The Case for the Dual Halo of the Milky Way
  Carollo et al. have recently resolved the stellar population of the Milky Way
halo into at least two distinct components, an inner halo and an outer halo.
This result has been criticized by Schoenrich et al., who claim that the
retrograde signature associated with the outer halo is due to the adoption of
faulty distances. We refute this claim, and demonstrate that the Schoenrich et
al. photometric distances are themselves flawed because they adopted an
incorrect main-sequence absolute magnitude relationship from the work of
Ivezi\'c et al. When compared to the recommended relation from Ivezi\'c et al.,
which is tied to a Milky Way globular cluster distance scale and accounts for
age and metallicity effects, the relation adopted by Schoenrich et al. yields
up to 18% shorter distances for stars near the main-sequence turnoff (TO). Use
of the correct relationship yields agreement between the distances assigned by
Carollo et al. and Ivezi\'{c} et al. for low-metallicity dwarfs to within
6-10%. Schoenrich et al. also point out that intermediate-gravity stars (3.5 <=
log g <= 4.0) with colors redder than the TO region are likely misclassified,
with which we concur. We implement a new procedure to reassign luminosity
classifications for the TO stars that require it. New derivations of the
rotational behavior demonstrate that the retrograde signature and high velocity
dispersion of the outer-halo population remains. We summarize additional lines
of evidence for a dual halo, including a test of the retrograde signature based
on proper motions alone, and conclude that the preponderance of evidence
strongly rejects the single-halo interpretation.
