AN EMISSION-LINE PROTOGALAXY CANDIDATE AT Z=2.5

Narrow-band infrared imaging has revealed a faint red galaxy with a st rong (equivalent width = 2%) emission line at 2.30 mu m. The field was observed because of its proximity to the quasar SBS 0953+549, which h as a metal-line absorption system at z(abs) = 2.50. The emission-line galaxy is only separated from the quasar line of sight by a projected distance of 240 kpc, and we identify the emission line as Hal[N II] in a galaxy which is in the same group as the z = 2.50 absorber. Since a ll the galaxy properties are also consistent with a young age and a re dshift of 2.5, it is a prime candidate for a protogalaxy.