With regards to the velocity data in the snapshot/subhalo files. If I am analyzing the rotation of a galaxy (e.g. Krot parameter that measures the mass-weighted ratio of azimuthal velocity to total velocity) is there a need to consider any correction of the velocity data for the overall velocity of the galaxy ie the velocity of the galactic centre of mass? I do not think this is necessary since the velocities (stellar, gas) are velocities with respect to the frame of reference of the subhalo and do not include a velocity with respect to the overall simulation. Is that correct ? Does that make sense ?
Dylan Nelson
20 Jan
The Velocities fields of the snapshots, i.e. for specific particle types, are in the frame of reference of the box. They are not with respect to the motion of any halo or subhalo. WIthin a halo, yes you would typically want to subtract off the motion of the overall object (i.e. SubhaloVel as a first thing to use).
With regards to the velocity data in the snapshot/subhalo files. If I am analyzing the rotation of a galaxy (e.g. Krot parameter that measures the mass-weighted ratio of azimuthal velocity to total velocity) is there a need to consider any correction of the velocity data for the overall velocity of the galaxy ie the velocity of the galactic centre of mass? I do not think this is necessary since the velocities (stellar, gas) are velocities with respect to the frame of reference of the subhalo and do not include a velocity with respect to the overall simulation. Is that correct ? Does that make sense ?
The
Velocitiesfields of the snapshots, i.e. for specific particle types, are in the frame of reference of the box. They are not with respect to the motion of any halo or subhalo. WIthin a halo, yes you would typically want to subtract off the motion of the overall object (i.e.SubhaloVelas a first thing to use).