VLA Calibrator Manual
Note: this is an obsolete page. For the
most up to date information see the
VLA Observational Status
Summary,
VLA Observing Guide, and
the
VLA
Calibrator List.
The version of the VLA Calibrator Manual presented here is the most
up-to-date, and we are adding to it continually. At the moment it
contains 5523 entries for a total of 1860 sources. If
you know of a good calibrator that isn't in this list (especially at
low galactic latitudes) please contact mclausse@nrao.edu.
You can now
search the Calibrator Manual around a region of interest.
Contents
Chapter 1. About the 2003 calibrator manual
Chapter 2. Flux Density Calibration
- 2.1 The Flux Density Scale used at the VLA
- 2.2 Monitoring of Flux Density Calibrators
- 2.3 Accurate Flux Density Bootstrapping
Chapter 3. Phase, Gain, Position and Polarization Calibration
- 3.1 Hints and Strategies for Successful Phase Calibration
- 3.2 Coordinate Systems at the VLA
- 3.3 Planning for good Polarization Calibration
Chapter 4. VLA Calibrators
- 4.1 The Key to the Calibrator Manual
- 4.2 The List of Calibrators (720kB)
Appendix A. High-Frequency (22 or 43 GHz) Data
reduction at the VLA -- AIPS Cookbook Appendix D
Appendix B. Low-Frequency
(74 or 330 MHz) Data reduction at the VLA -- Kassim & Perley
Appendix C. Hot List of Calibrators Needing Re-observation
The VLA Calibrator Manual is also available in postscript format (378kB). A plain text version (without links to figures)
can be found in this
ftp site under the name csource.mas. Finally, a
gzipped copy of the plain text version
is available (75kB).
We are working towards
combining the VLA and VLBA calibrator databases and providing
new and better tools to access the joint database. The plan
is to design a much-improved calibrator finding tool that
will also work for the EVLA and ALMA telescopes. Take a look
at our
calibrator specifications page. Please send any
comments to mclausse@nrao.edu.
We have begun a VLA polarization
monitoring program for ~10 compact calibrators, primarily to enable
better calibration of the VLBA. Each source is observed about once a
month and reduced semi-automatically. The preliminary results are
described in the
VLA/VLBA Polarization Calibration Page.
Positions for 950 sources were
refined on Aug. 28 2001 using the VLBA Calibrator Survey observations
as reduced by the NASA Goddard Space Flight Center Geodesy group with
the Calc/Solve package. These positions have typical positional
errors less than 1 milliarcsec (see Johnston et al 1995, AJ 110, 880;
and Beasley et al. in prep).
This database is also the primary source of positions for the VLBA
correlator. Two sources, J0259+425 and J2307+148 thought to have
positions good to less than 50 mas, were discovered to be in error by
more than 200 mas.
A tutorial for
new users of the 74 and 330 MHz systems at the VLA has been written
up by Namir Kassim & Rick Perley. It is available from
http://lwa.nrl.navy.mil/tutorial/tutorial_main.html.
The Iridium constellation of
satellites has begun transmitting almost continuously at 1622 MHz.
This has serious consequences for 1612 MHz OH observations at the VLA, and
also for continuum observations near 1622 MHz. For instructions on
how to invoke a special set of front end filters to mitigate RFI
see this
Guide to the 18cm Front End Filters.
For more details about the interaction of the VLA with the Iridium
see this
notice on calibration in the presence of the Iridium constellation
for more details.
The flux densities calculated by
SETJY for 3C286 using the coefficients determined in 1990 were
systematically in error by 0.7 -- 1.7% in AIPS versions up to and
including 15JAN96. See the SETJY bug
notice for more details. The overall description of the flux
density calibration scheme used at the VLA is described in Chapter 2.
Other useful places to look:
The JVAS
catalog currently includes a
list of 2118 compact radio sources in the northern sky (above 0
degrees declination, and with |b|>2.5 degrees). These have all been
observed at 8.4 GHz with the VLA in A configuration. Position errors
currently range from 12 - 55 mas, but see the entry on the VLBA
calibrator survey below. Work is also in progress to extend the sample
to -30 degrees declination.
The VLBA Calibrator Survey is an ongoing project to provide
phase-reference calibrators for VLBA experiments. When completed
it will contain astrometric (~1 mas) positions and 2.7/8 GHz
images of the ~3000 sources in the JVAS catalog.
The VSOP
5 GHz Continuum Survey The Pre-launch VLBA observations
comprise 374 strong flat-spectrum radio sources north of
declination -44 imaged with the VLBA in June 1996. The site
contains VLBA images at ~2 mas resolution and accurate
positions for a good number of VLA and VLBA calibrators.
The Radio Optical
Reference Frame at USNO. This site contains VLBI images and very
accurate coordinates for over 400 sources including
a number of good VLA and VLBA calibrators.
The CJPR VLBI source archive at Caltech. This site contains images of
over 300 VLBI sources at declinations > 35 degrees observed in the
Pearson-Readhead and Caltech-Jodrell Bank surveys. Many of these sources
are excellent calibrators for the VLA and VLBA.
The VLBA 2 cm
survey by Kellermann, Zensus, Vermeulen and Cohen. This site
contains images of 132 sources obtained in 1 hour snapshots during
multiple epochs. Many of these sources are excellent calibrators for
the VLA and VLBA.
Modified on
Saturday, 21-May-2016 16:26:52 MDT
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