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          Institute: MPI für Astronomie     Collection: Publikationen_mpia     Display Documents



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ID: 421368.0, MPI für Astronomie / Publikationen_mpia
The quasar proximity effect at redshift <z> ~= 2.6 with the From Lines to Overdensities approach
Authors:D'Odorico, V.; Bruscoli, M.; Saitta, F.; Fontanot, F.; Viel, M.; Cristiani, S.; Monaco, P.
Date of Publication (YYYY-MM-DD):2008
Title of Journal:Monthly Notices of the Royal Astronomical Society
Journal Abbrev.:MNRAS
Volume:389
Start Page:1727
End Page:1738
Review Status:Peer-review
Audience:Experts Only
Abstract / Description:We revisit the proximity effect produced by quasars (QSOs) at redshifts 2.1-3.3 applying the From Lines to Overdensities (FLO) approach to a sample of ~6300 Lyalpha lines fitted in 21 high resolution, high signal-to-noise spectra. This new technique allows to recover the hydrogen-density field from the HI column densities of the lines in the Lyalpha forest, on the basis of simple assumptions on the physical state of the gas. To minimize the systematic uncertainties that could affect the density recovering in the QSO vicinity, we carefully determined the redshifts of the QSOs in our sample and modelled in detail their spectra to compute the corresponding ionizing fluxes. The mean density field obtained from the observed spectra shows a significant overdensity in the region within 4 proper Mpc from the QSO position, confirming that QSOs are hosted in high-density peaks. The absolute value of rho/<rho> for the peak is uncertain by a factor of ~3, depending on the assumed QSO spectral slope and the minimum HI column density detectable in the spectra. We do not confirm the presence of a significant overdensity extending to separations of ~15 proper Mpc from the QSO, claimed in previous works at redshifts <z> ~= 2.5 and 3.8. Our best guess for the ultraviolet background (UVB) ionization rate based on the intergalactic medium (IGM) mean density recovered by FLO is GammaUVB ~= 10-12s-1. However, values of GammaUVB ~= 3 × 10-12s-1 could be viable if an inverted temperature-density relation with index alpha ~= -0.5 is adopted. Based on observations collected at the European Southern Observatory (ESO) Very Large Telescope (VLT), Cerro Paranal, Chile - Programs 166.A-0106(A) and during commissioning and science verification of UVES. E-mail: dodorico@oats.inaf.it
Free Keywords:intergalactic medium; quasars: absorption lines; cosmology: observations; large-scale structure of Universe
External Publication Status:published
Document Type:Article
Communicated by:N. N.
Affiliations:MPI für Astronomie
Identifiers:URL:http://adsabs.harvard.edu/abs/2008MNRAS.389.1727D [ID No:1]
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