Chandra Shekhar Murmu
Indian Institute of Technology Indore
Impact of Light-cone on the EoR CII LIM signal statistics
Probing the Epoch of Reionization (EoR) is one of the untackled challenges in modern cosmology. Line Intensity Mapping (LIM) of early galaxies from the EoR regime has the potential of being a reliable complementary probe of EoR to the 21 cm surveys. The CII line emission is a robust tracer of such galaxies, and upcoming LIM experiments like CONCERTO, CCAT-p, TIME-pilot will do large-volume surveys by detecting the CII signal fluctuations from EoR across the sky. It will enable us to estimate the CII power-spectrum and CII-21cm cross-power spectrum, and that way, we can understand and learn about the EoR. Since any observed signal will inherently have varying statistical properties along the Line of Sight (LoS), we have tried to model this so-called light-cone effect on the observed statistics of our semi-numerical CII simulations and quantify its impact. We find that light-cone can impact the CII power spectrum by more than 15% at relevant k-modes (k~0.1 Mpc^-1). Likewise, the CII-21cm cross-power spectrum is affected by light-cone, and in our models where reionization ends before z=6, we find that the impact on cross-power can reach 15-20% (at k~0.1 Mpc^-1). A comparatively faster reionization history leads to a more drastic influence on the cross-power due to light-cone. We can use the CII-21cm cross-power to constrain the reionization history and EoR parameters; we conclude that to do so, one needs to take the light-cone effect into account.