From Supernovae to Baryon Acoustic Oscillations Patrice OKOUMA Supervisor : Prof. Bruce A. BASSETT UCT Dec. 2008SKA Postgraduate Bursary Conference

Overview Theoretical Work Observational WorkData Analysis Adiabatic & Isocurvature modes on BAO Type-Ia Supernovae MeerKAT /SKA SALT

A Type-Ia Supernovae (SNe Ia) > Explosion of a White Dwarf having accreted mass from a companion star, beyond a critical threshold known as the Chandrasekhar limit (~ 1.4 Solar masses). A reminder Silicon Line Folatelli (2004)‏

SNe Ia as standardizable candle Krisciunas et al., 2005

Spectral characterization of Type-Ia supernovae via chi-squared based techniques and cross- correlation approach (SNID by Blondin et al. 2006) > M.Sc. A past work

chi-squared approach cross-correlation approach (SNID code)‏

2-week campaign for Infra red light curves of Sne Ia ( IRSF, Sutherland, SA )‏ Work with Ariel Goobar & al. (Sweden)‏ Extinctions corrections for optical observations -----> Major uncertainty in using SNe Ia for cosmology

In NIR, SNe-Ia are still standardizable candles ( Krisciunas et al., 2005 )‏ Smaller extinction corrections Strong evidence for a weaker lightcurve width-brightness correction Lower error budget Better constraints on the Cosmology

2-week campaign for optical spectra of Sne ( 1.9-m telescope, Sutherland, SA )‏ Work with. Y. Fang & al. (Michigan,US); A. Goobar et al. (Sweden)‏ Goals : Training; Testing simultaneous identification of transients from ROTSE ( in Gamsberg (southern Namibia).

Theoretical Work Observational WorkData Analysis Adiabatic & Isocurvature modes on BAO Supernovae MeerKAT / SKA SALT

Number density and/or energy density characterize cosmological species in the early Universe. Linear perturbations of these quantities are The Early Universe through Baryon Acoustic Oscillations Work with K. Moodley et al. (UKZN,SA) & C. Zunckel (Princeton, US)‏ METRIC perturbationsEqs. for evolution of perturbations THEN

Adiabatic modes are perturbations affecting cosmological species such that : Isocurvature modes : CMB (for flat Universe) ===> Adiabatic modes are dominant BUT BUT ~ 10% Isocurvature modes are allowed (in early Universe). S. White (2008)‏

Therefore, If we assume Adiabatic fluctuations, what do we get wrong about Dark Energy... and... by how much ? Baryon Acoustic Oscillations (B.A.O) = Pathfinder Initial fluctuations in density and gravitational potential drive acoustic waves in the fluid: compressions and rarefactions. At early times the universe was hot, dense and ionized. Photons and matter were tightly coupled by Thomson scattering.

An (adiab.) evolution in a spherically symmetric shell of plasma ‏

Another prediction verified !!! Eisenstein et al. (2005)‏ detect the theorized “bump” in the 2-point correlation function of the SDSS -LRG at z ~ 0.35

From CMB Possible effects of Isocurvature modes r0

Theory/Model Control with data Feedback Simulation (classical) Program √

Simulations using CAMB (code )‏ Mixture Cross-correlation Pk Correlation coeff. = -1 : anti-correlation = 1 : full correlation else : partial correlation

Divide both

Totally correlated

Partially correlated

Zoom

Strong “degeneracy” with Dark Energy via BAO Immediate perspective

Perspective (cont'd)‏ : Fisher formalism on Pk Seo & Eisenstein (2007) approach <--

Future work & preliminary conclusion BAO are a rapidly maturing method for investigating Dark Energy -----> Huge collaboration opportunities. Highly robust method. Complimentary to Supernova cosmology Applicability and scalability to MeerKAT / SKA … MeerKat TBD ~ 1 Million Ongoing F. Combes (2006)‏

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