Velocity binning in Miriad

[renovatio]

Dear great Miriad developers and users,

I was wondering whether there is any ways in Miriad to make binning in velocity? I have a cube with a velocity resolution of about 0.5 km/s, but I like to have a velocity resolution of 5 km/s for instance. How can I do that in Miriad? Is there task for that?

Apologies if this topic was already discussed here.


Cheers,
Selcuk

[Peter Teuben]

Several options:
  imbin
  regrid
if you obtained the cube via invert, you can also use a more appropriate line= parameter.

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[melvyn wright]

invert line=velocity....

doc line ( or mirhelp line)

line=velocity ...

      "velocity"  Spectral channels, resampled at equal increments in
                       velocity (using the radio definition). The resampling
                       involves a weighted average of the spectral channels.
                       This is useful if the source was not Doppler tracked
                       correctly.

...

e.g.
  line=velocity,10,-10,1,1

         resamples the spectral data in velocity, to give 10 channels of width
         1 km/s. The channels are centered at -10.0,-9.0,-8.0, etc, km/s.
lines 52-74/74 (END)

On Sat, May 5, 2018 at 4:19 AM, Peter Teuben <teu...@gmail.com> wrote:

Several options:
  imbin
  regrid
if you obtained the cube via invert, you can also use a more appropriate line= parameter.

On 05/05/2018 06:26 AM, renovatio wrote:

Dear great Miriad developers and users,

I was wondering whether there is any ways in Miriad to make binning in velocity? I have a cube with a velocity resolution of about 0.5 km/s, but I like to have a velocity resolution of 5 km/s for instance. How can I do that in Miriad? Is there task for that?

Apologies if this topic was already discussed here.


Cheers,
Selcuk

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[renovatio]

Dear Peter and Melvyn,

Many thanks! I did not create the cube myself. If I did, it would be easier to use invert instead. THANKS a lot. imbin works just fine!

However, I am having a weird problem now which I did not have before. I was wondering whether you had any such problem related the convol task explained below.

I used convol task many times, including 10 minutes ago without any problem. But now it giving me a heart attack. After convolving a cube to final beam size I want, I obtain a spectrum for a specific region in the cube using imspect. However, all fluxes in the spectra are NaN(?). Weirdly enough I did not have that problem 10 minutes ago. However, if I use the unconvolved cube, imspect works just fine. There is something going on with convol. Have you ever faced such problem? Any idea what could be reason?

Many thanks in advance! 


5 Mayıs 2018 Cumartesi 14:19:44 UTC+3 tarihinde Peter yazdı:

[renovatio]

I sorted it out, but I still do not understand exactly what the error occurred in the first place. Let me summarise what I have done in case somebody may have the same problem, even if it is a tiny possibility.

The original cube is in .fits format. I converted it to Miriad file format using fits task (i.e.  .cm or .mir file). I then converted the file back to the .fits file and then to .cm file again. Then the problem was solved. Why the first conversion from the .fits file to the .cm file produced this error I do not know. Because that has never happened before. However, I suspect that the problem is related to the blank pixels. Because, after doing the first .fits -> .cm conversion, Miriad fits task gave the message of 'There were no blanked pixels in the input', But the second conversion gave the message of 'Some pixels were blanked ... A blanking mask was created'. So, after the second conversion the blank pixels have been taken care of, and convol task worked properly (at least that what I understood). Although I do not have a plausible explanation for this, thats what happened.

Best,


5 Mayıs 2018 Cumartesi 13:26:05 UTC+3 tarihinde renovatio yazdı: