Extragalactic Astrophysics and Cosmology at Imperial College London

Lead Research Organisation: Imperial College London
Department Name: Dept of Physics


Our work in the Astrophysics Group at Imperial College London, in the broadest terms, is aimed at improving our understanding of the evolution of the Universe. The basic framework is the Big Bang model, the picture that the Universe began in a hot violent explosion several billion years ago. As the Universe expands it cools, and under the force of gravity matter segregates and condenses to form galaxies composed of stars. Our current picture of the Universe has changed dramatically in recent decades, both observationally and theoretically. The most important observational improvement has been the development of telescopes that map the sky over the complete range of wavelengths, both shorter than visual - gamma-ray, X-ray, ultraviolet - and longer than visual - infrared, microwave, radio. Two surprising results have emerged from these observations. First, there must be much more matter, dark matter, in the Universe than we can see, to explain the strong gravitational pull of galaxies. Second, the expansion of the Universe is accelerating, which we can only understand if empty space (the vacuum, nothing) possesses energy, dark energy. The aim of our work at Imperial College London, then, is to undertake observations and theoretical studies to develop this picture of the evolution of the Universe in more detail. We can order our research by wavelength, starting with X-rays. The shorter the wavelength of light, the higher the energy of photons, so X-rays can be used to study the most energetic processes in galaxies, particularly the accretion of matter onto black holes, and we are using the XMM-Newton satellite to explore these extreme environments. There is a very massive black hole, over a million times the mass of the Sun, at the centre of most galaxies, and a recent discovery has been that the mass of the black hole is proportional to the mass of the galaxy in which it lies. Our work using the Chandra satellite is aimed at understanding why this is and the implications for how galaxies form. At near-infrared wavelengths we are taking advantage of a new generation of large detectors to make a deep map of the sky, and are using this survey to search for distant quasars. The expansion of the Universe stretches (redshifts) the light from far away sources, so the most distant sources are the most redshifted. Light from the furthest quasars, from the time when they were first forming, is stretched to the near-infrared. By discovering the first quasars we can analyse their light to tell us about the conditions at that time, when the Universe was only 5% of its present age. Although stars emit most of their light near optical wavelengths, an important development in the 1980s and 1990s was the discovery that much of this light is hidden by the smoke from burning stars ('dust' to astronomers). The light is absorbed by dust and re-emitted at far-infrared wavelengths. About half of all starlight emerges at far-infrared wavelengths, so we need to study galaxies at these wavelengths to make a complete census of where and when the stars we see today formed. To this end over the next few years we will be analysing far-infrared maps made with the Herschel satellite, due to be launched in 2008. Finally, at microwave wavelengths we can see the furthest back in time, to the point when the Universe was so hot that matter was in the form of a plasma. In effect the entire sky looks like the surface of the sun, but that light has been redshifted by a factor of 1000, and stretched to microwave wavelengths. Analysis of the subtle variations in temperature of the microwave sky can provide a measurement of the amount of dark matter and dark energy. The launch of the Planck satellite in 2008 will provide the most detailed maps yet of the microwave sky. We will analyse the structure in these maps to obtain the most accurate measure of these cosmological parameters.


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Leggett S (2009) THE PHYSICAL PROPERTIES OF FOUR ~600 K T DWARFS in The Astrophysical Journal

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{Ashdown}, M. And {Aumont}, J. And {Baccigalupi}, C. And {Banday}, A. And {Basak}, S. And {Bernard}, J.-P. And {Betoule}, M. And {Bouchet}, F. And {Castex}, G. And {Clements}, D. And {Da Silva}, A. And {De Zotti}, G. And {Delabrouille}, J. And {Dickinson}, C. And {Dodu}, F. And {Dolag}, K. And {Elsner}, F. And {Fauvet}, L. And {Fay}, G. And {Giardino}, G. And {Gonzalez-Nuevo}, J. And {le Jeune}, M. And {Leach}, S. And {Lesgourgues}, J. And {Liguori}, M. And {Macias}, J. And {Massardi}, M. And { (2012) PSM: Planck Sky Model

Description understanding of the Universe. computational tools
Sector Education,Other
Impact Types Cultural,Societal

Description Planck 
Organisation European Space Agency
Country France 
Sector Public 
PI Contribution We are a data processing centre for the HFI Instrument on the Planck Satellite, responsible for determination of focal-plane and beam-shape parameter estimation. We also contribute heavily to various science products.
Collaborator Contribution This is a huge EU project.
Impact Lots of papers. Planck data products.
Description Big Bang Fair 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? Yes
Type Of Presentation Workshop Facilitator
Geographic Reach International
Primary Audience Schools
Results and Impact It's an exhibition - does not match any of the types of presentation listed.

It is aimed at all school ages and adults as well, but I'm not allowed to select such a mixture.

Over 30000 attended this year
Year(s) Of Engagement Activity 2009,2010,2012,2013
Description Planck 2011 
Form Of Engagement Activity A press release, press conference or response to a media enquiry/interview
Part Of Official Scheme? No
Type Of Presentation Keynote/Invited Speaker
Geographic Reach International
Primary Audience Public/other audiences
Results and Impact BBC World News channel segment

Year(s) Of Engagement Activity 2011
Description Royal Society Summer EXHIBITION 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? Yes
Type Of Presentation Keynote/Invited Speaker
Geographic Reach International
Primary Audience Public/other audiences
Results and Impact Audience type is *alll* of the above

Resulted in media appearances. >10000 at actual show, >100000 accessed website.
Year(s) Of Engagement Activity Pre-2006,2009,2012,2013