Imaging Sources in the Third Realization of the International Celestial Reference Frame

Abstract

The third iteration of the International Celestial Reference Frame (ICRF3) is made up of 4536 quasars observed at S/X bands using Very Long baseline Interferometry (VLBI). These sources are high redshift quasars, typically between $1<z<2$, that are believed to host active galactic nuclei (AGN) at their centers. The position of compact radio sources can be determined better than sources with large amounts of extended radio structure. Here we report information on a series of 20 observations from January 2017 through December 2017 which were designed for precise astrometry and to monitor the structure of sources included in the ICRF3. We targeted 3627 sources over the one year campaign and found the median flux density of 2697 detected sources at S-band is 0.13 Jy, and the flux density of 3209 sources detected at X-band is 0.09 Jy. We find that $70\%$ of detected sources in our campaign are considered compact at X-band and ideal for use in the ICRF and $89\%$ of the 2615 sources detected at both frequencies have a flat spectral index, $\alpha >0.5$

arXiv commentAccepted in AJ. 22 Pages, 12 Figures

References in corpus (10)

• DiFX2: A more flexible, efficient, robust and powerful software correlator
• A morphological algorithm for improving radio-frequency interference detection
• MOJAVE: Monitoring of Jets in AGN with VLBA Experiments - I. First-Epoch 15 GHz Linear Polarization Images
• The VLBA Calibrator Survey - VCS1
• The third realization of the International Celestial Reference Frame by very long baseline interferometry
• The VLBA Imaging and Polarimetry Survey at 5 GHz
• The Fourth VLBA Calibrator Survey - VCS4
• Single-epoch VLBI imaging study of bright active galactic nuclei at 2 and 8 GHz
• AUTO-MULTITHRESH: A General Purpose Automasking Algorithm
• Parsec-scale properties of steep and flat spectrum extragalactic radio sources from a VLBA survey of a complete north polar cap sample