GBT25A-069

A Polarization Study of the Sgr B Cloud in the Galactic Center

Abstract

Recent study has reported the detection of nonthermal radio emission from the infrared dark cloud (IRDC) associated with the envelope of the Sgr B complex on a scale of ~60 pc. A strong, spatial correlation between low-frequency (330-88 MHz) radio continuum emission and dense molecular gas combined with spectral index measurements indicate enhanced nonthermal emission. Additionally, 90, 150 and 220 GHz polarization measurements indicate evidence of a mixture dust and nonthermal polarized emission from cosmic-ray electrons at 90 GHz. We propose to measure polarized emission from Sgr B at 8 GHz, thus establishing the evidence for synchrotron emission from the cold and dense envelope of Sgr B. We intend to map 6'x6' region of the brightest region of the Sgr B cloud envelope at X-band to detect synchrotron polarized emission and to determine the geometry of the magnetic field field traced by synchrotron emission. Leptonic origin of the emission has also important implications in the origin of high energy emission such as the K$\alpha$ 6.4 keV line detected not only from Sgr B but also from dense clouds that make up the 200-pc Central Molecular Zone of the Galactic center.

Investigators

Name	Institution
Pedro Salas	Green Bank Observatory
Farhad Yusef-Zadeh *	Northwestern University
Richard Arendt	National Aeronautics and Space Administration
Mark Wardle	Macquarie University

* indicates the PI