PATT Linked Grant Support for the Bristol Astrophysics Group

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The Bristol Astrophysics Group works on a number of programmes that require careful observations to be made with the world's largest telescopes. This proposal requests two years of funding for travel to those telescopes and subsistence while working at them. In studies on the microwave background radiation, the left-over radiation from the Big Bang, it is important to remove contamination from foreground sources of emission that confuse our measurements of the background itself. This is done using a series of observations at radio-telescopes in the USA and elsewhere. Many of the measurements relate to the 'shadows' cast on the microwave background by clusters of galaxies. Extensive radio and optical studies of those clusters, to understand their masses and to gain insights into how they formed, are also a significant part of our work. Our work on active galaxies, which host very massive black holes in their nuclei, is principally done using orbiting X-ray telescopes, but to understand the physics of the emission it is essential to see also the emission in the radio, infra-red, and optical bands. Here again Group members make extensive use of telescopes world-wide, from the radio interferometers in Australia to optical telescopes in Chile. Small-scale models of these active galaxies can be found in our own Galaxy, in black hole systems with masses a few times the mass of the Sun. Work on these systems is done in the same way as for the active galaxies, with the extra requirement to follow rapid changes in the brightness of emission from matter near the black holes that tell us about the physics of the infall of matter and the associated ejection of high-speed flows. A unifying thread of our extragalactic work is on how structure in the Universe forms and changes over time. A large fraction of our observing is therefore dedicated to finding and characterizing the earliest galaxies and clusters, and then seeing how the most distant galaxies and clusters differ from those closer to us, which are therefore seen later in the life of the Universe, and so are older. A wide range of ground-based telescopes has to be used in this work, from the radio to the optical, with much of the work using the telescopes of the European Southern Observatory in Chile. Nearby galaxies can be studied in more detail than the more distant ones, and we also look at the populations of galaxies nearby - especially those of the lowest mass, which dominate the galaxy population by number, and have properties that can be quite different from their more massive cousins. Finally, we also work on our own Galaxy, looking at the gas between the stars, which has been heated by supernovae or young stars, and at the dense lumps of gas that emit coherent (maser) radiation.