Molecular line observations of the Tornado nebula and its Eye

J. Lazendic1, M. Burton2, F. Yusef-Zadeh3, M. Wardle4, A. Green4 & J. Whiteoak5

1 Harvard-Smithsonian CfA
2 University of New South Wales
3 Northwestern University
4 University of Sydney
5 Australia Telescope National Facility

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The Tornado nebula is a peculiar radio source located towards the Galactic Center region. It has been classified as a supernova remnant (SNR) due to its steep radio spectrum and linear polarization, but its unique morphology has led to other interpretations (e.g. accretion powered nebula). The Eye of Tornado is a compact radio source located 30'' from the emission peak of the nebula. It was initially thought to be responsible for the formation of the nebula (e.g. through mass ejections from a pulsar or accreting binary system), but was found to have a flat radio spectrum and was classified as an HII region.

We present molecular line observations of the Tornado and its Eye which show that the two objects are not spatially related, despite their apparent proximity. Our NIR Br gamma and HI line emission, in conjuction with the CO 1-0 and high-resolution radio observations, suggests that the Eye is a massive protostellar source deeply embedded within a dense molecular core.

OH(1720 MHz) maser emission, believed to be indicator of molecular-cloud/SNR interaction, was found towards the nebula. Consequently, we mapped the region in two CO transitions to investigate the implied interaction. These observations revealed that the distribution of molecular gas around the Tornado compliments its radio morphology, implying that the nebula's appearance was ifluenced by the structure of the surrounding molecular gas. Our NIR H2 observations reveal the presence of shocked molecular gas at the location where the shock wave from the nebula is expanding into the surrounding molecular cloud.