Outflowing material in the z<SUB>em</SUB> = 4.92 BAL QSO SDSS J160501.21-011220.0 - Université Pierre et Marie Curie Accéder directement au contenu
Article Dans Une Revue Astronomy and Astrophysics - A&A Année : 2003

Outflowing material in the zem = 4.92 BAL QSO SDSS J160501.21-011220.0

Résumé

We present the analysis of broad absorption lines (BALs) seen in the spectrum of the zem =~ 4.92 QSO SDSS J160501.21-011220.0. Our high spectral resolution UVES spectrum shows two well-detached absorption line systems at zabs = 4.685 and 4.855. The system at zabs = 4.855 covers the background source completely, suggesting that the gas is located outside the broad emission line region. On the contrary, the system at zabs = 4.685, which occults only the continuum source, has a covering factor of the order of 0.9. Physical conditions are investigated in the BAL system at zabs = 4.855 using detailed photoionization models. The observed H I absorption line together with the limits on C II and Si II absorptions suggest that 16 < log N(H I) (cm-2) < 17 in this system. Comparison with models show that the observed column densities of N V , Si IV and C IV in this system require that nitrogen is underabundant by more than a factor of 3 compared to silicon if the ionizing radiation is similar to a typical QSO spectrum. This is contrary to what is usually derived for the emission line gas in QSOs. We show that the relative suppression in the N V column density can be explained for Solar abundance ratios or abundance ratios typical of Starburst abundances if an ionizing spectrum devoid of X-rays is used instead. Thus, if the composition of BAL is like that of the emission line regions it is most likely that the cloud sees a spectrum devoid of X-rays similar to what we observe from this QSO. This is consistent with the fact that none of our models have high Compton optical depths to remove X-rays from the QSO. Similar arguments lead to the conclusion that the system at zabs = 4.685 as well is not Compton thick. Using simple Eddington arguments we show that the mass of the central black hole is ~ 7.1x 108 Msun. This suggests that the accretion onto a seed black hole must have started as early as z ~ 11.

Based on observations carried out at the European Southern Observatory (ESO) under programmes 67.A-0078 and 69.A-0457 with the UVES spectrograph installed at the Nasmyth focus B of the VLT 8.2m telescope, unit Kueyen, on Cerro Paranal in Chile.

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Dates et versions

hal-04111214 , version 1 (09-06-2023)

Identifiants

Citer

N. Gupta, R. Srianand, P. Petitjean, C. Ledoux. Outflowing material in the zem = 4.92 BAL QSO SDSS J160501.21-011220.0. Astronomy and Astrophysics - A&A, 2003, 406, pp.65-73. ⟨10.1051/0004-6361:20030793⟩. ⟨hal-04111214⟩
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