C.D.S. - SIMBAD4 rel 1.7 - 2021.02.25CET19:52:11

2002A&A...396..761B - Astronomy and Astrophysics, volume 396, 761-772 (2002/12-4)

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


Abstract (from CDS):

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 (kTe ∼ few eV) photoionized plasma. We confirm the conclusions of Kinkhabwala et al. (2002ApJ...575..732K), 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 30Å 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.

Abstract Copyright:

Journal keyword(s): galaxies: individual: NGC 1068 - galaxies: Seyfert - quasars: emission lines - X-rays: galaxies

Simbad objects: 3

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Number of rows : 3

N Identifier Otype ICRS (J2000)
ICRS (J2000)
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2021
1 M 77 GiP 02 42 40.771 -00 00 47.84 9.70 9.61 8.87 10.1 9.9 ~ 4176 2
2 2RE J1337+244 Sy1 13 37 18.7198121987 +24 23 03.320690345     15.0     ~ 364 0
3 NGC 5548 Sy1 14 17 59.5401093128 +25 08 12.600227883   14.35 13.73     ~ 2444 0

    Equat.    Gal    SGal    Ecl

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