1110.4431 (Yoshiaki Sofue)
Yoshiaki Sofue
A grand rotation curve of the Milky Way Galaxy is constructed, which covers a
wide range of radius from the Galactic Center to 1 Mpc, and is deconvolved into
bulge, disk and halo components by least-squares fitting. We determined the
scale radii and masses of the bulge and disk to be M_b=(1.711 +/-0.072)E10
Msun, a_b=0.537 +/- 0.029 kpc, M_=(3.21+/- 0.46)E10 Msun and a_d=3.08+/-0.45
kpc. The dark halo was fitted by the Navaro-Frenk-White (NFW) density profile,
rho=rho_0/[(R/h) (1+R/h)^2], and the fit yielded h=16.3+/-1.1 kpc and
rho_0=(7.37 +/- 0.99)E-3 Msun pc^{-3}. The local dark matter density near the
Sun at R_0=8 kpc is estimated to be rho_0_at sun=(6.8 +/- 1.1)E-2 Msun pc^{-3}
= 0.26 +/- 0.04 GeV cm^-3. The total mass inside the gravitational boundary of
the Galaxy at R ~ 385 kpc, a half distance to M31, is estimated to be M_h ~
9.6E11 \Msun$. This leads to the stellar baryon fraction of
(Mb+Md)/(Mb+Md+Mh)=5.2 +/- 1.0 %. Considering expected baryon fraction in the
Local Group, we suggest that baryons in the form of gas are filling the dark
halo with temperature of ~ 10^6 K and emission measure ~ 10^{-4} pc cm^2. Such
hot halo gas may share a small fraction of the observed X-ray background
emission.
View original:
http://arxiv.org/abs/1110.4431
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