Distances to the supernova remnants in the inner disk

Abstract

Context. Distance measurements of supernova remnants (SNRs) are essential as accurate estimates of physical size, dust masses, and some other properties of SNRs depend critically on accurate distance measurements. However, the determination of SNR distances is still a tough task. Aims. Red clump stars (RCs) have a long history of being used as standard candles. In this work, we take RCs as tracers to determine the distances to a large group of SNRs in the inner disk. Methods. We first selected RC stars based on the near-infrared (IR) color-magnitude diagram. Then the distance to and extinction of RC stars were calculated. To extend the measurable range of distance, we combined near-IR photometric data from the 2MASS survey with the deeper UKIDSS and VVV surveys. With the help of the Gaia parallaxes, we also removed contaminants, including dwarfs and giants. Because an SN explosion compresses the surrounding interstellar medium, the SNR region would become denser and exhibit higher extinction than the surroundings. The distance of an SNR is then recognized by the position where the extinction and its gradient is higher than that of the ambient medium. Results. A total of 63 SNRs distances in the Galactic inner disk were determined and divided into three Levels A, B, and C with decreasing reliability. The distances to 43 SNRs are well determined with reliability A or B. The diameters and dust masses of SNRs were estimated with the obtained distance and extinction.