X‐Ray Emission from Seyfert 2 Galaxies with Optical Polarized Broad Lines (original) (raw)

Soft X‐Ray Properties of Seyfert Galaxies in the ROSAT All‐Sky Survey

The Astrophysical Journal, 1996

We present the results of ROSAT All-Sky Survey observations of Seyfert and IR-luminous galaxies from the Extended 12 µm Galaxy Sample and the optically-selected CfA Sample. Detections are available for 80% (44/55) of the Seyfert 1s and 34% (23/67) of the Seyfert 2s in the 12 µm sample, and for 76% (26/34) of the Seyfert 1s and 38% (6/16) of the Seyfert 2s in the CfA sample.

On the relation of optical obscuration and X-ray absorption in Seyfert galaxies

Astronomy & Astrophysics, 2016

The optical classification of a Seyfert galaxy and whether it is considered X-ray absorbed are often used interchangeably. There are many borderline cases, however, and also numerous examples where the optical and X-ray classifications appear to be in disagreement. In this article we revisit the relation between optical obscuration and X-ray absorption in active galactic nuclei (AGNs). We make use of our "dust colour" method to derive the optical obscuration A V , and consistently estimated X-ray absorbing columns using 0.3-150 keV spectral energy distributions. We also take into account the variable nature of the neutral gas column N H and derive the Seyfert subclasses of all our objects in a consistent way. We show in a sample of 25 local, hard-X-ray detected Seyfert galaxies (log L X /(erg/s) ≈ 41.5−43.5) that there can actually be a good agreement between optical and X-ray classification. If Seyfert types 1.8 and 1.9 are considered unobscured, the threshold between X-ray unabsorbed and absorbed should be chosen at a column N H = 10 22.3 cm −2 to be consistent with the optical classification. We find that N H is related to A V and that the N H /A V ratio is approximately Galactic or higher in all sources, as indicated previously. However, in several objects we also see that deviations from the Galactic ratio are only due to a variable X-ray column, showing that (1) deviations from the Galactic N H /A V can be simply explained by dust-free neutral gas within the broad-line region in some sources; that (2) the dust properties in AGNs can be similar to Galactic dust and that (3) the dust colour method is a robust way to estimate the optical extinction towards the sublimation radius in all but the most obscured AGNs.

X-RAY WARM ABSORPTION AND EMISSION IN THE POLAR-SCATTERED SEYFERT 1 GALAXY Mrk 704

The Astrophysical Journal, 2011

We present a detailed study of the ionised environment of the Seyfert 1 galaxy Mrk 704 using medium and high resolution X-ray spectra obtained with a long XMM-Newton observation. The 0.3 − 10 keV continuum, well described by a power-law (Γ ≈ 1.86) and two blackbodies (kT ≈ 0.085 and 0.22 keV), is found to be affected by a neutral partial covering absorption (N H ≈ 10 23 cm −2 , covering fraction ≈ 0.22) and two warm absorber components. We identify a low ionisation, ξ ∼ 20 erg cm s −1 , and high outflow velocity, v ∼ 1350 km s −1 , phase producing the O VI and Fe M-shell unresolved-transition array (UTA). An additional high ionisation warm absorbing phase with ξ ∼ 500 erg cm s −1 and low outflow velocity, v ∼ 540 km s −1 , gives rise to absorption features due to O VII, O VIII, N VI, N VII and C VI. We also detected weak emission lines of He-like triplets from O VII and N VI ions, thus making Mrk 704 a Seyfert 1 galaxy with both warm absorption and emission. The emission lines are well described by two warm emitting, photoionised media with different densities but comparable ξ, suggesting discrete clouds of warm emission. The high density phase (n e ∼ 10 13 cm −3 ) responsible for the resonance lines appears to outflow at high velocity ∼ 5000 km s −1 . The low velocity, low density phase is likely similar to the X-ray line emitting regions found in Seyfert 2 galaxies. The physical conditions of warm emitters and warm absorbers suggest that these clouds are similar but observed in absorption along our line of sight and in emission at other lines of sight. The unique line of sight passing close to the torus opening angle is likely responsible for the neutral partial covering absorption and our view of emission lines due to the suppressed continuum in this polar scattered Seyfert 1 galaxy.

X-ray properties of a sample of polar-scattered Seyfert galaxies

Arxiv preprint arXiv: …, 2007

Abstract: We present the results on an XMM-Newton systematic analysis of a sample of nine Seyfert 1 galaxies. When observed in polarised light, the spectra of the selected sources are similar to those of Seyfert 2 galaxies. This peculiarity strongly suggests that these AGN are ...

The soft X-ray absorption lines of the Seyfert 1 galaxy MCG-6-30-15

Monthly Notices of the Royal Astronomical Society, 2004

The absorption lines in the soft X-ray spectrum of MCG-6-30-15 are studied using the Reflection Grating Spectrometer data from the 2001 XMM-Newton 320 ks observation. A line search of the full time-averaged spectrum reveals 51 absorption lines and one emission line. The equivalent widths of the lines are measured and the majority of the lines identified. We find lines produced by a broad range of charge states for several elements, including almost all the charge states of oxygen and iron, suggesting a broad range of ionization parameters is present in the warm absorber. The equivalent widths of the lines are broadly consistent with the best fitting warm absorber models from Turner et al. (2003). The equivalent widths of the absorption lines allow confidence limits on the column density of the species to be determined. For O VII a column density of 10 18.36-10 18.86 cm −2 is found. This column density of O VII, when combined with the inferred Fe I absorption, is sufficient to explain the drop in flux at 0.7 keV as being due to absorption from the warm absorber. Fitting O I K-edge absorption to the spectrum reveals a column of 10 17.51 − 10 17.67 cm −2 of O I, suggesting an Fe:O ratio of ∼1:2, consistent with the neutral iron being in the form of iron oxide dust. Variability is seen in a few absorption lines, but the majority of the absorption features, including the prominent absorption edges, stay constant throughout the observation despite variability in the continuum flux.

X-ray spectral survey with XMM–Newton of a complete sample of nearby Seyfert galaxies

Astronomy and Astrophysics, 2006

Results obtained from an X-ray spectral survey of nearby Seyfert galaxies using XMM-Newton are reported. The sample was optically selected, well defined, complete in B magnitude, and distance limited: it consists of the nearest (D < ∼ 22 Mpc) 27 Seyfert galaxies (9 of type 1, 18 of type 2) taken from the Ho et al. (1997) sample. This is one of the largest atlases of hard X-ray spectra of low-luminosity active galaxies ever assembled. All nuclear sources except two Seyfert 2s are detected between 2 and 10 keV, half for the first time ever, and average spectra are obtained for all of them. Nuclear luminosities reach values down to 10 38 erg s −1. The shape of the distribution of X-ray parameters is affected by the presence of Compton-thick objects (> ∼ 30% among type 2s). The latter have been identified either directly from their intense FeK line and flat X-ray spectra, or indirectly with flux diagnostic diagrams which use isotropic indicators. After taking into account these highly absorbed sources, we find that (i) the intrinsic X-ray spectral properties (i.e., spectral shapes and luminosities above 2 keV) are consistent between type 1 and type 2 Seyferts, as expected from "unified models", (ii) Seyfert galaxies as a whole are distributed fairly continuously over the entire range of NH, between 10 20 and 10 25 cm −2 , and (iii) while Seyfert 1s tend to have lower NH and Seyfert 2s tend to have the highest, we find 30% and 10% exceptions, respectively. Overall the sample is of sufficient quality to well represent the average intrinsic X-ray spectral properties of nearby active galactic nuclei, including a proper estimate of the distribution of their absorbing columns. Finally, we conclude that, with the exception of a few cases, the present study agrees with predictions of unified models of Seyfert galaxies, and extends their validity down to very low luminosities.

Broad-band study of hard X-ray-selected absorbed active galactic nuclei

Monthly Notices of the Royal Astronomical Society, 2012

In this paper we report on the broadband X-ray properties of a complete sample of absorbed Seyfert galaxies hard X-ray selected with INTEGRAL. Our sample is composed of 33 sources, of which 15 are newly discovered AGN above 20 keV (IGR sources) while 18 are already known type 2 AGN ("known"). For 17 sources (15 IGR + 2 "known" sources) we have performed a broadband analysis using both XMM-Newton, and INTEGRAL-IBIS data. To have a full view of the complete sample we have then complemented the analysis of the 16 remaining sources with already existing broadband studies in the same range. The high quality broadband spectra are well reproduced with an absorbed primary emission with a high energy cutoff and its scattered fraction below 2-3 keV, plus the Compton reflection features (Compton hump and Fe line emission). This study permitted a very good characterization of the primary continuum and, in turn, of all the spectral features. A high energy cutoff is found in 30% of the sample, with an average value below 150 keV, suggesting that this feature has to be present in the X-ray spectra of obscured AGN. The hard X-ray selection favours the detection of more obscured sources, with the log N H average value of 23.15 (standard deviation of 0.89). The diagnostic plot N H vs F corr (2-10 keV)/F(20-100 keV) allowed the isolation of the Compton thick objects, and may represent a useful tool for future hard X-ray observations of newly discovered AGN. We are unable to associate the reflection components (both continuum and Fe line) with the absorbing gas as a torus (as envisaged in the Unified Model), a more complex scenario being necessary. In the Compton thin 2 A. De Rosa et al. sources, a fraction (but not all) of the Fe K line needs to be produced in a gas located closer to the black hole than the Compton thick torus, and this is possibly associated with the optical Broad Line Region, responsible also for the absorption. We still need a Compton thick medium (not intercepting the line of sight) likely associated to a torus, which contributes to the Fe line intensity and produces the observed reflection continuum above 10 keV. The so-called Iwasawa-Taniguchi effect can not be confirmed with our data. Finally, the comparison with a sample of unobscured AGN shows that, type 1 and type 2 (once corrected for absorption) Seyfert are characterized by the same nuclear/accretion properties (luminosity, bolometric luminosity, Eddington ratio), supporting the "unified" view.

Title Soft x-ray properties of seyfert galaxies in the rosat all-sky survey Permalink

2013

We present the results of ROSAT All–Sky Survey observations of Seyfert and IR–luminous galaxies from the Extended 12 μm Galaxy Sample and the optically–selected CfA Sample. Detections are available for 80% (44/55) of the Seyfert 1s and 34% (23/67) of the Seyfert 2s in the 12 μm sample, and for 76% (26/34) of the Seyfert 1s and 38% (6/16) of the Seyfert 2s in the CfA sample. Roughly half of the Seyferts (mostly Seyfert 1s) have been fitted to an absorbed power–law model, yielding an average photon index of Γ=2.26±0.11 for 43 Seyfert 1s and Γ=2.45±0.18 for 10 Seyfert 2s, with both types having a median value of 2.3. The soft X–ray luminosity correlates with the 12 μm luminosity, with Seyfert 1s having relatively more soft X–ray emission than Seyfert 2s of similar mid–infrared luminosities, by a factor of 1.6 ± 0.3. Several physical interpretations of these results are discussed, including the standard unified model for Seyfert galaxies. Infrared–luminous non–Seyferts are shown to have...

Nuclear obscuration and scattering in Seyfert 2 galaxies

Astronomy and Astrophysics, 2001

We study the relation between gaseous absorbing column density (N H), infrared colors and detectability of the broad lines in a large sample of Seyfert 2 galaxies(Sy2s). We confirm that Sy2s without polarized broad lines tend to have cooler 60µm/25µm colors; this correlation was previously ascribed to the effect of obscuration towards the nuclear region. We find some evidence that Sy2s without polarized broad lines have larger absorbing column density (N H) and that a fraction of them are characterized by dust lanes crossing their nuclei. However, we find that the IR colors do not correlate with N H , in disagreement with the obscuration scenario. Also, Sy2s without polarized broad lines follow the same radio-FIR relation as normal and starburst galaxies, at variance with Sy2s with polarized broad lines. These results indicate that the lack of broad lines in the polarized spectrum of Sy2s is mostly due to the contribution/dilution from the host galaxy or from a circumnuclear starburst, though at a lower extent the obscuration toward the nuclear region also plays a role.