"LARGE SCALE STRUCTURE AT z=1.2 OUTLINED BY MgII ABSORBERS"
The largest known structure in the high redshift universe
is mapped by at
least 18 quasars and spans ~5 deg x 2.5 deg on the sky,
with a quasar spatial
overdensity of 6-10 times above the mean. This
large quasar group (LQG)
provides an extraordinary laboratory ~100 x 200 x 200
h^-3 comoving Mpc^3 in
size (q0=0.5, Lambda=0, H0=100h km/s/Mpc) covering 1.20<
z <1.39 in
redshift. One approach to establishing how
LQGs relate to mass (galaxy)
enhancements is to probe their gas content and distribution
via background
quasars. We have found the LQG to be associated with
11 MgII absorption
systems, an overdensity of ~3, which appear to form a
structure. The minimal
spanning tree test also supports the existence of a structure
of MgII
absorbers coincident with the LQG, and additionally indicates
a foreground
structure populated by MgII absorbers and quasars at
z~0.8. Finally, we find a
tendency for MgII absorbers in general to correlate with
field quasars (i.e.
quasars both inside and outside of the LQG) at a projected
scale length on the
sky of 9/h Mpc and a velocity difference |Delta v|=3000
to 4500 km/s. While
the correlation is on a scale consistent with observed
galaxy-AGN
distributions, the nonzero velocity offset could be due
to the "periphery
effect", in which quasars tend to populate the outskirts
of clusters of
galaxies and metal absorption systems, or to peculiar
velocity effects.