From the Milky Way to Andromeda: A PAndAS View of Galactic Halos
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Transcript of From the Milky Way to Andromeda: A PAndAS View of Galactic Halos
From the Milky Way to Andromeda: A PAndAS View of Galactic Halos
Brendan McMonigalSupervisor - Geraint F. Lewis
Sydney Institute for AstronomySchool of Physics, The University of Sydney
Original image: Stephen Rahn (Flikr)
Outline
• A PAndAS Introduction
• Mapping the contamination
• The Smooth Halo of M31
• A new MW Stream
Canada-France-Hawaii TelescopeCFHT – 3.6m on Hawaii
PAndAS(Pan-Andromeda Archaeological Survey)
MegaCam (~1 degree FOV)
Andromeda & Triangulum (M31 & M33)
M31 is a grand design spiral very similar to the MW, located at 780kpc.M33 has a mass ~1/10th that of the MW, located at a distance of 860kpc.
Separated on the sky by ~15 degrees on the sky (physical separation of 230kpc) and M33 may be a bound satellite of M31, although it appears to be very undisturbed.
Ibata et al (2014)
Martin et al (2013)
Martin et al (2013)
Original image: Stephen Rahn (Flikr)
Original image: Stephen Rahn (Flikr)
PAndAS Collaborators
PAndAS: The Pan-Andromeda Archaeological Survey
Alan McConnachieLead PI
Annette Ferguson
Rodrigo Ibata
Mike Irwin
Nicolas Martin
Scott Chapman Geraint Lewis
PAndAS Collaborators
Bullock & Johnston (2005) 300kpc
Expectations from Simulations
Full PAndAS CMD
Ibata et al (2014)
[Fe/H] = -1.91[Fe/H] = -1.29[Fe/H] = -0.71[Fe/H] = -0.20
PAndAS Contamination
Martin et al (2013)
α β γ
Before and...
Mar
tin e
t al (
2013
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...After
Mar
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t al (
2013
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Source Identification
Mar
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t al (
2013
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Smoothed Density Significance η M31 Halo [Fe/H]
Dwarf [Fe/H] Log(N) Half light radius Detections
Significance Map
Martin et al (2013)
Known Dwarf
Known GC
Detections
Martin et al (2013)
Known Dwarf
Known GC
Algorithm Detection
A New Extended Cluster
Martin et al (2013)
The search for the smooth halo
Ibata et al (2014)
Metal Poor
Metal Poor-ish
Metal Rich
Metal Rich-ish
The search for the smooth halo
Ibata et al (2014)
Metal Poor
Metal Poor-ish
Metal Rich
Metal Rich-ish
Combined Map
Ibata et al (2014)
Residuals
Ibata et al (2014)
Metal Poor
Metal Poor-ish
Metal Rich
Metal Rich-ish
Profiling: Metal Poor
Ibata et al (2014)
Profiling: Metal Poor-ish
Ibata et al (2014)
Profiling: Metal Rich (and Rich-ish)
Ibata et al (2014)
Substructure in the Milky Way
Koposov et al (2012)SDSS-III
Substructure in the Milky Way
Martin et al. (2014)
Substructure in the Milky Way
Take home points…• PAndAS: We now have the most comprehensive view of a galaxy halo out to
150kpc (as well as to 50kpc in M33)
• Substructure: We see extensive substructure, consisting of streams and clumps, both in Andromeda and the MW.
• Dwarf Population: We’ve uncovered a large populations of dwarf galaxies, but still not as many as expected from cosmological predictions (modulo gas physics).
Still to come: Globular Clusters (Nick), 3D structure (Anthony)