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Status of the Supernova Legacy Survey (SNLS) Isobel Hook University of Oxford
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SNe Ia provide direct evidence for accelerating Universe Results inconsistent with M =1 spatially flat cosmology (SNe too faint) SN data favor >0
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Riess et al (1998) with 16 ACS-discovered SNe z<1.5 (Riess et al 2004) If universe is flat then data require > 0
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SN constraints on M ( =1) High-z Team Riess et al 1998: M =0.28 +/-0.1 Tonry et al 2003 M =0.28 +/- 0.05 Riess et al 2004 M =0.29 + 0.05–0.03 SCP Perlmutter et al 1999: M =0.28 +0.09 -0.08 + 0.05-0.04 Knop et al 2004 : M= 0.25 +0.07-0.06 +/-0.04 The rest made up by “dark energy”
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The nature of the dark energy Cosmological constant fits the data but… –Fine tuning problem? Other possibilities include quintessence Differentiate via the equation of state Distinguishing w=-0.8 and w=-1 at 3σ requires ≈700 SNeIa with 0.15<z<0.9 – which SNLS will provide
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w = –1.02 +0.13 – 0.19 Riess et al 2004 Current Constraints on w Assumptions: Flat Universe w constant in time 2dF: M h = 0.2 ± 0.03 KP: h = 0.72 ± 0.08 Knop et al 2003
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SNLS collaboration http://cfht.hawaii.edu/SNLS/ Chris Pritchet: U. Victoria Ray Carlberg: U. Toronto Andy Howell: U. Toronto Mark Sullivan: U. Toronto Arif Babul: U. Victoria David Balam: U. Victoria Sara Ellison: U. Victoria F.D.A. Hartwick: U. Victoria Henk Hoekstra: CITA Don Neill: U. Toronto Julio Navarro: U. Victoria Kathy Perrett: U. Toronto David Schade: HIA Pierre Astier : CNRS-IN2P3, Paris Eric Aubourg Christophe Balland Luc Simard: HIA Peter Stetson: HIA Sidney van den Bergh: HIA Jon Willis: U. Victoria Isobel Hook: U. Oxford Justin Bronder: U. Oxford Richard McMahon: U. Cambridge Reynald Pain: CNRS-IN2P3, Paris Saul Perlmutter:LBNL Robert Knop: U. Vanderbilt James Rich: CEA-Saclay Nic Walton: U. Cambridge Eric Smith: Vanderbilt University Greg Aldering: LBNL Lifan Wang: LBNL Rachel Gibbons: LBNL Vitaly Fadayev: LBNL Stephane Basa Sylvain Baumont Sebastien Fabbro Melanie Filliol Ariel Goobar: Stockholm Delphine Guide Julien Guy Delphine Hardin Nicolas Regnault Tony Spadafora: LBNL Max Scherzer: LBNL Harish Agarwal: LBNL Herve Lafoux Vincent Lebrun Martine Mouchet Ana Mourao Nathalie Palanques Gregory Sainton Canada, France, UK, US, Sweden, Portugal
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SNLS Goals Primary goal: Use SNe Ia to determine “w” –SNLS Goal: 1000 SNe Ia (across all redshifts) –Calibration goal: 1-2% photometric accuracy SNLS advantages: –Rolling search –Queue observing –Multi-colour lightcurves –Spectroscopic follow up SNLS provides many consistency checks –SN colour evolution – multi-colour photometry check –Detailed studies of spectral evolution (Gemini/VLT/Keck spectra) [Bronder et al.]
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MegaCam 36 CCD imager MegaCam 1 deg x 1 deg 1 deg x 1 deg CFHT-LS (DEEP) 4 Fields 202 queue nights over 5 yrs Started August 03 5 epochs per field/month (u),g’r’i’z’ Top priority : 1 hr in i’ every 2-3 nights i~24.9 AB with S/N=10 CFHT imaging
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SNLS Rolling Search Real-time lightcurves
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SNLS spectroscopy Gemini N and S –2003B to 2005B: 60 hrs /semester –PI: I. Hook VLT –240 hrs periods 71-74 –Continuation requested P75-78 –PI: R. Pain Goal : measure redshifts and Types for SNLS candidates Fainter targets with Gemini, others at VLT Supplemented with spectra from Keck & Magellan
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Example Gemini/GMOS Nod & Shuffle spectrum 2 hr exposure SN i=24.0 Wavelength
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Host Galaxy spectrum
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Smoothed spectrum allowing for: template host galaxy subtraction Reddening Extracted spectrum Best match template SN SiII
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To Jun 2005: 191 SNIa/Ia? = 0.60 All close to maximum light (within ~10 days) Spectroscopic Summary to date 1 st yr Gemini spectra: Howell et al (2005) VLT spectra: Basa et al (2005)
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First Year Results – Hubble Diagram (Astier et al. in prep) First year results (72 SNeIa) consistent with an accelerating Universe: Ω Λ ~0.7 in a flat universe
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Comparison with previous SN results Comparison of SNLS first year (72 SNe) to previous SN results – Knop et al 2003 (~50 SNe) Shaded area shows projected end-of-survey constraints Superior colour and time sampling of SNLS allows tighter constraints on the cosmological parameters than any previous SN sample.
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SNLS Preliminary constraints on w (Astier et al in prep.)
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Preliminary results and predictions for end of survey w constraints with no prior on M Assumes flat universe With prior on M (e.g. from CFHT-LS weak lensing) should measure w to +/- 0.07 (stat)
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Conclusions Measurements of m and z of Type Ia SNe provide direct measurement of the acceleration of the Universe Can measure M, w during the epoch of dark energy Independent and complementary technique to CMB and galaxy redshift surveys SNLS will constrain w to ~ +/-0.07, & hence the nature of the dark energy SNLS will be the definitive high-z SN data set for ~10 years
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More Information See these websites for all details: Project overview, collaboration members, publications: –http://cfht.hawaii.edu/SNLS/ Candidate database, real-time candidate lists: –http://legacy.astro.utoronto.ca/ Watch out for the first SNLS cosmology publication soon!
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The End
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