Deep Silicate Absorption Features in Compton-Thick Active Galactic Nuclei Predominantly Arise Due to Dust in the Host Galaxy

Goulding, A. D.; Alexander, D. M.; Bauer, F. E.; Forman, W.; Hickox, R. C.; Jones, C.; Mullaney, James; Trichas, M.

doi:10.1088/0004-637x/755/1/5

Cited by 151 publications

(191 citation statements)

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“…This galaxy shows extended soft X-ray emission perpendicular to the IR emission and a point-like source at hard X-rays (see Appendix C.1). It is also a Compton-thick source Goulding et al 2012), with a column density of 1.1 × 10 24 cm −2 measured with BeppoSAX (Cappi et al 1999).…”

Section: B8 Markmentioning

confidence: 94%

“…In the present work, 12 nuclei are classified as Comptonthick candidates. Among them, variations are found only in MARK 3, which was previously classified as a Compton-thick candidate Goulding et al 2012), with a column density of 1.1 × 10 24 cm −2 measured by BeppoSAX (Cappi et al 1999). In fact, variations in MARK 3 have already been reported by Guainazzi et al (2012), who studied its variability using XMM-Newton, Suzaku, and Swift data, and found variations on timescales of months.…”

Section: Compton-thicknessmentioning

confidence: 99%

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X-ray spectral variability of Seyfert 2 galaxies

Hernández-García

Masegosa

González‐Martín³

et al. 2015

A&A

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Context. Variability across the electromagnetic spectrum is a property of active galactic nuclei (AGN) that can help constrain the physical properties of these galaxies. Nonetheless, the way in which the changes happen and whether they occur in the same way in every AGN are still open questions. Aims. This is the third in a series of papers with the aim of studying the X-ray variability of different families of AGN. The main purpose of this work is to investigate the variability pattern(s) in a sample of optically selected Seyfert 2 galaxies. Methods. We use the 26 Seyfert 2s in the Véron-Cetty and Véron catalog with data available from Chandra and/or XMM-Newton public archives at different epochs, with timescales ranging from a few hours to years. All the spectra of the same source were simultaneously fitted, and we let different parameters vary in the model. Whenever possible, short-term variations from the analysis of the light curves and/or long-term UV flux variations were studied. We divided the sample into Compton-thick and Compton-thin candidates to account for the degree of obscuration. When transitions between Compton-thick and thin were obtained for different observations of the same source, we classified it as a changing-look candidate. Results. Short-term variability at X-rays was studied in ten cases, but variations are not found. From the 25 analyzed sources, 11 show long-term variations. Eight (out of 11) are Compton-thin, one (out of 12) is Compton-thick, and the two changing-look candidates are also variable. The main driver for the X-ray changes is related to the nuclear power (nine cases), while variations at soft energies or related to absorbers at hard X-rays are less common, and in many cases these variations are accompanied by variations in the nuclear continuum. At UV frequencies, only NGC 5194 (out of six sources) is variable, but the changes are not related to the nucleus. We report two changing-look candidates, MARK 273 and NGC 7319. Conclusions. A constant reflection component located far away from the nucleus plus a variable nuclear continuum are able to explain most of our results. Within this scenario, the Compton-thick candidates are dominated by reflection, which suppresses their continuum, making them seem fainter, and they do not show variations (except MARK 3), while the Compton-thin and changing-look candidates do.

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Section: B8 Markmentioning

confidence: 94%

Section: Compton-thicknessmentioning

confidence: 99%

X-ray spectral variability of Seyfert 2 galaxies

Hernández-García

Masegosa

González‐Martín³

et al. 2015

A&A

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“…9, bottom), considering both X-ray 8 For sources like Mkn 3 and Mkn 231, this is a good estimate of the AGN 6 µm luminosity since their MIR spectra are dominated by the AGN (e.g. Weedman et al 2005;Goulding et al 2012); however, for other sources, e.g. NGC 4945, where the MIR emission is dominated by star formation (e.g.…”

Section: Infrared Agnmentioning

confidence: 99%

“…Moreover, at these wavelengths the effects of extinction are small, making it easier, in theory, to find even the most obscured AGN (e.g. Gandhi et al 2009;Goulding et al 2012). The downside of using the IR band to search for AGN activity is that dust is present not only in the circumnuclear region of AGN, but also in the host galaxy, in particular in star-forming regions.…”

Section: Introductionmentioning

confidence: 99%

GOODS-Herschel: radio-excess signature of hidden AGN activity in distant star-forming galaxies

Moro

Alexander

Mullaney

et al. 2012

A&A

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Context. A tight correlation exists between far-infrared and radio emission for star-forming galaxies (SFGs), which seems to hold out to high redshifts (z ≈ 2). Any excess of radio emission over that expected from star formation processes is most likely produced by an active galactic nucleus (AGN), often hidden by large amounts of dust and gas. Identifying these radio-excess sources will allow us to study a population of AGN unbiased by obscuration and thus find some of the most obscured, Compton-thick AGN, which are in large part unidentified even in the deepest X-ray and infrared (IR) surveys. Aims. We present here a new spectral energy distribution (SED) fitting approach that we adopt to select radio-excess sources amongst distant star-forming galaxies in the GOODS-Herschel (North) field and to reveal the presence of hidden, highly obscured AGN. Methods. Through extensive SED analysis of 458 galaxies with radio 1.4 GHz and mid-IR 24 µm detections using some of the deepest Chandra X-ray, Spitzer and Herschel infrared, and VLA radio data available to date, we have robustly identified a sample of 51 radio-excess AGN (∼1300 deg −2 ) out to redshift z ≈ 3. These radio-excess AGN have a significantly lower far-IR/radio ratio (q < 1.68, 3σ) than the typical relation observed for star-forming galaxies (q ≈ 2.2). Results. We find that ≈45% of these radio-excess sources have a dominant AGN component in the mid-IR band, while for the remainders the excess radio emission is the only indicator of AGN activity. The presence of an AGN is also confirmed by the detection of a compact radio core in deep VLBI 1.4 GHz observations for eight of our radio-excess sources (≈16%; ≈66% of the VLBI detected sources in this field), with the excess radio flux measured from our SED analysis agreeing, to within a factor of two, with the radio core emission measured by VLBI. We find that the fraction of radio-excess AGN increases with X-ray luminosity reaching ∼60% at L X ≈ 10 44 −10 45 erg s −1 , making these sources an important part of the total AGN population. However, almost half (24/51) of these radio-excess AGN are not detected in the deep Chandra X-ray data, suggesting that some of these sources might be heavily obscured. Amongst the radio-excess AGN we can distinguish three groups of objects: i) AGN clearly identified in infrared (and often in X-rays), a fraction of which are likely to be distant Compton-thick AGN; ii) moderate luminosity AGN (L X 10 43 erg s −1 ) hosted in strong star-forming galaxies; and iii) a small fraction of low accretion-rate AGN hosted in passive (i.e. weak or no star-forming) galaxies. We also find that the specific star formation rates (sSFRs) of the radio-excess AGN are on average lower that those observed for X-ray selected AGN hosts, indicating that our sources are forming stars more slowly than typical AGN hosts, and possibly their star formation is progressively quenching.

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“…Hönig et al 2006;Nenkova et al 2008a,b;Deo et al 2011;Mullaney et al 2011;Stalevski et al 2012;Baloković et al 2014;He, Liu & Zhang 2016;Marinucci et al 2016;Gallagher et al 2015), and those obscured by some other dust distribution ("non-torus obscured", or NTO, quasars, e.g. Goulding et al 2012). It is this latter subset that are of interest in an evolutionary framework, while the former are unified by simple orientation -i.e.…”

Section: Introductionmentioning

confidence: 99%

A unifying evolutionary framework for infrared-selected obscured and unobscured quasar host haloes

DiPompeo

Hickox

Myers

2016

Mon. Not. R. Astron. Soc.

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Recent measurements of the dark matter halo masses of infrared-selected obscured quasars are in tension -some indicate that obscured quasars have higher halo mass compared to their unobscured counterparts, while others find no difference. The former result is inconsistent with the simplest models of quasar unification that rely solely on viewing angle, while the latter may support such models. Here, using empirical relationships between dark matter halo and supermassive black hole masses, we provide a simple evolutionary picture that naturally explains these findings and is motivated by more sophisticated merger-driven quasar fueling models. The model tracks the growth rate of haloes, with the black hole growing in spurts of quasar activity in order to "catch-up" with the M bh -M stellar -M halo relationship. The first part of the quasar phase is obscured and is followed by an unobscured phase. Depending on the luminosity limit of the sample, driven by observational selection effects, a difference in halo masses may or may not be significant. For high luminosity samples, the difference can be large (a few to 10 times higher masses in obscured quasars), while for lower luminosity samples the halo mass difference is very small, much smaller than current observational constraints. Such a simple model provides a qualitative explanation for the higher mass haloes of obscured quasars, as well as rough quantitative agreement with seemingly disparate results.

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Deep Silicate Absorption Features in Compton-Thick Active Galactic Nuclei Predominantly Arise Due to Dust in the Host Galaxy

Cited by 151 publications

References 89 publications

X-ray spectral variability of Seyfert 2 galaxies

X-ray spectral variability of Seyfert 2 galaxies

GOODS-Herschel: radio-excess signature of hidden AGN activity in distant star-forming galaxies

A unifying evolutionary framework for infrared-selected obscured and unobscured quasar host haloes

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