Cosmic voids , the underdense regions in the universe , are particularly sensitive to diffuse density components such as cosmic neutrinos .
This sensitivity is enhanced by the match between void sizes and the free-streaming scale of massive neutrinos .
Using the massive neutrino simulations MassiveNuS , we investigate the effect of neutrino mass on dark matter halos as a function of environment .
We find that the halo mass function depends strongly on neutrino mass and that this dependence is more pronounced in voids than in high-density environments .
An observational program that measured the characteristic mass of the most massive halos in voids should be able to place novel constraints on the sum of the masses of neutrinos \sum m _ { \nu } .
The neutrino mass effect in the simulations is quite strong : In a 512 ^ { 3 } h ^ { -3 } Mpc ^ { 3 } survey , the mean mass of the 1000 most massive halos in the void interiors is ( 4.82 \pm 0.11 ) \times 10 ^ { 12 } ~ { } h ^ { -1 } M _ { \odot } for \sum m _ { \nu } = 0.6 eV and ( 8.21 \pm 0.13 ) \times 10 ^ { 12 } ~ { } h ^ { -1 } M _ { \odot } for \sum m _ { \nu } = 0.1 eV .
Subaru ( SuMIRe ) , Euclid and WFIRST will have both spectroscopic and weak lensing surveys .
Covering volumes at least 50 times larger than our simulations , they should be sensitive probes of neutrino mass through void substructure .