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The soft X-ray spectrum from NGC 1068 observed with LETGS on Chandra

Brinkman, A. C. and Kaastra, J. S. and van der Meer, R. L. J. and Kinkhabwala, A. and Behar, E. and Kahn, S. M. and Paerels, F. B. S. and Sako, M. (2002) The soft X-ray spectrum from NGC 1068 observed with LETGS on Chandra. Astronomy & Astrophysics, 396 (3). pp. 761-772. ISSN 0004-6361. doi:10.1051/0004-6361:20020918.

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Using the combined spectral and spatial resolving power of the Low Energy Transmission Grating (LETGS) on board Chandra, we obtain separate spectra from the bright central source of NGC 1068 (Primary region), and from a fainter bright spot 4” to the NE (Secondary region). Both spectra are dominated by discrete line emission from H- and He-like ions of C through S, and from Fe L-shell ions, but also include narrow radiative recombination continua (RRC), indicating that most of the observed soft X-ray emission arises in low-temperature (kT_e ~ few eV) photoionized plasma. We confirm the conclusions of Kinkhabwala et al. ([CITE]), based on XMM-Newton Reflection Grating Spectrometer (RGS) observations, that the entire nuclear spectrum can be explained by recombination/radiative cascade following photoionization, and radiative decay following photoexcitation, with no evidence for the presence of hot, collisionally ionized plasma. In addition, we show that this same model also provides an excellent fit to the spectrum of the Secondary region, albeit with radial column densities roughly a factor of three lower, as would be expected given its distance from the source of the ionizing continuum. The remarkable overlap and kinematical agreement of the optical and X-ray line emission, coupled with the need for a distribution of ionization parameter to explain the X-ray spectra, collectively imply the presence of a distribution of densities (over a few orders of magnitude) at each radius in the ionization cone. Relative abundances of all elements are consistent with Solar abundance, except for N, which is 2–3 times Solar. Finally, the long wavelength spectrum beyond 30 Å is rich of L-shell transitions of Mg, Si, S, and Ar, and M-shell transitions of Fe. The velocity dispersion decreases with increasing ionization parameter, which has been deduced from the measured line intensities of particularly these long wavelength lines in conjunction with the Fe-L shell lines.

Item Type:Article
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URLURL TypeDescription Paper
Kaastra, J. S.0000-0001-5540-2822
Additional Information:© 2002 ESO. Article published by EDP Sciences. Received 15 April 2002; Accepted 17 June 2002; Published online 05 December 2002. SRON, The National Institute for Space Research, is supported financially by NWO, the Netherlands Organization for Scientific Research. The Columbia University team is supported by NASA. AK acknowledges additional support from an NSF Graduate Research Fellowship and NASA GSRP fellowship. MS was partially supported by NASA through Chandra Postdoctoral Fellowship Award Number PF01-20016 issued by the Chandra X-ray Observatory Center, which is operated by the Smithsonian Astrophysical Observatory for and behalf of NASA under contract NAS8-39073.
Group:TAPIR, Space Radiation Laboratory
Funding AgencyGrant Number
Nederlandse Organisatie voor Wetenschappelijk Onderzoek (NWO)UNSPECIFIED
NSF Graduate Research FellowshipUNSPECIFIED
NASA Graduate Student Research FellowshipUNSPECIFIED
NASA Chandra FellowshipPF01-20016
Subject Keywords:galaxies: individual: NGC 1068 – galaxies: Seyfert – quasars: emission lines – X-rays: galaxies
Issue or Number:3
Record Number:CaltechAUTHORS:20180307-081542726
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Official Citation:The soft X-ray spectrum from NGC 1068 observed with LETGS on Chandra. A. C. Brinkman, J. S. Kaastra, R. L. J. van der Meer, A. Kinkhabwala, E. Behar, S. M. Kahn, F. B. S. Paerels and M. Sako. A&A, 396 3 (2002) 761-772. DOI:
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:85163
Deposited By: Tony Diaz
Deposited On:07 Mar 2018 17:33
Last Modified:15 Nov 2021 20:26

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