The Andromeda Effect: Dark Matter Halos in a Local Group - PowerPoint PPT Presentation

The Andromeda Effect: Dark Matter Halos in a Local Group Configuration with James Bullock, Jose Oñorbe, Shea Garrison-Kimmel UC Irvine Mike Boylan-Kolchin, and Kyle Lee Thursday, August 16, 12

The “Local Volume” Thursday, August 16, 12

The “Local Volume” Thursday, August 16, 12

The “Local Volume” Thursday, August 16, 12

The “Local Volume” Thursday, August 16, 12

The “Local Volume” Thursday, August 16, 12

Redefining “Near-Field” Astronomy SDSS Limit Thursday, August 16, 12

Redefining “Near-Field” Astronomy SDSS Limit R vir Thursday, August 16, 12

Redefining “Near-Field” Astronomy LSST SDSS Limit R vir Thursday, August 16, 12

Looking for Local Groups in Simulations Thursday, August 16, 12

Looking for Local Groups in Simulations Selected otherwise isolated pairs of halos in thirty-four 70 Mpc Gadget2 runs with: • • • Thursday, August 16, 12

Looking for Local Groups in Simulations Selected otherwise isolated pairs of halos in thirty-four 70 Mpc Gadget2 runs with: • • • Identified 880 pairs (find one pair per ~(24 Mpc) 3 ) Thursday, August 16, 12

Paired Halos: LG Analogues? V radial km/s Thursday, August 16, 12

Paired Halos: LG Analogues? V radial n 4 Mpc /n box Over-density of halos bigger than SMC within 4 Mpc km/s Thursday, August 16, 12

Paired Halos: LG Analogues? V radial n 4 Mpc /n box Over-density of halos bigger than SMC within 4 Mpc km/s V tangential km/s Thursday, August 16, 12

Paired Halos: LG Analogues? V radial n 4 Mpc /n box Over-density of halos bigger than SMC within 4 Mpc km/s V tangential Tikhonov & Observed Klypin, 2009 van der Marel et al., 2012 km/s Thursday, August 16, 12

Paired Halos: LG Analogues? V radial n 4 Mpc /n box Over-density of halos bigger than SMC within 4 Mpc km/s V tangential Tikhonov & Observed Klypin, 2009 We find similar distributions in Bolshoi (Klypin van der Marel et al., 2011) et al., 2012 km/s Thursday, August 16, 12

Paired Halos: LG Analogues? n 4 Mpc /n box Paired Halos n 4 Mpc /n box Isolated Halos Thursday, August 16, 12

Resolution Requirements N(>V max ) V max Simulating the same halo at four resolutions Thursday, August 16, 12

Resolution Requirements N(>V max ) Resolution Limit V max Simulating the same halo at four resolutions Thursday, August 16, 12

The ELVIS Suite: Exploring the Local Volume In Simulations • Twenty-two halos in LG-like configurations • Twenty-two mass-matched isolated halos Thursday, August 16, 12

The ELVIS Suite: Exploring the Local Volume In Simulations • Twenty-two halos in LG-like configurations • Twenty-two mass-matched isolated halos • • • Thursday, August 16, 12

The ELVIS Suite: Exploring the Local Volume In Simulations • Twenty-two halos in LG-like configurations • Twenty-two mass-matched isolated halos • • • Thursday, August 16, 12

The ELVIS Suite: Exploring the Local Volume In Simulations • Twenty-two halos in LG-like configurations • Twenty-two mass-matched isolated halos • • • Up to 15 million particles in a halo and up to 42 million high-res particles in the uncontaminated region Thursday, August 16, 12

~1 Mpc Thursday, August 16, 12

Thursday, August 16, 12

Structure Formation in LG Pairs z = 0 Thursday, August 16, 12

Structure Formation in LG Pairs z = 0 z = 7 Thursday, August 16, 12

Halos within R vir Isolated Sample Paired Sample N(>V peak ) Samples agree within the virial radius V peak V peak maximum circular velocity over all time Thursday, August 16, 12

Halos within R vir Isolated Sample Paired Sample N(>V peak /V vir ) Samples agree within the virial radius V peak /V vir Thursday, August 16, 12

Halos within 1 Mpc Isolated Sample Paired Sample N(>V peak /V vir ) V peak /V vir Thursday, August 16, 12

1 Mpc Thursday, August 16, 12

1 Mpc Thursday, August 16, 12

Halos outside MW and M31 Isolated Sample Paired Sample N(>V peak /V vir ) ~60% more halos in paired environments V peak /V vir Thursday, August 16, 12

Conclusions • New surveys (Pan-STARRS, SkyMapper, DES, LSST, etc.) are pushing the boundaries of discovery within the Local Group • Simulations need to resolve large regions with a comparable mass halo nearby to confront these data • Overdensity of galaxies brighter than SMC within 4 Mpc isn’t unexpected for halos that live in Local Group configurations Thursday, August 16, 12

Conclusions • ELVIS Suite: • Eleven Local Group pairs selected for zoom simulations from large volume simuations • Twenty two mass-matched isolated halos • Subhalo number counts within R vir agree between isolated and LG zoom simulations • LG simulations predict about 150 galaxies larger than Carina outside R vir of the MW or M31 but within 1 Mpc, versus only about 90 in isolated simulations Thursday, August 16, 12