The HI and H2 fractions in cells

Xingyao Cai
  • 2
  • 23 Jan


Hope this messsage finds you well.

I am investigating the spatial distribution of HI and H2. To get the datas, I am trying to calculate using the methods given by Diemer 2018, Lagos 2015 and Marinacci 2017. However, there are so many different models ( GK11, K13, GD14), thus, I am confused about them. So I am wondering which model and method you used when calculating the data? I have checked the forum before and found that you have your own calculations before, but the volume is too big. Could you send me a small cutout of the total data, containing some galaxies for me to validate my calculation?

And could you provide me for some advice on calculating the HI and H2 fractions, like which paper should I read above those? Since the method given by Diemer 2018 will lead to a 2D map instead of a 3D distribution, and I also need the 3D distribution.

Thanks again for you kind help!


Dylan Nelson
  • 23 Jan

When you say "which model and method you used when calculating the data", what data do you mean?

All the works you reference calculate molecular H2 (and thus also atomic HI) with various different models, as you say.

There is no "fiducial" or "best" model, unfortunately. All are a bit uncertain, but hopefully (in most circumstances) provide a reasonable approximation.

My suggestion would be to implement the simplest model (based on gas cell properties, not based on 2D maps in projection, as you also suggest).

You can test on a small simulation such as TNG50-4, or on a cutout of an individual halo, both of which you can download on this website.

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