Jones, David I. and Crocker, Roland M. and Ott, Jürgen and Protheroe, Raymond J. and Ekers, Ron D. (2011) Australia Telescope Compact Array Radio Continuum 1384 and 2368 MHz Observations of Sagittarius B. Astronomical Journal, 141 (3). Art. No. 82. ISSN 0004-6256 http://resolver.caltech.edu/CaltechAUTHORS:20110317-130412061
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We present images of the Sagittarius (Sgr) B giant molecular cloud at 1384 and 2368 MHz obtained using new, multi-configuration Australia Telescope Compact Array observations. We have combined these observations with archival single-dish observations yielding images at resolutions of 47" × 14" and 27" × 8" at 1384 and 2368 MHz, respectively. These observations were motivated by our theoretical work indicating the possibility that synchrotron emission from secondary electrons and positrons created in hadronic cosmic ray (CR) collisions with the ambient matter of the Sgr B2 cloud could provide a detectable (and possibly linearly polarized) non-thermal radio signal. We find that the only detectable non-thermal emission from the Sgr B region is from a strong source to the south of Sgr B2, which we label Sgr B2 Southern Complex (SC). We find Sgr B2(SC) integrated flux densities of 1.2 ± 0.2 Jy at 1384 MHz and 0.7 ± 0.1 Jy at 2368 MHz for a source of FWHM size at 1384 MHz of ~54". Despite its non-thermal nature, the synchrotron emission from this source is unlikely to be dominated due to secondary electrons and positrons. Failing to find clear evidence of non-thermal emission due to secondary electrons and positrons, we use polarization data to place 5σ upper limits on the level of polarized intensity from the Sgr B2 cloud of 3.5 and 3 mJy beam^(−1) at 1384 and 2368 MHz, respectively. We also use the angular distribution of the total intensity of archival 330 MHz Very Large Array and the total intensity and polarized emission of our new 1384 and 2368 MHz data to constrain the diffusion coefficient for transport of the parent hadronic CRs into the dense core of Sgr B2 to be no larger than about 1% of that in the Galactic disk. Finally, we have also used the data to perform a spectral and morphological study of the features of the Sgr B cloud and compare and contrast these to previous studies.
|Additional Information:||© 2011 American Astronomical Society. Received 2010 February 17; accepted 2010 November 6; published 2011 February 4. The authors thank the anonymous referee for their comments which greatly improved the manuscript. D.I.J. thanks Jasmina Lazendíc for help during the preparation of the manuscript. The Australia Telescope Compact Array is part of the Australia Telescope which is funded by the Commonwealth of Australia for operation as a National Facility managed by CSIRO. This work has made use of NASA’s Astrophysics Data System (ADS) abstract service. This research has made use of the SIMBAD database, operated at CDS, Strasbourg, France. This research was supported under the Australian Research Council’s Discovery Project funding scheme (project number DP0559991). While this research was conducted, Professor R. D. Ekers was the recipient of an Australian Research Council Federation Fellowship (project number FF0345330), J. Ott was the recipient of a Jansky Fellow of the National Radio Astronomy Observatory, and R. M. Crocker was the recipient of the inaugural J. L. William Fellowship.|
|Subject Keywords:||cosmic rays; Galaxy: center; ISM: clouds; radiation mechanisms: non-thermal; radio continuum: ISM|
|Classification Code:||PACS: 98.38.Dq; 95.30.Gv; 98.35.Hj; 95.30.Cq; 95.85.gh; 98.70.Sa|
|Official Citation:||Australia Telescope Compact Array Radio Continuum 1384 and 2368 MHz Observations of Sagittarius B David I. Jones, Roland M. Crocker, Jürgen Ott, Raymond J. Protheroe and Ron D. Ekers doi: 10.1088/0004-6256/141/3/82|
|Usage Policy:||No commercial reproduction, distribution, display or performance rights in this work are provided.|
|Deposited By:||Ruth Sustaita|
|Deposited On:||18 Mar 2011 15:15|
|Last Modified:||26 Dec 2012 13:05|
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