Photo-z for LRGs, DES, DUNE and the cross talk with Dark Energy Ofer Lahav, University College London 1. The Dark Energy Survey 2. Photo-z methodology 3. Photo-z and probes 4. Applications: LRGs, DES, DUNE mainly with Filipe Abdalla and Manda Banerji Ofer Lahav University College London
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Photo-z for LRGs, DES, DUNE and the cross talk with Dark Energy
Photo-z for LRGs, DES, DUNE and the cross talk with Dark Energy. Ofer Lahav, University College London. The Dark Energy Survey Photo-z methodology Photo-z and probes Applications: LRGs, DES, DUNE. mainly with Filipe Abdalla and Manda Banerji. Ofer Lahav University College London. - PowerPoint PPT Presentation
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Photo-z for LRGs, DES, DUNE and the cross talk with Dark Energy
Ofer Lahav,University College London
1. The Dark Energy Survey
2. Photo-z methodology
3. Photo-z and probes
4. Applications: LRGs, DES, DUNE
mainly with Filipe Abdalla and Manda Banerji
Ofer LahavUniversity College London
“Evidence” for Dark Energy
Observational data• Type Ia Supernovae • Galaxy Clusters• Cosmic Microwave Background• Large Scale Structure• Gravitational Lensing
Physical effects: • Geometry • Growth of StructureBoth depend on the Hubble expansion rate:
DES (NOAO) 5000 4 moderate 2008-2012? proposedPan-
STARRS ~10,000? 5? moderate 2006-2012? ~funded
LSST 15,000? 5? deep 2014-2024? proposed
JDEM/SNAP1000+ (space)
9 deep 2013-2018? proposed
VST/VISTA
DUNE
5000? 2010-2015?moderate 4+5 proposed
20000? (space) 2+1? moderate 2012-2018? proposed
Y. Y. Mellier
Photo-z / Cosmology Synergy
Large Scale Structure
Clusters of Galaxies
Simulations
Photo-z
Gravitational Lensing
The Dark Energy Survey
The Dark Energy Survey • Study Dark Energy using 4 complementary techniques: I. Cluster Counts II. Weak Lensing III. Baryon Acoustic Oscillations IV. Supernovae
• Two multi-band surveys 5000 deg2 g, r, i, z 40 deg2 repeat (SNe)
• Build new 3 deg2 camera and data management system Survey 2010-2015 (525 nights)
Blanco 4-meter at CTIO
300,000,000 photometric redshifts within a volume of 23 (Gpc/h)^3, out to z = 2
DES Organization
SupernovaeB. NicholJ. Marriner
ClustersJ. MohrT. McKay
Weak LensingB. JainS. Bridle
Galaxy ClusteringE. GaztanagaW. Percival
Photometric RedshiftsF. CastanderH. Lin
SimulationsA. KravtsovA. Evrard
Science Working Groups
DES:UK consortium:
UCL, Portsmouth, Cambridge, Edinburgh, Sussex
Over 100 scientistsin 17 institutionsIn the US, UK, Spain and Brazil
DES Status
• Low-risk, near-term (2010-15) project with high discovery potential• Survey strategy delivers substantial DE science after 2 years • Synergy with SPT and VISTA • Precursor to LSST, DUNE and JDEM• Total cost is relatively modest (~ $20-30M)
STFC approved £1.7M for the DES optical corrector, subject to funding in the US
Glass ordered by UCL in Sep 07 (funds from 5 universities) DES in the US President budget request for FY08 DOE CD1 approved; CD2/CD3 in Jan 08 NSF contribution to data management
DES Forecast Constraints
•DES+Stage II combined = Factor 4.6 improvement over Stage II combined•Consistent with DETF range for Stage III DES-like project•Large uncertainties in systematics remain, but FoM is robust to uncertainties in any one probe, and we haven’t made use of all the information
DETF FoM
DES Forecasts: Power of Multiple Techniques
FoM factor 4.6 tigther compared to near term projects
w(z) =w0+wa(1–a) 68% CL
Ma, Tang, Weller
Sources of uncertaintiesin measuring Dark Energy
• Theoretical (e.g. the cosmological model)
• Astrophysical (e.g. galaxy and cluster properties)
• Instrumental (e.g. image quality)
Photometric redshifts
• Probe strong spectral features (e.g. 4000 break)
z=3.7z=0.1
Photo-z –Dark Energy cross talk
• Approximately, for a photo-z slice:
(w/ w) = 5 (z/ z) = 5 (z/z) Ns-1/2
=> the target accuracy in w
and photo-z scatter z dictate the number of required spectroscopic redshifts
Ns =105-106
Cosmology from photo-z surveys
• Optimization of Photo-z for cosmic probes
• Photo-z mocks and algorithms
• Spetroscopic training sets
• MegaZ-LRG (DR6)
• DES
• VISTA
• DUNE
• other surveys
BAO, WL, neutrino mass, ISW,
halo parameters,…
Photo-z Challenges
• Optimizing hybrid methods - errors - pdf - ‘clippping’• Optimal filters• Spetroscopic training sets • Field vs cluster photo-z• Synergy with BAO and WL• “Self calibration” and “colour tomography”
Surveys (3-year initial programme):• WL survey: 20,000 deg2 in 1 red broad band, 35 galaxies/amin2 with median z ~ 1, ground based complement for photo-z’s
• Near-IR survey (J,H). Deeper than possible from ground. Secures z > 1 photo-z’s
Optical and Optical+NIR
QuickTime™ and aTIFF (Uncompressed) decompressor
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Abdalla, Amara, Capak, Cypriano, OL , Rodes astro-ph/0705.1437
DE FoM for DUNE with and without NIR
QuickTime™ and aTIFF (Uncompressed) decompressor
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NIR will improve FoM by 1.3-1.7
DE FOM vs number of spectra needed
QuickTime™ and aTIFF (Uncompressed) decompressor
are needed to see this picture.
Abdalla et al.
Photo-z Challenges
• Optimizing hybrid methods - errors - pdf - ‘clippping’• Optimal filters• Spetroscopic training sets • Field vs cluster photo-z• Synergy with BAO and WL• “Self calibration” and “colour tomography”