NOAO >   Observing Info >   Approved Programs >   2012A-0274

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Proposal Information for 2012A-0274


PI: Ryan Cooke, Institute of Astronomy, rcooke@ast.cam.ac.uk
Address: University of Cambridge, Madingley Road, Cambridge CB3 0HA, UK

CoI: Max Pettini, IoA, University of Cambridge

Title: The Physical Properties of Near-Pristine Gas at High Redshift

Abstract: High redshift damped Lyman alpha systems (DLAs) with metallicities less than 1/100 of solar are near-ideal environments for probing the nucleosynthesis by some of the first structures to form in the Universe. As part of our on-going survey of metal-poor DLAs, we have recently discovered a handful of quiescent DLAs that exhibit enhanced C/Fe ratios, with abundance patterns that are consistent with models of Population III star nucleosynthesis. Aside from their value as probes of the earliest episodes of star formation, the quiescent kinematics of these DLAs (\sigma ~ 2 km s^-1) provide us with a rare opportunity to decouple the turbulent and thermal broadening within the clouds by performing a differential analysis of the line widths for atoms of widely differing mass (such as deuterium and silicon). This will allow us to measure the gas temperature of these cold, near- pristine clouds of gas - a task that cannot be accomplished with other DLAs. By also measuring the gas density from the ratio of successive ion stages for multiple ions, we can begin to understand their origin and evolution, as well as the processes that heat and cool these clouds. As an additional bonus, we will also obtain two new measures of the primordial abundance of deuterium, building on the still meagre sample of such data from which the density of baryons in the Universe can be determined independently of CMB fluctuations.


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NOAO >   Observing Info >   Approved Programs >   2012A-0274

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