Unveiling the Hidden Universe - From the First Galaxies to Brown Dwarfs

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We propose a scientific programme that uses three revolutionary new instruments. The Planck Surveyor will map the cosmic microwave background radiation. The Herschel Space Observatory and the SCUBA-2 camera on the James Clerk Maxwell Telescope will observe the universe in the submillimetre waveband, which is still largely unexplored and which probably holds the answers to the questions of the origins of the stars and galaxies. These questions, of course, are two of the biggest ones in astronomy, and the reason we don't yet have very good answers is interstellar dust, the tiny solid particles that fill interstellar space and which, like smoke, hide optical light. This dust is a particular problem in studying the formation of stars and galaxies, which happens in regions where there are especially large amounts of gas and dust - and so the youngest stars, for example, are completely hidden from the view of normal optical telescopes. Fortunately, the dust is warmed by the absorbed optical radiation and then emits submillimetre radiation, and so by observing the submillimetre radiation we can study the objects that are hidden by the dust. Our group will use Herschel and SCUBA-2 for a number of large projects to investigate the origin of stars and galaxies. For example, we are leading a project to use SCUBA-2 to observe the youngest stars in the Gould Belt, a ring of nearby molecular clouds, the birthplaces of stars, that circles the sky. We are also part of international teams that will use Herschel to study the same molecular clouds and also to map a large part of the Milky Way in this waveband. We will study the origin and evolution of galaxies using another observational trick: the fact that by looking out into space we are also, because of the finite speed of light, looking back in time. In four huge Herschel projects, three of which we are leading, we will study galaxies from ones in the nearby universe to ones ten billion light years away, which will allow us to study the evolution of galaxies over ten billion years of cosmic history, and especially their birth. Finally, in another Herschel project, we will study the origin of the dust itself, and determine whether dust is formed in the atmospheres of old stars or whether it is formed in supernovae, the colossal explosions that end the lives of massive stars. We will also carry out a set of parallel theoretical programmes to address these questions. For example, we will carry out computer simulations of the formation of both stars and of prestellar cores, which are the densest parts of molecular cloud and the places where the stars actually form. Any computer simulation is necessarily built on a number of assumptions about the way in which stars form, and by comparing the predictions of the simulations with the results of our SCUBA-2 and Herschel surveys, we will test whether these assumptions are correct. The Planck Surveyor will extend the time-machine trick to a time only 400,000 years after the big bang, which is when the cosmic background radiation was emitted. Because this radiation has been travelling in a straight line for almost 14 billion years, its variation over the sky reveals the tiny differences in density that existed in the universe at this time - differences that eventually after 14 billion years (and the effect of gravity acting during this period) turned into the lumpy universe we see around us today. We will use this window into the early universe in two ways. First, using some new statistical techniques we have developed, we will use the properties of the cosmic background radiation to determine the type of universe we live in. Second, by studying the scattering of this radiation by the gas in rich clusters of galaxies, we will study the evolution of clusters over the last 14 billion years.