Abstract Details
| Name: Debanjan Sarkar Affiliation: Indian Institute of Technology Kharagpur Conference ID: ASI2018_1638 Title : Modelling redshift-space distortion (RSD) in the post-reionization HI 21-cm power spectrum Authors and Co-Authors : Somnath Bharadwaj(Indian Institute of Technology Kharagpur) Abstract Type : Contributed Talk Abstract Category : General Relativity and Cosmology Abstract : The post-reionization HI 21-cm signal, which is expected to be a pristine probe of the large scale structures in the Universe, is an excellent candidate for precision cosmology. This requires accurate and reliable modelling of the expected signal. In an earlier work (Sarkar, Bharadwaj \& Anathpindika; 2016) we have simulated the expected HI 21-cm power spectrum $P_{{\rm HI}}(k)$ in real space (as against redshift space) and used this to model the $k$ dependence of the (possibly complex) bias $\tilde{b}(k)$ over the redshift range $1 \le z \le 6$. Here we have extended the earlier simulations to include the redshift space distortion (RSD) due to the peculiar motion of the HI, and we have used this to model the anisotropy of the redshift space HI 21-cm power spectrum $P^s_{{\rm HI}}(k_{\perp},k_{\parallel})$. We model $P^s_{{\rm HI}}(k_{\perp},k_{\parallel})$ assuming that it is the product of $P_{{\rm HI}}(k)=b^2 P(k)$ with a Kaiser enhancement term and a Finger of God (FoG) damping which has $\sigma_p$ the pair velocity dispersion as a free parameter. Considering several possibilities for the bias and the damping profile, we find that the models with a scale dependent bias and a Lorentzian damping profile best fit the simulated $P^s_{{\rm HI}}(k_{\perp},k_{\parallel})$ over the entire range $1 \le z \le 6$. The best fit value of $\sigma_p$ falls approximately as $(1+z)^{-2}$, and the FoG effect is absent at $z \ge 5$. The model predictions are consistent with the simulations for $k < 0.3 \, {\rm Mpc}^{-1}$ over the entire $z$ range for the monopole $P^s_0(k)$, and at $z \le 3$ for the quadrupole $P^s_2(k)$. At $z \ge 4$ the models underpredict $P^s_2(k)$ at large $k$, and the fit is restricted to $k < 0.15 \, {\rm Mpc}^{-1}$. |