-
Notifications
You must be signed in to change notification settings - Fork 9
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
Support for CHI2 images and absolute thresholding? #440
Comments
That parameter doe not exist, right. I am not aware we ever discussed this. I'll have a look. If it does not exist it shouldn't be difficult to implement. Could you provide us with some example data (chi-square image plus SE2 catalog plus SE2 seg image)? |
I'm not entirely sure what's in those images but we use the detection image to estimate the initial value of flux for model fitting so that could be a problem if doesn't give us a usable flux. |
That parameter to make the detection threshold absolute for CHI2 images does not exist yet, and we will implement it for the next version v0.17. Until then you can:
That should result in the intended behaviour. @hjmcc again, could you give us some example data? |
Thank you @mkuemmel and @marcschefer for your help! I put some images from COSMOS2020 (https://ui.adsabs.harvard.edu/abs/2021AAS...23721506W/abstract) in You can find a subimage of the chi-mean images in there, as well as the same segment of the i-band image. I include an image from the paper showing what the parameters we used in COSMOS2020. My aim to is to try to run SE++ on the COSMOS2020 data with detection parameters as close as possible to SE2. Thanks for the hint @mkuemmel , I will try that! |
@hjmcc I checked you images, the weight image is 1.0 everywhere, hence the detection threshold is absolute as expected for a chi-square image. Have a look! |
Thank you, @mkuemmel for the help and posting these scripts! I tried your config and compared it to a similar config for SE2.0. Seems to work, it detects about ~20% more objects however, as you can see from the check-images (OBJECTS from SE2.0 and SEGMENTATION from SE++). So I understand that the SE++ deblending and splitting algorithm is different from SE2? I will make some more tests. GIF shows (chi2, SE2 and SE++). (We have quite an agressive threshold in SE2.0 to avoid too many spurious sources around the very bright objects in COSMOS. |
Some comments from my side:
On the second image I think I switched background subtraction off, which to me seems to be appropriate for a chi2 image. |
Thanks again @mkuemmel. I confirm that the minimum area is the same in both cases.
Thanks for the hint. I guess you are referring to these parameters:
What should I set them to? I couldn't find anything in the documentation... Cheers! |
Set:
The objects get larger which eliminates the halo objects around bright galaxies. False positives in the field are suppressed by the 'original', high core threshold. |
Dear SE++ developers, thanks for all the hard work.
I have a question, is SE++ able to use CHI2 detection images produced by Swarp? In 'sextractor classic' these images were signalled by adding -THRESH_TYPE ABSOLUTE in the configuration file. I grepped the sources and documentation and couldn't find anything 😰😰😰 .
thanks !
The text was updated successfully, but these errors were encountered: