Multi-wavelength images of the SNR HB9, the H II region G159.2+3.3, and the surrounding area. (a) False colour Fermi-LAT 1–300 GeV TS map centred on the SNR HB9. The white contours are the PMO 13.7 m ¹²CO (J=1–0) image from the MWISP–CO line survey, integrated in the velocity range of –13.0 – +6.5 km s^–1. The γ-ray and CO enhancement in the upper part of the image is apparently associated with another SNR, G156.2+5.7. The 3.25° × 3.25° white box in the centre is the FoV of the images shown in panel b. (b) The red colour is the 4.85 GHz radio continuum image from the Green Bank 6-cm (GB6) survey (Gregory et al. 1996). The green colour is the DSS2 red-band image that covers the Hα line. The blue colour is the ROSAT/PSPC broad-band (0.1–2.4 keV) image obtained from the ROSAT All Sky Survey (RASS; Voges et al. 1999). The contours outline the Fermi-LAT image in panel a. The 0.93° × 0.93° white box in the lower left is the FoV of panel c, with the vertical bar overlaid on the bright SE filament marking the location of the MDM 1.3 m/CCDS slit. (c) Zoom-in of panel b, with the slit location plotted as a white bar, which is the same as the white bar in panel b. The 3.92° × 3.92° black box is the FoV of panel d. (d) Zoom-in PanSTARRS r-band image close to the centre of the slit. The double lines illustrate the width of the slit.