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Blue RGB Red RGB 125 kpc 95 kpc Faintest features: Faintest features have
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Alan McConnachie
Mike Irwin, Annette Ferguson, Nial Tanvir, Rodrigo Ibata, Geraint Lewis, Scott Chapman, Avon Huxor
A Bird’s Eye View of M31 and its
Satellite Galaxies
IDM2004
The INT WFS of M31:
Ibata et al. 2001Ferguson et al. 2002
Irwin et al. 2004
Status as of July 2001(58 pointings)
Currently 165 pointings+ M33 (21 pointings) + total of 15 other dwarf galaxies
Blue RGB Red RGB12
5 kp
c
95 kpcFaintest features:
Faintest features have
Extent of the Stream:CFH12K Mosaic
McConnachie et al. 2003
Progress so far...
Ibata et al. 2004
radial velocities for ~15 000 stars in 34 distinct fields
concentrated on known substructure, general halo, and outer disk fields
RVs accurate to ~5km/s
McConnachie et al. 2004aKeck/DEIMOS radial velocity survey of M31
And VIIIIbata et al. 2004
First DIRECT measurement of the gravitational potential of a giant galaxy out to ~125 kpc:
Best fitting orbits:
Ibata et al. 2004
The Satellite Galaxies of Andromeda:
McConnachie et al. 2004b,c
Andromeda I & II
TRGB = 20.40 TRGB = 20.13
An M31 All-Sky View:(Aitoff equal-area projection)
An M31 All-Sky View:(Aitoff equal-area projection)
An M31 All-Sky View:
Preference for satellites to lie on near side of M31
The Line-of-Sight Probability Distribution Function
Why are the satellites lop-sided?
Why do they know about the Milky Way?
Are they tracing the underlying potential?
•Copious amounts of substructure: clue to formation history?
•First direct measure of dynamical mass of a galaxy over such a large distance range:
•Satellite distribution shows a strong anisotropy; tracers of underlying dark matter potential?
Summary: