ON PROBING THE PROPERTIES OF QSOs THROUGH THEIR PROXIMITY EFFECTS ON THE INTERGALACTIC MEDIUM

The proximity effect (PE) of QSOs is believed to be useful in constraining the QSO lifetime. Observations of the PE so far, however, give apparently contradictory results-some are consistent with a long QSO lifetime (greater than or similar to a few 10(7) yr), but others appear to be only consistent with a short QSO lifetime (less than or similar to 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 Ly alpha forest spectra. We demonstrate that the QSO properties and environment can be constrained simultaneously by the transverse PE (TPE) 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., less than or similar to 10(6) yr) is not required; and (3) the half opening angle of the tori associated with QSOs is similar to 60 degrees, 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.