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تسجيل مستخدم جديدNew candidate radio supernova remnants detected in the GLEAM survey over $345^circ < l < 60^circ$, $180^circ < l < 240^circ$
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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 physical properties for six candidate SNRs, finding G0.1-9.7 may be younger than 10kyr. 60% of the candidates subtend areas larger than 0.2deg$^{2}$ on the sky, compared to $<25$% of previously-detected SNRs. We also make the first detection of two SNRs in the Galactic longitude range $220^circ-240^circ$.
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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 these data. We also investigated the 18 unclassified Multi-Array Galactic Plane Imaging Survey (MAGPIS) candidate SNRs, newly confirming three as SNRs, reclassifying two as Hii regions, and exploring the unusual spectra and morphology of two others.
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 $2$. The catalogue has a completeness of 50% at $approx120$mJy, and a reliability of 99.86%. It covers Galactic latitudes $1^circleq|b|leq10^circ$ toward the Galactic Centre and $|b|leq10^circ$ for other regions, and is available from Vizier; images covering $|b|leq10^circ$ for all longitudes are made available on the GLEAM VO server and SkyView.
The GLOSTAR survey will study the star formation in the Galactic plane between $-2^{circ}< textit{l}< 85^{circ}$ and $|b| < 1^{circ}$ with unprecedented sensitivity in both, flux density ($sim$ 40 $mu Jy$ beam$^{-1}$) and range of angular scales ($si
m$ 1.5 to the largest radio structures in the Galaxy). In this paper we present the first results obtained from a radio continuum map of a 16 square degree sized region of the Galactic plane centered on $textit{l} = 32^{circ}$ and $b = 0^{circ}$ ($28^{circ} < textit{l} < 36^{circ}$ and $|b| < 1^{circ}$). This map has a resolution of 18 and sensitivity of $sim$ 60-150 $mu Jy$ beam$^{-1}$. We present data acquired with the VLA in D-configuration. Two 1 GHz wide sub-bands were observed simultaneously and centred at 4.7 and 6.9 GHz. These data were calibrated and imaged using the $textit{Obit}$ software package. The source extraction has been performed using the BLOBCAT software package and verified through a combination of visual inspection and cross-matching with other radio and mid-infrared surveys. The final catalog consists of 1575 discrete radio sources and 27 large scale structures (including W43 and W44). By cross-matching with other catalogs and calculating the spectral indices ($S( u) propto u^alpha$), we have classified 231 continuum sources as HII regions, 37 as ionization fronts, and 46 as planetary nebulae. The longitude and latitude distribution and negative spectral indices are all consistent with the vast majority of the unclassified sources being extragalactic background sources. We present a catalog of 1575 radio continuum sources and discuss their physical properties, emission nature and relation with previously reported. These first GLOSTAR results have increased the number of reliable HII regions in this part of the Galaxy by a factor of four.
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