Nuclear Star-Forming Ring of the Milky Way: Simulations

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Kim, Sungsoo S.
Saitoh, Takayuki R.
Jeon, Myouungwon
Figer, Donald F.
Merritt, David
Wada, Keiichi

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We present hydrodynamic simulations of gas clouds in the central kpc region of the Milky Way that is modeled with a three-dimensional bar potential. Our simulations consider realistic gas cooling and heating, star Formation, and supernova feedback. A ring of dense gas clouds forms as a result of X-1-X-2 orbit transfer, and our potential model results in a ring radius of similar to 200 pc, which coincides with the extraordinary reservoir of dense molecular clouds in the inner bulge, the Central Molecular Zone (CMZ). The gas clouds accumulated in the CMZ can reach high enough densities to form stars, and with an appropriate choice of simulation parameters, we successfully reproduce the observed gas mass and the star Formation rate (SFR) in the CMZ, similar to 2 x 10(7) M-circle dot and similar to 0.1 M-circle dot yr(-1). Star Formation in our simulations takes place mostly in the outermost X-2 orbits, and the SFR per unit surface area outside the CMZ is much lower. These facts suggest that the inner Galactic bulge may harbor a mild version of the nuclear star-forming rings seen in some external disk galaxies. Furthermore, from the relatively small size of the Milky Way's nuclear bulge, which is thought to be a result of sustained star Formation in the CMZ, we infer that the Galactic inner bulge probably had a shallower density profile or stronger bar elongation in the past.



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Kim, Sungsoo S., Takayuki R. Saitoh, Myoungwon Jeon, Donald F. Figer, David Merritt, and Keiichi Wada. "Nuclear Star-forming Ring of the Milky Way: Simulations." The Astrophysical Journal Letters, Vol. 735, No. 1 (Jul., 2011): L11.