Extended emission-line regions around QSOs

A narrow-band forbidden O III 5007 A imaging survey of a sample of 47 luminous low-redshift QSOs is reported. The ionized gas is found to be not well correlated with the extended continuum material, as would be expected if it were normal interstellar gas. The distribution of the ionized gas in most of the objects is highly structured over scales of tens of kpc, but this structure is generally quite asymmetric and is clearly not that of gas in an equilibrium configuration. The results are consistent with the assumption that the extended gas has been ionized by the UV continuum from the QSO nucleus. The correlations between the presence of strong extended emission and both the strength of the nuclear narrow-line emission and the radio spectral index generally confirm the results of Boroson and Oke (1984) and Boroson et al. (1985).