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Hypervelocity Stars Ejected from the Galactic Center. MMT Symposium June 14, 2006 Warren R. Brown Harvard-Smithsonian CfA Collaborators: Margaret Geller, Scott Kenyon, Michael Kurtz. The Milky Way. 30 kpc. 8 kpc. r=100 kpc. Kaufmann. The Galactic Center.
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Hypervelocity StarsEjected from the Galactic Center MMT Symposium June 14, 2006 Warren R. Brown Harvard-Smithsonian CfA 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
Three-body exchange Bromley 2005
An Unexpected Star Brown et al. (2005) • VRF = +709 km/s • B9 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 • B9 main sequence star. • [Fe/H] ~ 0. • Distance ~110 kpc. • Travel time ~160 Myr to 110 kpc. NY Times
Our Search for more Hypervelocity Stars O B F A G K M Fukugita et al (1996) Brown et al. (2005)
Our Search for more Hypervelocity Stars O B F A G K M Fukugita et al (1996) Brown et al. (2006a)
Our Search for more Hypervelocity Stars O B F A G K M Fukugita et al (1996) Brown et al. (2006b)
New Discoveries HVSs Brown et al. (2006b) astro-ph/0604111
The Big Picture Brown et al. (2006b) -300 0 +300 km/s
Mass Function of Stars We Observe: 4 HVS in 4000 deg2 ~40 3-4 Msun HVSs U. Heber Salpeter 16 3-4 Msun stars Predicted: 2000 HVSs (Yu & Tremaine) Arches 460 3-4 Msun stars NASA HST
Applications: Galactic • Yu & Tremaine (2003): HVS rates • Gualandris et al (2005): velocities • Ginsburg & Loeb (2005): orbits • Levin (2005): in-spiral signature • Gnedin et al (2005): dark matter Ginsburg & Loeb (2006) LISA
Applications: Extra-Galactic • Holley-Bockelmann et al. (2006): M87 planetary nebulae? • Demarque & Virani (2006): center of M31? M87 D. Malin M31 J. Ware Bender et al (2005)
Coming Attractions • Discovery surveys: MMT, 1.5m. • 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. • Provide constraints on mass function of stars and infall history of MBH. NY Times
The Hypervelocity Stars Brown et al. (2006b)