Astrophysics Seminar: SZ Number Counts and Power Spectrum: Neutrino Mass Constraints and Bias of Cosmological Parameters

Abstract:

Compton scattering of the CMB in galaxy clusters can be a sensitive probe of neutrino masses in the sub-eV range, but it can also introduce an appreciable bias in the extraction of some cosmological parameters. In the first part of the talk I will discuss the possibility of using cluster number counts from the ongoing PLANCK/SZ and future cosmic-variance-limited surveys to constrain neutrino masses solely from CMB data. Our recent work indicates that the projected precision in the determination of the total neutrino mass from the PLANCK/SZ survey is 0.06 eV (68 %), a constraint that is 2-3 times tighter than that expected from CMB lensing. For a cosmic-variance-limited (CVL) SZ survey we predict an uncertainty of 0.04 eV, a level comparable to that expected when CMB lensing extraction is carried out with the same experiment. These results were obtained under the asumption that the cluster mass function (MF) is pricesly known; a few percent uncertainty in the MF parameters could result in up to a factor 2-3 degradation of the PLANCK and CVL forecasts. These results demonstrate that cluster number counts provide a viable complementary probe to CMB lensing constraints on the total neutrino mass, and highlight the importance of improved knowledge of the cluster MF.

In the second part of the talk I will describe our recent work on the impact of filmant-induced SZ signal on the microwave sky and the expected bias it introduces in inferred cosmological parameters. We detemine the filament power spectrum based on a simple morphological model for filaments and adopting a MF deduced from simulations. The calculated filament power spectrum is sufficiently substantial to introduce nonnegligible bias in several key cosmological parameters extracted from primary CMB power spectra deduced from PLANCK data (and to a larger extent from a CVL survey).

Seminar Organiser: Prof. Rennan Barkana