Ikerbasque researcher: Tom Broadhurts
We aim to understand better the nature of dark matter
You were recently awarded time to use the Hubble Space telescope, what is it you are looking for?
My work with gravitational lenses has just received a serious boost with over one million seconds of exposure time granted on the Hubble Space Telescope, which will point the most powerful man-made telescope at largest natural cosmic telescopes to peer as deeply as possible into the early Universe.
This proposal makes use of the Advanced Camera which I helped to develop with colleage at JHU in Baltimore and which was sucessfully installed by the NASA space shuttle mission in 2004. We aim to understand better the nature of dark matter and to search for galaxies in formation when the Universe was very young. Natures telescopes are the giant clusters of galaxies - the largest graviationally collapsed objects to have formed in the Universe, with central densities exceeding the critical value required for bending light of background galaxies into "Einstein rings".
Seeingly all distant clusters are dense enough to create several stretched copies of magnified galaxies lying in the background. Although this lensing phenomenon can be explained by Einsteins general theory of relativity, the formation of multiple images was not anticipated in this context, requiring copius amounts of unseen "dark matter" dominating the masses of these clusters.
The hot X-ray emitting gas and the many many stars present in a giant cluster accounts for only a few percent of the mass inferred from lensing, leaving us at a loss to understand what sort of material comprises the majority of matter in galaxy clusters, and even to contemplate modification of General Relatively. This conclusion is supported by the speedy motions galaxies in clusters which move around randomly at ~1000km/s, and also by the very high temperature of the gas which is in equilibrium at ~10 million degrees Kelvin, balencing a very deep gravitational potential.
Curiously, our first results from Hubble and other telescopes in Hawaii have uncovered that clusters of galaxies are surprisingly more concentated than prediced, implying that structure in the Universe may have collapsed earlier than predicted in the standard cosmological model, a result which we look forward to exmaning fully as the data comes in over the next three years.
How has your research momentum been affected by moving to the Basque Country?
I'm enjoying a smooth continuation of my research work thanks to the generous welcome by the theoretical physics department at UPV, where charming individuals have gone out of their way to accommodate many Ikerbasque researchers with office space, computers, help with grant applications and important opportunities for collaboration. Together each day we all enjoy a good lunch provided by the school of gastronomy, making for a relaxing break from rigourous forefront research.
Crucially for my family the complexity of settling in Spain has been eased greatly by the capable Ikerbasque team, to whom we are sincerely grateful for sorting out tricky problems like residency permits and import tax duties. Also we have found people in Bilbao to be helpful and honest, with love of children - our new child was born here only 6 months ago and is thriving well - it would be really hard to imagine a better place to raise a family.
How do you see your research developing at UPV with your Ikerbasque position?
At the moment, together with my collegue Ruth Lazkoz at UPV we are analysing the new Hubble results and planning other approved complementary surveys for a definative comparison with a range of theoretical models describing the formation of structure in the Cosmos, combining experimental and theoretical expertise. We very much hope to provide a real center for cosmology here, with students and postdocs involved with forefront data to foster a new generation of research scientists in the Basque country.