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Revealing Elliptical Galaxy Halos
Duncan Forbes, Swinburne University
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Collaborators
• Robert Proctor (Sao Paulo)• Alan Brito (Swinburne)• George Hau (Swinburne) • Lee Spitler (Swinburne) • Caroline Foster (Swinburne)• Christina Blom (Swinburne)• Jean Brodie (UCSC)• Aaron Romanowsky (UCSC)• Jacob Arnold (UCSC) • Jay Strader (Harvard)• Soeren Larsen (Utrecht)
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Why study elliptical galaxy halos?
Also some kinematic signatures of galaxy formation only apparent at
large radii
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Halo stellar populations and kinematics using Deimos on
Keckmultiplexing times 4 !
Metallicity Kinematics
Globular Clusters ~10 Reff
Foster et al. In prep~10 Reff
Romanowsky et al. 2009
Halo starlight ~3 Reff
Foster et al. 2009~3 Reff
Proctor et al. 2009
“Need outer halo kinematics” - Rix
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Deimos spectra and fits to the galaxy halo light in the 3 Calcium Tripletregions
S/N
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NGC 2768: Deimos as an IFUNGC 2768: Deimos as an IFU
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Velocity map for NGC 2768Velocity map for NGC 2768
Sauron maps Reff = 64 arcsec
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Radial Kinematics - NGC 821
Proctor,Forbes etal. 2009
NGC 821: a low DM galaxy?
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N2768 and N821
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Anisotropy (Binney) diagramAnisotropy (Binney) diagram
NGC 2768
Fast -> Faster
NGC 821Fast ->Slow
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Metallicity gradients (<1Re) vs mass
Spolaor et al. 2009
Log sigma MB
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NGC 2768: Metallicity to ~3 Re
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Gal
axy
Hal
o M
ass
Globular Cluster System Mass
New Halo vs Globular Cluster Mass (linear)
Relation
Spitler & Forbes 2008
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Globular Cluster FormationGC formation is directly
proportional to the host halo mass with little environmental trend0.007% of Halo Mass = (Globular Cluster System Mass)
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Science progresses best when observations force us to alter our preconceptions.
Vera RubinTeacher and Coauthor
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Conclusions• New method for measuring 2D halo starlight kinematics and stellar populations to large Re
•Fast/slow rotators may change with radius.•Outer gE halos may be very metal-poor, built by low mass progenitors?•Mass modelling – see talk by Romanowsky. •New method for obtaining halo masses (based on globular cluster system mass) – see poster by Spitler.