1Relationship between ϖand redshift zIn principleIn practice(because of that @#$% cosmological constant)Eqns. 29.180, 29.181, true for all models• R-W metric:• Friedmann Eqn: Proper Distancedp,o~Luminosity DistanceF = L4πd2In practice(because of that @#$% cosmological constant)About right…Redshift Î (1+z)Time dilation Î (1+z)2Old Redshift-Magnitude Results• Curves diverge at larger z• Î use very luminous objects which are observable at large z.• Best bet = brightest cluster galaxies• But big correction for evolution of stellar population.Assuming Λ = 0Brightest cluster galaxiesAssuming Λ = 0qo– the accelerating universe• Type Ia supernovae are best standard candles.• Least scatter in luminosity• 2 independent groups get same answer• Supernova Cosmology Project• Perlmutter et al. 1999 ApJ 517, 565• High-z Supernova Search• Garnavich et al. ApJ 509, 74• Found acceleration• Not deceleration as expected.[CO fig. 29.27]Supernova resultsSupernova resultsBrightest clustergalaxiesqo= 0 1 2
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