Browsing by Author "Powell, M. C."

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    BASS. XXXIII. Swift-BAT Blazars and Their Jets through Cosmic Time
    (2022) Marcotulli, L.; Ajello, M.; Urry, C. M.; Paliya, V. S.; Koss, M.; Oh, K.; Madejski, G.; Ueda, Y.; Balokovic, M.; Trakhtenbrot, B.; Ricci, F.; Ricci, C.; Stern, D.; Harrison, F.; Powell, M. C.
    We derive the most up-to-date Swift-Burst Alert Telescope (BAT) blazar luminosity function in the 14-195 keV range, making use of a clean sample of 118 blazars detected in the BAT 105 month survey catalog, with newly obtained redshifts from the BAT Active Galatic Nucleus Spectroscopic Survey. We determine the best-fit X-ray luminosity function for the whole blazar population, as well as for flat-spectrum radio quasars (FSRQs) alone. The main results are: (1) at any redshift, BAT detects the most luminous blazars, above any possible break in their luminosity distribution, which means we cannot differentiate between density and luminosity evolution; (2) the whole blazar population, dominated by FSRQs, evolves positively up to redshift z similar to 4.3, confirming earlier results and implying lower number densities of blazars at higher redshifts than previously estimated. The contribution of this source class to the cosmic X-ray background at 14-195 keV can range from 5%-18%, while possibly accounting for 100% of the MeV background. We also derived the average 14 keV-10 GeV spectral energy distribution for BAT blazars, which allows us to predict the number counts of sources in the MeV range, as well as the expected number of high-energy (>100 TeV) neutrinos. A mission like COSI will detect 40 MeV blazars, of which two may have coincident neutrino detections. Finally, taking into account beaming selection effects, the distribution and properties of the parent population of these extragalactic jets are derived. We find that the distribution of viewing angles is quite narrow, with most sources aligned within <5 degrees of the line of sight. Moreover, the average Lorentz factor, Gamma = 8-12, is lower than previously suggested for these powerful sources.
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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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    BAT AGN spectroscopic survey – XV: the high frequency radio cores of ultra-hard X-ray selected AGN
    (OUP, 2019) Smith, K. L.; Mushotzky, R. F.; Koss, M.; Trakhtenbrot, B.; Ricci, Claudio; Wong, O. I.; Bauer, F. E.; Ricci, F.; Vogel, S.; Stern, D.; Powell, M. C.; Urry, C. M.; Harrison, F.; Mejia-Restrepo, J.; Oh, K.; Baek, J.; Chun, A.
    We have conducted 22 GHz radio imaging at 1 arcsec resolution of 100 low-redshift AGN selected at 14–195 keV by the Swift-BAT. We find a radio core detection fraction of 96 per cent, much higher than lower frequency radio surveys. Of the 96 radio-detected AGN, 55 have compact morphologies, 30 have morphologies consistent with nuclear star formation, and 11 have sub-kpc to kpc-scale jets. We find that the total radio power does not distinguish between nuclear star formation and jets as the origin of the radio emission. For 87 objects, we use optical spectroscopy to test whether AGN physical parameters are distinct between radio morphological types. We find that X-ray luminosities tend to be higher if the 22 GHz morphology is jet-like, but find no significant difference in other physical parameters. We find that the relationship between the X-ray and core radio luminosities is consistent with the LR/LX ∼ 10−5 of coronally active stars. We further find that the canonical fundamental planes of black hole activity systematically overpredict our radio luminosities, particularly for objects with star formation morphologies.
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    The Swift/BAT AGN Spectroscopic Survey. IX. The Clustering Environments of an Unbiased Sample of Local agns
    (2018) Powell, M. C.; Cappelluti, N.; Urry, C. M.; Koss, M.; Finoguenov, A.; Ricci, Claudio; Trakhtenbrot, B.; Allevato, V.; Ajello, M.; Oh, K.; Schawinski, K.; Secrest, N.