Australia telescope compact array radio continuum 1384 and 2368 MHz observations of Sagittarius B

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dc.contributor.authorJones, D.
dc.contributor.authorCrocker, R.
dc.contributor.authorOtt, J.
dc.contributor.authorProtheroe, R.
dc.contributor.authorEkers, R.
dc.date.issued2011
dc.description.abstractWe 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 mJybeam–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.
dc.description.statementofresponsibilityDavid I. Jones, Roland M. Crocker, Jürgen Ott, Raymond J. Protheroe and Ron D. Ekers
dc.identifier.citationThe Astronomical Journal, 2011; 141(3):1-7
dc.identifier.doi10.1088/0004-6256/141/3/82
dc.identifier.issn0004-6256
dc.identifier.issn1538-3881
dc.identifier.urihttp://hdl.handle.net/2440/69988
dc.language.isoen
dc.publisherUniv Chicago Press
dc.relation.granthttp://purl.org/au-research/grants/arc/DP0559991
dc.relation.granthttp://purl.org/au-research/grants/arc/DP0559991
dc.relation.granthttp://purl.org/au-research/grants/arc/FF0345330
dc.rightsCopyright 2011. The American Astronomical Society. All rights reserved.
dc.source.urihttps://doi.org/10.1088/0004-6256/141/3/82
dc.subjectcosmic rays
dc.subjectGalaxy: center
dc.subjectISM: clouds
dc.subjectradiation mechanisms
dc.subjectnon-thermal
dc.subjectradio continuum:ISM
dc.titleAustralia telescope compact array radio continuum 1384 and 2368 MHz observations of Sagittarius B
dc.typeJournal article
pubs.publication-statusPublished

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