AIPS HELP file for SETJY in 31DEC09
As of Sat Nov 21 23:54:52 2009
SETJY: Task to enter source info into source (SU) table.
INPUTS
INNAME Input image name (name)
INCLASS Input image name (class)
INSEQ 0.0 9999.0 Input image name (seq. #)
INDISK 0.0 9.0 Input image disk unit #
SOURCES Sources to modify.
QUAL -10.0 Source qualifier -1=>all
BIF 0.0 Low IF # for flux density
EIF 0.0 High IF # for flux density
ZEROSP I,Q,U,V flux density (Jy)
OPTYPE ' ' => use other adverbs
for required operation
'CALC' => determine
3C286/3C48/1934 fluxes from
standard formulae
'REJY' => reset source
fluxes to zero.
'REVL' => reset velocity
to zero
'RESE' => reset fluxes &
velocities to zero.
CALCODE New calibrator code:
'----' => change to blank
SYSVEL Velocity of source (km/s)
RESTFREQ Line rest frequency (Hz)
VELTYP Velocity type 'LSR,'HELIO'
VELDEF Velocity definition 'RADIO',
'OPTICAL'
FREQID FQ table entry to use for
velocity information and
'CALC' option
APARM (1): Pixel to which SYSVEL
refers ( 0=>1)
(2): Only for 'CALC' option:
<= 0 => use latest VLA
values (1999.2) or,
for 1934-638, the
ATCA value of 30Jul94.
1 => use Baars values
or old ATCA/PKS values
for 1934-638
2 => use VLA 1995.2
values or for 1934-638
the ATCA value of
30Jul94.
>= 3 => use oldest VLA
values (1990) or,
for 1934-638, the
ATCA value of 30Jul94.
(3): Only for 'CALC' option:
multiply the calculated
fluxes by APARM(3) with
0 -> 1
HELP SECTION
SETJY
Task: SETJY enters source information into the source (SU) table. If
a model for the source is available, it should tell you. These
models may be read with CALRD. CALIB scales the models to the
total flux in the SU table, so this must be set for the actual
observing frequency with SETJY even when models are used.
CALIB now uses the "V polarization" flux when calibrating RR
(= I + V) and LL (= I - V) correlators. This may be used for
instruments with circular polarization if the calibrator is
circularly polarized (not usually significant). It may also be
used with equatorially mounted instruments having linearly
polarized feeds. Such feeds do not rotate with parallactic
angle and so have XX = I-Q and YY = I+Q. To calibrate these
instruments, relabel the Stokes from (-5 to -8) to (-1 to -4)
and put minus the Q flux into the V position (ZEROSP(4)).
Some users have models for sources other than those provided
with AIPS. To use such a model, it is recommended that you
first run SETJY to set some total flux in the SU table. Then
the model will be scaled to that flux and GETJY may be used to
adjust that scale after CALIB. If you do not set a non-zero
flux for such calibrators, CALIB will use the flux contained in
the model but GETJY will assume 1.0 and the result after GETJY
will be erroneous.
Adverbs:
INNAME.....Input image name (name). Standard defaults.
INCLASS....Input image name (class). Standard defaults.
INSEQ......Input image name (seq. #). 0 => highest.
INDISK.....Disk drive # of input image. 0 => any.
SOURCES....The list of sources. '*' = all; a "-" before a
source name means all except ANY source named.
All ' ' =>all.
QUAL.......Only sources with a source qualifier number in the
SU table matching QUAL will be modified if QUAL is
not -1.
BIF........The lowest IF number for which the given flux
densities are valid. 0 => 1.
EIF........The highest IF number for which the given flux
densities are valid. 0 => all.
ZEROSP.....The I, Q, U, and V flux densities in Jy. If OPTYPE=' ',
ZEROSP is used to set the fluxes of all 4 polarizations
unless all 4 are zero - use REJY to do that. If
ZEROSP(1) < 0, then the I polarization flux is not
altered. This allows you to CALC the I flux and set the
Q, U, and V fluxes.
OPTYPE.....' ' => use ZEROSP values for the source flux
densities and SYSVEL for source velocity.
'CALC' => use the standard Baars et al formulae
and frequency information in the header to
determine the flux densities of the primary
calibrators 3C286, 3C48 and 3C147 (IAU style
names in B1950 or J2000 are also recognized
by SETJY). Any selected sources with a
recognized name will have fluxes calculated.
Australia Telescope source 1934-638 is also
recognized (J2000 only but can start with P).
(see APARM(2) for polynomial selection).
'REJY' => reset source flux densities to zero
for source(s) specified.
'REVL' => reset velocity to zero for source(s)
specified.
'RESE' => do both 'REJY' and 'REVL' operations.
CALCODE....The 4 character calibrator code to be inserted.
' ' => no change, '----' => change to blank,
'*' is not allowed.
NOTE that CALCODE is not part of the source
selection in SETJY as it is in other tasks.
SYSVEL.....The velocity of the source (in km/s)
per IF.
0 => no change. If 0 is desired use 1.0E-10.
RESTFREQ...Rest frequency of line (Hz) per IF; the value used
is the sum of RESTFREQ(1)+RESTFREQ(2).
0=>no change
VELTYP.....Velocity system ('LSR','HELIO'); ' '=> no change.
VELDEF.....Definition of velocity, 'RADIO' or 'OPTICAL';
' ' = > no change.
FREQID.....Frequency identifier to select (you may determine
which is applicable from the OPTYPE='SCAN' listing
produced by LISTR). This is needed to set the
frequency for flux computations in CALC OPTYPE.
It is also needed to estimate the width of a line
channel in km/s for calculation of velocity info.
SET IT on CALC.
APARM......(1) The frequency pixel (or channel) to which the
velocity refers. (0=>1)
The velocity stored in the 'SU' table will be
recalculated to refer to the reference pixel.
(2): Only for 'CALC' option:
<= 0 => use latest VLA values (1999.2) or,
for 1934-638, the ATCA value of
30Jul94.
1 => use Baars values or old ATCA/PKS
values for 1934-638
2 => use mid-1990s VLA determined values
(1995.2) or, for 1934-638, the ATCA
value of 30Jul94.
>= 3 => use oldest VLA determined values
(1990) or, for 1934-638, the ATCA
value of 30Jul94.
(3): Only for 'CALC' option:
You may wish to reduce the "official" flux computed
from the VLA measurements to account for resolution
effects. If 0 < APARM(3) <= 2.0, the computed flux
is multipled by APARM(3).
EXPLAIN SECTION
SETJY: Enter Source Flux Density and Calcode into the SU Table.
Other source parameters may also be entered.
RELATED PROGRAMS: CALIB
PURPOSE
The flux density scale of radio interferometers is often determined by
observations of radio sources of known brightness. For interferometer
observations, it is important that the standard sources used for this
purpose be relatively compact. This is often at odds however with the
requirement that the sources have very low variability over long
timescales.
For calibration of observations with the VLA, the radio sources 3C48,
3C286 and 3C147 are often used. In the southern hemisphere 1934-638
may also be used for this purpose.
The standard reference for the flux density of bright radio sources
is the paper by Baars, Genzel, Pauliny-Toth, Witzel 1977, Astron.,
Astrop. volume 61, page 99. The flux density of the standard sources
can be modelled as a polynomial expansion over frequency. Polynomial
coefficients have also been derived independently by R. Perley and
G. Taylor as part of a long-term program to monitor the standard flux
density calibrators at the VLA. These flux densities have been tied to
3C295 as it is believed that the bulk of the emission from 3C295
should remain constant over a timsecale of thousands of years.
SETJY will calculate the expected flux density of the standard
calibrators using either the Baars etal. coefficients or those derived
from the VLA observations in 1990, 1995.2, or 1999.2. This option is
selected by setting OPCODE to 'CALC'. The coefficient set to be used is
selected using APARM(2), with the default giving the 1999.2 values.
** NOTE 1: As of the end of 2000, there still is uncertainty in
the absolute VLA flux scale at 43 GHz, with the planets and NGC 7027
giving results that are discrepant by roughly 10 percent. For further
information, consult the VLA Observational Status Summary, available
via the VLA web site at http://www.vla.nrao.edu/
** NOTE 2: It was discovered several years ago that the existing 1990 VLA
coefficients were rounded incorrectly in SETJY, introducing a positive
bias of approximately 0.5 percent, 0.9 percent, 1.2 percent, 1.4 percent and 2.0 percent at P, L, C, X
and U bands respectively for 3C286. The effect for other sources is
less significant. This error affected AIPS versions up to and
including 15JAN96. The 1990 coefficients implemented in subsequent
versions have been corrected to remove the rounding error.
For more detailed information regarding the variability of the
standard flux density calibrators at the VLA the user is referred to
the VLA calibrator manual which is available on the WWW at
http://www.nrao.edu/doc/vla/html/calib.shtml.
The source 1934-638 is the primary calibrator for the ATCA (Australia
Telescope Compact Array). The flux density scale for 1934-638 was
re-determined by John Reynolds (jreynold@atnf.csiro.au, 30/jul/94) and
implemented in SETJY as the default on 30 August 1994. Changes in the
flux density scale are significant at all frequencies. The old scale
can be obtained with OPTYPE='CALC' by setting APARM(2)=1
Frequency New - Old
(MHz) ( percent)
408 -1.9
843 -3.5
1380 -7.9
1413 -8.1
1612 -9.3
1660 -9.5
1665 -9.5
2295 -11.4
2378 -11.5
4800 -7.9
4835 -7.8
4850 -7.8
8415 +8.5
8420 +8.5
8640 +9.8
The SETJY output in the SU table can be viewed with the tasks
LISTR or PRTAB.
There are now models of some calibrator sources shipped with AIPS.
These models are read in with the task CALRD. Available models are
OBJECT BAND
3C48 K
3C48 Q
3C48 U
3C138 K
3C138 Q
3C138 U
3C147 K
3C147 Q
3C147 U
3C286 K
3C286 Q
3C286 U
The above were all taken from Claire Chandler's web site although the
history files have been removed and the images cropped.
Note, to use these as calibrators, you must enter a total flux in the
source table with SETJY or GETJY which is correct for your observing
frequency. Then CALIB will scale the flux in these models to that
total flux.
These models are in J2000 coordinates. If your data are in B1950,
either change the uv data to J2000 with UVFIX or change the images to
B1950 with EPOSWTCH.