The Extinction Distance of Supernova Remnants in Combination with the CO Line Measurements

Accurate distance measurements to supernova remnants (SNRs) are crucial for understanding their physical properties and evolution. We present a novel method that combines CO line observations with three-dimensional extinction maps to determine distances to SNRs (G93.7−0.2, G109.1−1.0, G156.2+5.7, and G166.0+4.3) through their associated molecular clouds. For each SNR, candidate CO velocity components corresponding to interacting molecular clouds are identified based on previous observational evidence with refinements: [−19, −3] km s −1 for G93.7−0.2, [−51, −46] km s −1 for G109.1−1.0, [−10, 0] km s −1 for G156.2+5.7, and [−27, −15] km s −1 for G166.0+4.3. By examining extinction-distance profiles along the sightlines and identifying extinction jumps that spatially coincide with CO emission features, we derive distances of 1.82 ± 0.13 kpc for G93.7−0.2, 3.05 ± 0.15 kpc for G109.1−1.0, 0.60 ± 0.15 kpc for G156.2+5.7, and 3.44 ± 0.23 kpc for G166.0+4.3. Our extinction-based distances are largely consistent with previous estimates while with better accuracy and robustness.