Hypervelocity Stars Ejected from the Galactic Center MMT

Hypervelocity Stars Ejected from the Galactic Center MMT Symposium June 14, 2006 Warren R. Brown Harvard-Smithsonian Cf. A Collaborators: Margaret Geller, Scott Kenyon, Michael Kurtz

The Milky Way 30 kpc 8 kpc r=100 kpc Kaufmann

The Galactic Center http: //www. mpe. mpg. de/ir/GC/prop. html

Eisenhauer et al. 2005

Three-body exchange Bromley 2005

Radial Velocities from the MMT

An Unexpected Star Brown et al. (2005) • VRF = +709 km/s • B 9 main sequence star. • [Fe/H] ~ 0. • Distance ~110 kpc. • Travel time ~160 Myr to 110 kpc.

A Hypervelocity Star Brown et al. (2005) • VRF = +709 km/s • B 9 main sequence star. • [Fe/H] ~ 0. • Distance ~110 kpc. • Travel time ~160 Myr to 110 kpc. NY Times

Our Search for more Hypervelocity Stars Fukugita et al (1996) Brown et al. (2005)

Our Search for more Hypervelocity Stars Fukugita et al (1996) Brown et al. (2006 a)

Our Search for more Hypervelocity Stars Fukugita et al (1996) Brown et al. (2006 b)

New Discoveries Brown et al. (2006 b) astro-ph/0604111

The Big Picture Brown et al. (2006 b) -300 0 +300 km/s

Mass Function of Stars We Observe: ~40 3 -4 Msun HVSs 4 HVS in 4000 deg 2 U. Heber Salpeter 16 3 -4 Msun stars Predicted: 2000 HVSs Arches (Yu & Tremaine) 460 3 -4 Msun stars NASA HST

Applications: Galactic • Yu & Tremaine (2003): HVS rates • Gualandris et al (2005): velocities Ginsburg & Loeb (2006) • Ginsburg & Loeb (2005): orbits • Levin (2005): in-spiral signature LISA • Gnedin et al (2005): dark matter

Applications: Extra-Galactic M 87 • Holley-Bockelmann et al. (2006): M 87 planetary nebulae? D. Malin M 31 • Demarque & Virani (2006): center of M 31? J. Ware Bender et al (2005)

Coming Attractions • Discovery surveys: MMT, 1. 5 m. • Spectroscopic identifications: HET, VLT (Edelmann, Heber). • Space velocities: HST (Gnedin). • Variability: MDM (Stanek). • N-body simulations: (Bromley). • Other unusual objects: (Kewley).

Conclusions • MBH a hypervelocity stars. • First HVS: B star +709 km/s • Now seven known HVSs. NY Times • Provide constraints on mass function of stars and infall history of MBH.

The Hypervelocity Stars ID Type g’ VRF d t. GC (mag) (km/s) (kpc) (Myr) Citation HVS 1 B 19. 8 +709 110 160 Brown et al. (2005) HVS 2 sd. O 18. 8 +717 19 32 Hirsch et al. (2005) HVS 3 B 16. 2 +548 61 100 Edelmann et al. (2005) HVS 4 B? 18. 4 +558 75 140 Brown et al. (2006 a) HVS 5 B? 17. 9 +638 55 90 Brown et al. (2006 a) HVS 6 B? 19. 1 +508 75 160 Brown et al. (2006 b) HVS 7 B? 17. 7 +418 55 120 Brown et al. (2006 b)