High angular resolution spectroscopic and polarimetric imaging of the galactic center in the near-infrared

ANDREAS ECKART, REINHARD GENZEL, RAINER HOFMANN, BRUCE J. SAMS, LOWELL E. TACCONI-GARMAN

Max-Planck-Institut für extraterrestrische Physik, Postfach 1603, D-85740 Garching, Germany

THE ASTROPHYSICAL JOURNAL, 445:L23-L26, 1995 May 20


ABSTRACT

We present improved 0.15" resolution K-band (2.2 µm) maps of the central 0.5 pc of the Galaxy as well as, for the first time, 0.2" J-band (1.25 µm) images, 0.2" K-band polarimetry, and 0.4" images in the 2.058 µm He I emission and 2.29 µm CO band head absorption features. The new K-band maps reach K magnitudes of about 16 and resolve the previously found object at the position of the radio source Sgr A*(R) into a small cluster of compact sources. With one exception, their polarizations are similar to other sources in its vicinity and thus are probably caused by antisotropic foreground dust extinction in the Galactic plane. The Sgr A*(IR) complex does not exhibit any significant flux density variations at 2.2 µm on timescales of minutes or years. We therefore interpret Sgr A*(IR) as a small local clustering of luminous stars (MK ~ -3) near/at the position of the compact radio source. The central IRS 16 complex and the bright source IRS 13 are dominated by bright luminous He I stars and confirm the cluster of about a dozen He I stars found by Krabbe et al. (1991). There are also a dozen sources with K less than or equal to 12.5 exhibiting CO band head absorption within a radius of 10" of Sgr A*(IR). The drop in CO band head strength found by Sellgren et al. (1990) thus is most likely not caused by the disappearance of CO sources but by the additional presence of the bright early-type stars.

Subject headings: Galaxy: center - galaxies: nuclei - infrared: stars


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