Number density distribution of near-infrared sources on a sub-degree scale in the Galactic center: Comparison with the Fe XXV K alpha line at 6.7 keV

作者：Yasui Kazuki^*; Nishiyama Shogo; Yoshikawa Tatsuhito; Nagatomo Schun; Uchiyama Hideki; Tsuru Takeshi Go; Koyama Katsuji; Tamura Motohide; Kwon Jungmi; Sugitani Koji; Schodel Rainer; Nagata Tetsuya

来源：Publications of the Astronomical Society of Japan, 2015, 67(6): 123.

DOI：10.1093/pasj/psv100

• Galaxy: center
• infrared: stars
• ISM: lines and bands
• X-rays: general

The stellar distribution derived from an H- and KS-band survey of the central region of our Galaxy is compared with the Fe xxv K alpha (6.7 keV) line intensity observed with the Suzaku satellite. The survey is for the galactic coordinates |l| less than or similar to 3 degrees 0 and |b| less than or similar to 1 degrees 0 (equivalent to 0.8 kpc x 0.3 kpc for R-circle dot = 8 kpc), and the number-density distribution N( K-S,(0); l, b) of stars is derived by using the extinction-corrected magnitude K-S,(0) = 10.5. This is deep enough to probe the old red-giant population and in turn to estimate the (l, b) distribution of faint X-ray point sources such as coronally active binaries and cataclysmic variables. In the Galactic plane (b= 0 degrees.), N(10.5; l, b) increases in the direction of the Galactic center as | l |(- 0.30 +/- 0.03) in the range of - 0 degrees.1 greater than or similar to l greater than or similar to - 0 degrees.7, but this increase is significantly slower than the increase (| l|(- 0.44 +/- 0.02)) of the Fe xxv K alpha line intensity. If normalized with the ratios in the outer region 1 degrees.5 less than or similar to | l | less than or similar to 2.degrees. 8, where faint X-ray point sources are argued to dominate the diffuse Galactic X-ray ridge emission, the excess of the Fe xxv K alpha line intensity over the stellar number density is at least a factor of two at | l | = 0.degrees 1. This indicates that a significant part of the Galactic-center diffuse emission arises from a truly diffuse optically thin thermal plasma, and not from an unresolved collection of faint X-ray point sources related to the old stellar population.

• 出版日期2015-12