Grand Rotation Curve, Dark Halo, and Baryon Fraction in the Milky Way Galaxy

摘要

Grand rotation curve of the Milky Way Galaxy was constructed, which covers from the Galactic Center to Local Group (～ 1 Mpc). Least-sq. fit by bulge, disk and NFW dark halo resulted Galactic parameters in table 1, leading to local dark matter density of ～ 0.235 ± 0.030 GeV cm~(-3). We obtain stellar baryon fraction M(b+d) / M(b+d+h) = 0.072 ± 0.018, smaler than those in the universe (WMAP: 17%) or groups of galaxies (～ 12%). Missing baryons (～ 5%) may exist as hot gas of ～ 10~6 K and EM ～ 10~(-5) pc cm~(-6), sharing a small fraction of X-ray background.