- ID:
- ivo://CDS.VizieR/VIII/102
- Title:
- GLEAM II. Galactic plane
- Short Name:
- VIII/102
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This work makes available a further of the GaLactic and Extragalactic All-sky Murchison Widefield Array (GLEAM) survey, covering half of the accessible galactic plane, across 20 frequency bands sampling 72-231MHz, with resolution 4-2arcmin. Unlike previous GLEAM data releases, we used multi-scale CLEAN to better deconvolve large-scale galactic structure. For the galactic longitude ranges 345{deg}<l<67{deg}, 180{deg}<l<240{deg}, we provide a compact source catalogue of 22037 components selected from a 60-MHz bandwidth image centred at 200MHz, with RMS noise ~-10-20mJy/beam and position accuracy better than 2-arcsec. The catalogue has a completeness of 50% at ~120mJy, and a reliability of 99.86%. It covers galactic latitudes 1{deg}<=|b|<=10{deg} towards the galactic centre and |b|<=10{deg} for other regions, and is available from Vizier; images covering |b|<=10{deg} for all longitudes are made available on the GLEAM Virtual Observatory (VO).server and SkyView.
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Search Results
- ID:
- ivo://CDS.VizieR/VIII/109
- Title:
- GLEAM III. South Galactic Pole
- Short Name:
- VIII/109
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- 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 72-231MHz conducted with the Murchison Widefield Array (MWA) and cover an area of 5,113 deg^2^ centred on the SGP at 20h40m<RA<05h04m and -48{deg}<Dec<-2{deg}. At 216MHz, the typical rms noise is ~5mJy/beam and the angular resolution ~2 arcmin. The source catalogue contains a total of 108851 components above 5{sigma}, of which 77 per cent have measured spectral indices between 72 and 231MHz. 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.
- ID:
- ivo://CDS.VizieR/J/other/PASA/38.41
- Title:
- GLEAM 200MHz local radio luminosity function
- Short Name:
- J/other/PASA/38.
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The GaLactic and Extragalactic All-sky Murchison Widefield Array (GLEAM) is a radio continuum survey at 76-227MHz of the entire southern sky (Declination <+30{deg}) with an angular resolution of ~2arcmin. 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~0.064) radio sources with S_200MHz_>55mJy across an area of ~16700deg^2^. From the optical spectra, we identify the dominant physical process responsible for the radio emission from each galaxy: 73 per cent are fuelled by an active galactic nucleus (AGN) and 27 per cent by star formation. We present the local radio luminosity function for AGN and star-forming galaxies at 200MHz and characterise the typical radio spectra of these two populations between 76MHz and ~1GHz. For the AGN, the median spectral index between 200MHz and ~1GHz, {alpha}, is -0.600+/-0.010 (where S proportional to {nu}^{alpha}^) and the median spectral index within the GLEAM band, {alpha}_low_, is -0.704+/-0.011. For the star-forming galaxies, the median value of {alpha}_high_ is -0.650+/-0.010 and the median value of {alpha}_low_ is -0.596+/-0.015. Among the AGN population, flat-spectrum sources are more common at lower radio luminosity, suggesting the existence of a significant population of weak radio AGN that remain core-dominated even at low frequencies. However, around 4 per cent of local radio AGN have ultra-steep radio spectra at low frequencies ({alpha}_low_<-1.2). These ultra-steep-spectrum sources span a wide range in radio luminosity, and further work is needed to clarify their nature.
- ID:
- ivo://CDS.VizieR/VIII/107
- Title:
- GLEAM sources ionospheric position shifts
- Short Name:
- VIII/107
- Date:
- 22 Feb 2022
- Publisher:
- CDS
- Description:
- Nearly 200 hours of observing with the Murchison Widefield Array (MWA) radio telescope during the Galactic and Extra-galactic All-sky MWA (GLEAM) survey were used to assemble images of ionospheric structure. These images cover a nearly 50 degree-wide area on the sky at a cadence of 10 minutes over many 5-7 hours-long observing runs. They are generated by tracking the apparent motions of ~200-800 cosmic radio sources caused by changes in the transverse gradient of the ionospheric total electron content. Spectral analysis of these images revealed that the dataset was dominated by three distinct signatures. The first is consistent with field-aligned structures within the topside ionosphere/lower plasmasphere previously imaged with the MWA. The second are structures that are relatively large and aligned nearly east/west. Regional weather data implies that these are preferentially detected when there is a noticeable shear within the sub- tropical jet stream, which passes near the MWA. This suggests that this signature may be related to gravity waves launched by jet stream shear. The final signature is consistent with the properties of so-call electro-buoyancy waves that are known to occur at midlatitudes at night. Detections of these were more common when regional sporadic-E was present, supporting a proposed connection between these waves and polarization electric fields that may arise within sporadic-E. We discuss the implications for future observations with the Square Kilometer Array.
- ID:
- ivo://CDS.VizieR/J/A+A/563/A130
- Title:
- GLIMPSE/BGPS 6.7GHz methanol maser survey
- Short Name:
- J/A+A/563/A130
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of a 6.7GHz methanol maser survey from the Effelsberg 100m radio telescope. A sample of 404 sources from the Bolocam Galactic Plane Survey (BGPS) 1.1mm dust clump survey that met specific Galactic Legacy Infrared Mid-Plane Survey Extraodinaire (GLIMPSE) point-source color criteria was selected and 318 of these were observed. The new observations resulted in the detection of 29 methanol masers, including 12 new ones. Together with the additional 74 detections from the literature, this means that a total of 103 methanol masers are coincident with 1.1mm dust clumps, yielding an overall detection rate of 26%. A comparison of the properties of a 1.1mm dust clump and a 6.7GHz methanol maser indicates that methanol masers with a higher flux density and/or luminosity are generally associated with more massive but less dense 1.1mm dust clumps. The overall detection rate of 26% appears to vary as a function of the derived H_2_ column density of the associated 1.1mm dust clump. The methanol masers were primarily detected toward the brighter and more massive 1.1mm dust clumps. A subsample of 194 sources that overlapped sources with observations of the 95GHz methanol line was investigated in more detail for the properties of 1.1mm dust clumps. The statistical analysis reveals that 1.1mm dust clumps with both class I and II counterparts have much higher mean and median values of mass, column density, and flux density than those with only class I or II counterparts. Based on our much larger sample, we slightly revise the boundary defined previously for selecting BGPS sources associated with a class II methanol maser, wherein ~80% of expected class II methanol masers will be detected with a detection rate in the range of 40-50%.
- ID:
- ivo://CDS.VizieR/J/MNRAS/377/571
- Title:
- GLIMPSE 6.7GHz methanol masers non-detections
- Short Name:
- J/MNRAS/377/571
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The University of Tasmania Mt Pleasant 26-m and Ceduna 30-m radio telescopes have been used to search for 6.7-GHz class II methanol masers towards 200 GLIMPSE (The Galactic Legacy Infrared Mid-Plane Survey Extraordinaire) sources. The target regions were selected on the basis of their mid-infrared colours as being likely to be young high-mass star formation regions and are either bright at 8.0{mu}m, or have extreme [3.6]-[4.5] colour. Methanol masers were detected towards 38 sites, nine of these being new detections. The prediction was that approximately 20 new 6.7-GHz methanol masers would be detected within 3.5-arcmin of the target GLIMPSE sources, but this is the case for only six of the new detections. A number of possible reasons for the discrepancy between the predicted and actual number of new detections have been investigated. It was not possible to draw any firm conclusions as to the cause, but it may be because many of the target sources are at an evolutionary phase prior to that associated with 6.7-GHz methanol masers. Through comparison of the spectra collected as part of this search with those in the literature, the average lifetime of individual 6.7-GHz methanol maser spectral features is estimated to be around 150yr, much longer than is observed for 22-GHz water masers.
- ID:
- ivo://CDS.VizieR/J/AJ/136/159
- Title:
- Global 86GHz VLBI survey of compact radio sources
- Short Name:
- J/AJ/136/159
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present results from a large 86GHz global very long baseline interferometry (VLBI) survey of compact radio sources. The main goal of the survey is to increase by factors of 3-5 the total number of objects accessible for future 3mm VLBI imaging. The survey observations reach a baseline sensitivity of 0.1Jy and an image sensitivity of better than 10mJy/beam. A total of 127 compact radio sources have been observed. The observations have yielded images for 109 sources, extending the database of the sources imaged at 86GHz with VLBI observation by a factor of 5, and only six sources have not been detected. The remaining 12 objects have been detected but could not be imaged due to insufficient closure phase information.
- ID:
- ivo://CDS.VizieR/J/A+A/580/A43
- Title:
- Global HI content from a stacking experiment
- Short Name:
- J/A+A/580/A43
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We study the atomic neutral hydrogen (HI) content of ~1600 galaxies up to z~0.1 using stacking techniques. The observations were carried out with the Westerbork Synthesis Radio Telescope (WSRT) in the area of the SDSS South Galactic Cap (SSGC), where we selected a galaxy sample from the SDSS spectroscopic catalog. Multi-wavelength information is provided by SDSS, NVSS, GALEX, and WISE. We use the collected information to study HI trends with color, star-forming, and active galactic nuclei (AGN) properties. Using near-UV (NUV)-r colors, galaxies are divided into blue cloud, green valley and red sequence galaxies.
- ID:
- ivo://CDS.VizieR/J/A+A/651/A86
- Title:
- GLOSTAR Galactic plane survey. II. SNR.
- Short Name:
- J/A+A/651/A86
- Date:
- 17 Jan 2022 00:20:41
- Publisher:
- CDS
- Description:
- The properties of the population of Galactic supernova remnants (SNRs) are essential to our understanding of the dynamics of the interstellar medium (ISM) in the Milky Way. However, the completeness of the catalog of Galactic SNRs is expected to be only ~30%, with on order 700 SNRs yet to be detected. Deep interferometric radio continuum surveys of the Galactic plane help in rectifying this apparent deficiency by identifying low surface brightness SNRs and compact SNRs that have not been detected in previous surveys. However, SNRs are routinely confused with HII regions, which can have similar radio morphologies. Radio spectral index, polarization, and emission at mid-infrared (MIR) wavelengths can help distinguish between SNRs and HII regions. We aim to identify SNR candidates using continuum images from the Karl G. Jansky Very Large Array GLObal view of the STAR formation in the Milky Way (GLOSTAR) survey. GLOSTAR is a C-band (4-8GHz) radio wavelength survey of the Galactic plane covering 358{deg}>=l<=60{deg}, |b|<=1{deg}. The continuum images from this survey, which resulted from observations with the most compact configuration of the array, have an angular resolution of 18''. We searched for SNRs in these images to identify known SNRs, previously identified SNR candidates, and new SNR candidates. We study these objects in MIR surveys and the GLOSTAR polarization data to classify their emission as thermal or nonthermal. We identify 157 SNR candidates, of which 80 are new. Polarization measurements provide evidence of nonthermal emission from 9 of these candidates. We find that two previously identified candidates are filaments. We also detect emission from 91 of the 94 known SNRs in the survey region. Four of these are reclassified as HII regions following detection in MIR surveys. The better sensitivity and resolution of the GLOSTAR data have led to the identification of 157 SNR candidates, along with the reclassification of several misidentified objects. We show that the polarization measurements can identify nonthermal emission, despite the diffuse Galactic synchrotron emission. These results underscore the importance of higher resolution and higher sensitivity radio continuum data in identifying and confirming SNRs.
- ID:
- ivo://CDS.VizieR/J/A+A/627/A175
- Title:
- GLOSTAR. Radio Source Catalogue I
- Short Name:
- J/A+A/627/A175
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Radio continuum surveys of the Galactic plane are an excellent way to identify different source populations such as planetary nebulae, HII regions, and radio stars and characterize their statistical properties. The Global View of Star Formation in the Milky Way (GLOSTAR) survey will study the star formation in the Galactic plane between -2{deg}<l<85{deg} and |b|<1{deg} with unprecedented sensitivity in both flux density (~40uJy/beam) and range of angular scales (~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 l=32{deg} and b=0{deg} (28{deg}<l<36{deg} and |b|<1{deg}). This map has a resolution of 18" and a sensitivity of 60-150uJy/beam. We present data acquired in 40 hours of observations with the VLA in D-configuration. Two 1GHz wide sub-bands were observed simultaneously and they were centered at 4.7 and 6.9GHz. These data were calibrated and imaged using the Obit software package. The source extraction was 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 crossmatching with other catalogs and calculating the spectral indices (S({nu}){prop.to}{nu}^{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 to previously reported data. These first GLOSTAR results have increased the number of reliable HII regions in this part of the Galaxy by a factor of four.
