AI 中文总结
该研究通过UKIRT对M33进行近红外监测，结合斯皮策太空望远镜的中红外测光，用光谱能量分布建模等方法，测量AGB恒星和RSG的质量损失率，发现其与光度等有关，指出恒星向ISM返质速率低，需外部气体维持M33恒星形成。
AI 中文摘要
我们在英国红外望远镜（UKIRT）对本星系群螺旋星系M33（三角座星系）开展了近红外监测活动。在本系列的第六篇论文中，我们测量了M33恒星盘上脉动渐近巨星分支（AGB）恒星和红超巨星（RSG）的尘埃和气体质量损失率。我们将时间平均近红外测光与斯皮策太空望远镜获得的多时期中红外测光相结合，并采用光谱能量分布建模和比例关系的组合方法。我们发现质量损失率大致与光度（诞生质量）成正比，对脉动周期和/或振幅有较弱的额外依赖（反映恒星演化）。作为一个群体，AGB恒星对星际介质（ISM）的质量返回贡献最大。超级AGB恒星的质量损失率也非常高，超过$10^{-4}$ M$_\odot$ yr$^{-1}$。RSG的质量损失似乎有不同模式，速率远低于、接近和远高于核燃烧时间尺度。主导质量损失阶段的时间尺度约为$\sim0.6$-$2\times10^5$ yr，比热脉冲AGB或RSG阶段短。恒星向ISM返回质量的速率约为$\sim0.1$ M$_\odot$ yr$^{-1}$，约为恒星形成速率的四分之一，这将在约10亿年内耗尽当前ISM质量，因此需要额外的外部气体供应来维持M33未来长期的恒星形成。
英文摘要
We have conducted a near-infrared monitoring campaign at the UK InfraRed Telescope (UKIRT), of the Local Group spiral galaxy M33 (Triangulum). In this sixth paper of the series, we measure the dust and gas mass-loss rates by the pulsating Asymptotic Giant Branch (AGB) stars and red supergiants (RSGs) across the stellar disc of M33. We combined our time-averaged near-IR photometry with the multi-epoch mid-IR photometry obtained with the Spitzer Space Telescope, and employed a combination of spectral energy distribution modelling and scaling relations. We found that the mass-loss rate is approximately proportional to luminosity (birth mass), with additional weaker dependence on pulsation period and/or amplitude (reflecting stellar evolution). As a population, AGB stars contribute most to the mass return into the interstellar medium (ISM). Super-AGB stars also reach very high mass-loss rates, in excess of $10^{-4}$ M$_\odot$ yr$^{-1}$. The mass loss of RSGs appears to be subject to different modes, with rates well below, around, and well above the nuclear burning timescale. The timescale for the dominant mass loss phase is $\sim0.6$-$2\times10^5$ yr, shorter than the thermal-pulsing AGB or RSG phases. The rate at which stars return mass to the ISM, $\sim0.1$ M$_\odot$ yr$^{-1}$ is about four times lower than the star formation rate, which would deplete the current ISM mass within about a Gyr, thus requiring additional, external gas supplies to sustain the long-term future of star formation in M33.
CommentsResubmitted to MNRAS in 2018 after addressing the referee's comments
