Browsing by Author "Ivison, R.J."

Now showing 1 - 6 of 6
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    HerMES: Candidate gravitationally lensed galaxies and lensing statistics at submillimeter wavelengths
    (American Astronomical Society, 2013) Wardlow, Julie L.; Cooray, Asantha; De Bernardis, Francesco; Amblard, A.; Arumugam, V.; Aussel, H.; Baker, A.J.; Bethermin, M.; Blundell, R.; Bock, J.; Boselli, A.; Bridge, C.; Buat, V.; Burgarella, D.; Bussmann, R.S.; Cabrera-Lavers, A.; Calanog, J.A.; Carpenter, J.M.; Casey, C.M.; Castro-Rodríguez, N.; Cava, A.; Chanial, P.; Chapin, E.; Chapman, S.C.; Clements, D.L.; Conley, A.; Cox, P.; Dowell, C.D.; Dye, S.; Eales, S.; Farrah, D.; Ferrero, P.; Franceschini, Alberto; Frayer, D.T.; Frazer, C.; Fu, Hai; Gavazzi, R.; Glenn, J.; González Solares, E.A.; Griffin, M.; Gurwell, M.A.; Harris, A.I.; Hatziminaoglou, Evanthia; Hopwood, R.; Hyde, A.; Ibar, Edo; Ivison, R.J.; Kim, S.; Lagache, G.; Levenson, L.; Marchetti, L.; Marsden, G.; Martinez-Navajas, P.; Negrello, M.; Neri, R.; Nguyen, H.T.; OHalloran, B.; Oliver, S.J.; Omont, A.; Page, Matthew J.; Panuzzo, P.; Papageorgiou, A.; Pearson, C.P.; Perez-Fournon, E.; Pohlen, M.; Riechers, D.; Rigopoulou, D.; Roseboom, I.G.; Rowan-Robinson, M.; Schulz, B.; Scott, Douglas; Scoville, N.; Seymour, N.; Shupe, D.L.; Smith, A.J.; Streblyanska, A.; Strom, A.; Symeonidis, Myrto; Trichas, M.; Vaccari, M.; Vieira, J.D.; Viero, M. P.; Wang, L.; Xu, C.K.; Zemcov, M.; Yan, L.
    Gravitational lensing increases the angular size and integrated flux of affected sources. It is exploited to investigate the mass distribution of the foreground lensing structures and the properties of the background lensed galaxies (see reviews by Bartelmann 2010; Treu 2010). The magnification provided by gravitational lensing makes it an effective tool for identifying and studying intrinsically faint and typically distant galaxies (e.g., Stark et al. 2007; Richard et al. 2008, 2011). The flux boost from lensing yields an improved detection, and the associated spatial enhancement increases the ability to investigate the internal structure of distant galaxies to levels otherwise unattainable with the current generation of instrumentation (e.g., Riechers et al. 2008; Swinbank et al. 2010, 2011; Gladders et al. 2012). Furthermore, gravitational lensing probes the total mass of the foreground deflectors, including the relative content of dark and luminous mass. In combination with dynamical studies, lensing mass reconstruction allows one to obtain the density profile of the dark matter in individual lensing galaxies down to ~10 kpc scales (e.g., Miralda-Escude 1995; Dalal & Kochanek 2002; Metcalf & Zhao 2002; Rusin & Kochanek 2005; Treu & Koopmans 2004).
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    Hermes: Cosmic infrared background anisotropies and the clustering of dusty star-forming galaxies
    (American Astronomical Society, 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, Asantha; de Zotti, G.; Dowell, C.D.; Farrah, D.; Franceschini, Alberto; Glenn, J.; Griffin, M.; Hatziminaoglou, Evanthia; Heinis, S.; Ibar, Edo; Ivison, R.J.; Lagache, G.; Levenson, L.; Marchetti, L.; Marsden, G.; Nguyen, H.T.; OHalloran, B.; Oliver, S.J.; Omont, A.; Page, Matthew J.; Papageorgiou, A.; Pearson, C.P.; Perez-Fournon, I.; Pohlen, M.; Rigopoulou, D.; Roseboom, I.G.; Rowan-Robinson, M.; Schulz, B.; Scott, Douglas; Seymour, N.; Shupe, D.L.; Smith, A.J.; Symeonidis, Myrto; Vaccari, M.; Valtchanov, I.; Vieira, J.D.; Wardlow, Julie L.; Xu, C.K.
    Star formation is well traced by dust, which absorbs the UV/optical light produced by young stars in actively starforming regions and re-emits the energy in the far-infrared/ submillimeter (FIR/submm; e.g., Savage & Mathis 1979). Roughly half of all starlight ever produced has been reprocessed by dusty star-forming galaxies (DSFGs; e.g., Hauser & Dwek 2001; Dole et al. 2006), and this emission is responsible for the ubiquitous cosmic infrared background (CIB; Puget et al. 1996; Fixsen et al. 1998). The mechanisms responsible for the presence or absence of star formation are partially dependent on the local environment (e.g., major mergers: Narayanan et al. 2010; condensation or cold accretion: Dekel et al. 2009, photoionization heating, supernovae, active galactic nuclei, and virial shocks: Birnboim & Dekel 2003; Granato et al. 2004; Bower et al. 2006). Thus, the specifics of the galaxy distribution—which can be determined statistically to high precision by measuring their clustering properties—inform the relationship of star formation and dark matter density, and are valuable inputs for models of galaxy formation. However, measuring the clustering of DSFGs has historically proven difficult to do.
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    HerMES: The contribution to the cosmic infrared background from galaxies selected by mass and redshift
    (American Astronomical Society, 2013) Viero, M. P.; Monclesi, L.; Quadri, L.F.; Arumugam, V.; Assef, R.J.; Bethermin, M.; Bock, J.; Bridge, C.; Casey, C.M.; Conley, A.; Cooray, Asantha; Farrah, D.; Glenn, J.; Heinis, S.; Ibar, Edo; Ikarashi, S.; Ivison, R.J.; Kohno, K.; Marsden, G.; Oliver, S.J.; Roseboom, I.G.; Schulz, B.; Scott, Douglas; Serra, P.; Vaccari, M.; Vieira, J.D.; Wang, L.; Wardlow, Julie L.; Wilson, G.W.; Yun, M.S.; Zemcov, M.
    The cosmic infrared background (CIB), discovered in Far Infrared Absolute Spectrophotometer (FIRAS) data from the Cosmic Background Explorer (COBE; Puget et al. 1996; Fixsen et al. 1998), originates from thermal re-radiation of imagine cutting out hundreds of thumbnails from a map centered on the positions where galaxies are known to be, and averaging those thumbnails together until an image of the average galaxy emerges from the noise. These positional priors can come in many forms, e.g., they could be catalogs of UV, optical, IR, or radio sources. Note that the output is the average of that population in the stacked maps, i.e., there will likely be sources whose actual fluxes are higher or lower. Thus, the more homogeneous the sources comprising the input list, the more meaningful the stacked flux will be.
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    The Herschel* view of the environment of the radio galaxy 4C+41.17 at z = 3.8
    (Oxford University Press, 2013) Wylezalek, D.; Vernet, J.; De Breuck, C.; Stern, D.; Galametz, A.; Seymour, N.; Jarvis, Matt; Barthel, P.; Drouart, G.; Rottgering, H.J.A.; Greve, T.R.; Haas, M.; Hatch, N.; Ivison, R.J.; Lehnert, M.; Meisenheimer, K.; Miley, G.; Nesvadba, N.; Stevens, J.A.
    We present Herschel observations at 70, 160, 250, 350 and 500 μm of the environment of the radio galaxy 4C+41.17 at z = 3.792. About 65 per cent of the extracted sources are securely identified with mid-infrared sources observed with the Spitzer Space Telescope at 3.6, 4.5, 5.8, 8 and 24 μm.We derive simple photometric redshifts, also including existing 850 and 1200 μm data, using templates of active galactic nuclei, starburst-dominated systems and evolved stellar populations. We find that most of the Herschel sources are foreground to the radio galaxy and therefore do not belong to a structure associated with 4C+41.17. We do, however, find that the spectral energy distribution (SED) of the closest (∼25 arcsec offset) source to the radio galaxy is fully consistent with being at the same redshift as 4C+41.17. We show that finding such a bright source that close to the radio galaxy at the same redshift is a very unlikely event, making the environment of 4C+41.17 a special case. We demonstrate that multiwavelength data, in particular on the Rayleigh–Jeans side of the SED, allow us to confirm or rule out the presence of protocluster candidates that were previously selected by single wavelength data sets.
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    Herschel*-ATLAS: correlations between dust and gas in local submm-selected galaxies
    (2013) Dunne, L.; Bourne, N.; Bendo, G.J.; Smith, M.W.L.; Clark, C.J.R.; Smith, Daniel J.B.; Rigby, E.E.; Baes, M.; Leeuw, L.L.; Maddox, S.J.; Thompson, M.A.; Bremer, M.N.; Cooray, Asantha; Dariush, A.; de Zotti, G.; Dye, S.; Eales, S.; Hopwood, R.; Ibar, Edo; Ivison, R.J.; Jarvis, Matt; Michalowski, M.J.; Rowlands, K.; Valiante, E.
    We present an analysis of CO molecular gas tracers in a sample of 500 μ m-selected Herschel -ATLAS galaxies at z < 0 . 05 ( cz < 14990 km s − 1 ). Using 22 − 500 μ m photom- etry from WISE , IRAS and Herschel , with H i 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 FIR–submm fl uxes weakens with increasing IR wavelength ( λ & 60 μ m), as a result of colder dust being less strongly associated with dense gas. Conversely, CO(2–1) and H i line fluxes both ap- pear to be better correlated with longer wavelengths, suggesting that cold dust is more strongly associated with diffuse atomic and molecular gas phases, co nsistent with it being at least partially heated by radiation from old stellar populations . The increased scatter at long wavelengths implies that sub-millimetre fluxes are a po orer tracer of SFR. Fluxes at 22 and 60 μ m are also better correlated with diffuse gas tracers than dense CO(3–2), probably due to very-small-grain emission in the diffu se interstellar medium, which is not correlated with SFR. The FIR/CO luminosity ratio a nd the dust mass/CO luminosity ratio both decrease with increasing luminosit y, 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: A binary HyLIRG pinpointing a cluster of starbursting protoellipticals
    (American Astronomical Society, 2013) Ivison, R.J.; Swinbank, A.M.; Jarvis, Matt
    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 ≈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 ∼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 Mdyn of several ×1011M , and gas fractions of ∼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 5×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 ≈1014.6-M cluster.