How to identify subhalos containing well-formed galaxies?
Andrés Cardona
26 Oct '19
Hi.
I'm trying to study the morphology of the galaxies in Illustris-1 at z=0.
I want to make sure that the subhaloes that I'm taking, have a well-formed galaxi inside them. How can I know this?
Tnaks,
Dylan Nelson
26 Oct '19
Hi Andres,
It depends perhaps what you mean by "well-formed". Do you want galaxies to satisfy some physical requirements, or numerical requirements?
Andrés Cardona
29 Oct '19
Hi Dylan,
From documentation, there's ~4'400.000 subhalos in SUBFIND, but of them, only ~40.000 are refered to "galaxies"
My question is how to identificate those "galaxies.
Thanks for answer :)
Dylan Nelson
29 Oct '19
Hi Andres,
In this case we mean the difference between a "galaxy" (which contains stars) and a "subhalo" (which is a dark matter object). All galaxies are subhalos, but not all subhalos are galaxies.
The minimal definition is SubhaloMassType[4] > 0, meaning that the stellar mass is nonzero.
A more stringent definition, which also excludes very small galaxies which are not going to be numerically well resolved, would be e.g. SubhaloLenType[4] > 100, meaning that the subhalo must have at least one hundred star particles.
Hi.
I'm trying to study the morphology of the galaxies in Illustris-1 at z=0.
I want to make sure that the subhaloes that I'm taking, have a well-formed galaxi inside them. How can I know this?
Tnaks,
Hi Andres,
It depends perhaps what you mean by "well-formed". Do you want galaxies to satisfy some physical requirements, or numerical requirements?
Hi Dylan,
From documentation, there's ~4'400.000 subhalos in SUBFIND, but of them, only ~40.000 are refered to "galaxies"
My question is how to identificate those "galaxies.
Thanks for answer :)
Hi Andres,
In this case we mean the difference between a "galaxy" (which contains stars) and a "subhalo" (which is a dark matter object). All galaxies are subhalos, but not all subhalos are galaxies.
The minimal definition is
SubhaloMassType[4] > 0, meaning that the stellar mass is nonzero.A more stringent definition, which also excludes very small galaxies which are not going to be numerically well resolved, would be e.g.
SubhaloLenType[4] > 100, meaning that the subhalo must have at least one hundred star particles.Thank you Dylan.
This is really useful.