On Sun, May 27, 2018 at 2:48 PM, Nick Gnedin <ngnedin@gmail.com> wrote:


What are the implicit units of the deposited field? In the following script using implicit units returns an incorrect result, while setting them explicitly gives the correct one.

import yt
import numpy as np

d = yt.load("rei10_a0.1001/rei10_a0.1001.art")

xcen = d.arr([5,5,5],"Mpccm/h")
s = d.sphere(xcen,(100,"kpc"))

sf = ('STAR','particle_mass')
df = ('deposit','STAR_density')
print("sum=%9.3e int=%9.3e"%(np.sum(s[sf]),np.sum(s[df]*s[('gas','cell_volume')])))

The left-hand expression has units of code_mass, the right-hand expression has units of code_length^3 * g/cm^3.

It helps to see what's going on if you print out the result without using float formatting:

    In [17]: print(np.sum(s[sf]),np.sum(s[df]*s[('gas','cell_volume')]))
    6.893747161029751e-05 code_mass 1.8183255409899212e-31 code_length**3*g/cm**3

    In [18]: print(np.sum(s[sf]).to("Msun"),np.sum(s[df]*s[('gas','cell_volume')]).to("Msun"))
    32518.862230804152 Msun 32518.862230804145 Msun
print("sum=%9.3e int=%9.3e"%(np.sum(s[sf].in_units("Msun")),np.sum(s[df].in_units("Msun/kpc**3")*s[('gas','cell_volume')].in_units("kpc**3"))))

sum=6.894e-05 int=1.818e-31
sum=3.252e+04 int=3.252e+04

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