# Effect of mass loss due to stellar winds on the formation of supermassive black hole seeds in dense nuclear star clusters

**Authors:** Arpan Das, Dominik R. G. Schleicher, Shantanu Basu, Tjarda C. N. Boekholt  
**arXiv:** [2105.03450](https://arxiv.org/abs/2105.03450)  
**Date:** 2021-05-07  
**Summary page:** https://www.summarizepaper.com/en/paper/2105.03450v1/

## Key points

- High redshift quasars at $z\gtrsim 6$ indicate presence of supermassive black holes (SMBHs) with masses around $10^9\,\mathrm{M_{\odot}}$ in the early universe
- SMBHs believed to originate from supermassive stars (SMSs) with masses ranging from $10^{3-5}\,\mathrm{M_{\odot}}$
- Formation of SMSs can occur through gas accretion and runaway stellar collisions within dense nuclear star clusters (NSCs)
- Mass loss caused by stellar winds can limit formation of SMSs and reduce their final mass
- Idealized N-body simulations conducted to study formation and evolution of SMSs in dense NSCs
- Different scenarios of gas accretion considered, examining influence of mass loss rates across a range of metallicities ($Z_\ast=[.001-1]\mathrm{Z_{\odot}}$) and Eddington factors ($f_{\rm Edd}=L_\ast/L_{\mathrm{Edd}}=0.5,0.7, \& 0.9$)
- Results show high accretion rate leads to formation of SMSs with masses exceeding $10^3 \MSun$, even in high metallicity environments
- Lower accretion rate leads to formation of SMSs with masses around $10^{3-4}\, \mathrm{M_{\odot}}$, except for specific combinations of metallicity and Eddington factor
- Eddington accretion allows for formation of SMSs with masses around $10^3 \MSun$ in low metallicity environments ($Z_* \lesssim 0.01 \mathrm {Z_o}$)
- Most massive SMSs, with masses on the order of $10^5 \MSun$, can be formed through Bondi-Hoyle accretion in environments with metallicities below approximately 0.5 $\mathrm {Z_o}$
- Mass loss due to stellar winds is important to consider when studying formation and evolution of SMSs within dense NSCs
- Results provide insights into conditions for SMS formation and contribution to growth of SMBHs in early universe stages

## Summary

The observations of high redshift quasars at $z\gtrsim 6$ have provided evidence that supermassive black holes (SMBHs) with masses around $10^9\,\mathrm{M_{\odot}}$ were already present within the first billion years after the Big Bang. These SMBHs are believed to have originated from supermassive stars (SMSs) with masses ranging from $10^{3-5}\,\mathrm{M_{\odot}}$, which could serve as potential seeds for the observed SMBHs. One possible formation mechanism for these SMSs is through a combination of gas accretion and runaway stellar collisions occurring within dense nuclear star clusters (NSCs). However, the formation of SMSs can be limited by mass loss caused by stellar winds, which can significantly reduce their final mass. To investigate this effect, the authors of this study conducted idealized N-body simulations to study the formation and evolution of SMSs in dense NSCs. They considered different scenarios of gas accretion and examined the influence of mass loss rates across a wide range of metallicities ($Z_\ast=[.001-1]\mathrm{Z_{\odot}}$) and Eddington factors ($f_{\rm Edd}=L_\ast/L_{\mathrm{Edd}}=0.5,0.7, \& 0.9$). The results showed that for a high accretion rate of $10^{-4}\,\mathrm{M_{\odot}yr^{-1}}$, SMSs with masses exceeding $10^3 \MSun$ could be formed even in environments with high metallicity. On the other hand, for a lower accretion rate of $10^{-5}\, \mathrm{M_{\odot}yr^{-1}}$, SMSs with masses around $10^{3-4}\, \mathrm{M_{\odot}}$ could be formed for all considered values of $Z_*$ and $f_{Edd}$, except when $Z_* = \mathrm{Z_o}$ and $f_{Edd} = 0.7$ or 0.9. In the case of Eddington accretion, SMSs with masses around $10^3 \MSun$ could be formed in low metallicity environments with $Z_* \lesssim 0.01 \mathrm {Z_o}$. The most massive SMSs, with masses on the order of $10^5 \MSun$, could be formed through Bondi-Hoyle accretion in environments characterized by metallicities below approximately 0.5 $\mathrm {Z_o}$. Overall, this study highlights the importance of considering mass loss due to stellar winds when investigating the formation and evolution of SMSs within dense NSCs. The results provide valuable insights into the conditions under which SMSs can form and contribute to the growth of SMBHs in early universe stages.