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Astron. Astrophys. 330, 19-24 (1998)

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5. Summary and conclusions

  1. In this paper we have presented spectra of the quasar Q0151+048A, and found evidence for emission in the trough of the [FORMULA] DLA absorption line at [FORMULA].
  2. We have previously reported the detection of Ly [FORMULA] emission from the [FORMULA] [FORMULA] DLA system towards the quasar PKS0528-250, while an emission line in the trough of a third [FORMULA] DLA absorber, at [FORMULA], has also recently been reported. There is only one published successful detection of Ly [FORMULA] emission from an intervening DLA absorber, so these results suggest that Ly [FORMULA] emission is more common in or near [FORMULA] DLA absorbers than in or near intervening DLA absorbers.
  3. Despite this we find no evidence that [FORMULA] DLA absorbers are not members of the same population as intervening DLA absorbers. In particular we are unable to make a connection between the [FORMULA] DLA absorbers and the so-called intrinsic absorbers, which are of higher metallicity and higher ionisation. Neither is it possible to associate the [FORMULA] DLA absorbers with the disk of the quasar host galaxy, as the redshifts of the absorbers are not compatible with the measured quasar systemic redshifts.
  4. Star formation is almost certainly the cause of the Ly [FORMULA] emission from one of the three absorbers discussed here. Photoionisation by the quasar could be the explanation for the other two emission lines, but this can only be established by more detailed studies, and other explanations are possible.
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© European Southern Observatory (ESO) 1998

Online publication: January 8, 1998