GAS, DUSTY SOURCES AND ACCRETION IN THE GALACTIC CENTER

Anna Ciurlo – UCLA

The proximity of the Galactic Center makes it unique for studying the kinds of interactions that might be taking place between the interstellar medium, the stars and the supermassive black holes in galactic nuclei.  The galactic supermassive black hole is not very bright. The largest reservoir of material that could trigger a more intense phase is a molecular gas torus at about 1 pc but is presently kept at a distance. Smaller-scale processes can also accrete material onto the black hole and potentially trigger short peaks in the activity. Here I present the structure and dynamics of the ISM from few parsecs to sub-parsec scales through spectro-imaging data gathered by the VLT and Keck. In the central parsec the strong UV field is supposed to dissociate molecular hydrogen (H2). However,  I detected H2 everywhere. These molecules might have migrated from the molecular gas torus or have been formed in the winds of evolved mass-losing stars in the region. In the central few tenth of a parsec, I highlighted several compact emission sources (the « G-objects ») in Brγ emission line which are orbiting closely around the central supermassive black hole. The G objects are most likely the residuals of binaries merged under the influence of the black hole. These objects potentially offer a mechanism to episodically transport material onto the black hole and enhance its activity. The accretion rate of cooler gas very near the black hole is not strongly constrained. With our large Keck data-set I produced the highest signal-to-noise near-infrared spectrum of the immediate vicinity of the central black hole and test models of the accretion flow.