ASIAANTUPHYS CosPA Seminar May 28, Supernovae and Acceleration of the Universe A journal club K. Y. Lo

ASIAANTUPHYS CosPA Seminar May 28, Papers reviewed: 1. Supernova explosions in the Universe –Adam Burrows, 2000, Nature, 403, Observational Evidence from Supernovae for an Accelerating Universe and a Cosmological Constant –Reiss et al, 1998, AJ, 116, Measurements of  and  from 42 High Redshift Supernovae – Perlmutter et al, 1999, ApJ, 517, 565

ASIAANTUPHYS CosPA Seminar May 28, Geometry and Dynamics of the Universe Robertson-Walker metric: d  2 = dt 2 – a(t) 2 [dr 2 /(1 – r 2 /R 2 ) + r 2( d  2 + sin 2  d  2 )] –Scale factor, a(t) and radius of curvature, R History and Fate of the Universe: a(t) = ? ä/a = – 4  G(3p +  )/3 +  /3 = H o 2 [   –  m (1+z) 3 /2], (å/a) 2 = 8  G  /3 – 1/R 2 a 2 +  /3 = H o 2 [   +  m (1+z) 3 +  R (1+z) 2 ] Accelerating Universe: ä > 0  [   –  m (1+z) 3 /2] > 0 Taylor-expansion of a(t) at t o, the present: a(t) = a(t o )[1 + H o (t – t o ) – ½q o H o 2 (t - t o ) 2 + …] H o = å(t o )/a(t o ), q o = – ä (t o )/[H o 2 a(t o )], a(t o )/a(t) = 1 + z

ASIAANTUPHYS CosPA Seminar May 28, Hubble diagram of Standard Candles at various z: F = L/4  d L 2 = L/4  (a o r z ) 2 (1+z) 2 –F = Observed flux (erg/s/cm 2, or apparent magnitude) –L = Intrinsic luminosity (erg/s, or absolute magnitude) –d L = Luminosity distance = f(z,  ,  m ) = f’(z, q o, H o ) = H o -1 |  k | -½ sinn{|  k | ½  z [(1+z) 2 (1+  m z) – z(2+z)   ] -½ dz} = H o -1 z [1 + (q o – 1)z + …] -½, z < 1 –If  =   +  m only, q o =  m /2 –   Hubble Diagram: Apparent magnitude vs z plot m = M + 5 log[H o d L (z,  ,  m )] – 5 log H o + 25 Need Standard Candles at large z (~1) !! How to measure q o ?

ASIAANTUPHYS CosPA Seminar May 28, Standard Candles at large z Bright: to be detectable –~25 mag detection limit; absolute magnitude ~ -20 mag Intrinsic luminosity known First ranked galaxies in distant clusters (cf. Sandage 1988) –Evolution of galaxies –Scott effect/Mahmquist bias –Extinction, k-correction, aperture,... Type I SNe (SCP, HSS projects) – Searches for high z SNe –Calibrate Intrinsic luminosity with nearby sample: Luminosity - light-curve shape correlation: empirical standards

ASIAANTUPHYS CosPA Seminar May 28,

ASIAANTUPHYS CosPA Seminar May 28, Supernovae (cf Viewgraphs) Type II (no H in spectra) –Core collapse: > 11 M(solar) stars, burn through to Fe, succumb to gravity, collapse to neutron star, blows off mantle Type I (H in spectra) –Thermonuclear Incineration: Binary system with a white dwarf; mass transfer pushes WD to above Chandrasekhar limit; C,N,O burns explosively –10  less frequent; 10  brighter at peak; 10  more Fe produced –Energy release ~ burning 1.4M(solar) of C to Fe ~ standard candle ? 1 SN every second in the Universe –Galaxy: 1 SN every 30 to 50 years; one Type Ia every 300 years –SN search: ~ 10 SNe per night

ASIAANTUPHYS CosPA Seminar May 28,

ASIAANTUPHYS CosPA Seminar May 28,

ASIAANTUPHYS CosPA Seminar May 28,

ASIAANTUPHYS CosPA Seminar May 28,

ASIAANTUPHYS CosPA Seminar May 28, Perlmutter et al 1999 ApJ, 483, 565

ASIAANTUPHYS CosPA Seminar May 28,

ASIAANTUPHYS CosPA Seminar May 28,

ASIAANTUPHYS CosPA Seminar May 28,

ASIAANTUPHYS CosPA Seminar May 28,

ASIAANTUPHYS CosPA Seminar May 28,

ASIAANTUPHYS CosPA Seminar May 28,

ASIAANTUPHYS CosPA Seminar May 28, Perlmutter et al 1999 ApJ, 483, 565 Supernova Cosmology Project (>1988): LBL, Berkeley, Cambridge, Spain, Australia, STScI, Fermi Lab 42 SNe: 0.18 < z < Calan/Tololo nearby SNe: z < 0.1 –L fixed by light-curve width-luminosity correlation Hubble diagram fit by various models of d L –Inconsistent with =0, flat cosmology –0.8  m – 0.6   = 0.2 ± 0.1 –If  =1,   ~ 0.7 ± 0.1,  m ~ 0.3 ± 0.1 – t o ~ 14.9 ± 1.3 (0.63/h) Gyr

ASIAANTUPHYS CosPA Seminar May 28, Reiss et al 1998 AJ, 116, 1009 High z SN Search: Berkeley, Harvard, Chile, STScI, U. Wash, Mt. Stromlo, Michigan –CTIO 4m CCD; spectroscopy with Keck, MMT – high-z SNe: 0.16 < z < 0.97 –34 nearby SNe Hubble diagram constrains H o, q o, t o,  ,  m –   > 0 and q o < 0 at 3  confidence level –If  = 1,   > 0 at 7  –  m ruled out at 7  level –t o = 14.9 ± 1.7 Gyr

ASIAANTUPHYS CosPA Seminar May 28,

ASIAANTUPHYS CosPA Seminar May 28,

ASIAANTUPHYS CosPA Seminar May 28,

ASIAANTUPHYS CosPA Seminar May 28,

ASIAANTUPHYS CosPA Seminar May 28,

ASIAANTUPHYS CosPA Seminar May 28,

ASIAANTUPHYS CosPA Seminar May 28, Uncertainties & the Future Intrinsic luminosity/Evolution of SNe Type Ia K-correction: emitted wavelength red-shifted by (1+z) Extinction (intrinsic and Galactic) Selection bias (Scott-Mahmquist) Local Void (in-homogeneity) Gravitational lensing (affects apparent magnitude) Contamination by non-Type Ia SN  SNe at z > 1; SN light red-shifted to IR: NGST etc

ASIAANTUPHYS CosPA Seminar May 28, SN at z = 1.7 Reiss et al, April 2001 HST: Brighter than expected for steady state expansion: deceleration !?

ASIAANTUPHYS CosPA Seminar May 28,

ASIAANTUPHYS CosPA Seminar May 28,

ASIAANTUPHYS CosPA Seminar May 28, Conclusion More observations needed ! More observations will come ! Theorists can go on theorizing, but there will be a day of reckoning, which is what makes physics real and fun !