Left: the grey-scale image shows the intensity of H i line emission in units of K km s^-1, measured by the Parkes radio telescope during the Southern Galactic Plane Survey (SGPS) (McClure-Griffiths et al. 2005). The intensities are integrated in the velocity range  −13.79 km s^-1 to  −21.21 km s^-1 (shown as a shaded region in the velocity profile, right), corresponding to a near/far kinematic distance of 1.6–2.3 kpc/13.0–13.7 kpc. Contours of the Gaussian-smoothed (σ = 0.10°) VHE γ-ray excess are shown in blue. The red contours depict the intensity of the radio emission measured by the Very Large Array (VLA) at 330 MHz (see also Fig. 1 left). The radio data have been smoothed with σ = 0.03°. The white circle illustrates the integration region for the velocity profile shown on the right. Right: velocity profile of H i line emission intensity, integrated over the region enclosed by the dashed circle on the left. The velocity resolution is 0.08 km s^-1. The kinematic distance, shown in red, is derived from the velocity using the Galactic rotation curve of Fich et al. (1989).