[daip] TASK IRING

[Eric Greisen]

On 04/13/2016 11:03 PM, Israa wrote:
> Hi,
> Good Day,
>
>   I want to ask about  Task iring in AIPS. I want to make sure from
> input information. My data have beam size 51.77" X 47.22" and task
> imhead give me
>
> AIPS 1: Type       Pixels   Coord value     at Pixel     Coord incr
>     Rotat
> AIPS 1: RA---SIN   256    15 22 00.000 *129.00*        -15.000
> 0.00
> AIPS 1: DEC--SIN  256    05 04 00.000 *129.00*         15.000
> 0.00
> AIPS 1: FREQ         1      1.4127871E+09   1.00     2.4414062E+04    0.00
> AIPS 1: STOKES       1    1.0000000E+00    1.00    1.0000000E+00    0.00
> *Conv size*=  51.77 X  47.22 *Position angle*= -170.66
>
> *My questions are about x, y - coordinate center wrt rference point in
> pixels.*..Can I get it from task imhead (at pixel). I mean *129* or I
> have to suppose (0,129) for x and y as well
>
> *second question*, there are  radius inner ring ,  radius outer ring
> and width of each ring. In this case, I have to consider inner one is 0
> right?
>                                                outer one =51"
> According to beam size or what??
>                                                 width of each ring
> =within beam size
>
> Sorry for long questions, because I need to understand this task,

The reference pixel in x,y is 129,129.  IRING asks for the center of 
your object with respect to that pixel.  You need to find that center by 
examining your image of the object.

People often use the radius of the inner ring as 0.  The outer ring size 
is again determined by your object and should be enough to encompass all 
of the real emission.  The ring width could be the beam size (51") or 
you could try other larger widths to get a smoother result.  Note that 
if the object a say a galaxy which would be round if observed from above 
the plane, it may be elliptical when viewed at an angle.  IRING allows 
you to undo this viewing angle with some of the APARM values 
(inclination, position angle).

IRING integrates flux in your object and you have to tell it where your 
object is in the image and what shape to fit with rings.

ERic Greisen