From: Jun-Hui Zhao 
To: Christopher Faesi 
Cc: smamiriad@cfa.harvard.edu
Subject: Re: Question about continuum subtraction



On Wed, 5 Sep 2012, Christopher Faesi wrote:

> Hello,
>
> I'm a Harvard graduate student and a fairly new MIRIAD user, and I'm trying
> to image an SMA spectral line cube that has a rather weak CO (2-1)
> detection. I'm trying to use the uvlin task to subtract the continuum,
> which is at about 0.06-0.08 Jy (but somewhat noisy). The line peaks at
> about 0.28 Jy. (This is in the raw time-averaged uv data). However, I'm
> getting what appears to be nonsense out of the task - when I use
> mode=continuum to see what it thinks the continuum is, the amplitude is
> only about 0.02 Jy at most! Furthermore, I'm using order=1, and I'm seeing
> curves for the continuum. I'm including the syntax I used below. Any advice
> would be most helpful.
>
> uvlin vis=dcl69_miriad chans=2200,2230,2260,2290 out=dcl69.cont order=1
> mode=continuum
   Try use a large number of line-free channels for the continuum fitting.
If you can direct us where is your data located, we may give you a better
advice.
   Jun-Hui Zhao

>
> (or out=dcl69.csub mode=line to get the supposedly continuum-subtracted
> visibilities, which unsurprisingly look like the original ones).
>
> Many thanks,
> Chris Faesi
>
> --
> Christopher M. Faesi
> cfaesi@cfa.harvard.edu
> 617.496.0741 (office)
> 812.272.5459 (mobile)