Revealing Elliptical Galaxy Halos
Duncan Forbes, Swinburne University
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)
Why study elliptical galaxy halos?
Also some kinematic signatures of galaxy formation only apparent at
large radii
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
Deimos spectra and fits to the galaxy halo light in the 3 Calcium Tripletregions
S/N
NGC 2768: Deimos as an IFUNGC 2768: Deimos as an IFU
Velocity map for NGC 2768Velocity map for NGC 2768
Sauron maps Reff = 64 arcsec
Radial Kinematics - NGC 821
Proctor,Forbes etal. 2009
NGC 821: a low DM galaxy?
N2768 and N821
Anisotropy (Binney) diagramAnisotropy (Binney) diagram
NGC 2768
Fast -> Faster
NGC 821Fast ->Slow
Metallicity gradients (<1Re) vs mass
Spolaor et al. 2009
Log sigma MB
NGC 2768: Metallicity to ~3 Re
Gal
axy
Hal
o M
ass
Globular Cluster System Mass
New Halo vs Globular Cluster Mass (linear)
Relation
Spitler & Forbes 2008
Globular Cluster FormationGC formation is directly
proportional to the host halo mass with little environmental trend0.007% of Halo Mass = (Globular Cluster System Mass)
Science progresses best when observations force us to alter our preconceptions.
Vera RubinTeacher and Coauthor
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.
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