Helium Abundance in ISM of Galaxies: Best-Estimate Value

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SUMMARY

The best-estimate value for the Helium abundance (He/H ratio) in the interstellar medium (ISM) of galaxies in the nearby Universe is approximately 0.24, consistent with the primordial Helium abundance. While some speculation suggests a slight increase in this ratio over time, definitive measurements for the ISM at high redshift remain elusive. Further research and references are needed to confirm these values across different galaxies.

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vladivostok
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Hi,

Here is an info I don't manage to obtain from anywhere so far !
What is the "best-estimate" of the Helium abundance (the He/H ratio) in the interstellar medium of galaxies in the nearby Universe and at high redshift?

I know the primordial He abundance is Y = 0.24 but what is the value for the ISM of galaxies?

Does anybody know that? any reference please?

Thanks !
 
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I venture a guess that is about the same ration. Maybe a little more skewed towards helium now, but mostly still the same.
 

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