Source counts of the TGSS (red, continuous) and NVSS (blue, long-dashed) catalogs. The red shaded histogram on the right shows the number counts (in S₁₅₀ flux unit) of the objects in the TGSS × NVSS catalog. The blue shaded area on the left shows the number counts (in S_1.4 flux unit) of the same TGSS × NVSS objects. Dashed vertical lines indicate the lower flux thresholds assumed for the analysis presented in this paper. The histogram in the insert shows the distribution of the 150 MHz–1.4 GHz spectral index of the sources in the TGSS × NVSS catalog. The vertical dotted line indicates the peak of the distribution at α = −0.77.