Galaxy evolution, cosmology and dark energy with the Square Kilometer Array

Abstract

The present-day Universe is seemingly dominated by dark energy and dark matter, but mapping the normal (baryonic) content remains vital for both astrophysics -understanding how galaxies form -and astro-particle physics -inferring properties of the dark components.The Square Kilometre Array (SKA) will provide the only means of studying the cosmic evolution of neutral Hydrogen (HI) which, alongside information on star formation from the radio continuum, is needed to understand how stars formed from gas within dark-matter over-densities and the rôles of gas accretion and galaxy merging.'All hemisphere' HI redshift surveys to z ∼ 1.5 are feasible with wide-field-of-view realizations of the SKA and, by measuring the galaxy power spectrum in exquisite detail, will allow the first precise studies of the equationof-state of dark energy. The SKA will be capable of other uniquely powerful cosmological studies including the measurement of the dark-matter power spectrum using weak gravitational lensing, and the precise measurement of H0 using extragalactic water masers.The SKA is likely to become the premier dark-energy-measuring machine, bringing breakthroughs in cosmology beyond those likely to be made possible by combining CMB (e.g. Planck), optical (e.g. LSST, SNAP) and other early-21 st -century datasets.

Features and new physical scales in primordial observables: Theory and observation

“…At higher redshifts non-linear evolution becomes less of an issue, though in the case of the CMB, the original signal is significantly suppressed by Silk-damping from photon diffusion [314] and tends to be swamped by foregrounds beyond k O(10 −1 ) Mpc −1 . For other probes of the (matter) power spectrum such as 21 cm tomography, it may in principle be possible to see linearly coupled modes out to k ≈ O(10 2 ) Mpc −1 [24][25][26][27]. Therefore, given presently available data and being generous, the observable window spans a good four orders of magnitude in k, corresponding to roughly 10 e-foldings of inflation; features produced outside this range are hidden from our direct view.…”

“…It thus remains a pertinent question to ask whether or not we have exhausted all the information content that is potentially available in the primordial two-point correlation functions. Even if primordial non-Gaussianity is ever detected, the question takes on added significance in light of the vast amount of data due to become available in the near to long term through large-scale structure [21][22][23], 21 cm observations [24][25][26][27] and observations of the spectral distortion of the CMB [28,29]. In partici Although interesting deviations from its predictions might be present at longer wavelengths with marginal significance [5].…”

Reionization and Cosmology with 21-cm Fluctuations

“…It has been recognized for some time that the Square Kilometer Array (SKA) could perform a billion galaxy spectroscopic redshift survey in HI (Rawlings et al 2004), and that such a survey could have very low systematic errors for cosmology (see the report of the Dark Energy Task Force 6 ). The proposed SKA BAO dark energy measurement would identify the three dimensional positions of bright galaxies ( L * ), and use them as tracers of the underlying density fluctuations.…”

The renormalization of the energy-momentum tensor for an effective initial state

“…Since inflation naturally produces a set of primordial perturbations through the inherent quantum fluctuations of a field, it is important to determine, from a very general perspective, the observability of the features at short distances compared with 1=H through their imprint on this primordial spectrum. While this imprint is not expected to be observed in the most recent experiments [18], future observations of the microwave background [28] and of the large scale structure over large volumes of the observed universe [29] should be able to extract the spectrum of primordial perturbations to a far better precision.…”