Properties of QSO Metal Line Absorption Systems at High Redshifts: Nature and Evolution of the Absorbers and New Evidence on Escape of Ionizing Radiation from Galaxies

Using Voigt-profile-fitting procedures on Keck HIRES spectra of nine QSOs we identify 1099 CIV absorber components clumped in 201 systems outside the Lyman forest over 1.6 < z < 4.4. With associated SiIV, CII, SiII and NV where available we investigate bulk statistical and ionization properties of the components and systems and find no significant change in redshift for CIV and SiIV while CII, SiII and NV change substantially. The CIV components exhibit strong clustering but no clustering is detected for systems on scales from 150 km/s out to 50000 km/s. We conclude the clustering is due entirely to the peculiar velocities of gas present in the circumgalactic media of galaxies. Using specific combinations of ionic ratios we compare our observations with model ionization predictions for absorbers exposed to the metagalactic ionizing radiation background augmented by proximity radiation from their associated galaxies and find the generally accepted means of radiative escape by transparent channels from the internal star-forming sites is spectrally not viable for our stronger absorbers. We develop an active scenario based on runaway stars with resulting changes in the efflux of radiation that naturally enable the needed spectral convergence and in turn provide empirical indicators of morphological evolution in the associated galaxies. Together with a coexisting population of relatively compact galaxies indicated by the weaker absorbers in our sample the collective escape of radiation is sufficient to maintain the IGM ionized over the full range 1.9 < z < 4.4.Comment: 131 pages including 46 pages of figures and 33 pages of tables. Accepted for publication by the Astrophysical Journal (Supplement). arXiv admin note: text overlap with arXiv:astro-ph/030755

Interview with Wallace L. W. Sargent

An interview in two sessions in July 1991 with Dr. Wallace L. W. Sargent, Ira S. Bowen Professor of Astronomy in the Division of Physics, Mathematics, and Astronomy (PMA). Dr. Sargent received his BS (1956), MS (1957) and PhD in physics (1959) from the University of Manchester, U.K. He became a research fellow at Caltech, working on quasar absorption lines, from 1959 to 1962. In 1966, he joined the Caltech faculty as an assistant professor of astronomy, becoming associate professor two years later, full professor in 1971, and Bowen Professor in 1981. He served as executive officer for astronomy 1975-1981 and 1996-1997 and director of Palomar 1997-2000. In this interview, he discusses his involvement with the origins, in the early 1980s, of the first of the Keck Foundation telescopes on Mauna Kea, known as Keck I. He recalls the initial plans for a big telescope in partnership either with the Carnegie Institution, the University of Arizona, or the University of California, and the circumstances leading to eventually joining with UC on Keck I; the problematic relationship with Carnegie; and his involvement, along with Rochus Vogt, Gerry Neugebauer, and Edward Stone, in raising money from the Keck Foundation. He discusses the design competition for the proposed 10-meter telescope; the contributions of Jerry Nelson, then at Lawrence Berkeley Laboratory; and the difficulties encountered in designing and building the telescope. He concludes with an account of the decision to build Keck II

The Lyman-alpha Forest at z~4: Keck HIRES Observations of Q 0000-26

This paper describes a study of the Lyman-alpha forest absorption clouds along the quasar sightline Q0000-26 (zem=4.1). The spectrum was obtained with the High Resolution Spectrometer on the 10m Keck telescope. We derive accurate H I column density and Doppler width distributions for the clouds from Voigt profile fitting. We also analyze simulated Lyman-alpha forest spectra of matching characteristics in order to gauge the effects of line blending/blanketing and noise in the data. The results are compared with similar studies at lower redshifts in order to study any possible evolution in the clouds' properties. We also estimate the mean intensity of the UV background at z=4 from an analysis of the proximity effect.Comment: plain TeX containing 23 PS pages, 3 PS tables, and 9 PS figures, ApJ, Dec 1, 1996 issue replacing an earlier version which contains an corrupted table