what's the difference of the 'SubfindDMDensity' between PartType0,1,4

Di Yihuan

7 Jan

Hi TNG teams and other friends,
I wonder what's the difference of the 'SubfindDMDensity' between PartType0,1,4? if they are the same thing?

And does the Density and SubfindDensity in the PartType0 mean rho(x,y,z) (N,3)and rho(r)(N)?
if I try to picture a gas mean density profile with r, is it better to using SubfindDensity than Density?

Thanks in advance.
Yihuan

Dylan Nelson

13 Jan

Hello,

Yes SubfindDMDensity is the same measurement for all particle types. Note that this is a local estimate, so it is valid at the position of that gas/DM/star particle.

All such values, including Density and SubfindDensity, are estimates at the precise Coordinates value (x,y,z) of that cell or particle.

There is no rho(r) data, you would need to compute this by first computing r of cells/particles (from the halo center), then binning.

For gas density, you have two options: use average/median values of PartType0/Density at the r you are interested in, or else sum all PartType0/Masses in a bin, i.e. spherical shell, around r, and then normalize by the volume of that bin.

Hi TNG teams and other friends,

I wonder what's the difference of the 'SubfindDMDensity' between PartType0,1,4? if they are the same thing?

And does the Density and SubfindDensity in the PartType0 mean rho(x,y,z) (N,3)and rho(r)(N)?

if I try to picture a gas mean density profile with r, is it better to using SubfindDensity than Density?

Thanks in advance.

Yihuan

Hello,

Yes

`SubfindDMDensity`

is the same measurement for all particle types. Note that this is a local estimate, so it is valid at the position of that gas/DM/star particle.All such values, including

`Density`

and`SubfindDensity`

, are estimates at the precise`Coordinates`

value (x,y,z) of that cell or particle.There is no

`rho(r)`

data, you would need to compute this by first computing`r`

of cells/particles (from the halo center), then binning.For gas density, you have two options: use average/median values of

`PartType0/Density`

at the`r`

you are interested in, or else sum all`PartType0/Masses`

in a bin, i.e. spherical shell, around`r`

, and then normalize by the volume of that bin.I got it. Thanks again.