A Detailed Observational Study of Molecular Loops 1 and 2 in the Galactic Center

作者：Torii Kazufumi^*; Kudo Natsuko; Fujishita Motosuji; Kawase Tokuichi; Yamamoto Hiroaki; Kawamura Akiko; Mizuno Norikazu; Onishi Toshikazu; Mizuno Akira; Machida Mami; Takahashi Kunio; Nozawa Satoshi; Matsumoto Ryoji; Fukui Yasuo

来源：Publications of the Astronomical Society of Japan, 2010, 62(5): 1307-1332.

• ISM: clouds
• ISM: magnetic fields
• magnetic loops
• radio lines: ISM

Fukui et al. (2006, Science, 314, 106) discovered two huge molecular loops in the galactic center located at (l, b) similar or equal to (355 degrees-359 degrees, 0 degrees-2 degrees) in a large velocity range of -180-40 km s(-1). Following the discovery, we present detailed observational properties of the two loops based on NANTEN (CO)-C-12 (J = 1-0) and (CO)-C-13 (J = 1-0) datasets at 10 pc resolution, including a complete set of velocity channel distributions and comparisons with H and dust emissions as well as with the other broad molecular features. We have found new features on smaller scales in the loops, including helical distributions in the loop tops and vertical spurs. The loops have counterparts of the H I gas, indicating that the loops include atomic gas. The IRAS far-infrared emission is also associated with the loops, and was used to derive an X-factor of 0.7 (+/- 0.1) x 10(20) cm(-2) (K km s(-1))(-1) to convert the (CO)-C-12 intensity into the total molecular hydrogen column density. From the (CO)-C-12, (CO)-C-13, H I, and dust datasets we estimated the total mass of loops 1 and 2 to be similar to 1.4 x 10(6) M-circle dot and similar to 1.9 x 10(6) M-circle dot respectively, where the H I mass corresponds to similar to 10%-20% of the total mass and the total kinetic energy of the two loops is similar to 10(52) erg. An analysis of the kinematics of the loops yields that the loops are rotating at similar to 47 km s(-1) and expanding at similar to 141 km s(-1) at a radius of similar to 670 pc from the center. Fukui et al. (2006) presented a model that the loops are created by magnetic flotation due to the Parker instability with an estimated magnetic field strength of similar to 150 mu G. We present comparisons with the recent numerical simulations of the magnetized nuclear disk by Machida et al. (2009, PASJ, 61, 411) and Takahashi et al. (2009, PASJ, 61, 957), and show that the theoretical results are in good agreement with the observations. The helical distributions also suggest that some magnetic instability plays a role similarly to the solar helical features.

• 出版日期2010
• 单位中国科学院国家天文台