2021ApJ...917...47R

We present the detections of shocked molecular hydrogen (H₂) gas in near- and mid-infrared and broad CO in millimeter from the mixed-morphology supernova remnant (SNR) HB 3 (G132.7+1.3) using the Palomar Wide-field InfraRed Camera, the Spitzer GLIMPSE360 and Wide-field Infrared Survey Explorer (WISE) surveys, and the Heinrich Hertz Submillimeter Telescope. Our near-infrared narrow-band filter H₂ 2.12 µm images of HB 3 show that both Spitzer Infrared Array Camera and WISE 4.6 µm emission originates from shocked H₂ gas. The morphology of H₂ exhibits thin filamentary structures and a large scale of interaction sites between the HB 3 and nearby molecular clouds. Half of HB 3, the southern and eastern shell of the SNR, emits H₂ in a shape of a butterfly or W, indicating the interaction sites between the SNR and dense molecular clouds. Interestingly, the H₂ emitting region in the southeast is also co-spatial to the interacting area between HB 3 and the H II regions of the W3 complex, where we identified star-forming activity. We further explore the interaction between HB 3 and dense molecular clouds with detections of broad CO(3-2) and CO(2-1) molecular lines from the southern and southeastern shell along the H₂ emitting region. The widths of the broad lines are 8-20 km s^–1; the detection of such broad lines is unambiguous, dynamic evidence of the interactions between the SNR and clouds. The CO broad lines are from two branches of the bright, southern H₂ shell. We apply the Paris-Durham shock model to the CO line profiles, which infer the shock velocities of 20-40 km s^–1, relatively low densities of 10^3–4 cm^–3, and strong (>200 µG) magnetic fields.