INNAME Input name(name). INCLASS Input name(class). INSEQ 0.0 9999.0 Input name(seq. #). 0=>high INDISK 0.0 4.0 Input disk drive #. 0=>any OUTNAME Output name(name). OUTCLASS Contains a string of numbers (0-3) indicating which moments are wanted. blank => '012' OUTSEQ -1.0 9999.0 Output name(seq. #). 0=>highest unique. OUTDISK 0.0 4.0 Output image disk drive # 0=>highest with room. BLC 0.0 2048.0 Bottom left corner of image 0=>entire image TRC 0.0 2048.0 Top right corner of image 0=>entire image FUNCTYPE Smoothing functions to be used for blanking; 1st char refers to velocity coord: B:box, H:Hanning; 2nd char refers to spatial coords: B:box, G:Gaussian. CELLSIZE 0.0 25.0 Width of smoothing functions: 1st element: velocity coord 2nd element: spatial coords Allowed ranges: Vel. B/H: odd integer 1-25 Spat. G: real 0.5-6.0. B: odd integer 1-11 FLUX Use only data > FLUX ICUT Use only data > in abs value than ICUT (> 0). Use only data < in abs value than ICUT (< 0.). PBPARM Beam parameters: (1) Cutoff: 0 -> no PB corr (2) > 0 -> Use (3)-(7) (3)-(7) Beam shape

MOMNT Type: Task Use: MOMNT does profile analysis on spectral line data. It calculates profile moments 0 to 3 from n-dimensional maps (2TO BE 'VE', 'FR', or 'CH'; a subimage may be selected. The decision on whether or not to include a particular point in the moment calculation is made by comparing the smoothed/averaged intensity at that point with FLUX and ICUT. The smoothing/averaging is done in three dimensions, with a choice of Boxcar or Hanning for the velocity coordinate, and Boxcar or Gaussian for the spatial coordinates (specified by FUNCTYPE). The size of the convolving kernel is given by CELLSIZE and has to be an odd integer, except for the Gaussian where it specifies the FWHM of the kernel; in this case the size of the kernel is 2*CELLSIZE(2)+1. The maximum kernel size for velocity is 25, for the spatial coordinates 11. The kernel sizes are adjusted to the nearest extremum if they are out of bounds. The subimage size is adjusted for the spatial kernel size, if necessary. The program makes an effort to minimize the I/O; if (TRC(1)-BLC(1)+1+CELLSIZE(1)) * CELLSIZE(2) * (TRC(2)-BLC(2)+1+CELLSIZE(2)) > 4000000 the execution time will about double because of a huge increase in I/O (corners and kernel sizes adjusted, of course). For FLUX try a value in the range 1.5 to 4 * RMS / SQRT (A * B) where: A = CELLSIZE(1) for velocity Boxcar = (CELLSIZE(1)+1)/2 for velocity Hanning B = CELLSIZE(2)**2/(B1*B2) for spatial Boxcar = CELLSIZE(2)**2/(B1*B2) + 1 for spatial Gaussian B1 = major axis FWHM of input map beam (in pixels) B2 = minor axis FWHM of input map beam (in pixels) RMS = r.m.s. noise in input map The units of the first input axis must be m/s, Hz, or channel number. XMOM is similar to MOMNT but does not do any smoothing before the clipping. ************************************************************* MOMNT now (2003-06-01) finally handles magic-value blanks. Using REMAG to convert blanks to zero and then smoothing with them is not correct and is no longer required. ************************************************************* Users should be aware that the image of the first moment is in single-precision floating point. If the first axis is frequency, there may be not be enough accuracy to represent the variation in frequency about some very high central frequency. The task will subtract the central value from the image of the first moment whenever the difference in the axis values from one end to the other is < 10**-3 of the central value. NOTE: THIS PRODUCES AN INCORRECT FIRST MOMENT SINCE AIPS HEADERS NO LONGER SUPPORT THE CONCEPT OF A BIAS AND SCALE. Adverbs: INNAME.....Input name (name): Standard defaults. INCLASS....Input name (class); Standard defaults. INSEQ......Input name (sequence number); 0 => highest. INDISK.....Input disk unit number; 0 => any. OUTNAME....Output name (name): Standard defaults. OUTCLASS...Contains a string of numbers (0-3) indicating which moments are wanted (e.g., '0123' or '301'); N.B. blank => '012'. The actual OUTCLASSes of the images will be 'MOM0','MOM1','MOM2',and 'MOM3'. OUTSEQ.....Output name (sequence number); 0 => highest unique. OUTDISK....Output disk unit number; 0 => highest w room. BLC........Bottom left corner of subimage; 0: bottom left corner of entire image TRC........Top right corner of subimage; 0: top right corner of entire image FUNCTYPE...Smoothing functions to be used for blanking; first character refers to velocity coordinate: B:box, H:Hanning (default B); second character refers to spatial coordinates: B:box, G:Gaussian (default B). CELLSIZE...Width of smoothing functions; first element: velocity coordinate; allowed range: B/H: odd integer 1 - 25 (<= 0 => 3); second element: spatial coordinates; allowed ranges: B: odd integer 1 - 11 (<= 0.0 => 5), G: real 0.5 - 6.0 (<= 0.0 => 2.0). FLUX.......A flux cutoff in the same units as the input image (i.e. Jy/beam). Data values below FLUX in the smoothed image are ignored in the moment computation. NOTE that 0.0 is not a null value. Instead, it means ignore all negative brightnesses. ICUT.......A flux cutoff in the same units as the input image (i.e. Jy/beam). When ICUT > 0.0, data values in the smoothed image less in absolute value than ICUT are ignored. When ICUT < 0.0, data values in the smoothed image greater in absolute value than ICUT are ignored. NOTE that ICUT and FLUX are both always used. PBPARM.....Primary beam parameters: Adjust the cutoff levels to account for the primary beam. (1) Lowest beam value to believe: 0 -> do not do a primary beam correction. The maximum correction is a factor of 100. (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

MOMNT has the option of scaling the cutoff values on a pixel-by-pixel basis to "correct" for the primary beam. Thus, as the beam value goes down the cutoff value goes up. This allows MOMNT to be run on data cubes after the application of PBCOR. Since the primary beam is a function of frequency, the spectral moments are affected by the primary beam correction. Unfortunately this correction also raises the noise, making the option to raise the cutoff useful. MOMNT 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

1.285 -1.329E-3 6.445E-7 -1.146E-10 * 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.