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Alan Stockton |
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"Extended Emission-Line
Regions around QSOs" |
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The spectacular luminous extended emission regions that are present around some low-redshift (z < 0.5) QSOs have been something of an enigma. Although they are virtually exclusively associated with steep-spectrum radio-loud QSOs, their morphologies generally show no correlation with either the radio structure or the host galaxy stellar distribution. The origin of the ionized gas has also been controversial: does it come from the interstellar medium of the host galaxy or from an external source, such as a cooling flow or a merging gas-rich galaxy? Recent detailed studies of a few of these emission regions have begun to give answers to some of these questions. These will be discussed, along with some more speculative comments on how the mechanisms involved may be connected to issues of galaxy formation at high redshifts. |