Deep voidsDeep voids

Frazer PearceFrazer Pearce

Deepvoid catalogueDeepvoid catalogue

3000 >10Mpc diameter voids within 3000 >10Mpc diameter voids within the Millennium simulationthe Millennium simulation

MethodologyMethodologyExtension to “observational” void listExtension to “observational” void listApplication to galaxy alignmentsApplication to galaxy alignments

MethodMethod

Rehash MS z=0 into 4096 41.25Mpc Rehash MS z=0 into 4096 41.25Mpc cubes (31.25+5Mpc padding)cubes (31.25+5Mpc padding)

Calculate SPH-like density Calculate SPH-like density Order particles in densityOrder particles in densitySelect all particles at least 2Mpc Select all particles at least 2Mpc

away from any others selectedaway from any others selectedStop at density 0.035x meanStop at density 0.035x mean

=> 207,000 centres=> 207,000 centres

Extract region around centre and Extract region around centre and produce radial profileproduce radial profile

Calculate first up-crossing of Calculate first up-crossing of underdensities 0.1 and 0.2underdensities 0.1 and 0.2

Order voids in rOrder voids in r0.10.1 and delete any new and delete any new centres inside a previous voidcentres inside a previous void

=> 3024 voids=> 3024 voids

Radial structures of voidsRadial structures of voids Both plots: halo mass Both plots: halo mass

vs. distance from vs. distance from void center void center (normalized by void (normalized by void radius)radius)

Top: Top: δδ=-0.9; bottom: =-0.9; bottom: δδ=-0.8 =-0.8

Bottom plot: haloes Bottom plot: haloes that have subhaloes that have subhaloes shown in redshown in red

→ → void centers are void centers are very empty, haloes very empty, haloes pile up near edgespile up near edges

Application to galaxy Application to galaxy alignments (Brunino etal)alignments (Brunino etal)

Build “observational” void catalogueBuild “observational” void catalogueFor each deepvoid centre, search for 4 For each deepvoid centre, search for 4

nearest haloes (plus allow centre to nearest haloes (plus allow centre to move) [Patiri etal]move) [Patiri etal]

Pick largest radius and keep voids Pick largest radius and keep voids >10Mpc across>10Mpc across

Almost all trial centres produce Almost all trial centres produce observational voidsobservational voids

Calculate halo shapes, spins, Calculate halo shapes, spins, alignments for all haloes in the alignments for all haloes in the Millennium simulationMillennium simulation

Examine haloes in shells around Examine haloes in shells around voidsvoids

Cross-correlate with galaxy Cross-correlate with galaxy catalogue (Croton etal) to pick out catalogue (Croton etal) to pick out haloes dominated by a large spiral haloes dominated by a large spiral

VoidsVoids Define void catalogue for Millennium Define void catalogue for Millennium

simulationsimulation

3024 unique void centres3024 unique void centres 10+Mpc/h diameter sphere of 10+Mpc/h diameter sphere of

underdensity 10underdensity 10 Catalogue with void location, central Catalogue with void location, central

density, radius of first upcrossing density, radius of first upcrossing (0.1+0.2), radial density profile(0.1+0.2), radial density profile

Deep voidsDeep voids

Frazer PearceFrazer Pearce