[Yt-dev] minimum halo mass
Matthew Turk
matthewturk at gmail.com
Fri Mar 20 00:24:17 PDT 2009
> 1. Given the cosmological parameters from the Enzo parameter file,
> calculate the theoretical halo mass function using Press-Schechter or
> the equivalent (the Warren et al. mass function is actually the best
> one to use).
> 2. Figure out what the largest halo is that has at least a 50%
> probability of being inside the halo volume (in other words, what is
> the largest halo mass where you get 0.5 halos/box?)
> 3. Use the relationship between virial mass and virial radius to
> calculate a radius, and then scale it into box units.
> 4. Double that number and call that the padding.
This is a good idea. I like this idea. It's straightforward and
*easy to justify*.
> 1. One needs to assume a value of \sigma_8, since it's not actually
> in the Enzo parameter file. This isn't a big deal - it's somewhere
> between 0.8 and 0.9 for pretty much any simulation. For safety, I'd
> suggest we just pick 0.9, since that gives an overall higher mass
> function (and is thus the more conservative choice).
I agree.
> 2. This method of estimating padding only works for cosmology
> simulations. If one does non-cosmology particle simulations (which I
> could see happening in the future, if Enzo is adopted more widely)
> then people will have to specify their own padding. We can always
> cross that bridge when we get to it.
I do agree, and I think that specifying one's own padding is
acceptable, it just should be a reasonable guess for cosmo runs, I
felt.
> I have a press-schechter code that I am happy to donate to the cause.
> It's written in C, though, so somebody's going to have to mess around
> with it a bit. I don't have time, sadly, so I'd have to ask for
> somebody else to volunteer...
I'll take care of it; if you can send it my way, I'll take a look at
it, and it can ferment my mind grapes for a little while and I'll hit
it hard mid-April. Until then, I think everyone who needs parallel
hop has already figured out the padding issue, so we should be set. I
think this could be a useful set of code to include in any event!
Thanks, Brian!
-Matt
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