Browsing by Author "Marchetti, L."
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Item The complex physics of dusty star-forming galaxies at high redshifts as revealed by Herschel and Spitzer(IOP Publishing, 2013) Lo Faro, Barbara; Franceschini, Alberto; Vaccari, M.; Silva, L.; Rodighiero, G.; Berta, S.; Bock, J.; Burgarella, D.; Buat, V.; Cava, A.; Clements, D.L.; Cooray, Asantha; Farrah, D.; Feltre, Anna; Gonzalez-Solares, Eduardo A.; Hurley, P.; Lutz, D.; Magdis, G.; Magnelli, B.; Marchetti, L.; Oliver, S.J.; Page, Matthew J.; Popesso, P.; Pozzi, F.; Rigopoulou, D.; Rowan-Robinson, M.; Roseboom, I.G.; Scott, Douglas; Smith, A.J.; Symeonidis, Myrto; Wang, L.; Wuyts, S.We combine far-infrared photometry from Herschel (PEP/HerMES) with deep mid-infrared spectroscopy from Spitzer to investigate the nature and the mass assembly history of a sample of 31 luminous and ultraluminous infrared galaxies ((U)LIRGs) at z ∼ 1 and 2 selected in GOODS-S with 24μm fluxes between 0.2 and 0.5 mJy.We model the data with a self-consistent physical model (GRASIL) which includes a state-of-the-art treatment of dust extinction and reprocessing. We find that all of our galaxies appear to require massive populations of old (>1 Gyr) stars and, at the same time, to host a moderate ongoing activity of star formation (SFR 100M yr−1). The bulk of the stars appear to have been formed a few Gyr before the observation in essentially all cases. Only five galaxies of the sample require a recent starburst superimposed on a quiescent star formation history.We also find discrepancies between our results and those based on optical-only spectral energy distribution (SED) fitting for the same objects; by fitting their observed SEDs with our physical model we find higher extinctions (by ΔAV ∼ 0.81 and 1.14) and higher stellar masses (by Δlog(M ) ∼ 0.16 and 0.36 dex) for z ∼ 1 and z ∼ 2 (U)LIRGs, respectively. The stellar mass difference is larger for the most dust-obscured objects. We also find lower SFRs than those computed from LIR using the Kennicutt relation due to the significant contribution to the dust heating by intermediate-age stellar populations through “cirrus” emission (∼73% and ∼66% of the total LIR for z ∼ 1 and z ∼ 2 (U)LIRGs, respectively).Item 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).Item 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.Item HerMES: The far-infrared emission from dust-obscured galaxies(American Astronomical Society, 2013) Calanog, J.A.; Wardlow, Julie L.; Fu, Hai; Cooray, Asantha; Assef, R.J.; Bock, J.; Casey, C.M.; Conley, A.; Farrah, D.; Ibar, Edo; Kartaltepe, J.; Magdis, G.; Marchetti, L.; Oliver, S.J.; Perez-Fournon, I.; Riechers, D.; Rigopoulou, D.; Roseboom, I.G.; Schulz, B.; Scott, Douglas; Symeonidis, Myrto; Vaccari, M.; Viero, M. P.; Zemcov, M.The far-infrared (far-IR) luminosities of luminous infrared galaxies (LIRGs) and ultra-LIRGs (ULIRGs) are dominated by reprocessed thermal dust emission, due to a combination of star formation and active galactic nucleus (AGN) activity, with star formation typically being the more dominant component (e.g., Watabe et al. 2009; Elbaz et al. 2010). Locally, these sources are rare, although out to z - 1 they become more numerous and increasingly dominate the IR luminosity function of galaxies with increasing redshift (e.g., Le Floc’h et al. 2005; P´erez-Gonz´alez et al. 2005; Caputi et al. 2007; Magnelli et al. 2009; Rodighiero et al. 2010; Eales et al. 2010). (U)LIRGs are thought to trace a phase of intense star formation activity, which is likely followed by, or partially concurrent with, an episode of vigorous black hole accretion. It is postulated that upon the cessation of these phases, each produces an early-type galaxy (Genzel et al. 2001; Farrah et al. 2003; Lonsdale et al. 2006; Veilleux et al. 2009).Item NOEMA redshift measurements of bright Herschel galaxies(EDP Sciences, 2020) Marchetti, L.; Neri, R.; Cox, P.Using the IRAM NOrthern Extended Millimeter Array (NOEMA), we conducted a program to measure redshifts for 13 bright galaxies detected in the Herschel Astrophysical Large Area Survey with S500 μm ≥ 80 mJy. We report reliable spectroscopic redshifts for 12 individual sources, which are derived from scans of the 3 and 2 mm bands, covering up to 31 GHz in each band, and are based on the detection of at least two emission lines. The spectroscopic redshifts are in the range 2.08 < z < 4.05 with a median value of z = 2.9 ± 0.6. The sources are unresolved or barely resolved on scales of 10 kpc. In one field, two galaxies with different redshifts were detected. In two cases the sources are found to be binary galaxies with projected distances of ∼140 kpc.Item Revised SWIRE photometric redshifts(Oxford University Press, 2013) Rowan-Robinson, Michael; Gonzalez-Solares, Eduardo A.; Vaccari, Mattia; Marchetti, L.We have revised the Spitzer Wide-Area Infrared Extragalactic survey (SWIRE) Photometric Redshift Catalogue to take account of new optical photometry in several of the SWIRE areas, and incorporating Two Micron All Sky Survey (2MASS) and UKIRT Infrared Deep Sky Survey (UKIDSS) near-infrared data. Aperture matching is an important issue for combining near-infrared and optical data, and we have explored a number of methods of doing this. The increased number of photometric bands available for the redshift solution results in improvements both in the rms error and, especially, in the outlier rate. We have also found that incorporating the dust torus emission into the quasi-stellar object (QSO) templates improves the performance for QSO redshift estimation. Our revised redshift catalogue contains over 1 million extragalactic objects, of which 26 288 are QSOs.Item The roles of star formation and AGN activity of IRS sources in the HerMES fields(Oxford University Press, 2013) Feltre, Anna; Hatziminaoglou, Evanthia; Vaccari, Mattia; Hernán-Caballero, Antonio; Fritz, Jacopo; Franceschini, Alberto; Bock, J.; Cooray, Asantha; Farrah, Duncan; Gonzalez-Solares, Eduardo A.; Ibar, Edo; Isaak, Kate G.; Lo Faro, Barbara; Marchetti, L.; Oliver, Seb J.; Page, Matthew J.; Rigopoulou, Dimitra; Roseboom, Isaac G.; Symeonidis, MyrtoIn 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 these same galaxies. To do this we apply a multi-component, multi-band spectral synthesis technique to a sample of 250 μm selected galaxies of the HerschelMulti- tiered Extragalactic Survey (HerMES), with 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-fit hot dust (torus) model. We find a correlation between the obscured star formation rate (SFR) derived from the IR luminosity of the starburst component, SFRIR and SFRPAH, derived from the luminosity of the PAH features, LPAH, with SFRFIR taking higher values than SFRPAH. The correlation is different for AGN- and starburst-dominated objects. The ratio of LPAH to that of the starburst component, LPAH/LSB, is almost constant for AGN-dominated objects but decreases with increasing LSB for starburst-dominated objects. SFRFIR increases with the accretion luminosity, Lacc, with the increase less prominent for the very brightest, unobscured AGN-dominated sources. We find no correlation between the masses of the hot (AGN-heated) and cold (starburstheated) dust components. We interpret this as a non-constant fraction of gas driven by the gravitational effects to the AGN while the starburst is ongoing. We also find no evidence of the AGN affecting the temperature of the cold dust component, though this conclusion is mostly based on objects with a non-dominantAGN component.We conclude that our findings do not provide evidence that the presence of AGN affects the star formation process in the host galaxy, but rather that the two phenomena occur simultaneously over a wide range of luminosities.