Studying the very high redshift universe with gravitational telescopes
OKC colloquia
Tuesday 16 November 2010
from 13:15
to 14:15 at
FA32
Speaker :
Johan Richard (Dark Cosmology Centre, Copenhagen)
Abstract :
Characterizing the nature, physical properties, and epoch of formation of
the sources responsible for cosmic reionisation is one of the latest
challenges of modern cosmology. Extending the searches beyond z~6.5 and
back to ages where the Universe re-ionised requires extremely deep
observations in the near-IR bands. Until the construction of JWST and
20-40 meter class ground-based telescopes, gravitational lensing surveys
offer the only possibility of spectroscopically verifying the presence of
an abundant population of low-luminosity sources. I will present the
results of several projects targetting lensing clusters, aimed at
constraining the abundance of star-forming galaxies at z ~ 6-10 using
lensing magnification to improve the search efficiency and subsequent
spectroscopic studies. These surveys combine complementary approaches,
from the traditional "dropout" technique, applied on ground based images
obtained with VLT or high resolution HST imaging of the central regions
of the clusters, to a systematic search for low-luminosity
Lyman-alpha emitters with Keck/NIRSPEC, in the regions of maximal
magnification. In spite of the uncertainties inherent to the small areas
explored by these surveys, we demonstrate the practicality, over the next
few years, of providing a valuable glimpse at the nature of the z~10
Universe ahead of the commissioning of future large facilities such as the
ELT and the JWST.
