<p>I need to compare some ALMA observations of a protoplanetary disk to disk-integrated fluxes obtained from a model.</p>
<p>The ALMA observations are upper limits of non-detected spectral lines, where the RMS is measured from moment 0 maps, given in Jy/beam km/s. The disk integrated fluxes from the model are given in W/m<span class="math-container">$^2$</span>.</p>
<p>How can I convert the measured RMS from the observations to a disk integrated flux given in W/m<span class="math-container">$^2$</span>?</p>
<p><a href="https://i.sstatic.net/AAdxX.jpg" rel="noreferrer"><img src="https://i.sstatic.net/AAdxX.jpg" alt="enter image description here" /></a></p>
<p>Previous similar questions <a href="https://astronomy.stackexchange.com/questions/38996/converting-from-mathrmw-m-2-to-mathrmjy-km-s-1/41797#41797">here</a> and <a href="https://astronomy.stackexchange.com/questions/26721/converting-jy-beam-to-jy">here</a> are related but not quite what I'm looking for.</p>

CC BY-SA 4.0
2021-08-11T13:42:44.537Z
Isn't [your first link](https://astronomy.stackexchange.com/questions/38996/converting-from-mathrmw-m-2-to-mathrmjy-km-s-1/41797#41797) what you're looking for, except the other way? Or is it the "per beam" that confuses you? I think both "Jy km/s" and "W/m²" are integrated over the source, i.e. both _are_ "per beam", no?
pela
CC BY-SA 4.0
2021-08-11T15:26:03.600Z
@pela yes I am unsure how to work with the 'per beam' aspect. The synthesised beam size for the observation is 0.09x0.06arcsec. But since there is no detection, do I just choose an area that is roughly size of the disk, measure its size, then divide this by the number of synthesised beams that could fit within this area? I've added an image to the question to try to better explain what I need to do.
lucas
CC BY-SA 4.0
2021-08-12T09:13:06.193Z
Okay I see the difference now, but I'll refrain from answering this, because I have zero experience with radio astronomy and I don't fully understand this Fourier-transforming back and forth in interferometry, especially when it comes to limits rather than detections.
pela
<radio-astronomy><units><interferometry><modeling><proto-planetary-disk>
Convert from Jy/beam km/s to W/m$^2$
lucas
# Convert from Jy/beam km/s to W/m$^2$

(Asked by: username_0 on 2021-08-11)

I need to compare some ALMA observations of a protoplanetary disk to disk-integrated fluxes obtained from a model.

The ALMA observations are upper limits of non-detected spectral lines, where the RMS is measured from moment 0 maps, given in Jy/beam km/s. The disk integrated fluxes from the model are given in W/m$^2$.

How can I convert the measured RMS from the observations to a disk integrated flux given in W/m$^2$?

[![enter image description here](https://i.sstatic.net/AAdxX.jpg)](https://i.sstatic.net/AAdxX.jpg)

Previous similar questions [here](https://astronomy.stackexchange.com/questions/38996/converting-from-mathrmw-m-2-to-mathrmjy-km-s-1/41797#41797) and [here](https://astronomy.stackexchange.com/questions/26721/converting-jy-beam-to-jy) are related but not quite what I'm looking for.

**Tags:** radio-astronomy, units, interferometry, modeling, proto-planetary-disk
> **Comments:**
> **username_1**: Isn't [your first link](https://astronomy.stackexchange.com/questions/38996/converting-from-mathrmw-m-2-to-mathrmjy-km-s-1/41797#41797) what you're looking for, except the other way? Or is it the "per beam" that confuses you? I think both "Jy km/s" and "W/m²" are integrated over the source, i.e. both _are_ "per beam", no?  
> **username_0**: @pela yes I am unsure how to work with the 'per beam' aspect. The synthesised beam size for the observation is 0.09x0.06arcsec. But since there is no detection, do I just choose an area that is roughly size of the disk, measure its size, then divide this by the number of synthesised beams that could fit within this area? I've added an image to the question to try to better explain what I need to do.  
> **username_1**: Okay I see the difference now, but I'll refrain from answering this, because I have zero experience with radio astronomy and I don't fully understand this Fourier-transforming back and forth in interferometry, especially when it comes to limits rather than detections.  

---

## 0 answers

