Skip to content
New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Work around for correctly calculating flux from an integrated emission (moment 0 - 2D) image and constraining min_npix? #160

Open
AstroJLo opened this issue Mar 8, 2018 · 4 comments

Comments

@AstroJLo
Copy link

AstroJLo commented Mar 8, 2018

Hi there,

Firstly, a big thank you to everyone that has worked on updating and maintaining the astrodendro package; i found the tutorial to be very useful and informative at allowing me to understand what dendrograms are and how they can be utilised. Now, onto my questions:

Is it possible to calculate the correct flux from a 2D moment 0 (integrated emission) image of a molecular cloud? The units of the 2D image for BUNIT are in K*km/s. I am aware that when i try to do this, i get an error message stating that it isn't possible, due to these units not being implemented yet. However, i am just wondering whether a work around exists for this issue?

If I use 3D data (i.e. a PPV molecular line cube), this issue doesn't occur and the flux can be correctly calculated when BUNIT is equal to 'K' (thanks to the efforts of @tomr-stargazer !).

The issue with using a data cube (for now) is that it becomes slightly more challenging to choose the correct min_value, min_npix (this one in particular) and min_delta values; which isn't an issue that occurs with the 2D data. Perhaps @keflavich may have some ideas here for constraining min_npix in a data cube? The cloud I'm looking at is 'small' with the x and y dimensions of the image having an area that won't exceed 870" x 870" (29 x 29 pixels, with each pixel increment being 30 arc seconds).

@keflavich
Copy link
Contributor

Could you post the traceback you get when using BUNIT = K km/s ? I don't remember exactly where that is, but it sounds like it might be an equivalency issue that may have been solved.

@AstroJLo
Copy link
Author

AstroJLo commented Mar 8, 2018

Hi @keflavich , thanks for getting back to me. As per your request, here is a screenshot of the code.

dendrograms_2d_units_issue_screengrab

@AstroJLo
Copy link
Author

AstroJLo commented May 8, 2018

Hi @keflavich , i'm just wondering if there has been any update on this issue?

@keflavich
Copy link
Contributor

No, I don't have anything. Could you post a minimum working example? That might help.

FYI, I'm not an official maintainer of this repository, so I'm not promising anything.

Sign up for free to join this conversation on GitHub. Already have an account? Sign in to comment
Labels
None yet
Projects
None yet
Development

No branches or pull requests

2 participants