DESpec: Spectroscopic upgrade of the Dark Energy Survey

Dark Energy is one of the biggest mysteries in the whole of science. Observations over the past decade strongly favour a 'concordance' model in which the Universe is flat and contains approximately 4% ordinary atomic matter, 21% Cold Dark Matter and 75% Dark Energy. The Dark Energy paradigm and its extensions pose fundamental questions about the origins of the Universe: is Dark Energy an actual ingredient, or should Einstein's gravity theory be modified?

We propose a new initiative, the Dark Energy Spectrometer (DESpec), a 4000-fibre instrument for the Blanco 4-meter telescope in Chile that would take advantage of the infrastructure recently built for the Dark Energy Camera to achieve excellent science at low cost Starting in 2017, when the Dark Energy Survey (DES) is completed, DESpec would obtain spectroscopic redshifts for ~10 million galaxies from DES+VISTA Hemisphere Survey (VHS) and thereby improve our measurement of Dark Energy. DESpec will also constrain neutrino masses, enable new techniques such as redshift-space distortions to constrain Dark Energy vs. Modified Gravity models, and enable powerful studies of galaxy evolution. UK involvement would allow for the design to be harmonized with the needs and leadership roles of the UK astronomy community. As with DES, the UK investment would be highly leveraged by partnership with the US and other foreign partners. The total DESpec instrument cost is estimated at $40M, similar to DECam. The requested funding covers both instrumentation and and preparations for target selection and survey strategy. The work is fully coordinated with the work for BigBOSS:UK, another proposed spectroscopic instrument.

The DESpec project will develop the skills of Post-docs and technical staff.

In particular, the work on simulations for target selection and survey strategy will be of use not only for DESpec, but also for a number of other planned spectroscopic surveys.

The Opto-Mechanical design and specification of the fibre imaging system will have broad implications for optical systems.