150 GHz NOBA observations of the Galactic Center Arc

Wolfgang Reich1, Yoshiaki Sofue2, and Hiroshi Matsuo3


(1) Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69 D-53121 Bonn, Germany, E-mail(WR): wreich@mpifr-bonn.mpg.de,
(2) Institut of Astronomy, The University of Tokyo, Mitaka, Tokyo 181, Japan, E-mail(YS): sofue@mtk.ioa.s.u-tokyo.ac.jp,
(3) Nobeyama Radio Observatory, Minamimaki, Minamisaku, Nagano 384-13, Japan, E-mail(HM): matsuo@nrosv1.nro.nao.ac.jp

Paper: PASJ Vol. 52, No. 2, in press


Abstract:

We have used the seven beam 150 GHz bolometer NOBA installed at the Nobeyama 45-m telescope to map the central section of the Galactic Center Arc. In addition we mapped Sgr A, which shows Sgr A* and the thermal spiral structure. The results agree with previous mm-observations. South of the thermal "sickle" feature (G0.18-0.04) we observe three regions of enhanced emission along the Arc, which are located slightly offset relative to the most intense vertical filaments seen at low frequencies. This 150 GHz emission is observed at the apparent interacting areas of dense molecular material with the Arc. Another structure is seen south of the molecular cloud, where the Arc's vertical filaments apparently cross a weak filamentary structure running orthogonally in the direction of Sgr A. The 150 GHz results are unexpected in view of previous 32 GHz and 43 GHz results, which indicate a fading of the Arc towards higher frequencies. Cold dust can be ruled out as the origin of the 150 GHz emission. Synchrotron emission from quasi-monoenergetic electrons or an electron distribution with a low energy cut-off seems compatible with the available data. The coincidence of enhanced emission with regions of interacting molecular gas strongly suggests that high energetic electrons are accelerated in those places where the magnetic field is compressed and subsequently enter and illuminate the Arc.


Preprints available from the authors at p098wre@mpifr-bonn.mpg.de , or the raw TeX (no figures) if you click here.

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