1. Goals for HETDEX Determine equation of state of Universe and evolutionary history for dark energy from 0<z<3. End-to-end test of cosmology by comparing fluctuations in CMB to those in baryons. Use a large field redshift survey from 2<z<4 to measure the power spectrum of baryons to 1% accuracy over a large k range. Current state of cosmologyRole of HETDEX

2. Hobby Eberly Telescope Dark Energy Experiment (HETDEX) HETDEX has the following observational parameters –200 sq. degrees area; 1.8 < z < 3.7; 5.2 Gpc 3 »Two 10x10 sq. deg. fields or strip 7x30 sq. degrees –Lyman-alpha emitters (LAE) trace large-scale structure »Expect 0.5 to 1 million tracers in volume –LAEs detected directly by a massive IFU-spectrograph VIRUS »20 minute exposures of each 18 arcmin diameter field, with ~1/9 fill factor on sky »~110 clear dark nights to complete » using the 9.2m HET and around 150 spectrographs –Sufficient volume and source density to provide independent constraints on H(z) and d A (z) at three redshifts ~1% precision –Unique in constraining w at low redshift while still allowing detection of higher redshift evolution

3. HETDEX strengths Survey efficiency –No setup time for targeting objects –No pre-survey to select targets Data are largely self-calibrating –Very good sky determination –Photometric calibration against SDSS stars in every observation LAEs are numerous –Biggest uncertainty is in N(z~2) and bias, but narrow-band imaging results are encouraging –need pilot survey with prototype VIRUS mounted on McDonald 2.7 m »survey a large enough volume to characterize the population »0.2 sq. deg 1.8 < z < 3.7 around HDF/GOODS-N »~5 million Mpc 3 10x larger volume than MUSYC LAE survey

4. Optical design of VIRUS module Spherical collimator mirror Fiber bundle VPH Grating 115 mm beam f/1.33 Camera 2kx2k CCD DEX science driver requires coverage of 340-570 nm at R~800 Flat mirror P. MacQueen

5. Layout of 143 IFUs >35000 fibers >14 million resolution elements per exposure Layout with 1/9 fill factor is optimized for HETDEX IFUs are separate, so can be reconfigured into denser pattern 20’ dia field New HET wide field corrector FoV 0.22 sq. arcmin per raster of 3 exposures 1 IFU with 246 fibers 145 IFUs with 35670 fibers

6. VIRUS –Each unit spectrograph »246 fibers each 1 sq. arcsec on the sky »Dither of 3 exposures gives 0.22 sq. arcmin and 340-570 nm wavelength range, R=850 –~140 VIRUS would cover »30 sq. arcminutes per observation »Detect 14 million independent resolution elements per exposure –Prototype of the industrial replication concept »Massive replication of inexpensive unit spectrograph cuts costs and development time »Prototype development at AIP »R&D with local industry Visible Integral-field Replicable Unit Spectrograph

7. Messung der dunklen Energie mit VIRUS und HETDEX

8. VIRUS on HET 145 VIRUS units will be housed in two “saddle bags” on the HET frame Fiber feed allows offloading of the mass of the instruments to this location

9. Assembly: fiber head Assembly: fiber slit

10. VIRUS Integral Field Unit An integral Field Unit reformats the sky to feed into the remote spectrograph Prototype-bundle of 246 fibers, constructed at AIP. Kelz, Bauer, Hill et al. (2006)

11. VIRUS-prototype on 2.7 m Smith Reflector „First (commissioning) light“ during July 2006

12. Luminosity Function of Ly  galaxies Peter Schuecker (MPE) Ralf Bender (USM/MPE) Ulrich Hopp (USM/MPE) Ralf Köhler (USM) Karl Gebhard (UT) Gary Hill (UT) Philipp McQueen (UT) Matthias Steinmetz (AIP) Peter Weilbacher (AIP) Joris Gerssen (AIP) -> Baryon oscillation (HETDEX) pre.-HETDEX science using PPak at Calar Alto