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تسجيل مستخدم جديدNumber Density Distribution of Near-Infrared Sources on a Sub-Degree Scale in the Galactic Center: Comparison with the Fe XXV Ka Line at 6.7 keV
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The stellar distribution derived from an $H$ and $K_{mathrm S}$-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 $|l| lesssim 3^{circ}.0$ and $|b| lesssim 1^{circ}.0$ (equivalent to 0.8 kpc $times$ 0.3 kpc for $R_0 = 8$ kpc), and the number-density distribution $N(K_{mathrm S,0}; l, b)$ of stars is derived using the extinction-corrected magnitude $K_{mathrm S,0}=10.5$. 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 ($b=0^{circ}$), $N(10.5; l, b)$ increases to the Galactic center as $|l|^{-0.30 pm 0.03}$ in the range of $-0^{circ}.1 geq l geq -0^{circ}.7$, but this increase is significantly slower than the increase ($|l|^{-0.44 pm 0.02}$ ) of the Fe XXV K$alpha$ line intensity. If normalized with the ratios in the outer region $1^{circ}.5 leq |l| leq 2^{circ}.8$, 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 $|l| = 0^{circ}.1$. 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.
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