Abstract
We examine the importance of baryonic feedback effects on the matter power spectrum on small scales, and the implications for the precise measurement of neutrino masses through gravitational weak lensing. Planned large galaxy surveys such as the Large Synoptic Sky Telescope (LSST) and Euclid are expected to measure the sum of neutrino masses to extremely high precision, sufficient to detect non-zero neutrino masses even in the minimal mass normal hierarchy. We show that weak lensing of galaxies while being a very good probe of neutrino masses, is extremely sensitive to baryonic feedback processes. We use publicly available results from the Overwhelmingly Large Simulations (OWLS) project to investigate the effects of active galactic nuclei feedback, the nature of the stellar initial mass function, and gas cooling rates, on the measured weak lensing shear power spectrum. Using the Fisher matrix formalism and priors from CMB+BAO data, we show that when one does not account for feedback, the measured neutrino mass may be substantially larger or smaller than the true mass, depending on the dominant feedback mechanism, with the mass error |\Delta m_nu| often exceeding the mass m_nu itself. We also consider gravitational lensing of the cosmic microwave background (CMB) and show that it is not sensitive to baryonic feedback on scales l < 2000, although CMB experiments that aim for sensitivities sigma(m_nu) < 0.02 eV will need to include baryonic effects in modeling the CMB lensing potential. A combination of CMB lensing and galaxy lensing can help break the degeneracy between neutrino masses and baryonic feedback processes. We conclude that future large galaxy lensing surveys such as LSST and Euclid can only measure neutrino masses accurately if the matter power spectrum can be measured to similar accuracy.
Highlights
The discovery of neutrino masses provides exciting hints of physics beyond the standard model
We discussed how future weak lensing surveys, such as the Large Synoptic Sky Telescope (LSST) and Euclid, can measure neutrino masses through weak gravitational lensing of large scale structure
We showed that weak lensing is sensitive to the small-scale non-linear matter power spectrum and is a powerful tool with which to probe neutrino masses
Summary
The discovery of neutrino masses provides exciting hints of physics beyond the standard model. Large neutrino masses result in a damping of the small-scale matter power spectrum. They modify the size of the sound horizon at decoupling, and can be constrained through the location of the CMB peaks, and Baryonic Acoustic Oscillation (BAO) measurements. [18] estimate that combined CMB, shear, and galaxy data from future surveys can constrain neutrino masses with an estimated error on the sum of neutrino masses σ(mν) < 0.011(0.022) eV, assuming full knowledge (no knowledge) of the galaxy bias, which would be a >∼ 2.6σ detection even in the case of the minimal mass normal hierarchy Such highly precise measurements require a thorough understanding of the clustering properties of matter through high-resolution hydrodynamic simulations. It is noted that at low redshifts, massive halos of ∼ 1013M are almost devoid of gas as a result of radio-mode AGN feedback in disagreement with observations, suggesting that the precise nature of AGN feedback is a difficult issue to resolve
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
