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تسجيل مستخدم جديدSeparating out the Alcock-Paczynski Effect on 21cm Fluctuations
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Rennan Barkana
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We reconsider the Alcock-Paczynski effect on 21cm fluctuations from high redshift, focusing on the 21cm power spectrum. We show that at each accessible redshift both the angular diameter distance and the Hubble constant can be determined from the power spectrum. Furthermore, this is possible using anisotropies that depend only on linear density perturbations and not on astrophysical sources of 21cm fluctuations. We show that measuring these quantities at high redshift would not just confirm results from the cosmic microwave background but provide appreciable additional sensitivity to cosmological parameters and dark energy.
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Feasibility of the Alcock Paczynski (AP) test by stacking voids in the 21cm line intensity field is presented. We analyze the Illstris-TNG simulation to obtain the 21cm signal map. We then randomly distribute particles depending on the 21cm intensity
field to find voids by using publicly available code, VIDE. As in the galaxy clustering, the shape of the stacked void in the 21cm field is squashed along the line of sight due to the peculiar velocities in redshift-space, although it becomes spherical in real-space. The redshift-space distortion for the stacked void weakly depends on redshift and we show that the dependency can be well described by the linear prediction, with the amplitude of the offset being free parameters. We find that the AP test using the stacked voids in a 21cm intensity map is feasible and the parameter estimation on $Omega_{rm m}$ and $w$ is unbiased.
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