AIPS NRAO AIPS HELP file for BOXES in 31DEC18



As of Fri Nov 16 15:21:54 2018


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 #
SOURCES                            Source selected
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 facets
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.

AIPS