Helium Abundance in ISM of Galaxies: Best-Estimate Value

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The discussion centers on the Helium abundance (He/H ratio) in the interstellar medium (ISM) of galaxies, specifically seeking the best-estimate values for both the nearby Universe and high redshift. The primordial Helium abundance is noted as Y = 0.24, but the exact ISM values remain unclear. Participants speculate that the current ISM ratio may be similar to the primordial value, possibly with a slight increase in Helium concentration. References or specific data on the ISM Helium abundance are requested to provide clarity. The conversation highlights a gap in accessible information regarding Helium ratios in galactic ISM.
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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