Colloquium on Sep. 17, 2020

Exploring the Power and Limits of Extracting Astrophysics from Interferometric Hi Intensity Mapping

Speaker:Zhaoting Chen (University of Manchester)

Venue:Video Conference

Time:15:00 PM, Thursday, Sep. 17, 2020

Abstract:

We confront the halo model of neutral hydrogen (Hi) tracer with large volume, high resolution simulations at redshift z∼0.1 and z∼1.0. Using a generic modelling of dark matter halos and Hi tracers, we report an accurate reconstruction of 21 cm brightness temperature power spectra, subject to modelling of non-linearity of halo clustering. Measurements of power spectra at small scales, combined with the halo model, break the degeneracy of Hi density, ΩHI, and Hi bias, bHI. For z∼0.1, we forecast that using MeerKAT and ASKAP, an accurate measurement of ΩHI up to 6% level accuracy and b0HI up to 1% level accuracy can be achieved. We propose a new way of associating Hi scatter in galaxies with Hi shot noise, which allows us to use the measurement of Hi shot noise to constrain the standard deviation of galaxy Hi mass. If the number density of Hi galaxies above a certain Hi mass threshold is given, additional analysis of shot noise predicts that future surveys can constrain the Hi Mass Function. With a standard Schechter function parameterisation, constraints at the 10% level can be obtained. It will potentially provide a new way of measuring the HiMass Function, independent to existing methods. We predict that future SKA will be able to further improve the constraints by a factor of three, and also opens the window for interferometric Intensity Mapping at z∼1. We make a case for the necessity of a deep continuum survey at z∼1 to allow accurate measurement, yielding constraints similar in magnitude to the z∼0.1 case and opening new redshiftwindows for Hi cosmology.

Report PPT:SWIFAR_Zhaoting Chen.pdf