R. J. Ivison

French National Centre for Scientific Research, Lutetia Parisorum, Île-de-France, France

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Publications (700)2528.05 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: We report an unexpected variation in the positional offset distributions between Herschel-ATLAS sub-millimetre (submm) sources and their optical associations, depending on both 250-{\mu}m signal-to-noise ratio and 250/350-{\mu}m colour. We show that redder and brighter submm sources have optical associations with a broader distribution of positional offsets than would be expected if these offsets were due to random positional errors in the source extraction. The observation can be explained by two possible effects: either red submm sources trace a more clustered population than blue ones, and their positional errors are increased by confusion; or red submm sources are generally at high redshifts and are frequently associated with low-redshift lensing structures which are identified as false counterparts. We perform various analyses of the data, including the multiplicity of optical associations, the redshift and magnitude distributions in H-ATLAS in comparison to HerMES, and simulations of weak lensing, and we conclude that the effects are most likely to be explained by widespread weak lensing of Herschel-SPIRE sources by foreground structures. This has important consequences for counterpart identification and derived redshift distributions and luminosity functions of submm surveys.
    07/2014;
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    ABSTRACT: We present the detection of $^{12}$CO(2-1) in the $z = 4.44$ submillimetre galaxy ALESS65.1 using the Australia Telescope Compact Array. A previous ALMA study of submillimetre galaxies in the Extended Chandra Deep Field South determined the redshift of this optically and near-infrared undetected source through the measurement of [CII] 157.74 $\mu$m emission. Using the luminosity of the $^{12}$CO(2-1) emission we estimate the gas mass to be $M_{\rm gas} \sim 1.7 \times 10^{10}$ ${\rm M}_\odot$. The gas depletion timescale of ALESS65.1 is $\sim$ 25 Myr, similar to other high redshift submillimetre galaxies and consistent with $z > 4$ SMGs being the progenitors of massive "red-and-dead" galaxies at $z > 2$. The ratio of the [CII], $^{12}$CO and far-infrared luminosities implies a strong far-ultraviolet field of $G_0 \sim 10^{3.25}$, which is at the high end of the far-ultraviolet fields seen in local starbursts, but weaker than the far-ultraviolet fields of most nearby ULIRGs. The high ratio of $L_{\rm [CII]}/L_{\rm FIR} = 1.0 \times 10^{-3}$ observed in ALESS65.1, combined with $L_{\rm [CII]}/L_{\rm CO} \sim 2300$, is consistent with ALESS65.1 having more extended regions of intense star formation than local ULIRGs.
    07/2014;
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    ABSTRACT: [Abridged] Aims: This work focuses on one lensed system, HATLAS J142935.3-002836 (H1429-0028), selected in the Herschel-ATLAS field. Gathering a rich, multi-wavelength dataset, we aim to confirm the lensing hypothesis and model the background source's morphology and dynamics, as well as to provide a full physical characterisation. Methods: Multi-wavelength high-resolution data is utilised to assess the nature of the system. A lensing-analysis algorithm which simultaneously fits different wavebands is adopted to characterise the lens. The background galaxy dynamical information is studied by reconstructing the 3-D source-plane of the ALMA CO(J:4-3) transition. Near-IR imaging from HST and Keck-AO allows to constrain rest-frame optical photometry independently for the foreground and background systems. Physical parameters (such as stellar and dust masses) are estimated via modelling of the spectral energy distribution taking into account source blending, foreground obscuration, and differential magnification. Results: The system comprises a foreground edge-on disk galaxy (at z_sp=0.218) with an almost complete Einstein ring around it. The background source (at z_sp=1.027) is magnified by a factor of ~8-10 depending on wavelength. It is comprised of two components and a tens of kpc long tidal tail resembling the Antennae merger. As a whole, the system is a massive stellar system (1.32[-0.41,+0.63] x1E11 Mo) forming stars at a rate of 394+-90 Mo/yr, and has a significant gas reservoir M_ISM = 4.6+-1.7 x1E10 Mo. Its depletion time due to star formation alone is thus expected to be tau_SF=M_ISM/SFR=117+-51 Myr. The dynamical mass of one of the components is estimated to be 5.8+-1.7 x1E10 Mo, and, together with the photometric total mass estimate, it implies that H1429-0028 is a major merger system (1:2.8[-1.5,+1.8]).
    06/2014;
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    ABSTRACT: We present Keck-Adaptive Optics and Hubble Space Telescope high resolution near-infrared (IR) imaging for 500 um-bright candidate lensing systems identified by the Herschel Multi-tiered Extra-galactic Survey (HerMES) and Herschel Astrophysical Terahertz Survey (H-ATLAS). Out of 87 candidates with near-IR imaging, 15 (~17%) display clear near-IR lensing morphologies. We present near-IR lens models to reconstruct and recover basic rest-frame optical morphological properties of the background galaxies from 12 new systems. Sources with the largest near-IR magnification factors also tend to be the most compact, consistent with the size bias predicted from simulations and pre- vious lensing models for sub-millimeter galaxies. For four new sources that also have high-resolution sub-mm maps, we test for differential lensing between the stellar and dust components and find that the 880 um magnification factor (u_880) is ~1.5 times higher than the near-IR magnification factor (u_NIR), on average. We also find that the stellar emission is ~2 times more extended in size than dust. The rest-frame optical properties of our sample of Herschel-selected lensed SMGs are consistent with those of unlensed SMGs, which suggests that the two populations are similar.
    06/2014;
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    ABSTRACT: Ultra Steep Spectrum (USS) radio sources are one of the efficient tracers of powerful High-z Radio Galaxies (HzRGs). In contrast to searches for powerful HzRGs from radio surveys of moderate depths, fainter USS samples derived from deeper radio surveys can be useful in finding HzRGs at even higher redshifts and in unveiling a population of obscured weaker radio-loud AGN at moderate redshifts. Using our 325 MHz GMRT observations (5-sigma ~ 800 microJy) and 1.4 GHz VLA observations (5-sigma ~ 80 - 100 microJy) available in two subfields (viz., VLA-VIMOS VLT Deep Survey (VLA-VVDS) and Subaru X-ray Deep Field (SXDF)) of the XMM-LSS field, we derive a large sample of 160 faint USS radio sources and characterize their nature. The optical, IR counterparts of our USS sample sources are searched using existing deep surveys, at respective wavelengths. We attempt to unveil the nature of our faint USS sources using diagnostic techniques based on mid-IR colors, flux ratios of radio to mid-IR, and radio luminosities. Redshift estimates are available for 86/116 (~ 74%) USS sources in the VLA-VVDS field and for 39/44 (~ 87%) USS sources in the SXDF fields with median values (z_median) ~ 1.18 and ~ 1.57, which are higher than that for non-USS radio sources (z_median non-USS ~ 0.99 and ~ 0.96), in the two subfields, respectively. The flux ratio of radio to mid-IR (S_1.4 GHz/S_3.6 micron) versus redshift diagnostic plot suggests that more than half of our USS sample sources distributed over z ~ 0.5 to 3.8 are likely to be hosted in obscured environments. A significant fraction (~ 26% in the VLA-VVDS and ~ 13% in the SXDF) of our USS sources without redshift estimates mostly remain unidentified in the existing optical, IR surveys, and exhibit high radio to mid-IR flux ratio limits similar to HzRGs, and thus, can be considered as potential HzRG candidates.
    05/2014;
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    ABSTRACT: Ultra Steep Spectrum (USS) radio sources are one of the efficient tracers of powerful High-z Radio Galaxies (HzRGs). In contrast to searches for powerful HzRGs from radio surveys of moderate depths, fainter USS samples derived from deeper radio surveys can be useful in finding HzRGs at even higher redshifts and in unveiling a population of obscured weaker radio-loud AGN at moderate redshifts. Using our 325 MHz GMRT observations (5-sigma ~ 800 microJy) and 1.4 GHz VLA observations (5-sigma ~ 80 - 100 microJy) available in two subfields (viz., VLA-VIMOS VLT Deep Survey (VLA-VVDS) and Subaru X-ray Deep Field (SXDF)) of the XMM-LSS field, we derive a large sample of 160 faint USS radio sources and characterize their nature. The optical, IR counterparts of our USS sample sources are searched using existing deep surveys, at respective wavelengths. We attempt to unveil the nature of our faint USS sources using diagnostic techniques based on mid-IR colors, flux ratios of radio to mid-IR, and radio luminosities. Redshift estimates are available for 86/116 (~ 74%) USS sources in the VLA-VVDS field and for 39/44 (~ 87%) USS sources in the SXDF fields with median values (z_median) ~ 1.18 and ~ 1.57, which are higher than that for non-USS radio sources (z_median non-USS ~ 0.99 and ~ 0.96), in the two subfields, respectively. The flux ratio of radio to mid-IR (S_1.4 GHz/S_3.6 micron) versus redshift diagnostic plot suggests that more than half of our USS sample sources distributed over z ~ 0.5 to 3.8 are likely to be hosted in obscured environments. A significant fraction (~ 26% in the VLA-VVDS and ~ 13% in the SXDF) of our USS sources without redshift estimates mostly remain unidentified in the existing optical, IR surveys, and exhibit high radio to mid-IR flux ratio limits similar to HzRGs, and thus, can be considered as potential HzRG candidates.
    04/2014;
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    ABSTRACT: We have constructed a sample of radio-loud and radio-quiet quasars from the Faint Im- ages Radio Sky at Twenty-one centimetres (FIRST) and the Sloan Digital Sky Survey Data Release 7 (SDSS DR7), over the H-ATLAS Phase 1 Area (9h, 12h and 14.5h). Using a stacking analysis we find a significant correlation between the far-infrared luminosity and 1.4-GHz luminosity for radio-loud quasars. Partial correlation analysis confirms the intrinsic correlation after removing the redshift contribution while for radio-quiet quasars no partial correlation is found. Using a single-temperature grey-body model we find a general trend of lower dust temperatures in the case of radio-loud quasars comparing to radio-quiet quasars. Also, radio-loud quasars are found to have almost constant mean values of dust mass along redshift and optical luminosity bins. In addition, we find that radio-loud quasars at lower optical luminosities tend to have on average higher FIR and 250-micron luminosity with respect to radio-quiet quasars with the same optical luminosites. Even if we use a two-temperature grey-body model to describe the FIR data, the FIR luminosity excess remains at lower optical luminosities. These results suggest that powerful radio jets are associated with star formation especially at lower accretion rates.
    04/2014; 442(2).
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    ABSTRACT: We discuss the restframe UV emission from the starbursting galaxy HFLS3 at z=6.34, discovered in Herschel/SPIRE data due to its red color in the submm wavelengths from 250-500 um. The apparent inst. SFR of HFLS3 inferred from the total FIR luminosity measured with over 15 photometric data points between 100 to 1000 um is 2900 Msun/yr. Keck/NIRC2 Ks band adaptive optics imaging data showed two potential NIR counterparts near HFLS3. Previously, the northern galaxy was taken to be in the foreground at z=2.1 while the southern galaxy was assumed to HFLS3's NIR counterpart. New HST/WFC3 and ACS imaging data show both optically bright galaxies are in the foreground at z<6. A new lensing model based on HST data and mm-wave continuum emission yields a magnification of 2.2+/-0.3. The lack of multiple imaging constrains the lensing magnification to be lower than either 2.7 or 3.5 at the 95% confidence level for the two scenarios, which attribute one or two components to HFLS3 in the source plane. Correcting for gravitational lensing, the inst. SFR is 1320 Msun/yr with the 95% confidence lower limit around 830 Msun/yr. Using models for the restframe UV to FIR SED, the ave. SFR over the last 100 Myr is around 660 Msun/yr. The dust and stellar masses of HFLS3 from the same SED models are 3x10^8 Msun and ~5x10^10 Msun, respectively, with large systematic uncertainties on assumptions related to the SED model. With HST/WFC3 images we also find diffuse NIR emission about 0.5" (~3 kpc) SW of HFLS3 that remains undetected in the ACS data. The emission has a photometric redshift consistent with either z~6 or a dusty galaxy template at z~2. If at the same redshift as HFLS3 the detected diffuse emission could be part of the complex merger system that could be triggering the starburst. Alternatively, it could be part of the foreground structure at z~2.1 that is responsible for lensing of HFLS3.
    The Astrophysical Journal 04/2014; 790(1). · 6.73 Impact Factor
  • 03/2014;
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    ABSTRACT: We have constructed a sample of radio-loud and radio-quiet quasars from the Faint Im- ages Radio Sky at Twenty-one centimetres (FIRST) and the Sloan Digital Sky Survey Data Release 7 (SDSS DR7), over the H-ATLAS Phase 1 Area (9h, 12h and 14.5h). Using a stacking analysis we find a significant correlation between the far-infrared luminosity and 1.4-GHz luminosity for radio-loud quasars. Partial correlation analysis confirms the intrinsic correlation after removing the redshift contribution while for radio-quiet quasars no partial correlation is found. Using a single-temperature grey-body model we find a general trend of lower dust temperatures in the case of radio-loud quasars comparing to radio-quiet quasars. Also, radio-loud quasars are found to have almost constant mean values of dust mass along redshift and optical luminosity bins. In addition, we find that radio-loud quasars at lower optical luminosities tend to have on average higher FIR and 250-micron luminosity with respect to radio-quiet quasars with the same optical luminosites. Even if we use a two-temperature grey-body model to describe the FIR data, the FIR luminosity excess remains at lower optical luminosities. These results suggest that powerful radio jets are associated with star formation especially at lower accretion rates.
    03/2014;
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    ABSTRACT: The $\textit{Herschel}$ DEBRIS, DUNES and GT programmes observed 37 exoplanet host stars within 25 pc at 70, 100 and 160 $\mu$m with the sensitivity to detect far-infrared excess emission at flux density levels only an order of magnitude greater than that of the Solar system's Edgeworth-Kuiper belt. Here we present an analysis of that sample, using it to more accurately determine the (possible) level of dust emission from these exoplanet host stars and thereafter determine the links between the various components of these exoplanetary systems through statistical analysis. We have fitted the flux densities measured from recent \textit{Herschel} observations with a simple two parameter ($T_{d}$, $L_{\rm IR}/L_{\star}$) black body model (or to the 3-$\sigma$ upper limits at 100 $\mu$m). From this uniform approach we calculate the fractional luminosity, radial extent, dust temperature and disc mass. We then plotted the calculated dust luminosity or upper limits against the stellar properties, e.g. effective temperature, metallicity, age, and identified correlations between these parameters. A total of eleven debris discs are identified around the 37 stars in the sample. An incidence of ten cool debris discs around the Sun-like exoplanet host stars (29 $\pm$ 9 %) is consistent with the detection rate found by DUNES (20.2 $\pm$ 2.0 %). For the debris disc systems, the dust temperatures range from 20 to 80 K, and fractional luminosities ($L_{\rm IR}/L_{\star}$) between 2.4 $\times$10$^{-6}$ and 4.1 $\times$10$^{-4}$. In the case of non-detections, we calculated typical 3-$\sigma$ upper limits to the dust fractional luminosities of a few $\times10^{-6}$. We recover the previously identified correlation between stellar metallicity and hot Jupiter planets in our data set. We find a correlation between the increased presence of dust, lower planet masses and lower stellar metallicities. (abridged)
    03/2014;
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    ABSTRACT: We present a comparison of the physical properties of a rest-frame $250\mu$m selected sample of massive, dusty galaxies from $0<z<5.3$. Our sample comprises 29 high-redshift submillimetre galaxies (SMGs) from the literature, and 843 dusty galaxies at $z<0.5$ from the Herschel-ATLAS, selected to have a similar stellar mass to the SMGs. The $z>1$ SMGs have an average SFR of $390^{+80}_{-70}\,$M$_\odot$yr$^{-1}$ which is 120 times that of the low-redshift sample matched in stellar mass to the SMGs (SFR$=3.3\pm{0.2}$ M$_\odot$yr$^{-1}$). The SMGs harbour a substantial mass of dust ($1.2^{+0.3}_{-0.2}\times{10}^9\,$M$_\odot$), compared to $(1.6\pm0.1)\times{10}^8\,$M$_\odot$ for low-redshift dusty galaxies. At low redshifts the dust luminosity is dominated by the diffuse ISM, whereas a large fraction of the dust luminosity in SMGs originates from star-forming regions. At the same dust mass SMGs are offset towards a higher SFR compared to the low-redshift H-ATLAS galaxies. This is not only due to the higher gas fraction in SMGs but also because they are undergoing a more efficient mode of star formation, which is consistent with their bursty star-formation histories. The offset in SFR between SMGs and low-redshift galaxies is similar to that found in CO studies, suggesting that dust mass is as good a tracer of molecular gas as CO.
    03/2014;
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    ABSTRACT: We present the results from a 1.1 mm imaging survey of the SSA22 field, known for having an overdensity of z=3.1 Lyman-alpha emitting galaxies (LAEs), taken with the AzTEC camera on the Atacama Submillimeter Telescope Experiment (ASTE). We imaged a 950 arcmin$^2$ field down to a 1 sigma sensitivity of 0.7-1.3 mJy/beam to find 125 submillimeter galaxies (SMGs) with a signal to noise ratio >= 3.5. Counterpart identification using radio and near/mid-infrared data was performed and one or more counterpart candidates were found for 59 SMGs. Photometric redshifts based on optical to near-infrared images were evaluated for 45 SMGs of these SMGs with Spitzer/IRAC data, and the median value is found to be z=2.4. By combining these estimation with estimates from the literature we determined that 10 SMGs might lie within the large-scale structure at z=3.1. The two-point angular cross-correlation function between LAEs and SMGs indicates that the positions of the SMGs are correlated with the z=3.1 protocluster. These results suggest that the SMGs were formed and evolved selectively in the high dense environment of the high redshift universe. This picture is consistent with the predictions of the standard model of hierarchical structure formation.
    03/2014; 440(4).
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    ABSTRACT: We describe a search for submillimeter emission in the vicinity of one of the most distant, luminous galaxies known, HerMES FLS3 at z=6.34, exploiting it as a signpost to a potentially biased region of the early Universe, as might be expected in hierarchical structure formation models. Imaging to the confusion limit with the innovative, wide-field submillimeter bolometer camera, SCUBA-2, we are sensitive to colder and/or less luminous galaxies in the surroundings of HFLS3. We use the Millennium Simulation to illustrate that HFLS3 may be expected to have companions if it is as massive as claimed, but find no significant evidence from the surface density of SCUBA-2 galaxies in its vicinity, or their colors, that HFLS3 marks an over-density of dusty, star-forming galaxies. We cannot rule out the presence of dusty neighbours with confidence, but deeper 450-um imaging has the potential to more tightly constrain the redshifts of nearby galaxies, at least one of which likely lies at z>~5. If associations with HFLS3 can be ruled out, this could be taken as evidence that HFLS3 is less biased than a simple extrapolation of the Millennium Simulation may imply. This could suggest either that it represents a rare short-lived, but highly luminous, phase in the evolution of an otherwise typical galaxy, or that this system has suffered amplification due to a foreground gravitational lens and so is not as intrinsically luminous as claimed.
    03/2014;
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    ABSTRACT: We report the results from a 19-hr integration with the SPIRE Fourier Transform Spectrometer aboard the Herschel Space Observatory which has revealed the presence of a molecular outflow from the Cosmic Eyelash (SMM J2135-0102, hereafter SMMJ2135) via the detection of blueshifted OH absorption. Detections of several fine-structure emission lines indicate low-excitation HII regions contribute strongly to the [CII] luminosity in this z = 2.3 ULIRG. The OH feature suggests a maximum wind velocity of 700 km/s and outflow rate of ~60 Msun/yr. This is lower than the expected escape velocity of the host dark matter halo, ~1000 km/s. A large fraction of the available molecular gas could thus be converted into stars via a burst protracted by the resulting gas fountain, until an AGN-driven outflow can eject the remaining gas.
    02/2014;
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    ABSTRACT: The use of submillimeter dust continuum emission to probe the mass of interstellar dust and gas in galaxies is empirically calibrated using samples of local star-forming galaxies, Planck observations of the Milky Way, and high-redshift submillimeter galaxies. All of these objects suggest a similar calibration, strongly supporting the view that the Rayleigh-Jeans tail of the dust emission can be used as an accurate and very fast probe of the interstellar medium (ISM) in galaxies. We present ALMA Cycle 0 observations of the Band 7 (350 GHz) dust emission in 107 galaxies from z = 0.2 to 2.5. Three samples of galaxies with a total of 101 galaxies were stellar-mass-selected from COSMOS to have M * 1011M ☉: 37 at z ~ 0.4, 33 at z ~ 0.9, and 31 at z = 2. A fourth sample with six infrared-luminous galaxies at z = 2 was observed for comparison with the purely mass-selected samples. From the fluxes detected in the stacked images for each sample, we find that the ISM content has decreased by a factor ~6 from 1 to 2 × 1010M ☉ at both z = 2 and 0.9 down to ~2 × 109M ☉ at z = 0.4. The infrared-luminous sample at z = 2 shows a further ~4 times increase in M ISM compared with the equivalent non-infrared-bright sample at the same redshift. The gas mass fractions are ~2% ± 0.5%, 12% ± 3%, 14% ± 2%, and 53% ± 3% for the four subsamples (z = 0.4, 0.9, and 2 and infrared-bright galaxies).
    The Astrophysical Journal 02/2014; 783(2):84. · 6.73 Impact Factor
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    ABSTRACT: We present new observations of the XZ Tau system made at high angular resolution (55 milliarcsec) with the Karl G. Jansky Very Large Array (VLA) at a wavelength of 7 mm. Observations of XZ Tau made with the VLA in 2004 appeared to show a triple system, with XZ Tau A resolved into two sources, XZ Tau A and XZ Tau C. The angular separation of XZ Tau A and C (0.09 arcsec) suggested a projected orbital separation of around 13 AU with a possible orbital period of around 40 yr. Our observations were obtained approximately 8 yr later, a fifth of this putative orbital period, and should therefore allow us to constrain the orbit of XZ Tau C, and evaluate the possibility that a recent periastron passage of C coincided with the launch of extended optical outflows from XZ Tau A. Despite improved sensitivity and resolution compared with previous observations, we find no evidence of XZ Tau C in our data. Components A and B are detected with a signal-to-noise ratio greater than ten; their orbits are consistent with previous studies, although the emission from XZ Tau A appears to be weaker. Three possible interpretations are offered: either XZ Tau C is transiting XZ Tau A, which is broadly consistent with the periastron passage hypothesis, or the emission seen in 2004 was that of a transient, or XZ Tau C does not exist. A fourth interpretation, that XZ Tau C was ejected from the system, is dismissed due to the lack of angular momentum redistribution in the orbits of XZ Tau A and XZ Tau B that would result from such an event. Our observations are insufficient to distinguish between the remaining possibilities, at least not until we obtain further VLA observations at a sufficiently later time. A further non-detection would allow us to reject the transit hypothesis, and the periastron passage of XZ Tau C as agent of XZ Tau A's outflows.
    02/2014; 439(4).
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    ABSTRACT: We report a highly significant ($>10\sigma$) spatial correlation between galaxies with $S_{350\mu\rm m}\ge 30\,$mJy detected in the equatorial fields of the \textsl{Herschel} Astrophysical Terahertz Large Area Survey (H-ATLAS) with estimated redshifts $\gtrsim 1.5$, and SDSS or GAMA galaxies at $0.2\le z\le 0.6$. The significance of the cross-correlation is much higher than those reported so far for samples with non-overlapping redshift distributions selected in other wavebands. Extensive, realistic simulations of clustered sub-mm galaxies amplified by foreground structures confirm that the cross-correlation is explained by weak gravitational lensing ($\mu<2$). The simulations also show that the measured amplitude and range of angular scales of the signal are larger than can be accounted for by galaxy-galaxy weak lensing. However, for scales $\lesssim 2\,$arcmin, the signal can be reproduced if SDSS/GAMA galaxies act as signposts of galaxy groups/clusters with halo masses in the range ~$10^{13.2}$--$10^{14.5} M_{\odot}$. The signal detected on larger scales appears to reflect the clustering of such halos. Finally, we make use of our simulations to show that lensing can induce an apparent clustering of randomly distributed background galaxies, but the amplitude of the corresponding angular correlation function is at least a factor of 10 lower than observed for our sample of H-ATLAS galaxies. Moreover, although halos of group/cluster size are the dominant contributors to the cross-correlation between H-ATLAS and SDSS/GAMA galaxies, the gravitational magnification effects on counts of sub-mm sources are nevertheless dominated by galaxy-galaxy strong lensing.
    01/2014;
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    ABSTRACT: The use of submm dust continuum emission to probe the mass of interstellar dust and gas in galaxies is empirically calibrated using samples of local star forming galaxies, Planck observations of the Milky Way and high redshift submm galaxies (SMGs). All of these objects suggest a similar calibration, strongly supporting the view that the Rayleigh-Jeans (RJ) tail of the dust emission can be used as an accurate and very fast probe of the ISM in galaxies. We present ALMA Cycle 0 observations of the Band 7 (350 GHz) dust emission in 107 galaxies from z = 0.2 to 2.5. Three samples of galaxies with a total of 101 galaxies were stellar mass-selected from COSMOS to have $M_* \simeq10^{11}$\msun: 37 at z$\sim0.4$, 33 at z$\sim0.9$ and 31 at z$=2$. A fourth sample with 6 IR luminous galaxies at z = 2 was observed for comparison with the purely mass-selected samples. From the fluxes detected in the stacked images for each sample, we find that the ISM content has decreased a factor $\sim 6$ from $1 - 2 \times 10^{10}$\msun at both z = 2 and 0.9 down to $\sim 2 \times 10^9$\msun at z = 0.4. The IR luminous sample at z = 2 shows a further $\sim 4$ times increase in M$_{ISM}$ compared to the equivalent non-IR bright sample at the same redshift. The gas mass fractions are $\sim 2\pm0.5, 12\pm3, 14\pm2 ~\rm{and} ~53\pm3$ $\%$ for the four subsamples (z = 0.4, 0.9, 2 and IR bright galaxies).
    01/2014;
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    ABSTRACT: We use the Herschel ATLAS (H-ATLAS) Phase I data to study the conditional luminosity function of far-IR (250 um) selected galaxies in optically-selected galaxy groups from the GAMA spectroscopic survey, as well as environmental effects on the far-IR-to-optical colour. We applied two methods, which gave consistent results for the far-IR conditional luminosity functions. The direct matching method matches H-ATLAS sources to GAMA/SDSS galaxies, then links the optical counterparts to GAMA groups. The stacking method counts the number of far-IR sources within the projected radii of GAMA groups, subtracting the local background. We investigated the dependence of the far-IR (250 um) luminosity function on group mass in the range 10d12 < M_h < 10d14Msun/h and on redshift in the range 0 < z < 0.4, using a sample of 3000 groups containing H-ATLAS sources with GAMA redshifts over an area of 126 sq. deg. We find that the characteristic 250 um luminosity, L^*(250), increases with group mass up to M_h ~ 10d13Msun/h, but is roughly constant above this, while it increases with redshift at high group masses, but less so at low masses. We also find that the group far-IR luminosity-to-mass ratio L(250)/M_h increases with redshift and is higher in low-mass groups. We estimate that around 70% of the 250 um luminosity density in the local universe is contributed by groups with M_h > 10d12Msun/h. We also find that the far-IR-to-optical colours of H-ATLAS galaxies are independent of group mass over the range 10d12 < M_h <10d14Msun/h in the local universe. We also compare our observational results with recent semi-analytical models, and find that none of these galaxy formation model can reproduce the conditional far-IR luminosity functions of galaxy groups.
    01/2014;

Publication Stats

11k Citations
2,528.05 Total Impact Points

Institutions

  • 2001–2014
    • French National Centre for Scientific Research
      • Institut d'astrophysique spatiale (IAS)
      Lutetia Parisorum, Île-de-France, France
    • Massachusetts Institute of Technology
      • Kavli Institute for Astrophysics and Space Research
      Cambridge, Massachusetts, United States
  • 1997–2014
    • The University of Edinburgh
      • • Institute for Astronomy (IfA)
      • • School of Physics and Astronomy
      Edinburgh, Scotland, United Kingdom
  • 2013
    • Rutgers, The State University of New Jersey
      • Department Physics and Astronomy
      New Brunswick, New Jersey, United States
    • Cornell University
      • Department of Astronomy
      Ithaca, New York, United States
  • 2008–2013
    • California Institute of Technology
      Pasadena, California, United States
  • 2005–2013
    • University of California, Irvine
      • Department of Physics and Astronomy
      Irvine, CA, United States
    • The University of Manchester
      Manchester, England, United Kingdom
  • 2001–2013
    • The Royal Observatory, Edinburgh
      Edinburgh, Scotland, United Kingdom
  • 2012
    • Ruhr-Universität Bochum
      Bochum, North Rhine-Westphalia, Germany
    • University of Nottingham
      • School of Physics and Astronomy
      Nottigham, England, United Kingdom
  • 2011–2012
    • University of Colorado at Boulder
      • • Center for Astrophysics and Space Astronomy
      • • Department of Astrophysical and Planetary Sciences
      Boulder, Colorado, United States
    • Imperial College London
      • Department of Physics
      Londinium, England, United Kingdom
    • Cardiff University
      • School of Physics and Astronomy
      Cardiff, Wales, United Kingdom
    • Leiden University
      • Leiden Observartory
      Leiden, South Holland, Netherlands
    • Institute for Research in Fundamental Sciences (IPM)
      • School of Astronomy
      Tehrān, Ostan-e Tehran, Iran
    • Observatoire de Paris
      Lutetia Parisorum, Île-de-France, France
    • University of Hertfordshire
      • Centre for Astrophysics Research (CAR)
      Hatfield, ENG, United Kingdom
  • 1998–2012
    • University College London
      • Department of Physics and Astronomy
      Londinium, England, United Kingdom
  • 2010
    • Georgia Institute of Technology
      • School of Physics
      Atlanta, GA, United States
    • National Radio Astronomy Observatory
      Charlottesville, Virginia, United States
    • The Open University (UK)
      • Department of Physical Sciences
      Milton Keynes, England, United Kingdom
    • University of Leuven
      Louvain, Flanders, Belgium
  • 2007–2010
    • Scottish Universities Physics Alliance
      Glasgow, Scotland, United Kingdom
  • 2005–2009
    • University of Cambridge
      • Institute of Astronomy
      Cambridge, England, United Kingdom
  • 2006
    • Harvard-Smithsonian Center for Astrophysics
      • Smithsonian Astrophysical Observatory
      Cambridge, Massachusetts, United States
    • University of Sydney
      • School of Physics
      Sydney, New South Wales, Australia
  • 1999–2006
    • Durham University
      • Department of Physics
      Durham, ENG, United Kingdom
  • 2004
    • Joint Astronomy Centre
      Hilo, Hawaii, United States
  • 1995
    • Liverpool John Moores University
      • Astrophysics Research Institute
      Liverpool, ENG, United Kingdom
    • University of Toronto
      • Department of Astronomy and Astrophysics
      Toronto, Ontario, Canada
  • 1993
    • University of Central Lancashire
      Preston, England, United Kingdom
  • 1991
    • Slovak Academy of Sciences
      Presburg, Bratislavský, Slovakia