Browsing by Author "Ueda, Y."
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- ItemA hard X-ray view of luminous and ultra-luminous infrared galaxies in GOALS - I. AGN obscuration along the merger sequence(2021) Ricci, C.; Privon, G. C.; Pfeifle, R. W.; Armus, L.; Iwasawa, K.; Torres-Albà, N.; Satyapal, S.; Bauer, F. E.; Treister, E.; Ho, L. C.; Aalto, S.; Arévalo, P.; Barcos-Muñoz, L.; Charmandaris, V.; Diaz-Santos, T.; Evans, A. S.; Gao, T.; Inami, H.; Koss, M. J.; Lansbury, G.; Linden, S. T.; Medling, A.; Sanders, D. B.; Song, Y.; Stern, D.; U, V.; Ueda, Y.; Yamada, S.The merger of two or more galaxies can enhance the inflow of material from galactic scales into the close environments of active galactic nuclei (AGNs), obscuring and feeding the supermassive black hole (SMBH). Both recent simulations and observations of AGN in mergers have confirmed that mergers are related to strong nuclear obscuration. However, it is still unclear how AGN obscuration evolves in the last phases of the merger process. We study a sample of 60 luminous and ultra-luminous IR galaxies (U/LIRGs) from the GOALS sample observed by NuSTAR. We find that the fraction of AGNs that are Compton thick (CT;N-H >= 10(24)cm(-2) ) peaks at at a late merger stage, prior to coalescence, when the nuclei have projected separations (d(sep)) of 0.4-6 kpc. A similar peak is also observed in the median N-H [[(1.6 +/- 0.5) x 10(24) cm(-2)].]. The vast majority (85(-9)(+7) per cent)) of the AGNs in the final merger stages (d(sep) less than or similar to 10 kpc) are heavily obscured (N-H = 10(23) cm(-2)), and the median N-H of the accreting SMBHs in our sample is systematically higher than that of local hard X-ray-selected AGN, regardless of the merger stage. This implies that these objects have very obscured nuclear environments, with the gas almost completely covering the AGN in late mergers. CT AGNs tend to have systematically higher absorption-corrected X-ray luminosities than less obscured sources. This could either be due to an evolutionary effect, with more obscured sources accreting more rapidly because they have more gas available in their surroundings, or to a selection bias. The latter scenario would imply that we are still missing a large fraction of heavily obscured, lower luminosity (L2-10 less than or similar to 10(43) erg s(-1)) AGNs in U/LIRGs.
- ItemA statistical relation between the X-ray spectral index and Eddington ratio of active galactic nuclei in deep surveys.(2013) Brightman, M.; Treister, Ezequiel; Silverman, J. D.; Mainieri, V.; Ueda, Y.; Schramm, M.; Matsuoka, K.; Nagao, T.; Steinhardt C. L.; Kartaltepe, J.
- ItemBASS XXXVII: The Role of Radiative Feedback in the Growth and Obscuration Properties of Nearby Supermassive Black Holes(2022) Ricci, C.; Ananna, T. T.; Temple, M. J.; Urry, C. M.; Koss, M. J.; Trakhtenbrot, B.; Ueda, Y.; Stern, D.; Bauer, F. E.; Treister, E.; Privon, G. C.; Oh, K.; Paltani, S.; Stalevski, M.; Ho, L. C.; Fabian, A. C.; Mushotzky, R.; Chang, C. S.; Ricci, F.; Kakkad, D.; Sartori, L.; Baer, R.; Caglar, T.; Powell, M.; Harrison, F.We study the relation between obscuration and supermassive black hole (SMBH) accretion using a large sample of hard X-ray selected active galactic nuclei (AGNs). We find a strong decrease in the fraction of obscured sources above the Eddington limit for dusty gas (log lambda(Edd) >= -2) confirming earlier results, and consistent with the radiation-regulated unification model. This also explains the difference in the Eddington ratio distribution functions (ERDFs) of type 1 and type 2 AGNs obtained by a recent study. The break in the ERDF of nearby AGNs is at log lambda*(Edd) = -1.34 +/- 0.07. This corresponds to the lambda(Edd) where AGNs transition from having most of their sky covered by obscuring material to being mostly devoid of absorbing material. A similar trend is observed for the luminosity function, which implies that most of the SMBH growth in the local universe happens when the AGN is covered by a large reservoir of gas and dust. These results could be explained with a radiation-regulated growth model, in which AGNs move in the N-H-lambda(Edd) plane during their life cycle. The growth episode starts with the AGN mostly unobscured and accreting at low lambda(Edd). As the SMBH is further fueled, lambda(Edd), N-H and the covering factor increase, leading the AGN to be preferentially observed as obscured. Once lambda(Edd) reaches the Eddington limit for dusty gas, the covering factor and N-H rapidly decrease, leading the AGN to be typically observed as unobscured. As the remaining fuel is depleted, the SMBH goes back into a quiescent phase.
- ItemBASS. XLII. The Relation between the Covering Factor of Dusty Gas and the Eddington Ratio in Nearby Active Galactic NucleiRicci, C.; Ichikawa, K.; Stalevski, M.; Kawamuro, T.; Yamada, S.; Ueda, Y.; Mushotzky, R.; Privon, G. C.; Koss, M. J.; Trakhtenbrot, B.; Fabian, A. C.; Ho, L. C.; Asmus, D.; Bauer, Franz Erik; Chang, C. S.; Gupta, K. K.; Oh, K.; Powell, M.; Pfeifle, R. W.; Rojas, A.; Ricci, F.; Temple, M. J.; Toba, Y.; Tortosa, A.; Treister, Ezequiel; Harrison, F.; Stern, D.; Urry, C. M.Accreting supermassive black holes (SMBHs) located at the centers of galaxies are typically surrounded by large quantities of gas and dust. The structure and evolution of this circumnuclear material can be studied at different wavelengths, from the submillimeter to the X-ray. Recent X-ray studies have shown that the covering factor of the obscuring material tends to decrease with increasing Eddington ratio, likely due to radiative feedback on dusty gas. Here we study a sample of 549 nearby (z less than or similar to 0.1) hard X-ray (14-195 keV) selected nonblazar active galactic nuclei (AGN) and use the ratio between the AGN infrared and bolometric luminosity as a proxy of the covering factor. We find that, in agreement with what has been found by X-ray studies of the same sample, the covering factor decreases with increasing Eddington ratio. We also confirm previous findings that showed that obscured AGN typically have larger covering factors than unobscured sources. Finally, we find that the median covering factors of AGN located in different regions of the column density-Eddington ratio diagram are in good agreement with what would be expected from a radiation-regulated growth of SMBHs.
- ItemBASS. 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.
- ItemBAT AGN Spectroscopic Survey - XII. The relation between coronal properties of active galactic nuclei and the Eddington ratio.(2018) Ricci, Claudio; Bauer, Franz Erik; Treister, Ezequiel; Ho, L. C.; Fabian, AC.; Trakhtenbrot, B.; Koss, M.; Ueda, Y.; Lohfink, A.; Shimizu, T.; Mushotzky, R.
- ItemBAT 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.
- ItemCompton-thick accretion in the local universe(2015) Ricci, Claudio; Ueda, Y.; Koss, M.; Trakhtenbrot, B.; Bauer, Franz Erik; Gandhi, P.
- Item[O iii] lambda5007 and X-ray properties of a complete sample of hard X-ray selected AGNs in the local Universe(2015) Ueda, Y.; Hashimoto, Y.; Ichikawa, K.; Ishino, Y.; Kniazev, A.; Vaeisaenen, P.; Ricci, Claudio; Berney, S.; Gandhi, P.; Koss, M.