The current generation of deep multi-waveband surveys cover enough sky area to contain perhaps 1000s of strong gravitational lenses. By magnifying background distant galaxies in both flux and size (see Figure), these systems allow detailed studies of distant galaxies with current telescopes without waiting for next-generation facilities. These observations are needed to determine a key unknown in our Universe: how gas turned into stars in the early Universe.
The problem is in identifying these lenses because most are likely to be invisibly faint at optical wavelengths. The Herschel Satellite - to be launched in 2009 - is argued to have unique capabilities to pinpoint these objects because it will probe sub-millimetre wavelengths where distant star-forming galaxies will be bright, and the flux boost due to gravitational lensing means that perhaps half of all the objects detected will be gravitationally lensed.
The main purpose of this project is to find and characterize this population without waiting for the full release of any Herschel data. This will be made possible by developing a new approach to 'photometric redshifts' using radio (GMRT) data as the finding survey, near-infrared surveys with VISTA (in Chile) to constrain redshifts,and follow-up spectroscopy and high-resolution imaging with the world's largest telescopes.
The first year will be largely spent leading the observing and analysis of GMRT data. Most of the Herschel lenses should be easily detectable at the low radio frequencies probed by the GMRT. Our collaboration has been successful in obtaining a lot of time on the GMRT, and has developed a unique data reduction pipeline; first GMRT observations for this programme will be in Jan 2009.
The other task for the first year will be to develop a new and sophisticated `photometric redshift' code that will start with an input catalogue from the GMRT and then use near-infrared images, and those from complementary optical through X-ray facilities, to output probability distributions for the redshifts of the source of the radio emission and those of any potentially foreground lensing galaxies.
The second year will be spent applying this code to data from surveys to be carried out on the ESO VISTA telescope in Chile. The student will be expected to help in the collection and processing of these data, and will lead the application of the new photometric redshift code to these new datasets.
The third year will be spent following up the systems discovered.By default this will involve spectroscopy with giant optical and near-infrared telescopes. It may also involve using new facilities as they come on line like e-MERLIN (for high-resolution radio imaging), Herschel,and potentially even ALMA, ASKAP and MeerKAT.
If you are at all interested in this project
please contact any or all of the supervisors directly via email at the addresses
given below.
Steve Rawlings is Head of Astrophysics at Oxford.
Hans-Rainer Klöckner is a Postdoctoral Reseacher in Oxford, and is the SKA Design Study (SKADS) science simulations organiser throughout Europe.
Tom Mauch is a Postdoctoral Reseacher in observational cosmology at Oxford, and is expert in designing and undertaking large surveys at radio and optical wavebands.
Matt Jarvis is an RCUK Fellow and proleptic Lecturer at the University of Hertfordshire.
He is expert in observational extragalactic astronomy and PI of large surveys with the GMRT, Herschel
and VISTA.