分类： 天文学 >> 天文学 提交时间： 2023-02-19
摘要： The cosmological inflow of a galaxy is speculated to be able to enter the galaxy and enhance the star formation rate (SFR) and black hole accretion rate (BHAR). In this paper, by performing high-resolution hydrodynamic simulations in the framework of {\it MACER}, we investigate the fate of the inflow and its impacts on the evolution of a massive elliptical galaxy. The inflow properties are adopted from the cosmological simulation IllustrisTNG. We find that, the inflow gas hardly enters but is blocked beyond $\sim 20$ kpc from the central galaxy and becomes part of the circumgalactic medium (CGM). The gas pressure gradient, mainly contributed by the thermalized stellar wind and subdominantly by the energy input from the AGN, balances gravity and prevents the inflow from entering the galaxy. The SFR and BHAR are almost not affected by the normal inflow. However, if the rate of cosmological inflow were increased by a factor of 3, a small fraction of the inflow would enter the galaxy and contribute about 10\% of the gas in the galaxy. In this case, the gas density in the galaxy would increase by a factor of $\ga$ 20. This increase is not because of the additional gas supply by the inflow but the increase of gas density in the CGM caused by the inflow. Consequently, the SFR and BHAR would increase by a factor of $\sim$ 5 and $\sim 1000$ respectively. Finally, AGN feedback can perturb the motion of the inflow and heat the CGM through its intermittent outbursts.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
Francesco Paolo Rizzuto
Thorsten Naab
Antti Rantala
Peter H. Johansson
Jeremiah P. Ostriker
Nicholas C. Stone
Shihong Liao
Dimitrios Irodotou
摘要： We present $N\mathrm{-body} $ simulations, including post-Newtonian dynamics, of dense clusters of low-mass stars harbouring central black holes (BHs) with initial masses of 50, 300, and 2000 $\mathrm{M_{\odot}}$. The models are evolved with the $N\mathrm{-body} $ code \textsc{bifrost} to investigate the possible formation and growth of massive BHs by the tidal capture of stars and tidal disruption events (TDEs). We model star-BH tidal interactions using a velocity-dependent drag force, which causes orbital energy and angular momentum loss near the BH. About $\sim 20-30$ per cent of the stars within the spheres of influence of the black holes form Bahcall-Wolf cusps and prevent the systems from core collapse. Within the first 40 Myr of evolution, the systems experience 500 up to 1300 TDEs, depending on the initial cluster structure. Most ($> 95$ per cent) of the TDEs originate from stars in the Bahcall-Wolf cusp. We derive an analytical formula for the TDE rate as a function of the central BH mass, density and velocity dispersion of the clusters ($\dot{N}_{\mathrm{TDE}} \propto M\mathrm{_{BH}} \rho \sigma^{-3}$). We find that TDEs can lead a 300 $\mathrm{M_{\odot}}$ BH to reach $\sim 7000 \mathrm{M_{\odot}}$ within a Gyr. This indicates that TDEs can drive the formation and growth of massive BHs in sufficiently dense environments, which might be present in the central regions of nuclear star clusters.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
摘要： The cosmological inflow of a galaxy is speculated to be able to enter the galaxy and enhance the star formation rate (SFR) and black hole accretion rate (BHAR). In this paper, by performing high-resolution hydrodynamic simulations in the framework of {\it MACER}, we investigate the fate of the inflow and its impacts on the evolution of a massive elliptical galaxy. The inflow properties are adopted from the cosmological simulation IllustrisTNG. We find that, the inflow gas hardly enters but is blocked beyond $\sim 20$ kpc from the central galaxy and becomes part of the circumgalactic medium (CGM). The gas pressure gradient, mainly contributed by the thermalized stellar wind and subdominantly by the energy input from the AGN, balances gravity and prevents the inflow from entering the galaxy. The SFR and BHAR are almost not affected by the normal inflow. However, if the rate of cosmological inflow were increased by a factor of 3, a small fraction of the inflow would enter the galaxy and contribute about 10\% of the gas in the galaxy. In this case, the gas density in the galaxy would increase by a factor of $\ga$ 20. This increase is not because of the additional gas supply by the inflow but the increase of gas density in the CGM caused by the inflow. Consequently, the SFR and BHAR would increase by a factor of $\sim$ 5 and $\sim 1000$ respectively. Finally, AGN feedback can perturb the motion of the inflow and heat the CGM through its intermittent outbursts.
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