Dark energy constraints from the 21~cm intensity mapping surveys with SKA1

Abstract

Understanding the nature of dark energy is one of the most outstanding problems in cosmology at present. In last twenty years, cosmological observations related to SNIa, Cosmic Microwave Background Radiation, Baryon Acoustic Oscillations etc, have put stringent constraints on the the dark energy evolution, still there is enough uncertainty in our knowledge about dark energy that demands new generation of cosmological observations. Post-reionization neutral hydrogen 21 cm intensity mapping surveys are one of the most promising future cosmological observations that have the potential to map the cosmological evolution from dark ages till present time with unprecedented accuracy and Square Kilometer Array (SKA) is one of the most sensitive instruments to measure the post-reionization 21 cm signal. In this work, we study the future dark energy constraints using postreionization 21 cm intensity mapping power spectra with SKA1-mid specifications. We use three different parametrizations for dark energy equation of state (EoS) including the widely used CPL one. To generate simulated data, we use to two fiducial models: the concordance ΛCDM and the best fit CPL model for Planck+SNIa+BAO+HST. Our study shows that SKA1-mid alone has the potential to reach the present accuracy for combined Planck+SNIa+BAO+HST to constrain the dark energy behaviour. Whether dark energy is phantom or non-phantom or whether it exhibits phantom crossing, we may potentially address such questions with SKA1-mid. We also show that it is crucial to choose the correct parametrization for dark energy equation of state as some parametrizations are better than others to constrain the dark energy behaviour. Specifically, as observed in this study, the widely used CPL parametrization may not give the best constraint for dark energy behaviour.

Mapping large-scale-structure evolution over cosmic times

“…For example, it has been shown that LIM can potentially improve the experimental sensitivity to radiative dark-matter decays or annihilation by up to ten orders of magnitude [29], using cross-correlation of the spectral intensity maps with external traces of the mass distribution (such as CMB lensing). Meanwhile, the BAO measurements described above can probe models with a time-dependent equation of state for dark energy [37] or modified gravity theories [45,50,81].…”

Astrophysics and Cosmology with Line-Intensity Mapping

“…Dark energy and modified gravity. LIM measurements of baryon acoustic oscillations can be made continuously from low to high redshifts, enabling a test of the time-variation of the dark-energy equation of state [28]. In particular, LIM will shed light on the growing tension between local and CMB measurements of the Hubble parameter [29] by bridging the enormous distance gap between their sources.…”

Astrophysics & Cosmology from Line Intensity Mapping vs Galaxy Surveys

“…Tracking the evolution of galaxy populations from early times to today contains a wealth of astrophysical information about galaxy formation and evolution [2][3][4], and the processes which reionized the Universe [5][6][7]. It spans a large fraction of the observable Universe, enabling high precision measurements of the evolution of structure in the Universe, testing the properties of ΛCDM [8,9] and the masses of the neutrinos. Because the matter distribution is more linear at higher redshift, its simpler and more accurate modeling should also allow us to better reconstruct the initial conditions of the Universe, and test the presence of primordial non-Gaussianities [10][11][12].…”