H3O+ as a tracer of Galactic Center Black Hole activity

The center of the Milky Way harbors a now dormant massive blackhole (Sgr A*). Over the years evidence has mounted that Sgr A* releasedan energetic Xray flare nearly 100 years ago. The strongest evidence for thisis the detection of reflected Xray emission towards molecularclouds in the central regions of the galaxy. We believe that we havedirected direct evidence of the effects of this flare due to thepresence of warm (excitation termperature virgul 600800 K) H3O+ in theenvelope of the Sgr B2 molecular cloud. These observations wereobtained as part of the HEXOS key program and in all we have detected H3O+ J,K 1,1 through 11,11 each in absorption. These are the inversion transitions that lie at the bottom of a given K ladder. For J,K > 3 the transitions cannot be be excited by conventional collisional excitation or by radiative pumping. Instead our model strongly favors that the rotationally warm H3O+ is the result of formation pumping due to the strong impinging Xray flux, potentially from Sgr A*. We propose to follow up this fantastic result with a small search for rotationallywarm H3O+ absorption towards other galactic center molecular clouds that are strong continuum sources and are in close proximity to Sgr A*.This proposal follows a very interesting molecular astrophysical puzzle that may be a direct link to activity from the central engine of our galaxy. truncated!, Please see actual data for full text [truncated!, Please see actual data for full text]