Abstract details

How clumpy are galactic halos? Recent observations around both the Milky Way and the Andromeda galaxy (M31) have revealed numerous faint stellar streams and dwarf galaxies, leading to the belief that more of these may yet remain undetected. I will present the first results from the Megacam/CFHT survey that our group has undertaken in the outer halo of M31 and that, for the first time, gives a deep panoramic view of a significant region of a spiral galaxy halo. This panoramic survey covers $\sim$60 sq. deg. of the southern quadrant of the M31 halo, extends from a projected distance of $\sim$50 to $\sim$150 kpc and is deep enough to cover three magnitudes below the tip of the red giant branch of stellar populations at the distance of M31. The survey reveals Andromeda has a clumpy halo with none less than two previously undetected faint streams, three extremely faint dwarf galaxies and the most remote globular cluster in the Andromeda halo. We are also able to show that faint dwarf galaxies cannot alone explain the so-called missing satellite problem.