A<i>Chandra</i>X‐Ray Study of NGC 1068. I. Observations of Extended Emission

Young, A. J.; Wilson, A. S.; Shopbell, P. L.

doi:10.1086/321561

Cited by 155 publications

(216 citation statements)

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“…12b,c is spatially resolved. Young et al (2001) confirmed the reality of this extended component and concluded that the latter cannot be attributed to scattering by the telescope PSF. The compact source, located on the AGN, is surrounded by lowerlevel emission that pervades the molecular material of the CND out to r ∼ 2−3 .…”

Section: X-ray Emission In Ngc 1068mentioning

confidence: 62%

“…12a the subarcsec resolution X-ray image of NGC 1068 obtained in the 0.25−7.50 keV band with Chandra (contours) on the SiO map (color scale). The X-ray image has been taken from the 3.2 s frame time data published by Young et al (2001). The 0.25−7.50 keV band image incorporates the contribution from soft to hard X-rays and includes both continuum and line emission.…”

Section: X-ray Emission In Ngc 1068mentioning

confidence: 99%

“…12a. This outer emission takes the shape of a complex spiral-like structure that extends out to r ∼ 30−40 (see Young et al 2001 for a detailed description). The brightest region in X-ray emission corresponds with the compact AGN source.…”

Section: X-ray Emission In Ngc 1068mentioning

confidence: 99%

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Molecular gas chemistry in AGN

García‐Burillo

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Fuente

et al. 2010

A&A

126

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Context. This paper is part of a multi-species survey of line emission from the molecular gas in the circum-nuclear disk (CND) of the Seyfert 2 galaxy NGC 1068. Unlike in other active galaxies, the intensely star-forming regions in NGC 1068 and the CND can be resolved with current instrumentation. This makes this galaxy an optimal test-bed to probe the effects of AGN on the molecular medium at ∼100 pc scales. Aims. Single-dish observations have provided evidence that the abundance of silicon monoxide (SiO) in the CND of NGC 1068 is enhanced by 3-4 orders of magnitude with respect to the values typically measured in quiescent molecular gas in the Galaxy. We aim at unveiling the mechanism(s) underlying the SiO enhancement. Methods. We have imaged the emission of the SiO(2−1) (86.8 GHz) and CN(2−1) (226.8 GHz) lines in NGC 1068 at ∼150 pc and 60 pc spatial resolution with the IRAM Plateau de Bure interferometer (PdBI). We have also obtained complementary IRAM 30 m observations of HNCO and methanol (CH 3 OH) lines. These species are known as tracers of shocks in the Galaxy. Results. SiO is detected in a disk of ∼400 pc size around the AGN. SiO abundances in the CND of ∼(1−5)×10 −9 are about 1−2 orders of magnitude above those measured in the starburst ring. The overall abundance of CN in the CND is high: ∼(0.2−1) × 10 −7 . The abundances of SiO and CN are enhanced at the extreme velocities of gas associated with non-circular motions close to the AGN (r < 70 pc). On average, HNCO/SiO and CH 3 OH/SiO line ratios in the CND are similar to those measured in prototypical shocked regions in our Galaxy. Yet the strength and abundance of CN in NGC 1068 can be explained neither by shocks nor by photondominated region (PDR) chemistry. Abundances measured for CN and SiO and the correlation of CN/CO and SiO/CO ratios with hard X-ray irradiation suggest that the CND of NGC 1068 has become a giant X-ray-dominated region (XDR). Conclusions. The extreme properties of molecular gas in the circum-nuclear molecular disk of NGC 1068 result from the interplay between different processes directly linked to nuclear activity. The results presented here highlight in particular the footprint of shocks and X-ray irradiation on the properties of molecular gas in this Seyfert. Whereas XDR chemistry offers a simple explanation for CN and SiO in NGC 1068, the relevance of shocks deserves further scrutiny. The inclusion of dust grain chemistry would help solve the controversy regarding the abundances of other molecular species, like HCN, which are under-predicted by XDR models.

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Section: X-ray Emission In Ngc 1068mentioning

confidence: 62%

Section: X-ray Emission In Ngc 1068mentioning

confidence: 99%

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Molecular gas chemistry in AGN

García‐Burillo

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et al. 2010

A&A

126

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“…10 and 11). Di †use [O III] line emission is seen from an approximately biconical region centered on the nucleus, and in this regard the X-ray and [O III] emissions appear well correlated (as also found in NGC 1068 [Young, Wilson, & Shopbell 2001], where the ionization of the X-rayÈemitting gas is dominated by photoionization [Paerels et al 2000]). …”

Section: Comparison With Observations At Other Wavelengthsmentioning

confidence: 72%

AChandraX‐Ray Study of Cygnus A. II. The Nucleus

Young¹,

Wilson²,

Terashima³

et al. 2002

ApJ

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We report Chandra Advanced CCD Imaging Spectrometer and quasi-simultaneous Rossi X-Ray T iming Explorer (RXT E) observations of the nearby, powerful radio galaxy Cygnus A, with the present paper focusing on the properties of the active nucleus. In the Chandra observation, the hard ([a few keV) X-ray emission is spatially unresolved with a size (1.5 kpc, km s~1 Mpc~1) and coin-[1A H 0 \ 50 cides with the radio and near-infrared nuclei. In contrast, the soft (\2 keV) emission exhibits a bipolar nebulosity that aligns with the optical bipolar continuum and emission-line structures and approximately with the radio jet. In particular, the soft X-ray emission corresponds very well with the [O III] j5007 and Ha ] [N II] jj6548, 6583 nebulosity imaged with Hubble Space T elescope. At the location of the nucleus, there is only weak soft X-ray emission, an e †ect that may be intrinsic or result from a dust lane that crosses the nucleus perpendicular to the source axis. The spectra of the various X-ray components have been obtained by simultaneous Ðts to the six detectors. The compact nucleus is detected to 100 keV and is well described by a heavily absorbed power-law spectrum with (similar to other ! h \ 1.52~0 .12 0.12 narrow-line radio galaxies) and equivalent hydrogen column cm~2. This N H (nuc) \ 2.0~0 .2 0.1 ] 1023 column is compatible with the dust obscuration to the near-infrared source for a normal gas-to-dust ratio. The soft (\2 keV) emission from the nucleus may be described by a power-law spectrum with the same index (i.e., although direct Ðts suggest a slightly larger value for Narrow emission lines ! l \ ! h ), ! l . from highly ionized neon and silicon, as well as a "" neutral ÏÏ Fe Ka line, are detected in the nucleus and its vicinity kpc). The equivalent width (EW) of the Fe Ka line eV) is in good agreement (r [ 2 (182~5 4 40 with theoretical predictions for the EW versus relationship in various geometries. An Fe K edge N H (nuc) is also seen. The RXT E observations indicate a temperature of keV for the cluster gas kT \ 6.9~1 .0 0.3 (discussed in Paper III of this series) and cluster emission lines of Fe Ka and Fe Kb and/or Ni Ka.We consider the possibility that the extended soft X-ray emission is electron-scattered nuclear radiation. Given that 1% of the unabsorbed 2È10 keV nuclear radiation would have to be scattered, the necessary gas column cm~2] would absorb the X-rays rather than scatter [N H (scattering)^3.5 ] 1022 them if the gas is cold. Thus, the scattering plasma must be highly ionized. If this ionization is achieved through photoionization by the nucleus, the ionization parameter m [ 1 ergs cm s~1 and the electron density cm~3 given the observed distance of the soft X-ray emission from the nucleus. The elecn e^6 tron column density inferred from the X-ray observations is much too low to account for the extended optical scattered light, strongly suggesting that the polarized optical light is scattered by dust. The presence of highly ionized Ne lines in the soft X-ray spectrum requires 20...

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“…Strongly absorbed Seyfert galaxies are the perfect targets for studying the properties of the cold reprocessor, because the Compton reflection features are not diluted by the presence of a strong primary continuum. Indeed, Young, Wilson & Shopbell (2001) firstly showed that the neutral iron Kα emitter is extended in NGC 1068. Such a material is well imaged by the ACIS-S and extends up to ∼20 arcsec to the northeast and southwest which, at the redshift of the source, corresponding to about 2.2 kpc.…”

Section: Equivalent Width Of the Iron Kα Linementioning

confidence: 99%

Spatially resolved Fe K spectroscopy of NGC 4945

Marinucci

Bianchi

Fabbiano

et al. 2017

Monthly Notices of the Royal Astronomical Society

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We present the imaging and spectroscopic analysis of the combined Chandra ACIS-S observations of the Compton-thick Seyfert 2 galaxy NGC 4945. We performed a spatially-resolved spectroscopy of the circumnuclear environment of the source, picturing the innermost 200 parsecs around the highly absorbed nucleus. The additional 200 ks ACIS-S data with respect to the previous campaign allowed us to map with even greater detail the central structure of this source and to discover an enhanced iron emission in the innermost nuclear region, with respect to the associated Compton reflection continuum. We revealed that the Equivalent Width of the iron Kα line is spatially variable (ranging from 0.5 to 3 keV), on scales of tens of parsecs, likely due to the ionization state and orientation effects of the reprocessing material, with respect to the central X-ray illuminating source. A clump of highly ionized Fe xxv He-α is also detected, 40 parsecs east to the nucleus. When observations taken years apart are considered, the central unresolved reflected emission is found to remain constant.

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AChandraX‐Ray Study of NGC 1068. I. Observations of Extended Emission

Cited by 155 publications

References 47 publications

Molecular gas chemistry in AGN

Molecular gas chemistry in AGN

AChandraX‐Ray Study of Cygnus A. II. The Nucleus

Spatially resolved Fe K spectroscopy of NGC 4945

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