PhD Opportunities |
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If either/both of the two PhD topics described below sound
interesting, and you are currently or soon to be suitably qualified
then please feel free to email me for further information.
The Assembly and Thermodynamics of Massive Galaxy ClustersGalaxy clusters are the most massive collapsed objects in the universe. They are dominated gravitationally by non-baryonic dark matter, and yet their presence is revealed primarily at optical and X-ray wavelengths via observations of baryons in the form of galaxies and hot intracluster gas respectively. Clusters are therefore fascinating physics laboratories offering much cosmological insight. For example, although there is much evidence for the existence of dark matter, the dark matter particle has yet to be identified and the relevant physics is largely unconstrained. Unsurprisingly, it is also not known how the baryons and the dark matter influence each other, especially when clusters merge with one another and subsequently re-acquire an equilibrium state. Many cosmological experiments plan to count the number of clusters as a function of redshift and then to relate baryon-based cluster observations to cluster mass (the key quantity for cosmological constraints) by assuming that the clusters are in equilibrium. Dr. Smith has shown that this process is fraught with unquantified systematic errors and that explicit testing of the relevant assumptions is pivotal to future progress [Paper#1]Dr. Smith and his collaborators (based in Hawaii, Marseilles, Durham, Stanford, and Rome) are conducting a multi-wavelength study of the assembly and thermodynamic history of massive clusters using data acquired from space (using the Hubble Space Telescope and the Chandra and XMM X-ray observatories) and from the ground (e.g. the W.M. Keck Observatory). The Hubble and Keck data provide the cleanest available view of the spatial distribution of dark matter in the clusters via gravitational lensing. The light paths from galaxies closely aligned with our line-of-sight through these clusters are so grossly distorted by the intervening gravitational potential of the clusters that several images of the same galaxy are formed. Analysis and modeling of the gravitational lensing signal leads to the generation of dark matter maps which can then be analysed in conjunction with the baryonic tracers to investigate the relationship between dark and luminous material in clusters [Paper#2]. The scientific focus of this PhD project will be to study the interplay between baryons and dark matter in clusters as outlined above. Several opportunities currently exist, for example: analysis of the rich datasets currently in hand (including those in the Hubble data archive), development of new gravitational lens modeling algorithms, and interpretation of results using state of the art theoretical simulations. The project will also involve proposing for new observational data and, all being well, suffering acute jet lag whilst collecting such data. Collaboration with members of Prof. Ponman's group here in Birmingham on the joint analysis of gravitational lensing and X-ray data is also likely. Galaxy Formation Studies With Gravitational TelescopesGalaxy Clusters are powerful gravitational lenses, producing multiple images of galaxies that are closely aligned with our line-of-sight through the foreground clusters (see also "The Assembly and Thermodynamics of Massive Galaxy Clusters"). The critical aspect of gravitational lensing in the context of studying these lensed galaxies is that the multiple images are also magnified, sometimes by factors as large as 100. This means that distant galaxies can be studied in far greater detail through galaxy cluster lenses than with conventional observations. The clusters effectively increase the light collecting power of man-made telescopes, hence the terms "gravitational telescope", "cosmic microscope" and similar [Paper#3, Paper#4, Paper#5]Exciting current and imminent developments in this field include: * mid-infrared studies of Luminous Infrared Galaxies at z>2 with the Spitzer Space Telescope; * searching for the first generation of galaxies to form after the big bang (z>7); * study of new gravitational telescopes uncovered with the latest generation of wide-field panchromatic surveys; * 3-dimensional spectroscopy of galaxies out to z=5 using integral field spectrographs at the W. M. Keck (Hawaii), Gemini (Hawaii and Chile) and European Southern Observatories (Chile). This project will commence with basic familiarisation with the lens modeling techniques common to all of the projects listed above. The student would then progress toward detailed study of one topic from this list. The observations and modeling techniques required to exploit gravitational telescopes have much in common with the lensing aspects of the "Assembly and Thermodynamics of Massive Galaxy Clusters" project described above. There may also therefore be opportunity to publish on the subject of galaxy clusters themselves as part of this project. Prominent among the collaborators involved in these projects are those at the California Institute of Technology, the University of Durham, the University of Arizona and Laboratoire d'Astrophysique de Marseilles. |
| Composed by: Graham P. Smith ©2005 | ||
| School of Physics and Astronomy, University of Birmingham, Edgbaston, Birmingham, B15 2TT, England. | ||
| Email: gps@star.sr.bham.ac.uk | Tel: +44 121 414 4600 | Fax: +44 121 414 3722 |