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Browsing by Author "Eales, S."

Now showing 1 - 3 of 3
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    The evolution of the dust and gas content in galaxies
    Santini, P.; Maiolino, R.; Magnelli, B.; Lutz, D.; Lamastra, A.; Causi, G. L.; Eales, S.; Andreani, P.; Berta, S.; Buat, V.; Cooray, A.; Cresci, G.; Daddi, E.; Farrah, D.; Fontana, A.; Franceschini, A.; Genzel, R.; Granato, G.; Grazian, A.; Le Floc'h, E.; Magdis, G. E.; Magliocchetti, M.; Mannucci, F.; Menci, N.; Nordon, R.; Oliver, S.; Popesso, P.; Pozzi, F.; Riguccini, L.; Rodighiero, G.; Rosario, D. J.; Salvato, M.; Scott, D.; Silva, L.; Tacconi, L.; Viero, M.; Wang, L.; Wuyts, S.; Xu, K. (EDP SCIENCES, 2014-02)
    We use deep Herschel observations taken with both PACS and SPIRE imaging cameras to estimate the dust mass of a sample of galaxies extracted from the GOODS-S, GOODS-N and the COSMOS fields. We divide the redshift-stellar mass (M-star)-star formation rate (SFR) parameter space into small bins and investigate average properties over this grid. In the first part of the work we investigate the scaling relations between dust mass, stellar mass and SFR out to z = 2.5. No clear evolution of the dust mass with redshift is observed at a given SFR and stellar mass. We find a tight correlation between the SFR and the dust mass, which, under reasonable assumptions, is likely a consequence of the Schmidt-Kennicutt (S-K) relation. The previously observed correlation between the stellar content and the dust content flattens or sometimes disappears when considering galaxies with the same SFR. Our finding suggests that most of the correlation between dust mass and stellar mass obtained by previous studies is likely a consequence of the correlation between the dust mass and the SFR combined with the main sequence, i.e., the tight relation observed between the stellar mass and the SFR and followed by the majority of star-forming galaxies. We then investigate the gas content as inferred from dust mass measurements. We convert the dust mass into gas mass by assuming that the dust-to-gas ratio scales linearly with the gas metallicity (as supported by many observations). For normal star-forming galaxies (on the main sequence) the inferred relation between the SFR and the gas mass (integrated S-K relation) broadly agrees with the results of previous studies based on CO measurements, despite the completely different approaches. We observe that all galaxies in the sample follow, within uncertainties, the same S-K relation. However, when investigated in redshift intervals, the S-K relation shows a moderate, but significant redshift evolution. The bulk of the galaxy population at z similar to 2 converts gas into stars with an efficiency (star formation efficiency, SFE = SFR/M-gas, equal to the inverse of the depletion time) about 5 times higher than at z similar to 0. However, it is not clear what fraction of such variation of the SFE is due to an intrinsic redshift evolution and what fraction is simply a consequence of high-z galaxies having, on average, higher SFR, combined with the super-linear slope of the S-K relation (while other studies find a linear slope). We confirm that the gas fraction (f(gas) = M-gas/(M-gas + M-star)) decreases with stellar mass and increases with the SFR. We observe no evolution with redshift once M-star and SFR are fixed. We explain these trends by introducing a universal relation between gas fraction, stellar mass and SFR that does not evolve with redshift, at least out to z similar to 2.5. Galaxies move across this relation as their gas content evolves across the cosmic epochs. We use the 3D fundamental f(gas)-M-star-SFR relation, along with the evolution of the main sequence with redshift, to estimate the evolution of the gas fraction in the average population of galaxies as a function of redshift and as a function of stellar mass: we find that M-star greater than or similar to 10(11) M-circle dot galaxies show the strongest evolution at z greater than or similar to 1. 3 and a flatter trend at lower redshift, while f(gas) decreases more regularly over the entire redshift range probed in M-star less than or similar to 10(11) M-circle dot galaxies, in agreement with a downsizing scenario.
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    Gravitational lens models based on submillimeter array imaging of Herschel-selected strongly lensed sub-millimeter galaxies at z > 1.5
    Bussmann, R. S.; Perez-Fournon, I.; Amber, S.; Calanog, J. A.; Gurwell, M. A.; Dannerbauer, H.; De Bernardis, F.; Fu, H.; Harris, A. I.; Krips, M.; Lapi, A.; Maiolino, R.; Omont, A.; Riechers, D. A.; 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. G.; Hopwood, R.; Ibar, E.; Ivison, R. J.; Laporte, N.; Maddox, S.; Martinez-Navajas, P.; Michalowski, M. J.; Negrello, M.; Oliver, S. J.; Roseboom, I. G.; Scott, D.; Serjeant, S.; Smith, A. J.; Smith, M.; Streblyanska, A.; Valiante, E.; van der Werf, P.; Verma, A.; Vieira, J. D.; Wang, L.; Wilner, D. (IOP Publishing Ltd., 2013-12)
    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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    HerMES: candidate gravitationally lensed galaxies and lensing statistics at submillimeter wavelengths
    Wardlow, J. L.; Cooray, A.; De Bernardis, F.; Amblard, A.; Arumugam, V.; Aussel, H.; Baker, A. J.; Bethermin, M.; Blundell, R.; Bock, J.; Boselli, A.; Bridge, C. R.; Buat, V.; Burgarella, D.; Bussmann, R. S.; Cabrera-Lavers, A.; Calanog, J. A.; Carpenter, J. M.; Casey, C. M.; Castro-Rodriguez, 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, A.; Frayer, D. T.; Frazer, C.; Fu, H.; Gavazzi, R.; Glenn, J.; Solares, E. A. G.; Griffin, M.; Gurwell, M. A.; Harris, A. I.; Hatziminaoglou, E.; Hopwood, R.; Hyde, A.; Ibar, E.; Ivison, R. J.; Kim, S.; Lagache, G.; Levenson, L.; Marchetti, L.; Marsden, G.; Martinez-Navajas, P.; Negrello, M.; Neri, R.; Nguyen, H. T.; O'Halloran, B.; Oliver, S. J.; Omont, A.; Page, M. J.; Panuzzo, P.; Papageorgiou, A.; Pearson, C. P.; Perez-Fournon, I.; Pohlen, M.; Riechers, D. A.; Rigopoulou, D.; Roseboom, I. G.; Rowan-Robinson, M.; Schulz, B.; Scott, D.; Scoville, N.; Seymour, N.; Shupe, D. L.; Smith, A. J.; Streblyanska, A.; Strom, A.; Symeonidis, M.; Trichas, M.; Vaccari, M.; Vieira, J. D.; Viero, M.; Wang, L.; Xu, C. K.; Yan, L.; Zemcov, M. (IOP Publishing Ltd., 2013-01)
    We present a list of 13 candidate gravitationally lensed submillimeter galaxies (SMGs) from 95 deg(2) of the Herschel Multi-tiered Extragalactic Survey, a surface density of 0.14 +/- 0.04 deg(-2). The selected sources have 500 mu m flux densities (S-500) greater than 100 mJy. 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 +/- 0.06 deg(-2)) gravitationally lensed SMG candidates with S-500 = 80-100 mJy, 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 >= 100 mJy 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 = 100 mJy are magnified by factors of similar to 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 500 mu m flux densities less than 30 mJy. Thus, samples of strongly gravitationally lensed SMGs, such as those presented here, probe below the nominal Herschel detection limit at 500 mu m. 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 similar to 0 ''.01 in the source plane.