High Spectral and Spatial Resolution Observations of Shocked Molecular Hydrogen at the Galactic Center

F. Yusef-Zadeh, S. R. Stolovy, M. Burton, M. Wardle, and M.C.B. Ashley

Paper: ApJ, in press

EPrint Server: astro-ph/0106190


Abstract:

The presence of OH (1720 MHz) masers, and the absence of counterparts at 1665/1667 MHz has proved to be a clear diagnostic of shocked molecular gas associated with Galactic supernova remnants. This suggests that shocked molecular gas should be associated with the OH (1720 MHz) masers that have been detected in the circumnuclear disk (CND) and Sgr A East at the Galactic center. In order to test this hypothesis, we observed the H2 1-0 S(1) and Br gamma lines using NICMOS on the HST and UNSWIRF on the AAT, near the regions where OH (1720 MHz) masers are detected in the CND and Sgr A East. We present the distribution of H2 in the North and South lobes of the CND and in Sgr A East. H2 emission accompanies almost all of the maser spots detected at the Galactic center. In particular, we find a striking filamentary structure near the Northwest of the CND and evidence that shocked molecular gas is associated with the 70 km/sec molecular cloud at the Galactic center. We argue that the emission from the CND could arise in gas heated by the dissipation of the random motion of clumps by collisions or the dissipation of turbulence in a more homogeneous medium. In addition, highly red-shifted gas of up to 140 km/sec close to the eastern edge of the Sgr A East shell is detected. These observations combined with OH (1720 MHz) results suggest that the H2 gas is shocked and accelerated by the expansion of Sgr A East into the 50 and the 70 km/sec cloud and into the lobes of the CND.


Preprints available from the authors at zadeh@oort.astro.nwu.edu , or the raw TeX (no figures) if you click here.

Back to the gcnews home-page.