The large-scale structure of the early universe

Supervisor: Dr Roger Clowes

In 2013 Clowes et al. discovered the Huge-LQG as the “largest structure in
the early universe”. This discovery followed the earlier discovery of the
Clowes-Campusano (1991) LQG, or CCLQG, which was itself then the largest
structure known in the early universe. A LQG — Large Quasar Group — is a
large structure (or overdense volume) that is highlighted in the distribution
of quasars. Remarkably, both the Huge-LQG and the CCLQG are at the same
redshift (or distance) and are adjacent on the sky, although there is no
known connection between them.

Until recently the only viable probe of the large-scale structure of the
early universe has been quasars. The high-luminosities of quasars allow their
relatively easy detection at redshifts >~ 0.8 across large areas of sky. At
such redshifts, galaxies and clusters of galaxies present rather greater
observational challenges. However, technological advances have resulted in a
new type of cosmological probe becoming available — intervening MgII

Intervening MgII absorbers are absorption lines of singly-ionised Magnesium,
appearing in the spectra of distant, background, quasars. The absorbers arise
in gas in the haloes of galaxies that are between us and these background
quasars. The absorbers provide accurate redshifts for these galaxies, which
are in most case too faint to be detected by direct imaging and spectroscopy.

This PhD project is to investigate the cosmic web in the early universe using
this new probe. Aspects will include: the evolution of the cosmic web; the
largest structures; the size and shape of voids; the connection to structures
highlighted by quasars; the connection to superclusters; and the
correspondence to features in CMB temperature and lensing maps.

For details please contact Dr Roger Clowes at rgclowes[at]