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Browsing by Author "Rigopoulou, D."

Now showing 1 - 11 of 11
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    The Complex Physics of Dusty Star-Forming Galaxies at High Redshifts as Revealed by Herschel and Spitzer
    Lo Faro, B.; Franceschini, A.; Vaccari, M.; Silva, L.; Rodighiero, G.; Berta, S.; Bock, J.; Burgarella, D.; Buat, V.; Cava, A.; Clements, D. L.; Cooray, A.; Farrah, D.; Feltre, A.; Solares, E. A. G.; Hurley, P.; Lutz, D.; Magdis, G. E.; Magnelli, B.; Marchetti, L.; Oliver, S. J.; Page, M. J.; Popesso, P.; Pozzi, F.; Rigopoulou, D.; Rowan-Robinson, M.; Roseboom, I. G.; Scott, D.; Smith, A. J.; Symeonidis, M.; Wang, L.; Wuyts, S. (IOP Publishing Ltd., 2013-01)
    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 similar to 1 and 2 selected in GOODS-S with 24 mu m 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 <= 100 M-circle dot 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 Delta A(V) similar to 0.81 and 1.14) and higher stellar masses (by Delta log(M-*) similar to 0.16 and 0.36 dex) for z similar to 1 and z similar to 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 (similar to 73% and similar to 66% of the total L-IR for z similar to 1 and z similar to 2 (U)LIRGs, respectively).
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    Diagnostics of AGN-driven molecular outflows in ULIRGs from Herschel-PACS observations of OH at 119 μm
    Spoon, H. W. W.; Farrah, D.; Lebouteiller, V.; Gonzalez-Alfonso, E.; Bernard-Salas, J.; Urrutia, T.; Rigopoulou, D.; Westmoquette, M. S.; Smith, H. A.; Afonso, J.; Pearson, C.; Cormier, D.; Efstathiou, A.; Borys, C.; Verma, A.; Etxaluze, M.; Clements, D. L. (IOP Publishing Ltd., 2013-10)
    We report on our observations of the 79 and 119 mu m doublet transitions of OH for 24 local (z < 0.262) ULIRGs observed with Herschel-PACS as part of the Herschel ULIRG Survey (HERUS). Some OH 119 mu m profiles display a clear P-Cygni shape and therefore imply outflowing OH gas, while other profiles are predominantly in absorption or are completely in emission. We find that the relative strength of the OH emission component decreases as the silicate absorption increases. This result locates the OH outflows inside the obscured nuclei. The maximum outflow velocities for our sources range from less than 100 to similar to 2000 km s(-1), with 15/24 (10/24) sources showing OH absorption at velocities exceeding 700 km s(-1) (1000 km s(-1)). Three sources show maximum OH outflow velocities exceeding that of Mrk231. Since outflow velocities above 500-700 km s(-1) are thought to require an active galactic nucleus (AGN) to drive them, about two-thirds of our ULIRG sample may host AGN-driven molecular outflows. This finding is supported by the correlation we find between the maximum OH outflow velocity and the IR-derived bolometric AGN luminosity. No such correlation is found with the IR-derived star formation rate. The highest outflow velocities are found among sources that are still deeply embedded. We speculate that the molecular outflows in these sources may be in an early phase of disrupting the nuclear dust veil before these sources evolve into less-obscured AGNs. Four of our sources show high-velocity wings in their [C II] fine-structure line profiles, implying neutral gas outflow masses of at least (2-4.5) x 10(8) M-circle dot.
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    Far-infrared fine-structure line diagnostics of ultraluminous infrared galaxies
    Farrah, D.; Lebouteiller, V.; Spoon, H. W. W.; Bernard-Salas, J.; Pearson, C.; Rigopoulou, D.; Smith, H. A.; Gonzalez-Alfonso, E.; Clements, D. L.; Efstathiou, A.; Cormier, D.; Afonso, J.; Petty, S. M.; Harris, K.; Hurley, P.; Borys, C.; Verma, A.; Cooray, A.; Salvatelli, V. (IOP Publishing Ltd., 2013-10)
    We present Herschel observations of 6 fine-structure lines in 25 ultraluminous infrared galaxies at z < 0.27. The lines, [O III]52 mu m, [N III] 57 mu m, [O I]63 mu m, [N II]122 mu m, [O I]145 mu m, and [C II]158 mu m, are mostly single Gaussians with widths < 600 km s(-1) and luminosities of 10(7)-10(9) L-circle dot. There are deficits in the [O I] 63/L-IR, [N II]/L-IR, [O I]145/L-IR, and [C II]/L-IR ratios compared to lower luminosity systems. The majority of the line deficits are consistent with dustier H II regions, but part of the [C II] deficit may arise from an additional mechanism, plausibly charged dust grains. This is consistent with some of the [C II] originating from photodissociation regions or the interstellar medium (ISM). We derive relations between far-IR line luminosities and both the IR luminosity and star formation rate. We find that [N II] and both [O I] lines are good tracers of the IR luminosity and star formation rate. In contrast, [C II] is a poor tracer of the IR luminosity and star formation rate, and does not improve as a tracer of either quantity if the [C II] deficit is accounted for. The continuum luminosity densities also correlate with the IR luminosity and star formation rate. We derive ranges for the gas density and ultraviolet radiation intensity of 10(1) < n < 10(2.5) and 10(2.2) < G(0) < 10(3.6), respectively. These ranges depend on optical type, the importance of star formation, and merger stage. We do not find relationships between far-IR line properties and several other parameters: active galactic nucleus (AGN) activity, merger stage, mid-IR excitation, and SMBH mass. We conclude that these far-IR lines arise from gas heated by starlight, and that they are not strongly influenced by AGN activity.
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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.
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    HerMES: candidate high-redshift galaxies discovered with Herschel/SPIRE
    Dowell, C. D.; Conley, A.; Glenn, J.; Arumugam, V.; Asboth, V.; Aussel, H.; Bertoldi, F.; Bethermin, M.; Bock, J.; Boselli, A.; Bridge, C. R.; 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. A.; Rigopoulou, D.; Roseboom, I. G.; Rowan-Robinson, M.; Sayers, J.; Schulz, B.; Scott, D.; 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. (IOP Publishing Ltd., 2014-01)
    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
    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. (IOP Publishing Ltd., 2013-07)
    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 far-infrared emission from dust-obscured galaxies
    Calanog, J. A.; Wardlow, J.; Fu, H.; Cooray, A.; Assef, R. J.; Bock, J.; Casey, C. M.; Conley, A.; Farrah, D.; Ibar, E.; Kartaltepe, J.; Magdis, G. E.; Marchetti, L.; Oliver, S. J.; Perez-Fournon, I.; Riechers, D. A.; Rigopoulou, D.; Roseboom, I. G.; Schulz, B.; Scott, D.; Symeonidis, M.; Vaccari, M.; Viero, M.; Zemcov, M. (IOP Publishing Ltd., 2013-09)
    Dust-obscured galaxies (DOGs) are an ultraviolet-faint, infrared-bright galaxy population that reside at z similar to 2 and are believed to be in a phase of dusty star-forming and active galactic nucleus (AGN) activity. We present far-infrared (far-IR) observations of a complete sample of DOGs in the 2 deg(2) of the Cosmic Evolution Survey. The 3077 DOGs have < z > = 1.9 +/- 0.3 and are selected from 24 mu m and r(+) observations using a color cut of r(+) -[24] >= 7.5 (AB mag) and S-24 >= 100 mu Jy. Based on the near-IR spectral energy distributions, 47% are bump DOGs (star formation dominated) and 10% are power-law DOGs (AGN-dominated). We use SPIRE far-IR photometry from the Herschel Multi-tiered Extragalactic Survey to calculate the IR luminosity and characteristic dust temperature for the 1572 (51%) DOGs that are detected at 250 mu m (>= 3 sigma). For the remaining 1505 (49%) that are undetected, we perform a median stacking analysis to probe fainter luminosities. Herschel-detected and undetected DOGs have average luminosities of (2.8 +/- 0.4) x 10(12) L-circle dot and (0.77 +/- 0.08) x 10(12) L-circle dot, and dust temperatures of (33 +/- 7) K and (37 +/- 5) K, respectively. The IR luminosity function for DOGs with S-24 >= 100 mu Jy is calculated, using far-IR observations and stacking. DOGs contribute 10%-30% to the total star formation rate (SFR) density of the universe at z = 1.5-2.5, dominated by 250 mu m detected and bump DOGs. For comparison, DOGs contribute 30% to the SFR density for all z = 1.5-2.5 galaxies with S-24 >= 100 mu Jy. DOGs have a large scatter about the star formation main sequence and their specific SFRs show that the observed phase of star formation could be responsible for their total observed stellar mass at z similar to 2.
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    HERSCHEL observations of far-infrared cooling lines in intermediate redshift (ultra)-luminous infrared galaxies
    Rigopoulou, D.; Hopwood, R.; Magdis, G. E.; Thatte, N.; Swinyard, B. M.; Farrah, D.; Huang, J. S.; Alonso-Herrero, A.; Bock, J. J.; Clements, D. L.; Cooray, A.; Griffin, M. J.; Oliver, S.; Pearson, C.; Riechers, D. A.; Scott, D.; Smith, A.; Vaccari, M.; Valtchanov, I.; Wang, L. (IOP Publishing Ltd., 2014-01)
    We report the first results from a spectroscopic survey of the [C II] 158 mu m line from a sample of intermediate redshift (0.2 < z < 0.8) (ultra)-luminous infrared galaxies, (U) LIRGs (L-IR > 10(11.5) L-circle dot), using the Spectral and Photometric Imaging REceiver-Fourier Transform Spectrometer on board the Herschel Space Observatory. This is the first survey of [C II] emission, an important tracer of star formation, at a redshift range where the star formation rate density of the universe increases rapidly. We detect strong [C II] 158 mu m line emission from over 80% of the sample. We find that the [C II] line is luminous, in the range (0.8-4) x 10(-3) of the far-infrared continuum luminosity of our sources, and appears to arise from photodissociation regions on the surface of molecular clouds. The L-[C II]/L-IR ratio in our intermediate redshift (U) LIRGs is on average similar to 10 times larger than that of local ULIRGs. Furthermore, we find that the L-[C II]/L-IR and L-[C II]/LCO(1-0) ratios in our sample are similar to those of local normal galaxies and high-z star-forming galaxies. ULIRGs at z similar to 0.5 show many similarities to the properties of local normal and high-z star-forming galaxies. Our findings strongly suggest that rapid evolution in the properties of the star-forming regions of (U) LIRGs is likely to have occurred in the last 5 billion years.
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    Mid- to far-infrared properties of star-forming galaxies and active galactic nuclei
    Magdis, G. E.; Rigopoulou, D.; Helou, G.; Farrah, D.; Hurley, P.; Alonso-Herrero, A.; Bock, J.; Burgarella, D.; Chapman, S.; Charmandaris, V.; Cooray, A.; Dai, Y. S.; Dale, D.; Elbaz, D.; Feltre, A.; Hatziminaoglou, E.; Huang, J. S.; Morrison, G.; Oliver, S.; Page, M.; Scott, D.; Shi, Y. (EDP SCIENCES, 2013-10)
    We study the mid- to far-IR properties of a 24 mu m-selected flux-limited sample (S-24 > 5mJy) of 154 intermediate redshift (< z > similar to 0.15), infrared luminous galaxies, drawn from the 5 Milli-Jansky Unbiased Spitzer Extragalactic Survey. By combining existing mid-IR spectroscopy and new Herschel SPIRE submm photometry from the Herschel Multi-tiered Extragalactic Survey, we derived robust total infrared luminosity (L-IR) and dust mass (M-dust) estimates and infered the relative contribution of the AGN to the infrared energy budget of the sources. We found that the total (8-1000 mu m) infrared emission of galaxies with weak 6.2 mu m PAH emission (EW6.2 <= 0.2 mu m) is dominated by AGN activity, while for galaxies with EW6.2 > 0.2 mu m more than 50% of the L-IR arises from star formation. We also found that for galaxies detected in the 250-500 mu m Herschel bands an AGN has a statistically insignificant effect on the temperature of the cold dust and the far-IR colours of the host galaxy, which are primarily shaped by star formation activity. For star-forming galaxies we reveal an anti-correlation between the L-IR-to-rest-frame 8 mu m luminosity ratio, IR8 = L-IR/L-8 and the strength of PAH features. We found that this anti-correlation is primarily driven by variations in the PAHs emission, and not by variations in the 5-15 mu m mid-IR continuum emission. Using the [NeIII]/[NeII] line ratio as a tracer of the hardness of the radiation field, we confirm that galaxies with harder radiation fields tend to exhibit weaker PAH features, and found that they have higher IR8 values and higher dust-mass-weighted luminosities (L-IR/M-dust), the latter being a proxy for the dust temperature (T-d). We argue that these trends originate either from variations in the environment of the star-forming regions or are caused by variations in the age of the starburst. Finally, we provide scaling relations that will allow estimating L-IR, based on single-band observations with the mid-infrared instrument, on board the upcoming James Webb Space Telescope.
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    A Population of z > 2 Far-Infrared Herschel-Spire-Selected Starbursts
    Casey, C. M.; Berta, S.; Bethermin, M.; Bock, J.; Bridge, C. R.; Burgarella, D.; Chapin, E.; Chapman, S. C.; Clements, D. L.; Conley, A.; Conselice, C. J.; Cooray, A.; Farrah, D.; Hatziminaoglou, E.; Ivison, R. J.; Le Floc'h, E.; Lutz, D.; Magdis, G. E.; Magnelli, B.; Oliver, S. J.; Page, M. J.; Pozzi, F.; Rigopoulou, D.; Riguccini, L.; Roseboom, I. G.; Sanders, D. B.; Scott, D.; Seymour, N.; Valtchanov, I.; Vieira, J. D.; Viero, M.; Wardlow, J. (IOP Publishing Ltd., 2012-12)
    We present spectroscopic observations for a sample of 36 Herschel-Spire 250-500 mu m selected galaxies (HSGs) at 2 < z < 5 from the Herschel Multi-tiered Extragalactic Survey. Redshifts are confirmed as part of a large redshift survey of Herschel-Spire-selected sources covering similar to 0.93 deg(2) in six extragalactic legacy fields. Observations were taken with the Keck I Low Resolution Imaging Spectrometer and the Keck II DEep Imaging Multi-Object Spectrograph. Precise astrometry, needed for spectroscopic follow-up, is determined by identification of counterparts at 24 mu m or 1.4 GHz using a cross-identification likelihood matching method. Individual source luminosities range from log(L-IR/L-circle dot) = 12.5-13.6 (corresponding to star formation rates (SFRs) 500-9000M(circle dot) yr(-1), assuming a Salpeter initial mass function), constituting some of the most intrinsically luminous, distant infrared galaxies discovered thus far. We present both individual and composite rest-frame ultraviolet spectra and infrared spectral energy distributions. The selection of these HSGs is reproducible and well characterized across large areas of the sky in contrast to most z > 2 HyLIRGs in the literature, which are detected serendipitously or via tailored surveys searching only for high-z HyLIRGs; therefore, we can place lower limits on the contribution of HSGs to the cosmic star formation rate density (SFRD) at (7 +/- 2) x 10(-3) M-circle dot yr(-1) h(3) Mpc(-3) at z similar to 2.5, which is > 10% of the estimated total SFRD of the universe from optical surveys. The contribution at z similar to 4 has a lower limit of 3 x 10(-3) M-circle dot yr(-1) h(3) Mpc(-3), greater than or similar to 20% of the estimated total SFRD. This highlights the importance of extremely infrared-luminous galaxies with high SFRs to the buildup of stellar mass, even at the earliest epochs.
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    A redshift survey of Herschel far-infrared selected starbursts and implications for obscured star formation
    Casey, C. M.; Berta, S.; Bethermin, M.; Bock, J.; Bridge, C. R.; Budynkiewicz, J.; Burgarella, D.; Chapin, E.; Chapman, S. C.; Clements, D. L.; Conley, A.; Conselice, C. J.; Cooray, A.; Farrah, D.; Hatziminaoglou, E.; Ivison, R. J.; Le Floc'h, E.; Lutz, D.; Magdis, G. E.; Magnelli, B.; Oliver, S. J.; Page, M. J.; Pozzi, F.; Rigopoulou, D.; Riguccini, L.; Roseboom, I. G.; Sanders, D. B.; Scott, D.; Seymour, N.; Valtchanov, I.; Vieira, J. D.; Viero, M.; Wardlow, J. (IOP Publishing Ltd., 2012-12)
    We present Keck spectroscopic observations and redshifts for a sample of 767 Herschel-SPIRE selected galaxies (HSGs) at 250, 350, and 500 mu m, taken with the Keck I Low Resolution Imaging Spectrometer and the Keck II DEep Imaging Multi-Object Spectrograph. The redshift distribution of these SPIRE sources from the Herschel Multitiered Extragalactic Survey peaks at z = 0.85, with 731 sources at z < 2 and a tail of sources out to z similar to 5. We measure more significant disagreement between photometric and spectroscopic redshifts ( = 0.29) than is seen in non-infrared selected samples, likely due to enhanced star formation rates and dust obscuration in infrared-selected galaxies. The infrared data are used to directly measure integrated infrared luminosities and dust temperatures independent of radio or 24 mu m flux densities. By probing the dust spectral energy distribution (SED) at its peak, we estimate that the vast majority (72%-83%) of z < 2 Herschel-selected galaxies would drop out of traditional submillimeter surveys at 0.85-1 mm. We find that dust temperature traces infrared luminosity, due in part to the SPIRE wavelength selection biases, and partially from physical effects. As a result, we measure no significant trend in SPIRE color with redshift; if dust temperature were independent of luminosity or redshift, a trend in SPIRE color would be expected. Composite infrared SEDs are constructed as a function of infrared luminosity, showing the increase in dust temperature with luminosity, and subtle change in near-infrared and mid-infrared spectral properties. Moderate evolution in the far-infrared (FIR)/radio correlation is measured for this partially radio-selected sample, with q(IR) proportional to (1 + z)(-0.30 +/- 0.02) at z < 2. We estimate the luminosity function and implied star formation rate density contribution of HSGs at z < 1.6 and find overall agreement with work based on 24 mu m extrapolations of the LIRG, ULIRG, and total infrared contributions. This work significantly increased the number of spectroscopically confirmed infrared-luminous galaxies at z >> 0 and demonstrates the growing importance of dusty starbursts for galaxy evolution studies and the build-up of stellar mass throughout cosmic time.