The Non-Damped Nature of Twelve Low-Redshift Damped Lyα Candidate Systems

Hubble Space Telescope (HST ) UV spectroscopy of 12 candidate low-redshift damped Lyα (DLA) systems in 11 QSOs (z = 0.103 in Q0054+144, z = 0.969 and z = 0.987 in Q0302−223, z = 0.478 in Q0454−220, z = 1.476 in Q1047+550, z = 1.070 in Q1206+459, z = 1.228 in Q1247+267, z = 0.399 in Q1318+290B, z = 0.519 in Q1329+412, z = 0.276 in Q1451−375, z = 0.204 in Q2112+059, z = 0.263 in Q2251+113) are presented; the observations demonstrate that they are not DLAs with NHI ≥ 2 × 10 20 atoms cm. In all cases except two the systems either do not exist or are well below the DLA threshold column density; the exceptions are a z = 0.474 system in Q0454−220 which has NHI = 3 × 10 atoms cm and a z = 1.223 system in Q1247+267 which has NHI = 8 × 10 atoms cm. Despite the availability of data in the HST archives demonstrating that these are not suitable targets, many have unfortunately been approved for observation with Chandra, Gemini, and/or HST with the intent of doing followup work on low-redshift DLAs. Furthermore, these results indicate that the low-redshift DLA statistics derived from IUE spectra and presented by Lanzetta, Wolfe, & Turnshek (1995) and Wolfe et al. (1995) are invalid. Subject headings: quasars: absorption lines — quasars: individual (Q0054+144, Q0215+015, Q0302−223, Q0454−220, Q0935+417, Q1047+550, Q1206+459, Q1247+267, Q1318+290B, Q1329+412, Q1451−375, Q2112+059, Q2223−052, Q2251+113) — galaxy formation Based on data obtained with the NASA/ESA Hubble Space Telescope at the Space Telescope Science Institute, which is operated by AURA, Inc., under NASA contract NAS5-26555. email: [email protected], [email protected]