Absorption Lines in Quasi-stellar Objects with z_abs>Z_em

Abstract

OF the approximately twenty-five quasi-stellar objects which are known to have absorption lines^1,2, six have absorption lines with larger redshifts than the corresponding emission lines. In each case, 0.01≲Z_abs–Z_em<0.03 Four of the objects (PKS 1229–02, PHL 1222, PKS 0119–04, 4C 25.5) have only one emission line and one absorption line system. The two remaining objects (Ton 1530, B 194) each have one emission line system, but several distinct absorption line systems, only one of which has a larger redshift than the emission lines. It has been suggested that absorption lines in QSOs originate in clouds of gas which have been ejected from the QSO as a result of outbursts³. The lines having Z_abs>Z_em are then interpreted as resulting from clouds which have a peculiar inward velocity that exceeds the mean outward motion of the system of clouds. In spite of the extremely large velocity dispersion required among the clouds to bring about this situation, it is conceivable that it might occasionally occur. But the relatively common occurrence of lines for which z_abs>Z_em suggests that the assumption that the usual state of a QSO is one in which matter is flowing outward may not be entirely valid.