Seyfert 2 Galaxies with Spectropolarimetric Observations

Gu, Qing; Huang, Jianfeng

doi:10.1086/342703

Cited by 55 publications

(87 citation statements)

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“…It was optically classified as a Seyfert 2 by Goodrich & Osterbrock (1983), and broad lines were not detected in polarized light (Gu & Huang 2002). A radio counterpart showing a jet was found by Ulvestad & Wilson (1989).…”

Section: B6 Mark 1066mentioning

confidence: 97%

“…This galaxy was optically classified as a Seyfert 2 (Ho et al 1997, see their optical spectra in Appendix C.1). Broad lines were not detected in polarized light (Gu & Huang 2002). A point-like source is detected at hard X-ray energies (see Appendix C.1).…”

Section: B15 Ngc 5194mentioning

confidence: 97%

“…Broad lines were not detected in polarized light (Gu & Huang 2002). The HST image shows dust lanes (Appendix C.1).…”

Section: B10 Ngc 3079mentioning

confidence: 98%

“…However, we revisited the literature to search for hidden broad-line-region (HBLR, an usual name for S1h) and non-hidden broad-line-region (NHBLR) objects (e.g., Tran et al 1992;Tran 1995;Moran et al 2000;Lumsden et al 2001;Gu & Huang 2002). We found two additional HBLR (MARK 1210 and MARK 477) and five NHBLR (MARK 1066, NGC 3079, NGC 5194, NGC 5643, and NGC 7172) sources.…”

Section: Sample and Datamentioning

confidence: 98%

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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: B6 Mark 1066mentioning

confidence: 97%

Section: B15 Ngc 5194mentioning

confidence: 97%

“…Broad lines were not detected in polarized light (Gu & Huang 2002). The HST image shows dust lanes (Appendix C.1).…”

Section: B10 Ngc 3079mentioning

confidence: 98%

Section: Sample and Datamentioning

confidence: 98%

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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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“…Seyfert 1s with significant absorption have been found (e.g., Fiore et al 2001, Cappi et al 2006, along with Seyfert 2s without X-ray absorption (e.g., Pappa et al 2001, Panessa & Bassani 2002. Furthermore, spectropolarimetric surveys indicate that only ∼ 30 − 50% of Seyfert 2s have polarized broad lines (PBLs), which might imply that not all of them harbor hidden BLRs (e.g., Tran 2001, 2003, Gu & Huang 2002. In the soft X-rays the photon index distribution is found to be skewed towards low values of Γ for obscured objects (Brightman & Nandra 2010), while in the hard X-rays, Seyfert 2s have been found to have harder spectra than Seyfert 1s (e.g., , Malizia et al 2003, Deluit & Courvoisier 2003, Ajello et al 2008a, Burlon et al 2011.…”

Section: Introductionmentioning

confidence: 99%

Reflection in Seyfert galaxies and the unified model of AGN

Ricci

Walter

Courvoisier

et al. 2011

A&A

129

143

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We present a deep study of the average hard X-ray spectra of Seyfert galaxies. We aim to test the unified model of active galactic nuclei, and constrain differences and similarities between different classes of objects. We analyzed all public INTEGRAL IBIS/ISGRI data available on all the 165 Seyfert galaxies detected at z < 0.2. Our final sample consists of 44 Seyfert 1s, 29 Seyfert 1.5s, 78 Seyfert 2s, and 14 narrow-line Seyfert 1s. For each subsample, we stacked all the images, and derived their average hard X-ray spectra in the 17-250 keV energy range. We performed a detailed spectral analysis using both a model-independent and a model-dependent approach. All classes of Seyfert galaxies show on average the same nuclear continuum, as foreseen by the zeroth order unified model, with a cutoff energy of E C 200 keV, and a photon index of Γ ≃ 1.8. The average optical depth of the Comptonizing medium is consistent for the different classes (τ ≃ 0.8). Compton-thin Seyfert 2s show a reflection component stronger than Seyfert 1s and Seyfert 1.5s. Most of this reflection is due to mildly obscured (10 23 cm −2 ≤ N H < 10 24 cm −2 ) Seyfert 2s, which have a significantly stronger reflection component (R = 2.2 +4.5 −1.1 ) than Seyfert 1s (R ≤ 0.4), Seyfert 1.5s (R ≤ 0.4) and lightly obscured (N H < 10 23 cm −2 ) Seyfert 2s (R ≤ 0.5). This cannot be explained easily by the unified model. The absorber/reflector in mildly obscured Seyfert 2s might cover a large fraction of the X-ray source, and contain clumps of Compton-thick material. The large reflection found in the spectrum of mildly obscured Seyfert 2s reduces the amount of Compton-thick objects needed to explain the peak of the cosmic X-ray background. Our results are consistent with the fraction of Compton-thick sources being ∼ 10%. The spectra of Seyfert 2s with and without polarized broad lines do not show significant differences, the only difference between the two samples being the higher hard X-ray and bolometric luminosity of Seyfert 2s with polarized broad lines. The average hard X-ray spectrum of narrow-line Seyfert 1s is steeper than those of Seyfert 1s and Seyfert 1.5s, probably due to a lower energy of the cutoff.

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Chandra observations of the H2O megamaser galaxy Mrk1210

Zhang

Fan

2009

Sci. China Ser. G-Phys. Mech. Astron.

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We present the first Chandra X-ray observations of the H 2 O megamaser galaxy Mrk1210 (UGC4203), a Seyfert 2 galaxy at an approximate distance of D ~ 57.6 Mpc. The Chandra X-ray image, with by far the highest angular resolution (~1"), displays an unresolved compact core toward the nuclear region of Mrk1210. Comparisons with the previous X-ray observations in the nuclear emission and the spectral shape indicate a fairly stable phase between 2001 (BeppoSAX and XMM-Newton) and 2004 (Chandra) after a dramatic variation since 1995 (ASCA). The best-fit model of Chandra X-ray spectrum consists of two components. The soft scattered component can be best fitted by a moderately absorbed power-law model adding a spectral line at ~0.9 keV (possibly a Ne-Kα fluorescent line), while the hard nuclear component can be well reproduced by a heavily absorbed power-law model (N H ~ 2×10 23 cm −2 ) with an additional line at ~6.19 keV (close to the Fe-Kα fluorescent line). The derived absorption-corrected X-ray luminosity implies that the dramatic variation of spectral properties is caused by significant changes of the absorbing column density along the line-of-sight, while the intrinsic nuclear X-ray luminosity remains stable. In this case, the absorbers should be anisotropic and its size can be constrained to be less than 0.0013 pc. In addition, we also estimate the mass of central engine, the disk radius and the accretion rate of the accretion disk to be 10 7.12±0.31 M⊙, ~1 pc and 0.006, respectively. active galaxy nuclei, Seyfert galaxy, X-ray, maserThe discovery of optically polarized broad lines in Seyfert 2 galaxies reveals the existence of a hidden broadline region (BLR) and a hidden active galactic nucleus (AGN), although only about half of the studied Seyfert 2s were detected showing those features [1][2][3] . Seyfert 1s and Seyfert 2s appear to be essentially identical, but observed from different viewing angles. X-ray observations of hidden nuclear emission of Seyfert 2s allow us to investigate the physical conditions of the innermost nuclear environment [4] .Mrk1210 (UGC4203) is one of those Seyfert 2 galaxies, which show broad optical emission lines in their polarized spectrum [5] . It hosts a megamaser with an isotropic luminosity of ~100L⊙ and a peak flux density of 0.18 Jy [6] . Whether the maser is triggered by the optically detected outflow identified from its optical emission lines [7] still remains an open question.Recently, several Seyfert galaxies were reported to show transitions of spectral states. Possible reasons are:(1) Large changes of the obscuring column density, i.e., a switch between a Compton-thick and a Compton-thin nuclear environment (or vice-versa; the threshold corresponds to a column density N H ~ 10 24 cm −2 ) or (2) strong variation in AGN activity. These changes, observed e.g. in NGC4051 [8] , NGC2992 [9] , Mrk1210 [10] , NGC6300 [11] , NGC4939 [12] and NGC7638 [13] , were usually detected using different telescopes at epochs several years apart. Toward Mrk1210, first X-ray observations were...

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Seyfert 2 Galaxies with Spectropolarimetric Observations

Cited by 55 publications

References 60 publications

X-ray spectral variability of Seyfert 2 galaxies

X-ray spectral variability of Seyfert 2 galaxies

Reflection in Seyfert galaxies and the unified model of AGN

Chandra observations of the H2O megamaser galaxy Mrk1210

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