- 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.
Number of results to display per page
Search Results
- 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/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/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.
- ID:
- ivo://CDS.VizieR/J/A+A/602/A31
- Title:
- G29.37+0.1 610MHz image
- Short Name:
- J/A+A/602/A31
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report on the first detailed multiwavelength study of the radio source G29.37+0.1, which is an as-yet-unclassified object linked to the very-high-energy gamma-emitting source HESS J1844-030. The origin of the multiwavelength emission toward G29.37+0.1 has not been clarified so far, leaving open the question about the physical relationship between these sources. Using observations carried out with the Giant Metrewave Radio Telescope (GMRT), we performed high-quality full-synthesis imaging at 610MHz of the field containing G29.37+0.1. The obtained data, combined with observations at 1400MHz from the MAGPIS were used to investigate in detail the properties of its radio emission. Additionally, we reprocessed archival data obtained with the XMM-Newton and Chandra observatories in order to get a multiwavelength view of this unusual source. The radio source G29.37+0.1 mainly consists of a bright twisted structure, named the S-shaped feature. The high sensitivity of the new GMRT observations allowed the identification of potential lobes, jets and a nuclear central region in the S-shaped morphology of G29.37+0.1. We also highlight the detection of diffuse and low surface brightness emission enveloping the brightest emitting regions. The brightest emission in G29.37+0.1 has a radio synchrotron spectral index alpha=0.59+/-0.09. Variations in the spectral behaviour are observed across the whole radio source with the flattest spectral features in the central nuclear and jets components (alpha~0.3). These results lead us to conclude that the brightest radio emission from G29.37+0.1 likely represents a newly recognized radio galaxy. The identification of optical and infrared counterparts to the emission arising from the core of G29.37+0.1 strengthens our interpretation of an extragalactic origin of the radio emission. We performed several tests to explain the physical mechanism responsible for the observed X-ray emission, which appears overlapping the northeastern part of the radio emission. Our spectral analysis demonstrated that a non-thermal origin for the X-ray emission compatible with a pulsar wind nebula is quite possible. The analysis of the spatial distribution of the CO gas revealed the presence of a complex of molecular clouds located in projection adjacent to the radio halo emission and probably interacting with it. We propose that the faint halo represents a composite supernova remnant with a pulsar powered component given by the diffuse X-ray emission superimposed along the line of sight to the radio galaxy. Further broadband observations of HESS J1844-030 are needed to disentangle its origin, although its shape and position suggest an extragalactic origin connected to G29.37+0.1.
- ID:
- ivo://CDS.VizieR/J/MNRAS/464/3357
- Title:
- GMRT 610-MHz observations of the AMI001 field
- Short Name:
- J/MNRAS/464/3357
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present 610-MHz Giant Metrewave Radio Telescope observations of 0.84deg^2^ of the AMI001 field (centred on 00h23m10s, +31d53') with an rms noise of 18microJy/beam in the centre of the field. A total of 955 sources are detected, and 814 are included in the source count analysis. The source counts from these observations are consistent with previous work. We have used these data to study the spectral index distribution of a sample of sources selected at 15.7GHz from the recent deep extension to the Tenth Cambridge (10C) survey. The median spectral index, alpha, (where S{prop.to}nu^-alpha^^) between 0.08<S_15.7GHz/mJy<0.2 is 0.32+/-0.14, showing that star-forming galaxies, which have much steeper spectra, are not contributing significantly to this population. This is in contrast to several models, but in agreement with the results from the 10C ultra-deep source counts; the high-frequency sky therefore continues to be dominated by radio galaxies down to S_15.7GHz_=0.1mJy.
- ID:
- ivo://CDS.VizieR/J/A+A/551/A24
- Title:
- GMRT Radio Halo Cluster Survey diffuse sources
- Short Name:
- J/A+A/551/A24
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- To gain further insight on the origin of diffuse radio sources in galaxy clusters and their connection with cluster merger processes, we performed GMRT low frequency observations of the radio halos, relics and new candidates belonging to the GMRT Radio Halo Cluster Sample first observed at 610MHz. Our main aim was to investigate their observational properties and integrated spectrum at frequencies below 610MHz.
- ID:
- ivo://CDS.VizieR/J/MNRAS/392/1403
- Title:
- GMRT radios sources around J0916+6348 field
- Short Name:
- J/MNRAS/392/1403
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present deep multifrequency observations using the Giant Metrewave Radio Telescope (GMRT) at 153, 244, 610 and 1260MHz of a field centred on J0916+6348, to search for evidence of fossil radio lobes which could be due to an earlier cycle of episodic activity of the parent galaxy, as well as haloes and relics in clusters of galaxies. We do not find any unambiguous evidence of episodic activity in a list of 374 sources, suggesting that such activity is rare even in relatively deep low-frequency observations. We examine the spectra of all the sources by combining our observations with those from the Westerbork Northern Sky Survey (WENSS), NRAO (National Radio Astronomy Observatories) VLA (Very Large Array) Sky Survey (NVSS) and the Faint Images of the Radio Sky at Twenty-Centimeters Survey (FIRST).
- ID:
- ivo://CDS.VizieR/J/ApJ/859/33
- Title:
- GOBELINS. IV. VLBA obs. of Taurus
- Short Name:
- J/ApJ/859/33
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present new trigonometric parallaxes and proper motions of young stellar objects in the Taurus molecular cloud complex from observations collected with the Very Long Baseline Array as part of the Gould's Belt Distances Survey. We detected 26 young stellar objects and derived trigonometric parallaxes for 18 stars with an accuracy of 0.3% to a few percent. We modeled the orbits of six binaries and determined the dynamical masses of the individual components in four of these systems (V1023 Tau, T Tau S, V807 Tau, and V1000 Tau). Our results are consistent with the first trigonometric parallaxes delivered by the Gaia satellite and reveal the existence of significant depth effects. We find that the central portion of the dark cloud Lynds 1495 is located at d=129.5+/-0.3pc, while the B216 clump in the filamentary structure connected to it is at d=158.1+/-1.2pc. The closest and remotest stars in our sample are located at d=126.6+/-1.7pc and d=162.7+/-0.8pc, yielding a distance difference of about 36pc. We also provide a new distance estimate for HL Tau that was recently imaged. Finally, we compute the spatial velocity of the stars with published radial velocity and investigate the kinematic properties of the various clouds and gas structures in this region.
