We report results of a high-resolution imaging search for the galaxy associated with the damped Lyman- \alpha ( DLA ) absorber at z = 1.892 toward the z _ { em } = 2.543 quasar LBQS 1210+1731 , using HST/NICMOS .
The images were obtained in the broad filter F160W and the narrow filter F190N with camera 2 on NICMOS , and were aimed at detecting the absorber in the rest-frame optical continuum and in H- \alpha line emission from the DLA absorber .
After suitable point spread function ( PSF ) subtractions , a feature is seen in both the broad-band and narrow-band images , at a projected separation of 0.25 \arcsec from the quasar .
This feature may be associated with the DLA absorber , although we can not completely rule out that it could be a PSF artifact .
If associated with the DLA , the object would be \approx 2 - 3 h _ { 70 } ^ { -1 } kpc in size with a flux of 9.8 \pm 2.4 \mu Jy in the F160W filter , implying a luminosity at \lambda _ { central } = 5500 Å in the rest frame of 1.5 \times 10 ^ { 10 } h _ { 70 } ^ { -2 } L _ { \odot } at z = 1.89 , for q _ { 0 } = 0.5 .
However , a comparison of the fluxes in the broad and narrow filters indicates that most of the flux in the narrow-band filter is continuum emission , rather than red-shifted H- \alpha line emission .
This suggests that if this object is the absorber , then either it has a low star formation rate ( SFR ) , with a 3 \sigma upper limit of 4.0 h _ { 70 } ^ { -2 } M _ { \odot } yr ^ { -1 } , or dust obscuration is important .
It is possible that the H- \alpha emission may be extinguished by dust , but this seems unlikely , given the typically low dust-to-gas ratios observed in DLAs .
Alternatively , the object , if real , may be associated with the host galaxy of the quasar rather than with the damped Ly- \alpha absorber .
H-band images obtained with the NICMOS camera 2 coronagraph show a much fainter structure \approx 4 - 5 h _ { 70 } ^ { -1 } kpc in size and containing four knots of continuum emission , located 0.7 \arcsec away from the quasar .
This structure is not seen in images of comparison stars after similar PSF subtractions , and is also likely to be associated with the absorbing galaxy or its companions , although we do not know its redshift .
We have probed regions far closer to the quasar sight-line than in most previous studies of high-redshift intervening DLAs .
The two objects we report mark the closest detected high-redshift DLA candidates yet to any quasar sight line .
If the features in our images are associated with the DLA , they suggest faint , compact , somewhat clumpy objects rather than large , well-formed proto-galactic disks or spheroids .
If the features are PSF artifacts , then the constraints on sizes and star-formation rates of the DLA are even more severe .
The size , luminosity , and SFR estimates mentioned above should therefore be conservatively considered as upper limits .