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تسجيل مستخدم جديدMassive star feedback - from the first stars to the present
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تأليف
Jorick S. Vink
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The amount of mass loss is of fundamental importance to the lives and deaths of very massive stars, the input of chemical elements and momentum into the interstellar and intergalactic media, as well as the emitted ionizing radiation. I review mass-loss predictions for hot massive stars as a function of metal content for groups of OB stars, Luminous Blue Variables, and Wolf-Rayet stars. Although it is found that the predicted mass-loss rates drop steeply with decreasing metal content (Mdot ~ Z^{0.7-0.85}), I highlight two pieces of physics that are often overlooked: (i) mass-loss predictions for massive stars approaching the Eddington limit, and for (ii) stars that have enriched their own atmospheres with primary elements such as carbon. Both of these effects may significantly boost the mass-loss rates of the first stars - relevant for the reionization of the Universe, and a potential pre-enrichment of the intergalactic medium - prior to the first supernova explosions.
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Massive stars are powerful sources of radiation, stellar winds, and supernova explosions. The radiative and mechanical energies injected by massive stars into the interstellar medium (ISM) profoundly alter the structure and evolution of the ISM, whic
h subsequently influences the star formation and chemical evolution of the host galaxy. In this review, we will use the Large Magellanic Cloud (LMC) as a laboratory to showcase effects of energy feedback from massive young stellar objects (YSOs) and mature stars. We will also use the Carina Nebula in the Galaxy to illustrate a multi-wavelength study of feedback from massive star.
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cretion. An alternative route is to start from heavy seeds formed by the direct collapse of gas onto a ~ 10^5 Msun BH. Here we investigate the relative role of light and heavy seeds as BH progenitors of the first SMBHs. We use the cosmological, data constrained semi-analytic model GAMETE/QSOdust to simulate several independent merger histories of z > 6 quasars. Using physically motivated prescriptions to form light and heavy seeds in the progenitor galaxies, we find that the formation of a few heavy seeds (between 3 and 30 in our reference model) enables the Eddington-limited growth of SMBHs at z > 6. This conclusion depends sensitively on the interplay between chemical, radiative and mechanical feedback effects, which easily erase the conditions that allow the suppression of gas cooling in the low metallicity gas (Z < Zcr and JLW > Jcr). We find that heavy seeds can not form if dust cooling triggers gas fragmentation above a critical dust-to-gas mass ratio (D > Dcr). In addition, the relative importance of light and heavy seeds depends on the adopted mass range for light seeds, as this dramatically affects the history of cold gas along the merger tree, by both SN and AGN-driven winds.
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