Browsing by Author "Peca, Alessandro"

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    Accretion history of AGN: Estimating the host galaxy properties in X-ray luminous AGN from z=0-3
    (2022) Coleman, Brandon; Kirkpatrick, Allison; Cooke, Kevin C.; Glikman, Eilat; La Massa, Stephanie; Marchesi, Stefano; Peca, Alessandro; Treister, Ezequiel; Auge, Connor; Urry, C. Megan; Sanders, Dave; Turner, Tracey Jane; Ananna, Tonima Tasnim
    We aim to determine the intrinsic far-Infrared (far-IR) emission of X-ray-luminous quasars over cosmic time. Using a 16 deg(2) region of the Stripe 82 field surveyed by XMM-Newton and Herschel Space Observatory, we identify 2905 X-ray luminous (L-X > 10(42) erg/s) active galactic nuclei (AGN) in the range z approximate to 0-3. The IR is necessary to constrain host galaxy properties such as star formation rate (SFR) and gas mass. However, only 10 per cent of our AGN are detected both in the X-ray and IR. Because 90 per cent of the sample is undetected in the far-IR by Herschel, we explore the mean IR emission of these undetected sources by stacking their Herschel/SPIRE images in bins of X-ray luminosity and redshift. We create stacked spectral energy distributions from the optical to the far-IR, and estimate the median SFR, dust mass, stellar mass, and infrared luminosity using a fitting routine. We find that the stacked sources on average have similar SFR/L-bol ratios as IR detected sources. The majority of our sources fall on or above the main sequence line suggesting that X-ray selection alone does not predict the location of a galaxy on the main sequence. We also find that the gas depletion time scales of our AGN are similar to those of dusty star forming galaxies. This suggests that X-ray selected AGN host high star formation and that there are no signs of declining star formation.
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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.