Poster abstract details

Studying Luminous Red Galaxies to probe H(z) at high redshift
Ando Ratsimbazafy


Luminous Red Galaxies (LRGs) have old, red stellar populations often interpreted as evidence of a formation scenario in which these galaxies form in a single intense burst of star formation at high redshift. By measuring the average age of LRGs at two different redshifts, one can potentially measure the redshift interval corresponding to a time interval and thus measure the Hubble parameter H(z)= -(1+z)-1 Δz/Δt (as in Jimenez & Loeb).
The goal of this project is to measure directly the expansion rate of the universe at the redshift range 0.1 < z < 1.0 within 3% precision. We explore the age-dating of Sloan Digital Sky Survey (SDSS) LRGs using two different methods of fitting: the use of the stellar population models of Lick absorption line indices and the full spectral fitting. The fitting process is proceeded after stacking spectra in redshift bins to increase the signal-to-noise. We also apply the full spectral fitting method to measure the ages of LRGs observed with the Southern Africa Large Telescope (SALT). The results of H(z) estimates using the two different datasets will be presented as well as the cosmological constraints.