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We report 3He and 4He concentrations in 57 sediment samples from the southeast Indian Ocean where 60Fe excesses were previously identified in a subset of the same samples (Wallner et al., 2016). The coupled 60Fe-3He data allow further evaluation of two competing hypotheses: (1) a nearby supernova (SN) showered Earth with exotic radionuclides such as 60Fe during the last 3 million years, or (2) 60Fe in terrestrial archives was generated by reactions of galactic cosmic rays (GCRs) on micrometeorite grains that were irradiated for hundreds of millions of years in the interstellar medium, where 3He production by GCRs is larger than the solar wind 3He flux. Piston core ELT49-53 sediments show no correlation between 3He and 60Fe, and sedimentary 3He appears to be dominated by the presence of interplanetary dust particles (IDPs). Because 3He is not supplied in significant amounts by SN ejecta, the absence of a 3He-60Fe correlation provides additional, although circumstantial evidence for the supernova hypothesis. Large uncertainties in the relatively small number of sediment 60Fe measurements currently limit a firmer conclusion. The extraterrestrial 3He accumulation rate in ELT49-53 from 3.2 to 1.7 Ma was 0.88 ± 0.26 × 10−12 cm3 STP/g/kyr, similar to IDP 3He flux estimates from previous sedimentary and ice core records that span both shorter and longer time scales. 4He and 60Fe accumulation rates during this time interval were 0.11 ± 0.04 × 10−6 cm3 STP/cm2/kyr and 1.9 ± 0.5 × 104 atoms/cm2/kyr. Bulk sediment [4He] is strongly anti-correlated with sediment CaCO 3 content, evidence for modulation of the terrigenous and cosmic sedimentary fractions primarily by changes in biogenic carbonate deposition. Although the dominant terrigenous source has not been uniquely identified at the Indian Ocean deposition site, it resembles eolian material from the continental interior of Australia, and shows a narrow range of 3He/4He (from 2 to 4 × 10−8, 0.015–0.030 R A) over the last ∼3 Myrs. [ABSTRACT FROM AUTHOR]

We present a detailed radio-continuum study on Australia Telescope Compact Array (ATCA) observations of Large Magellanic Cloud (LMC) supernova remnant (SNR), MCSNR J0536-7038. This Type Ia SNR follows a horseshoe morphology, with a size 32 pc × 32 pc (1-pc uncertainty in each direction). It exhibits a radio spectrum α=−0.52±0.07 between λ=73 and 6 cm. We report detections of regions showing moderately high fractional polarisation at 6 cm, with a peak value of 71±25 % and a mean fractional polarisation of 35±8 %. We also estimate an average rotation measure across the remnant of -237 rad m. The intrinsic magnetic field appears to be uniformly distributed, extending in the direction of the two brightened limbs of the remnant. [ABSTRACT FROM AUTHOR]

Midcourse Space eXperiment and Infrared Astronomical Satellite colour diagnostics as well as OH maser profile characteristics were used to select a sample of post-asymptotic giant branch (pAGB) candidates for a radio continuum detection experiment with the Australia Telescope Compact Array. Seven out of 28 sources, six of which are new detections, show a continuum. A planetary nebula serendipitously detected in the field of an undetected pAGB candidate also reveals radio continuum. The radio continuum properties of these eight sources are described. Almost half have non-thermal emission.dusty modelling of the infrared spectral energy distributions (SEDs) of the three strongest detections reveals that they all have central stars with temperatures substantially lower than that required for significant photoionization, leading us to infer that the radio continuum has arisen from wind–shock interactions. This hypothesis is consistent with the detection of non-thermal radio emission in one of these three objects. [ABSTRACT FROM AUTHOR]

We present 11 spectra from 12 candidate radio sources co-identified with known planetary nebulae (PNe) in the Large Magellanic Cloud (LMC). Originally found in Australia Telescope Compact Array (ATCA) LMC surveys at 1.4, 4.8 and 8.64 GHz and confirmed by new high resolution ATCA images at 6 and 3 cm (400/200), these complement data recently presented for candidate radio PNe in the Small Magellanic Cloud (SMC). Their spectra were obtained using the Radclifie 1.9-meter telescope in Sutherland (South Africa). All of the optical PNe and radio candidates are within 200 and may represent a population of selected radio bright sample only. Nebular ionized masses of these objects are estimated to be as high as 1.8 Mʘ, supporting the idea that massive PNe progenitor central stars lose much of their mass in the asymptotic giant branch (AGB) phase or prior. We also identify a sub-political. [ABSTRACT FROM AUTHOR]

We have used the Australia Telescope Compact Array (ATCA) and the Swedish–ESO Submillimetre Telescope (SEST) to map the large-scale atomic and molecular gas in the nearby (4 Mpc) Circinus galaxy. The ATCA H i mosaic of Circinus exhibits the warps in position angle and inclination revealed in the single-pointing image of Jones et al., both of which appear to settle beyond the inner 30 kpc which was previously imaged. The molecular gas has been mapped in both the CO and transitions down to a column density of (3σ), where we derive a total molecular gas mass of . Within a radius of 3 kpc, i.e. where CO was clearly detected, the molecular fraction climbs steeply from ≈ 0.7 to unity (where , cf. ) with proximity to the nucleus. Our H i mosaic gives an atomic gas mass of , which is 70 per cent of the fully mapped single dish value. Combining the atomic and molecular gas masses gives a total gas mass of , cf. the total dynamical mass of within the inner 50 kpc of our mosaiced image. The total neutral gas mass to dynamical mass ratio is therefore 3 per cent, consistent with the SAS3 (Third Small Astronomy Satellite) classification of Circinus. The high (molecular) gas mass fraction of per cent found by Curran et al., only occurs close to the central ≈ 0.5 kpc and falls to ≲10 per cent within and outwith this region, allaying previous concerns regarding the validity of applying the Galactic conversion ratio to Circinus. The rotation curve, as traced by both the H i and CO, exhibits a steep dip at ≈ 1 kpc, the edge of the atomic/molecular ring, within which the starburst is occurring. We find the atomic and molecular gases to trace different kinematical features and believe that the fastest part of the subkpc ring consists overwhelmingly of molecular gas. Beyond the inner kpc, the velocity climbs to settle into a solid body rotation of at . Most of the starlight emanates from within this radius and so much of the dynamical mass, which remains climbing to the limit of our data , must be due to the dark matter halo. [ABSTRACT FROM AUTHOR]