Question on Centering Stellar Particle Velocities in IllustrisTNG
AMIT MONDAL
31 Jul
would like to analyze the velocities of the stellar particles in a central galaxy. I will download the Velocities field for the stars. Should these velocities be transformed into the rest frame of the central galaxy by subtracting the corresponding SubhaloVel, or are the downloaded stellar velocities already given in that frame?
Dylan Nelson
2 Aug
The PartType4/Velocities dataset you would download is exactly the same as in the snapshot.
So, it is not relative to the galaxy or subhalo motion in any way.
Making it relative to SubhaloVel is a good choice, you should check if that is sufficient. For e.g. massive galaxies, this may not represent the motion of the core/center of the galaxy, and you may want to derive a different velocity by considering the motion of the central stars, for instance.
would like to analyze the velocities of the stellar particles in a central galaxy. I will download the Velocities field for the stars. Should these velocities be transformed into the rest frame of the central galaxy by subtracting the corresponding SubhaloVel, or are the downloaded stellar velocities already given in that frame?
The
PartType4/Velocitiesdataset you would download is exactly the same as in the snapshot.So, it is not relative to the galaxy or subhalo motion in any way.
Making it relative to
SubhaloVelis a good choice, you should check if that is sufficient. For e.g. massive galaxies, this may not represent the motion of the core/center of the galaxy, and you may want to derive a different velocity by considering the motion of the central stars, for instance.