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Age-dating luminous red galaxies observed with the Southern African Large Telescope

A. L. RatsimbazafyCentre for Space Research, North-West University, Potchefstroom 2520, South AfricaS. I. LoubserCentre for Space Research, North-West University, Potchefstroom 2520, South AfricaSteven M. CrawfordSouth African Astronomical Observatory, PO Box 9 Observatory 7935, Cape Town, South AfricaC. M. CressPhysics Department, University of the Western Cape, Private Bag X17 Cape Town 7535, South AfricaBruce A. BassettDepartment of Maths and Applied Maths, University of Cape Town, Rondebosch 7701, South AfricaR. C. NicholInstitute of Cosmology and Gravitation, Dennis Sciama Building, Burnaby road, Portsmouth PO1 3FX, UKP. VäisänenSouth African Astronomical Observatory, PO Box 9 Observatory 7935, Cape Town, South Africa

2017en

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ABI

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We measure a value for the cosmic expansion of H(z) = 89 ± 23(stat) ± 44(syst) km s−1 Mpc−1 at a redshift of z ≃ 0.47 based on the differential age technique. This technique, also known as cosmic chronometers, uses the age difference between two redshifts for a passively evolving population of galaxies to calculate the expansion rate of the Universe. Our measurement is based on the analysis of high-quality spectra of luminous red galaxies obtained with the Southern African Large Telescope in two narrow redshift ranges of z ≃ 0.40 and 0.55 as part of an initial pilot study. Ages were estimated by fitting single stellar population models to the observed spectra. This measurement presents one of the best estimates of H(z) via this method at z ∼ 0.5 to date

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DOI: 10.1093/mnras/stx301

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