Browsing by Author "Weigel, Anna K."

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    BAT AGN Spectroscopic Survey - XIII. The nature of the most luminous obscured AGN in the low-redshift universe
    (2019) Bar, Rudolf E.; Trakhtenbrot, Benny; Oh, Kyuseok; Koss, Michael J.; Wong, Ivy; Ricci, Claudio; Schawinski, Kevin; Weigel, Anna K.; Sartori, Lia F.; Ichikawa, Kohei; Secrest, Nathan J.; Stern, Daniel; Pacucci, Fabio; Mushotzky, Richard; Powell, Meredith C.; Ricci, Federica; Sani, Eleonora; Smith, Krista L.; Harrison, Fiona A.; Lamperti, Isabella; Urry, C. Megan
    We present a multiwavelength analysis of 28 of the most luminous low-redshift narrow-line, ultra-hard X-ray-selected active galactic nuclei (AGN) drawn from the 70-month Swift/BAT all-sky survey, with bolometric luminosities of log(L-bol/erg s(-1)) greater than or similar to 45.25. The broad goal of our study is to determine whether these objects have any distinctive properties, potentially setting them aside from lower luminosity obscured AGN in the local Universe. Our analysis relies on the first data release of the BAT AGN Spectroscopic Survey (BASS/DR1) and on dedicated observations with the VLT, Palomar, and Keck observatories. We find that the vast majority of our sources agree with commonly used AGN selection criteria which are based on emission line ratios and on mid-infrared colours. Our AGN are pre-dominantly hosted in massive galaxies (9.8 less than or similar to log (M-*/M-circle dot) less than or similar to 11.7); based on visual inspection of archival optical images, they appear to be mostly ellipticals. Otherwise, they do not have distinctive properties. Their radio luminosities, determined from publicly available survey data, show a large spread of almost four orders of magnitude- much broader than what is found for lower X-ray luminosity obscured AGN in BASS. Moreover, our sample shows no preferred combination of black hole masses (M-BH) and/or Eddington ratio (lambda(Edd)), covering 7.5 less than or similar to log (M-BH/M-circle dot) less than or similar to 10.3 and 0.01 less than or similar to lambda(Edd) less than or similar to 1. Based on the distribution of our sources in the lambda(Edd)-N-H plane, we conclude that our sample is consistent with a scenario where the amount of obscuring material along the line of sight is determined by radiation pressure exerted by the AGN on the dusty circumnuclear gas.
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    Probing the Structure and Evolution of BASS Active Galactic Nuclei through Eddington Ratios
    (2022) Ananna, Tonima Tasnim; Urry, C. Megan; Ricci, Claudio; Natarajan, Priyamvada; Hickox, Ryan C.; Trakhtenbrot, Benny; Treister, Ezequiel; Weigel, Anna K.; Ueda, Yoshihiro; Koss, Michael J.; Bauer, F. E.; Temple, Matthew J.; Balokovic, Mislav; Mushotzky, Richard; Auge, Connor; Sanders, David B.; Kakkad, Darshan; Sartori, Lia F.; Marchesi, Stefano; Harrison, Fiona; Stern, Daniel; Oh, Kyuseok; Caglar, Turgay; Powell, Meredith C.; Podjed, Stephanie A.; Mejia-Restrepo, Julian E.
    We constrain the intrinsic Eddington ratio (lambda(Edd)) distribution function for local active galactic nuclei (AGN) in bins of low and high obscuration [log(N-H/cm(-2)) <= 22 and 22 < log(N-H/cm(-2)) < 25], using the Swift Burst Alert Telescope 70 month/BASS DR2 survey. We interpret the fraction of obscured AGN in terms of circumnuclear geometry and temporal evolution. Specifically, at low Eddington ratios (log lambda(Edd) < -2), obscured AGN outnumber unobscured ones by a factor of similar to 4, reflecting the covering factor of the circumnuclear material (0.8, or a torus opening angle of similar to 34 degrees). At high Eddington ratios (log lambda(Edd) > - 1), the trend is reversed, with <30% of AGN having log(N-H/cm(-2)) > 22, which we suggest is mainly due to the small fraction of time spent in a highly obscured state. Considering the Eddington ratio distribution function of narrow-line and broad-line AGN from our prior work, we see a qualitatively similar picture. To disentangle temporal and geometric effects at high lambda(Edd), we explore plausible clearing scenarios such that the time-weighted covering factors agree with the observed population ratio. We find that the low fraction of obscured AGN at high lambda(Edd) is primarily due to the fact that the covering factor drops very rapidly, with more than half the time spent with <10% covering factor. We also find that nearly all obscured AGN at high-lambda(Edd) exhibit some broad lines. We suggest that this is because the height of the depleted torus falls below the height of the broad-line region, making the latter visible from all lines of sight.
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    The close environments of accreting massive black holes are shaped by radiative feedback.
    (2017) Ricci, Claudio; Treister, Ezequiel; Trakhtenbrot, Benny; Koss, M.; Ueda, Yoshihiro; Schawinski, Kevin; Oh, Kyuseok; Lamperti, Isabella; Mushotzky, Richard; Ho, Luis C.; Weigel, Anna K.
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    The fraction of AGNs in major merger galaxies and its luminosity dependence.
    (2018) Weigel, Anna K.; Treister, Ezequiel; Schawinski, Kevin; Trakhtenbrot, Benny; Sanders, David B.
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    The systematic search for z ≳ 5 active galactic nuclei in the Chandra Deep Field South.
    (2015) Weigel, Anna K.; Treister, Ezequiel; Schawinski, Kevin; Urry, C. Megan; Koss, M.; Trakhtenbrot, Benny