1. Deep voids Frazer Pearce

2. Deepvoid catalogue 3000 >10Mpc diameter voids within the Millennium simulation 3000 >10Mpc diameter voids within the Millennium simulation Methodology Methodology Extension to “observational” void list Extension to “observational” void list Application to galaxy alignments Application to galaxy alignments

5. Method Rehash MS z=0 into 4096 41.25Mpc cubes (31.25+5Mpc padding) Rehash MS z=0 into 4096 41.25Mpc cubes (31.25+5Mpc padding) Calculate SPH-like density Calculate SPH-like density Order particles in density Order particles in density Select all particles at least 2Mpc away from any others selected Select all particles at least 2Mpc away from any others selected Stop at density 0.035x mean Stop at density 0.035x mean => 207,000 centres

6. Extract region around centre and produce radial profile Extract region around centre and produce radial profile Calculate first up-crossing of underdensities 0.1 and 0.2 Calculate first up-crossing of underdensities 0.1 and 0.2 Order voids in r 0.1 and delete any new centres inside a previous void Order voids in r 0.1 and delete any new centres inside a previous void => 3024 voids

8. Void Halo Properties (Jörg Colberg)

9. Radial structures of voids Both plots: halo mass vs. distance from void center (normalized by void radius) Both plots: halo mass vs. distance from void center (normalized by void radius) Top: δ=-0.9; bottom: δ=-0.8 Top: δ=-0.9; bottom: δ=-0.8 Bottom plot: haloes that have subhaloes shown in red Bottom plot: haloes that have subhaloes shown in red → void centers are very empty, haloes pile up near edges → void centers are very empty, haloes pile up near edges

12. Application to galaxy alignments (Brunino etal) Build “observational” void catalogue Build “observational” void catalogue For each deepvoid centre, search for 4 nearest haloes (plus allow centre to move) [Patiri etal] For each deepvoid centre, search for 4 nearest haloes (plus allow centre to move) [Patiri etal] Pick largest radius and keep voids >10Mpc across Pick largest radius and keep voids >10Mpc across Almost all trial centres produce observational voids Almost all trial centres produce observational voids

13. Calculate halo shapes, spins, alignments for all haloes in the Millennium simulation Calculate halo shapes, spins, alignments for all haloes in the Millennium simulation Examine haloes in shells around voids Examine haloes in shells around voids Cross-correlate with galaxy catalogue (Croton etal) to pick out haloes dominated by a large spiral Cross-correlate with galaxy catalogue (Croton etal) to pick out haloes dominated by a large spiral

18. Voids Define void catalogue for Millennium simulation Define void catalogue for Millennium simulation 3024 unique void centres 3024 unique void centres 10+Mpc/h diameter sphere of underdensity 10 10+Mpc/h diameter sphere of underdensity 10 Catalogue with void location, central density, radius of first upcrossing (0.1+0.2), radial density profile Catalogue with void location, central density, radius of first upcrossing (0.1+0.2), radial density profile

19. Deep voids Frazer Pearce