In an ongoing programme to identify a sample of high z DLA galaxies we have found the long sought for case of a Ly \alpha emitter seen in the centre of a broad DLA trough .
This is the predicted “ textbook case ” of an intervening DLA galaxy if DLA galaxies are small , but would not be expected if intervening high redshift DLA galaxies have large gaseous disks .
The Ly \alpha flux is 5.4 ^ { +2 } _ { -0.8 } \times 10 ^ { -17 } ergs~ { } s ^ { -1 } cm ^ { -2 } similar to what has been found in previously known high z DLA galaxies .
The impact parameter is found to be 0 \aas@@fstack { \prime \prime } 3 \pm 0 \aas@@fstack { \prime \prime } 3 .
This is smaller than what was found in previous cases but still consistent with random sight-lines through absorbers with mean impact parameter \approx 1 ″ .
Of the 24 DLAs targeted in the NICMOS imaging survey five have now been identified as Ly \alpha emitters .
The DLA galaxies with detected Ly \alpha emission tend to have higher interstellar metallicities than those with undetected Ly \alpha emission .
This is plausibly explained as a consequence of a positive correlation between the Ly \alpha line luminosities of the galaxies and their metallicities , although the present sample is too small for a definitive conclusion .
The available observations of high-redshift DLA galaxies are also consistent with a negative correlation between Ly \alpha equivalent widths and metallicities , as seen in nearby star-forming galaxies and usually attributed to the preferential absorption of Ly \alpha photons by dust grains .