The near-ultraviolet spectrum of the high-redshift BL Lacertae object0215+015.

Abstract

Spectra of the luminous high-redshift BL Lac object 0215+015 have been obtained with the IUE from 2300 to 3150 Å and with the AAT from 3040 to 3870 Å. A total of 66 absorption lines were detected, 50 of which can be identified in the six definite and one probable redshift systems ranging from z_abs = 1.254 to z_abs = 1.719. Strong unidentified lines found shortward of 3310 Å are assumed to be members of a sparse Lyα forest. This is the first reported detection of a Lyα forest in a BL Lac object. The intrinsic redshift of 0215+015 is likely to be near 1.7. From a detailed column density comparison it is shown that the z_abs = 1.345 system is most probably an intervening galaxy, with the sight line intercepting both disk- and halo-type material.