A deep ROSAT survey XV. the average QSO spectrum and its evolution

Details A deep ROSAT survey XV. the average QSO spectrum and its evolution A deep ROSAT survey XV. the average QSO spectrum and its evolution

2000-01-11

arxiv.org/abs/astro-ph/0001179v1

Astronomy and Astrophysics

Astrophysics

7 pages, to appear in the MNRAS

Scientific paper

10.1046/j.1365-8711.2000.03352.x

Using a sample of 165 X-ray selected QSOs from seven deep ROSAT fields we investigate the X-ray spectral properties of an ``average''radio-quiet broad line QSO as a function of redshift. The QSO stacked spectra, in the observers 0.1-2 keV band, in five redshift bins over the range 0.11.0) the single power-law model gives an acceptable fit to the data over the full energy band, at lower redshifts the spectra need a second component at low energies, a `soft excess'. Inclusion of a simple model for the soft excess, i.e. a black-body component (kT~100 eV), results in a significant improvement to the model fit, and yields power-law slopes of 1.8-1.9, for all redshift bins. This power-law is not inconsistent, within the error bars, with those of nearby AGN in the 2-10 keV band, suggesting that the same intrinsic power-law slope may continue from 10 keV down to below 0.5 keV. We caution that there is a possibility that the spectral upturn observed may not represent a real physical component but could be due to co-adding spectra with a large dispersion in spectral indices. Regardless of the origin of the soft excess, the average QSO spectrum has important consequences for the origin of the X-ray background: the average spectra of the typical, faint, high redshift QSO are significantly steeper than the spectrum of the X-ray background extending the spectral paradox into the soft 0.1-2 keV X-ray band.

Affiliated with

Also associated with

No associations

Rating

A deep ROSAT survey XV. the average QSO spectrum and its evolution 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 A deep ROSAT survey XV. the average QSO spectrum and its evolution, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and A deep ROSAT survey XV. the average QSO spectrum and its evolution will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFWR-SCP-O-364403