Browsing by Author "Sanders, David"

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    BASS. 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, David
    We 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.
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    On the Cosmic Evolution of AGN Obscuration and the X-Ray Luminosity Function: XMM-Newton and Chandra Spectral Analysis of the 31.3 deg2 Stripe 82X
    (2023) Peca, Alessandro; Cappelluti, Nico; Urry, C. Megan; LaMassa, Stephanie; Marchesi, Stefano; Ananna, Tonima Tasnim; Balokovic, Mislav; Sanders, David; Auge, Connor; Treister, Ezequiel; Powell, Meredith; Turner, Tracey Jane; Kirkpatrick, Allison; Tian, Chuan
    We present X-ray spectral analysis of XMM-Newton and Chandra observations in the 31.3 deg(2) Stripe-82X (S82X) field. Of the 6181 unique X-ray sources in this field, we analyze a sample of 2937 candidate active galactic nuclei (AGNs) with solid redshifts and sufficient counts determined by simulations. Our results show an observed population with median values of spectral index gamma = 1.94(-0.39) (+0.31), column density log N-H/cm(-2) = 20.7(-0.5) (+1.2) and intrinsic, de-absorbed, 2-10 keV luminosity log L-X/ erg s(-1 ) = 44.0(-1.0)(+0.7), in the redshift range 0-4. We derive the intrinsic, model-independent, fraction of AGNs that are obscured (22 <= log N-H / cm(-2) < 24), finding a significant increase in the obscured AGN fraction with redshift and a decline with increasing luminosity. The average obscured AGN fraction is 57% +/- 4% for log L-X/erg s(-1) > 43. This work constrains the AGN obscuration and spectral shape of the still uncertain high-luminosity and high-redshift regimes (log L-X/erg s(-1) > 45.5, z > 3), where the obscured AGN fraction rises to 64% +/- 12%. We report a luminosity and density evolution of the X-ray luminosity function, with obscured AGNs dominating at all luminosities at z > 2, and unobscured sources prevailing at log L-X/erg s(-1) > 45 at lower redshifts. Our results agree with the evolutionary models in which the bulk of AGN activity is triggered by gas-rich environments and in a downsizing scenario. Moreover, the black hole accretion density (BHAD) is found to evolve similarly to the star formation rate density, confirming the coevolution between AGN and host galaxy, but suggesting different timescales in their growing history. The derived BHAD evolution shows that Compton-thick AGNs contribute to the accretion history of AGNs as much as all other AGN populations combined.
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    Stripe 82-XL: The ∼54.8 deg2 and ∼18.8 Ms Chandra and XMM-Newton Point-source Catalog and Number of Counts
    (2024) Peca, Alessandro; Cappelluti, Nico; Lamassa, Stephanie; Urry, C. Megan; Moscetti, Massimo; Marchesi, Stefano; Sanders, David; Auge, Connor; Ghosh, Aritra; Ananna, Tonima Tasnim; Torres-Alba, Nuria; Treister, Ezequiel
    We present an enhanced version of the publicly available Stripe 82X catalog (S82-XL), featuring a comprehensive set of 22,737 unique X-ray point sources identified with a significance greater than or similar to 4 sigma. This catalog is four times larger than the original Stripe 82X catalog, by including additional archival data from the Chandra and XMM-Newton telescopes. Now covering similar to 54.8 deg(2 )of nonoverlapping sky area, the S82-XL catalog roughly doubles the area and depth of the original catalog, with limiting fluxes (half-area fluxes) of 3.4 x 10(-16) (2.4 x 10(-15)), 2.9 x 10(-15) (1.5 x 10(-14)), and 1.4 x 10(-15) (9.5 x 10(-15)) erg s(-1) cm(-2) across the soft (0.5-2 keV), hard (2-10 keV), and full (0.5-10 keV) bands, respectively. S82-XL occupies a unique region of flux-area parameter space compared to other X-ray surveys, identifying sources with rest-frame luminosities from 1.2 x 1038 to 1.6 x 1047 erg s(-1) in the 2-10 keV band (median X-ray luminosity, 7.2 x 1043 erg s(-1)), and spectroscopic redshifts up to z similar to 6. By using hardness ratios, we derived the obscuration of active galactic nuclei (AGNs), obtaining a median value of log(NH/cm(-2))=21.6-1.6+1.0 and an overall, obscured fraction ( log(NH/cm-2)>22 ) of similar to 36.9%. S82-XL serves as a benchmark in X-ray surveys and, with its extensive multiwavelength data, is especially valuable for comprehensive studies of luminous AGNs.
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    The Accretion History of AGN: The Spectral Energy Distributions of X-Ray-luminous Active Galactic Nuclei
    (2023) Auge, Connor; Sanders, David; Treister, Ezequiel; Urry, C. Megan; Kirkpatrick, Allison; Cappelluti, Nico; Ananna, Tonima Tasnim; Boquien, Médéric; Baloković, Mislav; Civano, Francesca; Coleman, Brandon; Ghosh, Aritra; Kartaltepe, Jeyhan; Koss, Michael; LaMassa, Stephanie; Marchesi, Stefano; Peca, Alessandro; Powell, Meredith; Trakhtenbrot, Benny; Turner, Tracey Jane
    Spectral energy distributions (SEDs) from X-ray to far-infrared (FIR) wavelengths are presented for a sample of 1246 X-ray-luminous active galactic nuclei (AGNs; L0.5–10 keV > 1043 erg s−1), with zspec < 1.2, selected from Stripe 82X, COSMOS, and GOODS-N/S. The rest-frame SEDs show a wide spread (∼2.5 dex) in the relative strengths of broad continuum features at X-ray, ultraviolet (UV), mid-infrared (MIR), and FIR wavelengths. A linear correlation (log–log slope of 0.7 ± 0.04) is found between LMIR and LX. There is significant scatter in the relation between the LUV and LX owing to heavy obscuration; however, the most luminous and unobscured AGNs show a linear correlation (log–log slope of 0.8 ± 0.06) in the relation above this scatter. The relation between LFIR and LX is predominantly flat, but with decreasing dispersion at LX > 1044 erg s−1. The ratio between the "galaxy-subtracted" bolometric luminosity and the intrinsic LX increases from a factor of ∼10 to 70 from log Lbol/(erg s−1) = 44.5 to 46.5. Characteristic SED shapes have been determined by grouping AGNs based on relative strengths of the UV and MIR emission. The average L1μm is constant for the majority of these SED shapes, while AGNs with the strongest UV and MIR emission have elevated L1μm, consistent with the AGN emission dominating their SEDs at optical and near-infrared wavelengths. A strong correlation is found between the SED shape and both the LX and Lbol, such that Lbol/LX = 20.4 ± 1.8, independent of the SED shape. This is consistent with an evolutionary scenario of increasing Lbol with decreasing obscuration as the AGN blows away circumnuclear gas.
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    Warm Molecular Hydrogen in Nearby, Luminous Infrared Galaxies
    (2018) Petric, Andreea O.; Armus, Lee; Flagey, Nicolas; Guillard, Pierre; Howell, Justin; Inami, Hanae; Charmandaris, Vassillis; Evanss, Aaron; Stierwalt, Sabrina; Diaz-Santos, Tanio; Lu, Nanyao; Spoon, Henrik; Mazzarella, Joe; Appleton, Phil; Chan, Ben; Chu, Jason; Hand, Derek; Privon, George; Sanders, David; Surace, Jason; Xu, Kevin; Zhao, Yinghe
    Mid-infrared molecular hydrogen (H-2) emission is a powerful cooling agent in galaxy mergers and in radio galaxies; it is a potential key tracer of gas evolution and energy dissipation associated with mergers, star formation, and accretion onto supermassive black holes. We detect mid-IR H-2 line emission in at least one rotational transition in 91% of the 214 Luminous Infrared Galaxies (LIRGs) observed with Spitzer as part of the Great Observatories All-sky LIRG Survey. We use H-2 excitation diagrams to estimate the range of masses and temperatures of warm molecular gas in these galaxies. We find that LIRGs in which the IR emission originates mostly from the Active Galactic Nuclei (AGN) have about 100 K higher H-2 mass-averaged excitation temperatures than LIRGs in which the IR emission originates mostly from star formation. Between 10% and 15% of LIRGs have H-2 emission lines that are sufficiently broad to be resolved or partially resolved by the high-resolution modules of Spitzer's Infrared Spectrograph (IRS). Those sources tend to be mergers and contain AGN. This suggests that a significant fraction of the H-2 line emission is powered by AGN activity through X-rays, cosmic rays, and turbulence. We find a statistically significant correlation between the kinetic energy in the H-2 gas and the H-2 to IR luminosity ratio. The sources with the largest warm gas kinetic energies are mergers. We speculate that mergers increase the production of bulk inflows leading to observable broad H-2 profiles and possibly denser gas.