A detailed observational study of molecular loops 1 and 2 in the galactic center

Kazufumi Torii, Natsuko Kudo, Motosuji Fujishita, Tokuichi Kawase, Hiroaki Yamamoto, Akiko Kawamura, Norikazu Mizuno, Toshikazu Onishi, Akira Mizuno, Mami MacHida, Kunio Takahashi, Satoshi Nozawa, Ryoji Matsumoto, Yasuo Fukui

Research output: Contribution to journalArticlepeer-review

24 Citations (Scopus)

Abstract

Fukui et al. (2006, Science, 314, 106) discovered two huge molecular loops in the galactic center located at (l , b) ≃ (355°-359°, 0°-2°) in a large velocity range of -180-40km s-1. Following the discovery, we present detailed observational properties of the two loops based on NANTEN 12CO (J = 1-0) and 13CO(J = 1-0) datasets at 10 pc resolution, including a complete set of velocity channel distributions and comparisons with HI and dust emissions as well as with the other broadmolecular 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 HI 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) × 1020cm -2 (K km s-1)-1 to convert the 12CO intensity into the total molecular hydrogen column density. From the 12CO, 13CO, HI, and dust datasets we estimated the total mass of loops 1 and 2 to be ∼1.4 × 106M⊙ and ∼1.9 × 106M⊙, respectively, where the HI mass corresponds to ∼10%-20% of the total mass and the total kinetic energy of the two loops is ∼1052 erg. An analysis of the kinematics of the loops yields that the loops are rotating at ∼47 km s-1 and expanding at ∼141km s-1 at a radius of ∼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 ∼150μG.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.

Original languageEnglish
Pages (from-to)1307-1332
Number of pages26
JournalPublications of the Astronomical Society of Japan
Volume62
Issue number5
DOIs
Publication statusPublished - Oct 25 2010

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science

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