Helium Abundance in ISM of Galaxies: Best-Estimate Value

In summary, the abundance of helium in the interstellar medium (ISM) of galaxies is an important factor in understanding the evolution and composition of galaxies. This is estimated through observations of emission lines in the spectra of galaxies, with the best-estimate value currently around 11% by mass. The helium abundance can vary among different types of galaxies, with spiral galaxies having higher abundances due to their higher rates of star formation. The helium abundance also plays a crucial role in the formation of new stars, with a higher abundance leading to more efficient star formation.
  • #1
vladivostok
8
0
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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  • #2
I venture a guess that is about the same ration. Maybe a little more skewed towards helium now, but mostly still the same.
 

1. What is the significance of measuring the helium abundance in the ISM of galaxies?

The abundance of helium in the interstellar medium (ISM) of galaxies is an important factor in understanding the evolution and composition of galaxies. Helium is the second most abundant element in the universe and serves as a key indicator of the chemical enrichment and star formation history of galaxies.

2. How is the helium abundance in the ISM of galaxies estimated?

The helium abundance in the ISM of galaxies is estimated through observations of various emission lines in the spectra of galaxies. These emission lines correspond to specific elements, including helium, and can be used to determine the relative abundance of different elements in the ISM.

3. What is the best-estimate value for the helium abundance in the ISM of galaxies?

The best-estimate value for the helium abundance in the ISM of galaxies is currently around 11% by mass. This means that for every 100 atoms of hydrogen in the ISM, there are approximately 11 atoms of helium.

4. How does the helium abundance in the ISM of galaxies vary among different types of galaxies?

The helium abundance in the ISM of galaxies can vary significantly among different types of galaxies. For example, spiral galaxies, which have a higher rate of star formation, tend to have higher helium abundances than elliptical galaxies, which have lower rates of star formation.

5. What impact does the helium abundance in the ISM of galaxies have on the formation of new stars?

The helium abundance in the ISM of galaxies plays a crucial role in the formation of new stars. As stars form from the gas and dust in the ISM, the helium abundance affects the rate and efficiency of this process. A higher helium abundance can lead to more efficient star formation, while a lower abundance can result in fewer stars being formed.

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