The Frequency and Radio Properties of Broad Absorption Line Quasars

A sample of 67 Broad Absorption Line quasars (BALQSOs) from the Large Bright Quasar Survey (LBQS) is used to estimate the observed and intrinsic fraction of BAL quasars in optically--selected samples at intermediate (B_J \simeq 18.5) magnitudes. The observed BALQSO fraction in the redshift range 1.5 < z < 3.0 is 15\pm3%. A well--determined, empirical, k--correction, to allow for the differences in the spectral energy distributions of non--BALQSOs and BALQSOs shortward of \simeq 2100A in the restframe, is applied to the sample. The result is an estimate of the intrinsic fraction of BALQSOs, in the redshift range 1.5 < z < 3.0, of 22+/-4%. This value is twice that commonly cited for the occurrence of BALQSOs in optically--selected samples and the figure is in reasonable agreement with that from a preliminary analysis of the SDSS Early Data Release. The fraction of BALQSOs predicted to be present in an optical survey with flux limits equivalent to that of the FIRST Bright Quasar Survey (FBQS) is shown to be \simeq 20%. The BALQSO fractions derived from the FBQS and the LBQS suggest that optically--bright BALQSOs are half as likely as non-BALQSOs to be detectable as S_1.4GHz > 1mJy radio sources.Comment: Accepted for publication in AJ, April 2003 Issu

An Extraordinary Scattered Broad Emission Line in a Type 2 QSO

An infrared-selected, narrow-line QSO has been found to exhibit an extraordinarily broad Halpha emission line in polarized light. Both the extreme width (35,000 km/sec full-width at zero intensity) and 3,000 km/sec redshift of the line centroid with respect to the systemic velocity suggest emission in a deep gravitational potential. An extremely red polarized continuum and partial scattering of the narrow lines at a position angle common to the broad-line emission imply extensive obscuration, with few unimpeded lines of sight to the nucleus.Comment: 4 pages, 1 figure, to appear in the Astrophysical Journal Letter

Observations of Lyman-alpha Absorption in a Triple Quasar System

We have obtained follow-up observations of the quasar pair LBQS 0107-025A,B and new observations of the nearby quasar LBQS 0107-0232 with the Hubble Space Telescope Faint Object Spectrograph. Extended wavelength coverage of LBQS 0107-025A and B using the G270H grating was also obtained. This triple system is unique in providing sensitivity to coherent Ly-alpha absorption on transverse scales of approximately 1 Mpc at z < 1. Monte Carlo simulations were used to establish the confidence level for matches between absorption features in different lines of sight as a function of velocity separation. Pairwise, there are 8, 9, and 12 lines that match between spectra. Three instances of matches between all three lines of sight were found with velocity separations of less than 550 kms^-1. Two of the pairings have coincident lines within |Delta v| < 200 kms^-1 that would occur with less than 10% probability by chance. Taking into account the equivalent widths of the lines, one of these triple coincidences is significant at the 99.99% confidence level, based on Monte Carlo simulations with random line placements. Matches with strong lines preferentially have small velocity separations. These same simulations are used to demonstrate that the distribution of matches for a population of absorbers randomly distributed in velocity space is peaked toward |Delta v| = 0, which has implications for the statistical significance of matches. One of the triple coincidences appears to be a strong absorber with a sheet-like, but inhomogeneous, geometry and a coherence length approaching or exceeding 1 Mpc.Comment: 23 pages, 9 figures, accepted for publication in the Astrophysical Journa