ABSTRACT
Red supergiants are important contributors to interstellar medium through massive wind. Due to serious interstellar extinction, the complete sample of RSGs is extremely difficult to obtain in our Galaxy. As two of the largest spiral galaxies in the Local Group, M31 and M33 can serve as a reference to analyze the global contribution of RSGs to the galactic medium. By using evident branching of red dwarfs and red (super)giants in the near-infrared color-color (J-H/H-K) diagram, the foreground dwarf stars are excluded efficiently with the UKIRT observational data, The most complete and pure sample of RSGs in M31 and M33, specifically, 5498 and 3055 RSGs respectively, are obtained from the color-magnitude ( J-K/K) diagram of the member stars. The dust radiative transfer model, the DUSTY code, is run to calculate the mass loss rate of RSGs. The average mass loss rate of RSGs is found to be around 2.0 × 10^-5 M⊙ yr^-1 with a gas-to-dust ratio of 100, which yields a total contribution to the interstellar dust of about 1.1 × 10^-3 M⊙ yr^-1 in M31 and 6.0 × 10^-4 M⊙ yr^-1 in M33, a non-negligible source in comparison with evolved low-mass stars.
BIO
Biwei Jiang, professor in the Department of Astronomy at Beijing Normal University. She graduated from the Department of Astronomy, Beijing Normal University in 1989 and received a PhD in Science from Graduate University for Advanced Studies, Japan in 1997. She has been engaged in research on interstellar medium and stellar astronomy. The main research topics include: circumstellar gas and dust of evolved stars, light variation and mass loss rate of red supergiants in the Local Group Galaxies, interstellar extinction laws from infrared to ultraviolet, and the extinction and dust of supernova remnants.
Host: Hui Li
