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تسجيل مستخدم جديدEffect of mass loss due to stellar winds on the formation of supermassive black hole seeds in dense nuclear star clusters
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The observations of high redshifts quasars at $zgtrsim 6$ have revealed that supermassive black holes (SMBHs) of mass $sim 10^9,mathrm{M_{odot}}$ were already in place within the first $sim$ Gyr after the Big Bang. Supermassive stars (SMSs) with masses $10^{3-5},mathrm{M_{odot}}$ are potential seeds for these observed SMBHs. A possible 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 idealised N-body simulations. Considering different accretion scenarios, we have studied the effect of the mass loss rates over a wide range of metallicities $Z_ast=[.001-1]mathrm{Z_{odot}}$ and Eddington factors $f_{rm Edd}=L_ast/L_{mathrm{Edd}}=0.5,0.7,,&, 0.9$. For a high accretion rate of $10^{-4},mathrm{M_{odot}yr^{-1}}$, SMSs with masses $gtrsim 10^3MSun$ could be formed even in a high metallicity environment. For a lower accretion rate of $10^{-5},mathrm{M_{odot}yr^{-1}}$, SMSs of masses $sim 10^{3-4},mathrm{M_{odot}}$ can be formed for all adopted values of $Z_ast$ and $f_{rm Edd}$, except for $Z_ast=mathrm{Z_{odot}}$ and $f_{rm Edd}=0.7$ or 0.9. For Eddington accretion, SMSs of masses $sim 10^3,mathrm{M_{odot}}$ can be formed in low metallicity environments with $Z_astlesssim 0.01mathrm{Z_{odot}}$. The most massive SMSs of masses $sim 10^5,mathrm{M_{odot}}$ can be formed for Bondi-Hoyle accretion in environments with $Z_ast lesssim 0.5mathrm{Z_{odot}}$.
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More than two hundred supermassive black holes (SMBHs) of masses $gtrsim 10^9,mathrm{M_{odot}}$ have been discovered at $z gtrsim 6$. One promising pathway for the formation of SMBHs is through the collapse of supermassive stars (SMSs) with masses $s
im 10^{3-5},mathrm{M_{odot}}$ into seed black holes which could grow upto few times $10^9,mathrm{M_{odot}}$ SMBHs observed at $zsim 7$. In this paper, we explore how SMSs with masses $sim 10^{3-5},mathrm{M_{odot}}$ could be formed via gas accretion and runaway stellar collisions in high-redshift, metal-poor nuclear star clusters (NSCs) using idealised N-body simulations. We explore physically motivated accretion scenarios, e.g. Bondi-Hoyle-Lyttleton accretion and Eddington accretion, as well as simplified scenarios such as constant accretions. While gas is present, the accretion timescale remains considerably shorter than the timescale for collisions with the most massive object (MMO). However, overall the timescale for collisions between any two stars in the cluster can become comparable or shorter than the accretion timescale, hence collisions still play a crucial role in determining the final mass of the SMSs. We find that the problem is highly sensitive to the initial conditions and our assumed recipe for the accretion, due to the highly chaotic nature of the problem. The key variables that determine the mass growth mechanism are the mass of the MMO and the gas reservoir that is available for the accretion. Depending on different conditions, SMSs of masses $sim10^{3-5} ,mathrm{M_{odot}}$ can form for all three accretion scenarios considered in this work.
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