arXiv subjects

Margarita Sobolenko

Publications and source records attributed to Margarita Sobolenko.

5 recordsLinked to original sources

arXiv2026

The effect of triaxial galaxy shapes on the dynamics of triple supermassive black holes in a cosmological context

The hierarchical nature of galaxy formation in the Lambda cold dark matter ($Λ$CDM) cosmological framework model often leads to the presence of multiple supermassive black holes (SMBHs) in the galactic nuclei. The timescale over which galaxies merge plays a crucial role in shaping the dynamical evolution and the merger dynamics of their central SMBHs. While binary SMBH evolution has been extensively studied, the long-term dynamics of triple SMBH systems, especially in realistic, nonspherical galactic potentials, still remain less understood. In this work, we investigated the role of triaxiality in shaping the dynamical evolution of three SMBH triple systems taken from the ROMULUS25 cosmological simulation embedded in triaxial stellar backgrounds to find common dynamical evolution patterns and estimate typical coalescence times using high-resolution gravitodynamical $\textit{N}$-body simulations. We explored a range of orbital configurations and host galaxy shapes with initial conditions from the ROMULUS25 data and tracked the orbital evolution from the galactic inspiral to the formation of hard binaries at sub-parsec separations and used the observed hardening rates to estimate the time of coalescence. In all cases, the two heaviest black holes form an efficiently hardening binary, which merges within the Hubble time, while the third black hole (BH) either forms a stable hierarchical triple system with the heavier binary or remains on a wide galactic orbit. Finally, we analyzed the triaxiality of the galactic remnant from our simulations and conclude that the initial triaxial shape of the galaxies does not significantly change the final dynamical outcome of the triple systems.

astro-ph.GA↗

arXiv2025

Intermediate Mass Black Hole Binary Evolution in Nuclear Star Clusters: the effect of the stellar mass black hole population

In this study, we investigate the dynamics of Intermediate-Mass Black Hole (IMBH) binaries within Nuclear Star Clusters (NSCs) that contain a population of stellar-mass black holes (BHs). We examine how these stellar and BH populations influence the dynamics of the IMBH binary and, in turn, how the evolving IMBH binary affects the surrounding stellar and BH populations. We conduct high-resolution $N$-body simulations of NSCs constructed based on observational parameters from two local dwarf galaxies: NGC205 and NGC404. For the first time, we achieve a star particle mass resolution of $1\rm\;M_{\odot}$ and a BH mass resolution of $10\rm\;M_{\odot}$. This level of resolution is crucial for accurately modeling the collisional dynamics of these dense systems. Including stellar-mass BHs within the stellar population significantly influences the IMBH binary dynamics, nearly doubling the sinking rate and halving the merger time. During the initial phase of the inspiral, the IMBH binary disrupts both the stellar and BH cusps. However, the BH cusp quickly regains its steep slope due to its shorter relaxation time and continues to dominate the evolution of the IMBH binary, despite being much less massive compared to the stellar component. We uncover an interesting mechanism in which BHs first efficiently extract energy from the IMBH binary and then transfer this energy to the surrounding stars, allowing the BHs to spiral back toward the center of the system and restart the process. Our results imply that, although stellar mass BHs are a minor component of a stellar population, they can significantly facilitate IMBH growth within NSCs via mergers. We also notice that these dense systems can potentially boost Intermediate Mass Ratio Inspirals (IMRIs) predominantly on radial orbits.

astro-ph.GA↗

arXiv2025

The effect of triaxiality on the dynamics of triple supermassive black holes in a cosmological context

The hierarchical nature of galaxy formation in the $Λ$CDM framework often leads to multiple supermassive black holes (SMBHs) in the galactic nuclei. The timescale over which galaxies merge, plays a crucial role in shaping the dynamical evolution and the merger dynamics of their central SMBHs. While binary SMBH evolution is well studied, the long-term dynamics of triple SMBH systems, particularly in non-spherical potentials, remain less understood. We investigate the role of triaxiality in the evolution and dynamics of triple SMBHs with initial conditions drawn from the ROMULUS25 cosmological simulation, using high-resolution gravitodynamical N-body simulations. We explore different orbital configurations and host shapes, tracking the evolution from galactic inspiral to hard binary formation at sub-parsec scales. In all cases, the two most massive SMBHs form a rapidly hardening binary that coalesces within a fraction of a Hubble time, while the third forms a stable hierarchical triple system with the heavier binary, or remains on a wide orbit.

astro-ph.GA↗

arXiv2024

Milky Way globular clusters on cosmological timescales. IV. Guests in the outer Solar System

The present epoch of the Gaia success gives us a possibility to predict the dynamical evolution of our Solar System in the global Galactic framework with high precision. We statistically investigated the total interaction of globular clusters with the Solar System during six billion years of look-back time. We estimated the gravitational influence of globular clusters' flyby onto the Oort cloud system. To perform the realistic orbital dynamical evolution for each individual cluster, we used our own high-order parallel dynamical $N$ body $φ$-GPU code that we developed. To reconstruct the orbital trajectories of clusters, we used five external dynamical time variable galactic potentials selected from the IllustrisTNG-100 cosmological database and one static potential. To detect a cluster's close passages near the Solar System, we adopted a simple distance criterion of below 200 pc. To take into account a cluster's measurement errors (based on Gaia DR3), we generated 1000 initial positions and velocity randomizations for each cluster in each potential. We found 35 globular clusters that have had close passages near the Sun in all the six potentials during the whole lifetime of the Solar System. We can conclude that at a relative distance of 50 pc between a GC and the SolS, we obtain on average $\sim 15$\% of the close passage probability over all six billion years, and at $dR=100$ pc, we get on average $\sim 35$\% of the close passage probability over all six billion years. The globular clusters BH_140, UKS_1, and Djorg_1 have a mean minimum relative distance to the Sun of 9, 19, and 17 pc, respectively. We can assume that a globular cluster with close passages near the Sun is not a frequent occurrence but also not an exceptional event in the Solar System's lifetime.

astro-ph.GA↗

arXiv2021

Merging timescale for supermassive black hole binary in interacting galaxy NGC 6240

One of the main possible way of creating the supermassive black hole (SMBH) is a so call hierarchical merging scenario. Central SMBHs at the final phase of interacting and coalescing host-galaxies are observed as SMBH binary (SMBHB) candidates at different separations from hundreds of pc to mpc. Today one of the strongest SMBHB candidate is a ULIRG galaxy NGC 6240 which was X-ray spatially and spectroscopically resolved by Chandra. Dynamical calculation of central SMBHBs merging in a dense stellar environment allows us to retrace their evolution from kpc to mpc scales. The main goal of our dynamical modeling was to reach the final, gravitational wave (GW) emission regime for the model BHs. We present the direct N-body simulations with up to one million particles and relativistic post-Newtonian corrections for the SMBHs particles up to 3.5 post-Newtonian terms. Generally speaking, the set of initial physical conditions can strongly effect of our merging time estimations. But in a range of our parameters, we did not find any strong correlation between merging time and BHs mass or BH to bulge mass ratios. Varying the model numerical parameters (such as particle number - N) makes our results quite robust and physically more motivated. From our 20 models we found the upper limit of merging time for central SMBHB is less than $\sim$55 Myr. This concrete number are valid only for our set of combination of initial mass ratios. Further detailed research of rare dual/multiple BHs in dense stellar environment (based on observations data) can clarify the dynamical co-evolution of central BHs and their host-galaxies.

astro-ph.GA↗