<LI> 22 May: <b>Wil van Breugel</b> (Institute of Geophysics and
Planetary Physics, Lawrence Livermore National Laboratory, USA) <br>
<em>``Giant Ly-a Haloes, Massive Galaxies and Proto-Clusters''</em><br>
<b>Abstract.</b>
In popular, hierarchical models the most massive galaxies and
clusters of galaxies are expected to form in over-dense regions.
There is considerable evidence that powerful radio galaxies are
uniquely associated with the most massive galaxies (and black
holes). For example, the combined near-IR `Hubble' K-z relation
for radio and field galaxies shows that high-z radio galaxies
(HzRGs) are among the most massive galaxies at any given epoch
up to z = 5.2 (De Breuck et al 2001, astro-ph/0109540). HzRGs
are therefore ideal beacons for studying the formation and
evolution of massive galaxies and proto-clusters. <BR>
I will present the results of ultra-deep Ly-a imaging and spectroscopy
(optical and IR) of several high redshift (z > 2) radio galaxies and
their surrounding fields using the Keck and VLT telescopes. The
observations show giant (150 kpc) Ly-a halos centered on the radio
galaxies, as well as spectroscopically confirmed over-densities of
Ly-a excess galaxies at redshifts ranging from 2 to 4. I will
discuss the possible origin and ionization of the halos and their
filamentary structures, and the implications of the existence of
proto-clusters already at redshifts up to z ~ 4.<BR>
See e.g. the
<A HREF="http://www.eso.org/outreach/press-rel/pr-2002/pr-07-02.html">
ESO Press Release (April 9)</A>.
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