Special Seminar: Unlocking the promise of high redshift 21cm: Very First stars, better cosmology, and context for JWST

Friday, February 17, 2017 - 1:00pm
216 Pyhsics
Daniel Jacobs (Arizona State University)


        The science case for observations of 21cm during and before reionization (6>z>12) begins with the properties of galaxies driving reionization however measurements of the time history of the power spectrum offer several additional possibilities unique to this probe. In this talk we’ll examine three.  First the power spectrum at the highest redshifts observed is predicted to have a bright signature driven by heating in the pre-reionization universe (z>11). This heat can come from XRay binaries formed from the collapsed remnants of Population III stars or it could even come from annihilating dark matter all of which have different 21cm power spectrum signatures.  Second, an open problem in cosmology is the timing of reionization and the value of tau, the optical depth to the CMB. This parameter is degenerate with cosmological parameters and its uncertainty is a limiting factor to present and future CMB measurements. With the 21cm probe of reionization we are directly measuring the onset of reionization and can break this degeneracy to improve several parameters including the sum of the neutrino masses. Finally, we’ll explore the future possibilities for cross correlation of high redshift galaxy observations by JWST and others with 21cm maps tracing neutral hydrogen and ionized regions as a function of redshift.