Thermal SiO observations of a shell attached to the nonthermal filaments in Sgr A

Handa Toshihiro1, Tsuboi Masato2, Sakano Masaaki3

1 Institute of Astronomy, University of Tokyo
2 Ibaraki University
3 University of Leicester

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The CS observations with NRO 45m telescope reveals that a dense molecular shell is located between Sgr A and the non-thermal filament of radio arc, and that the shell shows an interacting feature with the non-thermal filament (Tsuboi, Ukita and Handa, 1997). Using NRO 45m telescope we observed the shell in SiO (J=1-0, v=0) and SiO (J=2-1, v=0), which are thermally excited lines and thought to be an interstellar shock indicator.

Features associated with the shell are clearly appeared in both the SiO lines. All features associated with the shell are similar to those in the CS line in l-b-v 3-dimensional space. Intensity ratio of SiO (J=1-0) to CS (J=1-0) is ~0.24, using an intensity correlation diagram. Similarity between the CS and SiO features directly means X-ray features observed with ASCA and Chandra are also associated with the shell.

Intensity ratio of two SiO lines (J=2-1 over J=1-0) shows rather uniform over the shell, suggesting the shell is uniform in density. We estimated the averaged value of the ratio is ~0.9, using an intensity correlation diagram.

We will discuss about physical property of the shell and its origin.