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Recent studies indicate that the region of emission of coronal lines observed in some active galactic nuclei is located in the internal face of the obscurant toroid; however, there are numerous examples of Seyfert 2 galaxies with significant coronal emission. To clarify this anomaly, here we give some insights about the location of the coronal line region (CLR) and determine the physical conditions of the coronal gas in this type of galaxies. We executed a SQL query in the Sloan Digital Sky Survey (SDSS-DR14) database to select various Seyfert 2 galaxies under the following criteria: 3

Recent studies indicate that the region of emission of coronal lines observed in some active galactic nuclei is located in the internal face of the obscurant toroid; however, there are numerous examples of Seyfert 2 galaxies with significant coronal emission. To clarify this anomaly, here we give some insights about the location of the coronal line region (CLR) and determine the physical conditions of the coronal gas in this type of galaxies. We executed a SQL query in the Sloan Digital Sky Survey (SDSS-DR14) database to select various Seyfert 2 galaxies under the following criteria: 3

We present the X-ray spectral analysis of the 1855 extragalactic sources in the Chandra COSMOS-Legacy survey catalog having more than 30 net counts in the 0.5-7 keV band. 38% of the sources are optically classified Type 1 active galactic nuclei (AGN), 60% are Type 2 AGN and 2% are passive, low-redshift galaxies. We study the distribution of AGN photon index and of the intrinsic absorption N(H,z) based on the sources optical classification: Type 1 have a slightly steeper mean photon index than Type 2 AGN, which on the other hand have average intrinsic absorption ~3 times higher than Type 1 AGN. We find that ~15% of Type 1 AGN have N(H,z)>1E22 cm^(-2), i.e., are obscured according to the X-ray spectral fitting; the vast majority of these sources have L(2-10keV)>$1E44 erg/s. The existence of these objects suggests that optical and X-ray obscuration can be caused by different phenomena, the X-ray obscuration being for example caused by dust-free material surrounding the inner part of the nuclei. ~18% of Type 2 AGN have N(H,z), Comment: 23 pages, 16 figures. Accepted for publication on ApJ

A fraction of active galactic nuclei do not show the classical Seyfert-type signatures in their optical spectra, i.e. they are optically "elusive". X-ray observations are an optimal tool to identify this class of objects. We combine new Chandra observations with archival X-ray data in order to obtain a first estimate of the fraction of elusive AGN in local galaxies and to constrain their nature. Our results suggest that elusive AGN have a local density comparable to or even higher than optically classified Seyfert nuclei. Most elusive AGN are heavily absorbed in the X-rays, with gas column densities exceeding 10^24 cm^-2, suggesting that their peculiar nature is associated with obscuration. It is likely that in elusive AGN, the nuclear UV source is completely embedded and the ionizing photons cannot escape, which prevents the formation of a classical Narrow Line Region. Elusive AGN may contribute significantly to the 30 keV bump of the X-ray background., Comment: accepted for publication in MNRAS Letters, 6 pages, 3 figures, typos and references corrected

We present Nustar 3-40 keV observations of the optically selected Type 2 quasar (QSO2) SDSS J1034+6001 or Mrk 34. The high-quality hard X-ray spectrum and archival XMM-Newton data can be fitted self-consistently with a reflection-dominated continuum and strong Fe Kalpha fluorescence line with equivalent-width >1 keV. Prior X-ray spectral fitting below 10 keV showed the source to be consistent with being obscured by Compton-thin column densities of gas along the line-of-sight, despite evidence for much higher columns from multiwavelength data. NuSTAR now enables a direct measurement of this column, and shows that Nh lies in the Compton-thick (CT) regime. The new data also show a high intrinsic 2-10 keV luminosity of L_{2-10}~10^{44} erg/s, in contrast to previous low-energy X-ray measurements for which L_{2-10}, Comment: ApJ, in press

Stellar bars can lead to gas inflow toward the center of a galaxy and stimulate nuclear star formation. However, there is no compelling evidence on whether they also feed a central supermassive black hole: by measuring the fractions of barred active and inactive galaxies, previous studies have yielded conflicting results. In this paper, we aim to understand the lack of observational evidence for bar-driven active galactic nucleus (AGN) activity by studying a sample of 41 nearby (d < 35 Mpc) barred galaxies from the Spitzer Survey for Stellar Structure in Galaxies. We use Chandra observations to measure nuclear 2-10 keV X-ray luminosities and estimate Eddington ratios, together with Spitzer 3.6 mu m imaging to quantify the strength of the stellar bar in two independent ways: (1) from its structure, as traced by its ellipticity and boxiness, and (2) from its gravitational torque Q(b), taken as the maximum ratio of the tangential force to the mean background radial force. In this way, rather than discretizing the presence of both stellar bars and nuclear activity, we are able to account for the continuum of bar strengths and degrees of AGN activity. We find nuclear X-ray sources in 31 out of 41 galaxies with median X-ray luminosity and Eddington ratio of L-X = 4.3 x 10(38) erg s(-1) and L-bol/L-Edd = 6.9 x 10(-6), respectively, consistent with low-luminosity AGN activity. Including upper limits for those galaxies without nuclear detections, we find no significant correlation between any of the bar strength indicators and the degree of nuclear activity, irrespective of galaxy luminosity, stellar mass, Hubble type, or bulge size. Strong bars do not favor brighter or more efficient nuclear activity, implying that at least for the low-luminosity regime, supermassive black hole fueling is not closely connected to large-scale features.

Chandra observations of a complete, flux-limited sample of 38 high-redshift (1 < z < 2), low-frequency-selected (and so unbiased in orientation) 3CRR radio sources are reported. The sample includes 21 quasars (=broad-line radio galaxies) and 17 narrow-line radio galaxies (NLRGs) with matched 178 MHz radio luminosity (log LR (5 GHz) ∼44-45). The quasars have high radio core fraction, high X-ray luminosities (log L X ∼45-46), and soft X-ray hardness ratios (HR ∼-0.5) indicating low obscuration. The NLRGs have lower core fraction, lower apparent X-ray luminosities (log L X ∼43-45), and mostly hard X-ray hardness ratios (HR >0) indicating obscuration (N H ∼1022-1024 cm -2). These properties and the correlation between obscuration and radio core fraction are consistent with orientation-dependent obscuration as in unification models. About half the NLRGs have soft X-ray hardness ratios and/or a high [O III] emission line to X-ray luminosity ratio suggesting obscuration by Compton thick (CT) material so that scattered nuclear or extended X-ray emission dominates (as in NGC 1068). The ratios of unobscured to Compton-thin (1022 cm-2 < N H (int) 24 cm-2) to CT (N H (int) >1.5 × 1024 cm-2) is 2.5:1.4:1 in this high-luminosity, radio-selected sample. The obscured fraction is 0.5, higher than is typically reported for active galactic nuclei at comparable luminosities from multi-wavelength surveys (0.1-0.3). Assuming random nuclear orientation, the unobscured half-opening angle of the disk/wind/torus structure is ∼60° and the obscuring material covers 30°, ∼12° of which is CT. The multi-wavelength properties reveal that many NLRGs have intrinsic absorption 10-1000 × higher than indicated by their X-ray hardness ratios, and their true L X values are ∼10-100× larger than the hardness-ratio absorption corrections would indicate.