The Intrinsic Far-UV Spectrum of B1422+231

TL;DR

This study uses gravitational lensing and microlensing effects on a high-redshift quasar to extract its intrinsic UV spectrum, revealing details about its proximity zone and Ly-alpha absorption features.

Contribution

It introduces a method to decompose quasar spectra using differential microlensing, enabling the study of intrinsic emission and absorption features at high redshift.

Findings

Detection of the proximity zone edge at 8.6-17.3 Mpc from the quasar

Identification of a blue excess in the Ly-alpha line profile

Implications for quasar activity duration and Ly-alpha fitting techniques

Abstract

We present new spectroscopy of the z=3.62 gravitationally lensed quasar B1422+117 from the Gemini North GMOS integral field spectrograph. We observe significant differential magnifications between the broad emission lines and the continuum, as well as across the velocity structure of the Lyman-alpha line. We take advantage of this differential microlensing to algebraically decompose the quasar spectrum into the absorbed broad emission line and absorbed continuum components. We use the latter to derive the intrinsic Ly-alpha forest absorption spectrum. The proximity effect is clearly detected, with a proximity zone edge of 8.6-17.3 Mpc from the quasar, implying (perhaps intermittent) activity over at least 28 Myrs. The Ly-alpha line profile exhibits a blue excess that is inconsistent with a symmetric fit to the unabsorbed red side. This has important implications for the use of this fitting technique in estimating the absorbed blue Ly-alpha wings of Gunn-Peterson trough quasars.