Publications by Dimitra Rigopoulou


The JCMT Nearby Galaxies Legacy Survey - VIII. CO data and the L CO(3-2)-L FIR correlation in the SINGS sample

Monthly Notices of the Royal Astronomical Society (2012)

CD Wilson, BE Warren, FP Israel, S Serjeant, D Attewell, GJ Bendo, HM Butner, P Chanial, DL Clements, J Golding, V Heesen, J Irwin, J Leech, HE Matthews, S Mühle, AMJ Mortier, G Petitpas, JR Sánchez-Gallego, E Sinukoff, K Shorten, BK Tan, RPJ Tilanus, A Usero, M Vaccari, T Wiegert, M Zhu, DM Alexander, P Alexander, M Azimlu, P Barmby, R Brar, C Bridge, E Brinks, S Brooks, K Coppin, S Côté, P Côté, S Courteau, J Davies, S Eales, M Fich, M Hudson, DH Hughes, RJ Ivison, JH Knapen, M Page, TJ Parkin, D Rigopoulou, E Rosolowsky, ER Seaquist, K Spekkens, N Tanvir, JM van der Hulst, P van der Werf, C Vlahakis, TM Webb, B Weferling, GJ White


HerMES: Deep number counts at 250 μm, 350 μm and 500 μm in the COSMOS and GOODS-N fields and the build-up of the cosmic infrared background

Astronomy and Astrophysics 542 (2012)

M Béthermin, E Le Floc'H, O Ilbert, A Conley, G Lagache, A Amblard, V Arumugam, H Aussel, S Berta, J Bock, A Boselli, V Buat, CM Casey, N Castro-Rodríguez, A Cava, DL Clements, A Cooray, CD Dowell, S Eales, D Farrah, A Franceschini, J Glenn, M Griffin, E Hatziminaoglou, S Heinis, E Ibar, RJ Ivison, JS Kartaltepe, L Levenson, G Magdis, L Marchetti, G Marsden, HT Nguyen, B O'Halloran, SJ Oliver, A Omont, MJ Page, P Panuzzo, A Papageorgiou, CP Pearson, I Pérez-Fournon, M Pohlen, D Rigopoulou, IG Roseboom, M Rowan-Robinson, M Salvato, B Schulz, D Scott, N Seymour, DL Shupe, AJ Smith, M Symeonidis, M Trichas, KE Tugwell, M Vaccari, I Valtchanov, JD Vieira, M Viero, L Wang, CK Xu, M Zemcov

Aims. The Spectral and Photometric Imaging REceiver (SPIRE) onboard the Herschel space telescope has provided confusion limited maps of deep fields at 250 μm, 350 μm, and 500 μm, as part of the Herschel Multi-tiered Extragalactic Survey (HerMES). Unfortunately, due to confusion, only a small fraction of the cosmic infrared background (CIB) can be resolved into individually-detected sources. Our goal is to produce deep galaxy number counts and redshift distributions below the confusion limit at SPIRE wavelengths (∼20 mJy), which we then use to place strong constraints on the origins of the cosmic infrared background and on models of galaxy evolution. Methods. We individually extracted the bright SPIRE sources (>20 mJy) in the COSMOS field with a method using the positions, the flux densities, and the redshifts of the 24 μm sources as a prior, and derived the number counts and redshift distributions of the bright SPIRE sources. For fainter SPIRE sources (<20 mJy), we reconstructed the number counts and the redshift distribution below the confusion limit using the deep 24 μm catalogs associated with photometric redshift and information provided by the stacking of these sources into the deep SPIRE maps of the GOODS-N and COSMOS fields. Finally, by integrating all these counts, we studied the contribution of the galaxies to the CIB as a function of their flux density and redshift. Results. Through stacking, we managed to reconstruct the source counts per redshift slice down to ∼2 mJy in the three SPIRE bands, which lies about a factor 10 below the 5σ confusion limit. Our measurements place tight constraints on source population models. None of the pre-existing models are able to reproduce our results at better than 3-σ. Finally, we extrapolate our counts to zero flux density in order to derive an estimate of the total contribution of galaxies to the CIB, finding 10.1 -2.3+2.6 nW m -2 sr -1, 6.5 -1.6+1.7 nW m -2 sr -1, and 2.8 -0.8+0.9 nW m -2 sr -1 at 250 μm, 350 μm, and 500 μm, respectively. These values agree well with FIRAS absolute measurements, suggesting our number counts and their extrapolation are sufficient to explain the CIB. We find that half of the CIB is emitted at z = 1.04, 1.20, and 1.25, respectively. Finally, combining our results with other works, we estimate the energy budget contained in the CIB between 8 μm and 1000 μm: 26 -3+7 nW m -2 sr -1. © 2012 ESO.


Ultra Steep Spectrum Radio Sources in the Lockman Hole: SERVS Identifications and Redshift Distribution at the Faintest Radio Fluxes

SQUARE KILOMETRE ARRAY: PAVING THE WAY FOR THE NEW 21ST CENTURY RADIO ASTRONOMY PARADIGM (2012) 97-100

J Afonso, L Bizzocchi, E Ibar, M Grossi, C Simpson, S Chapman, MJ Jarvis, H Rottgering, RP Norris, J Dunlop, RJ Ivison, H Messias, J Pforr, M Vaccari, N Seymour, P Best, E Gonzalez-Solares, D Farrah, CAC Fernandes, J-S Huang, M Lacy, C Marastron, L Marchetti, J-C Mauduit, S Oliver, D Rigopoulou, SA Stanford, J Surace, G Zeimann


The Spitzer Extragalactic Representative Volume Survey (SERVS): Survey Definition and Goals (vol 124, pg 714, 2012)

PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF THE PACIFIC 124 (2012) 1135-1136

J-C Mauduit, M Lacy, D Farrah, JA Surace, M Jarvis, S Oliver, C Maraston, M Vaccari, L Marchetti, G Zeimann, EA Gonzales-Solares, J Pforr, AO Petric, B Henriques, PA Thomas, J Afonso, A Rettura, G Wilson, JT Falder, JE Geach, M Huynh, RP Norris, N Seymour, GT Richards, SA Stanford, DM Alexander, RH Becker, PN Best, L Bizzocchi, D Bonfield, N Castro, A Cava, S Chapman, N Christopher, DL Clements, G Covone, N Dubois, JS Dunlop, E Dyke, A Edge, HC Ferguson, S Foucaud, A Franceschini, RR Gal, JK Grant, M Grossi, E Hatziminaoglou, S Hickey, JA Hodge, J-S Huang, RJ Ivison, M Kim, O LeFevre, M Lehnert, CJ Lonsdale, LM Lubin, RJ McLure, H Messias, A Martinez-Sansigre, AMJ Mortier, DM Nielsen, M Ouchi, G Parish, I Perez-Fournon, M Pierre, S Rawlings, A Readhead, SE Ridgway, D Rigopoulou, AK Romer, IG Rosebloom, HJA Rottgering, M Rowan-Robinson, A Sajina, CJ Simpson, I Smail, GK Squires, JA Stevens, R Taylor, M Trichas, T Urrutia, E van Kampen, A Verma, CK Xu


The molecular gas content of z = 3 lyman break galaxies: Evidence of a non-evolving gas fraction in main-sequence galaxies at z &gt; 2

Astrophysical Journal Letters 758 (2012)

GE Magdis, E Daddi, M Sargent, D Elbaz, R Gobat, H Dannerbauer, C Feruglio, Q Tan, D Rigopoulou, V Charmandaris, M Dickinson, N Reddy, H Aussel

We present observations of the CO[J = 3 → 2] emission toward two massive and infrared luminous Lyman break galaxies (LBGs) at z = 3.21 and z = 2.92, using the IRAM Plateau de Bure Interferometer, placing first constraints on the molecular gas masses (M gas) of non-lensed LBGs. Their overall properties are consistent with those of typical (main-sequence) galaxies at their redshifts, with specific star formation rates 1.6 and 2.2Gyr-1, despite their large infrared luminosities (L IR (2-3) × 1012L) derived from Herschel. With one plausible CO detection (spurious detection probability of 10-3) and one upper limit, we investigate the evolution of the molecular gas-to-stellar mass ratio (M gas/M *) with redshift. Our data suggest that the steep evolution of M gas/M * of normal galaxies up to z 2 is followed by a flattening at higher redshifts, providing supporting evidence for the existence of a plateau in the evolution of the specific star formation rate at z > 2.5. © 2012. The American Astronomical Society. All rights reserved.


The JCMT Nearby Galaxies Legacy Survey - VIII. CO data and the L <inf>CO(3-2)</inf>-L <inf>FIR</inf> correlation in the SINGS sample

Monthly Notices of the Royal Astronomical Society 424 (2012) 3050-3080

CD Wilson, BE Warren, FP Israel, S Serjeant, D Attewell, GJ Bendo, HM Butner, P Chanial, DL Clements, J Golding, V Heesen, J Irwin, J Leech, HE Matthews, S Mühle, AMJ Mortier, G Petitpas, JR Sánchez-Gallego, E Sinukoff, K Shorten, BK Tan, RPJ Tilanus, A Usero, M Vaccari, T Wiegert, M Zhu, DM Alexander, P Alexander, M Azimlu, P Barmby, R Brar, C Bridge, E Brinks, S Brooks, K Coppin, S Côté, P Côté, S Courteau, J Davies, S Eales, M Fich, M Hudson, DH Hughes, RJ Ivison, JH Knapen, M Page, TJ Parkin, D Rigopoulou, E Rosolowsky, ER Seaquist, K Spekkens, N Tanvir, JM van der Hulst, P van der Werf, C Vlahakis, TM Webb, B Weferling, GJ White

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 25Mpc. 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 CO(3-2) 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. © 2012 The Authors Monthly Notices of the Royal Astronomical Society © 2012 RAS.


A population of dust-rich quasars at z ∼ 1.5

Astrophysical Journal 753 (2012)

YS Dai, J Bergeron, M Elvis, A Omont, JS Huang, J Bock, A Cooray, G Fazio, E Hatziminaoglou, E Ibar, GE Magdis, SJ Oliver, MJ Page, I Perez-Fournon, D Rigopoulou, IG Roseboom, D Scott, M Symeonidis, M Trichas, JD Vieira, CNA Willmer, M Zemcov

We report Herschel SPIRE (250, 350, and 500 μm) detections of 32 quasars with redshifts 0.5 ≤z < 3.6 from the Herschel Multi-tiered Extragalactic Survey (HerMES). These sources are from a MIPS 24 μm flux-limited sample of 326 quasars in the Lockman Hole Field. The extensive multi-wavelength data available in the field permit construction of the rest-frame spectral energy distributions (SEDs) from ultraviolet to the mid-infrared for all sources, and to the far-infrared (FIR) for the 32 objects. Most quasars with Herschel FIR detections show dust temperatures in the range of 25-60K, with a mean of 34K. The FIR luminosities range from 1011.3 to 1013.5 L, qualifying most of their hosts as ultra- or hyper-luminous infrared galaxies. These FIR-detected quasars may represent a dust-rich population, but with lower redshifts and fainter luminosities than quasars observed at 1mm. However, their FIR properties cannot be predicted from shorter wavelengths (0.3-20 μm, rest frame), and the bolometric luminosities derived using the 5100Å index may be underestimated for these FIR-detected quasars. Regardless of redshift, we observed a decline in the relative strength of FIR luminosities for quasars with higher near-infrared luminosities. © 2012. The American Astronomical Society. All rights reserved.


PHOTOMETRY AND PHOTOMETRIC REDSHIFT CATALOGS FOR THE LOCKMAN HOLE DEEP FIELD

ASTROPHYSICAL JOURNAL SUPPLEMENT SERIES 198 (2012) ARTN 1

S Fotopoulou, M Salvato, G Hasinger, E Rovilos, M Brusa, E Egami, D Lutz, V Burwitz, JP Henry, JH Huang, D Rigopoulou, M Vaccari


The Herschel Multi-tiered Extragalactic Survey: HerMES

Monthly Notices of the Royal Astronomical Society (2012)

SJ Oliver, J Bock, B Altieri, A Amblard, V Arumugam, H Aussel, T Babbedge, A Beelen, M Béthermin, A Blain, A Boselli, C Bridge, D Brisbin, V Buat, D Burgarella, N Castro-Rodríguez, A Cava, P Chanial, M Cirasuolo, DL Clements, A Conley, L Conversi, A Cooray, CD Dowell, EN Dubois, E Dwek, S Dye, S Eales, D Elbaz, D Farrah, A Feltre, P Ferrero, N Fiolet, M Fox, A Franceschini, W Gear, E Giovannoli, J Glenn, Y Gong, EA González Solares, M Griffin, M Halpern, M Harwit, E Hatziminaoglou, S Heinis, P Hurley, HS Hwang, A Hyde, E Ibar, O Ilbert, K Isaak, RJ Ivison, G Lagache, E Le Floc'h, L Levenson, BL Faro, N Lu, S Madden, B Maffei, G Magdis, G Mainetti, L Marchetti, G Marsden, J Marshall, AMJ Mortier, HT Nguyen, B O'Halloran, A Omont, MJ Page, P Panuzzo, A Papageorgiou, H Patel, CP Pearson, I Pérez-Fournon, M Pohlen, JI Rawlings, G Raymond, D Rigopoulou, L Riguccini, D Rizzo, G Rodighiero, IG Roseboom, M Rowan-Robinson, M Sánchez Portal, B Schulz, D Scott, N Seymour, DL Shupe, AJ Smith, JA Stevens, M Symeonidis, M Trichas, KE Tugwell, M Vaccari, I Valtchanov, JD Vieira, M Viero, L Vigroux, L Wang, R Ward, J Wardlow, G Wright, CK Xu, M Zemcov


A POPULATION OF DUST-RICH QUASARS AT z similar to 1.5

ASTROPHYSICAL JOURNAL 753 (2012) ARTN 33

YS Dai, J Bergeron, M Elvis, A Omont, J-S Huang, J Bock, A Cooray, G Fazio, E Hatziminaoglou, E Ibar, GE Magdis, SJ Oliver, MJ Page, I Perez-Fournon, D Rigopoulou, IG Roseboom, D Scott, M Symeonidis, M Trichas, JD Vieira, CNA Willmer, M Zemcov


LOCAL LUMINOUS INFRARED GALAXIES. II. ACTIVE GALACTIC NUCLEUS ACTIVITY FROM SPITZER/INFRARED SPECTROGRAPH SPECTRA

ASTROPHYSICAL JOURNAL 744 (2012) ARTN 2

A Alonso-Herrero, M Pereira-Santaella, GH Rieke, D Rigopoulou


The Herschel Multi-tiered Extragalactic Survey: HerMES

Monthly Notices of the Royal Astronomical Society 424 (2012) 1614-1635

SJ Oliver, J Bock, B Altieri, A Amblard, V Arumugam, H Aussel, T Babbedge, A Beelen, M Béthermin, A Blain, A Boselli, C Bridge, D Brisbin, V Buat, D Burgarella, N Castro-Rodríguez, A Cava, P Chanial, M Cirasuolo, DL Clements, A Conley, L Conversi, A Cooray, CD Dowell, EN Dubois, E Dwek, S Dye, S Eales, D Elbaz, D Farrah, A Feltre, P Ferrero, N Fiolet, M Fox, A Franceschini, W Gear, E Giovannoli, J Glenn, Y Gong, EA González Solares, M Griffin, M Halpern, M Harwit, E Hatziminaoglou, S Heinis, P Hurley, HS Hwang, A Hyde, E Ibar, O Ilbert, K Isaak, RJ Ivison, G Lagache, E Le Floc'h, L Levenson, BL Faro, N Lu, S Madden, B Maffei, G Magdis, G Mainetti, L Marchetti, G Marsden, J Marshall, AMJ Mortier, HT Nguyen, B O'Halloran, A Omont, MJ Page, P Panuzzo, A Papageorgiou, H Patel, CP Pearson, I Pérez-Fournon, M Pohlen, JI Rawlings, G Raymond, D Rigopoulou, L Riguccini, D Rizzo, G Rodighiero, IG Roseboom, M Rowan-Robinson, M Sánchez Portal, B Schulz, D Scott, N Seymour, DL Shupe, AJ Smith, JA Stevens, M Symeonidis, M Trichas, KE Tugwell, M Vaccari, I Valtchanov, JD Vieira, M Viero, L Vigroux, L Wang, R Ward

The Herschel Multi-tiered Extragalactic Survey (HerMES) is a legacy programme designed to map a set of nested fields totalling ~380deg 2 . Fields range in size from 0.01 to ~20deg 2 , using the Herschel-Spectral and Photometric Imaging Receiver (SPIRE) (at 250, 350 and 500μm) and the Herschel-Photodetector Array Camera and Spectrometer (PACS) (at 100 and 160μm), with an additional wider component of 270deg 2 with SPIRE alone. These bands cover the peak of the redshifted thermal spectral energy distribution from interstellar dust and thus capture the reprocessed optical and ultraviolet radiation from star formation that has been absorbed by dust, and are critical for forming a complete multiwavelength understanding of galaxy formation and evolution. The survey will detect of the order of 100000 galaxies at 5σ in some of the best-studied fields in the sky. Additionally, HerMES is closely coordinated with the PACS Evolutionary Probe survey. Making maximum use of the full spectrum of ancillary data, from radio to X-ray wavelengths, it is designed to facilitate redshift determination, rapidly identify unusual objects and understand the relationships between thermal emission from dust and other processes. Scientific questions HerMES will be used to answer include the total infrared emission of galaxies, the evolution of the luminosity function, the clustering properties of dusty galaxies and the properties of populations of galaxies which lie below the confusion limit through lensing and statistical techniques. This paper defines the survey observations and data products, outlines the primary scientific goals of the HerMES team, and reviews some of the early results. © 2012 The Authors. Monthly Notices of the Royal Astronomical Society © 2012 RAS.


The suppression of star formation by powerful active galactic nuclei.

Nature 485 (2012) 213-216

MJ Page, M Symeonidis, JD Vieira, B Altieri, A Amblard, V Arumugam, H Aussel, T Babbedge, A Blain, J Bock, A Boselli, V Buat, N Castro-Rodríguez, A Cava, P Chanial, DL Clements, A Conley, L Conversi, A Cooray, CD Dowell, EN Dubois, JS Dunlop, E Dwek, S Dye, S Eales, D Elbaz, D Farrah, M Fox, A Franceschini, W Gear, J Glenn, M Griffin, M Halpern, E Hatziminaoglou, E Ibar, K Isaak, RJ Ivison, G Lagache, L Levenson, N Lu, S Madden, B Maffei, G Mainetti, L Marchetti, HT Nguyen, B O'Halloran, SJ Oliver, A Omont, P Panuzzo, A Papageorgiou, CP Pearson, I Pérez-Fournon, M Pohlen, JI Rawlings, D Rigopoulou, L Riguccini, D Rizzo, G Rodighiero, IG Roseboom, M Rowan-Robinson, M Sánchez Portal, B Schulz, D Scott, N Seymour, DL Shupe, AJ Smith, JA Stevens, M Trichas, KE Tugwell, M Vaccari, I Valtchanov, M Viero, L Vigroux, L Wang, R Ward, G Wright, CK Xu, M Zemcov

The old, red stars that constitute the bulges of galaxies, and the massive black holes at their centres, are the relics of a period in cosmic history when galaxies formed stars at remarkable rates and active galactic nuclei (AGN) shone brightly as a result of accretion onto black holes. It is widely suspected, but unproved, that the tight correlation between the mass of the black hole and the mass of the stellar bulge results from the AGN quenching the surrounding star formation as it approaches its peak luminosity. X-rays trace emission from AGN unambiguously, whereas powerful star-forming galaxies are usually dust-obscured and are brightest at infrared and submillimetre wavelengths. Here we report submillimetre and X-ray observations that show that rapid star formation was common in the host galaxies of AGN when the Universe was 2-6 billion years old, but that the most vigorous star formation is not observed around black holes above an X-ray luminosity of 10(44) ergs per second. This suppression of star formation in the host galaxy of a powerful AGN is a key prediction of models in which the AGN drives an outflow, expelling the interstellar medium of its host and transforming the galaxy's properties in a brief period of cosmic time.


The starburst-active galactic nucleus connection in the merger galaxy Mrk 938: an infrared and X-ray view

MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY 423 (2012) 185-196

P Esquej, A Alonso-Herrero, AM Perez-Garcia, M Pereira-Santaella, D Rigopoulou, M Sanchez-Portal, M Castillo, CR Almeida, D Coia, B Altieri, JA Acosta-Pulido, L Conversi, JI Gonzalez-Serrano, E Hatziminaoglou, M Povic, JM Rodriguez-Espinosa, I Valtchanov


A redshift survey of herschel far-infrared selected starbursts and implications for obscured star formation

Astrophysical Journal 761 (2012)

CM Casey, S Berta, M Béthermin, J Bock, C Bridge, J Budynkiewicz, D Burgarella, E Chapin, SC Chapman, DL Clements, A Conley, CJ Conselice, A Cooray, D Farrah, E Hatziminaoglou, RJ Ivison, E Le Floc'H, D Lutz, G Magdis, B Magnelli, SJ Oliver, MJ Page, F Pozzi, D Rigopoulou, L Riguccini, IG Roseboom, DB Sanders, D Scott, N Seymour, I Valtchanov, JD Vieira, M Viero, J Wardlow

We present Keck spectroscopic observations and redshifts for a sample of 767 Herschel-SPIRE selected galaxies (HSGs) at 250, 350, and 500 μm, 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 ∼ 5. We measure more significant disagreement between photometric and spectroscopic redshifts (〈Δz/(1 + zspec)〉 = 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 μm 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 qIR∝(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 μm 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. © 2012. The American Astronomical Society. All rights reserved..


A population of z &gt; 2 far-infrared Herschel-SPIRE-selected starbursts

Astrophysical Journal 761 (2012)

CM Casey, S Berta, M Béthermin, J Bock, C Bridge, D Burgarella, E Chapin, SC Chapman, DL Clements, A Conley, CJ Conselice, A Cooray, D Farrah, E Hatziminaoglou, RJ Ivison, EL Floc'H, D Lutz, G Magdis, B Magnelli, SJ Oliver, MJ Page, F Pozzi, D Rigopoulou, L Riguccini, IG Roseboom, DB Sanders, D Scott, N Seymour, I Valtchanov, JD Vieira, M Viero, J Wardlow

We present spectroscopic observations for a sample of 36 Herschel-SPIRE 250-500 μm 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 ∼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 μm or 1.4 GHz using a cross-identification likelihood matching method. Individual source luminosities range from log (LIR/L) = 12.5-13.6 (corresponding to star formation rates (SFRs) 500-9000 M⊙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) × 10-3 M⊙yr-1 h 3 Mpc-3 at z ∼ 2.5, which is >10% of the estimated total SFRD of the universe from optical surveys. The contribution at z ∼ 4 has a lower limit of 3 × 10-3 M⊙yr-1 h 3 Mpc-3, ≳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. © 2012. The American Astronomical Society. All rights reserved..


The Herschel Multi-tiered Extragalactic Survey: SPIRE-mm photometric redshifts

Monthly Notices of the Royal Astronomical Society 419 (2012) 2758-2773

IG Roseboom, RJ Ivison, TR Greve, A Amblard, V Arumugam, R Auld, H Aussel, M Bethermin, A Blain, J Bock, A Boselli, D Brisbin, V Buat, D Burgarella, N Castro-Rodríguez, A Cava, P Chanial, E Chapin, S Chapman, DL Clements, A Conley, L Conversi, A Cooray, CD Dowell, JS Dunlop, E Dwek, S Eales, D Elbaz, D Farrah, A Franceschini, J Glenn, M Griffin, M Halpern, E Hatziminaoglou, E Ibar, K Isaak, G Lagache, L Levenson, N Lu, S Madden, B Maffei, G Mainetti, L Marchetti, G Marsden, G Morrison, AMJ Mortier, HT Nguyen, B O'Halloran, SJ Oliver, A Omont, MJ Page, P Panuzzo, A Papageorgiou, CP Pearson, I Pérez-Fournon, M Pohlen, JI Rawlings, G Raymond, D Rigopoulou, D Rizzo, G Rodighiero, M Rowan-Robinson, B Schulz, D Scott, N Seymour, DL Shupe, AJ Smith, JA Stevens, M Symeonidis, M Trichas, KE Tugwell, M Vaccari, I Valtchanov, JD Vieira, MP Viero, L Vigroux, J Wardlow, L Wang, G Wright, CK Xu, M Zemcov

We investigate the potential of submm-mm and submm-mm-radio photometric redshifts using a sample of mm-selected sources as seen at 250, 350 and 500μm by the SPIRE instrument on Herschel. From a sample of 63 previously identified mm sources with reliable radio identifications in the Great Observatories Origins Deep Survey North and Lockman Hole North fields, 46 (73per cent) are found to have detections in at least one SPIRE band. We explore the observed submm/mm colour evolution with redshift, finding that the colours of mm sources are adequately described by a modified blackbody with constant optical depth τ= (ν/nu 0 ) β , where β=+1.8 and ν 0 =c/100μm. We find a tight correlation between dust temperature and IR luminosity. Using a single model of the dust temperature and IR luminosity relation, we derive photometric redshift estimates for the 46 SPIRE-detected mm sources. Testing against the 22 sources with known spectroscopic or good quality optical/near-IR photometric redshifts, we find submm/mm photometric redshifts offer a redshift accuracy of |Δz|/(1 +z) = 0.16(〈|Δz|〉= 0.51). Including constraints from the radio-far-IR correlation, the accuracy is improved to |Δz|/(1 +z) = 0.15(〈|Δz|〉= 0.45). We estimate the redshift distribution of mm-selected sources finding a significant excess at z > 3 when compared to ∼ 850μm selected samples. © 2011 The Authors Monthly Notices of the Royal Astronomical Society © 2011 RAS.


The evolving interstellar medium of star-forming galaxies since z = 2 as probed by their infrared spectral energy distributions

Astrophysical Journal 760 (2012)

GE Magdis, E Daddi, M Béthermin, M Sargent, D Elbaz, M Pannella, M Dickinson, H Dannerbauer, E Da Cunha, F Walter, D Rigopoulou, V Charmandaris, HS Hwang, J Kartaltepe

Using data from the mid-infrared to millimeter wavelengths for individual galaxies and for stacked ensembles at 0.5 < z < 2, we derive robust estimates of dust masses (Mdust) for main-sequence (MS) galaxies, which obey a tight correlation between star formation rate (SFR) and stellar mass (M *), and for starbursting galaxies that fall outside that relation. Exploiting the correlation of gas-to-dust mass with metallicity (Mgas/M dust-Z), we use our measurements to constrain the gas content, CO-to-H2 conversion factors (αCO), and star formation efficiencies (SFE) of these distant galaxies. Using large statistical samples, we confirm that αCO and SFE are an order of magnitude higher and lower, respectively, in MS galaxies at high redshifts compared to the values of local galaxies with equivalently high infrared luminosities (LIR > 1012 L⊙). For galaxies within the MS, we show that the variations of specific star formation rates (sSFRs = SFR/M *) are driven by varying gas fractions. For relatively massive galaxies like those in our samples, we show that the hardness of the radiation field, 〈U〉, which is proportional to the dust-mass-weighted luminosity (L IR/Mdust) and the primary parameter defining the shape of the IR spectral energy distribution (SED), is equivalent to SFE/Z. For MS galaxies with stellar mass log (M */M⊙) ≥ 9.7 we measure this quantity, 〈U〉, showing that it does not depend significantly on either the stellar mass or the sSFR. This is explained as a simple consequence of the existing correlations between SFR-M *, M*-Z, and M gas-SFR. Instead, we show that 〈U〉 (or equally L IR/Mdust) does evolve, with MS galaxies having harder radiation fields and thus warmer temperatures as redshift increases from z = 0 to 2, a trend that can also be understood based on the redshift evolution of the M *-Z and SFR-M * relations. These results motivate the construction of a universal set of SED templates for MS galaxies that are independent of their sSFR or M * but vary as a function of redshift with only one parameter, 〈U〉. © 2012. The American Astronomical Society. All rights reserved.


Ultra steep spectrum radio sources in the Lockman Hole: SERVS identifications and redshift distribution at the faintest radio fluxes

Astrophysics and Space Science Proceedings (2012) 97-100

L Bizzocchi, J Afonso, E Ibar, M Grossi, C Simpson, S Chapman, MJ Jarvis, H Rottgering, RP Norris, J Dunlop, RJ Ivison, H Messias, J Pforr, M Vaccari, N Seymour, P Best, E Gonz, D Farrah, JS Huang, M Lacy, C Marastron, L Marchetti, JC Mauduit, S Oliver, D Rigopoulou, SA Stanford, J Surace, G Zeimann

Ultra Steep Spectrum (USS) radio sources have been successfully used to select powerful radio sources at high redshifts (z > 2). Typically restricted to large-sky surveys and relatively bright radio flux densities, it has gradually become possible to extend the USS search to sub-mJy levels, thanks to the recent appearance of sensitive low-frequency radio facilities. Here we present a first detailed analysis of the nature of the faintest USS sources. By using GMRT and VLA radio observations of the Lockman Hole (LH) at 610MHz and 1.4GHz, a sample of 58 micro-Jansky USS sources is assembled. Deep infrared data at 3.6 and 4.5μm from the Spitzer Extragalactic Representative Volume Survey (SERVS) is used to reliably identify counterparts for 48 (83%) of these sources, showing an average magnitude of [3.6]=19.7 mag(AB). Spectroscopic redshifts for 14 USS sources, together with photometric redshift estimates, improved by the use of the deep SERVS data, for a further 19 objects, show redshifts ranging from z =0.1 to z=2.8, peaking at z∼0.6 and tailing off at high redshifts. © Springer-Verlag Berlin Heidelberg 2012.


The suppression of star formation by powerful active galactic nuclei

Nature 485 (2012) 213-216

MJ Page, M Symeonidis, JD Vieira, B Altieri, A Amblard, V Arumugam, H Aussel, T Babbedge, A Blain, J Bock, A Boselli, V Buat, N Castro-Rodrñguez, A Cava, P Chanial, DL Clements, A Conley, L Conversi, A Cooray, CD Dowell, EN Dubois, JS Dunlop, E Dwek, S Dye, E Eales, D Elbaz, D Farrah, M Fox, A Franceschini, G Gear, J Glenn, M Griffin, M Halpern, E Hatziminaoglou, E Ibar, K Isaak, RJ Ivison, G Lagache, L Levenson, N Lu, S Madden, B Maffei, G Mainetti, L Marchetti, HT Nguyen, B O’halloran, SJ Oliver, A Omont, P Panuzzo, A Papageorgiou, CP Pearson, I Pérez-Fournon, M Pohlen, JI Rawlings, D Rigopoulou, L Riguccini, D Rizzo, G Rodighiero, IG Roseboom, M Rowan-Robinson, MS Portal, B Schulz, D Scott, N Seymour, DL Shupe, AJ Smith, JA Stevens, M Trichas, KE Tugwell, M Vaccari, I Valtchanov, M Viero, L Vigroux, L Wang, R Ward, G Wright, CK Xu, M Zemcov

The old, red stars that constitute the bulges of galaxies, and the massive black holes at their centres, are the relics of a period in cosmic history when galaxies formed stars at remarkable rates and active galactic nuclei (AGN) shone brightly as a result of accretion onto black holes. It is widely suspected, but unproved, that the tight correlation between the mass of the black hole and the mass of the stellar bulge results from the AGN quenching the surrounding star formation as it approaches its peak luminosity. X-rays trace emission from AGN unambiguously, whereas powerful star-forming galaxies are usually dust-obscured and are brightest at infrared and submillimetre wavelengths. Here we report submillimetre and X-ray observations that show that rapid star formation was common in the host galaxies of AGN when the Universe was 2-6 billion years old, but that the most vigorous star formation is not observed around black holes above an X-ray luminosity of 10 44 ergs per second. This suppression of star formation in the host galaxy of a powerful AGN is a key prediction of models in which the AGN drives an outflow, expelling the interstellar medium of its host and transforming the galaxy’s properties in a brief period of cosmic time. © 2012 Macmillan Publishers Limited.

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