Transcript LSST-SNAP complementarity Reynald Pain IN2P3/LPNHE Paris, France R. Pain

LSST-SNAP complementarity
Reynald Pain
IN2P3/LPNHE Paris, France
R. Pain
9/18/2008
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LSST vs SNAP (and vice-versa)
True:
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Target Dark Energy (and Dark Matter) as primary science
Use wide field imager as (main) instrument
Hope to start operating in ~2015
Are competing for (some of) the same money
But …
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LSST & SNAP apparatus
• Primary mirror : 8.4 m
• Field-of-view : ~ 10 deg2
• 6 filters in the visible :
320 nm -> 1100 nm
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• Primary mirror : ~2m
• Field-of-view : ~ 1 deg2
• 6 filters in the visible :
320 nm -> 1100 nm
• 3 filters in NIR (->1700 nm)
• low-z spectrograph
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LSST & SNAP surveys
LSST Survey
SNAP Survey Area(sq.deg) Depth(AB mag) ngal(arcmin-2)
Deep/SNe
Wide
15
30.3
250
107
4000
27.8
100
108.5
26.7
40-50
109
Panoramic 7000-10000
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SNAP & LSST strategies for Supernovae
SNAP: Area : 2x7.5 sq. deg.
LSST: full sky, twice a week
Cadence : 4 days
=> 250000 SN/yr !
Imaging and spectroscopy
well measured subsample at z<1
Total nb of SN : ~ 2000
Need for “nearby” SN (ground)
Some DE models require SN at z>1
Light curve modeling requires lots of SN
Dust modeling requires IR meas.
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SNAP & LSST strategies for Weak Lensing
SNAP: increase the number of
resolved galaxies (spatial
resolution) and PSF stability
LSST: 200 exposures per sky patch
will yield negligible PSF induced
shear systematics
Cosmic shear signal
Stars
9-band photometry (incl NIR)
helps for phot-z
SNAP and LSST will have very
different systematic uncertainties
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LSST and SNAP
Rely on the same techniques (SN, WL, BAO, ..) to constraint DE
but use a very different instrumental approach
DE is a difficult measurement.
Improving on current (+ near future) constraints will be extremely
difficult and will in fine come to how well one does on
controlling the systematic uncertainties
LSST and SNAP are complementarity in particular when dealing
with systemactic uncertainties
Combined, they will yield improved constraints on
Dark Energy
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Cosmological parameters (1st year)
68.3, 95.5 and 99.7% CL
Green SNLS, Blue SDSS/BAO 2005
WM = 0.271 +/- 0.021 (stat) +/- 0.007 (syst)
w = -1.023 +/- 0.090 (stat) +/- 0.054 (syst)
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