Browsing by Author "Kakkad, Darshan"
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- ItemBASS XXXII: Studying the Nuclear Millimeter-wave Continuum Emission of AGNs with ALMA at Scales ≲100-200 pc(2022) Kawamuro, Taiki; Ricci, Claudio; Imanishi, Masatoshi; Mushotzky, Richard F.; Izumi, Takuma; Ricci, Federica; Bauer, Franz E.; Koss, Michael J.; Trakhtenbrot, Benny; Ichikawa, Kohei; Rojas, Alejandra F.; Smith, Krista Lynne; Shimizu, Taro; Oh, Kyuseok; den Brok, Jakob S.; Baba, Shunsuke; Balokovic, Mislay; Chang, Chin-Shin; Kakkad, Darshan; Pfeifle, Ryan W.; Privon, George C.; Temple, Matthew J.; Ueda, Yoshihiro; Harrison, Fiona; Powell, Meredith C.; Stern, Daniel; Urry, Meg; Sanders, David B.To understand the origin of nuclear (less than or similar to 100 pc) millimeter-wave (mm-wave) continuum emission in active galactic nuclei (AGNs), we systematically analyzed subarcsecond resolution Band-6 (211-275 GHz) Atacama Large Millimeter/submillimeter Array data of 98 nearby AGNs (z < 0.05) from the 70 month Swift/BAT catalog. The sample, almost unbiased for obscured systems, provides the largest number of AGNs to date with high mm-wave spatial resolution sampling (similar to 1-200 pc), and spans broad ranges of 14-150 keV luminosity {40< log [L-14(-150)/(erg s(-1))] < 45}, black hole mass [5 < log(M-BH/M-circle dot) < 10], and Eddington ratio (-4 < log lambda(Edd) < 2). We find a significant correlation between 1.3 mm (230 GHz) and 14-150 keV luminosities. Its scatter is approximate to 0.36 dex, and the mm-wave emission may serve as a good proxy of the AGN luminosity, free of dust extinction up to N-H similar to 10(26) CM-2. While the mm-wave emission could be self-absorbed synchrotron radiation around the X-ray corona according to past works, we also discuss different possible origins of the mm-wave emission: AGN-related dust emission, outflow-driven shocks, and a small-scale (<200 pc) jet. The dust emission is unlikely to be dominant, as the mm-wave slope is generally flatter than expected. Also, due to no increase in the mm-wave luminosity with the Eddington ratio, a radiation-driven outflow model is possibly not the common mechanism Furthermore, we find independence of the mm-wave luminosity on indicators of the inclination angle from the polar axis of the nuclear structure, which is inconsistent with a jet model whose luminosity depends only on the angle.
- ItemBASS. LIII. The Eddington Ratio as the Primary Regulator of the Fraction of X-Ray Emission in Active Galactic Nuclei(2025) Gupta, Kriti Kamal; Ricci, Claudio; Tortosa, Alessia; Temple, Matthew J.; Koss, Michael J.; Trakhtenbrot, Benny; Bauer, Franz E.; Treister, Ezequiel; Mushotzky, Richard; Kammoun, Elias; Papadakis, Iossif; Oh, Kyuseok; Rojas, Alejandra; Chang, Chin-Shin; Diaz, Yaherlyn; Jana, Arghajit; Kakkad, Darshan; Moral Castro, Ignacio del; Peca, Alessandro; Powell, Meredith C.; Stern, Daniel; Urry, C. Megan; Harrison, FionaActive galactic nuclei (AGN) emit radiation via accretion across the entire energy spectrum. While the standard disk and corona model can somewhat describe this emission, it fails to predict specific features such as the soft X-ray excess, the short-term optical/UV variability, and the observed UV/X-ray correlation in AGN. In this context, the fraction of AGN emission in different bands (i.e., bolometric corrections) can be useful to better understand the accretion physics of AGN. Past studies have shown that the X-ray bolometric corrections are strongly dependent on the physical properties of AGN, such as their luminosities and Eddington ratios. However, since these two parameters depend on each other, it has been unclear which is the main driver of the X-ray bolometric corrections. We present here results from a large study of hard-X-ray-selected (14–195 keV) nearby (z < 0.1) AGN. Based on our systematic analysis of the simultaneous optical-to-X-ray spectral energy distributions of 236 unobscured AGN, we found that the primary parameter controlling the X-ray bolometric corrections is the Eddington ratio. Our results show that, while the X-ray bolometric correction increases with the bolometric luminosity for sources with intermediate Eddington ratios (0.01–1), this dependence vanishes for sources with lower Eddington ratios (<0.01). This could be used as evidence for a change in the accretion physics of AGN at low Eddington ratios.
- ItemBASS. XLIX. Characterization of Highly Luminous and Obscured AGNs: Local X-Ray and [Ne V]λ3426 Emission in Comparison with the High-redshift Universe(2025) Peca, Alessandro; Koss, Michael J.; Oh, Kyuseok; Ricci, Claudio; Trakhtenbrot, Benny; Mushotzky, Richard; Treister, Ezequiel; Urry, C. Megan; Pizzetti, Andrealuna; Ichikawa, Kohei; Tortosa, Alessia; Ricci, Federica; Signorini, Matilde; Kakkad, Darshan; Chang, Chin-Shin; Mazzolari, Giovanni; Caglar, Turgay; Magno, Macon; Moral Castro, Ignacio del; Boorman, Peter G.; Ananna, Tonima T.; Harrison, Fiona; Stern, Daniel; Sanders, DavidWe present a detailed analysis of the most luminous and obscured active galactic nuclei (AGNs) detected in the ultra-hard X-ray band (14–195 kev) by the Swift/Burst Alert Telescope. Our sample comprises 21 X-ray luminous (log LX/erg s > 44.6 1 , 2–10 keV) AGNs at z < 0.6, optically classified as Seyfert 1.9 and 2. Using NuSTAR, XMM-Newton, Suzaku, and Chandra data, we constrain AGN properties such as absorption column density NH, photon index Γ, intrinsic LX, covering factor, and iron Kα equivalent width. We find median line-ofsight / = + logNH cm 23.5 2 1.2 0.5 and 2–10 keV rest-frame, de-absorbed / = + log LX erg s 44.7 1 0.6 0.8, at the 5th and 95th percentiles. For sources with black hole mass estimates (12/20), we find a weak correlation between Γ and Eddington ratio (λEdd). Of these, six (50% ± 13%) lie in the NH-λEdd “forbidden region” and exhibit a combined higher prevalence of NH variability and outflow signatures, suggesting a transitional phase where AGN feedback may be clearing the obscuring material. For the 13/21 sources with multi-epoch X-ray spectroscopy, + 85 1 5 5% exhibit variability in either 2–10 keV flux (+ 77 1 8 5%) or line-of-sight NH (+ 33 1 1 0 5% ). For the 20/21 sources with available near-UV/optical spectroscopy, we detect [Ne v]λ3426 in 17 (+ 85 11 5 %), confirming its reliability to probe AGN emission even in heavily obscured systems. When renormalized to the same [O III]λ5007 peak flux as z = 2 −9 narrow-line AGNs identified with JWST, our sample exhibits significantly stronger [Ne v]λ3426 emission, suggesting that high-redshift obscured AGNs may be intrinsically weaker in [Ne v]λ3426 or that [Ne v]λ3426 is more challenging to detect in those environments. The sources presented in this work serve as a benchmark for high-redshift analogs, showing the potential of [Ne v]λ3426 to reveal obscured AGNs and the need for future missions to expand X-ray studies into the high-redshift Universe.
- ItemBASS. XXIX. The Near-infrared View of the Broad-line Region (BLR): The Effects of Obscuration in BLR Characterization(2022) Ricci, Federica ; Treister, Ezequiel ; Bauer, Franz E.; Mejía-Restrepo, Julian E. ; Koss, Michael J. ; den Brok, Jakob S. ; Baloković, Mislav ; Bär, Rudolf ; Bessiere, Patricia ; Caglar, Turgay ; Harrison, Fiona ; Ichikawa, Kohei ; Kakkad, Darshan; Lamperti, Isabella ; Mushotzky, Richard ; Oh, Kyuseok ; Powell, Meredith C. ; Privon, George C. ; Ricci, Claudio ; Riffel, Rogerio ; Rojas, Alejandra F. ; Sani, Eleonora ; Smith, Krista L. ; Stern, Daniel ; Trakhtenbrot, Benny ; Urry, C. Megan ; Veilleux, Sylvain
- ItemBASS. XXV. DR2 Broad-line-based Black Hole Mass Estimates and Biases from Obscuration(2022) Mejía-Restrepo, Julian E.; Trakhtenbrot, Benny; Koss, Michael J.; Oh, Kyuseok; den Brok, Jakob; Stern, Daniel; Powell, Meredith C.; Ricci, Federica; Caglar, Turgay; Ricci, Claudio; Bauer, Franz Erik; Treister , Ezequiel; Harrison, Fiona A.; Urry, C. M.; Ananna, Tonima Tasnim; Asmus, Daniel; Assef, Roberto J.; Bär, Rudolf E.; Bessiere, Patricia S.; Burtscher, Leonard; Ichikawa, Kohei; Kakkad, Darshan; Kamraj, Nikita; Mushotzky, Richard; Privon, George C.; Rojas, Alejandra F.; Sani, Eleonora; Schawinski, Kevin; Veilleux, SylvainWe present measurements of broad emission lines and virial estimates of supermassive black hole masses (M _{BH} ) for a large sample of ultrahard X-ray-selected active galactic nuclei (AGNs) as part of the second data release of the BAT AGN Spectroscopic Survey (BASS/DR2). Our catalog includes M _{BH} estimates for a total of 689 AGNs, determined from the Hα, Hβ, Mg II λ2798, and/or C_{IV} λ1549 broad emission lines. The core sample includes a total of 512 AGNs drawn from the 70 month Swift/BAT all-sky catalog. We also provide measurements for 177 additional AGNs that are drawn from deeper Swift/BAT survey data. We study the links between M _{BH} estimates and line-of-sight obscuration measured from X-ray spectral analysis. We find that broad Hα emission lines in obscured AGNs (Log(N_{H} / cm^{-2} > 22.0) are on average a factor of 8.0_{-2.4}^{+4.1} weaker relative to ultrahard X-ray emission and about 35_{-12}^{,+7} % narrower than those in unobscured sources (i.e.(Log(N_{H} / cm^{-2} > 21.5). This indicates that the innermost part of the broad-line region is preferentially absorbed. Consequently, current single-epoch M _{BH} prescriptions result in severely underestimated (>1 dex) masses for Type 1.9 sources (AGNs with broad Hα but no broad Hβ) and/or sources with Log(N_{H} / cm^{-2} >= 22.0 . We provide simple multiplicative corrections for the observed luminosity and width of the broad Hα component (LbHα and FWHMbHα) in such sources to account for this effect and to (partially) remedy M _{BH} estimates for Type 1.9 objects. As a key ingredient of BASS/DR2, our work provides the community with the data needed to further study powerful AGNs in the low-redshift universe.
- ItemBASS. XXXIV. A Catalog of the Nuclear Millimeter-wave Continuum Emission Properties of AGNs Constrained on Scales ≤ 100-200 pc(IOP Publishing Ltd, 2023) Kawamuro, Taiki; Ricci, Claudio; Mushotzky, Richard F.; Imanishi, Masatoshi; Bauer, Franz Erik; Ricci, Federica; Koss, Michael J.; Privon, George C.; Trakhtenbrot, Benny; Izumi, Takuma; Ichikawa, Kohei; Rojas, Alejandra F.; Smith, Krista Lynne; Shimizu, Taro; Oh, Kyuseok; den Brok, Jakob S.; Baba, Shunsuke; Balokovic, Mislav; Chang, Chin-Shin; Kakkad, Darshan; Pfeifle, Ryan W.; Temple, Matthew J.; Ueda, Yoshihiro; Harrison, Fiona; Powell, Meredith C.; Stern, Daniel; Urry, Meg; Sanders, David B.We present a catalog of the millimeter-wave (mm-wave) continuum properties of 98 nearby (z < 0.05) active galactic nuclei (AGNs) selected from the 70 month Swift/BAT hard-X-ray catalog that have precisely determined X-ray spectral properties and subarcsecond-resolution Atacama Large Millimeter/submillimeter Array Band 6 (211-275 GHz) observations as of 2021 April. Due to the hard-X-ray (>10 keV) selection, the sample is nearly unbiased for obscured systems at least up to Compton-thick-level obscuration, and provides the largest number of AGNs with high-physical-resolution mm-wave data (less than or similar to 100-200 pc). Our catalog reports emission peak coordinates, spectral indices, and peak fluxes and luminosities at 1.3 mm (230 GHz). Additionally, high-resolution mm-wave images are provided. Using the images and creating radial surface brightness profiles of mm-wave emission, we identify emission extending from the central sources and isolated blob-like emission. Flags indicating the presence of these emission features are tabulated. Among 90 AGNs with significant detections of nuclear emission, 37 AGNs (approximate to 41%) appear to have both or one of extended or blob-like components. We, in particular, investigate AGNs that show well-resolved mm-wave components and find that these seem to have a variety of origins (i.e., a jet, radio lobes, a secondary AGN, stellar clusters, a narrow-line region, galaxy disk, active star formation regions, or AGN-driven outflows), and some components have currently unclear origins.
- ItemBASS. XXXV. The MBH-σ* Relation of 105 Month Swift-BAT Type 1 AGNs(IOP Publishing Ltd, 2023) Caglar, Turgay; Koss, Michael J.; Burtscher, Leonard; Trakhtenbrot, Benny; Erdim, M. Kiyami; Mejia-Restrepo, Julian E.; Ricci, Federica; Powell, Meredith C.; Ricci, Claudio; Mushotzky, Richard; Bauer, Franz Erik; Ananna, Tonima T.; Baer, Rudolf E.; Brandl, Bernhard; Brinchmann, Jarle; Harrison, Fiona; Ichikawa, Kohei; Kakkad, Darshan; Oh, Kyuseok; Riffel, Rogerio; Sartori, Lia F.; Smith, Krista L.; Stern, Daniel; Urry, C. MeganWe present two independent measurements of stellar velocity dispersions (sigma(star)) from the Ca II H+K lambda 3969, 3934 and Mg I b lambda 5183, 5172, 5167 region (3880-5550 angstrom) and the calcium triplet region (8350-8750 angstrom) for 173 hard X-ray-selected Type 1 active galactic nuclei (AGNs; z <= 0.08) from the 105 month Swift-BAT catalog. We construct one of the largest samples of local Type 1 AGNs that have both single-epoch virial black hole mass (M-BH) estimates and sigma(star) measurements obtained from high spectral resolution data, allowing us to test the usage of such methods for supermassive black hole studies. We find that the two independent sigma(star) measurements are highly consistent with each other, with an average offset of only 0.002 +/- 0.001 dex. Comparing M-BH estimates based on broad emission lines and stellar velocity dispersion measurements, we find that the former is systematically lower by approximate to 0.12 dex. Consequently, Eddington ratios estimated through broad-line MBH determinations are similarly biased (but in the opposite way). We argue that the discrepancy is driven by extinction in the broad-line region. We also find an anticorrelation between the offset from the M-BH-sigma(star) relation and the Eddington ratio. Our sample of Type 1 AGNs shows a shallower M-BH-sigma(star) relation (with a power-law exponent of approximate to 3.5) compared with that of inactive galaxies (with a power-law exponent of approximate to 4.5), confirming earlier results obtained from smaller samples.
- ItemProbing 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.
- ItemUGC 4211: A Confirmed Dual Active Galactic Nucleus in the Local Universe at 230 pc Nuclear Separation(2023) Koss, Michael J.; Treister, Ezequiel; Kakkad, Darshan; Casey-Clyde, J. Andrew; Kawamuro, Taiki; Williams, Jonathan; Foord, Adi; Trakhtenbrot, Benny; Bauer, Franz E.; Privon, George C.; Ricci, Claudio; Mushotzky, Richard; Barcos-Munoz, Loreto; Blecha, Laura; Connor, Thomas; Harrison, Fiona; Liu, Tingting; Magno, Macon; Mingarelli, Chiara M. F.; Muller-Sanchez, Francisco; Oh, Kyuseok; Shimizu, T. Taro; Smith, Krista Lynne; Stern, Daniel; Tello, Miguel Parra; Urry, C. MeganWe present multiwavelength high-spatial resolution (similar to 0 ? 1, 70 pc) observations of UGC 4211 at z = 0.03474, a late-stage major galaxy merger at the closest nuclear separation yet found in near-IR imaging (0 " 32, similar to 230 pc projected separation). Using Hubble Space Telescope/Space Telescope Imaging Spectrograph, Very Large Telescope/MUSE+AO, Keck/OSIRIS+AO spectroscopy, and the Atacama Large Millimeter/submillimeter Array (ALMA) observations, we show that the spatial distribution, optical and near-infrared emission lines, and millimeter continuum emission are all consistent with both nuclei being powered by accreting supermassive black holes (SMBHs). Our data, combined with common black hole mass prescriptions, suggest that both SMBHs have similar masses, log (M-BH M-?) similar to 8.1 (south) and log (M-BH M-?) similar to 8.3 (north), respectively. The projected separation of 230 pc (similar to 6x the black hole sphere of influence) represents the closest-separation dual active galactic nuclei (AGN) studied to date with multiwavelength resolved spectroscopy and shows the potential of nuclear (< 50 pc) continuum observations with ALMA to discover hidden growing SMBH pairs. While the exact occurrence rate of close-separation dual AGN is not yet known, it may be surprisingly high, given that UGC 4211 was found within a small, volume-limited sample of nearby hard X-ray detected AGN. Observations of dual SMBH binaries in the subkiloparsec regime at the final stages of dynamical friction provide important constraints for future gravitational wave observatories.