N. Seymour

Publications (109)164.13 Total impact

• Article: The Herschel PEP/HerMES Luminosity Function. I: Probing the Evolution of PACS selected Galaxies to z~4

  C. Gruppioni, F. Pozzi, G. Rodighiero, I. Delvecchio, S. Berta, L. Pozzetti, G. Zamorani, P. Andreani, A. Cimatti, O. Ilbert, [......], M. Zemcov, S. Bardelli, M. Carollo, T. Contini, O. Le Fevre, S. Lilly, V. Mainieri, A. Renzini, M. Scodeggio, E. Zucca
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  ABSTRACT: We exploit the deep and extended far infrared data sets (at 70, 100 and 160 um) of the Herschel GTO PACS Evolutionary Probe (PEP) Survey, in combination with the HERschel Multi tiered Extragalactic Survey (HerMES) data at 250, 350 and 500 um, to derive the evolution of the restframe 35 um, 60 um, 90 um, and total infrared (IR) luminosity functions (LFs) up to z~4. We detect very strong luminosity evolution for the total IR LF combined with a density evolution. In agreement with previous findings, the IR luminosity density increases steeply to z~1, then flattens between z~1 and z~3 to decrease at z greater than 3. Galaxies with different SEDs, masses and sSFRs evolve in very different ways and this large and deep statistical sample is the first one allowing us to separately study the different evolutionary behaviours of the individual IR populations contributing to the IR luminosity density. Galaxies occupying the well established SFR/stellar mass main sequence (MS) are found to dominate both the total IR LF and luminosity density at all redshifts, with the contribution from off MS sources (0.6 dex above MS) being nearly constant (~20% of the total IR luminosity density) and showing no significant signs of increase with increasing z over the whole 0.8<z<2.2 range. Sources with mass in the 10< log(M/Msun) <11 range are found to dominate the total IR LF, with more massive galaxies prevailing at the bright end of the high-z LF. A two-fold evolutionary scheme for IR galaxies is envisaged: on the one hand, a starburst-dominated phase in which the SMBH grows and is obscured by dust, is followed by an AGN dominated phase, then evolving toward a local elliptical. On the other hand, moderately starforming galaxies containing a low-luminosity AGN have various properties suggesting they are good candidates for systems in a transition phase preceding the formation of steady spiral galaxies.
  02/2013;
• Article: The Herschel census of infrared SEDs through cosmic time

  Myrto Symeonidis, M. Vaccari, S. Berta, M. J. Page, D. Lutz, V. Arumugam, H. Aussel, J. Bock, A. Boselli, V. Buat, [......], B. Schulz, Douglas Scott, N. Seymour, D. L. Shupe, A. J. Smith, I. Valtchanov, L. Wang, C. K. Xu, M. Zemcov, S. Wuyts
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  ABSTRACT: Using Herschel data from the deepest SPIRE and PACS surveys (HerMES and PEP) in COSMOS and GOODS (N+S), we examine the dust properties of IR-luminous (L_IR>10^10 L_sun) galaxies at 0.1<z<2 and determine how these evolve with cosmic time. The unique angle of this work is the rigorous analysis of survey selection effects, making this the first study of the star-formation-dominated, IR-luminous population within a framework almost entirely free of selection biases. We find that IR-luminous galaxies have SEDs with broad far-IR peaks characterised by cool/extended dust emission and average dust temperatures in the 25-45K range. Hot (T>45K) SEDs and cold (T<25K), cirrus-dominated SEDs are rare, with most sources being within the range occupied by warm starbursts such as M82 and cool spirals such as M51. We observe a luminosity-temperature (L-T) relation, where the average dust temperature of log[L_IR/L_sun]=12.5 galaxies is about 10K higher than that of their log[L_IR/L_sun]=10.5 counterparts. However, although the increased dust heating in more luminous systems is the driving factor behind the L-T relation, the increase in dust mass and/or starburst size with luminosity plays a dominant role in shaping it. Our results show that the dust conditions in IR-luminous sources evolve with cosmic time: at high redshift, dust temperatures are on average up to 10K lower than what is measured locally. This is manifested as a flattening of the L-T relation, suggesting that (U)LIRGs in the early Universe are typically characterised by a more extended dust distribution and/or higher dust masses than local equivalent sources. Interestingly, the evolution in dust temperature is luminosity dependent, with the fraction of LIRGs with T<35K showing a 2-fold increase from z~0 to z~2, whereas that of ULIRGs with T<35K shows a 6-fold increase.
  02/2013;
• Article: Physical Conditions of the Gas in an ALMA [CII]-identified Submillimetre Galaxy at z = 4.44

  M. T. Huynh, R. P. Norris, K. E. K. Coppin, B. H. C. Emonts, R. J. Ivison, N. Seymour, Ian Smail, V. Smolcic, A. M. Swinbank, W. N. Brandt, [......], H. Dannerbauer, C. De Breuck, T. R. Greve, J. A. Hodge, A. Karim, K. K. Knudsen, K. M. Menten, P. P. van der Werf, F. Walter, A. Weiss
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  ABSTRACT: We present CO(2-1) observations of the submillimetre galaxy ALESS65.1 performed with the Australia Telescope Compact Array at 42.3 GHz. A previous ALMA study of submillimetre galaxies in the Extended Chandra Deep Field South detected [CII] 157.74 micron emission from this galaxy at a redshift of z = 4.44. No CO(2-1) emission was detected but we derive a firm upper limit to the cold gas mass in ALESS65.1 of M_gas < 1.7 x 10^10 M_odot. The estimated gas depletion timescale is <50 Myr, which is similar to other high redshift SMGs, and consistent with z > 4 SMGs being the likely progenitors of massive red-and-dead galaxies at z > 2. The ratio of the [CII], CO and far-infrared luminosities implies a strong far-ultraviolet field of G_0 > 10^3, as seen in Galactic star forming regions or local ULIRGs. The observed L_[CII]/L_FIR = 2.3 x 10^{-3} is high compared to local ULIRGs and, combined with L_[CII]/L_CO > 2700, it is consistent with ALESS65.1 either having an extended (several kpc) [CII] emitting region or lower than solar metallicity.
  02/2013;
• Article: CO(1-0) detection of molecular gas in the massive Spiderweb Galaxy (z=2)

  B. H. C. Emonts, I. Feain, H. J. A. Roettgering, G. Miley, N. Seymour, R. P. Norris, C. L. Carilli, M. Villar-Martin, M. Y. Mao, E. M. Sadler, R. D. Ekers, G. A. van Moorsel, R. J. Ivison, L. Pentericci, C. N. Tadhunter, D. J. Saikia
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  ABSTRACT: The high-redshift radio galaxy MRC 1138-262 (`Spiderweb Galaxy'; z = 2.16), is one of the most massive systems in the early Universe and surrounded by a dense `web' of proto-cluster galaxies. Using the Australia Telescope Compact Array, we detected CO(1-0) emission from cold molecular gas -- the raw ingredient for star formation -- across the Spiderweb Galaxy. We infer a molecular gas mass of M(H2) = 6x10^10 M(sun) (for M(H2)/L'(CO)=0.8). While the bulk of the molecular gas coincides with the central radio galaxy, there are indications that a substantial fraction of this gas is associated with satellite galaxies or spread across the inter-galactic medium on scales of tens of kpc. In addition, we tentatively detect CO(1-0) in the star-forming proto-cluster galaxy HAE 229, 250 kpc to the west. Our observations are consistent with the fact that the Spiderweb Galaxy is building up its stellar mass through a massive burst of widespread star formation. At maximum star formation efficiency, the molecular gas will be able to sustain the current star formation rate (SFR ~ 1400 M(sun)/yr, as traced by Seymour et al.) for about 40 Myr. This is similar to the estimated typical lifetime of a major starburst event in infra-red luminous merger systems.
  01/2013;
• Article: Radio Continuum Surveys with Square Kilometre Array Pathfinders

  Ray P. Norris, J. Afonso, D. Bacon, Rainer Beck, Martin Bell, R. J. Beswick, Philip Best, Sanjay Bhatnagar, Annalisa Bonafede, Gianfranco Brunetti, [......], H. Rottgering, Jose Sabater, Mara Salvato, Anna M. M. Scaife, Richard Schilizzi, N. Seymour, Dan J. B. Smith, Grazia Umana, G. -B. Zhao, Peter-Christian Zinn
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  ABSTRACT: In the lead-up to the Square Kilometre Array (SKA) project, several next-generation radio telescopes and upgrades are already being built around the world. These include APERTIF (The Netherlands), ASKAP (Australia), eMERLIN (UK), VLA (USA), e-EVN (based in Europe), LOFAR (The Netherlands), Meerkat (South Africa), and the Murchison Widefield Array (MWA). Each of these new instruments has different strengths, and coordination of surveys between them can help maximise the science from each of them. A radio continuum survey is being planned on each of them with the primary science objective of understanding the formation and evolution of galaxies over cosmic time, and the cosmological parameters and large-scale structures which drive it. In pursuit of this objective, the different teams are developing a variety of new techniques, and refining existing ones. Here we describe these projects, their science goals, and the technical challenges which are being addressed to maximise the science return.
  10/2012;
• Article: The Herschel view of the environment of the radio galaxy 4C+41.17 at z = 3.8

  D. Wylezalek, J. Vernet, C. De Breuck, D. Stern, A. Galametz, N. Seymour, M. Jarvis, P. Barthel, G. Drouart, T. R. Greve, M. Haas, N. Hatch, R. Ivison, M. Lehnert, K. Meisenheimer, G. Miley, N. Nesvadba, H. J. A. Röttgering, J. A. Stevens
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  ABSTRACT: We present Herschel observations at 70, 160, 250, 350 and 500 micron of the environment of the radio galaxy 4C+41.17 at z = 3.792. About 65% of the extracted sources are securely identified with mid-IR sources observed with the Spitzer Space Telescope at 3.6, 4.5, 5.8, 8 and 24 micron. We derive simple photometric redshifts, also including existing 850 micron and 1200 micron data, using templates of AGN, 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 SED of the closest (~ 25" 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 multi-wavelength data, in particular on the Rayleigh-Jeans side of the spectral energy distribution, allow us to confirm or rule out the presence of protocluster candidates that were previously selected by single wavelength data sets.
  10/2012;
• Article: A Redshift Survey of Herschel Far-Infrared Selected Starbursts and Implications for Obscured Star Formation

  C. M. Casey, S. Berta, M. Béthermin, J. Bock, C. Bridge, J. Budynkiewicz, D. Burgarella, E. Chapin, S. C. Chapman, D. L. Clements, [......], D. Rigopoulou, L. Riguccini, I. G. Roseboom, D. B. Sanders, D. Scott, N. Seymour, I. Valtchanov, J. D. Vieira, M. Viero, J. Wardlow
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  ABSTRACT: We present Keck spectroscopic observations and redshifts for a sample of 767 Herschel-SPIRE selected galaxies (HSGs) at 250, 350, and 500um, taken with the Keck I Low Resolution Imaging Spectrometer (LRIS) and the Keck II DEep Imaging Multi-Object Spectrograph (DEIMOS). The redshift distribution of these SPIRE sources from the Herschel Multitiered Extragalactic Survey (HerMES) 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 ( /(1+z)>=0.29) than is seen in non-infrared selected samples, likely due to enhanced star formation rates and dust obscuration in infrared-selected galaxies. We estimate that the vast majority (72-83%) of z<2 Herschel-selected galaxies would drop out of traditional submillimeter surveys at 0.85-1mm. 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 24um 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. [abridged]
  10/2012;
• Article: A Population of z>2 Far-Infrared Herschel-SPIRE selected Starbursts

  C. M. Casey, S. Berta, M. Béthermin, J. Bock, C. Bridge, D. Burgarella, E. Chapin, S. C. Chapman, D. L. Clements, A. Conley, [......], D. Rigopoulou, L. Riguccini, I. G. Roseboom, D. B. Sanders, D. Scott, N. Seymour, I. Valtchanov, J. D. Vieira, M. Viero, J. Wardlow
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  ABSTRACT: We present spectroscopic observations for a sample of 36 Herschel-SPIRE 250-500um selected galaxies (HSGs) at 2<z<5 from the Herschel Multi-tiered Extragalactic Survey (HerMES). Redshifts are confirmed as part of a large redshift survey of Herschel-SPIRE-selected sources covering ~0.93deg^2 in six extragalactic legacy fields. Observations were taken with the Keck I Low Resolution Imaging Spectrometer (LRIS) and the Keck II DEep Imaging Multi-Object Spectrograph (DEIMOS). Precise astrometry, needed for spectroscopic follow-up, is determined by identification of counterparts at 24um or 1.4GHz using a cross-identification likelihood matching method. Individual source luminosities range from log(L_IR/Lsun)=12.5-13.6 (corresponding to star formation rates 500-9000Msun/yr, assuming a Salpeter IMF), constituting some of the most intrinsically luminous, distant infrared galaxies yet discovered. We present both individual and composite rest-frame ultraviolet spectra and infrared spectral energy distributions (SEDs). The selection of these HSGs is reproducible and well characterized across large areas of 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 at (7+-2)x10^(-3)Msun/yr h^3Mpc^(-3) at z~2.5, which is >10% of the estimated total star formation rate density (SFRD) of the Universe from optical surveys. The contribution at z~4 has a lower limit of 3x10^(-3)Msun/yr h^3 Mpc^(-3), ~>20% of the estimated total SFRD. This highlights the importance of extremely infrared-luminous galaxies with high star formation rates to the build-up of stellar mass, even at the earliest epochs.
  10/2012;
• Article: The Spitzer Extragalactic Representative Volume Survey (SERVS): Survey Definition and Goals (PASP, 124, 714, [2012])

  J -C Mauduit, M Lacy, D Farrah, J ~A Surace, M Jarvis, S Oliver, C Maraston, M Vaccari, L Marchetti, G Zeimann, [......], C ~J Simpson, I Smail, G ~K Squires, J ~A Stevens, R Taylor, M Trichas, T Urrutia, E Kampen, A Verma, C ~K Xu
  pasp. 10/2012; 124:1135-1136.
• Article: Gas-rich mergers and feedback are ubiquitous amongst starbursting radio galaxies, as revealed by the VLA, IRAM PdBI and Herschel

  R ~J Ivison, I Smail, A Amblard, V Arumugam, C De Breuck, B ~H ~C Emonts, I Feain, T ~R Greve, M Haas, E Ibar, M ~J Jarvis, A Kovács, M ~D Lehnert, N ~P ~H Nesvadba, H ~J ~A Röttgering, N Seymour, D Wylezalek
  mnras. 09/2012; 425:1320-1331.
• Article: HerMES: Cosmic Infrared Background Anisotropies and the Clustering of Dusty Star-Forming Galaxies

  M. P. Viero, L. Wang, M. Zemcov, G. Addison, A. Amblard, V. Arumugam, H. Aussel, M. Bethermin, J. Bock, A. Boselli, [......], N. Seymour, B. Schulz, D. L. Shupe, A. J. Smith, M. Symeonidis, M. Vaccari, I. Valtchanov, J. D. Vieira, J. Wardlow, C. K. Xu
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  ABSTRACT: We present measurements of the auto- and cross-frequency power spectra of the cosmic infrared background (CIB) at 250, 350, and 500um (1200, 860, and 600 GHz) from observations totaling ~ 70 deg^2 made with the SPIRE instrument aboard the Herschel Space Observatory. We measure a fractional anisotropy dI / I = 14 +- 4%, detecting signatures arising from the clustering of dusty star-forming galaxies in both the linear (2-halo) and non-linear (1-halo) regimes to unprecedented levels; 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 ~ 0.1 arcmin^-1 (l ~ 2200). 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. 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 using a novel alternative to the standard halo model. With the aim of fitting simultaneously with one model the power spectra and number counts 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 towards 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 ~ 1-3, is log(M_peak/M_sun) ~ 12.1 +- 0.5, and that the minimum halo mass to host infrared galaxies is log(M_min/M_sun) ~ 9.9 +- 0.5.
  08/2012;
• Article: Herschel-ATLAS: Multi-wavelength SEDs and physical properties of 250 micron-selected galaxies at z < 0.5

  D. J. B. Smith, L. Dunne, E. da Cunha, K. Rowlands, S. J. Maddox, H. L. Gomez, D. G. Bonfield, S. Charlot, S. P. Driver, C. C. Popescu, [......], R. Hopwood, E. Ibar, R. J. Ivison, L. Kelvin, B. F. Madore, M. Pohlen, E. E. Rigby, A. Robotham, M. Seibert, P. Temi
  [show abstract] [hide abstract]
  ABSTRACT: We present a pan-chromatic analysis of an unprecedented sample of 1402 250 micron-selected galaxies at z < 0.5 (mean z = 0.24) from the Herschel-ATLAS survey. We complement our Herschel 100-500 micron data with UV-K-band photometry from the Galaxy And Mass Assembly (GAMA) survey and apply the MAGPHYS energy-balance technique to produce pan-chromatic SEDs for a representative sample of 250 micron selected galaxies spanning the most recent 5 Gyr of cosmic history. We derive estimates of physical parameters, including star formation rates, stellar masses, dust masses and infrared luminosities. The typical H-ATLAS galaxy at z < 0.5 has a far-infrared luminosity in the range 10^10 - 10^12 Lsolar (SFR: 1-50 Msolar/yr) thus is broadly representative of normal star forming galaxies over this redshift range. We show that 250 micron-selected galaxies contain a larger mass of dust at a given infra-red luminosity or star formation rate than previous samples selected at 60 micron from IRAS. We derive typical SEDs for H-ATLAS galaxies, and show that the emergent SED shape is most sensitive to specific star formation rate. The optical-UV SEDs also become more reddened due to dust at higher redshifts. Our template SEDs are significantly cooler than existing infra-red templates. They may therefore be most appropriate for inferring total IR luminosities from moderate redshift submillimetre selected samples and for inclusion in models of the lower redshift submillimetre galaxy populations.
  08/2012;
• Article: CI, [CII] and CO observations towards TNJ 1338-1942: Probing the ISM in a massive proto-cluster galaxy at z = 4.11

  S König, T ~R Greve, N Seymour, J ~I Rawlings, P Papadopoulos, R ~J Ivison, C De Breuck, J Stevens, I Smail, A Kovacs
  Journal of Physics Conference Series 07/2012; 372(1):012064.
• Article: Rapid Coeval Black Hole and Host Galaxy Growth in MRC 1138-262: The Hungry Spider

  N. Seymour, B. Altieri, C. De Breuck, P. Barthel, D. Coia, L. Conversi, H. Dannerbauer, A. Dey, M. Dickinson, G. Drouart, [......], A. Rettura, H. Rottgering, B. Rocca-Volmerange, M. Sanchez-Portal, J. S. Santos, D. Stern, J. Stevens, I. Valtchanov, J. Vernet, D. Wylezalek
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  ABSTRACT: We present a detailed study of the infrared spectral energy distribution of the high-redshift radio galaxy MRC 1138-26 at z = 2.156, also known as the Spiderweb Galaxy. By combining photometry from Spitzer, Herschel and LABOCA we fit the rest-frame 5-300 um emission using a two component, starburst and active galactic nucleus (AGN), model. The total infrared (8 - 1000 um) luminosity of this galaxy is (1.97+/-0.28)x10^13 Lsun with (1.17+/-0.27) and (0.79+/-0.09)x10^13 Lsun due to the AGN and starburst components respectively. The high derived AGN accretion rate of \sim20% Eddington, and the measured star formation rate (SFR) of 1390pm150 Msun/yr, suggest that this massive system is in a special phase of rapid central black hole and host galaxy growth, likely caused by a gas rich merger in a dense environment. The accretion rate is sufficient to power both the jets and the previously observed large outflow. The high SFR and strong outflow suggest this galaxy could potentially exhaust its fuel for stellar growth in a few tens of Myr, although the likely merger of the radio galaxy with nearby satellites suggest bursts of star formation may recur again on time scales of several hundreds of Myr. The age of the radio lobes implies the jet started after the current burst of star formation, and therefore we are possibly witnessing the transition from a merger-induced starburst phase to a radio-loud AGN phase. We also note tentative evidence for [CII]158um emission. This paper marks the first results from the Herschel Galaxy Evolution Project (Project HeRGE), a systematic study of the evolutionary state of 71 high redshift, 1 < z < 5.2, radio galaxies.
  06/2012;
• Article: Gas-rich mergers and feedback are ubiqitous amongst starbursting radio galaxies, as revealed by JVLA, IRAM PdBI and Herschel

  R. J. Ivison, Ian Smail, A. Amblard, V. Arumugam, C. De Breuck, B. H. C. Emonts, I. Feain, T. R. Greve, M. Haas, E. Ibar, M. J. Jarvis, A. Kovaks, M. D. Lehnert, N. P. H. Nesvadba, H. J. A. Rottgering, N. Seymour, D. Wylezalek
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  ABSTRACT: We report new, sensitive observations of two z ~ 3-3.5 FIR-luminous radio galaxies, 6C1909+72 and B3J2330+3927, in 12CO J=1-0 with the Karl Jansky VLA and at 100-500um using Herschel, alongside new and archival 12CO J=4-3 observations from IRAM PdBI. We introduce a new colour-colour diagnostic plot to constrain the redshifts of several distant, dusty galaxies in our target fields. A bright SMG near 6C1909+72 likely shares the same node or filament as the signpost AGN, but it is not detected in CO despite ~20,000 km/s of velocity coverage. Also in the 6C1909+72 field, a large, red dust feature spanning ~500 kpc is aligned with the radio jet. We suggest several processes by which metal-rich material may have been transported, favouring a collimated outflow reminiscent of the jet-oriented metal enrichment seen in local cluster environments. Our interferometric imaging reveals a gas-rich companion to B3J2330+3927; indeed, all bar one of the eight z >~ 2 radio galaxies (or companions) detected in CO provide some evidence that starburst activity in radio-loud AGN at high redshift is driven by the interaction of two or more gas-rich systems in which a significant mass of stars has already formed, rather than via steady accretion of cold gas from the cosmic web. We find that the CO Tb ratios in radio-loud AGN host galaxies are significantly higher than those seen in similarly intense starbursts where AGN activity is less pronounced. Our most extreme example, where L'(CO4-3)/L'(CO1-0) > 2.7, provides evidence that significant energy is being deposited rapidly into the molecular gas via X-rays and/or mechanical (`quasar-mode') feedback from the AGN, leading to a high degree of turbulence globally and a low optical depth in 12CO - feedback that may lead to the cessation of star formation on a timescale commensurate with that of the jet activity, <~10 Myr.
  06/2012;
• Article: The Spitzer Extragalactic Representative Volume Survey (SERVS): survey definition and goals

  J. -C. Mauduit, M. Lacy, D. Farrah, J. A. Surace, M. Jarvis, S. Oliver, C. Maraston, M. Vaccari, L. Marchetti, G. Zeimann, [......], C. J. Simpson, I. Smail, G. K. Squires, J. A. Stevens, R. Taylor, M. Trichas, T. Urrutia, E. van Kampen, A. Verma, C. K. Xu
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  ABSTRACT: We present the Spitzer Extragalactic Representative Volume Survey (SERVS), an 18 square degrees medium-deep survey at 3.6 and 4.5 microns with the post-cryogenic Spitzer Space Telescope to ~2 microJy (AB=23.1) depth of five highly observed astronomical fields (ELAIS-N1, ELAIS-S1, Lockman Hole, Chandra Deep Field South and XMM-LSS). SERVS is designed to enable the study of galaxy evolution as a function of environment from z~5 to the present day, and is the first extragalactic survey both large enough and deep enough to put rare objects such as luminous quasars and galaxy clusters at z>1 into their cosmological context. SERVS is designed to overlap with several key surveys at optical, near- through far-infrared, submillimeter and radio wavelengths to provide an unprecedented view of the formation and evolution of massive galaxies. In this paper, we discuss the SERVS survey design, the data processing flow from image reduction and mosaicing to catalogs, as well as coverage of ancillary data from other surveys in the SERVS fields. We also highlight a variety of early science results from the survey.
  06/2012;
• Article: HerMES: Candidate Gravitationally Lensed Galaxies and Lensing Statistics at Submillimeter Wavelengths

  Julie L. Wardlow, Asantha Cooray, Francesco De Bernardis, A. Amblard, V. Arumugam, H. Aussel, A. J. Baker, M. Béthermin, R. Blundell, J. Bock, [......], A. Strom, M. Symeonidis, M. Trichas, M. Vaccari, J. D. Vieira, M. Viero, L. Wang, C. K. Xu, L. Yan, M. Zemcov
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  ABSTRACT: We present a list of 13 candidate gravitationally lensed submillimeter galaxies (SMGs) from 95 square degrees of the Herschel Multi-tiered Extragalactic Survey, a surface density of 0.14\pm0.04deg^{-2}. The selected sources have 500um flux densities (S_500) greater than 100mJy. 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\pm0.06deg^{-2}) gravitationally lensed SMG candidates with S_500=80--100mJy, 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>100mJy 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=100mJy are magnified by factors of ~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 500micron flux densities less than 30mJy. Thus, samples of strongly gravitationally lensed SMGs, such as those presented here, probe below the nominal Herschel detection limit at 500 micron. 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 ~0.01" in the source plane.
  05/2012;
• Article: Ultraluminous Star-Forming Galaxies and Extremely Luminous Warm Molecular Hydrogen Emission at z=2.16 in the PKS 1138-26 Radio Galaxy Protocluster

  P. Ogle, J. E. Davies, P. N. Appleton, B. Bertincourt, N. Seymour, G. Helou
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  ABSTRACT: A deep Spitzer Infrared Spectrograph map of the PKS 1138-26 galaxy protocluster reveals ultraluminous PAH emission from obscured star formation in three protocluster galaxies, including Halpha-emitter (HAE) 229, HAE 131, and the central Spiderweb Galaxy. Star formation rates of 500-1100 Msun/yr are estimated from the 7.7 micron PAH feature. At such prodigious formation rates, the galaxy stellar masses will double in 0.6-1.1 Gyr. We are viewing the peak epoch of star formation for these protocluster galaxies. However, it appears that extinction of Halpha is much greater (factor of 40) in the two ULIRG HAEs compared to the Spiderweb. This may be attributed to different spatial distributions of star formation--nuclear star formation in the HAEs versus extended star formation in accreting satellite galaxies in the Spiderweb. We find extremely luminous mid-IR rotational line emission from warm molecular hydrogen in the Spiderweb Galaxy, with L(H2 0-0 S(3))= 1.4E44 erg/s (3.7E10 Lsun), 20 times more luminous than any previously known H2 emission galaxy (MOHEG). Depending on temperature, this corresponds to a very large mass of >9E6-2E9 Msun of T>300 K molecular gas, heated by the PKS 1138-26 radio jet, acting to quench nuclear star formation. There is >8 times more warm H2 at these temperatures in the Spiderweb than what has been seen in low-redshift (z<0.2) radio galaxies, indicating that the Spiderweb may have a larger reservoir of molecular gas than more evolved radio galaxies. This is the highest redshift galaxy yet in which warm molecular hydrogen has been directly detected.
  03/2012;
• Article: The Herschel Multi-tiered Extragalactic Survey: HerMES

  HerMES Collaboration, S. J. Oliver, J. Bock, B. Altieri, A. Amblard, V. Arumugam, H. Aussel, T. Babbedge, A. Beelen, M. Béthermin, [......], I. Valtchanov, J. D. Vieira, M. Viero, L. Vigroux, L. Wang, R. Ward, J. Wardlow, G. Wright, C. K. Xu, M. Zemcov
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  ABSTRACT: The Herschel Multi-tiered Extragalactic Survey, HerMES, is a legacy program designed to map a set of nested fields totalling ~380 deg^2. Fields range in size from 0.01 to ~20 deg^2, using Herschel-SPIRE (at 250, 350 and 500 \mu m), and Herschel-PACS (at 100 and 160 \mu m), with an additional wider component of 270 deg^2 with SPIRE alone. These bands cover the peak of the redshifted thermal spectral energy distribution from interstellar dust and thus capture the re-processed optical and ultra-violet radiation from star formation that has been absorbed by dust, and are critical for forming a complete multi-wavelength understanding of galaxy formation and evolution. The survey will detect of order 100,000 galaxies at 5\sigma 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.
  03/2012;
• Article: HerMES: deep number counts at 250, 350, and 500 microns in the COSMOS and GOODS-N fields and the build-up of the cosmic infrared background

  M. Béthermin, E. Le Floc'h, O. Ilbert, A. Conley, G. Lagache, A. Amblard, V. Arumugam, H. Aussel, S. Berta, J. Bock, [......], M. Symeonidis, M. Trichas, K. E. Tugwell, M. Vaccari, I. Valtchanov, J. D. Vieira, M. Viero, L. Wang, C. K. Xu, M. Zemcov
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  ABSTRACT: ABRIGED Herschel/SPIRE has provided confusion limited maps of deep fields at 250, 350, and 500um, as part of the HerMES survey. Due to confusion, only a small fraction of the Cosmic Infrared Background can be resolved into individually-detected sources. Our goal is to produce deep galaxy number counts and redshift distributions below the confusion limit, which we then use to place strong constraints on the origins of the cosmic infrared background and on models of galaxy evolution. We individually extracted the bright SPIRE with a method using the positions, the flux densities, and the redshifts of the 24um sources as a prior, and derived the number counts and redshift distributions of the bright SPIRE sources. For fainter SPIRE sources, we reconstructed the number counts and the redshift distribution below the confusion limit using the deep 24um catalogs associated with photometric redshift and information provided by the stacking of these sources into the deep SPIRE maps. 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. 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 5sigma confusion limit. None of the pre-existing population models are able to reproduce our results at better than 3sigma. 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, 6.5, and 2.8 nW/m2/sr at 250, 350, and 500um, respectively. These values agree well with FIRAS absolute measurements, suggesting our number counts and their extrapolation are sufficient to explain the CIB. Finally, combining our results with other works, we estimate the energy budget contained in the CIB between 8 and 1000um: 26 nW/m2/sr.
  03/2012;