[daip] [forwarded from Alice Argon] JMFIT problem

Fri Apr 7 16:03:03 EDT 2000

Any ideas?  OMFIT?  SAD?  XGAUS?

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From: Alice Argon <alice at rgalp2.harvard.edu>
To: pmurphy at NRAO.EDU
Subject: JMFIT problem
Date: Fri, 7 Apr 2000 14:07:00 -0400 (EDT)
Message-ID: <Pine.OSF.4.05.10004071335390.7501-100000 at rgalp2.harvard.edu>

Dear Pat,

I have some spectral line VLBA data which I imaged with a circular restoring 
beam (40x40 milliarcsec--only the desert SW remains).  I then tried to fit a 
Gaussian to each feature using JMFIT, but found that ALL the position angles 
of the fitted features are coming out to either 90 degrees or 0 degrees, 
exactly.  The vast majority are 90 degrees.  The 0 degree PA's occur in weak 
channels (of a given feature) and are always adjacent to 90 degree PA's.  
Below is a sample JMFIT output from a feature which when contoured appears to 
have a position angle of about 60 degrees.  I should mention that many of the 
contour plots appear to have position angles of around 90 degrees, but exactly 
90 degrees to three places after the decimal point and every single one of 
them?  It seems strange. Any idea as to what's going on?

Thanks,
 Alice Argon

- --------------------------------------------------------------------------------
JMFIT1: Task JMFIT  (release of 31DEC99) begins
JMFIT1:           CHANNEL  55.
JMFIT1: Fit to histogram gives RMS = 2.034E-02
JMFIT1: Model fit to G351-M00-5-R.RCLN  .   1
JMFIT1: Source= G351.78     Units are JY/BEAM
JMFIT1: X-ref pix= 512.0  RA 17 26 42.70300   pix sep (Asec) -0.0100
JMFIT1: Y-ref pix= 513.0  DEC -36 09 17.3700  pix sep (Asec)  0.0100
JMFIT1: Axes 3-7 pixels =     55      1      1      1      1
JMFIT1: Axis 3 : 1665.589 MHZ
JMFIT1: Axis 4 : RR
JMFIT1:  - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
JMFIT1: ******** Input Model ****************************************
JMFIT1: Component=  1  Gaussian
JMFIT1:       Peak= 3.6118E-01    JY/BEAM
JMFIT1:       Xpos=  601.00      Ypos=  325.00     pixels
JMFIT1:       Size=   4.00    x   4.00    Pixels at pa   0.00 ** deg
JMFIT1:       Component made 10% elliptical for better fitting
JMFIT1:                    ** Means parameter is held fixed
JMFIT1:  - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
JMFIT1:       Beam=   4.00    X   4.00    pixels: in PA    0.0    deg
JMFIT1: Initial guess RMS  1.2744E-01 in   49 usable pixels
JMFIT1: Fitting to   49 data points for  5 parameters
JMFIT1: Initial Chi-squared, R.M.S., and gradient norm:
JMFIT1:               7.95778E-01    9.71465E-03    6.21396E+00
JMFIT1: ***  Convergence achieved.
JMFIT1: Solution RMS  5.3841E-02 in   49 usable pixels
JMFIT1: Post-fit Chi-squared, R.M.S., and gradient norm:
JMFIT1:               1.42042E-01    5.68175E-02    1.41796E-04
JMFIT1: Writing MF file version  92 attached to input image
JMFIT1: ********* Solution from JMFIT *********************************
JMFIT1: Component   1-Gaussian
JMFIT1:   Peak intensity    = 3.5199E-01 +/-  1.88E-02 JY/BEAM
JMFIT1:   Integral intensity= 1.1036E+00 +/-  7.55E-02 JANSKYS
JMFIT1:   X-position        =    600.871 +/-   0.2043 pixels
JMFIT1:   Y-position        =    325.233 +/-   0.1264 pixels
JMFIT1:                       RA 17 26 42.62962    +/-  0.00017
JMFIT1:                       DEC -36 09 19.2477   +/-  0.00126
JMFIT1:   Major axis        =   9.006 +/-  0.4812 pixels
JMFIT1:   Minor axis        =   5.570 +/-  0.2976 pixels
JMFIT1:   Position angle    =  90.000 +/-  4.336 degrees
JMFIT1:   Major axis        =  0.09006 +/-0.00481 asec
JMFIT1:   Minor axis        =  0.05570 +/-0.00298 asec
JMFIT1:   Position angle    =  90.000 +/-  4.336 degrees
JMFIT1:   - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
JMFIT1:                   Deconvolution of component in pixels
JMFIT1:                        Nominal     minimum     maximum
JMFIT1:     Major ax             8.07        7.69        8.44
JMFIT1:     Minor ax             3.88        3.57        4.17
JMFIT1:     Pos ang             90.00       86.96       93.04
JMFIT1:                   Deconvolution of component in asec
JMFIT1:                        Nominal     minimum     maximum
JMFIT1:     Major ax          0.08069     0.07692     0.08444
JMFIT1:     Minor ax          0.03876     0.03570     0.04170
JMFIT1:     Pos ang          90.00018    86.96520    93.03513
JMFIT1:   - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
JMFIT1: Appears to have ended successfully
JMFIT1: rgalp6 31DEC99 TST: Cpu=     0.4  Real=     1  IO=       664
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