2012A&A...538A.127K

The mini-spiral is a feature of the interstellar medium in the central ∼2pc of the Galactic center. It is composed of several streamers of dust and ionised and atomic gas with temperatures between a few 100K to 10⁴K. There is evidence that these streamers are related to the so-called circumnuclear disk of molecular gas and are ionized by photons from massive, hot stars in the central parsec. We attempt to constrain the emission mechanisms and physical properties of the ionized gas and dust of the mini-spiral region with the help of our multiwavelength data sets. Our observations were carried out at 1.3mm and 3mm with the mm interferometric array CARMA in California in March and April 2009, with the MIR instrument VISIR at ESO's VLT in June 2006, and the NIR Brγ with VLT NACO in August 2009. We present high resolution maps of the mini-spiral, and obtain a spectral index of 0.5±0.25 for Sgr A*, indicating an inverted synchrotron spectrum. We find electron densities within the range 0.8-1.5x10⁴cm^–3 for the mini-spiral from the radio continuum maps, along with a dust mass contribution of ∼0.25M_☉ from the MIR dust continuum, and extinctions ranging from 1.8-3 at 2.16µm in the Brγ line. We observe a mixture of negative and positive spectral indices in our 1.3mm and 3mm observations of the extended emission of the mini-spiral, which we interpret as evidence that there are a range of contributions to the thermal free-free emission by the ionized gas emission and by dust at 1.3mm.