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gaia-dpci / GaiaXPy

Gaia BP/RP spectra package
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Adding DECam g,r,i,z as a PhotometricSystem #20

Closed psferguson closed 2 years ago

psferguson commented 2 years ago

Hello, I was wondering if it would be possible to add the DECam g,r,i,z bandpasses as a PhotometricSystem in GaiaXPy? I think the filter transformation information is available here: https://noirlab.edu/science/programs/ctio/filters/Dark-Energy-Camera

Alternatively, if there was documentation for creating the GaiaXPy filter config files that would also work.

Thanks so much, -Peter Ferguson

fdeangeli commented 2 years ago

Hi Peter,

The DECam system has been added in the 1.1.4 release of GaiaXPy. Run pip install gaiaxpy --upgrade to update your installation to the latest release.

The code generating the filter bases has been used and validated extensively with other photometric systems, but no specific validation for the DECam synthetic photometry has been done. There are known systematics in the BP/RP spectra that will affect the synthetic photometry, particularly for bands covering wavelength ranges bluer than 400 nm and for faint sources. These are well detailed in the DR3 papers (Gaia Collaboration, Montegriffo et al. 2022, Montegriffo et al. 2022 and De Angeli et al. 2022).

Kind regards, Francesca De Angeli

dnidever commented 2 years ago

Hi Francesca,

Would it also be possible to add the DECam u-band and VR-filters to gaiaxpy. They are available at https://noirlab.edu/science/programs/ctio/filters/Dark-Energy-Camera as well.

Thanks, David Nidever

fdeangeli commented 2 years ago

Hi David,

sorry for not replying earlier, but you added your request as a comment to a closed issue. It would have been better to create a new issue. Much more visible :) Actually, could I please ask you to do so, i.e. create a new issue just copying and pasting the text above?

I will add the following comment to the newly generated issue when available, but just to speed things up, I had a look at the DECam filters page. The system we offer in GaiaXPy is the first one from that page (DES standard bandpasses). The u and VR are only available from the second set, which also includes different definitions for grizY. Unfortunately, the two systems are not clearly labelled and we are concerned that if we now add u and VR, it will be unclear for users which of the grizY filters we have used. You should also be aware that the Gaia BP spectra do not cover the full range of the u band.

Thanks, Francesca