Five key elements¶

This section lists and briefly describes five of the most important elements of the hydrangea library. For a full description of all elements and their options, including those mentioned below, please see the detailed documentation pages below.

Download data¶

Coming soon…

Auto-generate file names¶

The hydrangea.Simulation class can be used to automatically generate the file names of the various catalogues. For example, to get the high-level galaxy catalogue file, and the first file of the snapshot 26 (z = 0.101) particle and subfind catalogues for simulation CE-29:

sim = hydrangea.Simulation(29)
galaxy_file = sim.fgt_loc
snapshot_file = sim.get_snapshot_file(26)
subfind_file = sim.get_subfind_file(26)

For more information and details, see here.

Read single HDF5 files¶

The hdf5.read_data() function provides a convenient wrapper around the h5py library, to read data from an HDF5 file to a numpy array in a single line. For example, to read the stellar masses of all galaxies in all snapshots of simulation CE-29 (in log₁₀ [M/M_Sun]):

galaxy_log_mstar = hydrangea.hdf5.read_data(galaxy_file, 'Mstar')

For more information and details, see here.

Read catalogues¶

The hydrangea.SplitFile class can be used to read in full snapshot (particle) catalogues, or substructure catalogues from Subfind. In both cases, it is also possible to read only entries at a given index, or a list (or range) of indices. For example, to read the (total) initial stellar masses of all subhaloes in snapshot 26 (in M_Sun):

subhaloes = hydrangea.SplitFile(subfind_file, 'Subhalo')
print(subhaloes.StellarInitialMass)  # In practice, would do something more meaningful

More information and details are given here.

Read sub-regions of snapshots¶

With the ReadRegion class, a specified sub-region of a snapshot can be read much more quickly than the full particle catalogue. For example, to read the temperatures of all gas particles within 100 pkpc (= 0.1 pMpc) from the centre of potential of subhalo 0 in snapshot 26 (in K):

subhalo_0 = hydrangea.SplitFile(subfind_file, 'Subhalo', read_index=0)
gas = hydrangea.ReadRegion(snapshot_file, 0, subhalo_0.Coordinates, 0.1, exact=True)
print(gas.Temperature)  # In practice, would do something more meaningful

More information and details are given here.