Astrophysical constraints on a possible neutrino ball at the galactic center

The nature of the massive object at the Galactic Center (Sgr A*) is still unclear even if various observational campaigns led many authors to believe that our Galaxy hosts a super-massive black hole with mass M =~ 2.6x 106 Msun. However, the black hole hypothesis, which theoretically implies a luminosity =~ 1041 erg s-1, runs into problems if one takes into account that the observed luminosity, from radio to gamma -ray wavelengths, is below 1037 erg s-1. In order to solve this blackness problem, alternative models have recently been proposed. In particular, it has been suggested that the Galactic Center hosts a ball made up of non-baryonic matter ({e.g.} massive neutrinos and anti-neutrinos) in which the degeneracy pressure of fermions balances their self-gravity. Requiring it to be consistent with all the available observations towards the Galactic Center allows us to put severe astrophysical constraints on the neutrino ball parameters. The presence of such an object in the Galactic Center may be excluded if the constituent neutrino mass mnu is >~ 24 keV, while if mnu <~ 24 keV observations cannot give a definite answer.