An investigation of the line of sight towards QSO PKS 0237−233★

Abstract

We present a detailed analysis of absorption systems along the line of sight towards QSO PKS 0237−233 using a high resolution spectrum of signal-to-noise ratio (SNR) ∼60-80 obtained with the Ultraviolet and Visual Echelle Spectrograph mounted on the Very Large Telescope. This line of sight is known to show a remarkable overdensity of C iv systems that has been interpreted as revealing the presence of a supercluster of galaxies. A detailed analysis of each of these absorption systems is presented. In particular, for the z abs = 1.6359 (with two components of log N HI [ cm −2 ] =18.45, 19.05) and z abs = 1.6720 (log N HI = 19.78) sub-Damped Lyα systems (sub-DLAs), we measure accurate abundances (resp. [O/H] = −1.63±0.07 and [Zn/H] = −0.57±0.05 relative to solar). While the depletion of refractory elements onto dust grains in both sub-DLAs is not noteworthy, photoionization models show that ionization effects are important in a part of the absorbing gas of the sub-DLA at z abs = 1.6359 (H i is 95 percent ionized) and in part of the gas of the sub-DLA at z abs = 1.6359 The C iv clustering properties along the line of sight is studied in order to investigate the nature of the observed overdensity. We conclude that despite the unusually high number of C iv systems detected along the line of sight, there is no compelling evidence for the presence of a single unusual overdensity and that the situation is consistent with chance coincidence.

Properties of Qso Metal-Line Absorption Systems at High Redshifts: Nature and Evolution of the Absorbers and New Evidence on Escape of Ionizing Radiation From Galaxies

“…Furthermore, the majority of the members in our system sample have a velocity width of <100 km s −1 , and therefore might fortuitously act in the v link regime; however, we find no contributing signal to system clustering. In measurements similar to ours, Fathivavsari et al (2013) also find no evidence of system clustering (see Section 7.4).…”

VLT/UVES observations of peculiarαabundances in a sub-DLA atz≈ 1.8 towards the quasar B1101−26

“…However, similar inconsistencies in the relative abundance of α-elements have been found in other high-redshift absorbers, too (e.g. Bonifacio et al 2001;Prochaska & Wolfe 2002;Fathivavsari et al 2013). We note that the large range in the above listed ratios originates in the very weak sulphur absorption, which is below the detection limit in most of the absorption components.…”

“…Abundance ratios that cannot be explained by current nucleosynthetic theories have also been found by other groups, e.g. by Fathivavsari et al (2013), who find sulphur being overabundant compared to oxygen in a sub-DLA, by Bonifacio et al (2001), who find sulphur being overabundant compared to oxygen, silicon, and iron even though [S/H] = −1.04 in the considered DLA, and by Lehner et al (2008).…”

“…As has been pointed out in Sect. 4.7, peculiar sulphur abundances have also been found by Bonifacio et al (2001), and Fathivavsari et al (2013) have derived abundances of α-elements not being in line with each other in sub-DLA systems. Other detailed studies of multi-component absorbers at high redshift provide further evidence of significant discrepancies between a standard SN Type II enrichment pattern and measured gas-phase abundances in individual absorption components.…”

Ghostly Strong Lyα Absorbers: Tracers of Gas Flows in the Close Vicinity of Quasars?

“…We determined the rest EWs of the absorption lines in the stacked spectrum of the ghostly DLAs using Gaussian fits (Fathivavsari et al 2013). The results are summarized in Table 2.…”