Physics Department, University of the Western Cape, Cape Town, South Africa; Institute of Theoretical Astrophysics, University of Oslo, PO Box 1029 Blindern, Oslo, Norway; SKA South Africa, The Park, Park Road, Cape Town, South Africa; CENTRA, Instituto Superior Técnico, Universidade de Lisboa, Lisboa, Portugal; Institute of Cosmology and Gravitation, University of Portsmouth, Portsmouth, United Kingdom; African Institute for Mathematical Sciences, Cape Town, South Africa; Department of Mathematics and Applied Mathematics, University of Cape Town, Cape Town, South Africa; South African Astronomical Observatory, Cape Town, South Africa
Yahya, S., Physics Department, University of the Western Cape, Cape Town, South Africa; Bull, P., Institute of Theoretical Astrophysics, University of Oslo, PO Box 1029 Blindern, Oslo, Norway; Santos, M.G., Physics Department, University of the Western Cape, Cape Town, South Africa, SKA South Africa, The Park, Park Road, Cape Town, South Africa, CENTRA, Instituto Superior Técnico, Universidade de Lisboa, Lisboa, Portugal; Silva, M., Physics Department, University of the Western Cape, Cape Town, South Africa, CENTRA, Instituto Superior Técnico, Universidade de Lisboa, Lisboa, Portugal; Maartens, R., Physics Department, University of the Western Cape, Cape Town, South Africa, Institute of Cosmology and Gravitation, University of Portsmouth, Portsmouth, United Kingdom; Okouma, P., Physics Department, University of the Western Cape, Cape Town, South Africa, African Institute for Mathematical Sciences, Cape Town, South Africa, Department of Mathematics and Applied Mathematics, University of Cape Town, Cape Town, South Africa; Bassett, B., African Institute for Mathematical Sciences, Cape Town, South Africa, Department of Mathematics and Applied Mathematics, University of Cape Town, Cape Town, South Africa, South African Astronomical Observatory, Cape Town, South Africa
The Square Kilometre Array (SKA) will conduct the biggest spectroscopic galaxy survey ever, by detecting the 21 cm emission line of neutral hydrogen (H I) from around a billion galaxies over 3/4 of the sky, out to a redshift of z ~ 2. This will allow the redshift-space matter power spectrum, and corresponding dark energy observables, to be measured with unprecedented precision. In this paper, we present an improved model of the HI galaxy number counts and bias from semi-analytic simulations, and use it to calculate the expected yield of HI galaxies from surveys with a variety of Phase 1 and 2 SKA configurations. We illustrate the relative performance of the different surveys by forecasting errors on the radial and transverse scales of the baryon acoustic oscillation (BAO) feature, finding that the full 'billion galaxy survey' with SKA2 will deliver the largest dark energy Figure of Merit of any current or future large-scale structure survey. © 2015 The Authors.