Red Supergiants in M31 and M33. II. The Mass-loss Rate

Abstract

Mass loss is an important activity for red supergiants (RSGs) and can influence their evolution and final fate. Previous estimations of mass-loss rates (MLRs) of RSGs exhibit significant dispersion due to differences in method and the incompleteness of samples. With the improved quality and depth of surveys including the UKIRT/WFCAM observations in the near-infrared, and LGGS and PS1 in the optical, a rather complete sample of RSGs is identified in M31 and M33 according to their brightness and colors. For about 2000 objects in either galaxy from this largest ever sample, the MLR is derived by fitting the observational optical-to-mid-infrared spectral energy distribution with the DUSTY code of a 1D dust radiative transfer model. The average MLR 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 from RSGs 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. The MLRs are divided into three types by the dust species, i.e., amorphous silicate, amorphous carbon, and optically thin, and the relations between MLR and stellar parameters, infrared flux, and colors are discussed and compared with previous works for the silicate and carbon dust groups.

Multiple components in the molecular outflow of the red supergiant NML Cyg

“…Investigations into the relation between the gas-mass loss and the dust-mass loss from galactic RSGs will, furthermore, be crucial to help interpret the observations of extragalactic populations of RSGs, which are generally used to measure the o v erall impact of RSGs on galactic evolution (e.g. Dell'Agli et al 2018 ;Wang et al 2021 ). We underscore the need for a systematic understanding of the molecular and dust content of the outflows of this class of star, in order to understand the mass-loss mechanism, the mass-loss history , and ultimately , the impact of mass loss on stellar and galactic evolution.…”

A Census of Thermally-Pulsing AGB stars in the Andromeda Galaxy and a First Estimate of their Contribution to the Global Dust Budget

“…Previous ground-based observations targeting AGB stars in M31 have been limited to shallow observations, low angular resolution, and/or small fields (Brewer et al 1995;Brewer et al 1996;Kodaira et al 1998;Davidge 2001;Battinelli & Demers 2005;Davidge et al 2005;Boyer et al 2013;Hamren et al 2015;Boyer et al 2019;Ren et al 2021;Massey et al 2021;Wang et al 2021). By characterizing M31's AGB population, we will have the confidence of uniformity and statistical power need to compare it to other nearby galaxies.…”

The Sample of Red Supergiants in Twelve Low-Mass Galaxies of the Local Group

“…In fact, there is a similar effect for all RSGs. A higher metallicity will bring about a higher mass loss rate (Wang et al 2021) and make RSGs leave RSG phase more quickly. Previous studies have shown that metallicity affects the ratio of blue-to-red supergiants (B/R) and Wolf-Rayet stars to RSGs (WR/RSG).…”

“…In addition, the statistical study of the complete sample of RSGs is key to estimating the influence of RSGs on a galaxy. For example, the mass loss rates of a complete sample which were determined in M31 and M33 by Wang et al (2021) illustrate the contribution of interstellar dust by massive stars to the interstellar medium. This is particularly important in that the source of interstellar dust in high-redshift galaxies is still a puzzle (Reimers 1975;Kudritzki & Reimers 1978;Gordon et al 2016).…”