High-resolution mappings of the l =1.3 complex in molecular lines: Discovery of a proto-superbubble

Kunihiko Tanaka, Kazuhisa Kamegai, Makoto Nagai, Tomoharu Oka

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34 Citations (Scopus)


We report on the results of molecular line observations toward the l = 1,3 complex, an anomalous cloud complex in the central molecular zone of the Galaxy, The CO J=3-2 survey recently performed with the Atacama Submillimeter Telescope Experiment (ASTE) 10 m telescope has found that the complex has an enhanced CO J=3-2/J=1-0 intensity ratio. We have made high-resolution maps of the CO J=1-0, HCN J=1-0, HCO+ J=1-0, SiO J=1-0, and J=2-1 lines with the Nobeyama 45 m telescope. The complex is found to be rich in shells and arcs of dense molecular gas. We identified 9 expanding shells in HCN maps and compact SiO features associated with the shells. The intensity ratios of HCN/CO, HCO +/CO, and CO J=3-2/J=1-0 are coherently enhanced by a factor of a few in gas with an LSR velocity higher than 110 km s-1. The high-velocity gas has a high density (nH ∼ 104.5 cm-3) and high SiO/13CO intensity ratio, indicating that the gas was shocked. The typical HCN/HCO+ intensity ratio is found to be 2.3, being higher by a factor of a few than those in the Galactic disk clouds. The typical kinetic energy and expansion time of the shells are estimated to be 1050.9-52.5 erg and 104.6-5.3 yr, respectively. The kinetic energy could be furnished by multiple supernova and/or hypernova explosions at a rate of 10-3-4 yr-1. These estimates suggest that the expanding shells as a whole may be in the early stage of superbubble formation. This proto-superbubble may have originated in a massive cluster formation that took place 106.8-7.6 yr ago.

Original languageEnglish
Pages (from-to)323-333
Number of pages11
JournalPublications of the Astronomical Society of Japan
Issue number2
Publication statusPublished - 2007
Externally publishedYes


  • Galaxy: center

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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