Interaction between the Northeastern Boundary of Sgr A East and Giant Molecular Clouds

Sungho Lee1, Soojong Pak1, Christopher J. Davis2, Robeson M. Herrnstein3, Thomas R. Geballe4, Paul T. P. Ho3, and J. Craig Wheeler5

1 Astronomy Program in SEES, Seoul National University, Shillim-Dong, Kwanak-Gu, Seoul 151-742, South Korea
2 Joint Astronomy Centre, University Park, 660 North A'ohoku Place, Hilo, HI 96720, USA
3 Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA
4 Gemini Observatory, 670 N. A'ohoku Place, Hilo, HI 96720, USA
5 Astronomy Department, University of Texas, Austin, TX 78712, USA

E-mail contact: leesh@astro.snu.ac.kr, soojong@astro.snu.ac.kr, c.davis@jach.hawaii.edu, rmcgary@cfa.harvard.edu, tgeballe@gemini.edu, pho@cfa.harvard.edu, wheel@astro.as.utexas.edu

We have detected the v=1-0 S(1) 2.1218um and v=2-1 S(1) 2.2477um lines of H2 in the Galactic centre, in a 90 x 27 arcsec region between the northeastern boundary of the non-thermal source, Sgr A East, and the giant molecular cloud (GMC) M-0.02-0.07. The detected emission has an intensity of 1.6 - 21 x 10^-18 W/m^2/arcsec^2 and is present over most of the region. Along with the high intensity, the broad line widths (FWHM = 40 - 70 km/s) and the 2-1 S(1) / 1-0 S(1) line ratios (0.3 - 0.5) can be best explained by a combination of C-type shocks and fluorescence. The detection of shocked H2 is clear evidence that Sgr A East is driving material into the surrounding adjacent cool molecular gas. The H2 emission lines have two velocity components at +50 km/s and 0 km/s, which are also present in the NH3(3,3) emission mapped by McGary, Coil, and Ho (2001). This two-velocity structure can be explained if Sgr A East is driving C-type shocks into both the background GMC M-0.02-0.07 and the northern ridge of McGary, Coil, and Ho (2001).

References:
McGary, R. S., Coil, A. L., and Ho, P. T. P. 2001, ApJ, 559, 326