ar X iv : a st ro - p h / 97 09 21 0 v 1 2 2 Se p 19 97 ’ Galaxy Associations ’ as Possible Common Features of Galaxy Clusters

ar X iv : a st ro - p h / 97 09 16 3 v 1 1 7 Se p 19 97 Modelling Galaxy Formation at high z

I describe a semi-analytical model for the formation and evolution of galaxies in hierarchical clustering models, and its predictions for the properties of the galaxy population at high z. The predictions are found to agree well with the observed properties of the Lyman break galaxies found at z ∼ 3 by Steidel et al. . The models predict that the star formation rate per comoving volume should h...

ar X iv : a st ro - p h / 97 09 22 7 v 1 2 4 Se p 19 97 Limits on the Variability of Physical Constants

We have compared the frequency of high-redshift Hydrogen HI 21 cm absorption with that of associated molecular absorption in two quasars to place new (1 sigma) upper limits on any variation in y ≡ gpα 2 (where α is the fine structure constant and gp is the proton g-factor) of ∆y/y < 5 × 10 −6 at redshifts z = 0.25 and z = 0.68.

ar X iv : a st ro - p h / 97 11 13 5 v 1 1 2 N ov 1 99 7 HOT ELECTRONS AND COLD PHOTONS : GALAXY CLUSTERS AND THE SUNYAEV - ZEL ’ DOVICH EFFECT

ar X iv : a st ro - p h / 97 09 14 1 v 1 1 5 Se p 19 97 The complex molecular absorption line system at z = 0 . 886 towards PKS 1830 – 211

New single dish and millimeter wave interferometer observations of the molecular absorption line system in the gravitational lens to PKS1830–211 at z=0.88582 is presented. Self–calibrated interferometer data shows unequivocally that the previously detected absorption component is associated with the gravitationally lensed south–west image of the background source. A second absorption line of HC...

ar X iv : a st ro - p h / 97 09 13 7 v 1 1 5 Se p 19 97 Distribution of the Lyman - α Forest at z = 0 . 0 − 1 . 7

We present the analysis of a sample of the Ly-α forest spectra of 152 quasars taken with the HST FOS. The Ly-α lines show little evolution at 0 < z < 1.7. We see a difference between the evolution indices for weak and strong lines.