Public Data Access Overview / Discussion Forum

Hello! I am trying to track a set of BHs across snapshots using the TNG300-1 BH merger catalog. I found that over half of the BH IDs disappear between snapshots, but do not appear anywhere in the catalog as the “in” BH. I am wondering if you see any issues with my code? I’ve attached the relevant parts below - this is for z=2 to z=1. Or is this catalog known to be incomplete? Thank you for your help!

with h5py.File('tng300_blackhole_mergers.hdf5') as f:  
    IDs_swallowed = f['id_in'][:]
    IDs_keep = f['id_out'][:]
    masses_swallowed = f['mass_in'][:] * 1e10/hh
    masses_keep = f['mass_out'][:] * 1e10/hh
    scalefactors = f['time'][:]
redshifts = 1/scalefactors - 1

snap_old = 33 #z~2
snap_new = 50 #z~1
z_old = il.groupcat.loadHeader(basePath, snap_old)['Redshift']
z_new = il.groupcat.loadHeader(basePath, snap_new)['Redshift']

a_old = 1 / (1 + z_old)
a_new = 1 / (1 + z_new)
mask = (scalefactors >= a_old) & (scalefactors <= a_new)

IDs_swallowed = IDs_swallowed[mask]
IDs_keep = IDs_keep[mask]
masses_swallowed = masses_swallowed[mask]
masses_keep = masses_keep[mask]
redshifts = redshifts[mask]
scalefactors = scalefactors[mask]

order = np.argsort(scalefactors)
IDs_swallowed = IDs_swallowed[order]
IDs_keep = IDs_keep[order]
masses_swallowed = masses_swallowed[order]
masses_keep = masses_keep[order]
redshifts = redshifts[order]
scalefactors = scalefactors[order]

new_bhs = il.snapshot.loadSubset(basePath, snap_new, 'BHs', fields=['ParticleIDs','BH_Mass','BH_Mdot','Coordinates'])

def track_mergers(BHID):
    if not np.isfinite(BHID):
        return np.nan, np.nan, np.nan

    cur_ID = int(BHID)

    mass_add = 0
    count_add = 0
    start = 0

    while True:
        mergers_keep = np.where(IDs_keep[start:] == cur_ID)[0]
        mergers_swallowed = np.where(IDs_swallowed[start:] == cur_ID)[0]

        if (len(mergers_keep) == 0) and (len(mergers_swallowed) == 0):
            break

        if len(mergers_keep) == 0:
            earliest_merger = start + mergers_swallowed[0]
            outcome = 'swallowed'
        elif len(mergers_swallowed) == 0:
            earliest_merger = start + mergers_keep[0]
            outcome = 'keep'
        elif mergers_keep[0] > mergers_swallowed[0]:
            earliest_merger = start + mergers_swallowed[0]
            outcome = 'swallowed'
        else:
            earliest_merger = start + mergers_keep[0]
            outcome = 'keep'

        if outcome == 'keep':
            mass_add += masses_swallowed[earliest_merger]
        else:
            mass_add += masses_keep[earliest_merger]
            cur_ID = int(IDs_keep[earliest_merger])

        count_add += 1
        start = earliest_merger + 1

    bh_ind = np.where(new_bhs['ParticleIDs'] == cur_ID)[0]
    if len(bh_ind) == 0:
        return np.nan, np.nan, np.nan
    else:
        return bh_ind[0], count_add, mass_add