Left: 3, 48, 96, and 192σ levels of the 144 MHz radio emission (σ = 750 μJy beam⁻¹ and a resolution of 30 × 30 arcsec) with the sampling cells on top. Right: observed and model profiles of flux density (top), spectral index (middle), and break frequency (bottom). The upper limits were computed based on the 2σ level of the 610 MHz map. In the top and middle panels, the predictions are reported based on the two different galactic velocities.