Browsing by Author "Zappacosta, L."

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    BAT AGN Spectroscopic Survey XXVII: scattered X-Ray radiation in obscured active galactic nuclei
    (2021) Gupta, K. K.; Ricci, C.; Tortosa, A.; Ueda, Y.; Kawamuro, T.; Koss, M.; Trakhtenbrot, B.; Oh, K.; Bauer, F. E.; Ricci, F.; Privon, G. C.; Zappacosta, L.; Stern, D.; Kakkad, D.; Piconcelli, E.; Veilleux, S.; Mushotzky, R.; Caglar, T.; Ichikawa, K.; Elagali, A.; Powell, M. C.; Urry, C. M.; Harrison, F.
    Accreting supermassive black holes (SMBHs), also known as active galactic nuclei (AGN), are generally surrounded by large amounts of gas and dust. This surrounding material reprocesses the primary X-ray emission produced close to the SMBH and gives rise to several components in the broadband X-ray spectra of AGN, including a power-law possibly associated with Thomson-scattered radiation. In this work, we study the properties of this scattered component for a sample of 386 hard-X-ray-selected, nearby (z similar to 0.03) obscured AGN from the 70-month Swift/BAT catalogue. We investigate how the fraction of Thomson-scattered radiation correlates with different physical properties of AGN, such as line-of-sight column density, X-ray luminosity, black hole mass, and Eddington ratio. We find a significant negative correlation between the scattering fraction and the column density. Based on a large number of spectral simulations, we exclude the possibility that this anticorrelation is due to degeneracies between the parameters. The negative correlation also persists when considering different ranges of luminosity, black hole mass, and Eddington ratio. We discuss how this correlation might be either due to the angle dependence of the Thomson cross-section or to more obscured sources having a higher covering factor of the torus. We also find a positive correlation between the scattering fraction and the ratio of [OIII] lambda 5007 to X-ray luminosity. This result is consistent with previous studies and suggests that the Thomson-scattered component is associated with the narrow-line region.
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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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    The Nustar Extragalactic Surveys: Overview and Catalog from the COSMOS Field
    (2015) Civano, Francesca; Bauer, Franz Erik; Luo, B.; Saez, C.; Treister, Ezequiel; Hickox, R. C.; Puccetti, S.; Comastri, A.; Mullaney, J.; Zappacosta, L.; LaMassa, Stephanie M.
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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 WISSH quasars project : IX. Cold gas content and environment of luminous QSOs at z ∼2.4-4.7
    (2021) Bischetti, M.; Feruglio, C.; Piconcelli, E.; Duras, F.; Perez-Torres, M.; Herrero, R.; Venturi, Giacomo; Carniani, S.; Bruni, G.; Gavignaud, I.; Testa, V.; Bongiorno, A.; Brusa, M.; Circosta, C.; Cresci, G.; D'Odorico, V.; Maiolino, R.; Marconi, A.; Mingozzi, M.; Pappalardo, C.; Perna, M.; Traianou, E.; Travascio, A.; Vietri, G.; Zappacosta, L.; Fiore, F.