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Mid-Infrared Observations of the Galactic Center Arc and the Sgr A East HII Region

Published online by Cambridge University Press:  23 September 2016

F. Yusef-Zadeh ,
C. M. Telesco  and
R. Decher
F. Yusef-Zadeh
Affiliation:
LASP, Goddard Space Flight Center and Northwestern University Space Science Laboratory, NASA/Marshall Space Flight Center
C. M. Telesco
Affiliation:
Space Science Laboratory, NASA/Marshall Space Flight Center
R. Decher
Affiliation:
Space Science Laboratory, NASA/Marshall Space Flight Center

Abstract

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We have used the 20-pixel IR camera to observe thermal IR emission from dust associated with the radio continuum Arc near the Galactic center and the cluster of HII regions in the immediate vicinity of Sgr A East. We detected strong 10μm emission from the eastern and western arched filaments (G0.1+0.08), from an unusual pistol-shaped structure known as G0.15–0.05 and from the brightest member of the Sgr A East HII region. Spatial maps of these features at 10μm with a resolution of 4.1″ × 4.2″ are presented and are compared with 5-GHz radio images. We find a general spatial correlation between the ionized gas and the dust distributions. The ratio of IR to radio flux densities is significantly different in the eastern and western arched filaments, which suggests that the source of heating has a softer spectrum along the eastern arched filaments. In addition, the ratio of IR to radio flux densities, which is typically ~10 in normal Galactic HII regions excited by O stars, is at least a factor of two higher than this value in almost all the sources we have observed. This suggests that additional mechanisms other than trapped Lyman α radiation should be present in heating the dust, e.g. stochastic heating of small dust grains by energetic particles associated with the nonthermal filaments.

Type
The Arc
Information
Symposium - International Astronomical Union , Volume 136: The Galactic Center , 1989 , pp. 287 - 292
Copyright
Copyright © Kluwer 1989 

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