Browsing by Author "Del Moro, A."

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    Active galactic nuclei and their large-scale structure: an eROSITA mock catalogue
    (2019) Comparat, J.; Merloni, A.; Salvato, M.; Nandra, K.; Boller, T.; Georgakakis, A.; Finoguenov, A.; Dwelly, T.; Buchner, J.; Del Moro, A.; Clerc, N.; Wang, Y.; Zhao, G.; Prada, F.; Yepes, G.; Brusa, M.; Krumpe, M.; Liu, T.
    In the context of the upcoming SRG/eROSITA survey, we present an N-body simulation-based mock catalogue for X-ray-selected active galactic nucleus (AGN) samples. The model reproduces the observed hard X-ray AGN luminosity function (XLF) and the soft X-ray logN-logS from redshift 0 to 6. The XLF is reproduced to within +/- 5 per cent and the logN-logS to within +/- 20 per cent. We develop a joint X-ray - optical extinction and classification model. We adopt a set of empirical spectral energy distributions to predict observed magnitudes in the UV, optical, and NIR. With the latest eROSITA all sky survey sensitivity model, we create a high-fidelity full-sky mock catalogue of X-ray AGN. It predicts their distributions in right ascension, declination, redshift, and fluxes. Using empirical medium resolution optical spectral templates and an exposure time calculator, we find that 1.1 x 10(6) (4 x 10(5)) fibre-hours are needed to follow-up spectroscopically from the ground the detected X-ray AGN with an optical magnitude 21 < r < 22.8 (22.8 < r < 25) with a 4-m (8-m) class multiobject spectroscopic facility. We find that future clustering studies will measure the AGN bias to the per cent level at redshift z < 1.2 and should discriminate possible scenarios of galaxy-AGN co-evolution. We predict the accuracy to which the baryon acoustic oscillation standard ruler will be measured using X-ray AGN: better than 3 per cent for AGN between redshift 0.5 to 3 and better than 1 per cent using the Ly alpha forest of X-ray QSOs discovered between redshift 2 and 3. eROSITA will provide an outstanding set of targets for future galaxy evolution and cosmological studies.
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    GOODS- Herschel : Radio-excess signature of hidden AGN activity in distant star-forming galaxies
    (2013) Del Moro, A.; Alexander, D.; Mullaney, J.; Daddi, E.; Pannella, M.; Bauer, Franz Erik
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    GOODS-Herschel: the far-infrared view of star formation in active galactic nucleus host galaxies since z ∼ 3
    (2012) Mullaney, J. R.; Pannella, M.; Daddi, E.; Alexander, D. M.; Elbaz, D.; Hickox, R. C.; Bournaud, F.; Altieri, B.; Aussel, H.; Coia, D.; Dannerbauer, H.; Dasyra, K.; Dickinson, M.; Hwang, H. S.; Kartaltepe, J.; Leiton, R.; Magdis, G.; Magnelli, B.; Popesso, P.; Valtchanov, I.; Bauer, F. E.; Brandt, W. N.; Del Moro, A.; Hanish, D. J.; Ivison, R. J.; Juneau, S.; Luo, B.; Lutz, D.; Sargent, M. T.; Scott, D.; Xue, Y. Q.
    We present a study of the infrared properties of X-ray selected, moderate-luminosity (i.e. L-X = 10(42)-10(44) erg s(-1)) active galactic nuclei (AGNs) up to z approximate to 3, in order to explore the links between star formation in galaxies and accretion on to their central black holes. We use 100 and 160 mu m fluxes from GOODS-Herschel - the deepest survey yet undertaken by the Herschel telescope - and show that in the vast majority of cases (i.e. > 94 per cent) these fluxes are dominated by emission from the host galaxy. As such, these far-infrared bands provide an uncontaminated view of star formation in the AGN host galaxies. We find no evidence of any correlation between the X-ray and infrared luminosities of moderate AGNs at any redshift, suggesting that global star formation is decoupled from nuclear (i.e. AGN) activity in these galaxies. On the other hand, we confirm that the star formation rates of AGN hosts increase strongly with redshift, by a factor of 43(-18)(+27) from z < 0.1 to z = 2-3 for AGNs with the same range of X-ray luminosities. This increase is entirely consistent with the factor of 25-50 increase in the specific star formation rates (SSFRs) of normal, star-forming (i.e. main-sequence) galaxies over the same redshift range. Indeed, the average SSFRs of AGN hosts are only marginally (i.e. approximate to 20 per cent) lower than those of main-sequence galaxies at all surveyed redshifts, with this small deficit being due to a fraction of AGNs residing in quiescent (i.e. low SSFR) galaxies. We estimate that 79 +/- 10 per cent of moderate-luminosity AGNs are hosted in main-sequence galaxies, 15 +/- 7 per cent in quiescent galaxies and < 10 per cent in strongly starbursting galaxies. We derive the fractions of all main-sequence galaxies at z < 2 that are experiencing a period of moderate nuclear activity, noting that it is strongly dependent on galaxy stellar mass (M-stars), rising from just a few per cent at M-stars similar to 10(10) M-circle dot to greater than or similar to 20 per cent at M-stars >= 10(11) M-circle dot. Our results indicate that it is galaxy stellar mass that is most important in dictating whether a galaxy hosts a moderate-luminosity AGN. We argue that the majority of moderate nuclear activity is fuelled by internal mechanisms rather than violent mergers, which suggests that high-redshift disc instabilities could be an important AGN feeding mechanism.
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    Hard X-Ray-selected AGNs in Low-mass Galaxies from the NuSTAR Serendipitous Survey
    (2017) Chen, C. T. J.; Brandt, W. N.; Reines, A. E.; Lansbury, G.; Stern, D.; Alexander, D. M.; Bauer, Franz Erik; Ricci, Claudio; Del Moro, A.; Gandhi, P.; Harrison, F. A.; Hickox, R. C.; Koss, M. J.; Lanz, L.; Koss, M. J.; Lanz, L.; Luo, B.; Ricci, Claudio
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    Luminous and Obscured Quasars and Their Host Galaxies
    (2018) Del Moro, A.; Alexander, D.M.; Bauer, Franz Erik; Daddi, E.; Kocevski, D.D.; Stanley, F.; McIntosh, D.H.
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    Mid-infrared luminous quasars in the GOODS–Herschel fields: a large population of heavily obscured, Compton-thick quasars at z ≈ 2
    (2016) Del Moro, A.; Alexander, D. M.; Bauer, Franz Erik; Daddi, E.; Kocevski, D. D.; McIntosh, D. H.; Stanley, F.; Brandt, W. N.; Elbaz, D.; Harrison, C. M.; Luo, B.; Mullaney, J. R.; Xue, Y. Q.
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    NuSTAR J033202-2746.8: Direct Constraints on the Compton Reflection in a Heavily Obscured Quasar at z ≈ 2.
    (2014) Del Moro, A.; Bauer, Franz Erik; Treister, Ezequiel; Mullaney, J. R.; Alexander, D. M.; Comastri, A.; Stern, D.; Civano, F.; Ranalli, P.; Vignali, C.; Aird, J. A.
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    NuSTAR observations of four nearby X-ray faint AGNs: low luminosity or heavy obscuration?
    (OUP, 2020) Annuar, A.; Alexander, D. M.; Gandhi, P.; Lansbury, G. B.; Asmus, D.; Balokovic, M.; Ballantyne, D. R.; Bauer, Franz Erik; Boorman, P. G.; Brandt, W. N.; Brightman, M.; Chen, C. T. J.; Del Moro, A.; Farrah, D.; Harrison, F. A.; Koss, M. J.; Lanz, L.; Marchesi, S.; Masini, A.; Nardini, E.; Ricci, Claudio; Stern, D.; Zappacosta, L.
    We present NuSTAR (Nuclear Spectroscopic Telescope Array) observations of four active galactic nuclei (AGNs) located within 15 Mpc. These AGNs, namely ESO 121-G6, NGC 660, NGC 3486, and NGC 5195, have observed X-ray luminosities of L 2–10 keV,obs ≲ 10 39 erg s −1 , classifying them as low-luminosity AGN (LLAGN). We perform broad-band X-ray spectral analysis for the AGN by combining our NuSTAR data with Chandra or XMM–Newton observations to directly measure their column densities (N H ) and infer their intrinsic power. We complement our X-ray data with archival and new high-angular resolution mid-infrared (mid-IR) data for all objects, except NGC 5195. Based on our X-ray spectral analysis, we found that both ESO 121-G6 and NGC 660 are heavily obscured (N H > 10 23 cm −2 ; L 2–10 keV,int ∼ 10 41 erg s −1 ), and NGC 660 may be Compton thick. We also note that the X-ray flux and spectral slope for ESO 121-G6 have significantly changed over the last decade, indicating significant changes in the obscuration and potentially accretion rate. On the other hand, NGC 3486 and NGC 5195 appear to be unobscured and just mildly obscured, respectively, with L 2–10 keV,int < 10 39 erg s −1 , i.e. genuine LLAGN. Both of the heavily obscured AGNs have L bol > 10 41 erg s −1 and λ Edd ≳ 10 −3 , and are detected in high-angular resolution mid-IR imaging, indicating the presence of obscuring dust on nuclear scale. NGC 3486, however, is undetected in high-resolution mid-IR imaging, and the current data do not provide stringent constraints on the presence or absence of obscuring nuclear dust in the AGN.
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    NuSTAR observations of heavily obscured quasars at z 0.5
    (2014) Lansbury, G.B.; Alexander, D.M.; Del Moro, A.; Gandhi, P.; Assef, R.J.; Stern, D.; Aird, J.; Ballantyne, D.R.; Balokovic, M.; Bauer, Franz Erik
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    NuStar observations of the compton-thick active galactic nucleus and ultraluminous X-Ray source candidate in NGC 5643
    (2015) Annuar, A.; Gandhi, P.; Alexander, D.; Lansbury, G.; Arévalo, P.; Ballantyne, D.; Balokovic, M.; Boggs, S.; Brandt, W.; Brightman, M.; Christensen, F.; Craig, W.; Del Moro, A.; Hailey, C.; Harrison, F.; Bauer, Franz Erik
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    NuStar spectroscopy of multiI-component X-Ray reflection from NGC 1068
    (2015) Bauer, Franz Erik; Arévalo, P.; Walton, D.; Koss, M.; Puccetti, S.; Gandhi, P.; Stern, D.; Alexander, D.; Balokovic, M.; Boggs, S.; Brandt, W.; Brightman, M.; Christensen, F.; Comastri, A.; Craig, W.; Del Moro, A.
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    SPIDERS: selection of spectroscopic targets using AGN candidates detected in all-sky X-ray surveys
    (OXFORD UNIV PRESS, 2017) Dwelly, T.; Salvato, M.; Merloni, A.; Brusa, M.; Buchner, J.; Anderson, S. F.; Boller, Th.; Brandt, W. N.; Budavari, T.; Clerc, N.; Coffey, D.; Del Moro, A.; Georgakakis, A.; Green, P. J.; Jin, C.; Menzel, M. L.; Myers, A. D.; Nandra, K.; Nichol, R. C.; Ridl, J.; Schwope, A. D.; Simm, T.
    SPIDERS (SPectroscopic IDentification of eROSITA Sources) is a Sloan Digital Sky Survey IV (SDSS-IV) survey running in parallel to the Extended Baryon Oscillation Spectroscopic Survey (eBOSS) cosmology project. SPIDERS will obtain optical spectroscopy for large numbers of X-ray-selected active galactic nuclei (AGN) and galaxy cluster members detected in wide-area eROSITA, XMM-Newton and ROSAT surveys. We describe the methods used to choose spectroscopic targets for two sub-programmes of SPIDERS X-ray selected AGN candidates detected in the ROSAT All Sky and the XMM-Newton Slew surveys. We have exploited a Bayesian cross-matching algorithm, guided by priors based on mid-IR colourmagnitude information from the Wide-field Infrared Survey Explorer survey, to select the most probable optical counterpart to each X-ray detection. We empirically demonstrate the high fidelity of our counterpart selection method using a reference sample of bright welllocalized X-ray sources collated from XMM-Newton, Chandra and Swift-XRT serendipitous catalogues, and also by examining blank-sky locations. We describe the down-selection steps which resulted in the final set of SPIDERS-AGN targets put forward for spectroscopy within the eBOSS/TDSS/SPIDERS survey, and present catalogues of these targets. We also present catalogues of similar to 12 000 ROSAT and similar to 1500 XMM-Newton Slew survey sources that have existing optical spectroscopy from SDSS-DR12, including the results of our visual inspections. On completion of the SPIDERS programme, we expect to have collected homogeneous spectroscopic redshift information over a footprint of similar to 7500 deg(2) for > 85 per cent of the ROSAT and XMM-Newton Slew survey sources having optical counterparts in the magnitude range 17 < r < 22.5, producing a large and highly complete sample of bright X-ray-selected AGN suitable for statistical studies of AGN evolution and clustering.
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    THE NuSTAR EXTRAGALACTIC SURVEY: A FIRST SENSITIVE LOOK AT THE HIGH-ENERGY COSMIC X-RAY BACKGROUND POPULATION
    (2013) Alexander, D. M.; Stern, D.; Del Moro, A.; Lansbury, G. B.; Assef, R. J.; Aird, J.; Ajello, M.; Ballantyne, D. R.; Bauer, F. E.; Boggs, S. E.; Brandt, W. N.; Christensen, F. E.; Civano, F.; Comastri, A.; Craig, W. W.; Elvis, M.; Grefenstette, B. W.; Hailey, C. J.; Harrison, F. A.; Hickox, R. C.; Luo, B.; Madsen, K. K.; Mullaney, J. R.; Perri, M.; Puccetti, S.; Saez, C.; Treister, E.; Urry, C. M.; Zhang, W. W.; Bridge, C. R.; Eisenhardt, P. R. M.; Gonzalez, A. H.; Miller, S. H.; Tsai, C. W.
    We report on the first 10 identifications of sources serendipitously detected by the Nuclear Spectroscopic Telescope Array (NuSTAR) to provide the first sensitive census of the cosmic X-ray background source population at greater than or similar to 10 keV. We find that these NuSTAR-detected sources are approximate to 100 times fainter than those previously detected at greater than or similar to 10 keV and have a broad range in redshift and luminosity (z = 0.020-2.923 and L10-40 keV approximate to 4 x 10(41)-5 x 10(45) erg s(-1)); the median redshift and luminosity are z approximate to 0.7 and L10-40 keV approximate to 3 x 10(44) erg s(-1), respectively. We characterize these sources on the basis of broad-band approximate to 0.5-32 keV spectroscopy, optical spectroscopy, and broad-band ultraviolet-to-mid-infrared spectral energy distribution analyses. We find that the dominant source population is quasars with L10-40 keV > 10(44) erg s(-1), of which approximate to 50% are obscured with N-H greater than or similar to 10(22) cm(-2). However, none of the 10 NuSTAR sources are Compton thick (N-H greater than or similar to 10(24) cm(-2)) and we place a 90% confidence upper limit on the fraction of Compton-thick quasars (L10-40 keV > 10(44) erg s(-1)) selected at greater than or similar to 10 keV of less than or similar to 33% over the redshift range z = 0.5-1.1. We jointly fitted the rest-frame approximate to 10-40 keV data for all of the non-beamed sources with L10-40 keV > 10(43) erg s(-1) to constrain the average strength of reflection; we find R < 1.4 for Gamma = 1.8, broadly consistent with that found for local active galactic nuclei (AGNs) observed at greater than or similar to 10 keV. We also constrain the host-galaxy masses and find a median stellar mass of approximate to 10(11) M-circle dot, a factor approximate to 5 times higher than the median stellar mass of nearby high-energy selected AGNs, which may be at least partially driven by the order of magnitude higher X-ray luminosities of the NuSTAR sources. Within the low source-statistic limitations of our study, our results suggest that the overall properties of the NuSTAR sources are broadly similar to those of nearby high-energy selected AGNs but scaled up in luminosity and mass.
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    The NuSTAR Extragalactic Survey: Average Broadband X-Ray Spectral Properties of the NuSTAR-detected AGNs
    (2017) Del Moro, A.; Bauer, Franz Erik; Treister, Ezequiel; Ricci, Claudio; Alexander, D. M.; Aird, J. A.; Civano, Francesca; Mullaney, J.; Ballantyne, D. R.; Brandt, W N.; Comastri, A.
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    The NuSTAR Extragalactic Surveys: Initial Results and Catalog from the Extended Chandra Deep Field South
    (2015) Mullaney, J.; Bauer, Franz Erik; Treister, Ezequiel; Del Moro, A.; Aird, J. A.; Alexander, D. M.; Civano, Francesca; Hickox, R. C.; Lansbury, George B.; Ajello, Marco; Assef, R.
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    The NuSTAR Extragalactic Surveys: X-Ray Spectroscopic Analysis of the Bright Hard-band Selected Sample
    (2018) Zappacosta, L.; Ricci, Claudio; Treister, Ezequiel; Comastri, A.; Civano, Francesca; Puccetti, S.; Fiore, F.; Aird, J. A.; Del Moro, A.; Lansbury, George B.; Lanzuisi, G.
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    The NuSTAR Serendipitous Survey: The 40-month Catalog and the Properties of the Distant High-energy X-Ray Source Population
    (2017) Lansbury, George B.; Treister, Ezequiel; Bauer, Franz Erik; Stern, Daniel.; Aird, J. A.; Alexander, D. M.; Fuentes, C.; Harrison, F. A.; Tomsick, J. A.; Baloković, M.; Del Moro, A.
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    X-Ray Bolometric Corrections for Compton-thick Active Galactic Nuclei
    (2017) Brightman, M.; Balokovic, M.; Ballantyne, D. R.; Bauer, Franz Erik; Boorman, P.; Buchner, J.; Brandt, W. N.; Comastri, A.; Del Moro, A.; Ricci, Claudio