of gas can additionally drive up the mean filament signal to the higher outliers shown in Fig. \[fig:filsigs\]. The outliers to lower mean signals are due to misalignments of the inferred filament spines with the underlying density distribution.\

![Distribution of the mean signal per cell in filaments as a function of their length for Bisous filaments longer than 5 $h^{-1}$Mpc in the EAGLE simulation box. A filament radius of 0.5 $h^{-1}$Mpc was adopted together with the UVB.[]{data-label="fig:filsigs"}](./images/filaments_siglens_He_hm01_caseA_1cat_sph.pdf "fig:"){width="48.00000%"}\

We note that many other methods have been developed to identify the large-scale structure components in simulations [see e.g., @art:libeskind17 for an overview of a number of different available codes]. For observations, the large-scale structure is only traced by the positions of the galaxies. Recovering the filaments requires a method that can properly infer the structures based solely on the limited data from galaxy surveys. This makes the Bisous model a good choice for this study, since it can be applied directly to both the simulations and real data from galaxy redshift surveys. The same model will therefore come back in our observational strategy in Section \[sec:obsstrat\].\
Another thing to note is that observations do not measure distances in physical distances. Instead, 