Browsing by Author "Aird, J."
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- ItemNuSTAR 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
- ItemNuStar reveals extreme absorption in z < 0.5 type 2 quasars(2015) Lansbury, G.; Gandhi, P.; Alexander, D.; Assef, R.; Aird, J.; Annuar, A.; Ballantyne, D.; Balokovic, M.; Bauer, Franz Erik; Boggs, S.; Brandt, W.; Brightman, M.; Christensen, F.; Civano, F.; Comastri, A.; Craig, W.
- ItemTHE 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.
- ItemThe Evolving AGN Duty Cycle in Galaxies Since z ∼ 3 as Encoded in the X-Ray Luminosity Function(2020) Delvecchio, I.; Daddi, E.; Aird, J.; Mullaney, J. R.; Bernhard, E.; Grimmett, L. P.; Carraro, R.; Cimatti, A.; Zamorani, G.; Caplar, N.; Vito, F.; Elbaz, D.; Rodighiero, G.We present a new modeling of the X-ray luminosity function (XLF) of active galactic nuclei (AGNs) out to z similar to 3, dissecting the contributions of main-sequence (MS) and starburst (SB) galaxies. For each galaxy population, we convolved the observed galaxy stellar mass (M-*) function with a grid of M-*- independent Eddington ratio (lambda(EDD)) distributions, normalized via empirical black hole accretion rate (BHAR) to star formation rate (SFR) relations. Our simple approach yields an excellent agreement with the observed XLF since z similar to 3. We find that the redshift evolution of the observed XLF can only be reproduced through an intrinsic flattening of the lambda(EDD) distribution and with a positive shift of the break lambda*, consistent with an antihierarchical behavior. The AGN accretion history is predominantly made by massive (10(10) < M-* < 10(11) M-circle dot) MS galaxies, while SB-driven BH accretion, possibly associated with galaxy mergers, becomes dominant only in bright quasars, at log(L-X/erg s(-1)) > 44.36 + 1.28 x (1 + z). We infer that the probability of finding highly accreting (lambda(EDD) > 10%) AGNs significantly increases with redshift, from 0.4% (3.0%) at z = 0.5%-6.5% (15.3%) at z = 3 for MS (SB) galaxies, implying a longer AGN duty cycle in the early universe. Our results strongly favor a M-*-dependent ratio between BHAR and SFR, as BHAR/SFR proportional to M-*(0.73[+0.22,-0.29]), supporting a nonlinear BH buildup relative to the host. Finally, this framework opens potential questions on super-Eddington BH accretion and different lambda(EDD) prescriptions for understanding the cosmic BH mass assembly.
- ItemThe NuSTAR Extragalactic Survey : First Direct Measurements of the Greater Than Or Similar To 10 Kev X-Ray Luminosity Function For Active Galactic Nuclei At z > 0.1(2015) Aird, J.; Alexander, D. M.; Ballantyne, D. R.; Civano, F.; Moro, A. Del; Hickox, R. C.; Lansbury, G. B.; Mullaney, J. R.; Bauer, Franz Erik; Brandt, W. N.