THE CELESTIAL REFERENCE FRAME AT 24 AND 43 GHz. I. ASTROMETRY

Lanyi, G. E.; Boboltz, D. A.; Charlot, P.; Fey, A. L.; Fomalont, Edward B.; Geldzahler, B. J.; Gordon, D.; Jacobs, C. S.; Ma, C.; Naudet, C. J.; Romney, J. D.; Sovers, O. J.; Zhang, L. D.

doi:10.1088/0004-6256/139/5/1695

Cited by 48 publications

(46 citation statements)

References 20 publications

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“…There were only several VLBI surveys at frequencies higher than 24 GHz. Lanyi et al (2010) observed 132 sources at Q-band in 2002-2003, Marscher et al (2012 run an ongoing project of monitoring 34 AGNs since 2007, and Jacobs & Sovers (2009) started to work on the catalog of ∼ 300 objects at 32 GHz that will become available in the future. Considering that 13 sources overlap in both projects, the total number of sources with known Q-band flux densities at milliarcsecond scales with their brightness distributions publicly available is 153.…”

Section: Introduction the Korean Vlbi Network (Kvn) Is The First Dedimentioning

confidence: 99%

EARLY SCIENCE WITH THE KOREAN VLBI NETWORK: THE QCAL-1 43 GHz CALIBRATOR SURVEY

Petrov¹,

Lee

Kim

et al. 2012

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This paper presents the catalog of correlated flux densities in three ranges of baseline projection lengths of 637 sources from a 43 GHz (Q-band) survey observed with the Korean VLBI Network. Of them, 14 objects used as calibrators were previously observed, but 623 sources have not been observed before at Q−band with very long baseline interferometry (VLBI). The goal of this work in the early science phase of the new VLBI array is twofold: to evaluate the performance of the new instrument that operates in a frequency range of 22-129 GHz and to build a list of objects that can be used as targets and as calibrators. We have observed the list of 799 target sources with declinations down to −40• . Among them, 724 were observed before with VLBI at 22 GHz and had correlated flux densities greater than 200 mJy. The overall detection rate is 78%. The detection limit, defined as the minimum flux density for a source to be detected with 90% probability in a single observation, was in a range of 115-180 mJy depending on declination. However, some sources as weak as 70 mJy have been detected. Of 623 detected sources, 33 objects are detected for the first time in VLBI mode. We determined their coordinates with the median formal uncertainty 20 mas. The results of this work set the basis for future efforts to build the complete flux-limited sample of extragalactic sources at frequencies 22 GHz and higher at 3/4 of the celestial sphere.

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Section: Introduction the Korean Vlbi Network (Kvn) Is The First Dedimentioning

confidence: 99%

EARLY SCIENCE WITH THE KOREAN VLBI NETWORK: THE QCAL-1 43 GHz CALIBRATOR SURVEY

Petrov¹,

Lee

Kim

et al. 2012

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“…The median increase was 28% and 42%, respectively. Removing EVN stations from the array would, of course, degrade the quality of images, but as analysis of other VLBA experiments, for instance, the K/Q survey (Lanyi et al 2010), showed the degradation would not be at a level that would undermine their usability for the goals of this specific project.…”

Section: Discussionmentioning

confidence: 97%

“…The data set that was used for the final parameter estimation utilized all dual-band S/X data acquired under absolute astrometry and space geodesy programs from 1980 April through 2010 December, including the data from the GC030 experiment-a total of 8 million observations. Thus, the GC030 experiment was analyzed exactly the same way as over 5000 other VLBI experiments, using the same analysis strategy that was used for processing prior observations for the ICRF, VCS, VGaPS, LCS, and K/Q survey (Lanyi et al 2010) catalogs. The estimated parameters are right ascensions and declinations of all sources, coordinates and velocities of all stations, coefficients of B-spline expansion of nonlinear motion for 17 stations, coefficients of harmonic site position variations of 48 stations at four frequencies: annual, semiannual, diurnal, semi-diurnal, and axis offsets for 67 stations.…”

Section: Discussionmentioning

confidence: 99%

The Catalog of Positions of Optically Bright Extragalactic Radio Sources Obrs-1

Petrov

2011

The Astronomical Journal

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It is expected that the European Space Agency mission Gaia will make it possible to determine coordinates in the optical domain of more than 500,000 quasars. In 2006, a radio astrometry project was launched with the overall goal of making comparisons between coordinate systems derived from future space-born astrometry instruments and the coordinate system constructed from analysis of global very long baseline interferometry (VLBI) more robust. Investigation of the rotation, zonal errors, and non-alignment of the radio and optical positions caused by both radio and optical structures is needed to validate both techniques. In order to support these studies, the densification of the list of compact extragalactic objects that are bright in both radio and optical ranges is desirable. A set of 105 objects from the list of 398 compact extragalactic radio sources with decl. > −10• was observed with the Very Long Baseline Array and European VLBI Network (EVN) with the primary goal of producing images with milliarcsecond resolution. These sources are brighter than 18 mag in the V band, and they were previously detected by the EVN. In this paper, coordinates of observed sources have been derived with milliarcsecond accuracies from analysis of these VLBI observations using an absolute astrometry method. The catalog of positions for 105 target sources is presented. The accuracies of source coordinates are in the range of 0.3-7 mas, with a median of 1.1 mas.

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“…However, VLBI calibrators at higher frequency (>20 GHz) are very rare compared to those at lower frequency. For example, 858 VLBI calibrators in the K band (∼20 GHz) are known Lanyi et al 2010;Petrov et al 2011Petrov et al , 2012Petrov 2012), while ∼3800 sources are listed in the VCS in the S and X bands. High-frequency VLBI observations are useful to understand the physical processes in the vicinity of supermassive black holes of active galactic nuclei (AGNs) because it enables studying the optically thin region from the synchrotron radiation of compact radio sources.…”

Section: Introductionmentioning

confidence: 99%

“…High-frequency VLBI observations are useful to understand the physical processes in the vicinity of supermassive black holes of active galactic nuclei (AGNs) because it enables studying the optically thin region from the synchrotron radiation of compact radio sources. In addition, radio sources become more compact in structure so that astrometric errors in the celestial reference frame (CRF) would be minimized (e.g., Fey & Charlot 1997;Ma et al 1998;Fey et al 2004;Charlot et al 2010;Lanyi et al 2010). Together with the successful operation of the Gaia spacecraft during the first two years of sky survey, high-frequency VLBI sources that match Gaia samples will be important to compare the radio and optical reference frames (e.g., Bourda et al 2010Bourda et al , 2011Jacobs et al 2014).…”

Section: Introductionmentioning

confidence: 99%

Korean VLBI Network Calibrator Survey (KVNCS). 1. Source Catalog of KVN Single-dish Flux Density Measurement in the K and Q Bands

Lee

Sohn

Byun

et al. 2017

ApJS

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We present the catalog of the KVN Calibrator Survey (KVNCS). This first part of the KVNCS is a single-dish radio survey simultaneously conducted at 22 (K band) and 43 GHz (Q band) using the Korean VLBI Network (KVN) from 2009 to 2011. A total of 2045 sources are selected from the VLBA Calibrator Survey with an extrapolated flux density limit of 100 mJy at the Kband. The KVNCS contains 1533 sources in the K band with a flux density limit of 70 mJy and 553 sources in the Q band with a flux density limit of 120 mJy; it covers the whole sky down to −32°.5 in decl. We detected 513 sources simultaneously in the K and Q bands; ∼76% of them are flatspectrum sources (−0.5 α 0.5). From the flux-flux relationship, we anticipated that most of the radiation of many of the sources comes from the compact components. The sources listed in the KVNCS therefore are strong candidates for high-frequency VLBI calibrators.

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THE CELESTIAL REFERENCE FRAME AT 24 AND 43 GHz. I. ASTROMETRY

Cited by 48 publications

References 20 publications

EARLY SCIENCE WITH THE KOREAN VLBI NETWORK: THE QCAL-1 43 GHz CALIBRATOR SURVEY

EARLY SCIENCE WITH THE KOREAN VLBI NETWORK: THE QCAL-1 43 GHz CALIBRATOR SURVEY

The Catalog of Positions of Optically Bright Extragalactic Radio Sources Obrs-1

Korean VLBI Network Calibrator Survey (KVNCS). 1. Source Catalog of KVN Single-dish Flux Density Measurement in the K and Q Bands

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