Query : 2003A&A...409..503B

2003A&A...409..503B - Astronomy and Astrophysics, volume 409, 503-509 (2003/10-2)

On the location and composition of the dust in the MCG-6-30-15 warm absorber.


Abstract (from CDS):

The warm absorber observed in the Seyfert 1 galaxy MCG-6-30-15 is known to consist of at least two zones and very likely contains dust. Hubble Space Telescope images of MCG-6-30-15 show a dust lane crossing the galaxy just below the nucleus. In this paper, we argue that this dust lane is responsible for the observed reddening of the nuclear emission and the Fe i edge hinted at in the Chandra spectrum of MCG-6-30-15. We further suggest that the gas within the dust lane can comprise much of the low ionization component (i.e., the one contributing the O vii edge) of the observed warm absorber. Moreover, placing the warm absorbing material at such distances (hundreds of pc) can account for the small outflow velocities of the low ionization absorption lines as well as the constancy of the O vii edge. Photoionization models of a dusty interstellar gas cloud (with a column appropriate for the reddening toward MCG-6-30-15) using a toy Seyfert 1 spectral energy distribution show that it is possible to obtain a significant O vii edge (τ∼0.2) if the material is ∼150pc from the ionizing source. For MCG-6-30-15, such a distance is consistent with the observed dust lane. We emphasize the point first made by Kraemer et al.: dusty interstellar material will likely contribute to the warm absorber, and should be included in spectral modeling. The current data on MCG-6-30-15 is unable to constrain the dust composition within the warm absorber. Astronomical silicate is a viable candidate, but there are indications of a very low O abundance in the dust, which is inconsistent with a silicate origin. If true, this may indicate that there were repeated cycles of grain destruction and growth from shocks in the interstellar medium of MCG-6-30-15. Pure iron grains are an unlikely dust constituent due to the limit on their abundance in the Galaxy, yet they cannot be ruled out. The high column densities inferred from the highly ionized zone of the warm absorber implies that this gas is dust-free.

Abstract Copyright:

Journal keyword(s): dust, extinction - galaxies: active - galaxies: Seyfert - galaxies: individual: MCG-6-30-15 - X-rays: galaxies - X-rays: ISM

Simbad objects: 5

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Number of rows : 5
N Identifier Otype ICRS (J2000)
ICRS (J2000)
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2023
1 NGC 3227 GiP 10 23 30.5765149296 +19 51 54.282206700   12.61 11.79     ~ 1643 1
2 ESO 383-35 Sy1 13 35 53.7691256160 -34 17 44.160716796   13.89 13.61 8.9   ~ 1451 0
3 IRAS 13349+2438 Sy1 13 37 18.7199358192 +24 23 03.319883484     15.0     ~ 380 0
4 HD 226868 HXB 19 58 21.6757355952 +35 12 05.784512688 9.38 9.72 8.91 8.42   O9.7Iabpvar 4188 0
5 NAME MR 2251-178 Sy1 22 54 05.8858611984 -17 34 55.402233708   14.99 14.36 15.12   ~ 413 3

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