The Sgr A^* Stellar Cluster:, New NIR Imaging and Spectroscopy

Andreas Eckart & Thomas Ott & Reinhard Genzel


(1) Max-Planck-Institut für extraterrestrische Physik, Giessenbachstr., D-85740 Garching

Paper: Accepted by A and A

EPrint Server: astro-ph/9911011


Abstract:

We report preliminary results based on new near-infrared observations of the central stellar cluster of our Galaxy conducted with the infrared spectrometer ISAAC at the ESO VLT UT1 and the MPE speckle camera SHARP at the ESO NTT. We obtained lambda / DELTA lambda >= 3000 K-band spectroscopy of the 2.058 micron He I, 2.165 micron Br gamma emission lines, and 2.29 micron CO bandhead absorption line. These data demonstrate clearly that there is no strong CO bandhead absorption originating in the northern part (S1/S2 area) of the central stellar cluster at the position of Sgr A^*. This makes it likely that these K~14.5 stars are O9 - B0.5 stars with masses of 15 to 20 M_o. Weaker CO bandhead absorption in the southern part of the cluster (S10/S11 area) could be due to contributions from neighbouring stars. We also report the detection of Br gamma line emission at the position of the central stellar cluster which could be associated with the 'mini-spiral' rather than with the Sgr A^* cluster itself. At the NTT we obtained another epoch epoch of proper motion measurments. The changes of source positions are consistent with the proper motion velocities derived from earlier epochs.


Preprints available from the authors at ott@ibm-s-1.mpe-garching.MPG.DE , or the raw TeX (no figures) if you click here.

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