- ID:
- ivo://CDS.VizieR/J/MNRAS/377/430
- Title:
- Jodrell Bank Flat-spectrum radio sample
- Short Name:
- J/MNRAS/377/430
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the selection of the Jodrell Bank Flat-spectrum (JBF) radio source sample, which is designed to reduce the uncertainties in the Cosmic Lens All-Sky Survey (CLASS) gravitational lensing statistics arising from the lack of knowledge about the parent population luminosity function. From observations at 4.86GHz with the Very Large Array, we have selected a sample of 117 flat-spectrum radio sources with flux densities greater than 5mJy. These sources were selected in a similar manner to the CLASS complete sample and are therefore representative of the parent population at low flux densities. The vast majority (~90 per cent) of the JBF sample are found to be compact on the arcsec scales probed here and show little evidence of any extended radio jet emission. Using the JBF and CLASS complete samples, we find the differential number counts slope of the parent population above and below the CLASS 30-mJy flux density limit to be 2.07+/-0.02 and 1.96+/-0.12, respectively.
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402. JVLA images of W51A
- ID:
- ivo://CDS.VizieR/J/A+A/595/A27
- Title:
- JVLA images of W51A
- Short Name:
- J/A+A/595/A27
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present new JVLA observations of the high-mass cluster-forming region W51A from 2 to 16GHz with resolution {theta}_fwhm_~~0.3-0.5". The data reveal a wealth of observational results: (1) Currently-forming, very massive (proto-O) stars are traced by o-H_2_CO 2_1,1_-2_1,2_ emission, suggesting that this line can be used efficiently as a massive protostar tracer. (2) There is a spatially distributed population of <~mJy continuum sources, including hypercompact HII regions and candidate colliding wind binaries, in and around the W51 proto-clusters. (3) There are two clearly detected protoclusters, W51e and W51 IRS2, that are gas-rich but may have most of their mass in stars within their inner <~0.05pc. The majority of the bolometric luminosity in W51 most likely comes from a third population of OB stars between these clusters. The presence of a substantial population of exposed O-stars coincident with a population of still-forming massive stars, along with a direct measurement of the low mass loss rate via ionized gas outflow from W51 IRS2, together imply that feedback is ineffective at halting star formation in massive protoclusters. Instead, feedback may shut off the large-scale accretion of diffuse gas onto the W51 protoclusters, implying that they are evolving towards a state of gas exhaustion rather than gas expulsion. Recent theoretical models predict gas exhaustion to be a necessary step in the formation of gravitationally bound stellar clusters, and our results provide an observational validation of this process.
- ID:
- ivo://CDS.VizieR/J/ApJ/871/215
- Title:
- JVLA rotation measures of Smith cloud bckg sources
- Short Name:
- J/ApJ/871/215
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Smith Cloud is a high-velocity cloud with an orbit suggesting it has made at least one passage through the Milky Way disk. A magnetic field found around this cloud has been thought to provide extra stability as it passes through the Galactic halo. We use the Karl G. Jansky Very Large Array to measure Faraday rotation measures (RMs) toward 1105 extragalactic background point sources behind and next to the Smith Cloud to constrain the detailed geometry and strength of its magnetic field. The RM pattern across the cloud gives the detailed morphology of the magnetic field structure, which indicates a field draped over the ionized gas and compressed at the head of the cloud. We constrain the peak line-of-sight magnetic field strength to >~+5{mu}G and create a model of the magnetic field to demonstrate that a draped configuration can qualitatively explain the morphology of the observed RMs.
- ID:
- ivo://CDS.VizieR/J/A+A/596/A106
- Title:
- 1Jy northern AGN sample
- Short Name:
- J/A+A/596/A106
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Continuum spectra covering centimetre to submillimetre wavelengths are presented for a northern sample of 104 extragalactic radio sources, mainly active galactic nuclei, based on four-epoch Planck data. The nine Planck frequencies, from 30 to 857GHz, are complemented by a set of simultaneous ground-based radio observations between 1.1 and 37GHz. The single-survey Planck data confirm that the flattest high-frequency radio spectral indices are close to zero, indicating that the original accelerated electron energy spectrum is much harder than commonly thought, with power-law index around 1.5 instead of the canonical 2.5. The radio spectra peak at high frequencies and exhibit a variety of shapes. For a small set of low-z sources, we find a spectral upturn at high frequencies, indicating the presence of intrinsic cold dust. Variability can generally be approximated by achromatic variations, while sources with clear signatures of evolving shocks appear to be limited to the strongest outbursts.
- ID:
- ivo://CDS.VizieR/J/AJ/143/35
- Title:
- KCAL VERA 22 GHz calibrator survey
- Short Name:
- J/AJ/143/35
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We observed at 22GHz with the VLBI array VERA a sample of 1536 sources with correlated flux densities brighter than 200mJy at 8GHz. One half of target sources has been detected. The detection limit was around 200mJy. We derived the correlated flux densities of 877 detected sources in three ranges of projected baseline lengths. The objective of these observations was to determine the suitability of given sources as phase calibrators for dual-beam and phase-referencing observations at high frequencies. Preliminary results indicate that the number of compact extragalactic sources at 22GHz brighter than a given correlated flux density level is twice less than at 8GHz.
- ID:
- ivo://CDS.VizieR/J/AJ/158/31
- Title:
- Kepler K2 mission fields 3-5: radio continuum survey
- Short Name:
- J/AJ/158/31
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present Murchison Widefield Array (MWA) monitoring of the Kepler K2 mission fields 3, 4, and 5 at frequencies of 155 and 186 MHz, from observations contemporaneous with the K2 observations. This work follows from previous MWA and Giant Metrewave Radio Telescope (GMRT) surveys of field 1, with the current work benefiting from a range of improvements in the data processing and analysis. We continue to build a body of systematic low-frequency blind surveys overlapping with transient/variable survey fields at other wavelengths, providing multiwavelength data for object classes such as flare stars. From the current work, we detect no variable objects at a surface density above 2x10^-4^ per square degree, at flux densities of ~500 mJy, and an observation cadence of days to weeks, representing almost an order of magnitude decrease in the measured upper limits compared to previous results in this part of observational parameter space. This continues to show that radio transients at meter and centimeter wavelengths are rare.
407. KGS EoR0 Catalogue
- ID:
- ivo://CDS.VizieR/J/MNRAS/461/4151
- Title:
- KGS EoR0 Catalogue
- Short Name:
- J/MNRAS/461/4151
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Detection of the epoch of reionization HI signal requires a precise understanding of the intervening galaxies and AGN, both for instrumental calibration and foreground removal. We present a catalogue of 7394 extragalactic sources at 182MHz detected in the RA=0 field of the Murchison Widefield Array Epoch of Reionization observation programme. Motivated by unprecedented requirements for precision and reliability we develop new methods for source finding and selection. We apply machine learning methods to self-consistently classify the relative reliability of 9490 source candidates. A subset of 7466 are selected based on reliability class and signal-to-noise ratio criteria. These are statistically cross-matched to four other radio surveys using both position and flux density information. We find 7369 sources to have confident matches, including 90 partially resolved sources that split into a total of 192 sub-components. An additional 25 unmatched sources are included as new radio detections. The catalogue sources have a median spectral index of -0.85. Spectral flattening is seen towards lower frequencies with a median of -0.71 predicted at 182MHz. The astrometric error is 7-arcsec compared to a 2.3-arcmin beam FWHM. The resulting catalogue covers ~1400deg^2^ and is complete to approximately 80mJy within half beam power. This provides the most reliable discrete source sky model available to date in the MWA EoR0 field for precision foreground subtraction.
- ID:
- ivo://CDS.VizieR/J/ApJ/753/62
- Title:
- Kinematic distance ambiguity in HII regions
- Short Name:
- J/ApJ/753/62
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Using H I absorption spectra from the International Galactic Plane Survey, a new method is implemented to resolve the kinematic distance ambiguity for 75 H II regions with known systemic velocities from radio recombination lines. A further 40 kinematic distance determinations are made for H II region candidates without known systemic velocities through an investigation of the presence of H I absorption around the terminal velocity. New kinematic distance determinations can be used to further constrain spiral arm parameters and the location and extent of other structures in the Milky Way disk. H I absorption toward continuum sources beyond the solar circle is also investigated. Follow-up studies of H I at higher resolution than the 1' to 2' of existing Galactic Plane Surveys will provide kinematic distances to many more H II regions on the far side of the Galactic center. On the basis of the velocity channel summation technique developed in this paper, a much larger sample of H II regions will be analyzed in a future paper to remove the near-far distance ambiguity.
- ID:
- ivo://CDS.VizieR/J/MNRAS/355/20
- Title:
- K magnitudes of 74MHz radio sources
- Short Name:
- J/MNRAS/355/20
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In this paper we present near-infrared K-band imaging of a sample of ultra-steep-spectrum (USS) radio sources selected at 74-MHz. The dual selection criteria of low frequency and USS mean that we should be sensitive to the highest-redshift (z>5) radio galaxies. We have obtained K-band magnitudes for all of the objects in our sample of 26 and discuss the properties of each.
- ID:
- ivo://CDS.VizieR/J/MNRAS/426/2107
- Title:
- KNoWS pilot bright sample
- Short Name:
- J/MNRAS/426/2107
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- During 2010-11, the Medicina 32-m dish hosted the seven-feed 18-26.5GHz receiver built for the Sardinia Radio Telescope, with the goal to perform its commissioning. This opportunity was exploited to carry out a pilot survey at 20GHz over the area for {delta}>+72.3{deg}. This paper describes all the phases of the observations, as they were performed using new hardware and software facilities. The map-making and source extraction procedures are illustrated. A customized data reduction tool was used during the follow-up phase, which produced a list of 73 confirmed sources down to a flux density of 115mJy. The resulting catalogue, presented here, is complete above 200mJy. Source counts are in agreement with those provided by the Australia Telescope 20GHz (AT20G) survey. This pilot activity paves the way for a larger project, the K-band Northern Wide Survey (KNoWS), whose final aim is to survey the whole Northern hemisphere down to a flux limit of 50mJy (5{sigma}).
