[daip] New Ticket - [!DKX-380761]: JMFIT: setting the zero level

[Rachael Ainsworth]

New Ticket: JMFIT: setting the zero level

Hello,

I am currently trying to fit two nearby sources using JMFIT. My current setup is:


AIPS 1: JMFIT: Task to fit Gaussian models to an image by least-squares
AIPS 1: Adverbs     Values                 Comments
AIPS 1: ----------------------------------------------------------------
AIPS 1: INNAME     'CH24S4.FACET'          Input image name (name)
AIPS 1: INCLASS    'ICL001'                Input image name (class)
AIPS 1: INSEQ         1                    Input image name (seq. #)
AIPS 1: INDISK        1                    Input image disk drive #
AIPS 1: BLC        *all 0                  Bottom Left corner of fit
AIPS 1: TRC        *all 0                  Top Right corner of fit
AIPS 1: OUTNAME    ' '                     Output image name (name)
AIPS 1: OUTCLASS   ' '                     Output image name (class)
AIPS 1: OUTSEQ        0                    Output image name (seq. #)
AIPS 1: OUTDISK       1                    Output image disk drive #
AIPS 1: NGAUSS        2                    Number of components
AIPS 1: CTYPE         1           2        Model types; one for each
AIPS 1:               0           0         component
AIPS 1:                                     0->1=Gaussian
AIPS 1:                                     2=Zero level; 3=Zero+slope
AIPS 1:                                     4=Zero+slope+curve;
AIPS 1:                                     5=see HELP JMFIT
AIPS 1:                                    Guess of model parameters
AIPS 1: GMAX       *all 0                  Peak of component (JY)
AIPS 1:                                      0-> Use maximum value
AIPS 1: GPOS       *all 0                  (X,Y) position (pixels)
AIPS 1:                                      0-> Use position of max
AIPS 1: GWIDTH     *all 0                  (BMAJ, BMIN, PA) of comp.
AIPS 1:                                      (pixels,pixels,deg)
AIPS 1:                                      0->Use clean beam
AIPS 1: DOMAX         1           1        Solve for GMAX?  >0 -> yes
AIPS 1:               1           1          returns the error
AIPS 1: DOPOS         1           1        Solve for GPOS?  >0 -> yes
AIPS 1:               1           1          returns the error
AIPS 1:               1           1           1           1
AIPS 1: DOWIDTH       1           1        Solve for GWIDTH? >0-> yes
AIPS 1:               1           1          returns the error
AIPS 1:               1           1           1           1
AIPS 1:               1           1           1           1
AIPS 1: BWSMEAR       0                    Bandwidth smearing corr.
AIPS 1: RADIUS        0                    Radius for finding RMS
AIPS 1: NITER         0                    Maximum # of iterations
AIPS 1:                                      0->20*NGAUSS
AIPS 1:                                    Solve for model parameters?
AIPS 1: DOPRINT       0                    <=0 -> Print maps and
AIPS 1:                                      solutions on line printer
AIPS 1:                                    >0 -> print on terminal
AIPS 1:                                    =0 -> maps not printed
AIPS 1: FITOUT     ' '
AIPS 1:                                    Disk file to save fit info
AIPS 1: DOOUTPUT     -1                    >0 -> 1 Catalog residual map
AIPS 1: OFFSET        0                    Cutoff level. 0-> None
AIPS 1: DOMODEL      -1                    > 0 => put solutions in a CC
AIPS 1:                                    file with input image
AIPS 1: OUTVERS       0                    MF table version number
AIPS 1:                                       -1 => none, 0 => new
AIPS 1: STVERS       -1                    STars output file version
AIPS 1:                                       -1 => none, 0 => new
AIPS 1: PRTLEV        0                    Level of messages desired:
AIPS 1:                                      0 normal, 1 some extra,
AIPS 1:                                      2 iteration results
AIPS 1: PBPARM     *all 0                  Primary beam parameters:
AIPS 1:                                    (1) level to believe - <= 0
AIPS 1:                                    means do not apply a primary
AIPS 1:                                    beam (2) > 0 use (3)-(7)


I am simply trying to fit a gaussian and a zero level base for each source. However, the task is fitting two separate zero levels for each source and therefore returning inconsistent flux densities. The sources are right next to each other, so the zero level should be consistent, and I've attempted a variety of fitting boxes, but still get very different zero levels. 

I have also tried setting:

> GMAX 0, ACTNOISE, 0
> DOMAX 0, -1, 0

using the actual noise from the image header, but I am unsure if I have this input correct. I still obtain different zero levels. 

So my question is, how does one set the zero level so that the returned fluxes are consistent with each other?

Any help would be much appreciated!

Cheers,

Rachael

Ticket Details
===================
Ticket ID: DKX-380761
Department: AIPS Data Processing
Priority: Default
Status: Open
Link:  https://help.nrao.edu/staff/index.php?_m=tickets&_a=viewticket&ticketid=2860