Publications by Dimitra Rigopoulou


Herschel observations and a model for IRAS 08572+3915: A candidate for the most luminous infrared galaxy in the local (z < 0.2) Universe

Monthly Notices of the Royal Astronomical Society: Letters 437 (2013)

A Efstathiou, C Pearson, D Farrah, D Rigopoulou, J Gracía-Carpio, A Verma, HWW Spoon, J Afonso, J Bernard-Salas, DL Clements, A Cooray, D Cormier, M Etxaluze, J Fischer, E Gonźalez-Alfonso, P Hurley, V Lebouteiller, SJ Oliver, M Rowan-Robinson, E Sturm

We present Herschel photometry and spectroscopy, carried out as part of the Herschel ultraluminous infrared galaxy (ULIRG) survey, and a model for the infrared to submillimetre emission of the ULIRG IRAS 08572+3915. This source shows one of the deepest known silicate absorption features and no polycyclic aromatic hydrocarbon emission. The model suggests that this object is powered by an active galactic nucleus (AGN) with a fairly smooth torus viewed almost edge-on and a very young starburst. According to our model, the AGN contributes about 90 per cent of the total luminosity of 1.1 × 1013 L⊙, which is about a factor of 5 higher than previous estimates. The large correction of the luminosity is due to theanisotropy of the emission of the best-fitting torus. Similar corrections may be necessary for other local and high-z analogues. This correction implies that IRAS 08572+3915 at a redshift of 0.058 35 may be the nearest hyperluminous infrared galaxy and probably the most luminous infrared galaxy in the local (z < 0.2) Universe. IRAS 08572+3915 shows a low ratio of [C II] to IR luminosity (log L[C II]/LIR < -3.8) and a [OI]63 μm to [CII]158 μm line ratio of about 1 that supports the model presented in this Letter ©2013 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society.


Hermes: Dust attenuation and star formation activity in ultraviolet-selected samples from z ~ 4 to ~1.5

Monthly Notices of the Royal Astronomical Society 437 (2013) 1268-1283

S Heinis, V Buat, M Béthermin, J Bock, D Burgarella, A Conley, A Cooray, D Farrah, O Ilbert, G Magdis, G Marsden, SJ Oliver, D Rigopoulou, Y Roehlly, B Schulz, M Symeonidis, M Viero, CK Xu, M Zemcov

We study the link between observed ultraviolet (UV) luminosity, stellar mass and dust attenuation within rest-frame UV-selected samples at z ~ 4, ~ 3 and ~1.5.We measure by stacking at 250, 350 and 500 μm in the Herschel/Spectral and Photometric Imaging Receiver images from the Herschel Multi-Tiered Extragalactic Survey (HerMES) program the average infrared luminosity as a function of stellar mass and UV luminosity. We find that dust attenuation is mostly correlated with stellarmass. There is also a secondary dependence with UV luminosity: at a given UV luminosity, dust attenuation increases with stellar mass, while at a given stellar mass it decreases with UV luminosity. We provide new empirical recipes to correct for dust attenuation given the observed UV luminosity and the stellar mass. Our results also enable us to put new constraints on the average relation between star formation rate (SFR) and stellar mass at z ~ 4, ~3 and ~1.5. The SFR-stellar mass relations are well described by power laws (SFR α M 0.7* ), with the amplitudes being similar at z ~ 4 and ~3, and decreasing by a factor of 4 at z ~ 1.5 at a given stellar mass. We further investigate the evolution with redshift of the specific SFR. Our results are in the upper range of previous measurements, in particular at z ~ 3, and are consistent with a plateau at 3 < z < 4. Current model predictions (either analytic, semi-analytic or hydrodynamic) are inconsistent with these values, as they yield lower predictions than the observations in the redshift range we explore. We use these results to discuss the star formation histories of galaxies in the framework of the main sequence of star-forming galaxies. Our results suggest that galaxies at high redshift (2.5 < z < 4) stay around 1 Gyr on the main sequence. With decreasing redshift, this time increases such that z = 1 main-sequence galaxies with 10 8 M * M⊙ 10 10 stay on the main sequence until z = 0. © 2013 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society.


The SCUBA-2 cosmology legacy survey: Blank-Field number counts of 450-μm-selected galaxies and their contribution to the cosmic infrared background

Monthly Notices of the Royal Astronomical Society 432 (2013) 53-61

JE Geach, EL Chapin, KEK Coppin, JS Dunlop, M Halpern, I Smail, P van der Werf, S Serjeant, D Farrah, I Roseboom, T Targett, V Arumugam, V Asboth, A Blain, A Chrysostomou, C Clarke, RJ Ivison, SL Jones, A Karim, T Mackenzie, R Meijerink, MJ Michałowski, D Scott, JM Simpson, AM Swinbank, DM Alexander, O Almaini, I Aretxaga, P Best, S Chapman, DL Clements, C Conselice, ALR Danielson, S Eales, AC Edge, AG Gibb, D Hughes, T Jenness, KK Knudsen, CG Lacey, G Marsden, R McMahon, SJ Oliver, MJ Page, JA Peacock, D Rigopoulou, EI Robson, M Spaans, J Stevens, TMA Webb, C Willott, CD Wilson, M Zemcov

The first deep blank-field 450 μm map (1σ ≈ 1.3 mJy) from the Submillimetre Common- User Bolometer Array-2 SCUBA-2 Cosmology Legacy Survey (S2CLS), conducted with the James Clerk Maxwell Telescope (JCMT) is presented. Our map covers 140 arcmin2 of the Cosmological Evolution Survey field, in the footprint of the Hubble Space Telescope (HST) Cosmic Assembly Near-Infrared Deep Extragalactic Legacy Survey. Using 60 submillimetre galaxies detected at ≥3.75σ, we evaluate the number counts of 450-μm-selected galaxies with flux densities S450 > 5 mJy. The 8 arcsec JCMT beam and high sensitivity of SCUBA-2 now make it possible to directly resolve a larger fraction of the cosmic infrared background (CIB, peaking at λ ~ 200 μm) into the individual galaxies responsible for its emission than has previously been possible at this wavelength. At S450 > 5 mJy, we resolve (7.4 ± 0.7) x 10-2 MJy sr-1 of the CIB at 450 μm (equivalent to 16 ± 7 per cent of the absolute brightness measured by the Cosmic Background Explorer at this wavelength) into point sources. A further ~40 per cent of the CIB can be recovered through a statistical stack of 24 μm emitters in this field, indicating that the majority (≈60 per cent) of the CIB at 450 μm is emitted by galaxies with S450 > 2 mJy. The average redshift of 450 μm emitters identified with an optical/near-infrared counterpart is estimated to be 〈z〉 = 1.3, implying that the galaxies in the sample are in the ultraluminous class (LIR ≈ 1.1 x 1012 L⊙). If the galaxies contributing to the statistical stack lie at similar redshifts, then the majority of the CIB at 450 μm is emitted by galaxies in the luminous infrared galaxy (LIRG) class with LIR > 3.6 x 1011 L⊙. © 2013 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society.


Mid to far-infrared properties of star-forming galaxies and active galactic nuclei

Astronomy and Astrophysics 558 (2013)

GE Magdis, D Rigopoulou, G Helou, D Farrah, P Hurley, A Alonso-Herrero, J Bock, D Burgarella, S Chapman, V Charmandaris, A Cooray, Y Sophia Dai, D Dale, D Elbaz, A Feltre, E Hatziminaoglou, JS Huang, G Morrison, S Oliver, M Page, D Scott, Y Shi

We study the mid- to far-IR properties of a 24 ?m-selected flux-limited sample (S 24 5mJy) of 154 intermediate redshift (z ? 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 (LIR) and dust mass (Mdust) estimates and infered the relative contribution of the AGN to the infrared energy budget of the sources. We found that the total (8?1000 ?m) infrared emission of galaxies with weak 6.2 ?m PAH emission (EW6.2 ? 0.2 ?m) is dominated by AGN activity, while for galaxies with EW6.2 0.2 ?m more than 50% of the LIR arises from star formation. We also found that for galaxies detected in the 250-500 ?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 LIR-to-rest-frame 8 ?m luminosity ratio, IR8 ? LIR/L8 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 ?m mid-IR continuum emission. Using the [Ne iii]/[Ne ii] 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 (LIR/Mdust), the latter being a proxy for the dust temperature (Td). 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 LIR, based on single-band observations with the mid-infrared instrument, on board the upcoming James Webb Space Telescope. © ESO 2013.


Local luminous infrared galaxies. III. co-evolution of black hole growth and star formation activity?

Astrophysical Journal 765 (2013)

A Alonso-Herrero, M Pereira-Santaella, GH Rieke, AM Diamond-Stanic, Y Wang, A Hernán-Caballero, D Rigopoulou

Local luminous infrared (IR) galaxies (LIRGs) have both high star formation rates (SFR) and a high AGN (Seyfert and AGN/starburst composite) incidence. Therefore, they are ideal candidates to explore the co-evolution of black hole (BH) growth and star formation (SF) activity, not necessarily associated with major mergers. Here, we use Spitzer/IRS spectroscopy of a complete volume-limited sample of local LIRGs (distances of <78 Mpc). We estimate typical BH masses of 3 × 107 M using [Ne III] 15.56 μm and optical [O III] λ5007 gas velocity dispersions and literature stellar velocity dispersions. We find that in a large fraction of local LIRGs, the current SFR is taking place not only in the inner nuclear ∼1.5 kpc region, as estimated from the nuclear 11.3 μm PAH luminosities, but also in the host galaxy. We next use the ratios between the SFRs and BH accretion rates (BHAR) to study whether the SF activity and BH growth are contemporaneous in local LIRGs. On average, local LIRGs have SFR to BHAR ratios higher than those of optically selected Seyferts of similar active galactic nucleus (AGN) luminosities. However, the majority of the IR-bright galaxies in the revised-Shapley-Ames Seyfert sample behave like local LIRGs. Moreover, the AGN incidence tends to be higher in local LIRGs with the lowest SFRs. All of this suggests that in local LIRGs there is a distinct IR-bright star-forming phase taking place prior to the bulk of the current BH growth (i.e., AGN phase). The latter is reflected first as a composite and then as a Seyfert, and later as a non-LIRG optically identified Seyfert nucleus with moderate SF in its host galaxy. © 2013. The American Astronomical Society. All rights reserved.


Diagnostics of agn-driven molecular outflows in ulirgs from herschel-pacs observations of oh at 119 μm

Astrophysical Journal 775 (2013)

HWW Spoon, D Farrah, V Lebouteiller, E González-Alfonso, J Bernard-Salas, T Urrutia, D Rigopoulou, MS Westmoquette, HA Smith, J Afonso, C Pearson, D Cormier, A Efstathiou, C Borys, A Verma, M Etxaluze, DL Clements

We report on our observations of the 79 and 119 μm 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 μm 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 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) × 108 M. © 2013. The American Astronomical Society. All rights reserved..


The roles of star formation and AGN activity of IRS sources in the HerMES fields

Monthly Notices of the Royal Astronomical Society 434 (2013) 2426-2437

A Feltre, E Hatziminaoglou, A Hernán-Caballero, J Fritz, A Franceschini, J Bock, A Cooray, D Farrah, EA González Solares, E Ibar, KG Isaak, BL Faro, L Marchetti, SJ Oliver, MJ Page, D Rigopoulou, IG Roseboom, M Symeonidis, M Vaccari

In this work, we explore the impact of the presence of an active galactic nucleus (AGN) on the mid- and far-infrared (IR) properties of galaxies as well as the effects of simultaneous AGN and starburst activity in the same galaxies. To do this, we apply a multicomponent, multiband spectral synthesis technique to a sample of 250 μm selected galaxies of the Herschel Multitiered Extragalactic Survey (HerMES), with Infrared Spectrograph (IRS) spectra available for all galaxies. Our results confirm that the inclusion of the IRS spectra plays a crucial role in the spectral analysis of galaxies with an AGN component improving the selection of the best-fitting hot dust (torus) model. We find a correlation between the obscured star formation rate, SFRIR, derived from the IR luminosity of the starburst component, and SFRPAH, derived from the luminosity of the PAH features, LPAH, with SFRFIR taking higher values than SFRPAH. The correlation is different for AGN- and starburst-dominated objects. The ratio of LPAH to that of the starburst component, LPAH/LSB, is almost constant for AGN-dominated objects but decreases with increasing LSB for starburst-dominated objects. SFRFIR increases with the accretion luminosity, Lacc, with the increase less prominent for the very brightest, unobscured AGN-dominated sources. We find no correlation between the masses of the hot (AGN-heated) and cold (starburstheated) dust components. We interpret this as a non-constant fraction of gas driven by the gravitational effects to the AGN while the starburst is ongoing. We also find no evidenceof the AGN affecting the temperature of the cold dust component, though this conclusion is mostly based on objects with a non-dominant AGN component. We conclude that our findings do not provide evidence that the presence of AGN affects the star formation process in the host galaxy, but rather that the two phenomena occur simultaneously over a wide range of luminosities. © 2013 The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society.


Far-infrared fine-structure line diagnostics of ultraluminous infrared galaxies

Astrophysical Journal 776 (2013)

D Farrah, V Lebouteiller, HWW Spoon, J Bernard-Salas, C Pearson, D Rigopoulou, HA Smith, E González-Alfonso, DL Clements, A Efstathiou, D Cormier, J Afonso, SM Petty, K Harris, P Hurley, C Borys, A Verma, A Cooray, V Salvatelli

We present Herschel observations of 6 fine-structure lines in 25 ultraluminous infrared galaxies at z < 0.27. The lines, [O III]52 μm, [N III]57 μm, [O I]63 μm, [N II]122 μm, [O I]145 μm, and [C II]158 μm, are mostly single Gaussians with widths <600 km s -1 and luminosities of 10 7 -10 9 L O . 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. © 2013. The American Astronomical Society. All rights reserved.


HerMES: Cosmic infrared background anisotropies and the clustering of dusty star-forming galaxies

Astrophysical Journal 772 (2013)

MP Viero, L Wang, M Zemcov, G Addison, A Amblard, V Arumugam, H Aussel, M Béthermin, J Bock, A Boselli, V Buat, D Burgarella, CM Casey, DL Clements, A Conley, L Conversi, A Cooray, G De Zotti, CD Dowell, D Farrah, A Franceschini, J Glenn, M Griffin, E Hatziminaoglou, S Heinis, E Ibar, RJ Ivison, G Lagache, L Levenson, L Marchetti, G Marsden, HT Nguyen, B O'Halloran, SJ Oliver, A Omont, MJ Page, A Papageorgiou, CP Pearson, I Pérez-Fournon, M Pohlen, D Rigopoulou, IG Roseboom, M Rowan-Robinson, B Schulz, D Scott, N Seymour, DL Shupe, AJ Smith, M Symeonidis, M Vaccari, I Valtchanov, JD Vieira, J Wardlow, CK Xu

We present measurements of the auto- and cross-frequency power spectra of the cosmic infrared background (CIB) at 250, 350, and 500 μm (1200, 860, and 600 GHz) from observations totaling 70 deg2 made with the SPIRE instrument aboard the Herschel Space Observatory. We measure a fractional anisotropy δI/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 θ 0.10-0.12 arcmin-1 (ℓ 2160-2380), from 250 to 500 μm. 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 1-3, is log(Mpeak/M ⊙) 12.1 ± 0.5, and that the minimum halo mass to host infrared galaxies is log(M⊙min/M⊙) 10.1 ± 0.6. © 2013. The American Astronomical Society. All rights reserved.


Multi-wavelength study of a complete IRAC 3.6 μm selected galaxy sample: A fair census of red and blue populations at redshifts 0.4-1.2

Astrophysical Journal 766 (2013)

JS Huang, SM Faber, CNA Willmer, D Rigopoulou, D Koo, J Newman, C Shu, MLN Ashby, P Barmby, A Coil, Z Luo, G Magdis, T Wang, B Weiner, SP Willner, XZ Zheng, GG Fazio

We present a multi-wavelength study of a 3.6 μm selected galaxy sample in the Extended Groth Strip (EGS). The sample is complete for galaxies with stellar mass >109.5 Mȯ and redshift 0.4 < z < 1.2. In this redshift range, the Infrared Array Camera 3.6 μm band measures the rest-frame near-infrared band, permitting nearly unbiased selection with respect to both quiescent and star-forming galaxies. The numerous spectroscopic redshifts available in the EGS are used to train an artificial neural network to estimate photometric redshifts. The distribution of photometric redshift errors is Gaussian with standard deviation ∼0.025(1 + z), and the fraction of redshift failures (>3σ errors) is about 3.5%. A new method of validation based on pair statistics confirms the estimate of standard deviation even for galaxies lacking spectroscopic redshifts. Basic galaxy properties measured include rest-frame U-B colors, B- and K-band absolute magnitudes, and stellar masses. We divide the sample into quiescent and star-forming galaxies according to their rest-frame U-B colors and 24-3.6 μm flux density ratios and derive rest K-band luminosity functions and stellar mass functions for quiescent, star-forming, and all galaxies. The results show that massive, quiescent galaxies were in place by z ≈ 1, but lower mass galaxies generally ceased their star formation at later epochs. © 2013. The American Astronomical Society. All rights reserved..


Seds: The spitzer extended deep survey. Survey design, photometry, and deep irac source counts

Astrophysical Journal 769 (2013)

MLN Ashby, SP Willner, GG Fazio, JS Huang, R Arendt, P Barmby, G Barro, EF Bell, R Bouwens, A Cattaneo, D Croton, R Davé, JS Dunlop, E Egami, S Faber, K Finlator, NA Grogin, P Guhathakurta, L Hernquist, JL Hora, G Illingworth, A Kashlinsky, AM Koekemoer, DC Koo, I Labbé, Y Li, L Lin, H Moseley, K Nandra, J Newman, K Noeske, M Ouchi, M Peth, D Rigopoulou, B Robertson, V Sarajedini, L Simard, HA Smith, Z Wang, R Wechsler, B Weiner, G Wilson, S Wuyts, T Yamada, H Yan

The Spitzer Extended Deep Survey (SEDS) is a very deep infrared survey within five well-known extragalactic science fields: the UKIDSS Ultra-Deep Survey, the Extended Chandra Deep Field South, COSMOS, the Hubble Deep Field North, and the Extended Groth Strip. SEDS covers a total area of 1.46 deg 2 to a depth of 26 AB mag (3σ) in both of the warm Infrared Array Camera (IRAC) bands at 3.6 and 4.5 μm. Because of its uniform depth of coverage in so many widely-separated fields, SEDS is subject to roughly 25% smaller errors due to cosmic variance than a single-field survey of the same size. SEDS was designed to detect and characterize galaxies from intermediate to high redshifts (z = 2-7) with a built-in means of assessing the impact of cosmic variance on the individual fields. Because the full SEDS depth was accumulated in at least three separate visits to each field, typically with six-month intervals between visits, SEDS also furnishes an opportunity to assess the infrared variability of faint objects. This paper describes the SEDS survey design, processing, and publicly-available data products. Deep IRAC counts for the more than 300,000 galaxies detected by SEDS are consistent with models based on known galaxy populations. Discrete IRAC sources contribute 5.6 ± 1.0 and 4.4 ± 0.8 nW m-2 sr-1 at 3.6 and 4.5 μm to the diffuse cosmic infrared background (CIB). IRAC sources cannot contribute more than half of the total CIB flux estimated from DIRBE data. Barring an unexpected error in the DIRBE flux estimates, half the CIB flux must therefore come from a diffuse component. © 2013. The American Astronomical Society. All rights reserved.


HerMES: The far-infrared emission from dust-obscured galaxies

Astrophysical Journal 775 (2013)

JA Calanog, J Wardlow, H Fu, A Cooray, RJ Assef, J Bock, CM Casey, A Conley, D Farrah, E Ibar, J Kartaltepe, G Magdis, L Marchetti, SJ Oliver, I Pérez-Fournon, D Riechers, D Rigopoulou, IG Roseboom, B Schulz, D Scott, M Symeonidis, M Vaccari, M Viero, M Zemcov

Dust-obscured galaxies (DOGs) are an ultraviolet-faint, infrared-bright galaxy population that reside at z ∼ 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 deg2 of the Cosmic Evolution Survey. The 3077 DOGs have 〈z〉 = 1.9 ± 0.3 and are selected from 24 μm and r + observations using a color cut of r +-[24] ≥ 7.5 (AB mag) and S 24 ≥ 100 μJy. 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 μm (≥3σ). 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) × 1012 L⊙ and (0.77 ± 0.08) × 10 12 L⊙, and dust temperatures of (33 ± 7) K and (37 ± 5) K, respectively. The IR luminosity function for DOGs with S 24 ≥ 100 μJy 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 μm 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 μJy. 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 ∼ 2. © 2013. The American Astronomical Society. All rights reserved.


Erratum to The herschel* pep/hermes luminosity function - i. probing the evolution of PACS selected galaxies to z ̃ 4 [MNRAS 436, (2013) 2875-2876]

Monthly Notices of the Royal Astronomical Society 436 (2013) 2875-2876

C Gruppioni, F Pozzi, G Rodighiero, I Delvecchio, S Berta, L Pozzetti, G Zamorani, P Andreani, A Cimatti, O Ilbert, E Le Floc'h, D Lutz, B Magnelli, L Marchetti, L Monaco, R Nordon, S Oliver, P Popesso, L Riguccini, I Roseboom, DJ Rosario, M Sargent, M Vaccari, B Altieri, H Aussel, A Bongiovanni, J Cepa, E Daddi, H Doḿlnguez-Śanchez, D Elbaz, N F̈orster Schreiber, R Genzel, A Iribarrem, M Magliocchetti, R Maiolino, A Poglitsch, A Ṕerez Garćla, M Sanchez-Portal, E Sturm, L Tacconi, I Valtchanov, A Amblard, V Arumugam, M Bethermin, J Bock, A Boselli, V Buat, D Burgarella, N Castro-Rodŕlguez, A Cava, P Chania, DL Clements, A Conley, A Cooray, CD Dowell, E Dwek, S Eales, A Franceschini, J Glenn, M Griffin, E Hatziminaoglou, E Ibar, K Isaak, RJ Ivison, G Lagache, L Levenson, N Lu, S Madden, B Maffei, G Mainetti, HT Nguyen, B O'Halloran, MJ Page, P Panuzzo, A Papageorgiou, CP Pearson, I Ṕerez-Fournon, M Pohlen, D Rigopoulou, M Rowan-Robinson, B Schulz, D Scott, N Seymour, DL Shupe, AJ Smith, JA Stevens, M Symeonidis, M Trichas, KE Tugwell, L Vigroux, L Wang, G Wright, CK Xu, M Zemcov, S Bardelli, M Carollo, T Contini, O Le F́evre, S Lilly, V Mainieri


The James Clerk Maxwell Telescope Nearby Galaxies Legacy Survey - IX. <sup>12</sup>CO J = 3→2 observations of NGC 2976 and NGC 3351

Monthly Notices of the Royal Astronomical Society 436 (2013) 921-933

BK Tan, J Leech, D Rigopoulou, BE Warren, CD Wilson, D Attewell, M Azimlu, GJ Bendo, HM Butner, E Brinks, P Chanial, DL Clements, V Heesen, F Israel, JH Knapen, HE Matthews, AMJ Mortier, S Mühle, JR Sánchez-Gallego, RPJ Tilanus, A Usero, P Van der Werf, M Zhu

We present 12CO J = 3→2 maps of NGC 2976 and NGC 3351 obtained with the James Clerk Maxwell Telescope (JCMT), both early targets of the JCMT Nearby Galaxy Legacy Survey (NGLS). We combine the present observations with 12CO J = 1→0 data and find that the computed 12CO J = 3→2 to 12CO J = 1→0 line ratio (R31) agrees with values measured in other NGLS field galaxies. We compute the MH2 value and find that it is robust against the value of R31 used. Using HI data from The HI Nearby Galaxy Survey, we find a tight correlation between the surface density of H2 and star formation rate density for NGC 3351 when 12CO J = 3→2 data are used. Finally, we compare the 12CO J = 3→2 intensity with the polycyclic aromatic hydrocarbon (PAH) 8 μm surface brightness and find a good correlation in the high surface brightness regions. We extend this study to include all 25 Spitzer Infrared Nearby Galaxies Survey galaxies within the NGLS sample and find a tight correlation at large spatial scales. We suggest that both PAH 8 μm and 12CO J = 3→2 are likely to originate in regions of active star formation. © 2013 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society.


The complex physics of dusty star-forming galaxies at high redshifts as revealed by herschel and Spitzer

Astrophysical Journal 762 (2013)

B Lo Faro, A Franceschini, M Vaccari, L Silva, G Rodighiero, S Berta, J Bock, D Burgarella, V Buat, A Cava, DL Clements, A Cooray, D Farrah, A Feltre, EAG Solares, P Hurley, D Lutz, G Magdis, B Magnelli, L Marchetti, SJ Oliver, MJ Page, P Popesso, F Pozzi, D Rigopoulou, M Rowan-Robinson, IG Roseboom, D Scott, AJ Smith, M Symeonidis, L Wang, S Wuyts

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 &thk 1 and 2 selected in GOODS-S with 24 μm 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 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 ΔA V &thk 0.81 and 1.14) and higher stellar masses (by Δlog(M) &thk 0.16 and 0.36 dex) for z &thk 1 and z &thk 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 (&thk73% and &thk66% of the total LIR for z &thk 1 and z &thk 2 (U)LIRGs, respectively). © 2013. The American Astronomical Society. All rights reserved..


Herschel-ATLAS/GAMA: What determines the far-infrared properties of radio galaxies?

Monthly Notices of the Royal Astronomical Society 432 (2013) 609-625

JS Virdee, MJ Hardcastle, S Rawlings, D Rigopoulou, T Mauch, MJ Jarvis, A Verma, DJB Smith, I Heywood, SV White, M Baes, A Cooray, G de Zotti, S Eales, MJ Michalowski, N Bourne, A Dariush, L Dunne, R Hopwood, E Ibar, S Maddox, MWL Smith, E Valiante

We perform a stacking analysis of Herschel Astrophysical Terahertz Large Area Survey (H-ATLAS) data in order to obtain isothermal dust temperatures and rest-frame luminosities at 250 μm (L 250 ), for a well-defined sample of 1599 radio sources over the H-ATLAS Phase 1/Galaxy and Mass Assembly (GAMA) area. The radio sample is generated using a combination of NRAO VLA Sky Survey data and K-band United Kingdom Infrared Telescope Deep Sky Survey-Large Area Survey data, over the redshift range 0.01 < z < 0.8. The far-infrared(FIR) properties of the sample are investigated as a function of 1.4-GHz luminosity, redshift, projected radio-source size and radio spectral index. In order to search for stellar mass-dependent relations, we split the parent sample into those sources which are below and above 1.5 L *K .After correcting for stellar mass and redshift, we find no relation between the 250-μm luminosity and the 1.4-GHz radio luminosity of radio active galactic nuclei. This implies thata galaxy's nominal radio luminosity has little or no bearing on the star formation rate (SFR)and/or dust mass content of the host system, although this does not mean that other variables(e.g. radio source size) related to the jets do not have an effect. The L 250 of both the radio detected and non-radio-detected galaxies (defined as those sources not detected at 1.4 GHz but detected in the Sloan Digital Sky Survey with r< 22) rises with increasing redshift. Compact radio sources (<30 kpc) are associated with higher 250 μm luminosities and dust temperatures than their more extended (>30 kpc) counterparts. The higher dust temperature suggests that this may be attributed to enhanced SFRs in compact radio galaxies, but whether this is directly or indirectly due to radio activity (e.g. jet-induced or merger-driven star formation) is as yet unknown.For matched samples in L K and g-r, sub-1.5 L *K and super-1.5 L *K radio-detected galaxies have 0.89±0.18 and 0.49±0.12 times the 250μm luminosity of their non-radio-detected counterparts. Thus, while no difference in L 250 is observed in sub-1.5 L *K radio-detected galaxies, a strong deficit is observed in super-1.5 L *K radio-detected galaxies. We explain these results in terms of the hotter, denser and richer halo environments massive radio galaxies maintain and are embedded in. These environments are expected to quench the cold gas and dust supply needed for further star formation and therefore dust production. Our results indicate that all massive radio galaxies (>1.5 L *K ) may have systematically lower FIR luminosities(~25 per cent) than their colour-matched non-radio-detected counterparts. Finally, no relation between radio spectral index and L 250 is found for the subset of 1.4-GHz radio sources with detections at 330 MHz. © 2013 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society.


HerMES: Candidate gravitationally lensed galaxies and lensing statistics at submillimeter wavelengths

Astrophysical Journal 762 (2013)

JL Wardlow, A Cooray, F De Bernardis, A Amblard, V Arumugam, H Aussel, AJ Baker, M Béthermin, R Blundell, J Bock, A Boselli, C Bridge, V Buat, D Burgarella, RS Bussmann, A Cabrera-Lavers, J Calanog, JM Carpenter, CM Casey, N Castro-Rodríguez, A Cava, P Chanial, E Chapin, SC Chapman, DL Clements, A Conley, P Cox, CD Dowell, S Dye, S Eales, D Farrah, P Ferrero, A Franceschini, DT Frayer, C Frazer, H Fu, R Gavazzi, J Glenn, EA González Solares, M Griffin, MA Gurwell, AI Harris, E Hatziminaoglou, R Hopwood, A Hyde, E Ibar, RJ Ivison, S Kim, G Lagache, L Levenson, L Marchetti, G Marsden, P Martinez-Navajas, M Negrello, R Neri, HT Nguyen, B O'Halloran, SJ Oliver, A Omont, MJ Page, P Panuzzo, A Papageorgiou, CP Pearson, I Pérez-Fournon, M Pohlen, D Riechers, D Rigopoulou, IG Roseboom, M Rowan-Robinson, B Schulz, D Scott, N Scoville, N Seymour, DL Shupe, AJ Smith, A Streblyanska, A Strom, M Symeonidis, M Trichas, M Vaccari, JD Vieira, M Viero, L Wang, CK Xu, L Yan, M Zemcov

We present a list of 13 candidate gravitationally lensed submillimeter galaxies (SMGs) from 95 deg2 of the Herschel Multi-tiered Extragalactic Survey, a surface density of 0.14 ± 0.04 deg-2. The selected sources have 500 μm 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 (μ ≥ 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 ∼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 μm 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 μm. 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. © 2013. The American Astronomical Society. All rights reserved.


Erratum to The herschel* pep/hermes luminosity function - i. probing the evolution of PACS selected galaxies to z ̃ 4 [MNRAS 436, (2013) 2875-2876]

Monthly Notices of the Royal Astronomical Society 436 (2013) 2875-2876

C Gruppioni, L Pozzetti, G Zamorani, H Doḿlnguez-Śanchez, R Genzel, P Chania, S Bardelli, E Zucca, F Pozzi, I Delvecchio, A Cimatti, G Rodighiero, L Marchetti, M Vaccari, A Franceschini, G Mainetti, S Berta, D Lutz, B Magnelli, R Nordon, P Popesso, DJ Rosario, N F orster Schreiber, A Poglitsch, E Sturm, L Tacconi, P Andreani, A Iribarrem, E Hatziminaoglou, V Mainieri, O Ilbert, A Boselli, V Buat, D Burgarella, O Le F evre, E Le Floc'h, L Riguccini, M Sargent, H Aussel, E Daddi, D Elbaz, M Bethermin, S Madden, P Panuzzo, L Monaco, S Oliver, I Roseboom, AJ Smith, L Wang, V Arumugam, RJ Ivison, B Altieri, A Ṕerez Garćla, M Sanchez-Portal, I Valtchanov, A Bongiovanni, J Cepa, N Castro-Rodŕlguez, I Ṕerez-Fournon, M Magliocchetti, R Maiolino, A Amblard, J Bock, A Cooray, CD Dowell, L Levenson, N Lu, HT Nguyen, B Schulz, DL Shupe, CK Xu, M Zemcov, A Cava, DL Clements, B O'Halloran, M Rowan-Robinson, A Conley, J Glenn, E Dwek, S Eales, M Griffin, A Papageorgiou, M Pohlen, E Ibar, G Wright, K Isaak, G Lagache, B Maffei, MJ Page, N Seymour, M Symeonidis, KE Tugwell, CP Pearson, D Rigopoulou, D Scott, JA Stevens, M Trichas, L Vigroux, M Carollo, S Lilly, T Contini, A Renzini, M Scodeggio


The Herschel* PEP/HerMES luminosity function - I. Probing the evolution of PACS selected Galaxies to z ≃ 4

Monthly Notices of the Royal Astronomical Society 432 (2013) 23-52

C Gruppioni, F Pozzi, G Rodighiero, I Delvecchio, S Berta, L Pozzetti, G Zamorani, P Andreani, A Cimatti, O Ilbert, E Le Floc'h, D Lutz, B Magnelli, L Marchetti, P Monaco, R Nordon, S Oliver, P Popesso, L Riguccini, I Roseboom, DJ Rosario, M Sargent, M Vaccari, B Altieri, H Aussel, A Bongiovanni, J Cepa, E Daddi, H Domínguez-Sánchez, D Elbaz, NF Schreiber, R Genzel, A Iribarrem, M Magliocchetti, R Maiolino, A Poglitsch, AP García, M Sanchez-Portal, E Sturm, L Tacconi, I Valtchanov, A Amblard, V Arumugam, M Bethermin, J Bock, A Boselli, V Buat, D Burgarella, N Castro-Rodríguez, A Cava, P Chanial, DL Clements, A Conley, A Cooray, CD Dowell, E Dwek, S Eales, A Franceschini, J Glenn, M Griffin, E Hatziminaoglou, E Ibar, K Isaak, RJ Ivison, G Lagache, L Levenson, N Lu, S Madden, B Maffei, G Mainetti, HT Nguyen, B O'Halloran, MJ Page, P Panuzzo, A Papageorgiou, CP Pearson, I Pérez-Fournon, M Pohlen, D Rigopoulou, M Rowan-Robinson, B Schulz, D Scott, N Seymour, DL Shupe, AJ Smith, JA Stevens, M Symeonidis, M Trichas, KE Tugwell, L Vigroux, L Wang, G Wright, CK Xu, M Zemcov, S Bardelli, M Carollo, T Contini, O Le Févre, S Lilly, V Mainieri

We exploit the deep and extended far-IR data sets (at 70, 100 and 160 μm) of the Herschel Guaranteed Time Observation (GTO) PACS Evolutionary Probe (PEP) Survey, in combination with the Herschel Multi-tiered Extragalactic Survey data at 250, 350 and 500 μm, to derive the evolution of the rest-frame 35-, 60-, 90- and total infrared (IR) luminosity functions (LFs) up to z ~ 4.We detect very strong luminosity evolution for the total IR LF (L IR α (1 + z) 3.55 ± 0.10 up to z ~ 2, and α (1 + z) 1.62 ± 0.51 at 2 < z 4) combined with a density evolution (α (1 + z) -0.57 ± 0.22 up to z ~ 1 and α (1 + z) -3.92 ± 0.34 at 1 < z 4). In agreement with previous findings, the IR luminosity density (ρIR) increases steeply to z ~ 1, then flattens between z ~ 1 and z ~ 3 to decrease at z 3. Galaxies with different spectral energy distributions, masses and specific star formation rates (SFRs) 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 ρIR. Galaxies occupying the well-established SFR-stellar mass main sequence (MS) are found to dominate both the total IR LF and ρIR at all redshifts, with the contribution from off-MS sources (≥0.6 dex above MS) being nearly constant (~20 per cent of the total ρIR) and showing no significant signs of increase with increasing z over the whole 0.8 < z < 2.2 range. Sources with mass in the range 10 ≤ log(M/M⊙) ≤ 11 are found to dominate the total IR LF, with more massive galaxies prevailing at the bright end of the high-z (2) LF. A two-fold evolutionary scheme for IR galaxies is envisaged: on the one hand, a starburst-dominated phase in which the Super Massive Black Holes (SMBH) grows and is obscured by dust (possibly triggered by a major merging event), is followed by an AGN-dominated phase, then evolving towards a local elliptical. On the other hand, moderately star-forming 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. © 2013 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society.


The Herschel census of infrared SEDs through cosmic time

Monthly Notices of the Royal Astronomical Society 431 (2013) 2317-2340

M Symeonidis, M Vaccari, S Berta, MJ Page, D Lutz, V Arumugam, H Aussel, J Bock, A Boselli, V Buat, PL Capak, DL Clements, A Conley, L Conversi, A Cooray, CD Dowell, D Farrah, A Franceschini, E Giovannoli, J Glenn, M Griffin, E Hatziminaoglou, HS Hwang, E Ibar, O Ilbert, RJ Ivison, E Le Floc'h, S Lilly, JS Kartaltepe, B Magnelli, G Magdis, L Marchetti, HT Nguyen, R Nordon, B O'Halloran, SJ Oliver, A Omont, A Papageorgiou, H Patel, CP Pearson, I Perez-Fournon, M Pohlen, P Popesso, F Pozzi, D Rigopoulou, L Riguccini, D Rosario, IG Roseboom, M Rowan-Robinson, M Salvato, B Schulz, Douglas Scott, N Seymour, DL Shupe, AJ Smith, I Valtchanov, L Wang, CK Xu, M Zemcov, S Wuyts

Using Herschel data from the deepest SPIRE and PACS surveys (HerMES and PEP) in COSMOS, GOODS-S and GOODS-N, we examine the dust properties of infrared (IR)- luminous (LIR gt; 1010 L⊙) galaxies at 0.1 lt; z lt; 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 spectral energy distributions (SEDs) with broad far-IR peaks characterized by cool/extended dust emission and average dust temperatures in the 25-45 K range. Hot (T gt; 45 K) SEDs and cold (T lt; 25 K), 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 [LIR/L⊙] ~ 12.5 galaxies is about 10 K higher than that of their log [LIR/L⊙] ~ 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 10 K lower than what is measured locally (z ≲ 0.1). This is manifested as a flattening of the L-T relation, suggesting that (ultra)luminous infrared galaxies [(U)LIRGs] in the early Universe are typically characterized 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 lt; 35 K showing a two-fold increase from z ~ 0 to z ~ 2, whereas that of ULIRGs with T lt; 35 K shows a six-fold increase. Our results suggest a greater diversity in the IR-luminous population at high redshift, particularly for ULIRGs. © 2013 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society.

Pages