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

Published online by Cambridge University Press:  17 July 2013

A. Ratsimbazafy ,
C. Cress ,
S. Crawford  and
SCALPEL team
A. Ratsimbazafy
Affiliation:
Physics Dept, University of the Western Cape, Private Bag X17. Cape Town 7535, South Africa email: raljha.a@gmail.com
C. Cress
Affiliation:
Physics Dept, University of the Western Cape, Private Bag X17. Cape Town 7535, South Africa email: raljha.a@gmail.com Centre of High Performance Computing, 15 Lower Hope St. Cape Town 7700, South Africa
S. Crawford
Affiliation:
South African Astronomical Observatory, PO box 9. Cape Town 7935, South Africa
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Abstract

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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 Δ z/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 LRGs using the stellar population models of Lick absorption line indices after stacking spectra in redshift bins to increase the signal-to-noise. We also use the method of full spectral fitting to measure the ages of LRGs observed with the Southern Africa Large Telescope (SALT).

Keywords

galaxies: evolutioncosmology: cosmological parameterscosmology: observations

References

Crawford, S., Ratsimbazafy, A., Cress, C., et al. 2010, MNRAS, 406, 2569Google Scholar
Jimenez, & Loeb, 2002, ApJ, 573, 37CrossRefGoogle Scholar