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Register a new userGLOSTAR -- Radio Source Catalog I: $28^{circ}< textit{l} < 36^{circ}$ and $|b| < 1^{circ}$
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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 ($sim$ 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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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.
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.
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 $220^circ-240^circ$.
We have studied the properties of molecular clouds in the second quadrant of the Milky Way Mid-plane from l$=$104$.!!^{circ}$75 to l$=$119$.!!^{circ}$75 and b$=-$5$.!!^{circ}$25 to b$=$5$.!!^{circ}$25 using the $^{12}$CO, $^{13}$CO, and C$^{18}$O $J=1-0$ emission line data from the Milky Way Imaging Scroll Painting project (MWISP). We have identified 857 and 300 clouds in the $^{12}$CO and $^{13}$CO spectral cubes, respectively, using the DENDROGRAM + SCIMES algorithms. The distances of the molecular clouds are estimated and the physical properties like masses, sizes, and surface densities of the clouds are tabulated. The molecular clouds in the Perseus arm are about 30$-$50 times more massive and 4$-$6 times larger than the clouds in the Local arm. This result, however, is likely biased by distance selection effects. The surface densities of the clouds are enhanced in the Perseus arm with an average value of $sim$100 M$_{odot}$ pc$^{-2}$. We selected the 40 most extended ($>$0.35 arcdeg$^2$) molecular clouds from the $^{12}$CO catalog to build the H$_2$ column density probability distribution function (N-PDF). About 78% of the N-PDFs of the selected molecular clouds are well fitted with log-normal functions with only small deviations at high-densities which correspond to star-forming regions with scales of $sim$1-5 pc in the Local arm and $sim$5-10 pc in the Perseus arm. About 18% of the selected molecular clouds have power-law N-PDFs at high-densities. In these molecular clouds, the majority of the regions fitted with the power-law correspond to molecular clumps of sizes of $sim$1 pc or filaments of widths of $sim$1 pc.
We have developed a method to make a spectral-line-based survey of hot cores, which represent an important stage of high-mass star formation, and applied the method to the data of the FUGIN (FOREST Unbiased Galactic plane Imaging survey with the Nobeyama 45-m telescope) survey. First, we select hot core candidates by searching the FUGIN data for the weak hot core tracer lines (HNCO and CH$_3$CN) by stacking, and then we conduct follow-up pointed observations on these candidates in C$^{34}$S, SO, OCS, HC$_3$N, HNCO, CH$_3$CN, and CH$_3$OH $J=2-1$ and $J=8-7$ lines to confirm and characterize them. We applied this method to the $l = 10^circ-20^circ$ portion of the FUGIN data and identified 22 Hot Cores (compact sources with more than two significant detection of the hot core tracer lines, i.e., SO, OCS, HC$_3$N, HNCO, CH$_3$CN, or CH$_3$OH $J=8-7$ lines) and 14 Dense Clumps (sources with more than two significant detection of C$^{34}$S, CH$_3$OH $J=2-1$, or the hot core tracer lines). The identified Hot Cores are found associated with signposts of high-mass star formation such as ATLASGAL clumps, WISE HII regions, and Class II methanol masers. For those associated with ATLASGAL clumps, their bolometric luminosity to clump mass ratios are consistent with the star formation stages centered at the hot core phase. The catalog of FUGIN Hot Cores provides a useful starting point for further statistical studies and detailed observations of high-mass star forming regions.
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