Redshift in which the subhalo has fallen into the parent halo (infall)
Natanael de IsÃdio
3 Feb
I am trying to estimate the timescale over which some of my galaxies stopped forming new stars after falling into a major halo. Since I am starting with TNG50, I would like to ask whether the information about the redshift at which a given halo fell into its parent one is available somewhere. For example, I know that this subhalo (https://www.tng-project.org/api/TNG50-1/snapshots/96/subhalos/118219/) has this one (https://www.tng-project.org/api/TNG50-1/snapshots/96/halos/3/) as its parent halo, but I would like to know exactly when the subhalo fell into the major one. Does TNG50 have this information available?
Thank you for your attention and time.
Dylan Nelson
3 Feb
This would be one definition of "infall time".
You will find in many TNG papers calculations of this value, but there are no catalogs of such quantities available.
The way to calculate it would be to follow the main progenitor branch of the primary (sub)halo, obtaining its Pos and Group_R_Crit200 at each snapshot. Then separately follow the main progenitor branch of the infalling subhalo, obtaining its Pos at each snapshot. Make sure there are no gaps or misalignments by interpolating if necessary. Then calculate the (periodic) distance of the infaller with respect to the primary, normalized to r200c. Identify the two snapshots that bracket the value 1.0 (there could be more than one such pair, and then you will need to define if you mean e.g. first infall, or most recent infall), and linearly interpolate to identify the redshift where this distance crosses this value.
I am trying to estimate the timescale over which some of my galaxies stopped forming new stars after falling into a major halo. Since I am starting with TNG50, I would like to ask whether the information about the redshift at which a given halo fell into its parent one is available somewhere. For example, I know that this subhalo (https://www.tng-project.org/api/TNG50-1/snapshots/96/subhalos/118219/) has this one (https://www.tng-project.org/api/TNG50-1/snapshots/96/halos/3/) as its parent halo, but I would like to know exactly when the subhalo fell into the major one. Does TNG50 have this information available?
Thank you for your attention and time.
This would be one definition of "infall time".
You will find in many TNG papers calculations of this value, but there are no catalogs of such quantities available.
The way to calculate it would be to follow the main progenitor branch of the primary (sub)halo, obtaining its
PosandGroup_R_Crit200at each snapshot. Then separately follow the main progenitor branch of the infalling subhalo, obtaining itsPosat each snapshot. Make sure there are no gaps or misalignments by interpolating if necessary. Then calculate the (periodic) distance of the infaller with respect to the primary, normalized to r200c. Identify the two snapshots that bracket the value1.0(there could be more than one such pair, and then you will need to define if you mean e.g. first infall, or most recent infall), and linearly interpolate to identify the redshift where this distance crosses this value.