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jacopo-chevallard / BEAGLE-general

Basic information to get started with the galaxy spectral modelling tool Beagle
https://www.iap.fr/beagle/
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Meaning of output parameters #68

Closed steveschulze closed 6 years ago

steveschulze commented 6 years ago

Hi,

I have a question about the meaning of some keywords.

What is the difference between M_tot and M_star and between SFR and SFR_10?

Which masses and SFRs are usually returned by other SED fitting software, e.g. LePhare and MagPhys?

Cheers,

Steve

steveschulze commented 6 years ago

A few more things. The specific SFR is normalised to M_star, right?

Cheers,

Steve

jacopo-chevallard commented 6 years ago

Hi Steve, the difference between M_star and M_tot is explained in pag 29 of the manual, while that between SFR and SFR_10 in pag 30. Let me know if the explanation on the manual is unclear to you!

The specific SFR is normalised to M_star, right?

No, the specific SFR is normalized to M_tot, is it explained (perhaps not very clearly) in pag 30 of the manual

jacopo-chevallard commented 6 years ago

(I've edited the manual to clarity the definition of sSFR)

steveschulze commented 6 years ago

Hi Jacopo,

Thanks a lot for your quick replies. Hmm, I wonder why I asked you about the SFR indicators. This was clearly described in the manual. Sorry...I think I understand the mass estimates better. On page 25 you mention that M_STAR includes the return fraction to the ISM.

Is your definition of the sSFR used by other SED fitters, too? I wonder because I want to compare my results to literature results that were done with different software packages, e.g. LePhare and FAST.

Cheers,

Steve

jacopo-chevallard commented 6 years ago

Is your definition of the sSFR used by other SED fitters, too? I wonder because I want to compare my results to literature results that were done with different software packages, e.g. LePhare and FAST.

I honestly don't know about the definition of sSFR in other codes, but the stellar masses provided by most codes usually include the effect of the return fraction. I would take a look at their manuals (although the definitions used are not always clearly stated), my guess is that their sSFR is computed considering the return fraction. To compare, you should therefore multiply the Beagle sSFR by the factor M_tot/M_star

steveschulze commented 6 years ago

Thanks. I will check this carefully.