Australia Telescope Compact Array Radio Continuum 1384 and 2368 Mhz Observations of Sagittarius B

Abstract

We present images of the Sagittarius (Sgr) B giant molecular cloud at 2368 and 1384 MHz obtained using new, multi-configuration Australia Telescope Compact Array (ATCA) observations. We have combined these observations with archival single-dish observations yielding images at resolutions of 47" by 14" and 27" by 8" at 1384 and 2368 MHz respectively. These observations were motivated by our theoretical work (Protheroe et al. 2008) 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 dominantly due to secondary electrons and positrons. We use polarization data to place 5-sigma upper limits on the level of polarized intensity from the Sgr B2 cloud of 3.5 and 3 mJy/beam at 1384 and 2368 MHz respectively. We also use the angular distribution of the total intensity of archival 330 MHz VLA and the total intensity and polarized emission of our new 1384 MHz 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.

7 pages, 4 figures, matches version published in the Astronomical Journal

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Cited by in corpus (10)

• The 1.28 GHz MeerKAT Galactic Center Mosaic
• Low energy cosmic rays
• 3 to 12 millimetre studies of dense gas towards the western rim of supernova remnant RX J1713.7-3946
• The physical and chemical structure of Sagittarius B2 -- V. Non-thermal emission in the envelope of Sgr B2
• The QUaD Galactic Plane Survey II: A Compact Source Catalog
• Spectrum of Relativistic and Subrelativistic Cosmic Rays in the 100 pc Central Region
• Probes of turbulent driving mechanisms in molecular clouds from fluctuations in synchrotron intensity
• Self-modulation of cosmic rays in molecular clouds: Imprints in the radio observations
• Prospects for Detection of Synchrotron Emission from Secondary Electrons and Positrons in Starless Cores: Application to G0.216+0.016
• Feedback between Sgr A and B : AGN-Starburst Connection in the Galactic Centre