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Lines of sight

We provide a set of lines of sight extracted randomly from the simulation box using the COLT code. COLT uses the native Voronoi tessellation of the simulation, therefore retaining all the information available. Each line of sight is composed of a set of segments, corresponding to the intersection between the ray and one Voronoi cell. Therefore, each segment has a different length. Additionally, each ray has a different number of segments. For each segment, a number of gas properties are extracted from the Voronoi cell and saved. The lines of sights are initialized from random position within the simulation box and with random directions, and have length \( 100 Mpc/h \), employing periodic boundary conditions to wrap around the box when necessary.

We provide 150 lines of sights for each snapshot from the 54th onward. The lines of sight (LOS) for each snapshot are stored in a different HDF5 file. This file contains general information in the attributes of the Header group (in a similar way to most other data product). The available attributes are listed in the table below (click to open).

Root attributes ▾
Attribute Dimensions Units Description
BoxSize 1 \( ckpc / h \) Spatial extent of the periodic box (in comoving units).
HubbleParam 1 - Little \( h \), defined as \( h = H_0 / (100 km/s/Mpc) \)
MultipleOrigins 1 - Flag indicating that the LOS have different origins within the simulation box.
NumRays 1 - Number of LOS stored in the file.
Omega0 1 - The cosmological density parameter for matter.
OmegaBaryon 1 - The cosmological density parameter for baryons.
RayImpact 1 - Meaningless for the current configuration.
RayLength 1 \( ckpc/h \) Length of the LOS.
RayLength_cMpc 1 \( ckpc \) Length of the LOS in \( cMpc \).
RaySphere 1 - Meaningless for the current configuration.
Redshift 1 - The redshift corresponding to the current snapshot.
UnitLength_in_cm 1 - Length unit used in the simulation, expressed in comoving cm.
UnitLength_in_g 1 - Mass unit used in the simulation, expressed in g.
UnitLength_in_cm_per_s 1 - Velocity unit used in the simulation, expressed in comoving cm / s.
Within each LOS file, the properties extracted along the LOS are saved in a number of groups, each one containing a dataset for each ray (named simply with a progressive number, starting from 0). These values are directly extracted from the simulation cell crossed by the ray, and saved as they are. This means that the units and considerations made for such fields (see Snapshots) apply directly to the ray fields. Additionally, LOS properties are saved in a mix of groups (with the same format just described) and datasets. Both are described in the table below (click to open). We distinguish groups from dataset in the dimensions column.
Datasets and groups ▾
Dataset Dim. Units Description
Density group \( 10^{10} M_\odot h^2 / ckpc^3 \) Gas density in the Voronoi cell. Internal units.
ElectronAbundance group - Electron abundance, defined as \( n_e / n_H \), in each Voronoi cell.
GFM_DustMetallicity group - Dust-to-metal ratio in each Voronoi cell.
GFM_Metallicity group - Gas-phase metallicity in each Voronoi cell.
GFM_Metals group - For each ray, contains the mass fracion of nine species: H, He, C, N, O, Ne, Mg, Si, Fe (in this order). Each one is the dimensionless ratio of mass in that species to the total gas cell mass.
HI_Fraction group - HI fraction (i.e. \(n_{HI} / n_H \) ) in the cell.
HeI_Fraction group - HeI fraction (i.e. \(n_{HeI} / n_H \) ) in the cell. Note: the denominator is \(n_H\), rather than \(n_{He}\).
HeII_Fraction group - HeII fraction (i.e. \(n_{HeII} / n_H \) ) in the cell. Note: the denominator is \(n_H\), rather than \(n_{He}\).
InternalEnergy group \( (km/s)^2 \) Internal energy of the gas in the Voronoi cell.
MagneticField group \( (h/a^2) \sqrt{}\)UnitPressure Three-dimensional magnetic field.
PhotonDensity group #\( (ckpc/h^3) / 10^{63} \) Density of photons in the cells in the three spectral bands tracked in Thesan.
RayOrigins (Nlos,3) \( ckpc/h \) Starting point of the LOS.
RayEndings (Nlos,3) \( ckpc/h \) End point of the LOS. Note that this does not include the box wrapping due to PBC, so this value can nominally lie outside of the simulation box, although the rays include PBC..
RaySegments group \( ckpc/h \) Length of each segment composing the LOS. These segments are the intersection of the LOS with the Voronoi tesselation.
StarFormationRate group \( M_\odot / yr \) Star Fromation Rate of the gas.
Velocity group \( km \sqrt{a} /s \) Spatial velocity. Multiply this value by \(\sqrt{a}\) to obtain peculiar velocity.