AIPS NRAO AIPS HELP file for FACES in 31DEC18



As of Mon Jul 23 9:27:26 2018


FACES: Makes images of catalog sources for initial calibration

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
OUTNAME                            Output file name
OUTDISK                            Output disk number
CELLSIZE        0.0                (X,Y) size of grid in asec
IMSIZE          0.0      16384     field size
SHIFT                              Position shift (RA,Dec) asec
                                   for all fields
BMAJ                               Clean beam FWHM in asec
FLUX              0.0              Minimum component flux
                                   (source * beam)
BPARM                              (1) Inner region radius (deg)
                                   (2) Field overlap in pixels
                                   (3) Factor to scale NVSS
                                       fluxes, 0 -> 1
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

FACES
Type:  Task
Use:   FACES creates (mostly empty) images and CC files containing all
       NVSS (or WENSS or ??) sources > n milliJy that would fall in
       the images.  The survey flux of each source is multiplied by
       the single-dish beam pattern out to a specified cutoff.
       Sources beyond this point are not included.
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.
  OUTNAME.....Name field (12 characters) of output files.  ' ' =>
              INNAME.  The OUTCLASS is IMOnnn for filed number nnn.
              The OUTSEQ for field 1 is 0 and that OUTSEQ is used for
              all other fields.
  OUTDISK.....Output file disk number.
  CELLSIZE....Pixel size for the fields in IMAGR in arc seconds.
  IMSIZE......Size of each field.
              If CELLSIZE and/or IMSIZE are zero, the data are read to
              find the maximum baseline and maximum W in order to
              estimate these parameters.
              NOTE: FACES may write out only 512 fields but is willing
              to try as many as 20 times that number.  Only those
              fields which have sources will be written.  So IMSIZE
              may be smaller than one would use with SETFC and IMAGR.
  SHIFT.......Specifies a position shift in arc seconds at the phase
              center for all of the fields in the inner portion.  The
              output RA = RA0 + SHIFT(1)/cos(DEC0) and DEC = DEC0 +
              SHIFT(2) where 0 refers to the input coordinates.
  BMAJ........Clean beam FWHM in arc seconds.  0 -> 3 * CELLSIZE(1)
  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) The radius in degrees to be covered fully by
                  overlapping fields.
              (2) Field overlap in pixels 0 -> 5.
              (3) Factor to scale NVSS fluxes (to account for spectral
                  index on average).  0 -> 1
  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
              but may be too deep to be of use here.
              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

FACES:  Task to make images from the NVSS (or WENSS or ??)

                        DESCRIPTION

The task creates images matching the Fly's eye portion of the fields
that would be found by SETFC.  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.  They are also added to
the CC file of the field closest to them.

These images and the CC files may be used as a model for the area
observed.  The CC sources will not lie on grid cells.  The CC model
may be used only with CMETHOD = 'DFT'.

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 adverbs
BPARM(3), and BPARM(5-10).  See their description above.   The source
catalog may be specified in INLIST or you may use one of the
AIPS-provided versions of the NVSS.  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 no width is shown
since none are used by FACES.

  0.08521  55.65239   1518
  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

     FACES 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