[daip] A question about HI image analysis in classical AIPS !!

[Eric Greisen]

Everton Ludke writes:

 >     According to the AIPS Cookbook, one must produce the data
 > cube with MX or other imaging task. Then you must ALTDEF and

      Use IMAGR not MX

 > ALTSW to get the channel axis converted to a velocity axis.

     These may not be required - the VLA and VLBA provide this
information from the correlator.

 > Then, you BLANK the off-source pixels to magical values.
 > 
 >     After that, the cube axis must be inverted in order
 > with task TRANS, TRANSCOD='-312' to get the decreasing velocity
 > as first axis.  XMOM can be run afterwards to get the moment
 > images from that cube.
 > 
 >     My questions are:
 > 
 >   (a) How could we get the total neutral hydrogen mass
 > from the XMOM0 image ?
 > 
 > I believe that I must set some sort of box around the galaxy
 > and integrate the total HI flux with some aips task, but
 > I don't know which tasks must be used to get MHI in solar
 > masses from that map.

       IMEAN, IMSTAT, TVSTAT all will give the total flux in Jy.
Conversion of that to solar masses of HI is by standard means you
should find in text books.  I am not current on this area (although I
may become so in the next year) so I forget the formulae.

 > 
 >   (b) How to get the radial velocity profile of the rotation
 > curve with the XMOM1 image, without using GAL for model fitting ?
 > 
 > It seems to me that we must make a slice of XMOM1 image, specifying
 > a vector R from the centre of the galaxy to the desired point in an
 > edge of the galaxy disk. Again, which AIPS tasks must be used to
 > get V(R) from this image ?

The XMOM1 image is an image of velocity.  Put it on the TV and use
SETSLICE to set the end points.  Then SLICE to make a SL file and
SL2PL will plot things.  Alternatively, select the end points where
you think the major axis runs as pixels - using XMOM0 for example -
and the run SLICE on the XMOM1 image.

Eric Greisen