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Session 87 - Environments of QSOs and Radio Galaxies.
Oral session, Wednesday, January 17
Corte Real, Hilton
A sample of 16 quasars from the Large Bright Quasar Survey (LBQS) has been imaged with WFPC2 on the Hubble Space Telescope. Host galaxies are clearly visible around several of the quasars. Many fields contain companions with small projected separations from the host galaxies, and there is evidence of interaction between the companion and the host galaxy in some cases. The sample was selected to include radio-loud and radio-quiet quasars in a narrow range of redshift (0.4 \leq z \geq 0.5) at faint to moderate absolute magnitudes (-23 < M_B < -25).
Radio observations of the LBQS indicate that the radio-loud fraction of optically selected quasars is mostly independent of absolute magnitude and redshift (Hooper et al. 1995, ApJ, 445, 62; Hooper et al. 1995, ApJ, submitted). No correlation is detectable between radio luminosity and absolute magnitude among radio-loud quasars, and the radio-loud fraction remains constant at \approx 10% from M_B = -23 to M_B \geq -28. In particular, no decrease in radio-loud fraction for M_B fainter than -24 is seen, contrary to several previous studies based on the Palomar-Green quasar survey (e.g., Peacock et al. 1986, MNRAS, 218, 265). The radio-loud fraction does not evolve, aside from a modest peak at z \sim 1, from z = 0.2 to redshifts approaching 5, based on the LBQS and three high-redshift quasar samples.
