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We report the first short term velocity centroid (VC) periodicity derived from SiO maser emission. L2 Puppis, a semi-regular AGB star, was observed using the Mopra radio telescope of the Australia Telescope National Facility in the SiO v = 1, J = 1-0 and v = 1, J = 2-1 transitions. It exhibits a 139 day period in its SiO maser VC based on a period folding analysis and a Lomb Scargle analysis. L2 Pup's SiO maser emission has an unusually large velocity range and an unusual three-peaked spectrum. To create the change in VC the entire spectrum does not shift in velocity, but changes in the relative emission of the peaks generate the variation. The changes in the VC may be due to differential illumination, an asymmetric circumstellar distribution of material, or a mixture of causes. The unusual velocity structure, similar to that observed in Orion source 1, may be due to revolution of the circumstellar material or asymmetries in the circumstellar environment. [ABSTRACT FROM AUTHOR]

Context. The Large Magellanic Cloud (LMC) is rich in supernova remnants (SNRs), which can be investigated in detail with radio, optical, and X-ray observations. SNR-J0453-6829 is an X-ray and radio-bright remnant in the LMC, within which previous studies revealed the presence of a pulsar wind nebula (PWN), making it one of the most interesting SNRs in the Local Group of galaxies. Aims. We study the emission of SNR-J0453-6829 to improve our understanding of its morphology, spectrum, and thus the emission mechanisms in the shell and the PWN of the remnant. Methods. We obtained new radio data with the Australia Telescope Compact Array and analysed archival XMM-Newton observations of SNR-J0453-6829. We studied the morphology of SNR-J0453-6829 from radio, optical, and X-ray images and investigated the energy spectra in the different parts of the remnant. Results. Our radio results confirm that this LMC SNR hosts a typical PWN. The prominent central core of the PWN exhibits a radio spectral index αCore of −0.04 ± 0.04, while in the rest of the SNR shell the spectral slope is somewhat steeper with αShell = −0.43- ± -0.01. We detect regions with a mean polarisation of P ≅ (12 ± 4)% at 6 cm and (9 ± 2)% at 3 cm. The full remnant is of roughly circular shape with dimensions of (31 ± 1) pc- × (29 ± 1) pc. The spectral analysis of the XMM-Newton EPIC and RGS spectra allowed us to derive physical parameters for the SNR. Somewhat depending on the spectral model, we obtain for the remnant a shock temperature of around 0.2 keV and estimate the dynamical age to 12-000-15-000 years. Using a Sedov model we further derive an electron density in the X-ray emitting material of 1.56-cm-3, typical for LMC remnants, a large swept-up mass of 830 M⊙, and an explosion energy of 7.6 × 1050 erg. These parameters indicate a well evolved SNR with an X-ray spectrum dominated by emission from the swept-up material. [ABSTRACT FROM AUTHOR]

Context. The Large Magellanic Cloud (LMC) is rich in supernova remnants (SNRs), which can be investigated in detail with radio, optical, and X-ray observations. SNRJ0453-6829 is an X-ray and radio-bright remnant in the LMC, within which previous studies revealed the presence of a pulsar wind nebula (PWN), making it one of the most interesting SNRs in the Local Group of galaxies. Aims. We study the emission of SNRJ0453-6829 to improve our understanding of its morphology, spectrum, and thus the emission mechanisms in the shell and the PWN of the remnant. Methods. We obtained new radio data with the Australia Telescope Compact Array and analysed archival XMM-Newton observations of SNRJ0453-6829. We studied the morphology of SNRJ0453-6829 from radio, optical, and X-ray images and investigated the energy spectra in the different parts of the remnant. Results. Our radio results confirm that this LMC SNR hosts a typical PWN. The prominent central core of the PWN exhibits a radio spectral index αCore of -0.04 ± 0.04, while in the rest of the SNR shell the spectral slope is somewhat steeper with αShell = -0.43 ± 0.01. We detect regions with a mean polarisation of P (12 ± 4)% at 6 cm and (9 ± 2)% at 3 cm. The full remnant is of roughly circular shape with dimensions of (31±1) pc × (29±1) pc. The spectral analysis of the XMM-Newton EPIC and RGS spectra allowed us to derive physical parameters for the SNR. Somewhat depending on the spectral model, we obtain for the remnant a shock temperature of around 0.2 keV and estimate the dynamical age to 12 000-15 000 years. Using a Sedov model we further derive an electron density in the X-ray emitting material of 1.56 cm-3, typical for LMC remnants, a large swept-up mass of 830 M☉, and an explosion energy of 7.6 × 1050 erg. These parameters indicate a well evolved SNR with an X-ray spectrum dominated by emission from the swept-up material. [ABSTRACT FROM AUTHOR]

ABSTRACT We have mapped 20 spectral lines in the Central Molecular Zone (CMZ) around the Galactic Centre, emitting from 85.3 to 93.3 GHz. This work used the 22-m Mopra radio telescope in Australia, equipped with the 8-GHz bandwidth University of New South Wales-Mopra Spectrometer (UNSW-MOPS) digital filter bank, obtaining ∼2 km s−1 spectral and ∼40 arcsec spatial resolution. The lines measured include emission from the c-C3H2, CH3CCH, HOCO+, SO, H13CN, H13CO+, SO, H13NC, C2H, HNCO, HCN, HCO+, HNC, HC3N, 13CS and N2H+ molecules. The area covered is Galactic longitude −07 to 18 and latitude −03 to 02, including the bright dust cores around Sgr A, Sgr B2, Sgr C and G1.6−0.025. We present images from this study and conduct a principal component analysis on the integrated emission from the brightest eight lines. This is dominated by the first component, showing that the large-scale distribution of all molecules is very similar. We examine the line ratios and optical depths in selected apertures around the bright dust cores, as well as for the complete mapped region of the CMZ. We highlight the behaviour of the bright HCN, HNC and HCO+ line emission, together with that from the 13C isotopologues of these species, and compare the behaviour with that found in extragalactic sources where the emission is unresolved spatially. We also find that the isotopologue line ratios (e.g. HCO+/H13CO+) rise significantly with increasing redshifted velocity in some locations. Line luminosities are also calculated and compared to that of CO, as well as to line luminosities determined for external galaxies. [ABSTRACT FROM AUTHOR]

This paper presents a study of the envelope of the young stellar object (YSO) GGD30IR. What distinguishes this from most other YSOs is the elongated absorption feature seen in silhouette against the background emission in the Spitzer Galactic Legacy Infrared Midplane Survey Extraordinaire 8 μm Infrared Array Camera image of the region. The size and the symmetrical placement of GGD30IR in the centre of this feature suggest that it is an extended envelope, perhaps the remnant of the collapse of the GGD30 core. We have used the extinction in the envelope measured from (i) the reduction in the 8 μm background intensity and (ii) field star colour excesses, to estimate the envelope mass, obtaining values of 0.6 ± 0.2 and , respectively. To investigate the envelope further, we have obtained Australia Telescope Compact Array 3 mm continuum and HCO+ line observations of the region. The continuum emission at 3 mm arises from both a compact (unresolved; ≤730 au) core embedded in an extended envelope ∼18 000 au × 38 000 au in extent. We estimate the core mass to be 0.11 ± 0.02 . The HCO+ emission is extended in a direction perpendicular to the long axis of the envelope, suggesting it comes from an outflow. The spectral energy distribution (SED) provides a 2–24 μm spectral index, α= 1.0, which places GGD30IR in the Class I YSO category. Integrating the SED provides a luminosity of . [ABSTRACT FROM AUTHOR]

Time variations of lightning activity in the three main tropical thunderstorm centers located in the Maritime Continent (Pakistan, India, Southeast Asia, Indonesia, and Australia), Africa, and the Americas are analyzed using a lightning activity index IRS, which is calculated from the resonances of magnetic field in the extremely low frequency range—the Schumann resonances—which were observed at Hylaty station (Poland) in the time interval July 2005–May 2006. Power spectrum analysis of the IRS series is carried out for this time interval. The annual and semiannual variations are shown in all of the series together with the following characteristic periodicities: 45 (Madden–Julian oscillation), 17.6, 13.5, and 4.8 days, seen mainly in the series describing the lightning activity of the Maritime Continent. In addition, maps of the dynamical power spectrum are constructed. They present variability both in the values of characteristic periods 26–30, 17–22, 12–14, 9–10, and 5–7 days and in their duration. During the studied time interval, according to these indices, the African center was the most active, whereas the American and Maritime Continent centers showed a similar level of activity. The largest differences among the centers were observed in the summer months in the Northern Hemisphere. [ABSTRACT FROM AUTHOR]

Gigahertz-peaked spectrum (GPS) radio sources are thought to be young objects which later evolve into Fanaro–Riley type I (FR I) and FR II radio galaxies. We have used the Australia Telescope 20 GHz (AT20G) survey catalogue to select a uniform sample of GPS sources with spectral peaks above 5 GHz, which should represent the youngest members of this class. In this paper, we present e-VLBI observations of 10 such objects which are associated with nearby galaxies and so represent a new population of local, low-power GPS sources. Our e-VLBI observations were carried out at 4.8 GHz with the Australia Telescope Long Baseline Array (LBA) using a real-time software correlator. All 10 sources were detected, and were unresolved on scales of ∼100 mas, implying that they are typically less than 100 pc in linear size. [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) at 95 GHz to carry out continuum observations of 130 extragalactic radio sources selected from the Australia Telescope 20 GHz (AT20G) survey. We use a triple-correlation method to measure simultaneous 20- and 95-GHz flux densities for these objects, and over 90 per cent of our target sources are detected at 95 GHz. We demonstrate that the ATCA can robustly measure 95-GHz flux densities with an accuracy of ∼10 per cent in a few minutes for sources stronger than about 50 mJy. We measure the distribution of radio spectral indices in a flux-limited sample of extragalactic sources, and show that the median 20–95 GHz spectral index does not vary significantly with flux density for . This finding allows us to estimate the extragalactic radio source counts at 95 GHz by combining our observed 20–95 GHz spectral-index distribution with the accurate 20-GHz source counts measured in the AT20G survey. Our derived 95-GHz source counts at flux densities above 80 mJy are significantly lower than those found by several previous studies. The main reason is that most radio sources with flat or rising spectra in the frequency range 5–20 GHz show a spectral turnover between 20 and 95 GHz. As a result, there are fewer 95-GHz sources (by almost a factor of 2 at 0.1 Jy) than would be predicted on the basis of extrapolation from the source populations seen in lower-frequency surveys. We also derive the predicted confusion noise in cosmic microwave background surveys at 95 GHz and find a value 20–30 per cent lower than previous estimates. The 95-GHz source population at the flux levels probed by this study is dominated by quasi-stellar objects with a median redshift . We find a correlation between optical magnitude and 95-GHz flux density which suggests that many of the brightest 95-GHz sources may be relativistically beamed, with both the optical and millimetre continuum significantly brightened by Doppler boosting. [ABSTRACT FROM AUTHOR]

The Australia Telescope 20-GHz (AT20G) Survey is a blind survey of the whole southern sky at 20 GHz (with follow-up observations at 4.8 and 8.6 GHz) carried out with the Australia Telescope Compact Array from 2004 to 2007. The Bright Source Sample (BSS) is a complete flux-limited subsample of the AT20G Survey catalogue comprising 320 extragalactic ) radio sources south of with Jy. Of these, 218 have near simultaneous observations at 8 and 5 GHz. In this paper we present an analysis of radio spectral properties in total intensity and polarization, size, optical identifications and redshift distribution of the BSS sources. The analysis of the spectral behaviour shows spectral curvature in most sources with spectral steepening that increases at higher frequencies (the median spectral index α, assuming , decreases from between 4.8 and 8.6 GHz to between 8.6 and 20 GHz), even if the sample is dominated by flat spectra sources (85 per cent of the sample has . The almost simultaneous spectra in total intensity and polarization allowed us a comparison of the polarized and total intensity spectra: polarized fraction slightly increases with frequency, but the shapes of the spectra have little correlation. Optical identifications provided an estimation of redshift for 186 sources with a median value of 1.20 and 0.13, respectively, for QSO and galaxies. [ABSTRACT FROM AUTHOR]

The second-order, three-dimensional, finite-depth wave theory is here used to investigate the statistical properties of the surface elevation and wave crests of field data from Lake George, Australia. A direct comparison of experimental and numerical data shows that, as long as the nonlinearity is small, the second-order model describes the statistical properties of field data very accurately. By low-pass filtering the Lake George time series, there is evidence that some energetic wave groups are accompanied by a setup instead of a setdown. A numerical study of the coupling coefficient of the second-order model reveals that such an experimental result is consistent with the second-order theory, provided directional spreading is included in the wave spectrum. In particular, the coupling coefficient of the second-order difference contribution predicts a setup as a result of the interaction of two waves with the same frequency but with different directions. This result is also confirmed by numerical simulations. Bispectral analysis, furthermore, indicates that this setup is a statistically significant feature of the observed wave records. [ABSTRACT FROM AUTHOR]

We present results of polarization observations at 1.4 GHz of the two fields imaged by the DASI experiment ( and , respectively). Data were taken with the Australia Telescope Compact Array with 3.4-arcmin resolution and ∼0.18-mJy beam−1 sensitivity. The emission is dominated by point sources, and we do not find evidence for diffuse synchrotron radiation even after source subtraction. This allows to estimate an upper limit of the diffuse polarized emission. The extrapolation to 30 GHz suggests that the synchrotron radiation is lower than the polarized signal measured by the DASI experiment by at least two orders of magnitude. This further supports the conclusions drawn by the DASI team itself about the negligible Galactic foreground contamination in their data set, improving by a factor of ∼5 the upper limit estimated by Leitch et al. The dominant point-source emission allows us to estimate the contamination of the cosmic microwave background (CMB) by extragalactic foregrounds. We computed the power spectrum of their contribution, and its extrapolation to 30 GHz provides a framework where the CMB signal should dominate. However, our results do not match the conclusions of the DASI team about the negligibility of point-source contamination, suggesting taking into account a source subtraction from the DASI data. [ABSTRACT FROM AUTHOR]

In this study, independent classifications of Landsat Thematic Mapper imagery and Jet Propulsion Laboratory AirSAR were combined to create an integrated classification of pasture and other vegetation types for a study area in the agricultural zone of Western Australia. The resulting classification combines greenness and brightness information from optical data with structure and water content information from synthetic aperture radar (SAR). Field observations of vegetation type, botanical composition, ground cover percentage, wet and dry biomass, canopy height, and soil water content were collected at 34 sites representing a range of pastures, browse shrubs, and crops. An unsupervised version of the Complex Wishart classification procedure, based on preserving scattering characteristics from the Freeman and Durden backscatter decomposition, was applied to the C-, L-, and P-band polarimetric SAR data. The optical classification was carried out using a principle component analysis on the green, red, and near-infrared bands and clustering on the basis of a class centroid distance measure and knowledge of ground targets. These two classification results were then fused together. Assessment of a confusion matrix using the individual sites showed that identification of more uniform, dense, and structurally distinct canopies was better than that of more diverse, sparse, and structurally ambiguous canopies, as the former were better represented by the canopy height attribute used in the SAR classification component. The optical classification enabled correction of SAR misclassification of vegetation due to surface roughness and soil moisture effects, or similar backscatter responses from herbaceous or arboreal canopies. The results show that simplification of vegetation into groups based upon properties with sensitive responses in both the optical and SAR domains, and combination of separate SAR and optical classifications, has potential for improving classification of diverse and heterogeneous herbaceous and browse cover in grazing lands. However, collection of ground calibration data must be at an appropriate spatial scale and include canopy and surface measurements directly related to backscatter mechanisms and spectral sensitivity. [ABSTRACT FROM AUTHOR]