The Ultra Violet Output of Sgr A*

Flows in the accretion disks surrounding supermassive black holes are central to virtually all observations of these objects, as well as to the consequences they have on their environments. This topic is complex because accretion disks are three-dimensional, turbulent, frequently self-gravitating, and strongly influenced by magnetic fields. Furthermore, in nearly all cases the system is too distant for detailed study. Sgr A* provides a unique laboratory to study this process through detailed imaging of the effects of the black hole on its environment, given that it is orders of magnitude closer than any other example. We will answer a key question about models of the accretion disk around Sgr A*, namely whether purely thermal or hybrid thermal/nonthermal models are appropriate. This ambiguity arises because plasma instabilities can accelerate electrons and push the electron distribution function into a non-thermal state. Hybrid models predict UV fluxes 3 orders of magnitude higher in that case than pure thermal models. We will make a definitive test of this prediction using a very deep search for the [Ne VI] line, ionization potential 126 eV, at 7.64 microns. This result fills in a key aspect of the theory of the nearest, and best studied, super-massive black hole and its accretion disk.