Energy density within TeV sources associated with pulsars as a function of pulsar Ė and τ_c under different assumptions. Top panels: energy density calculated as ε_e = Ėτ_c∕V, described in Sect. 3.1. Bottom panels: energy density calculated using the electron spectrum derived from TeV γ-ray measurements, described in Sect. 3.2. The shaded regions correspond to an energy density lower than that of the ISM under any reasonable assumption. Systems for which measured properties are taken from the HGPS are indicated bycircles, whereas stars indicate the systems where HAWC data is used (see also Table 2).