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26 April 2024 |
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Temperature and Density in the Foot Points of the Molecular Loops in the Galactic Center; Analysis of Multi-J Transitions of 12CO(J=1-0, 3-2, 4-3, 7-6), 13CO(J=1-0) and C18O(J=1-0) | | Kazufumi Torii
; Natsuko Kudo
; Motosuji Fujishita
; Tokuichi Kawase
; Takeshi Okuda
; Hiroaki Yamamoto
; Akiko Kawamura
; Norikazu Mizuno
; Toshikazu Onishi
; Mami Machida
; Kunio Takahashi
; Satoshi Nozawa
; Ryoji Matsumoto
; Juergen Ott
; Kunihiko Tanaka
; Nobuyuki Yamaguchi
; Hajime Ezawa
; Juergen Stutzki
; Uli Klein
; Frank Bertoldi
; Koo Bon-Chul
; Leonardo Bronfman
; Michael Burton
; Arnold Benz
; Hideo Ogawa
; Yasuo Fukui
; | | Date: |
11 Sep 2009 | | Abstract: | Fukui et al. (2006) discovered two molecular loops in the Galactic center and
argued that the foot points of the molecular loops, two bright spots at the
both loop ends, represent the gas accumulated by the falling motion along the
loops, subsequent to the magnetic flotation by the Parker instability. We have
carried out sensitive CO observations of the foot points toward l = 356 deg. at
a few pc resolution in the six rotational transitions of CO; 12CO(J=1-0, 3-2,
4-3, 7-6), 13CO(J=1-0) and C18O(J=1-0). The high resolution image of
12CO(J=3-2) has revealed detailed distribution of the high excitation gas
including a U shape, the outer boundary of which shows sharp intensity jumps
accompanying strong velocity gradients. An analysis of the multi-J CO
transitions shows that temperature is in a range from 30 - 100 K or higher and
density is around 10^3 - 10^4 /cm^3, confirming that the foot points have high
temperature and density although there is no radiative heat source like high
mass stars in and around the loops. We argue that the high temperature is
likely due to the shock heating under C-shock condition caused by the magnetic
flotation. We made a detailed comparison of the distribution obtained with
theoretical numerical simulations and note that the U shape seems to be
consistent with numerical simulations. We also find that the region of highest
temperature of 60 K or higher inside the U shape corresponds to the spur having
upward flow, additionally heated up either by magnetic reconnection or bouncing
in the interaction with the narrow "neck" at the bottom of the U shape. We note
these new findings further reinforce the magnetic floatation interpretation. | | Source: | arXiv, 0909.2073 | | Services: | Forum | Review | PDF | Favorites | |
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