- ID:
- ivo://CDS.VizieR/J/AJ/139/1695
- Title:
- Celestial Reference Frame at 24 and 43 GHz
- Short Name:
- J/AJ/139/1695
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present astrometric results for compact extragalactic objects observed with the Very Long Baseline Array at radio frequencies of 24 and 43GHz. Data were obtained from ten 24-hr observing sessions made over a five-year period. These observations were motivated by the need to extend the International Celestial Reference Frame (ICRF) to higher radio frequencies to enable improved deep space navigation after 2016 and to improve state-of-the-art astrometry. Source coordinates for 268 sources were estimated at 24GHz and for 131 sources at 43GHz.
Number of results to display per page
Search Results
- ID:
- ivo://CDS.VizieR/J/AJ/139/1713
- Title:
- Celestial Reference Frame at 24 and 43GHz. II
- Short Name:
- J/AJ/139/1713
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have measured the submilliarcsecond structure of 274 extragalactic sources at 24 and 43 GHz in order to assess their astrometric suitability for use in a high-frequency celestial reference frame (CRF). Ten sessions of observations with the Very Long Baseline Array have been conducted over the course of ~5 years, with a total of 1339 images produced for the 274 sources. There are several quantities that can be used to characterize the impact of intrinsic source structure on astrometric observations including the source flux density, the flux density variability, the source structure index, the source compactness, and the compactness variability.
- ID:
- ivo://CDS.VizieR/J/A+A/651/A74
- Title:
- 4C +29.45 OVRO and KNV fluxes curve
- Short Name:
- J/A+A/651/A74
- Date:
- 22 Feb 2022
- Publisher:
- CDS
- Description:
- We present the results of multi-epoch, multifrequency monitoring of blazar 4C +29.45, which was regularly monitored as part of the Interferometric Monitoring of GAmma-ray Bright Active Galactic Nuclei (iMOGABA) program - a key science program of the Korean Very long baseline interferometry Network (KVN). Observations were conducted simultaneously at 22, 43, 86, and 129GHz over the 4 years from 5 December 2012 to 28 December 2016. We also used additional data from the 15GHz Owens Valley Radio Observatory (OVRO) monitoring program. From the 15GHz light curve, we estimated the variability timescales of the source during several radio flux enhancements. We found that the source experienced six radio flux enhancements with variability timescales of 9-187days during the observing period, yielding corresponding variability Doppler factors of 9-27. From the simultaneous multifrequency KVN observations, we were able to obtain accurate radio spectra of the source and hence to more precisely measure the turnover frequencies {nu}_r_, of synchrotron self-absorption (SSA) emission with a mean value of {nu}_r_=28.9GHz. Using jet geometry assumptions, we estimated the size of the emitting region at the turnover frequency. We found that the equipartition magnetic field strength is up to two orders of magnitude higher than the SSA magnetic field strength (0.001-0.1G). This is consistent with the source being particle dominated. We performed a careful analysis of the systematic errors related to the making of these estimations. From the results, we concluded that the equipartition region is located upstream from the SSA region.
- ID:
- ivo://CDS.VizieR/J/MNRAS/432/1294
- Title:
- Fermi unassociated sources ATCA observations
- Short Name:
- J/MNRAS/432/1294
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report results of the first phase of observations with Australia Telescope Compact Array (ATCA) at 5 and 9GHz of the fields around 411 {gamma}-ray sources with declinations less than +10{deg} detected with Fermi but marked as unassociated in the 2FGL catalogue. We have detected 424 sources with flux densities in a range of 2mJy to 6Jy in the fields of 283 {gamma}-ray sources within their position error ellipses drawn to cover the area of 99 per cent probability of their localisation. Of them, 146 objects were detected in both bands. We found 84 sources with spectral index flatter than -0.5 in our sample. The majority of detected sources are weaker than 100 mJy and for this reason were not found in previous surveys. Approximately 1/3 of our sample, 128 objects, have the probability of being associated by more than 10 times than the probability of being a background source found in the vicinity of a {gamma}-ray object by chance. We present the catalogue of positions of these sources, estimates of their flux densities and spectral indices when available.
- ID:
- ivo://CDS.VizieR/J/ApJS/98/1
- Title:
- First Caltech-Jodrell Bank VLBI Survey. I.
- Short Name:
- J/ApJS/98/1
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the first results from the first Caltech-Jodrell Bank VLBI survey (the CJ1 survey). The CJ1 sample includes 135 radio sources with total flux density 1.3Jy>S_6cm>=0.7Jy, declination delta_1950>=35deg, and Galactic latitude |b^II|>10deg. It extends the flux density limit of the complete "PR" sample studied by Pearson & Readhead from 1.3 to 0.7Jy and increases the total number of sources from 65 to 200. The complete survey includes VLBI images at both lambda-18 and 6cm of all objects in the extended sample that have cores strong enough to be mapped with the Mark II VLBI system. These images provide a large enough sample to study, for example, the variety of morphologies exhibited by compact radio sources, cosmological evolution, superluminal motion, and misalignment between parsec-scale and kiloparsec-scale radio structures. In this paper we present lambda-18cm VLBI observations of 56 CJ1 and 31 PR sources made in 1990-1991, including images of 82 sources. The observations were made with a "snapshot" technique in which each source was observed in three 20-30-minute scans using an array of 12-16 antennas. The images have resolution 3-10mas and dynamic range greater than 100:1. Later papers in the series will present the remaining lambda-18cm observations, the lambda-6cm observations, and the analysis and interpretation of the results.
- ID:
- ivo://CDS.VizieR/J/ApJS/98/33
- Title:
- First Caltech-Jodrell Bank VLBI Survey. II.
- Short Name:
- J/ApJS/98/33
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report lambda-18 cm VLBI observations made in 1991 September of a further 25 objects from the first Caltech-Jodrell Bank VLBI Survey (the CJ1 survey). The CJ1 sample is a complete, flux-density limited sample of 135 radio sources with total flux density at lambda-6cm between 0.7 and 1.3Jy. These observations complete the lambda-18cm part of the survey. Together with the results of Paper I (Polatidis et al., <J/ApJS/98/1>), we have now observed 81 CJ1 sources at lambda-18cm. Later papers in the series will present lambda-6cm observations and the analysis and interpretation of the results.
- ID:
- ivo://CDS.VizieR/J/A+A/559/A95
- Title:
- Fitted proper motions for the DR solution
- Short Name:
- J/A+A/559/A95
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We propose new estimates of the secular aberration drift, mainly due to the rotation of the Solar System about the Galactic center, based on up-to-date VLBI observations and and improved method of outlier elimination. We fit degree-2 vector spherical harmonics to extragalactic radio source proper motion field derived from geodetic VLBI observations spanning 1979-2013. We pay particular attention to the outlier elimination procedure to remove outliers from (i) radio source coordinate time series and (ii) the proper motion sample. We obtain more accurate values of the Solar system acceleration compared to those in our previous paper. The acceleration vector is oriented towards the Galactic center within ~7{deg}. The component perpendicular to the Galactic plane is statistically insignificant. We show that an insufficient cleaning of the data set can lead to strong variations in the dipole amplitude and orientation, and statistically biased results.
- ID:
- ivo://CDS.VizieR/J/PASJ/52/631
- Title:
- Galactic plane VERA survey
- Short Name:
- J/PASJ/52/631
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In order to search for new VLBI sources in the galactic plane that can be used as phase reference sources in differential VLBI, we conducted 22GHz observations of radio sources in the galactic plane using the Japanese VLBI Network (J-Net). We have observed 267 VLBI source candidates selected from existing radio surveys and have detected 93 sources at a signal-to-noise ratio larger than 5. While 42 of the 93 detected sources had already been detected with VLBI at relatively lower frequency (typically 2 to 8GHz), the remaining 51 are found to be new VLBI sources detected for the first time. These are located within |b|<=5{deg}, and have a large number of galactic maser sources around them. Thus, they are potential candidates for phase reference sources for VLBI Exploration of Radio Astrometry (VERA), which is the first VLBI array dedicated to phase-referencing VLBI astrometry aimed at measuring the parallax and proper motion of maser sources in the whole Galaxy.
- ID:
- ivo://CDS.VizieR/J/A+A/364/391
- Title:
- 86GHz VLBI survey of compact radio sources
- Short Name:
- J/A+A/364/391
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- File table1 contains the list of observed sources, providing the source coordinates (J2000) and redshift, detection status, type, optical magnitude, and brightness temperature of the radio emission. File table4 contains the description of the VLBI data, and provide the observed total and correlated flux densities, the parameters of single gaussian component model fits, and the parameters of hybrid images of the observed sources. File table5 contains multicomponent model fits for the sources with detected extended structures and the brightness temperatures derived from these model fits.
- 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.
