Sagittarius A Molecular Cloud Complex in H13CO+ and Thermal SiO Emission Lines

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We present results of a high-resolution wide-field mapping observation of the Sagittarius A (Sgr A) molec-ular cloud complex in H13CO+ J = 1-0 and thermal SiO J = 2-1 emission lines with the 25-beam receiver of the 100 GHz band operating on the Nobeyama Radio Observatory 45-m telescope. The mapping area covers a 0.°5 x × 0.°5 area involving several named molecular clouds, for example GCM -0.02-0.07, GCM -0.13-0.08, GCM 0.11-0.11, the Sickle molecular cloud, the Arched filaments molecular cloud, and so on. The data have an effective angular resolution of 26"". The H13CO+ emission line is a famous tracer of molecular gas mass because the line is optically thin, even in the Galactic center region, and is not emphasized by shock. The emission line presents a clumpy distribution of the molecular cloud. The averaged fractional abundance in the Sgr A complex is N (H13 CO+) /NH2 (1.8±0.4) ×10-11, comparing the LTE mass and the virial theorem mass. The SiO emission line is a famous and reliable tracer of shocked molecular gas. We find many molecular clouds that are remarkable only in the SiO emission line. Such molecular clouds have a large velocity width of up to 60km s-1. The brightness temperature ratio is up to TB(SiO)/ TB(H13CO+) < 8. The features are dominated by shock SiO-enriched gas. In such clouds, the ratio of the fractional abundance of SiO and H13CO+ molecules is X (Si0)/ x(H13CO+)~ 100. The features are presumably made by supernova remnants. We found a prototypical example in GCM -0.02-0.07. It has two distinct structures. One is a ridge-like structure contacting with the Sgr A East shell; another is an expanding shell-like structure. There is a wide-velocity width ridge of SiO-enriched gas in GCM 0.11-0.11, which is adja-cent to Vertical filaments. This suggests that the collision with the molecular cloud accelerates relativistic electrons, which illuminate the Vertical filaments-Polarized Plumes complex.

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