2008A&A...483...19L


C.D.S. - SIMBAD4 rel 1.7 - 2020.08.07CEST21:02:08

2008A&A...483...19L - Astronomy and Astrophysics, volume 483, 19-34 (2008/5-3)

EUV spectral energy distribution of quasars restored from associated absorbers.

LEVSHAKOV S.A., AGAFONOVA I.I., REIMERS D., HOU J.L. and MOLARO P.

Abstract (from CDS):

We reconstruct the spectral shape of the quasar ionizing radiation in the extreme-UV range (1Ryd≤E<10Ryd) from the analysis of narrow absorption lines (NAL) of the associated systems. The computational technique for inverse spectroscopic problems - a Monte Carlo Inversion augmented by the spectral shape recovering procedure and modified to account for the incomplete coverage of the light source is used to analyze observations. The ionizing spectra responsible for the ionization structure of the NAL systems require an intensity depression at E>4Ryd which is attributed to the HeII Lyman continuum opacity (τHeIIc∼1). A most likely source of this opacity is a quasar accretion disk wind. The corresponding column density of HI in the wind is estimated as a few times 1016cm–2. This amount of neutral hydrogen should cause a weak continuum depression at λ≲912Å (rest-frame), and a broad and shallow absorption in HI Ly-α. If the metallicity of the wind is high enough, other resonance lines of OVI, NeVI-NeVIII, etc. are expected. In the analyzed QSO spectra we do observe broad (stretching over 1000s.km/s) and shallow (τ≪1) absorption troughs of HI Ly-α and OVI λλ1031, 1037 as well as continuum depressions at λ≲912Å which correspond to N(HI)∼5x1016cm–2. Observational data available in both the UV and X-ray ranges suggest that at least ∼50% of the quasar radiation passes through the gas opaque in the HeII Lyman continuum. This means that the outcoming ionizing spectrum should have a pronounced intensity break at E>4Ryd with the depth of this break depending on the angle with the rotational axis of the accretion disk (the larger the angle the deeper the break). The QSO spectra with a discontinuity at 4Ryd can influence the rate of HeII reionization in the intergalactic medium and partly explain the inhomogeneous (patchy) ionization structure of the intergalactic HeII observed at z∼3.

Abstract Copyright:

Journal keyword(s): cosmology: observations - line: formation - line: profiles - quasars: absorption lines

CDS comments: Paragraph 2.2.1 HE 0141-3432 is a misprint for HE 0141-3932. Paragraph 2.3 HE 2347-4243 is a misprint for HE 2347-4342. Paragraph 3.1 Q0329-325 is a misprint for Q0329-385, HE 0141-1020 is a misprint for HE 1341-1020.

Simbad objects: 8

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Number of rows : 8

N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2020
#notes
1 QSO J0143-3917 QSO 01 43 33.6332299840 -39 17 00.065618732     16.28     ~ 24 0
2 QSO B0329-385 QSO 03 31 06.3780192488 -38 24 04.653743031   17.63 16.92     ~ 75 0
3 QSO B1103+6416 QSO 11 06 10.7342664415 +64 00 09.646278482   16.36 16.16     ~ 59 0
4 QSO J1342-1355 QSO 13 42 58.8724264812 -13 55 59.811090379   19.2 19.2     ~ 20 0
5 QSO J1344-1035 QSO 13 44 27.0638968862 -10 35 41.748550205     17.1     ~ 46 0
6 HS 1700+6416 QSO 17 01 00.6195618802 +64 12 09.118927057   16.39 16.17     ~ 343 0
7 QSO J2233-606 QSO 22 33 37.5814904803 -60 33 29.146578276 16.90 17.39 17.16 16.93 16.51 ~ 86 0
8 QSO B2347-4342 QSO 23 50 34.2595236845 -43 25 59.680334378   16.3 16.3     ~ 159 0

    Equat.    Gal    SGal    Ecl

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2020.08.07-21:02:08

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