H. S. Murdoch

Absorption Line Systems At z > 3 in the QSO 2000-330

This paper presents some preliminary results from analysis of our high- resolution (30–35 km/s FWHM) spectra of the Lyman a forest region in the z = 3.78 QSO 2000-330. These spectra were obtained at the Anglo-Australian Telescope over several observing seasons and have been analysed by fitting multiple-cloud Voigt profiles to Lyman series and heavy-element absorption lines. Two specific issues are addressed here: (i) The distribution of column densities, N(H I), and velocity dispersion, b, for hydrodgen clouds in the interval zabs = 3.43–3.78; (ii) Heavy-element abundances in a system at zabs = 3.1723.

An absorption line study of galaxies at high redshift

Complex velocity structure is revealed in several absorption systems in the spectrum of 0215+015 (z=1.715) at resolutions of 20–30 km s−1 FWHM. Striking differences are found in the relative strengths of low to high ions among the components, reinforcing our interpretation of these systems as intervening galaxies.

QSOs as probes of the early universe

The spectrum of the highest redshift QSO 2000–330 (z = 3.78) contains four heavy-element absorption systems with zabs > 3.0. Interesting features include velocity structure at zabs = 3.552 which suggests a cluster origin and a purely low ionization system at zabs = 3.1881 typical of a galactic disk sightline.

Absorption Structure in the BL Lac Object 0215+015 at 20 km s-1 Resolution

The origin of the narrow metal absorption lines in the spectra of QSOs remains uncertain despite the large amount of high-quality data obtained at high resolution over the past decade. Recently, statistical tests of a uniform sample of C IV absorption systems have shown that their redshift distribution is consistent with the view that these lines arise in randomly distributed intervening galaxies in a Friedmann Universe (Young, Sargent and Boksenberg 1982, hereafter YSB). In a complementary approach we consider in detail the physical properties of the absorbing material in cases of particular interest. We have chosen the high-redshift BL Lac object 0215+015 (Blades et al. 1982, hereafter BHMP) for detailed spectroscopic study because it is currently in a bright phase (V ~ 14.5 – 16.5) and because it has several strong absorption systems with differing ionization structure. From our medium-resolution spectra of 0215+015 (BHMP) it appears that the density of C IV systems per unit redshift in this object is somewhat higher than, but not inconsistent with, the average density in the YSB sample.