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Maybe its a dumb question, but to convert Jy/beam to Jy, I just have to multiply it by the beam size in sr right?

Being $\Omega$ the beam size: $\Omega = \frac{\pi \theta_{maj} ~~ \theta_{min}}{4 \ln{2}}$

Jy/beam $\cdot \ \Omega$ = Jy ?

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  • $\begingroup$ Please add a little more info - define J and Jy, and what your beam source is -- for example is it a point source? $\endgroup$ – Carl Witthoft Jun 22 '18 at 14:08
  • $\begingroup$ See en.wikipedia.org/wiki/Jansky $\endgroup$ – Mike G Jun 22 '18 at 19:37
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So long as you accurately know the beam size, then yes multiplying your Jy/beam measurement (effectively flux density) by the beam size (effectively area of flux) will give you the total Jy (effectively the flux).

See this source as an example.

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Actually to convert from Jy/beam to Jy/pixel you need to divide by the beam size.

Let's say you have a quantity of 1 Jy/beam, then

$\frac{Jy}{beam} \frac{beam}{\Omega}$, then to go from Jy/beam to Jy/pixel you would need to divide by $\Omega$.

The values of the beam major and minor axis must be in pixels.

Source: NRAO

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