Inferring Compton-thick AGN candidates at z &gt; 2 with Chandra using the &gt;8 keV rest-frame spectral curvature

Baronchelli, L.; Koss, Michael; Schawinski, Kevin; Cardamone, Carolin N.; Civano, F.; Comastri, A.; Elvis, M.; Lanzuisi, G.; Marchesi, S.; Ricci, Cláudio; Salvato, M.; Trakhtenbrot, Benny; Treister, Ezequiel

doi:10.1093/mnras/stx1561

Cited by 6 publications

(6 citation statements)

References 45 publications

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“…Yet again, the heavily absorbed AGNs generally occupy the same parameter space as unobscured AGNs. The spectral curvature method (Koss et al 2016) may provide a more effective means of selecting heavily AGNs at higher redshift in the XXL-N field, and indeed, Baronchelli et al (2017) demonstrated its effectiveness in selecting high-redshift (z > 2) CT AGNs in both the Chandra Deep Field South and the Chandra COSMOS legacy survey.…”

Section: Diagnosis Of N H In the Xmm Xxl Fieldmentioning

confidence: 99%

BASS. XXIII. A New Mid-infrared Diagnostic for Absorption in Active Galactic Nuclei

Pfeifle¹,

Ricci²,

Boorman³

et al. 2022

ApJS

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In this study, we use the Swift/BAT AGN sample, which has received extensive multiwavelength follow-up analysis as a result of the BAT AGN Spectroscopic Survey, to develop a diagnostic for nuclear obscuration by examining the relationship between the line-of-sight column densities (N H), the 2–10 keV to 12 μm luminosity ratio, and WISE mid-infrared colors. We demonstrate that heavily obscured AGNs tend to exhibit both preferentially “redder” mid-infrared colors and lower values of L X,Obs./L 12 μm than less obscured AGNs, and we derive expressions relating N H to the L X,Obs./L 12 μm and L 22 μm/L 4.6 μm luminosity ratios, as well as develop diagnostic criteria using these ratios. Our diagnostic regions yield samples that are ≳80% complete and ≳60% pure for AGNs with log(N H/cm−2) ≥ 24, as well as ≳85% pure for AGNs with log ( N H / cm − 2 ) ≳ 23.5 . We find that these diagnostics cannot be used to differentiate between optically star-forming galaxies and active galaxies. Further, mid-IR contributions from host galaxies that dominate the observed 12 μm emission can lead to larger apparent X-ray deficits and redder mid-IR colors than the AGNs would intrinsically exhibit, though this effect helps to better separate less and more obscured AGNs. Finally, we test our diagnostics on two catalogs of AGNs and infrared galaxies, including the XMM-Newton XXL-N field, and we identify several known Compton-thick AGNs, as well as a handful of candidate heavily obscured AGNs based upon our proposed obscuration diagnostics.

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Section: Diagnosis Of N H In the Xmm Xxl Fieldmentioning

confidence: 99%

BASS. XXIII. A New Mid-infrared Diagnostic for Absorption in Active Galactic Nuclei

Pfeifle¹,

Ricci²,

Boorman³

et al. 2022

ApJS

Self Cite

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“…At these high column densities, the attenuation of X-rays is mainly due to Compton-scattering rather than photoelectric absorption; these sources are the so-called "Compton-thick" (CT) AGNs (N H 1.5 × 10 24 cm −2 ), of which only a few have been identified in the local Universe (Burlon et al 2011;Ricci et al 2015, and references therein). At higher redshifts, hundreds of CT AGN candidates have been identified in X-rays thanks to XMM and Chandra observations at E<10 keV (e.g., Comastri et al 2011;Feruglio et al 2011;Brightman et al 2014;Buchner et al 2015;Baronchelli et al 2017) and NuSTAR data at higher X-ray energies (e.g., Civano et al 2015;Mullaney et al 2015;Lansbury et al 2017).…”

Section: Introductionmentioning

confidence: 99%

The Composite Nature of Dust-obscured Galaxies (DOGs) at z ∼ 2–3 in the COSMOS Field. II. The AGN Fraction

Riguccini¹,

Treister

Menéndez‐Delmestre³

et al. 2019

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We present the X-ray properties of 108 Dust-Obscured Galaxies (DOGs; F 24µm /F R > 1000) in the COSMOS field, all of which detected in at least three far-infrared bands with the Herschel Observatory. Out of the entire sample, 22 are individually detected in the hard 2-8 keV X-ray band by the Chandra COSMOS Legacy survey, allowing us to classify them as AGN. Of them, 6 (27%) are Compton Thick AGN candidates with column densities N H >10 24 cm −2 while 15 are moderately obscured AGNs with 10 22 < N H < 10 24 cm −2 . Additionally, we estimate AGN contributions to the IR luminosity (8-1000µm rest-frame) greater than 20% for 19 DOGs based on SED decomposition using Spitzer/MIPS 24µm and the five Herschel bands (100-500 µm). Only 7 of these are detected in X-rays individually. We performed a X-ray stacking analysis for the 86 undetected DOGs. We find that the AGN fraction 2 Riguccini et al.in DOGs increases with 24µm flux and that it is higher than that of the general 24µm population. However, no significant difference is found when considering only X-ray detections. This strongly motivates the combined use of X-ray and far-IR surveys to successfully probe a wider population of AGNs, particularly for the most obscured ones.

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“…Koss et al (2016) developed an SC analysis technique that uses weighted averages of different energy bands above 10 keV to estimate the Compton thickness of an AGN. For CT AGN, the SC value calculated is SC CT ≥ 0.4 (Koss et al 2016;Baronchelli et al 2017). We applied this technique to the two AGNs in our sample that are detected at E > 10 keV, i.e.…”

Section: Discussionmentioning

confidence: 99%

NuSTAR observations of four nearby X-ray faint AGNs: low luminosity or heavy obscuration?

Annuar

Alexander

Gandhi

et al. 2020

Monthly Notices of the Royal Astronomical Society

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We present NuSTAR observations of four active galactic nuclei (AGN) located within 15 Mpc. These AGN, namely ESO 121-G6, NGC 660, NGC 3486 and NGC 5195, have observed X-ray luminosities of L2-10 keV, obs ≲ 1039 erg s−1, classifying them as low luminosity AGN (LLAGN). We perform broadband X-ray spectral analysis for the AGN by combining our NuSTAR data with Chandra or XMM-Newton observations to directly measure their column densities (NH) and infer their intrinsic power. We complement our X-ray data with archival and new high angular resolution mid-infrared (mid-IR) data for all objects, except NGC 5195. Based on our X-ray spectral analysis, we found that both ESO 121-G6 and NGC 660 are heavily obscured (NH > 1023 cm−2; L2-10 keV, int ∼ 1041 erg s−1), and NGC 660 may be Compton-thick. We also note that the X-ray flux and spectral slope for ESO 121-G6 have significantly changed over the last decade, indicating significant changes in the obscuration and potentially accretion rate. On the other hand, NGC 3486 and NGC 5195 appear to be unobscured and just mildly obscured, respectively, with L2-10 keV, int < 1039 erg s−1; i.e., genuine LLAGN. Both of the heavily obscured AGN have Lbol > 1041 erg s−1 and λEdd ≳ 10−3, and are detected in high angular resolution mid-IR imaging, indicating the presence of obscuring dust on nuclear scale. NGC 3486 however, is undetected in high-resolution mid-IR imaging, and the current data do not provide stringent constraints on the presence or absence of obscuring nuclear dust in the AGN.

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Inferring Compton-thick AGN candidates at z > 2 with Chandra using the >8 keV rest-frame spectral curvature

Cited by 6 publications

References 45 publications

BASS. XXIII. A New Mid-infrared Diagnostic for Absorption in Active Galactic Nuclei

BASS. XXIII. A New Mid-infrared Diagnostic for Absorption in Active Galactic Nuclei

The Composite Nature of Dust-obscured Galaxies (DOGs) at z ∼ 2–3 in the COSMOS Field. II. The AGN Fraction

NuSTAR observations of four nearby X-ray faint AGNs: low luminosity or heavy obscuration?

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