Comprehensive study of the QSO-galaxy pair 1327-206 and the extent oflow ionization galactic haloes.

Abstract

New observations of the absorption systems in the spectrum of the QSO-galaxy pair 1327-206 are presented. At a resolving power of about 10000, the Na I doublet from the z = 0.0179 absorber is resolved in at least two components separated by 236 km s^-1. The ESO 1327-2041 spiral galaxy (z = 0.0180) is at a projected distance of 20(50/H₀) kpc west from the QSO. CCD imaging reveals a disturbed faint east arm which does not appear to extend to the QSO but rather bends back towards the galaxy. There is another absorption system in the QSO spectrum at z = 0.8526. Its Mg II doublet has also been observed at high resolution. A few faint extended objects close on the sky to the QSO are detected in the deep CCD imaging. They are most probably the brightest members of a galaxy cluster at z = 0.85. To compare the values obtained for the size of gaseous haloes from Ca II (z ≡ 0) and Mg II (z ≡ 0.5) surveys, the authors have analyzed new and previously reported results for Ca II and Mg II doublets detected within the same absorption system. It is shown that the available Ca II and Mg II surveys lead to compatible values for the halo radii at variance with previous claims by Morton et al. (1986).