Browsing by Author "Peca, Alessandro"
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- ItemAccretion 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 TasnimWe 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.
- 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. LIV. Physical Properties of AGN-hosting Galaxy Mergers from Multiwavelength SED Fitting(2025) Troncoso Balbiano, Marco Javier; Treister, Ezequiel; Rojas, Alejandra; Boquien, Médéric; Bauer, Franz; Koss, Michael J.; Assef, Roberto J.; Parra Tello, Miguel Agustín; Moral-Castro, Ignacio del; Ricci, Claudio; Dai, Sophia; Oh, Kyuseok; Ricci, Federica; Peca, Alessandro; Urry, C. Megan; Gupta, Kriti Kamal; Venturi, Giacomo; Signorini, Matilde; Mushotzky, Richard; Sanders, DavidGalaxy mergers are believed to play an important role in triggering rapid supermassive black hole (SMBH) growth. As merging nuclei approach each other, the physical properties of the participating galaxies and the associated SMBH growth are expected to evolve significantly. This study measures and characterizes these physical properties throughout the merger sequence. We constructed multiwavelength Spectral Energy Distributions (SEDs) from hard X-rays to the far-infrared (FIR) for a sample of 72 nearby Active Galactic Nuclei (AGN) host galaxies. The sample comprises 64 interacting systems, including single AGNs in mergers and dual AGNs, with nuclear separations 30 kpc, as well as eight isolated active galaxies with merging features. We carefully adapted available photometric measurements at each wavelength to account for their complex morphologies and varying spatial resolutions, to perform SED fitting using CIGALE, aimed to derive critical physical properties. Our results reveal that merging galaxies hosting AGN(s) show deviations from the star-forming main sequence, and a wide range of star formation rates (SFRs). Both AGN activity and star formation are significantly influenced by the merger process, but these effects are more prominent in major, mass ratios 4:1, interactions. We find that the projected nuclear separation is not a good tracer of the merger stage. Instead, morphological classification accurately assesses the merger progression. Based on this morphological analysis, late-stage mergers exhibit elevated SFRs (5.1), AGN luminosities (2.4), and nuclear obscuration (2.8) compared to earlier stages, supporting previous findings and reinforcing the link between merger-driven galaxy evolution and SMBH growth.
- 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. XLV. Quantifying Active Galactic Nuclei Selection Effects in the Chandra COSMOS-legacy Survey with BASS(IOP Publishing Ltd, 2025) Tokayer, Yarone M.; Koss, Michael J.; Urry, C. Megan; Natarajan, Priyamvada; Mushotzky, Richard; Balokovic, Mislav; Bauer, Franz Erik; Boorman, Peter; Peca, Alessandro; Ricci, Claudio; Ricci, Federica; Stern, Daniel; Treister, Ezequiel; Trakhtenbrot, BennyDeep extragalactic X-ray surveys, such as the Chandra COSMOS-Legacy field (CCLS), are prone to be biased against active galactic nuclei (AGN) with high column densities due to their lower count rates at a given luminosity. To quantify this selection effect, we forward model nearby (z similar to 0.05) AGN from the BAT AGN Spectroscopic Survey (BASS) with well-characterized (greater than or similar to 1000 cts) broadband X-ray spectra (0.5-195 keV) to simulate the CCLS absorption distribution. We utilize the BASS low-redshift analogs with similar luminosities to the CCLS (L-2-10keV(int) similar to 10(42-45) erg s), which are much less affected by obscuration and low-count statistics, as the seed for our simulations and follow the spectral fitting of the CCLS. Our simulations reveal that Chandra would fail to detect the majority (53.3%; 563/1056) of obscured (N-H >= 10(22) cm(-2)) simulated BASS AGN given the observed redshift and luminosity distribution of the CCLS. Even for detected sources with sufficient counts (>= 30) for spectral modeling, the level of obscuration is significantly overestimated. This bias is most extreme for objects whose best fit indicates a high-column density AGN (N-H >= 10(24) cm(-2)), since the majority (66.7%; 18/27) of these are actually unobscured sources (N-H < 10(22) cm(-2)). This implies that previous studies may have significantly overestimated the increase in the obscured fraction with redshift and the fraction of luminous obscured AGN. Our findings highlight the importance of directly considering obscuration biases and forward modeling in X-ray surveys, as well as the need for higher-sensitivity X-ray missions such as the Advanced X-ray Imaging Satellite (AXIS), and the importance of multiwavelength indicators to estimate obscuration in distant supermassive black holes.
- ItemOn 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, ChuanWe 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.
- ItemStripe 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, EzequielWe 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.
- ItemThe 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 JaneSpectral 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.