On probing the properties of QSOs through their proximity effects on the intergalactic medium

TL;DR

This paper investigates the proximity effects of QSOs on the intergalactic medium, resolving previous contradictions in QSO lifetime estimates by considering environmental factors and torus obscuration through simulations.

Contribution

It introduces a comprehensive simulation approach that accounts for density enhancement and torus obscuration, providing refined constraints on QSO lifetime and geometry.

Findings

QSO environments show significant density enhancement.

QSO lifetime is consistent with up to a few 10^7 years.

Half opening angle of QSO tori is about 60 degrees.

Abstract

The proximity effect (PE) of QSOs is believed to be useful in constraining the QSO lifetime. Observations on the PE so far, however, give apparently contradictory results -- some are consistent with a long QSO lifetime (>~ a few 10^7 yr), but others appear to be only consistent with a short QSO lifetime <~ 10^6 yr. In this paper, we show that this apparent contradiction may be solved by simultaneously taking into account both the effect due to the density enhancement in the QSO near zones and that due to the obscuration of the tori associated with the QSOs, using a large number of Monte-Carlo generated synthetic Lyman alpha forest spectra. We demonstrate that the QSO properties and environment can be constrained simultaneously by the transverse PE and the line of sight PE of bright type 1 QSOs together. The current available measurements on the PEs of type 1 QSOs suggest that (1) the density is significantly enhanced in the vicinity of the QSOs; (2) the QSO lifetime is consistent with being as large as a few 10^7 yr and a substantially shorter lifetime (e.g., <~10^6 yr) is not required; and (3) the half opening angle of the tori associated with QSOs is ~60 deg, consistent with some other independent estimates. Our simulations also show that the TPE of type 2 QSOs can be significantly different from that of type 1 QSOs, which may be useful to put further constraints on the QSO properties and the QSO environment.