Which Milky Way masses are consistent with the slightly declining 5-25
  kpc rotation curve?
  Discoveries of extended rotation curves have suggested the presence of dark
matter in spiral galaxy haloes. It has led to many studies that estimated the
galaxy total mass, mostly by using the Navarro Frenk and White (NFW) density
profile. We aim at verifying how the choice of the dark-matter profile may
affect the predicted values of extrapolated total masses. We have considered
the recent Milky Way (MW) rotation curve, firstly because of its unprecedented
accuracy, and secondly because the Galactic disk is amongst the least affected
by past major mergers having fully reshaped the initial disk. We find that the
use of NFW profile (or its generalized form, gNFW) for calculating the
dark-matter contribution to the MW rotation curve generates apparently
inconsistent results, e.g., an increase of the baryonic mass leads to increase
of the dark matter mass. Furthermore we find that NFW and gNFW profile narrow
the total mass range, leading to a possible methodological bias particularly
against small MW masses. By using the Einasto profile that is more appropriate
to represent cold dark matter haloes, we finally find that the Milky Way
slightly decreasing rotation curve favors total mass that can be as small as
2.6 $\times 10^{11}$ $M_{\odot}$, disregarding any other dynamical tracers
further out in the MW. It is inconsistent with values larger than 18 $\times
10^{11}$ $M_{\odot}$ for any kind of CDM dark-matter halo profiles, under the
assumption that stars and gas do not influence the predicted dark matter
distribution in the MW. This methodological paper encourages the use of the
Einasto profile for characterizing rotation curves with the aim of evaluating
their total masses.
