The Non-Damped Nature of Twelve Low-Redshift Damped Lyman Alpha Candidate Systems

Abstract

Hubble Space Telescope (HST) UV spectroscopy of 12 candidate low-redshift damped Lyman alpha (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 $N(HI)\ge 2\times 10^{20}$ atoms cm${}^{-2}$. 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 $N(HI)=3\times 10^{19}$ atoms cm${}^{-2}$ and a z=1.223 system in Q1247+267 which has $N(HI)=8\times 10^{19}$ atoms cm${}^{-2}$. 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.

Accepted for publication in the Astrophysical Journal Letters

References in corpus (3)

• Implications of 21cm observations for damped Ly-$\alpha$ systems
• Chandra Detection of X-ray Absorption Associated with a Damped Lyman Alpha System
• Deep imaging of Q2112+059: A bright host galaxy but no DLA absorber

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• The WSRT wide-field HI survey: II. Local Group features
• A deep search for 21cm absorption in high redshift damped Lyman-$\alpha$ systems
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• The neutral gas extent of galaxies as derived from weak intervening CaII absorbers
• CIV and CIII] reverberation mapping of the luminous quasar PG 1247+267
• A successful search for intervening 21 cm HI absorption in galaxies at 0.4 < z <1.0 with the Australian Square Kilometre Array Pathfinder (ASKAP)
• Adaptive Optics Imaging of Low-redshift Damped Lyman-alpha Quasar Absorbers
• The kinematic signature of damped Lyman alpha systems: Using the D-index to screen for high column density HI absorbers
• Dust depletion of Ca and Ti in QSO absorption line systems
• Multiple origins for the DLA at $z_{\mathrm{abs}}=0.313$ toward PKS 1127$-$145 indicated by a complex dust depletion pattern of Ca, Ti, and Mn