2011/10/31 by Yoshiaki Sofue · 1 citation
Physics and Astronomy · #astro-ph.GA
paper · pdf · doi:10.1093/pasj/64.4.75
PASJ 2012, Vol 64, No. 2, Preprint with full figures available at http://www.ioa.s.u-tokyo.ac.jp/~sofue/htdocs/2012DarkHalo/
arxiv created 2013/08/01 · arxiv updated 2015/05/29
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 Mb=(1.652 +/-0.083)x1010 Msun, ab=(0.522 +/- 0.037) kpc, Md=(3.41 +/- 0.41)x1010 Msun and ad=(3.19 +/- 0.3) kpc. The dark halo was fitted by the Navaro-Frenk-White (NFW) density profile, rho=rho0/[(R/h) (1+R/h)2], and the fit yielded h=12.5 +/- 0.9 kpc and rho0=(1.06 +/- 0.14)x10-2 Msun pc-3. The local dark matter density near the Sun at R0=8 kpc is estimated to be rho0sun=(6.12 +/-0.80)x10-3 Msun pc-3 = 0.235 +/- 0.030 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 Mh ~ (7.03 +/- 1.01)x1011 Msun. This leads to the stellar baryon fraction of (Mb+Md)/(Mb+Md+Mh)=0.072 +/-0.018. Considering expected baryon fraction in the Local Group, we suggest that baryons in the form of hot gas are filling the dark halo with temperature of ~ 106 K and emission measure ~ 10-5 pc cm-6. Such hot halo gas may share a small fraction of the observed X-ray background emission.