Open AccessSize estimates for intervening C iv absorbers from high‐resolution spectroscopy of APM 0827+5255
Author(s) -
Tzanavaris Panayiotis,
Carswell Robert F.
Publication year - 2003
Publication title -
monthly notices of the royal astronomical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.058
H-Index - 383
eISSN - 1365-2966
pISSN - 0035-8711
DOI - 10.1046/j.1365-8711.2003.06355.x
Subject(s) - qsos , physics , astrophysics , redshift , line of sight , line (geometry) , spectral line , equivalent width , absorption (acoustics) , lyman limit , absorption spectroscopy , emission spectrum , optics , astronomy , galaxy , intergalactic medium , geometry , mathematics
A new analysis of Keck/HIRES observations of the broad absorption line quasi‐stellar object (QSO) APM 0827+5255 indicates that a number of intervening C iv absorbers give rise to absorption lines for which the observed optical depths for the 1548, 1550 Å doublet components are not in the expected 2:1 ratio. To compensate for the effect, a local adjustment of the zero‐level is required. We model this effect as coverage of one line of sight to this gravitationally lensed QSO and perform a set of simulations to select a sample of lines for which our model provides an explanation for the effect. We use lines in this sample to obtain estimates for minimum C iv absorber sizes from total coverage and the separations of the lines of sight for a range of lens redshifts, z l , and two cosmologies. We also obtain best estimates for overall sizes from a statistical ‘hit and miss’ approach. For z l = 0.7 our results set a lower limit to sizes of C iv absorbers of ∼0.3 h − 1 72kpc (∼0.5 h − 1 72kpc) for Ω M = 1, Ω Λ = 0 (Ω M = 0.3, Ω Λ = 0.7 ), in agreement with other results from similar work but are limited by sample size and the uncertainty in z l . Our method can be used to detect lensed QSOs and to probe absorber sizes when separate spectra cannot be obtained for each line of sight.