- Yanchuan Cai, Durham University
Talk: Combining photo-z and spec-z surveys: Constraint on linear growth
May 30, 2012 (2:30 PM - 3:00 PM)
PDF, 1.77 MB
Redshift space distortion is a powerful way of measuring the growth of structure and testing General Relativity, but it is limited by cosmic variance and the degeneracy between the galaxy bias b and the growth rate factor f. The cross-correlation of lensing shear with the galaxy density field can measure b in a manner free from cosmic variance limits, breaking the f - b degeneracy and allowing inference of the matter power spectrum from the galaxy survey. Constraint on the linear growth of structure may benefit from combining a weak-lensing photo-z survey with a spectroscopic galaxy redshift survey.
- Donnacha Kirk, Imperial College London
Talk: DES/DESpec WGL & RSDs on the same sky
May 30, 2012 (3:30 PM - 4:00 PM)
PDF, 1.13 MB
I will present forecasts for DES + DESpec, concentrating on cosmic shear from DES & galaxy clustering including RSDs for DESpec with particular attention on the issue of cross-correlations when the survey areas overlap.
- Jeffrey A Newman, U. Pittsburgh / Pitt-PACC
Talk: Photometric Redshift Calibration with Wide-Area Surveys
May 30, 2012 (11:00 AM - 11:20 AM)
PDF, 4.16 MB
Many of the cosmological measurements to be performed with future wide-area photometric surveys such as DES and LSST will require extremely well-characterized photometric redshifts. A conventional approach is to calibrate these photo-z's using large sets of spectroscopic redshifts; however, even for objects 1.5 magnitudes brighter than DES will reach, current surveys on 8-10m telescopes only obtain secure redshifts for 40-70% of targeted objects. As a further complication, in most surveys the majority of these secure redshifts are in categories with a ~5% failure rate, significantly degrading their use for precision calibration. A powerful alternative approach is to exploit the clustering of galaxies. Measuring the two-point angular cross-correlation between objects in a photometric redshift bin and objects with known spectroscopic redshift, as a function of the spectroscopic z, allows the true redshift distribution of a photometric sample to be reconstructed in detail, even if it includes objects too faint for spectroscopy or if spectroscopic samples are highly incomplete (and only the most secure redshifts are utilized). A wide-area survey with ~100k objects within a 500-1000 square degree region would be more than sufficient to calibrate photometric redshifts for DES or LSST. Combining photometric and wide-area spectroscopic surveys in the same region of sky will be a powerful tool for future cosmological experiments.
- Bob Nichol, ICG Portsmouth
Remote talk: The latest from BOSS and eBOSS
May 31, 2012 (9:00 AM - 9:30 AM)
PDF, 2.79 MB
The BOSS collaboration is making great progress and has just released the first significant cosmology results (see Anderson et al. 2012). I will review the highlights of this on-going survey including plans for the next generation of dark energy surveys with SDSS e.g. eBOSS. I can also give a brief overview of WEAVE which is a UK-led multi-object spectroscopic survey using the WHT.
- Will Saunders, Australian Astronomical Observatory
Talk: Mohawk - a 4000-fiber positioner for DESpec
May 31, 2012 (1:50 PM - 2:10 PM)
PDF, 2.82 MB
DESpec requires a 4000-fiber positioner, with a pitch under 7mm, and a curved focal plane. We have carried out a feasibility study into adapting existing AAO 'tilting spine' designs to this geometry, and no show-stoppers have been identified. The proposed design is also simpler and more modular than previous designs.
- Will Saunders, Australian Astronomical Observatory
Talk: A fast new reflective design for fiber-fed spectrographs
May 31, 2012 (4:30 PM - 4:50 PM)
PDF, 0.4 MB
A new design is presented for fibre-fed optical spectrographs. The design is a Schmidt/Maksutov variant, but with the focal plane close to the spectrograph pupil. This means it is possible to hide the detector package almost entirely within the shadow of the top end obstruction of the telescope. This allowing a very high efficiency, competitive with transmissive designs. The optics are superb, as least as good as classic Schmidt designs, allowing f/1.2 or faster cameras. For DESpec, this means the entire wavelength range can be accommodated on a single 4Kx4K detector at the required resolution.
- Michael Seiffert, Jet Propulsion Laboratory
Talk: The Subaru Prime Focus Spectrograph (PFS)
May 31, 2012 (2:10 PM - 2:30 PM)
PDF, 2.65 MB
The Prime Focus Spectrograph (PFS) is a fiber fed multi-object spectrograph for the Subaru Telescope that will conduct targeted surveys for studies of dark energy, galaxy evolution, and galactic archaeology. I will discuss the planned surveys, the top-level instrument requirements, and the baseline instrument design. The key to the instrument is a high-density array of 2400 fiber positioners placed at the prime focus of the Subaru Telescope. The fiber positioners cover a 1.3 degree field of view and feed a set of 4 spectrographs covering 400 nm to 1.3 microns. PFS will comprise a system with an unprecedented combination of high-multiplex factor, observing efficiency, and aperture on the Subaru telescope.
- Michael A Strauss, Princeton University
Talk: Sumire and LSST
May 31, 2012 (9:30 AM - 9:50 AM)
PDF, 24.73 MB
I will discuss two projects that have the potential to be strongly synergistic with DESpec. SuMIRe (Subaru Measurements of Images and Redshifts) will use the Hyper SuprimeCam, a 1.7 deg^2 imaging camera on the Subaru 8.2m telescope, to carry out a layered survey of the sky to study weak lensing and galaxy evolution. The Prime Focus Spectrograph (PFS) will have 2400 fibers over 1.3 deg^2, and wavelength coverage from 0.38 to 1.3 microns to measure galaxy redshifts from z=0 to z=7 with no gaps. The Large Synoptic Survey Telescope (LSST), a 6.7-meter telescope with a 9.6 deg^2 field of view, will be dedicated to a ten-year survey of the sky starting in 2021, reaching to r=27.5 over 20,000 deg^2 of the Southern sky.
- Molly Swanson, Harvard CfA
Talk: Probing Dark Energy with Weak Lensing and Redshift Space Distortions
May 30, 2012 (4:00 PM - 4:30 PM)
PDF, 1.45 MB
I will discuss ideas on science projects to distinguish between dark energy and modified gravity using a combination of weak lensing data from DES and redshift space distortions from DESpec.