Avoiding baryonic feedback effects on neutrino mass measurements from CMB lensing

Understand

A measurement of the sum of neutrino masses is one of the main applications of upcoming measurements of gravitational lensing of the cosmic microwave background (CMB).

• This measurement can be confounded by modelling uncertainties related to so-called "baryonic effects" on the clustering of matter, arising from gas dynamics, star formation, and feedback from active galactic nuclei and supernovae.
• In particular, a wrong assumption about the form of baryonic effects on CMB lensing can bias a neutrino mass measurement by a significant fraction of the statistical uncertainty.
• In this paper, we investigate three methods for mitigating this bias: (1) restricting the use of small-scale CMB lensing information when constraining neutrino mass; (2) using an external tracer to remove the low-redshift contribution to a CMB lensing map; and (3) marginalizing over a parametric model for baryonic effects on large-scale structure.