Key Project Papers

The Hubble Space Telescope (HST) Quasar Absorption Line Key Project. XIII. A Census of Absorption Line Systems at Low Redshift

Authors: Buell T. Jannuzi, John N. Bahcall, Jacqueline Bergeron, Alec Boksenberg, George F. Hartig, Sofia Kirhakos, W. L. W. Sargent, Blair D. Savage, Donald P. Schneider, Daviid A. Turnshek, Ray J. Weymann, and Arthur M. Wolfe

Journal: The Astrophysical Journal Supplement Series, 118, 1-125 (September 1998); astro-ph/9805148.

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Abstract: We present a catalogue of absorption lines obtained from the analysis of the ultra-violet spectra of 66 quasars. The data were acquired with the Faint Object Spectrograph of the Hubble Space Telescope (HST) as part of the Quasar Absorption Line Survey, a Key Project for the first four cycles of HST observations. This is the third of a series of catalogues of absorption lines produced from the survey and increases the number of quasars whose higher resolution (R = 1300) spectra we have published from 17 to 83. The general properties and execution of the survey are reviewed, including descriptions of the final sample of observed objects and the algorithmic processes used to construct the catalogue. This database is suitable for a wide variety of studies of gaseous systems in the nearby Universe. This third catalogue includes 2594 absorption lines and brings the total number of absorption lines in the combined catalogue to 3238. The third catalogue has 878 identified Ly- lines, 27 extensive metal line systems (detected absorption lines from four or more metal ions), 88 C IV systems, and 34 O VI systems. The combined catalogue contains the following numbers of extragalactic absorption lines: 1,129 Ly- lines, 107 C IV systems, 41 O VI systems, 16 Lyman-limit systems, and one damped Ly- system (in the spectrum of PG 0935 + 416). In addition, there are 25 pairs of identified Ly- lines that are candidate C IV doublets. Of the 122 identified C IV and candidate C IV systems in the completely identified sample of absorption lines, 24±5 are expected to be chance coincidences of other lines (based upon Monte Carlo simulations). The detection of a single damped Ly- system in a path length of z = 49 yields an observed number of damped systems per unit redshift of (dN/dz)_damp(z = 0.58) = 0.020 with 95% confidence boundaries of 0.001 to 0.096 systems per unit redshift. We include notes on our analysis of each of the observed quasars and the absorption systems detected in each spectrum. Some especially interesting systems include low redshift Ly- absorbers suitable for extensive follow-up observations (e.g. in the spectra of TON 28 and PG 1216 + 069), possibly physically associated pairs of extensive metal line absorption systems (e.g. in the spectrum of PG 0117 + 213), and systems known to be associated with galaxies (e.g. in the spectrum of 3C 232). The spectra of five broad absorption line (BAL) quasars (UM 425, PG 1254 + 047, PG 1411 + 442, PG 1700 + 518, and PG 2112 + 059) can be found in this third catalogue, bringing the total number of BAL quasars in the combined catalogue to six (including PG 0043 + 039).

The Hubble Space Telescope (HST) quasar absorption line key project. VII. absorption systems at z_abs 1.3

Authors: John N. Bahcall, Jacqueline Bergeron, Alec Boksenberg, George F. Hartig, Buell T. Jannuzi, Sofia Kirhakos, W. L. W. Sargent, Blair D. Savage, Donald P. Schneider, Daviid A. Turnshek, Ray J. Weymann, and Arthur M. Wolfe

Journal: The Astrophysical Journal, 457, 19-49 (January 20, 1996); astro-ph/9506124.

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Abstract: We present evidence that clumps of Ly lines are physically associated with about half of the extensive metal-line systems (absorption systems with four or more observed metal-line species) found in this paper, demonstrate that all four Lyman-limit systems discussed here correspond to extensive metal-line absorption systems, and present an extraordinary pair of extensive metal-line absorption systems within 2000 kms of each other at z = 0.95 that are probably an early manifestation of large scale structure. We also determine the evolution of Ly absorption lines at redshifts less than 1.3 by combining the results for 13 smaller redshift quasars discussed in Paper I of this series with the the results for 4 moderate redshift quasars analyzed in the present paper.

The Hubble Space Telescope quasar absorption line key project. I. first observational results, including lyman-alpha and lyman-limit systems

Authors: John N. Bahcall, Jacqueline Bergeron, Alec Boksenberg, George F. Hartig, Buell T. Jannuzi, Sofia Kirhakos, W. L. W. Sargent, Blair D. Savage, Donald P. Schneider, David A. Turnshek, Ray J. Weymann, and Arthur M. Wolfe

Journal: The Astrophysical Journal Supplement Series, 87, 1-43 (July 1993).

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Abstract: Spectra are presented for 37 quasars with small and moderate redshifts; the quasars were observed with the Faint Object Spectrograph of the HST. New higher resolution measurements of the absorption lines in the UV spectra of 11 quasars with emission-line redshifts that lie between 0.3 and 1.0 are reported. Calibrated spectra and continuum fits are shown for each object. A total of 104 extragalactic Ly-alpha systems are identified, nine of which are found at the same redshifts as metal-line systems. The local number density of Ly-alpha systems with rest equivalent widths larger than 0.32 A and without detected metal lines is about 15.1 +/- 4.3 Ly-alpha systems per unit redshift with gamma = 0.30 +/- 0.62 and W* = 0.22 +/- 0.02 A. A total of 10 Lyman-limit systems with an optical depth greater than 0.4 are identified. The paucity of damped Ly-alpha lines at small and moderate redshifts shows that the number density of damped absorption systems decreases with decreasing redshift.