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Session 11 - QSOs and Radio Galaxies.
Display session, Monday, June 08
We have observed a sample of 25 high luminosity QSOs, in the range 2.0 \lesssim z \lesssim 2.5, at 1.6\micron with the near-infrared spectrograph FSPEC on the Multiple Mirror Telescope. We have measured the systemic redshift z_ sys by direct detection of the strong [\ionO3]\lambda5007 line emitted from the narrow-line-region. We have found that the broad H\beta lines, from the same spectra, have a systematic mean red shift of 530\pm80 km s^-1 with respect to systemic. From data in the literature, we have found that the high ionization, rest-frame ultraviolet broad lines \ionC4\lambda1549 and Ly\alpha are systematically blue shifted \sim 1500 km s^-1 and \sim 1000 km s^-1, respectively, from systemic. Therefore, estimating the ionizing flux from the inter-galactic-medium J_\nu^IGM via the Proximity Effect, using redshift measurements from these two broad line species, results in an over-estimation of J_\nu^IGM by factors of 2.5-4.0. Furthermore, related calculations of the lower limit for the density of baryons Ømega_b will be over-estimated by factors of 1.6-2.0. However, the low ionization broad line \ionMg2\lambda2798 is within 100 km s^-1 of systemic, and thus would be the line of choice for determining the true redshift of distant (z>1) QSOs without near-infrared spectroscopy.
Program listing for Monday