From the Milky Way to Andromeda: A PAndAS View of Galactic Halos Brendan McMonigal Supervisor - Geraint F. Lewis Sydney Institute for Astronomy School 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 Telescope CFHT – 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 ~1/10 th 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)

Original image: Stephen Rahn (Flikr)

PAndAS Collaborators PAndAS: The Pan-Andromeda Archaeological Survey Alan McConnachie Lead 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] = [Fe/H] = [Fe/H] = [Fe/H] = -0.20

PAndAS Contamination Martin et al (2013) αβγ

Before and... Martin et al (2013)

...After Martin et al (2013)

Source Identification Martin et al (2013) Smoothed DensitySignificanceηM31 Halo [Fe/H] Dwarf [Fe/H]Log(N)Half light radiusDetections

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)