To make a power spectrum (PS) detection of the 21-cm signal from the Epoch of Reionisation (EoR), one must avoid/subtract bright foreground sources. Sources such as Fornax A present a modelling challenge due to spatial structures spanning from arc seconds up to a degree. We compare modelling with multi-scale (MS) CLEAN components to ‘shapelets’, an alternative set of basis functions. We introduce a new image-based shapelet modelling package, SHAMFI. We also introduce a new CUDA simulation code (WODEN) to generate point source, Gaussian, and shapelet components into visibilities. We test performance by modelling a simulation of Fornax A, peeling the model from simulated visibilities, and producing a residual PS. We find the shapelet method consistently subtracts large-angular-scale emission well, even when the angular resolution of the data is changed. We find that when increasing the angular resolution of the data, the MS CLEAN model worsens at large angular scales. When testing on real Murchison Widefield Array data, the expected improvement is not seen in real data because of the other dominating systematics still present. Through further simulation, we find the expected differences to be lower than obtainable through current processing pipelines. We conclude shapelets are worthwhile for subtracting extended galaxies, and may prove essential for an EoR detection in the future, once other systematics have been addressed.

We apply two methods to estimate the 21-cm bispectrum from data taken within the Epoch of Reionisation (EoR) project of the Murchison Widefield Array (MWA). Using data acquired with the Phase II compact array allows a direct bispectrum estimate to be undertaken on the multiple redundantly spaced triangles of antenna tiles, as well as an estimate based on data gridded to the uv-plane. The direct and gridded bispectrum estimators are applied to 21 h of high-band (167–197 MHz; z = 6.2–7.5) data from the 2016 and 2017 observing seasons. Analytic predictions for the bispectrum bias and variance for point-source foregrounds are derived. We compare the output of these approaches, the foreground contribution to the signal, and future prospects for measuring the bispectra with redundant and non-redundant arrays. We find that some triangle configurations yield bispectrum estimates that are consistent with the expected noise level after 10 h, while equilateral configurations are strongly foreground-dominated. Careful choice of triangle configurations may be made to reduce foreground bias that hinders power spectrum estimators, and the 21-cm bispectrum may be accessible in less time than the 21-cm power spectrum for some wave modes, with detections in hundreds of hours.

The current generation of experiments aiming to detect the neutral hydrogen signal from the Epoch of Reionisation (EoR) is likely to be limited by systematic effects associated with removing foreground sources from target fields. In this paper, we develop a model for the compact foreground sources in one of the target fields of the MWA’s EoR key science experiment: the ‘EoR1’ field. The model is based on both the MWA’s GLEAM survey and GMRT 150 MHz data from the TGSS survey, the latter providing higher angular resolution and better astrometric accuracy for compact sources than is available from the MWA alone. The model contains 5 049 sources, some of which have complicated morphology in MWA data, Fornax A being the most complex. The higher resolution data show that 13% of sources that appear point-like to the MWA have complicated morphology such as double and quad structure, with a typical separation of 33 arcsec. We derive an analytic expression for the error introduced into the EoR two-dimensional power spectrum due to peeling close double sources as single point sources and show that for the measured source properties, the error in the power spectrum is confined to high k⊥ modes that do not affect the overall result for the large-scale cosmological signal of interest. The brightest 10 mis-modelled sources in the field contribute 90% of the power bias in the data, suggesting that it is most critical to improve the models of the brightest sources. With this hybrid model, we reprocess data from the EoR1 field and show a maximum of 8% improved calibration accuracy and a factor of two reduction in residual power in k-space from peeling these sources. Implications for future EoR experiments including the SKA are discussed in relation to the improvements obtained.

The Pleistocene College Farm Silty Clay Member of the Creeting Formation at Great Blakenham, Suffolk, south-east England is shown to contain indigenous and recycled dinoflagellate cysts and other derived palynomorphs. The indigenous dinoflagellate cysts indicate a marine influence during deposition of the clay, whilst the other palynomorphs demonstrate derivation of sediment from a wide catchment of Carboniferous, Jurassic and Cretaceous bedrocks. It is argued, by comparison with palynological data from the Chillesford Clay Member of the Norwich Crag Formation some 25km to the east, that these sediments were eroded from western, south-central and south-eastern Britain, and transported by the early River Thames to its estuary, where they were redeposited at the western margin of the Crag Basin, during the Early Pleistocene Tiglian TC3 Substage. This interpretation refines earlier research which concluded the College Farm Silty Clay was deposited in a predominantly freshwater environment, such as a lagoon, without any direct access to the sea or major river.

Mapping combined with till provenance studies have resulted in a re-appraisal of the pre-Devensian glacial stratigraphy of Norfolk, England. The traditional model invoked two formations, a North Sea Drift Formation (NSDF) overlain by a Lowestoft Formation, formed by co-existing ice-sheets originating in Scandinavia and Northern Britain respectively. The NSDF included three diamictons, the First, Second and Third Cromer tills. The Briton’s Lane Sands and Gravels were considered to overlie the Lowestoft Formation. However, our work has shown this stratigraphy to be untenable, and we propose a model of several glaciations instead of co-existing ice-sheets. In our revised stratigraphy, the oldest formation, the Happisburgh Formation (including the Happisburgh or First Cromer Till) includes massive, sandy tills derived from northern Britain. The overlying Lowestoft Formation, including the Second Cromer (Walcott) Till is confirmed as derived from the west, introducing much Jurassic material as well as Chalk. The Sheringham Cliffs Formation includes both brown sandy tills (the Third Cromer Till) and ‘marly drift’, in a variety of tectonic relationships, and derived from the north and NNW. Finally the Briton’s Lane Formation is the only formation to include Scandinavian erratics. Dating of the four formations is at varying levels of confidence, with the Lowestoft Formation most confidently confirmed as MIS 12. The Happisburgh Formation is believed to represent an earlier glaciation, and MIS 16 is proposed. The Sheringham Cliffs Formation is tentatively believed to date from MIS 10, and the Briton’s Lane Formation is assigned to MIS 6.

We compare first-order (refractive) ionospheric effects seen by the MWA with the ionosphere as inferred from GPS data. The first-order ionosphere manifests itself as a bulk position shift of the observed sources across an MWA field of view. These effects can be computed from global ionosphere maps provided by GPS analysis centres, namely the CODE. However, for precision radio astronomy applications, data from local GPS networks needs to be incorporated into ionospheric modelling. For GPS observations, the ionospheric parameters are biased by GPS receiver instrument delays, among other effects, also known as receiver DCBs. The receiver DCBs need to be estimated for any non-CODE GPS station used for ionosphere modelling. In this work, single GPS station-based ionospheric modelling is performed at a time resolution of 10 min. Also the receiver DCBs are estimated for selected Geoscience Australia GPS receivers, located at Murchison Radio Observatory, Yarragadee, Mount Magnet and Wiluna. The ionospheric gradients estimated from GPS are compared with that inferred from MWA. The ionospheric gradients at all the GPS stations show a correlation with the gradients observed with the MWA. The ionosphere estimates obtained using GPS measurements show promise in terms of providing calibration information for the MWA.

The Murchison Widefield Array is a Square Kilometre Array Precursor. The telescope is located at the Murchison Radio–astronomy Observatory in Western Australia. The MWA consists of 4 096 dipoles arranged into 128 dual polarisation aperture arrays forming a connected element interferometer that cross-correlates signals from all 256 inputs. A hybrid approach to the correlation task is employed, with some processing stages being performed by bespoke hardware, based on Field Programmable Gate Arrays, and others by Graphics Processing Units housed in general purpose rack mounted servers. The correlation capability required is approximately 8 tera floating point operations per second. The MWA has commenced operations and the correlator is generating 8.3 TB day−1 of correlation products, that are subsequently transferred 700 km from the MRO to Perth (WA) in real-time for storage and offline processing. In this paper, we outline the correlator design, signal path, and processing elements and present the data format for the internal and external interfaces.

The Murchison Widefield Array is a new low-frequency interferometric radio telescope built in Western Australia at one of the locations of the future Square Kilometre Array. We describe the automated radio-frequency interference detection strategy implemented for the Murchison Widefield Array, which is based on the aoflagger platform, and present 72–231 MHz radio-frequency interference statistics from 10 observing nights. Radio-frequency interference detection removes 1.1% of the data. Radio-frequency interference from digital TV is observed 3% of the time due to occasional ionospheric or atmospheric propagation. After radio-frequency interference detection and excision, almost all data can be calibrated and imaged without further radio-frequency interference mitigation efforts, including observations within the FM and digital TV bands. The results are compared to a previously published Low-Frequency Array radio-frequency interference survey. The remote location of the Murchison Widefield Array results in a substantially cleaner radio-frequency interference environment compared to Low-Frequency Array’s radio environment, but adequate detection of radio-frequency interference is still required before data can be analysed. We include specific recommendations designed to make the Square Kilometre Array more robust to radio-frequency interference, including: the availability of sufficient computing power for radio-frequency interference detection; accounting for radio-frequency interference in the receiver design; a smooth band-pass response; and the capability of radio-frequency interference detection at high time and frequency resolution (second and kHz-scale respectively).

We present the results of an approximately 6 100 deg2 104–196 MHz radio sky survey performed with the Murchison Widefield Array during instrument commissioning between 2012 September and 2012 December: the MWACS. The data were taken as meridian drift scans with two different 32-antenna sub-arrays that were available during the commissioning period. The survey covers approximately 20.5 h < RA < 8.5 h, − 58° < Dec < −14°over three frequency bands centred on 119, 150 and 180 MHz, with image resolutions of 6–3 arcmin. The catalogue has 3 arcmin angular resolution and a typical noise level of 40 mJy beam− 1, with reduced sensitivity near the field boundaries and bright sources. We describe the data reduction strategy, based upon mosaicked snapshots, flux density calibration, and source-finding method. We present a catalogue of flux density and spectral index measurements for 14 110 sources, extracted from the mosaic, 1 247 of which are sub-components of complexes of sources.

Filtrates from cultures of wild isolates of Phellinus contiguus grown on liquid medium containing malt extract induced precocious fruiting of this resupinate polypore when tested in a bioassay. Active filtrates were analysed using gel filtration, HPLC and GC-MS and were compared with filtrates from single spore progeny, two of which lacked fruiting inducing activity. The active material was polar and heat stable, passed through both anion and cation exchange columns and had a mol. wt less than approx. 1000. Fractionation using HPLC on amino-silica yielded one fraction which was active on its own and a second, later eluting fraction, which had scarcely detectable activity when alone, but when combined with the first fraction had much higher activity than either alone. GC-MS showed that both this first fraction and the most active fraction from P2 gel filtration were rich in mono- and disaccharide sugars. In comparison with fractions from parallel inactive filtrates, all active fractions contained more myo-inositol and a relatively high glucose/disaccharide ratio.

It is suggested that a combination of high concentrations of myo-inositol and apoplastic glucose may be required for initiation of fruiting in P. contiguus. Although additional work is needed, this view is consistent with known features of growth and fruiting in white rot fungi.

The northern, James Ross Island region of the Larsen Basin, on the eastern, back-arc margin of the Antarctic Peninsula magmatic arc, includes one of the thickest and most complete Upper Cretaceous sedimentary successions exposed in the Southern Hemisphere. However, the southern part of the basin remains poorly known, mainly owing to inaccessibility and lack of exposure. Table Nunatak, an isolated, 1-km-long, 400-m-wide outcrop at the tip of Kenyon Peninsula, is the only known exposure of Upper Cretaceous or younger strata in this region. The 62-m-thick succession exposed there is assigned to the newly defined Table Nunatak Formation. It consists mainly of sharp-based, amalgamated beds of fine-grained sandstone up to 2.8 m thick, with subordinate intervals of intensely bioturbated mudstone. Wave ripples are present at some levels, and locally developed swaley cross-stratification provides evidence for storm-generated combined-flow deposition. However, most sandstone beds appear to be internally structureless apart from normal grading, and are interpreted as the direct suspension deposits of highly sediment-charged storm- and/or flood-related flows. The succession represents relatively nearshore deposition, probably at the mouth of a river or deltaic distributary channel. Charcoalified plant debris, abundant at the tops of some sandstone beds, suggests a periodically wildfire-swept hinterland forested largely by coniferous trees. Dinoflagellate cyst assemblages indicate a late Santonian age, and suggest correlation with the basal part of the Lachman Crags Member of the Santa Marta Formation (Marambio Group) on James Ross Island. Palaeocurrents, sandstone petrography and the high sediment supply rate proposed for the Table Nunatak Formation, suggest a relatively high-relief source area to the west, with large-scale erosion of granitoid plutons and metamorphic rocks, possibly related to arc uplift during a mid-Cretaceous compressional episode. The formation is evidence of a major southward extension of the Upper Cretaceous strata exposed in the northern Larsen Basin, and suggests lateral continuity of shallow-marine deposition for at least 500–600 km along the Weddell Sea margin of the Antarctic Peninsula in Santonian times.

The onshore record of Cenozoic glaciation in the Antarctic Peninsula region is limited to a number of isolated localities on Alexander Island, the South Shetland Islands and in the James Ross Island area. In the James Ross Island area, Late Cretaceous sedimentary rocks are unconformably overlain by a unit of diamictites and tuffs, which occur at the base of the James Ross Island Volcanic Group. These rocks are here defined as the Hobbs Glacier Formation, and on the basis of palynological studies are assigned to a Miocene (?late Miocene) age. The diamictites are interpreted as representing glaciomarine sedimentation close to the grounding line of either a floating ice shelf or a grounded tidewater glacier in a marine basin. Provenance studies indicate that the glacier was flowing from the Antarctic Peninsula towards the southeast. Volcanic tuffs conformably overlie the diamictites and are interpreted as representing deposition in a periglacial delta front setting in either a marine or non-marine basin, away from direct glacial influence. The Hobbs Glacier Formation and overlying James Ross Island Volcanic Group help to enhance our understanding of the Neogene glacial chronology of West Antarctica.