reference for shape H2-self-shielding function

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Leonard Romano

Sep 7, 2021, 7:19:33 AM9/7/21

Dear enzo-developers,

This question might be more related to Grackle, but I had trouble signing up for the mailing list so I am asking here instead.
I noticed that in grackle (and I have been told the same is true for enzo), the exponent in the first term of the H2-self-shielding function is slightly different, than in the commonly cited form from Draine & Bertoldi '96 (ApJ, 468, 269). The corresponding code in grackle is in line 1434 in the file "solve_rate_cool_g.F":

f_shield = 0.965_DKIND / (1._DKIND + x/b_doppler)**1.1+
     &           0.035_DKIND * exp(-8.5E-4_DKIND * sqrt(1._DKIND +x))/
     &           sqrt(1._DKIND + x)

The exponent here is 1.1, whereas in Draine & Bertoldi '96 it's 2. If anyone knows any references for this different shape, or knows whether or not this is a typo, it would be very helpful!


Leonard Romano, B.Sc.(レオナルド・ロマノ)
Physics Department
Technical University of Munich (TUM), Germany
Theoretical Astrophysics Group 
Department of Earth and Space Science
Graduate School of Science, Osaka University, Japan
he / him / his
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