科研之友
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摘要
We have discovered a molecular dome-like feature towards 355 degrees <= l <= 359 degrees and 0 degrees <= b <= 2 degrees. The large velocity dispersions of 50-100 km s(-1) of this feature are much larger than those in the Galactic disk, and indicate that the feature is located in the Galactic center, probably within similar to 1 kpc of Sgr A*. The distribution has a projected length of similar to 600 pc and a height of similar to 300 pc from the Galactic disk, and shows a large-scale monotonic velocity gradient of similar to 130 km s(-1) per similar to 600 pc. The feature is also associated with H I gas having a more continuous spatial and velocity distribution than that of (12)CO. We interpret the feature as being a magnetically floated loop similar to loops 1 and 2, and name it "loop 3". Loop 3 is similar to loops 1 and 2 in its height and length, but is different from loops 1 and 2 in that the inner part of loop 3 is filled with molecular emission. We have identified two foot points at both ends of loop 3. H I, (12)CO, and (13)CO datasets were used to estimate the total mass and the kinetic energy of loop 3 to be similar to 3.0 x 10(6) M(circle dot) and similar to 1.7 x 10(52) erg. The huge size, velocity dispersions, and energy are consistent with the magnetic origin of the Parker instability, as in the case of loops 1 and 2, but is difficult to be explained by multiple stellar explosions. We argue that loop 3 is in an earlier evolutionary phase than loops 1 and 2 based on the inner-filled morphology and the relative weakness of the foot points. This discovery indicates that the western part of the nuclear gas disk of similar to 1 kpc radius is dominated by the three well-developed magnetically floated loops, and suggests that the dynamics of the nuclear gas disk is strongly affected by magnetic instabilities.
- 出版日期2009
- 单位中国科学院国家天文台
