Investigating the high-frequency spectral features of SNRs Tycho, W44 and IC443 with the Sardinia Radio Telescope

The main characteristics in the radio continuum spectra of Supernova Remnants (SNRs) result from simple synchrotron emission. In addition, electron acceleration mechanisms can shape the spectra in specific ways, especially at high radio frequencies. These features are connected to the age and the peculiar conditions of the local interstellar medium interacting with the SNR. Whereas the bulk radio emission is expected at up to $20-50$ GHz, sensitive high-resolution images of SNRs above 10 GHz are lacking and are not easily achievable, especially in the confused regions of the Galactic Plane. In the framework of the early science observations with the Sardinia Radio Telescope in February-March 2016, we obtained high-resolution images of SNRs Tycho, W44 and IC443 that provided accurate integrated flux density measurements at 21.4 GHz: 8.8 $\pm$ 0.9 Jy for Tycho, 25 $\pm$ 3 Jy for W44 and 66 $\pm$ 7 Jy for IC443. We coupled the SRT measurements with radio data available in the literature in order to characterise the integrated and spatially-resolved spectra of these SNRs, and to find significant frequency- and region-dependent spectral slope variations. For the first time, we provide direct evidence of a spectral break in the radio spectral energy distribution of W44 at an exponential cutoff frequency of 15 $\pm$ 2 GHz. This result constrains the maximum energy of the accelerated electrons in the range $6-13$ GeV, in agreement with predictions indirectly derived from AGILE and \textit{Fermi}-LAT gamma-ray observations. With regard to IC443, our results confirm the noticeable presence of a bump in the integrated spectrum around $20-70$ GHz that could result from a spinning dust emission mechanism.Comment: 12 pages, 9 figure

Developing an effective conservation and sustainable use economy: two Arnhem Land case studies<br />

SummaryThis is the final report for the research project &lsquo;Developing an effective conservation and sustainable use economy in Arnhem Land: Options for payment for environmental services&rsquo;. The research was undertaken at the Centre for Aboriginal Economic Policy Research (CAEPR) at the Australian National University (ANU). The Tropical Rivers and Coastal Knowledge (TRaCK) research hub funded the research. This report provides a preliminary assessment of the management needs and costs for two Indigenous Protected Areas (IPAs) in Arnhem Land, as well as a preliminary cost-benefit analysis (CBA) of the social benefits and costs associated with the management of the protected areas. The project commenced in July 2009 and was completed in March 2011.This report is aimed at helping decision-makers in communities, businesses, nongovernment organisations and government agencies consider payment for environmental services alongside continued public funding to support economic development in remote Indigenous communities. Crucially, this report highlights the need for better information and alternative economic perspectives in relation to the capacity of payment for environmental services to support the regional economy of Arnhem Land. This information is critical to addressing both opportunities for and barriers to the development of an effective conservation and sustainable use economy in this region and beyond.The research was carried out in collaboration with two Indigenous Ranger groups in Arnhem Land, the Djelk Rangers (Bawinanga Aboriginal Corporation) in Maningrida and the Dhimurru Rangers (Dhimurru Aboriginal Corporation) in Nhulunbuy. The two groups manage the Djelk IPA and the Dhimurru IPA respectively. The Djelk IPA was declared in 2009. It extends over 6,732 km2 stretching from the Central Arnhem Plateau to the Arafura Sea in the Arnhem Coast sub-bioregion ARC-2. The Djelk IPA has outstanding environmental and cultural values for the diversity of its landscapes and languages, and the wealth of community assemblages and species. The Dhimurru IPA was established in 2000. It covers around 920 km2 of land and 90 km2 of adjacent marine areas in the Gove Peninsula. The IPA contains areas of important cultural and environmental values, hosting a significant representation of Australia\u27s Arnhem Coast sub-bioregion ARC-3. Both IPA&rsquo;s are generally considered to be in near pristine condition.The two IPAs face quite different environmental management problems. The Djelk Rangers&rsquo; priorities focus on land and sea management including fire, weed and feral animal control and coastal surveillance. Among the most important issues for the Dhimurru IPA is managing the growing demand for the recreational uses of its environmental and cultural resources. Recreational activities could damage sensitive ecological systems, spread weeds and invasive ants through vehicles movement, disturb native flora and fauna, and damage cultural and sacred sites. The bauxite mine and processing plant adjacent to the Dhimurru IPA also have a serious impact on the integrity of the natural environment and cultural landscape.Both the Djelk and the Dhimurru rangers finance their management activities mainly through public funding. Djelk&rsquo;s revenues are split between government grants (78%) and fee-for-service earnings (22%). The Djelk Rangers use these finances to employ over 35 Indigenous rangers as well as to cover the operational costs of a range of activities including weed and feral animal control, fire management, and coastal patrols. Four activities&mdash;weed control, fire management, customs patrols, and marine debris patrols&mdash; generate 85 per cent of Djelk&rsquo;s total expenditure. The major source of Dhimurru&rsquo;s revenues is public funding (69%), and it is supplemented by Dhimurru&rsquo;s own generated income (20.5%), private contributions (9.2%) and fee-for-service income (1.6%). Dhimurru\u27s activities have interconnected goals: people management, environmental monitoring, conservation and restoration, and heritage and cultural protection. People management includes issuing general and special access permits to non-Indigenous visitors, checking permit compliance, camp site maintenance, fencing, and rubbish pickup. It accounts for over 74 per cent of Dhimurru&rsquo;s total expenditure. Weed control and crocodile management account for another 17 per cent of the Dhimurru&rsquo;s expenses.Public funding and fee-for-service revenues are the cost to society of this provision of environmental services through Indigenous ranger organisations. Both funding streams originate largely from institutional responsibilities of government. A variety ofCommonwealth programs such as Working on Country (WoC) and Indigenous Protected Areas (IPAs) are based on this principle. Here the government outsources some of its responsibility to protect the environment by contracting local Indigenous rangers to provide environmental services. In return, Indigenous rangers are required to provide some measure of accountability for their work through management plans, progress reports and financial reports. However, the compensation for this service is calculated on the basis of the government&rsquo;s accounting rule for granting funding and on what the ranger organisations estimate it will cost for them to deliver the service. They are not based on estimates of the benefits that the rangers&rsquo; activities generate for the Australian public.Lack of data, methodological limitations, and a short timeframe, severely restricted the quantitative assessment of the demand for environmental services. Therefore it is not possible to&nbsp; contrast the benefits of Indigenous provision of environmental services in the two IPAs with either&nbsp; the social costs or the organisations&rsquo; private expenditure. As a result, the data presented here is&nbsp; not sufficient to demonstrate in economic terms that the benefits of environmental service&nbsp; provision within the IPAs justify their social cost. Similarly, it was not possible to assess the&nbsp; feasibility of financing Indigenous provision of environmental services in the IPAs on the basis of he benefits it generates at the local and national levels. Further research is necessary to collect more data on such issues over longer time periods. A robust analysis of the costs and benefits of Indigenous provision of environmental services needs to account for temporal and spatial variability, and take into account the fluctuations in environmental, economic and social&nbsp; conditions. Priority should also be given to the collection of basic ecological data. This is necessary to assess the effectiveness of management practices in reaching environmental outcomes

Imaging of SNR IC443 and W44 with the Sardinia Radio Telescope at 1.5 GHz and 7 GHz

Observations of supernova remnants (SNRs) are a powerful tool for investigating the later stages of stellar evolution, the properties of the ambient interstellar medium, and the physics of particle acceleration and shocks. For a fraction of SNRs, multi-wavelength coverage from radio to ultra high-energies has been provided, constraining their contributions to the production of Galactic cosmic rays. Although radio emission is the most common identifier of SNRs and a prime probe for refining models, high-resolution images at frequencies above 5 GHz are surprisingly lacking, even for bright and well-known SNRs such as IC443 and W44. In the frameworks of the Astronomical Validation and Early Science Program with the 64-m single-dish Sardinia Radio Telescope, we provided, for the first time, single-dish deep imaging at 7 GHz of the IC443 and W44 complexes coupled with spatially-resolved spectra in the 1.5-7 GHz frequency range. Our images were obtained through on-the-fly mapping techniques, providing antenna beam oversampling and resulting in accurate continuum flux density measurements. The integrated flux densities associated with IC443 are S_1.5GHz = 134 +/- 4 Jy and S_7GHz = 67 +/- 3 Jy. For W44, we measured total flux densities of S_1.5GHz = 214 +/- 6 Jy and S_7GHz = 94 +/- 4 Jy. Spectral index maps provide evidence of a wide physical parameter scatter among different SNR regions: a flat spectrum is observed from the brightest SNR regions at the shock, while steeper spectral indices (up to 0.7) are observed in fainter cooling regions, disentangling in this way different populations and spectra of radio/gamma-ray-emitting electrons in these SNRs.Comment: 13 pages, 9 figures, accepted for publication to MNRAS on 18 May 201

Sardinia Radio Telescope wide-band spectral-polarimetric observations of the galaxy cluster 3C 129

We present new observations of the galaxy cluster 3C 129 obtained with the Sardinia Radio Telescope in the frequency range 6000-7200 MHz, with the aim to image the large-angular-scale emission at high-frequency of the radio sources located in this cluster of galaxies. The data were acquired using the recently-commissioned ROACH2-based backend to produce full-Stokes image cubes of an area of 1 deg x 1 deg centered on the radio source 3C 129. We modeled and deconvolved the telescope beam pattern from the data. We also measured the instrumental polarization beam patterns to correct the polarization images for off-axis instrumental polarization. Total intensity images at an angular resolution of 2.9 arcmin were obtained for the tailed radio galaxy 3C 129 and for 13 more sources in the field, including 3C 129.1 at the galaxy cluster center. These data were used, in combination with literature data at lower frequencies, to derive the variation of the synchrotron spectrum of 3C 129 along the tail of the radio source. If the magnetic field is at the equipartition value, we showed that the lifetimes of radiating electrons result in a radiative age for 3C 129 of t_syn = 267 +/- 26 Myrs. Assuming a linear projected length of 488 kpc for the tail, we deduced that 3C 129 is moving supersonically with a Mach number of M=v_gal/c_s=1.47. Linearly polarized emission was clearly detected for both 3C 129 and 3C 129.1. The linear polarization measured for 3C 129 reaches levels as high as 70% in the faintest region of the source where the magnetic field is aligned with the direction of the tail.Comment: 19 pages, 17 figures, accepted for publication in MNRA

Modeling complex metabolic reactions, ecological systems, and financial and legal networks with MIANN models based on Markov-Wiener node descriptors

[Abstract] The use of numerical parameters in Complex Network analysis is expanding to new fields of application. At a molecular level, we can use them to describe the molecular structure of chemical entities, protein interactions, or metabolic networks. However, the applications are not restricted to the world of molecules and can be extended to the study of macroscopic nonliving systems, organisms, or even legal or social networks. On the other hand, the development of the field of Artificial Intelligence has led to the formulation of computational algorithms whose design is based on the structure and functioning of networks of biological neurons. These algorithms, called Artificial Neural Networks (ANNs), can be useful for the study of complex networks, since the numerical parameters that encode information of the network (for example centralities/node descriptors) can be used as inputs for the ANNs. The Wiener index (W) is a graph invariant widely used in chemoinformatics to quantify the molecular structure of drugs and to study complex networks. In this work, we explore for the first time the possibility of using Markov chains to calculate analogues of node distance numbers/W to describe complex networks from the point of view of their nodes. These parameters are called Markov-Wiener node descriptors of order kth (Wk). Please, note that these descriptors are not related to Markov-Wiener stochastic processes. Here, we calculated the Wk(i) values for a very high number of nodes (>100,000) in more than 100 different complex networks using the software MI-NODES. These networks were grouped according to the field of application. Molecular networks include the Metabolic Reaction Networks (MRNs) of 40 different organisms. In addition, we analyzed other biological and legal and social networks. These include the Interaction Web Database Biological Networks (IWDBNs), with 75 food webs or ecological systems and the Spanish Financial Law Network (SFLN). The calculated Wk(i) values were used as inputs for different ANNs in order to discriminate correct node connectivity patterns from incorrect random patterns. The MIANN models obtained present good values of Sensitivity/Specificity (%): MRNs (78/78), IWDBNs (90/88), and SFLN (86/84). These preliminary results are very promising from the point of view of a first exploratory study and suggest that the use of these models could be extended to the high-throughput re-evaluation of connectivity in known complex networks (collation)

Multi-messenger observations of a binary neutron star merger

On 2017 August 17 a binary neutron star coalescence candidate (later designated GW170817) with merger time 12:41:04 UTC was observed through gravitational waves by the Advanced LIGO and Advanced Virgo detectors. The Fermi Gamma-ray Burst Monitor independently detected a gamma-ray burst (GRB 170817A) with a time delay of ~1.7 s with respect to the merger time. From the gravitational-wave signal, the source was initially localized to a sky region of 31 deg2 at a luminosity distance of 40+8-8 Mpc and with component masses consistent with neutron stars. The component masses were later measured to be in the range 0.86 to 2.26 Mo. An extensive observing campaign was launched across the electromagnetic spectrum leading to the discovery of a bright optical transient (SSS17a, now with the IAU identification of AT 2017gfo) in NGC 4993 (at ~40 Mpc) less than 11 hours after the merger by the One- Meter, Two Hemisphere (1M2H) team using the 1 m Swope Telescope. The optical transient was independently detected by multiple teams within an hour. Subsequent observations targeted the object and its environment. Early ultraviolet observations revealed a blue transient that faded within 48 hours. Optical and infrared observations showed a redward evolution over ~10 days. Following early non-detections, X-ray and radio emission were discovered at the transient’s position ~9 and ~16 days, respectively, after the merger. Both the X-ray and radio emission likely arise from a physical process that is distinct from the one that generates the UV/optical/near-infrared emission. No ultra-high-energy gamma-rays and no neutrino candidates consistent with the source were found in follow-up searches. These observations support the hypothesis that GW170817 was produced by the merger of two neutron stars in NGC4993 followed by a short gamma-ray burst (GRB 170817A) and a kilonova/macronova powered by the radioactive decay of r-process nuclei synthesized in the ejecta

Duty cycle of the radio galaxy B2 0258+35

Radio loud Active Galactic Nuclei are episodic in nature, cycling through periods of activity and quiescence. In this work we investigate the duty cycle of the radio galaxy B2~0258+35, which was previously suggested to be a restarted radio galaxy based on its morphology. The radio source consists of a pair of kpc-scale jets embedded in two large-scale lobes (~240 kpc) with relaxed shape and very low surface brightness, which resemble remnants of a past AGN activity. We have combined new LOFAR data at 145 MHz and new SRT data at 6600 MHz with available WSRT data at 1400 MHz to investigate the spectral properties of the outer lobes and derive their age. Interestingly, the spectrum of both the outer Northern and Southern lobes is not ultra-steep as expected for an old ageing plasma with spectral index values equal to $\rm \alpha_{1400}^{145}=0.48\pm0.11$ and $\rm \alpha_{6600}^{1400}=0.69\pm0.20$ in the outer Northern lobe, and $\rm \alpha_{1400}^{145}=0.73\pm0.07$ in the outer Southern lobe. Moreover, despite the wide frequency coverage available for the outer Northern lobe (145-6600~MHz), we do not identify a significant spectral curvature (SPC$\simeq$0.2$\pm0.2$). While mechanisms such as in-situ particle reacceleration, mixing or compression can temporarily play a role in preventing the spectrum from steepening, in no case seem the outer lobes to be compatible with being very old remnants of past activity as previously suggested (with age $\gtrsim$ 80 Myr). We conclude that either the large-scale lobes are still fuelled by the nuclear engine or the jets have switched off no more than a few tens of Myr ago. Our study shows the importance of combining morphological and spectral properties to reliably classify the evolutionary stage of low surface brightness, diffuse emission that low frequency observations are revealing around a growing number of radio sources.Comment: 13 pages, 4 figures, 6 tables, A&A accepte