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cconroy20 / fsps

Flexible Stellar Population Synthesis
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Possible issue effecting Cloudy Ly-a #75

Closed stevet40 closed 2 weeks ago

stevet40 commented 1 month ago

We noticed that there was (circa November 2023) a bug fix in the Cloudy v23.01 release that has some impact on Ly-a line strength in Cloudy. The correction is described here: https://ui.adsabs.harvard.edu/abs/2023RNAAS...7..246G/abstract

Having compared the plot in that RNAAS article to the Cloudy configuration described in Byler+17 (i.e. the cloud density and range of ionisation parameters used), I think the effect on Ly-a intensity would be a change by a factor of 2.5-3x. Although I understand that the Cloudy grids in FSPS have been rerun since 2017, so this may have changed.

What version of Cloudy does the current version of FSPS correspond to? And do you expect this to have a big effect if it's pre v23.01?

Apologies if you're already aware of this, or if it's already addressed!

Cc: @jrleja @hiranyapeiris @ixkael @justinalsing @sinandeger

bd-j commented 1 month ago

Hi @stevet40, thanks for bringing this to our attention. Certainly all the grids (except maybe the BPASS ones) have been run with pre-23.01 versions of cloudy. It's not clear to me how much this effect is restricted to the WD ('with dust') grids which are neither the default nor recommended for use.

stevet40 commented 2 weeks ago

Thanks for the reply @bd-j! I think you're right that it does sound like this mainly affects dusty clouds, even though it is a little ambiguous from the v23.01 release note. Thanks for confirming about the default grids, and when they were last updated. Even if they're pre-v23.01, hopefully the non-dusty grids won't be too badly hit by this bug.

I'll mark this issue as closed, as I guess it sounds like this isn't anything major to worry about. Thanks again for the help!