GaLactic and Extragalactic All-sky Murchison Widefield Array (GLEAM) survey III: South Galactic Pole data release
T. Franzen, N. Hurley-Walker, S. White, P. Hancock, N. Seymour, A. Kapińska, L. Staveley-Smith, R. Wayth
备注：
13 pages, 7 figures, accepted for publication in PASA. Added link to images and source catalogue from GLEAM SGP data release in section 5. Corrected some mistakes in column numbers in section 4.5 describing catalogue. The catalogue is now also available on VizieR
发表信息：
Publications of the Astronomical Society of Australia (2021), 38, e014, 10 pages
We present the South Galactic Pole (SGP) data release from the GaLactic and Extragalactic All-sky Murchison Widefield Array (GLEAM) survey. These data combine both years of GLEAM observations at 72-231 MHz conducted with the Murchison Widefield Array (MWA) and cover an area of 5,113 $\mathrm{deg}^2$ centred on the SGP at 20$^\mathrm{h}$40$^\mathrm{m}$ < RA < 05$^\mathrm{h}$04$^\mathrm{m}$ and $-48°$ < Dec < $-2°$. At 216 MHz, the typical rms noise is $\approx 5$ mJy/beam and the angular resolution $\approx 2$ arcmin. The source catalogue contains a total of 108,851 components above $5σ$, of which 77 per cent have measured spectral indices between 72 and 231 MHz. Improvements to the data reduction in this release include the use of the GLEAM Extragalactic catalogue as a sky model to calibrate the data, a more efficient and automated algorithm to deconvolve the snapshot images, and a more accurate primary beam model to correct the flux scale. This data release enables more sensitive large-scale studies of extragalactic source populations as well as spectral variability studies on a one-year timescale.
This work makes available a further 2,860deg$^2$ of the GLEAM survey, covering half of the accessible Galactic Plane, across twenty frequency bands sampling $72-231$MHz, with resolution $4'-2'$. Unlike previous GLEAM data releases, we used multi-scale clean to better deconvolve large-scale Galactic structure. For the Galactic longitude ranges $345^\circ < l < 67^\circ$, $180^\circ < l < 240^\circ$, we provide a compact source catalogue of 22,037 components selected from a 60-MHz bandwidth image centred at 200-MHz, with RMS noise $\approx10-20$mJy beam$^{-1}$ and position accuracy better than $…
We detail and present results from a pilot study to assess the feasibility of detecting molecular lines at low radio frequencies. We observed a 400 square degree region centred on the Galactic Centre with the Murchison Widefield Array (MWA) between 103 and 133\,MHz targeting 28 known molecular species that have significant transitions. The results of this survey yield tentative detections of nitric oxide (NO) and the mercapto radical (SH). Both of these molecules appear to be associated with evolved stars.
We describe a new low-frequency wideband radio survey of the southern sky. Observations covering 72 - 231 MHz and Declinations south of $+30^\circ$ have been performed with the Murchison Widefield Array "extended" Phase II configuration over 2018 - 2020 and will be processed to form data products including continuum and polarisation images and mosaics, multi-frequency catalogues, transient search data, and ionospheric measurements. From a pilot field described in this work, we publish an initial data release covering 1,447 sq. deg over 4h < RA < 13h, -32.7deg < Dec < -20.7deg. We process twent…
International Centre for Radio Astronomy Research, Curtin University（国际射电天文中心，科廷大学）；Australian SKA Regional Centre (AusSRC), Curtin University（澳大利亚SKA区域中心（AusSRC），科廷大学）；CSIRO Space and Astronomy（CSIRO空间与天文学）
We describe the parameters of a low-frequency all-sky survey of compact radio sources using Interplanetary Scintillation (IPS), undertaken with the Murchison Widefield Array (MWA). While this survey gives important complementary information to low-resolution survey such as the MWA GLEAM survey, providing information on the subarsecond structure of every source, a survey of this kind has not been attempted in the era of low-frequency imaging arrays such as the MWA and LOFAR. Here we set out the capabilities of such a survey, describing the limitations imposed by the heliocentric observing geome…
The Murchison Widefield Array (MWA) is a new low frequency interferometric radio telescope, operating in the remote Murchison Radio Observatory in Western Australia. In this paper we present the first MWA observations of the well known radio relics in Abell 3667 (A3667) between 120 and 226 MHz. We clearly detect the radio relics in A3667 and present flux estimates and spectral indices for these features. The average spectral index of the north-west (NW) and south-east (SE) relics is -0.9 +/- 0.1 between 120 and 1400 MHz. We are able to resolve spatial variation in the spectral index of the NW …
Diffuse, non-thermal emission in galaxy clusters is increasingly being detected in low-frequency radio surveys and images. We present a new diffuse, steep-spectrum, non-thermal radio source within the cluster Abell 1127 found in survey data from the Murchison Widefield Array (MWA). We perform follow-up observations with the 'extended' configuration MWA Phase II with improved resolution to better resolve the source and measure its low-frequency spectral properties. We use archival Very Large Array S-band data to remove the discrete source contribution from the MWA data, and from a power law mod…
Using the Murchison Widefield Array (MWA), the low-frequency Square Kilometre Array (SKA1 LOW) precursor located in Western Australia, we have completed the GaLactic and Extragalactic All-sky MWA (GLEAM) survey, and present the resulting extragalactic catalogue, utilising the first year of observations. The catalogue covers 24,831 square degrees, over declinations south of $+30^\circ$ and Galactic latitudes outside $10^\circ$ of the Galactic plane, excluding some areas such as the Magellanic Clouds. It contains 307,455 radio sources with 20 separate flux density measurements across 72--231MHz,…
We present low-frequency spectral energy distributions of 60 known radio pulsars observed with the Murchison Widefield Array (MWA) telescope. We searched the GaLactic and Extragalactic All-sky MWA (GLEAM) survey images for 200-MHz continuum radio emission at the position of all pulsars in the ATNF pulsar catalogue. For the 60 confirmed detections we have measured flux densities in 20 x 8 MHz bands between 72 and 231 MHz. We compare our results to existing measurements and show that the MWA flux densities are in good agreement.
Significant new opportunities for astrophysics and cosmology have been identified at low radio frequencies. The Murchison Widefield Array is the first telescope in the Southern Hemisphere designed specifically to explore the low-frequency astronomical sky between 80 and 300 MHz with arcminute angular resolution and high survey efficiency. The telescope will enable new advances along four key science themes, including searching for redshifted 21 cm emission from the epoch of reionisation in the early Universe; Galactic and extragalactic all-sky southern hemisphere surveys; time-domain astrophys…
We analyse a 154 MHz image made from a 12 h observation with the Murchison Widefield Array (MWA) to determine the noise contribution and behaviour of the source counts down to 30 mJy. The MWA image has a bandwidth of 30.72 MHz, a field-of-view within the half-power contour of the primary beam of 570 deg^2, a resolution of 2.3 arcmin and contains 13,458 sources above 5 sigma. The rms noise in the centre of the image is 4-5 mJy/beam. The MWA counts are in excellent agreement with counts from other instruments and are the most precise ever derived in the flux density range 30-200 mJy due to the s…
We present a search for transient and variable radio sources at 154 MHz with the Murchison Widefield Array 32-tile prototype. Fifty-one images were obtained that cover a field of view of 1430 deg^2 centred on Hydra A. The observations were obtained over three days in 2010 March and three days in 2011 April and May. The mean cadence of the observations was 26 minutes and there was additional temporal information on day and year timescales. We explore the variability of a sample of 105 low frequency radio sources within the field. Four bright (S > 6 Jy) candidate variable radio sources were iden…
We present new molecular modelling for 14NO and 15NO and a deep, blind molecular line survey at low radio frequencies (99-129 MHz). This survey is the third in a series completed with the Murchison Widefield Array (MWA), but in comparison with the previous surveys, uses four times more data (17 hours vs. 4 hours) and is three times better in angular resolution (1' vs. 3'). The new molecular modelling for nitric oxide and its main isotopologue has seven transitions within the MWA frequency band (although we also present the higher frequency transitions). Although we did not detect any new molec…
We have compiled a catalogue of HII regions detected with the Murchison Widefield Array (MWA) between 72 and 231MHz. The multiple frequency bands provided by the MWA allow us identify the characteristic spectrum generated by the thermal Bremsstrahlung process in HII regions. We detect 302 HII regions between 260 < l < 340 and report on the positions, sizes, peak, integrated flux density, and spectral indices of these HII regions. By identifying the point at which HII regions transition from the optically thin to thick regime we derive the physical properties including the electron density, ion…
Recent observations with the Murchison Widefield Array at 185~MHz have serendipitously unveiled a heretofore unknown giant and relatively nearby ($z = 0.0178$) 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 $\sim$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 g…
We examined the latest data release from the GaLactic and Extragalactic All-sky Murchison Widefield Array (GLEAM) survey covering $345^\circ < l < 60^\circ$, $180^\circ < l < 240^\circ$, using these data and that of the Widefield Infrared Survey Explorer to follow up proposed candidate Supernova Remnants from other sources. Of the 101 candidates proposed in the region, we are able to definitively confirm ten as SNRs, tentatively confirm two as SNRs, and reclassify five as Hii regions. A further two are detectable in our images but difficult to classify; the remaining 82 are undetectable in the…
Estimating Galaxy Star Formation Rates from Murchison Widefield Array Radio Continuum Emission
Nagoya University（名古屋大学）；The Institute of Statistical Mathematics（统计数学研究所）；Stanford University（斯坦福大学）；SLAC National Accelerator Laboratory（SLAC国家加速器实验室）；Tohoku University（东北大学）；University of Western Australia（西澳大学）；CSIRO Space & Astronomy（澳大利亚联邦科学与工业研究组织空间与天文部）
We have studied radio haloes and relics in nine merging galaxy clusters using the Murchison Widefield Array (MWA). The images used for this study were obtained from the GaLactic and Extragalactic All-sky MWA (GLEAM) Survey which was carried out at 5 frequencies, viz. 88, 118, 154, 188 and 215 MHz. We detect diffuse radio emission in 8 of these clusters. We have estimated the spectra of haloes and relics in these clusters over the frequency range 80-1400 MHz; the first such attempt to estimate their spectra at low frequencies. The spectra follow a power law with a mean value of $α= -1.13\pm0.21…
Interplanetary scintillation (IPS) provides an approach for identifying the presence of sub-arcsec structures in radio sources, and very long baseline interferometry (VLBI) technique can help verify whether the IPS sources have fine structures on milli-arcsec (mas) scales. We searched the available VLBI archive for the 244 IPS sources detected by the Murchison Widefield Array at 162~MHz and found 63 cross-matches. We analysed the VLBI data of the 63 sources and characterised the compactness index in terms of the ratio $R$ of the VLBI-measured flux density at 4.3~GHz to the flux density estimat…
We present the first Murchison Widefield Array observations of the well-known cluster of galaxies Abell 3667 (A3667) between 105 and 241 MHz. A3667 is one of the best known examples of a galaxy cluster hosting a double radio relic and has been reported to contain a faint radio halo and bridge. The origins of radio halos, relics and bridges is still unclear, however galaxy cluster mergers seems to be an important factor. We clearly detect the North-West (NW) and South-East (SE) radio relics in A3667 and find an integrated flux density at 149 MHz of 28.1 +/- 1.7 and 2.4 +/- 0.1 Jy, respectively,…
The Tracking Tapered Gridded Estimator for the 21-cm power spectrum from the Murchison Widefield Array (MWA) drift scan observations -- III. Improved upper limits at $z = 8.2$ from multiple pointings
Indian Institute of Technology Madras（印度马德拉斯理工学院）；Indian Institute of Technology Kharagpur（印度克拉格普尔理工学院）；University of the Western Cape（西开普大学）；Raman Research Institute（拉曼研究所）
We report on a search for low-frequency radio variability in 944 bright (> 4Jy at 154 MHz) unresolved, extragalactic radio sources monitored monthly for several years with the Murchison Widefield Array. In the majority of sources we find very low levels of variability with typical modulation indices < 5%. We detect 15 candidate low frequency variables that show significant long term variability (>2.8 years) with time-averaged modulation indices M = 3.1 - 7.1%. With 7/15 of these variable sources having peaked spectral energy distributions, and only 5.7% of the overall sample having peaked spec…
We have carried out multiwavelength observations of the near-by ($z=0.046$) rich, merging galaxy cluster Abell 3376 with the Murchison Widefield Array (MWA). As a part of the GaLactic and Extragalactic All-sky MWA survey (GLEAM), this cluster was observed at 88, 118, 154, 188 and 215 MHz. The known radio relics, towards the eastern and western peripheries of the cluster, were detected at all the frequencies. The relics, with a linear extent of $\sim$ 1 Mpc each, are separated by $\sim$ 2 Mpc. Combining the current observations with those in the literature, we have obtained the spectra of these…
We previously reported a putative detection of a radio galaxy at z=10.15, selected from the GaLactic and Extragalactic All-sky Murchison Widefield Array (GLEAM) survey. The redshift of this source, GLEAM J0917-0012, was based upon three weakly detected molecular emission lines observed with the Atacama Large Millimetre Array (ALMA). In order to confirm this result, we conducted deep spectroscopic follow-up observations with ALMA and the Karl Jansky Very Large Array (VLA). The ALMA observations targeted the same CO lines previously reported in Band 3 (84-115GHz) and the VLA targeted the CO(4-3)…
While unobscured and radio-quiet active galactic nuclei are regularly being found at redshifts $z > 6$, their obscured and radio-loud counterparts remain elusive. We build upon our successful pilot study, presenting a new sample of low-frequency-selected candidate high-redshift radio galaxies (HzRGs) over a sky area twenty times larger. We have refined our selection technique, in which we select sources with curved radio spectra between 72-231 MHz from the GaLactic and Extragalactic All-sky Murchison Widefield Array (GLEAM) survey. In combination with the requirements that our GLEAM-selected H…
The GaLactic and Extragalactic All-sky MWA survey (GLEAM) is a radio continuum survey at 72-231 MHz of the whole sky south of declination +30 deg, carried out with the Murchison Widefield Array (MWA). In this paper, we derive source counts from the GLEAM data at 200, 154, 118 and 88 MHz, to a flux density limit of 50, 80, 120 and 290 mJy respectively, correcting for ionospheric smearing, incompleteness and source blending. These counts are more accurate than other counts in the literature at similar frequencies as a result of the large area of sky covered and this survey's sensitivity to exten…
This paper outlines how the new GaLactic and Extragalactic All-sky MWA Survey (GLEAM, Wayth et al. 2015), observed by the Murchison Widefield Array covering the frequency range 72 - 231 MHz, allows identification of a new large, complete, sample of more than 2000 bright extragalactic radio sources selected at 151 MHz. With a flux density limit of 4 Jy this sample is significantly larger than the canonical fully-complete sample, 3CRR (Laing, Riley & Longair 1983). In analysing this small bright subset of the GLEAM survey we are also providing a first user check of the GLEAM catalogue ahead of i…
We detect and characterise extended, diffuse radio emission from galaxy clusters at 168 MHz within the Epoch of Reionization 0-hour field: a $45^\circ \times 45^\circ$ region of the southern sky centred on R.~A.${}= 0^\circ$, decl.${}=-27^\circ$. We detect 29 sources of interest; a newly detected halo in Abell 0141; a newly detected relic in Abell 2751; 4 new halo candidates and a further 4 new relic candidates; and a new phoenix candidate in Abell 2556. Additionally, we find 9 clusters with unclassifiable, diffuse steep-spectrum emission as well as a candidate double relic system associated w…
In this paper we discuss the radio continuum and X-ray properties of the so-far poorly studied Galactic supernova remnant (SNR) G5.9+3.1. We present the radio spectral energy distribution (SED) of the Galactic SNR G5.9+3.1 obtained with the Murchison Widefield Array (MWA). Combining these new observations with the surveys at other radio continuum frequencies, we discuss the integrated radio continuum spectrum of this particular remnant. We have also analyzed an archival XMM-Newton observation, which represents the first detection of X-ray emission from this remnant. The SNR SED is very well ex…
We derive the synchrotron distribution in the Milky Way disk from HII region absorption observations over -40° < l < 40° at six frequencies of 76.2, 83.8, 91.5, 99.2, 106.9, and 114.6 MHz with the GaLactic and Extragalactic All-sky Murchison widefield array survey (GLEAM). We develop a new method of emissivity calculation by taking advantage of the Haslam et al., (1981) map and known spectral indices, which enable us to simultaneously derive the emissivity and the optical depth of HII regions at each frequency. We show our derived synchrotron emissivities based on 152 absorption features of HI…
GLEAM, the GaLactic and Extragalactic All-sky MWA survey, is a survey of the entire radio sky south of declination +25 deg at frequencies between 72 and 231 MHz, made with the Murchison Widefield Array (MWA) using a drift scan method that makes efficient use of the MWA's very large field-of-view. We present the observation details, imaging strategies and theoretical sensitivity for GLEAM. The survey ran for two years, the first year using 40 kHz frequency resolution and 0.5 s time resolution; the second year using 10 kHz frequency resolution and 2 s time resolution. The resulting image resolut…
We have detected 27 new supernova remnants (SNRs) using a new data release of the GLEAM survey from the Murchison Widefield Array (MWA) telescope, including the lowest surface-brightness SNR ever detected, G0.1-9.7. Our method uses spectral fitting to the radio continuum to derive spectral indices for 26/27 candidates, and our low-frequency observations probe a steeper-spectrum population than previously discovered. None of the candidates have coincident Wide-field Infrared Survey Explorer mid-IR emission, further showing that the emission is non-thermal. Using pulsar associations we derive ph…
Powerful radio-galaxies feature heavily in our understanding of galaxy evolution. However, when it comes to studying their properties as a function of redshift and/or environment, the most-detailed studies tend to be limited by small-number statistics. During Focus Meeting 3, on "Radio Galaxies: Resolving the AGN phenomenon", SVW presented a new sample of nearly 2,000 of the brightest radio-sources in the southern sky (Dec. $<$ 30 deg). These were observed at low radio-frequencies as part of the GaLactic and Extragalactic All-sky MWA (GLEAM) Survey, which is a continuum survey conducted using …
The search for emission from weakly interacting massive particle (WIMP) dark matter annihilation and decay has become a multi-pronged area of research not only targeting a diverse selection of astrophysical objects, but also taking advantage of the entire electromagnetic spectrum. The decay of WIMP particles into standard model particles has been suggested as a possible channel for synchrotron emission to be detected at low radio frequencies. Here, we present the stacking analysis of a sample of 33 dwarf spheroidal (dSph) galaxies with low-frequency (72 - 231 MHz) radio images from the GaLacti…
The GaLactic and Extragalactic All-sky Murchison Widefield Array (GLEAM) is a radio continuum survey at 76-227 MHz of the entire southern sky (Declination $<+30°$) with an angular resolution of $\approx 2$ arcmin. In this paper, we combine GLEAM data with optical spectroscopy from the 6dF Galaxy Survey to construct a sample of 1,590 local (median $z \approx 0.064$) radio sources with $S_{200\,\mathrm{MHz}} > 55$ mJy across an area of $\approx 16,700~\mathrm{deg}^{2}$. From the optical spectra, we identify the dominant physical process responsible for the radio emission from each galaxy: 73 per…
We present a search for transient and highly variable sources at low radio frequencies (150-200 MHz) that explores long timescales of 1-3 years. We conducted this search by comparing the TIFR GMRT Sky Survey Alternative Data Release 1 (TGSS ADR1) and the GaLactic and Extragalactic All-sky Murchison Widefield Array (GLEAM) survey catalogues. To account for the different completeness thresholds in the individual surveys, we searched for compact GLEAM sources above a flux density limit of 100 mJy that were not present in the TGSS ADR1; and also for compact TGSS ADR1 sources above a flux density l…
This Rescaled Subset of the Alternative Data Release 1 to the Tata Institute of Fundamental Physics Giant Metrewave Radio Telescope Sky Survey (TGSS-RSADR1) modifies the initial data release of TGSS-ADR1 (Intema et al. 2017) to bring that catalogue to the same flux scale as the extragalactic catalogue from the GaLactic and Extragalactic All-sky Murchison Widefield Array survey (GLEAM: Wayth et al. 2015; Hurley-Walker et al. 2017). In this paper we motivate the derivation of correct and complementary flux density scales, introduce a methodology for correction based on radial basis functions, ap…
The Murchison Widefield Array (MWA) has observed the entire southern sky (Declination, $δ<$ 30 deg) at low radio-frequencies, over the range 72-231 MHz. These observations constitute the GaLactic and Extragalactic All-sky MWA (GLEAM) Survey, and we use the extragalactic catalogue (Galactic latitude, $|b| >$ 10 deg) to define the GLEAM 4-Jy (G4Jy) Sample. This is a complete sample of the 'brightest' radio-sources ($S_{\mathrm{151MHz}} >$ 4 Jy), the majority of which are active galactic nuclei with powerful radio-jets. Crucially, low-frequency observations allow the selection of such sources in …
The entire southern sky (Declination, $δ<$ 30 deg) has been observed using the Murchison Widefield Array (MWA), which provides radio imaging of $\sim$2-arcmin resolution at low frequencies (72-231 MHz). This is the GaLactic and Extragalactic All-sky MWA (GLEAM) Survey, and we have previously used a combination of visual inspection, cross-checks against the literature, and internal matching to identify the 'brightest' radio-sources ($S_{\mathrm{151MHz}} >$ 4 Jy) in the extragalactic catalogue (Galactic latitude, $|b| >$ 10 deg). We refer to these 1,863 sources as the GLEAM 4-Jy (G4Jy) Sample, a…
The low-frequency polarisation properties of radio sources are poorly studied, particularly in statistical samples. However, the new generation of low-frequency telescopes, such as the Murchison Widefield Array (MWA; the precursor for the low-frequency component of the Square Kilometre Array) offers an opportunity to probe the physics of radio sources at very low radio frequencies. In this paper, we present a catalogue of linearly-polarised sources detected at 216 MHz, using data from the Galactic and Extragalactic All-sky MWA (GLEAM) survey. Our catalogue covers the Declination range $-17^{\c…
Synchrotron emission pervades the Galactic plane at low radio frequencies, originating from cosmic ray electrons interacting with the Galactic magnetic field. Using a low-frequency radio telescope, the Murchison Widefield Array (MWA), we measure the free-free absorption of this Galactic synchrotron emission by intervening HII regions along the line of sight. These absorption measurements allow us to calculate the Galactic cosmic-ray electron emissivity behind and in front of 47 detected HII regions in the region $250^\circ < l < 355^\circ$, $|b| < 2^\circ$. We find that all average emissivitie…
We use Murchison Widefield Array observations of interplanetary scintillation (IPS) to determine the source counts of point ($<$0.3 arcsecond extent) sources and of all sources with some subarcsecond structure, at 162 MHz. We have developed the methodology to derive these counts directly from the IPS observables, while taking into account changes in sensitivity across the survey area. The counts of sources with compact structure follow the behaviour of the dominant source population above $\sim$3 Jy but below this they show Euclidean behaviour. We compare our counts to those predicted by simul…
Around 10% of bright low-frequency radio sources observed with the Murchison Widefield Array (MWA) show strong Interplanetary Scintillation (IPS) on timescales of a few seconds, implying that almost all their low-frequency radio emission comes from a compact component less than 0.5 arcsec in angular size. Most of these objects are compact steep-spectrum (CSS) or MHz-peaked spectrum (MPS) radio sources. We have used mid-infrared data from the Wide-field Infrared Survey Explorer (WISE) catalogue to search for the host galaxies of 65 strongly-scintillating MWA sources and compare their properties…
The low-frequency linearly-polarised radio source population is largely unexplored. However, a renaissance in low-frequency polarimetry has been enabled by pathfinder and precursor instruments for the Square Kilometre Array. In this second paper from the POlarised GaLactic and Extragalactic All-Sky Murchison Widefield Array (MWA) Survey -- the POlarised GLEAM Survey, or POGS -- we present the results from our all-sky MWA Phase I Faraday Rotation Measure survey. Our survey covers nearly the entire Southern sky in the Declination range $-82^{\circ}$ to $+30^{\circ}$ at a resolution between aroun…
We present a catalogue of over 7000 sources from the GLEAM survey which have significant structure on sub-arcsecond scales at 162MHz. The compact nature of these sources was detected and quantified via their Interplanetary Scintillation (IPS) signature, measured in interferometric images from the Murchison Widefield Array. The advantage of this approach is that all sufficiently compact sources across the survey area are included down to a well-defined flux density limit. The survey is based on $\sim$250$\times$ 10-minute observations, and the area covered is somewhat irregular, but the area wi…
This paper is the fourth in a series of low-frequency searches for technosignatures. Using the Murchison Widefield Array over two nights we integrate 7 hours of data toward the Galactic Centre (centred on the position of Sagittarius A*) with a total field-of-view of 200 deg^2. We present a targeted search toward 144 exoplanetary systems, at our best yet angular resolution (75 arc seconds). This is the first technosignature search at a frequency of 155 MHz toward the Galactic Centre (our previous central frequencies have been lower). A blind search toward in excess of 3 million stars toward the…
The low-frequency sky may reveal some of the secrets yet to be discovered and until recently, molecules had never been detected within interstellar clouds at frequencies below 700MHz (Lovas, 2003) . Following the pilot survey towards the Galactic Centre at 103--133MHz with the Murchison Widefield Array (Tremblay, 2017), we surveyed 400 degree squared centered on the Orion KL nebula from 99--170MHz. Orion is a nearby region of active star formation and known to be a chemically rich environment. In this paper, we present tentative detections of nitric oxide and its isotopologues, singularly deut…
