has been confirmed through X-ray observations  [e.g., @art:eckert15], by tracing the galaxy luminosity density  [@art:nevalainen15] and through the thermal Sunyaev-Zel’dovich effect  [@art:szeffect]. The cooler component of the IGM, on the other hand, is mostly kept ionized and heated by the the cosmic UV background (UVB). It can be traced through Lyman alpha absorption  [e.g., @art:abs2], Lyman alpha emission [@art:silva16] or through HI 21 cm emission [@art:takeuchi14; @art:kooistra17 hereafter K17] if the neutral fraction is high enough.\
In , using a simple model based on the dark matter density field, it was shown that multiple current and upcoming radio telescopes have the sensitivity to possibly detect the HI 21 cm signal from the cold component in strong large-scale filaments at $z$ = 0.1 within $\sim100$ h integrations and with signal-to-noise ratio (S/N) of $\sim1-10$ for phase 2 of the Square Kilometre Array (SKA2). Such an observation could have the potential to provide an unbiased tracer of the underlying dark matter distribution  [@art:cui18].\
The differential brightness temperature signal is proportional to the neutral hydrogen number density $n_{\rm HI}$ in cgs units following [@art:furl06]

$$\begin{aligned}
\delta T_{\mathrm{b}}^{\rm HI} (z) = & 5.48\times10^{-14}\times\frac{n_{\rm HI}(z)}{\left(1+z\right)H(z)}\\ \notag
&\times\left(1-\frac{T_{\rm CMB}(z)}{T_s}\right)\left[1 + H(z)^{-1}dv_r/dr\right]^{-1} \mathrm{K},\label{eq_c4:dtb}\end{aligned}$$

where $H(z)$ is the 