The instrinsic UV/soft x-ray spectrum of quasars
| dc.creator | Haardt, Francesco | |
| dc.creator | Madau, Piero | |
| dc.date | 1996-09-06 | |
| dc.date.accessioned | 2026-07-07T02:21:53Z | |
| dc.date.available | 2026-07-07T02:21:53Z | |
| dc.description | The detection of a HeII absorption trough in the spectra of three high-redshift quasars provides new constraints on the spectral shape of the UV extragalactic background. The relative strengths of the observed flux decrements at the rest-frame wavelengths of 1216 and 304 A require a relatively soft radiation field at 4 ryd compared to 1 ryd. If the ionizing metagalactic flux is dominated by the integrated light from QSOs, and the HeII reionization of the universe was completed well before z~3, then the UV/soft X-ray spectrum of individual quasars at these epochs must, once the cosmological ``filtering'' through material along the line of sight is taken into account, satisfy similar constraints on the average. We model the propagation of AGN-like ionizing radiation through the intergalactic medium using CUBA, a numerical code developed in our prior work. We show that, in order to explain the reported HeII absorption, any thermal component responsible for the ``soft X-ray excess'' observed in the spectra of AGNs at z<0.3 must, at z~3, have a typical temperature >80 eV, and a luminosity not exceeding 20% of that of the ``UV bump''. | |
| dc.description | 2 pages, PASP latex [11pt,paspconf,epsf], + 1.ps figure To be published in the proceedings of 163 IAU Conference. Also available at http://fy.chalmers.se/~haardt/personal/curr.html | |
| dc.identifier | https://arxiv.org/abs/astro-ph/9609057 | |
| dc.identifier | http://arxiv.org/abs/astro-ph/9609057 | |
| dc.identifier.uri | http://salesiana.dossiersoluciones.com/handle/123456789/10669 | |
| dc.subject | Astrophysics | |
| dc.title | The instrinsic UV/soft x-ray spectrum of quasars | |
| dc.type | text |