Cosmological performance of SKA H i galaxy surveys

Abstract

The Square Kilometre Array (SKA) will conduct the biggest spectroscopic galaxy survey ever, by detecting the 21cm emission line of neutral hydrogen (HI) 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.

Probing the constancy of the speed of light with future galaxy survey: The case of SKA and Euclid

“…Thus this level of improvement we have considered should be possible. Moreover, it is also clear that any technical improvement will be useful: based on modern technology, the ground based telescopes like DESI and SKA [44] are already almost as competitive as space ones like Euclid and WFIRST-2.4, with SKA errors that should be one third of Euclid ones. Thus we expect that in the future, even if still not planned, it will be surely possible to further improve space-based surveys and obtain even better constraints.…”

“…In [44] the percentage errors on D A and H expected from this survey are shown in their Fig. 5; we can use them, once given the fiducial values for these quantities, to calculate their corresponding errors.…”

SKA weak lensing – I. Cosmological forecasts and the power of radio-optical cross-correlations

“…Yahya et al 2015), greatly improving the tomographic reconstruction for the sources for which spectra are available. For SKA1 this will be a relatively small fraction of sources (∼ 10%) at low redshifts (which are less useful for gravitational lensing) but this will improve significantly for SKA2.…”

Large-scale imprint of relativistic effects in the cosmic magnification

“…1 and 2) that there is a consistent decrease in the amplitude of C with increasing z; with the contribution of the GR effects (relative to the weak lensing effect) gradually falling, to ∼40% at z S = 3 (see inset), which is a significant amount nevertheless, as we enter an era of precision cosmology-e.g. BOSS is expected to measure the area distanceD A with a precision of ∼1.0% at z < 0.7 and ∼4.5% at z ≈ 2.5 (with higher % at 2 z 3.5) [63], while the SKA is expected to be better (∼0.3% at z ≈ 1.3) [61]. (Note however that, in reality, detecting the actual effect of the GR corrections depends on the cosmic variance on the given scales, and the error bars achievable by the survey experiment; but for the purpose of this work, we leave out all exact experimental aspects.)…”

“…The cosmic magnification [1]- [59] will be crucial in interpreting the data from future surveys that depend on the apparent flux and/or angular size of the sources, such as surveys of the 21 cm emission line of neutral hydrogen of the SKA [60,61], and the baryon acoustic oscillation surveys of BOSS [62,63]. It will be key to understanding cosmic distances, and the nature of large-scale structure in the universe.…”