Research
My research uses observations of the Cosmic Microwave Background, combined with other astronomical tools such as the clustering of galaxies, to understand the contents and evolution of the universe.
In our model in cosmology, everything we see today came from a hot dense Big Bang, an extreme compression of space. As space expanded, tiny irregularities in an otherwise featureless universe evolved over billions of years to form cosmic structure, including galaxies, stars, and planets.
The universe only appears to be made of 5% normal matter, and I am trying to understand the missing 95%: Dark Energy and Dark Matter. I am also working to understand the physics of the very early universe, to find out if ‘inflation’ happened, an extremely rapid expansion of the universe in the first trillionth of a second.
Science Oxford talk on Dark Universe, and interview clip.
Main research topics
Cosmic Microwave Background
Dark Energy and Dark Matter
Early universe, cosmic inflation
Galactic and extragalactic foregrounds
Atacama Cosmology Telescope (ACT) and ACTPol
The Atacama Cosmology Telescope (ACT) is a six-metre NSF-funded telescope in the Atacama Desert in Chile. From 2007-11 it measured the CMB anisotropy at arcminute scales over hundreds of square degrees of sky.
These high resolution observations of the CMB signal allow us to better constrain cosmological models, and provide a window on new types of secondary measurements that allow us to probe the evolution of structure at late cosmic times. These include the Sunyaev-Zel’dovich effect as a probe of massive galaxy clusters, and gravitational lensing of the CMB by large-scale cosmic structure. At Oxford we are working on modeling and cosmological interpretation of the ACT data.
Oxford team members: Dunkley, Louis, Calabrese, Addison.
Discovery channel clip on ACT
ACTPol is an NSF-funded upgrade to ACT, due online 2012, to measure the polarization of the CMB at small-scales. It will target neutrino and Dark Energy properties through gravitational lensing, and early universe physics through the primordial CMB signal.
ESA’s Planck satellite is the third generation CMB satellite, following COBE and WMAP. It launched in May 2009, and is making full-sky observations of the CMB temperature and polarization anisotropies. It will allow us to test theories of the early universe and better understand the origin of cosmic structure. In Oxford we are members of the High Frequency Instrument team (HFI, measuring the microwave sky in the 100-857 GHz range), and Low Frequency Instrument (30-70 GHz). Oxford team members: Dunkley, Calabrese, Armitage-Caplan.
The first Planck results were released in early 2011. Among many exciting discoveries, measurements of distant galaxies have shed new light on when and where ancient stars formed in the early universe.
Planck data: Early Release Compact Source Catalog
WMAP is a NASA satellite mission that launched in 2001 and has measured the CMB anisotropy over the whole sky with high sensitivity, playing a key role in establishing the current cosmological model. I have been a member of the Science Team since 2006, working on cosmological parameter estimation, as well as modeling and analysis of Galactic foregrounds. WMAP completed its 9th year of observations in September 2010. The final data analysis is underway. Oxford team member: Dunkley.
Seven-year data on LAMBDA: http://lambda.gsfc.nasa.gov/
Wilkinson Microwave Anisotropy Probe (WMAP)
In addition to analysis and interpretation work, I am also collaborating on a number of more theoretical projects connected to observations.
These include modeling the emission from high redshift star-forming galaxies, and modeling the Galactic magnetic field to predict polarized synchrotron and dust emission. I am also investigating how gravitational lensing of the CMB can be used to better understand Dark Energy. I also work on MCMC techniques for sampling high dimensional probability distributions, and other related statistical problems.
Theoretical work
The Planck satellite
Image courtesy the NASA/WMAP Science Team.
Image courtesy ESA, HFI and LFI consortia.
Image courtesy ESA, HFI and LFI consortia.
Credit: Sloan Digital Sky Survey Team, NASA, NSF, DOE.
Image courtesy ESA, HFI and LFI consortia.