Two new Durham-led programmes on Hubble Space Telescope.

Durham researchers lead two successful proposals for NASA's Hubble Space Telescope in the recently announced proposal round. Together these projects will provide 42 orbits of spacecraft time to pursue two science programmes on this world-leading facility, representing an investment of around $US 4-M in Durham research.

The first programme, led by Durham graduate student Nicolas Tejos, will use the far Ultra-Violet (UV) spectrograph on the Hubble Space Telescope to detect the inter-galactic medium (IGM) associated with large-scale structure of the Universe. Astronomers believe that galaxies roughly trace the filamentary structure of matter in the Universe predicted by cosmological simulations, but very little is known about the actual material within this 'cosmic web'. Given the extremely low densities of the IGM, the only way to observe it is by looking at the absorption from this material in the spectra of bright, background sources such as distant Quasars. We have carefully chosen a single Quasar whose line-of-sight intersects six cosmological filaments. Such filaments can only be accurately traced in the local Universe, but the resulting absorption features then fall in the UV, where the Earth's atmosphere is opaque, requiring the use of a space-based observatory to detect them. We will use 12 orbits with Hubble to observe the absorption signatures of the IGM associated to these filaments. We also expect to observe portions of the warm-hot IGM, which has been very hard to detect, but is expected to account for a significant fraction of all the normal matter in the local Universe.

The second programme, a survey led by STFC Fellow Mark Swinbank at Durham, will study the nature and morphologies of distant sub-millimetre galaxies with the Wide Field Camera 3 instrument on Hubble. Discovered by astronomers in Durham over a decade ago, sub-millimetre galaxies represent an important population in the young Universe. These galaxies, seen around 10 billion years ago, are undergoing tremendous bursts of star formation, forming stars at a rate 500 times faster than the Milky Way today. They are thus thought to represent the formation phase of the most massive galaxies we see in the Universe today. Our view of the sub-millimetre galaxy population has been radically altered by a new Durham-led programme on the recently commissioned Atacama Large Millimeter Array (ALMA) whose impressive resolution and sensitivity has for the first time precisely located 100 examples of these galaxies. As part of an on-going programme to study this unique sample of distant, luminous galaxies, we have been awarded 30 orbits with the Hubble Space Telescope to identify the mechanisms which trigger their intense starbursts.