Wednesday.
1511.07377
Combining galaxy and 21cm surveys
Cohn, White, Chang, Holder, Padmanabhan, Doré
Acoustic waves traveling through the early Universe imprint a characteristic scale in the clustering of galaxies, QSOs and inter-galactic gas. This scale can be used as a standard ruler to map the expansion history of the Universe, a technique known as BAO. BAO offer a high-precision, low-systematics means of constraining the cosmo model. The statistical power of BAO measurements can be improved if the 'smearing' of the acoustic feature by non-linear structure formation is undone in a process known as reconstruction. In this paper, use low-order Lagrangian perturbation theory to study the ability of 21 cm experiments to perform reconstruction and how augmenting these surveys with galaxy redshift surveys at relatively low number densities can improve performance. Find that the critical number density which must be achieved in order to benefit 21 cm surveys is set by the linear theory power spectrum near its peak, and corresponds to densities achievable by upcoming surveys of emission line galaxies such as eBOSS and DESI. As part of this work, analyze reconstruction within the framework of Lagrangian perturbation theory with local Lagrangian bias, redshift-space distortions, k-dependent noise and anisotropic filtering schemes.
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