AIPS HELP file for BOXES in 31DEC24
As of Tue Apr 23 9:00:00 2024
BOXES: Task to make a BOXFILE for input to IMAGR
INPUTS
INNAME UV dataset name (name)
INCLASS UV dataset name (class)
INSEQ 0.0 9999.0 UV dataset name (seq. #)
INDISK 0.0 9.0 Disk drive #
SRCNAME Source name
BOXFILE
disk file to read field locs
and Clean boxes
OBOXFILE
output file to incl field
locs and Clean boxes
CELLSIZE 0.0 (X,Y) size of grid in asec
IMSIZE 0.0 16384 field size
NFIELD 0.0 4096. Number of f
RASHIFT RA shift per field (asec)
DECSHIFT DEC shift per field (asec)
FLUX 0.0 Minimum component flux
(source * beam)
BPARM (1) Radius of box pixels
(2) Box scale if width > 0
(3) Factor to scale NVSS
fluxes, 0 -> 1
(4) > 0 -> keep old boxes
(5) Max field # to use
PBPARM Beam parameters:
(1) Cutoff 0 -> 0.023
(2) > 0 -> Use (3)-(7)
(3)-(7) Beam shape
INLIST
NVSS input file name
' ' => AIPS provided.
HELP SECTION
BOXES
Type: Task
Use: BOXES creates Clean boxes containing all NVSS (or WENSS or ??)
sources > n milliJy that would fall in the images specified by
the input data file and BOXFILE. The survey flux of each
source is multiplied by the single-dish beam pattern out to a
specified cutoff.
Adverbs:
INNAME......The UV dataset name (name). Standard defaults.
INCLASS.....The UV dataset name (class). Standard defaults.
INSEQ.......The UV dataset name (seq. #). 0 => highest.
INDISK......The disk drive #. 0 => any.
SOURCES.....The source to be used from a multi-source file; a single
source name is required to get the central pointing
position from the source table. Ignored for single-source
files.
BOXFILE.....Input text file containing field coordinates. No real
default, ' ' => that there is none. In that case,
NFIELD, RASHIFT, and DECSHIFT specify fully the field
locations. Otherwise, the task starts with these adverb
values and overrides them following the information in
BOXFILE.
OBOXFILE....Output box file contains BOXFILE (with or without the
previous Clean boxes) plus Clean boxes around sources.
No default and may not pre-exist.
CELLSIZE....Pixel size for the fields in IMAGR in arc seconds.
IMSIZE......Size of each field.
NFIELD......The number of fields to map in the antenna beam. Up to
4096 are allowed. 0 -> set by max field in BOXFILE
and/or bPARM(5). Note that only 64 fields may be
described in adverbs, but 4096 are allowed. If you want
to set Clean boxes in advance for more than the first
field, or wish to specify RASHIFT, DECSHIFT, FLDSIZE, or
BCOMP for fields > 64, you must use the BOXFILE option.
RASHIFT.....RA shift of the phase center of each field from the
tangent point of the uv data in asec. Map center =
tangent point + shift. If X>0 shifts map center to east.
NOTE: RASHIFT is a shift in RA scaled by cos (Dec_0) as
Ra_new(i) = RA_0 + RASHIFT(i) / cos (Dec_0)
where _0 => the tangent point in the uv data. This is a
change for 15OCT99 from shifts in -SIN projection (which
do not work for -NCP data and large angles). If the UV
data have been rotated then RASHIFT and DECSHIFT refer
to X and Y in the new coordinate system.
DECSHIFT....Declination shift of map center from tangent point of
each field in asec. Map center = tangent point + shift.
If Y>0 shifts map center to north.
FLUX........Minumum included component "flux" = source flux times
the single-dish beam power. 0 => any in INLIST.
Fluxes are read from the table, scaled by BPARM(3), and
then compared to FLUX.
BPARM.......(1) Clean boxes are circles of BPARM(1) pixels radius
when there is no source width parameter given in
INLIST for the particular source. The NVSS and
WENSS tables provided do not show widths. <= 1 -> 3
(2) When a width parameter is provided (e.g. from MFPRT)
for a source in INLIST, the Clean box is then made a
circle of radius = BPARM(2) times the source FWHM
(converted to pixels). <= 0 -> 1.5.
(3) Factor to scale NVSS fluxes (to account for spectral
index on average). 0 -> 1
(4) > 0 => keep all Clean boxes found in the input.
<= 0 => keep only Clean boxes for fields numbered >
BPARM(5)
(5) Max field number to consider: 0 -> 4096. All fields
are copied to OBOXFILE but only those numbered <=
BPARM(5) are altered.
PBPARM......Primary beam parameters:
(1) Lowest beam value to believe: 0 -> 0.023 Sources
outside this range are ignored.
(2) > 0 => Use beam parameters from PBPARM(3)-PBPARM(7)
Otherwise use default parameters for the VLA (or
ATCA where appropriate)
(3-7)..For all wavelengths, the beam is described by the
function:
1.0 + X*PBPARM(3)/(10**3) + X*X*PBPARM(4)/(10**7) +
X*X*X*PBPARM(5)/(10**10) + X*X*X*X*PBPARM(6)/(10**13)
X*X*X*X*X*PBPARM(7)/(10**16)
where X is (distance from the pointing position in arc
minutes times the frequency in GHz)**2.
See Explain for details and defaults
INLIST......Catalog input file name. For format see Explain
' ' => AIPS-provided file with 237600 objects, either
'AIPSTARS:NV00.0030' for J2000 or 'AIPSTARS:NV50.0030'
for B1950. Other AIPSTARS: files available are
Epoch 2000:
FLUX >= 1.000 NV00.1000 ( 2267 objects)
FLUX >= 0.300 NV00.0300 ( 14456 objects)
FLUX >= 0.100 NV00.0100 ( 63411 objects)
FLUX >= 0.030 NV00.0030 (237600 objects)
Epoch 1950:
FLUX >= 1.000 NV50.1000 ( 2267 objects)
FLUX >= 0.300 NV50.0300 ( 14456 objects)
FLUX >= 0.100 NV50.0100 ( 63411 objects)
FLUX >= 0.030 NV50.0030 (237600 objects)
The WENSS/WISH surveys ar also available $AIPSTARS as
FLUX >= 0.100 WE00.0100 ( 99709 object 2000)
FLUX >= 0.100 WE50.0100 ( 99709 object 1950)
Some sites may choose to download really large source
lists to deeper flux levels. These may include from the
NVSS survey:
FLUX >= 0.003 NV00.0003 (1560007 objects, 2000)
FLUX >= 0.003 NV50.0003 (1560007 objects, 1950)
and the WENSS/WISH survey:
FLUX >~ 0.010 WE00.0000 (319770 objects, 2000)
FLUX >~ 0.010 WE50.0000 (319770 objects, 1950)
These deep files may be particularly useful for BOXES.
Note: the WENSS survey covers +90 to +28 degrees
declination and the WISH survey covers -25 to -15 with
some sources to -9.
EXPLAIN SECTION
BOXES: Task to make Clean boxes from the NVSS (or WENSS or ??)
DESCRIPTION
The task creates Clean boxes for all fields in BOXFILE. The NVSS or
other source catalog is then searched for all sources which would fit
in these images within the primary or single-dish beam. Those sources
that fit in one or more of the images are added to those images.
In order to do all this, the position (RA,DEC) of the pointing phase
center is required. This is obtained from the input UV data set. In
the case of a single-source data set, it is read from the header. In
the case of a multi-source data set, the source must be specified in
the first element of the adverb SOURCES, and the position is read from
the SU extension. The selection of sources is by the adverb BPARM(3)
and FLUX. The source catalog may be specified in INLIST or you may
use one of the AIPS-provided versions of the NVSS or WENSS. The
format of the file is:
All lines beginning with a semi-colon are ignored. They are the
copyleft, a descriptive text in the AIPS files, and other comments.
Be careful about the epoch of the coordinates.
Remaining give the Right ascension in degrees, Declination in degrees,
Flux in mJy, and optionally a FWHM in arc seconds using format
F9.5,1X,F9.5,I7,F10.4. A sample is given below (a width is shown
although the actual NVSS files provided by AIPS have no widths).
0.08521 55.65239 1518 3.1234
0.22108 40.90052 1301
0.84166 -17.45316 2415
1.23802 12.80524 1071
1.37727 69.39949 1105
1.55780 -6.39310 2051
1.59416 -0.07363 3898
2.12217 -5.97935 1323
358.54728 32.91998 1183
358.59049 45.88455 1873
358.78961 49.83570 2306
358.97312 15.69069 1104
359.25280 -34.75882 1286
359.32748 14.76875 1020
359.38022 -11.42748 1814
359.64781 44.07789 1940
PRIMARY BEAM CORRECTION
BOXES corrects an image for the primary beam attenuation of
the antennas. The function used to model the primary beam for normal
VLA frequencies
F(x) = 1.0
+ parm(3) * 10E-3 * x
+ parm(4) * 10E-7 * x*x
+ parm(5) * 10E-10 * x*x*x
+ parm(6) * 10E-13 * x*x*x*x
+ parm(7) * 10E-16 * x*x*x*x*x
where x is proportional to the square of the distance from the
pointing position in units of [arcmin * freq (GHz)]**2, and F(x)
is the multiplicative factor to divide into the image intensity at the
distance parameter x. For other antennas, the user may read
in appropraite constants in PBPARM(3) through PBPARM(7). The
flag, PBPARM(2) must be set to a positive number to invoke this
option and PBPARM(3) must not be zero.
This correction scales with frequency and has a cutoff
beyond which the map values are set to an undefined pixel value GIVEN
in PBPARM(1). At the VLA frequencies the default cutoff is
1.485 GHz 29.8 arcmin
4.885 GHz 9.13 arcmin
15 GHz 2.95 arcmin
22.5 GHz 1.97 arcmin
and occurs at a primary beam sensitivity of 2.3 percent of the value at
the beam center. Corrections factors < 1 are forced to be 1.
The estimated error of the algorithm is about 0.02 in (1/F(x))
and thus leads to very large errors for x>1500, or at areas
outside of the primary response of 20 percent. The cutoff level
may be specified with DPARM(1).
Default values of PBPARM for the VLA are given by Perley's fits:
0.0738 GHz -0.897 2.71 -0.242
0.3275 -0.935 3.23 -0.378
1.465 -1.343 6.579 -1.186
4.885 -1.372 6.940 -1.309
8.435 -1.306 6.253 -1.100
14.965 -1.305 6.155 -1.030
22.485 -1.417 7.332 -1.352
43.315 -1.321 6.185 -0.983
For the ATCA, these are by default:
1.5 GHz -1.049 4.238 -0.8473 0.09073 -5.004E-3
2.35 -0.9942 3.932 -0.7772 0.08239 -4.429E-3
5.5 -1.075 4.651 -1.035 0.12274 -6.125E-3
8.6 -0.9778 3.875 -0.8068 0.09414 -5.841E-3
20.5 -0.9579 3.228 -0.3807 0.0 0.0
For the Karl G Jansky VLA ("EVLA"), the defaults are frequency
dependent. If the observing frequency is between two tabulated
frequencies, then the beam is computed for each of the tabulated
frequencies and then interpolated to the observing frequency. The
values used are far too numerous to give here, see EVLA Memo 195,
"Jansky Very Large Array Primary Beam Characteristics" by Rick Perley,
revision dated June 2016. Obtain it from
http://library.nrao.edu/evla.shtml
RICK PERLEY'S (OLD) REPORT
Polynomial Coefficients from LSq Fit to VLA Primary
Beam raster scans.
Functional form fitted:
1 + G1.X^2 + G2.X^4 + G3.X^6
where X = r.F,
and r = radius in arcminutes
F = frequency in GHz.
Fits were made to 3 percent cutoff in power for 24 antennas.
Poor fits, and discrepant fits were discarded, and the most
consistent subset of antennas had their fitted coefficients
averaged to produce the following 'best' coefficients.
Freq. G1 G2 G3
0.0738 -0.897E-3 2.71 E-7 -0.242E-10
0.3275 -0.935 3.23 -0.378
1.285 -1.329 6.445 -1.146 *
1.465 -1.343 6.579 -1.186
4.885 -1.372 6.940 -1.309
8.435 -1.306 6.253 -1.100
14.965 -1.305 6.155 -1.030
22.485 (old) -1.350 6.526 -1.090 *
22.485 (new) -1.417 7.332 -1.352
43.315 -1.321 6.185 -0.983
The estimated errors (from the scatter in the fitted
coefficients) are generally very small:
G1: .003 at all bands except Q (.014)
G2: .03 to .07 at all bands except Q (.15)
G3: .01 to .02 at all bands except Q (.04)
R. Perley 21/Nov/00
* The 1.285 and 22.485 old feed values are not used.