Effect of mass-loss due to stellar winds on the formation of supermassive black hole seeds in dense nuclear star clusters
Monthly Notices of the Royal Astronomical Society
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The observations of high-redshifts quasars at z 6 have revealed that supermassive black holes (SMBHs) of mass ∼ 109M were already in place within the first ∼Gyr after the big bang. Supermassive stars (SMSs) with masses 103−5M are potential seeds for these observed SMBHs.Apossible formation channel of these SMSs is the interplay of gas accretion and runaway stellar collisions inside dense nuclear star clusters (NSCs). However, mass-loss due to stellar winds could be an important limitation for the formation of the SMSs and affect the final mass. In this paper, we study the effect of mass-loss driven by stellar winds on the formation and evolution of SMSs in dense NSCs using idealized N-body simulations. Considering different accretion scenarios, we have studied the effect of the mass-loss rates over a wide range of metallicities Z∗ = [.001–1]Z and Eddington factors fEdd = L∗/LEdd = 0.5, 0.7, and 0.9. For a high accretion rate of 10−4Myr−1, SMSs with masses 103Myr−1 could be formed even in a high metallicity environment. For a lower accretion rate of 10−5Myr−1, SMSs of masses ∼ 103−4M can be formed for all adopted values of Z∗ and fEdd, except for Z∗ = Z and fEdd = 0.7 or 0.9. For Eddington accretion, SMSs of masses ∼ 103M can be formed in low metallicity environments with Z∗ 0.01 Z. The most massive SMSs of masses ∼ 105M can be formed for Bondi–Hoyle accretion in environments with Z∗ 0.5 Z. An intermediate regime is likely to exist where the mass-loss from the winds might no longer be relevant, while the kinetic energy deposition from the wind could still inhibit the formation of a very massive object.