Reading the maps with lightcone_io¶

The lightcone_io python module can be used to read FLAMINGO HEALPix maps, either by reading downloaded HDF5 files directly or by accessing maps stored on Cosma using the hdfstream service. The latter method might be better if you’re only interested in certain quantities or regions on the sky.

Installation¶

The lightcone_io module can be installed as follows:

pip install lightcone_io

For remote access to snapshots we also need the hdfstream module:

pip install hdfstream

Opening a set of HEALPix maps¶

The examples below show how to access the down-sampled maps for observer 0 in the fiducial L1_m9 simulation.

Opening remote files

# Connect to the hdfstream service and open the root directory
import hdfstream
root = hdfstream.open("cosma", "/")

# Location of the lightcone output relative to the directory we opened
basedir="FLAMINGO/L1_m9/L1_m9/healpix_maps/nside_4096"

# Specify which observer's lightcone to read
basename="lightcone0"

# Open the set of HEALPix maps on the server
import lightcone_io as lc
shell = lc.ShellArray(basedir, basename, remote_dir=root)

Opening local files

# Location of the lightcone output we downloaded
basedir="./FLAMINGO/L1_m9/L1_m9/healpix_maps/nside_4096/"

# Specify which observer's lightcone to read
basename="lightcone0"

# Open the set of HEALPix maps
import lightcone_io as lc
shell = lc.ShellArray(basedir, basename)

Reading map data¶

For each observer we have a number of concentric shells, and for each shell we have maps of various physical quantities. The pixel data for a particular map can be accessed by specifying a shell index and the name of the map:

# Index of the shell we're interested in
shell_nr = 0

# Name of the quantity we want to read
map_name = "TotalMass"

# Read the data
map_data = shell[shell_nr][map_name][...]

Here, indexing an individual map with the ellipsis ([...]) triggers the full map to be read in or downloaded. The result is a unyt array containing the pixel values with unit information. See the lightcone_io documentation for more details.