J/A+A/574/A73 LOFAR long baselines at 140MHz Calibrators (Moldon+, 2015)
Calibrators for LOFAR long baselines at 140 MHz.
Moldon J., Deller A.T., Wucknitz O., Jackson N., Drabent A., Carozzi T.,
Conway J., Kapinska A.D., McKean J.P., Morabito L., Varenius E., Zarka P.,
Anderson J., Asgekar A., Avruch I.M., Bell M.E., Bentum M.J., Bernardi G.,
Best P., Birzan L., Bregman J., Breitling F., Broderick J.W., Bruggen M.,
Butcher H.R., Carbone D., Ciardi B., de Gasperin F., de Geus E., Duscha S.,
Eislooffel J., Engels D., Falcke H., Fallows R.A., Fender R., Ferrari C.,
Frieswijk W., Garrett M.A., Griessmeier J., Gunst A.W., Hamaker J.P.,
Hassall T.E., Heald G., Hoeft M., Juette E., Karastergiou A.,
Kondratiev V.I., Kramer M., Kuniyoshi M., Kuper G., Maat P., Mann G.,
Markoff S., McFadden R., McKay-Bukowski D., Morganti R., Munk H.,
Norden M.J., Offringa A.R., Orru E., Paas H., Pandey-Pommier M., Pizzo R.,
Polatidis A.G., Reich W., Roottgering H., Rowlinson A., Scaife A.M.M.,
Schwarz D., Sluman J., Smirnov O., Stappers B.W., Steinmetz M., Tagger M.,
Tang Y., Tasse C., Thoudam S., Toribio M.C., Vermeulen R., Vocks C.,
van Weeren R.J., White S., Wise M.W., Yatawatta S., Zensus A.
<Astron. Astrophys. 574, A73 (2015)>
=2015A&A...574A..73M 2015A&A...574A..73M
ADC_Keywords: Interferometry ; Positional data ; Radio continuum ;
Radio sources ; Regional catalog ; Surveys ; VLBI
Keywords: instrumentation: high angular resolution -
instrumentation: interferometers - methods: observational -
techniques: interferometric - techniques: high angular resolution -
catalogs
Abstract:
An efficient means of locating calibrator sources for international
LOw Frequency ARray (LOFAR) is developed and used to determine the
average density of usable calibrator sources on the sky for
subarcsecond observations at 140MHz.
We used the multi-beaming capability of LOFAR to conduct a fast and
computationally inexpensive survey with the full international LOFAR
array. Sources were preselected on the basis of 325MHz
arcminute-scale flux density using existing catalogues. By observing
30 different sources in each of the 12 sets of pointings per hour, we
were able to inspect 630 sources in two hours to determine if they
possess a sufficiently bright compact component to be usable as LOFAR
delay calibrators.
Description:
We observed 630 sources with the LOFAR international baselines to
determine if they are compact enough to be delay calibrators. We used
information in other catalogs to determine their properties. The
quality factor (q) is a measure of they reliability of the source as a
potential calibrator. q=3 indicates good primary calibrators, q=2
indicates potentially good primary calibrators, and q=1 indicates
sources that are resolved or faint or both. All WENSS peak flux
densities in this paper include a correction factor of 0.9 with
respect to the original catalogue to place them in the RCB scale.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
lofarlb.dat 80 630 LOFAR sources observed
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See also:
VIII/65 : 1.4GHz NRAO VLA Sky Survey (NVSS) (Condon+ 1998)
VIII/62 : The Westerbork Northern Sky Survey (Leiden, 1998)
VIII/97 : 74MHz VLA Low-frequency Sky Survey Redux (VLSSr) (Lane+, 2014)
Byte-by-byte Description of file: lofarlb.dat
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Bytes Format Units Label Explanations
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1- 15 A15 --- Name Source name (WNBHHMM.m+DDMMA or JHHMM+DDMM)
17- 18 I2 h RAh Right ascension (J2000)
20- 21 I2 min RAm Right ascension (J2000)
23- 31 F9.6 s RAs Right ascension (J2000)
33 A1 --- DE- Declination sign (J2000)
34- 35 I2 deg DEd Declination (J2000)
37- 38 I2 arcmin DEm Declination (J2000)
40- 47 F8.5 arcsec DEs Declination (J2000)
49- 55 F7.1 mJy Fwenss ?=- Peak flux density in the WENSS catalogue
(330MHz, VIII/62)
57- 59 F3.1 mJy e_Fwenss ?=- Error of peak flux density in the WENSS
catalogue
61- 66 F6.1 mJy Fnvss ?=- Flux density in the NVSS catalogue
(1.4GHz, VIII/65)
69- 73 F5.1 mJy e_Fnvss ?=- Error of flux density in the NVSS catalogue
75- 78 F4.1 Jy Fvlss ?=- Flux density of VLSS catalogue
(74MHz, VIII/97)
80 I1 --- q [1/3] Quality factor, 3=good calibrator (1)
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Note (1): Quality factor as follows:
3 = good calibrator
2 = potential good calibrator
1 = resolved or faint source
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Acknowledgements:
Javier Moldon, moldon(at)astron.nl
(End) Javier Moldon, Patricia Vannier [CDS] 08-Dec-2014