Computing the halo mass function and the SFH

[matteo86bo]

Hi,
I have a catalog of dark matter halos, which consists of their COM positions and their masses.
I need to determine the halo mass function. How can I do? I mean, it is easy to plot the number of halos between mass M and M+dM, but how can I have information on the volume? I don't get it.

Similarly, how can I determine the SFH in terms of solar masses per year per volume, when my stellar catalog contains only stars positions and their birthdate? I mean the problem it is alway the volume.

I know it is a stupid question but I really don't get it.


Thanks in advance

 

[zhermes]

Well... how big is the volume of the catalog?

 

[phyzguy]

Most dark matter halos are characterized using NFW profiles. If you know the mass and the concentration (usually called c), then you can calculate the density profile, the virial radius, and whatever else you might want to know. Here's a place to start:

http://en.wikipedia.org/wiki/Navarro–Frenk–White_profile

The original paper by Navarro, Frenk, and White is a good reference:

http://arxiv.org/abs/astro-ph/9508025