High-Redshift Radio Galaxies


High redshift (z > 1) radio galaxies (HzRGs) were initially discovered
via their extreme radio luminosities, their radio spectra, and often
double-lobed radio morphologies (Blandford & Payne 1982).  Observational
evidence unearthed in the last decade has unequivocally linked HzRGs to
the most massive galaxies at high redshifts, harbouring vast stellar
populations (M_star > 10^11 M_solar - Seymour et al. 2007) as well as
extremely active super-massive black holes (SMBHs) at their centers.
Furthermore, the presence of vast reservoirs of atomic and molecular
hydrogen have been established in a number of cases via observations of
strong HI absorption against the luminous, morphologically complex Lyα
haloes (Reuland et al. 2004), and from detections of CO (e.g.,
Papadopoulos et al. 2000) and dust (e.g., Dominika et al. 2012).

TG_fig1

According to currently favored models of galaxy formation, massive
galaxies are thought to attain their masses through a biased
hierarchical build-up within a ΛCDM cosmology. We would expect,
therefore, HzRGs to reside in the most over-dense regions of the early
Universe, and to provide powerful test-cases of the biased growth of
cosmic structures during the formative stages of the most massive
galaxies. In fact, a number of the most luminous HzRGs have been found
to be associated with over-densities of sources selected at optical,
sub-millimetre, and X-ray wavelengths (e.g., Stevens et al. 2003; De
Breuck et al. 2003; Greve et al. 2007; Humprey et al. 2011).

This project will carry out a systematic study of the large-scale
environments of ten HzRGs at redshifts ~2.5 and ~3.5, corresponding to
about 2.6 and 1.8 billion years after the Big Bang, respectively. Using
the submillimeter camera SCUBA-2 (observing at 450 and 850micron) on the
James Clerk Maxwell Telescope in Hawaii, we have obtained uniform maps
of a 15’ x 15’ region around each HzRG. This corresponds to a co-moving
area of about 7Mpc x 7Mpc, which is sufficiently large to encompass the
whole of the expected proto-cluster environment.

TG_fig2


The primary scientific goal of this project is first and foremost to
identify dusty star forming galaxies (DSFGs) within the SCUBA-2 maps,
and thus measure the over-density of such objects associated with the
HzRGs. Secondly, we will perform a statistical comparison of the average
amplitude of the overdensity at these two epoch, and contrast it with
predictions from cosmological simulations of structure growth and
evolution.

We plan interferometric observations of our discovered sources with the
Atacama Large Millimeter/sub-millimeter Array (ALMA) in Chile in order
to illucidate the detailed properties of their dust and gas content,
including their spatially resolved gas-kinematics, as well as the sizes
and masses of the galaxies.

Finally, we hope to push our surevey to higher (z~4) and lower (z~1.5)
redshifts in order to increase the baseline over which we can delineate
the growth and evolution in DSFG over-density around radio galaxies.


Page last modified on 06 jan 14 10:21 by Amira K F Val Baker