The Study of the Circumgalactic Medium with Quasar Pairs

Abstract

We have collected 10,025 foreground–background quasar pairs with projected distances d _p 0.15 Å around foreground quasars, including both the line of sight (LOS; of foreground quasars) and transverse (TRA; perpendicular to the LOS) absorptions. Both the equivalent width (the correlation coefficient ρ = −0.915 and the probability P 4 σ ) greater than that of LOS Mg ii absorption lines at projected distances d _p 200 kpc. The anisotropic radiation from quasars would be the most possible interpretation for the anisotropic absorption around quasars. This could also indicate that the quasar radiation is not obviously impacting the gas halos of quasars at scales d _p > 200 kpc.

Keywords

• Quasar absorption line spectroscopy
• Quasar-galaxy pairs