Astronomy and Astrophysics – Astrophysics – Cosmology and Extragalactic Astrophysics
Scientific paper
2011-10-04
Astronomy and Astrophysics
Astrophysics
Cosmology and Extragalactic Astrophysics
MNRAS in press. Revised version has significant improvements thanks to anonymous referee and various colleagues, especially di
Scientific paper
I summarise and analyse key problems with observations of the UV bump in Active Galactic Nuclei (AGN), and especially the accretion disc interpretation - the temperature problem, the ionisation problem, the timescale problem, and the co-ordination problem - and suggest that all these problems can be solved if, in addition to the accretion disc, there is a population of cold, thick clouds at approximately 30R_S which reprocess the intrinsic continuum. Exploring cloud parameter space, I find that clouds with density n~10^12 cm^-3 and column N_H >4 X 10^24 cm^-2 reflect most of the intrinsic continuum, but convert a substantial fraction of the EUV luminosity into lines, dominated by Ly-beta and HeII Ly-alpha. When velocity-blurred, this makes a false continuum peak at ~1100A which fits the observed SED well, but turns back up in the FUV to make a hard EUV SED, as required by ionisation models. I argue that the observed UV variability is dominated by this component of fixed shape, possibly due to changes of covering factor. The amount of mass required is small, so it is not necessary to disrupt the disc, but only to make an unstable and inhomogeneous atmosphere. The proposed clouds may be related to those suggested by several X-ray phenomena (X-ray reflection components, high-velocity outflows, Compton thick partial covering) but are not the same, leading to a picture with a wide range of inhomogeneous structures at different radii.
No associations
LandOfFree
The UV peak in Active Galactic Nuclei : a false continuum from blurred reflection ? does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with The UV peak in Active Galactic Nuclei : a false continuum from blurred reflection ?, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and The UV peak in Active Galactic Nuclei : a false continuum from blurred reflection ? will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-324399