than 35 mJy at 500{\mu}m in the \sim 135 square degrees of the sky covered by the H-ATLAS equatorial fields at 9 h and 15 h, plus half of the field at 12 h. We found that 379 of the H-ATLAS sources have a FIRST counterpart within 10 arcsec, including 8 catalogued blazars (plus one known blazar that was found at the edge of one the H-ATLAS maps). To search for additional blazar candidates we have devised new diagnostic diagrams and found that known blazars occupy a region of the log(S500{\mu}m/S350{\mu}m) vs. log(S500{\mu}m/S1.4GHz) plane separated from that of the other sub-mm sources with radio counterparts. Using this diagnostic we have selected 12 further candidates that turn out to be scattered in the (r-z) vs. (u-r) plane or in the WISE colour-colour diagram proposed by Massaro et al. (2012), where known blazars are concentrated in well defined strips. This suggests that the majority of them either are not blazars or have spectral energy distributions contaminated by their host galaxies. A significant fraction of true blazars are found to be hosted by star-forming galaxies. This finding, supported by an analysis of blazars detected in Planck 545 and 857 GHz bands, is at odds with the notion that blazar hosts are passive ellipticals and indicates that the sub-mm selection is providing a novel prospect on blazar properties. Based on an inspection of the available photometric data, including the WISE all-sky survey, the unpublished VIKING survey and new radio observations, we tentatively estimate that there are 11 blazars with synchrotron flux density S500{\mu}m > 35mJy over the considered area. This result already allows us to constrain blazar evolution models.
  05/2012;
• Article: Submillimetre Photometry of 323 Nearby Galaxies from the Herschel Reference Survey

  L. Ciesla, A. Boselli, M. W. L. Smith, G. J. Bendo, L. Cortese, S. Eales, S. Bianchi, M. Boquien, V. Buat, J. Davies, [......], M. Galametz, H. L. Gomez, V. Lebouteiller, S. C. Madden, C. Pappalardo, A. Remy, L. Spinoglio, M. Vaccari, R. Auld, D. L. Clements
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  ABSTRACT: The Herschel Reference Survey (HRS) is a guaranteed time Herschel key project aimed at studying the physical properties of the interstellar medium in galaxies of the nearby universe. This volume limited, K-band selected sample is composed of galaxies spanning the whole range of morphological types (from ellipticals to late-type spirals) and environments (from the field to the centre of the Virgo Cluster). We present flux density measurements of the whole sample of 323 galaxies of the HRS in the three bands of the Spectral and Photometric Imaging Receiver (SPIRE), at 250, 350 and 500 microns. Aperture photometry is performed on extended galaxies and point spread function (PSF) fitting on timeline data for unresolved objects; we carefully estimate errors and upper limits. The flux densities are found to be in good agreement with those of the HeViCS and KINGFISH key projects in all SPIRE bands, and of the Planck consortium at 350 and 550 microns, for the galaxies in common. This submillimetre catalogue of nearby galaxies is a benchmark for the study of the dust properties in the local universe, giving the zero redshift reference for any cosmological survey.
  04/2012;
• Article: Blind detections of CO J = 1--0 in 11 H-ATLAS galaxies at z = 2.1--3.5 with the GBT/Zpectrometer

  A. I. Harris, A. J. Baker, D. T. Frayer, Ian Smail, A. M. Swinbank, D. A. Riechers, P. P. van der Werf, R. Auld, M. Baes, R. S. Bussmann, [......], R. Hopwood, E. Ibar, R. J. Ivison, M. J. Jarvis, S. Maddox, M. Negrello, E. Rigby, D. J. B. Smith, P. Temi, J. Wardlow
  [show abstract] [hide abstract]
  ABSTRACT: We report measurements of the carbon monoxide ground state rotational transition (12C16O J = 1--0) with the Zpectrometer ultra-wideband spectrometer on the 100-m diameter Green Bank Telescope. The sample comprises 11 galaxies with redshifts between z = 2.1 and 3.5 from a total sample of 24 targets identified by Herschel-ATLAS photometric colors from the SPIRE instrument. Nine of the CO measurements are new redshift determinations, substantially adding to the number of detections of galaxies with rest-frame peak submillimeter emission near 100um. The CO detections confirm the existence of massive gas reservoirs within these luminous dusty star-forming galaxies (DSFGs). The CO redshift distribution of the 350um-selected galaxies is strikingly similar to the optical redshifts of 850um-selected submillimeter galaxies (SMGs) in 2.1 < z < 3.5. Spectroscopic redshifts break a temperature-redshift degeneracy; optically thin dust models fit to the far-infrared photometry indicate characteristic dust temperatures near 34 K for most of the galaxies we detect in CO. Detections of two warmer galaxies and statistically significant nondetections hint at warmer or molecule-poor DSFGs with redshifts difficult determine from from Herschel-SPIRE photometric colors alone. Many of the galaxies identified by H-ATLAS photometry are expected to be amplified by foreground gravitational lenses. Analysis of CO linewidths and luminosities provides a method for finding approximate gravitational lens magnifications mu from spectroscopic data alone, yielding mu ~ 3--20. Corrected for magnification, most galaxy luminosities are consistent with an ultra-luminous infrared galaxy (ULIRG) classification, but three are candidate hyper-LIRGs with luminosities greater than 10^13 L_sun.
  04/2012;
• Article: Herschel-ATLAS: Planck sources in the Phase 1 fields

  D. Herranz, J. González-Nuevo, D. L. Clements, M. Clemens, G. De Zotti, M. López-Caniego, A. Lapi, G. Rodighiero, L. Danese, H. Fu, [......], I. Valtchanov, P. Van der Werf, R. Auld, S. Buttiglione, A. Dariush, L. Dunne, R. Hopwood, C. Hoyos, E. Ibar, S. Maddox
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  ABSTRACT: We present the results of a cross-correlation of the Planck Early Release Compact Source Catalog (ERCSC) with the catalog of Herschel-ATLAS sources detected in the Phase 1 fields, covering 134.55 deg2. There are 28 ERCSC sources detected by Planck at 857 GHz in this area. As many as 16 of them are probably high Galactic latitude cirrus; 10 additional sources can be clearly identified as bright, low-z galaxies; one further source is resolved by Herschel as two relatively bright sources; and the last is resolved into an unusual condensation of low-flux, probably high-redshift point sources, around a strongly lensed Herschel-ATLAS source at z = 3.26. Our results demonstrate that the higher sensitivity and higher angular resolution H-ATLAS maps provide essential information for the interpretation of candidate sources extracted from Planck sub-mm maps.
  04/2012;
• Article: Herschel-ATLAS: Toward a Sample of ~1000 Strongly Lensed Galaxies

  J González-Nuevo, A Lapi, S Fleuren, S Bressan, L Danese, G De Zotti, M Negrello, Z -Y Cai, L Fan, W Sutherland, [......], A Dariush, J Fritz, R Hopwood, E Ibar, S Maddox, E Pascale, M Pohlen, E Rigby, D Smith, P Temi
  apj. 04/2012; 749:65.