In article ,
"Michael F. Stemper" writes:
The general unit system is kpc/h for lengths,
10^10M_Sol/h for masses, [...]
The documentation doesn't define h (at least that I see), but it is
almost certainly the current value of the Hubble constant in units of
100 km s^-1 Mpc-1. That means h = 0.7 (or very nearly so).
Don't overlook that quantities are given in _co-moving_
coordinates. To get physical coordinates, you have to multiply by the
appropriate power of the scale factor at the epoch in question.
Also, I'm going to need to follow the histories of various
subhalos. In the section on Merger Trees, it says:
The number inside each circle from the figure is the
unique ID (within the whole simulation) of the
corresponding subhalo [...]
Is this "SubhaloID"?
That's how it looks to me.
If I find a way to extract data about
SubhaloID == 42 (for example) from each snapshot, will I be
following a single subhalo through time?
It looks to me as though any given SubhaloID will exist in only one
snapshot. You have to follow the Progenitor or Descendent IDs to
look at evolution through time. If you don't want to follow each
step, you could select by FirstProgenitorID or RootDescendantID.
There's also TreeID.
Is there a similar field for halos? I'm trying to follow the
changes in a galaxy after its capture, and I think that I'll
need to be able to find out things like the mass of the halo
that captures it.
I think you need to use SubfindID as an index into the Group
Catalog. ("Group" = Halo as far as I can tell.)
This page is quite comprehensive, but that makes it overwhelming
for somebody who's never used Illustris before. Is there a
novice's introduction or some documentation that explains the
documentation?
There are numerous published papers and a general introduction at
http://www.illustris-project.org/about/#astronomers
Isn't there anyone locally you could ask for help? I expect some of
the people who worked on the simulation would be willing to answer
questions by email.
[1] http://www.illustris-project.org/data/docs/specifications/
--
Help keep our newsgroup healthy; please don't feed the trolls.
Steve Willner Phone 617-495-7123
Cambridge, MA 02138 USA