10 research outputs found
Australia Telescope Compact Array Radio Continuum 1384 and 2368 Mhz Observations of Sagittarius B
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.Comment: 7 pages, 4 figures, matches version published in the Astronomical
Journa
Ultimate precision in cosmic-ray radio detection - The SKA
As of 2023, the low-frequency part of the Square Kilometre Array will go online in Australia. It will constitute the largest and most powerful low-frequency radio-astronomical observatory to date, and will facilitate a rich science programme in astronomy and astrophysics. With modest engineering changes, it will also be able to measure cosmic rays via the radio emission from extensive air showers. The extreme antenna density and the homogeneous coverage provided by more than 60,000 antennas within an area of one km 2 will push radio detection of cosmic rays in the energy range around 10 17 eV to ultimate precision, with superior capabilities in the reconstruction of arrival direction, energy, and an expected depth-of-shower-maximum resolution of < 10 g/cm 2
Serendipitous discovery of a dying Giant Radio Galaxy associated with NGC 1534, using the Murchison Widefield Array
This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society. © 2015 The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society.Recent observations with the Murchison Widefield Array at 185~MHz have serendipitously unveiled a heretofore unknown giant and relatively nearby () radio galaxy associated with NGC\,1534. The diffuse emission presented here is the first indication that NGC\,1534 is one of a rare class of objects (along with NGC\,5128 and NGC\,612) in which a galaxy with a prominent dust lane hosts radio emission on scales of 700\,kpc. We present details of the radio emission along with a detailed comparison with other radio galaxies with disks. NGC1534 is the lowest surface brightness radio galaxy known with an estimated scaled 1.4-GHz surface brightness of just 0.2\,mJy\,arcmin. The radio lobes have one of the steepest spectral indices yet observed: , and the core to lobe luminosity ratio is $Peer reviewe
Radio Frequency Interference Mitigation Strategies: Summary of the E. & F. White Conference held in Sydney, Australia, December 1999
The host galaxies and progenitors of fast radio bursts localized with the Australian square kilometre Array Pathfinder
The Australian SKA Pathfinder (ASKAP) telescope has started to localize fast radio bursts (FRBs) to arcsecond accuracy from the detection of a single pulse, allowing their host galaxies to be reliably identified. We discuss the global properties of the host galaxies of the first four FRBs localized by ASKAP, which lie in the redshift range 0.11 z < 0.48. All four are massive galaxies (log(M-*/M) similar to 9.4-10.4) with modest star formation rates of up to 2 M yr(-1)-very different to the host galaxy of the first repeating FRB 121102, which is a dwarf galaxy with a high specific star formation rate. The FRBs localized by ASKAP typically lie in the outskirts of their host galaxies, which appears to rule out FRB progenitor models that invoke active galactic nuclei or free-floating cosmic strings. The stellar population seen in these host galaxies also disfavors models in which all FRBs arise from young magnetars produced by superluminous supernovae, as proposed for the progenitor of FRB 121102. A range of other progenitor models (including compact-object mergers and magnetars arising from normal core-collapse supernovae) remain plausible.European Southern Observatory
0102.A-0450(A)
0103.A-0101(B)
Australian Research Council
DP180100857
Australian Research Council
FT150100415
Australian Research Council
FL150100148
CE170100004
PUCV/VRIEA project
039.395/2019
National Science Foundation (NSF)
AST-1911140
Australian Government
Australian Government
Department of Industry, Innovation and Science
Government of Western Australia
Science and Industry Endowment Fund
W.M. Keck Foundation
Las Campanas Observatory, Chile
CN2019A-36
LCOGT network
CN2019A-39/CLN2019A-002
CN2019B-93/CLN2019B-001
Gemini Observatory
GS-2018B-Q-133
UCh/VID-ENL18/18
FONDECYT 119123