On the Formation of S stars from a Recent Massive Black Hole Merger in the Galactic Center
The Galactic center hosts a rotating disk of young stars between 0.05 and 0.5 pc of Sgr A*. The “S stars” at a distance <0.04 pc, however, are on eccentric orbits with nearly isotropically distributed inclinations. The dynamical origin of the S-star cluster has remained a theoretical challenge. U...
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| Format: | Article |
| Language: | English |
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IOP Publishing
2025-01-01
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| Series: | The Astrophysical Journal Letters |
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| Online Access: | https://doi.org/10.3847/2041-8213/addc5d |
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| author | Tatsuya Akiba Smadar Naoz Ann-Marie Madigan |
| author_facet | Tatsuya Akiba Smadar Naoz Ann-Marie Madigan |
| author_sort | Tatsuya Akiba |
| collection | DOAJ |
| description | The Galactic center hosts a rotating disk of young stars between 0.05 and 0.5 pc of Sgr A*. The “S stars” at a distance <0.04 pc, however, are on eccentric orbits with nearly isotropically distributed inclinations. The dynamical origin of the S-star cluster has remained a theoretical challenge. Using a series of N -body simulations, we show that a recent massive black hole merger with Sgr A* can self-consistently produce many of the orbital properties of the Galactic nuclear star cluster within 0.5 pc. A black hole merger results in a gravitational-wave recoil kick, which causes the surrounding cluster to form an apse-aligned eccentric disk. We show that stars near the inner edge of an eccentric disk migrate inward and are driven to high eccentricities and inclinations due to secular torques similar to the eccentric Kozai–Lidov mechanism. In our fiducial model, starting with a thin eccentric disk with e = 0.3, the initially unoccupied region within 0.04 pc is populated with high-eccentricity, high-inclination S stars within a few Myr. This formation channel requires a black hole of mass ${2}_{-1.2}^{+3}\times 1{0}^{5}\,{M}_{\odot }$ to have merged with Sgr A* within the last 10 Myr. |
| format | Article |
| id | doaj-art-50bbcef253ca4f2ab915f3651f469051 |
| institution | Kabale University |
| issn | 2041-8205 |
| language | English |
| publishDate | 2025-01-01 |
| publisher | IOP Publishing |
| record_format | Article |
| series | The Astrophysical Journal Letters |
| spelling | doaj-art-50bbcef253ca4f2ab915f3651f4690512025-08-20T03:29:17ZengIOP PublishingThe Astrophysical Journal Letters2041-82052025-01-019872L2710.3847/2041-8213/addc5dOn the Formation of S stars from a Recent Massive Black Hole Merger in the Galactic CenterTatsuya Akiba0https://orcid.org/0000-0002-0647-718XSmadar Naoz1https://orcid.org/0000-0002-9802-9279Ann-Marie Madigan2https://orcid.org/0000-0002-1119-5769JILA and Department of Astrophysical and Planetary Sciences, CU Boulder , Boulder, CO 80309, USA ; tatsuya.akiba@colorado.eduDepartment of Physics and Astronomy, University of California , Los Angeles, CA 90095, USA; Mani L. Bhaumik Institute for Theoretical Physics, University of California , Los Angeles, CA 90095, USAJILA and Department of Astrophysical and Planetary Sciences, CU Boulder , Boulder, CO 80309, USA ; tatsuya.akiba@colorado.eduThe Galactic center hosts a rotating disk of young stars between 0.05 and 0.5 pc of Sgr A*. The “S stars” at a distance <0.04 pc, however, are on eccentric orbits with nearly isotropically distributed inclinations. The dynamical origin of the S-star cluster has remained a theoretical challenge. Using a series of N -body simulations, we show that a recent massive black hole merger with Sgr A* can self-consistently produce many of the orbital properties of the Galactic nuclear star cluster within 0.5 pc. A black hole merger results in a gravitational-wave recoil kick, which causes the surrounding cluster to form an apse-aligned eccentric disk. We show that stars near the inner edge of an eccentric disk migrate inward and are driven to high eccentricities and inclinations due to secular torques similar to the eccentric Kozai–Lidov mechanism. In our fiducial model, starting with a thin eccentric disk with e = 0.3, the initially unoccupied region within 0.04 pc is populated with high-eccentricity, high-inclination S stars within a few Myr. This formation channel requires a black hole of mass ${2}_{-1.2}^{+3}\times 1{0}^{5}\,{M}_{\odot }$ to have merged with Sgr A* within the last 10 Myr.https://doi.org/10.3847/2041-8213/addc5dGalactic centerStellar dynamicsSupermassive black holes |
| spellingShingle | Tatsuya Akiba Smadar Naoz Ann-Marie Madigan On the Formation of S stars from a Recent Massive Black Hole Merger in the Galactic Center The Astrophysical Journal Letters Galactic center Stellar dynamics Supermassive black holes |
| title | On the Formation of S stars from a Recent Massive Black Hole Merger in the Galactic Center |
| title_full | On the Formation of S stars from a Recent Massive Black Hole Merger in the Galactic Center |
| title_fullStr | On the Formation of S stars from a Recent Massive Black Hole Merger in the Galactic Center |
| title_full_unstemmed | On the Formation of S stars from a Recent Massive Black Hole Merger in the Galactic Center |
| title_short | On the Formation of S stars from a Recent Massive Black Hole Merger in the Galactic Center |
| title_sort | on the formation of s stars from a recent massive black hole merger in the galactic center |
| topic | Galactic center Stellar dynamics Supermassive black holes |
| url | https://doi.org/10.3847/2041-8213/addc5d |
| work_keys_str_mv | AT tatsuyaakiba ontheformationofsstarsfromarecentmassiveblackholemergerinthegalacticcenter AT smadarnaoz ontheformationofsstarsfromarecentmassiveblackholemergerinthegalacticcenter AT annmariemadigan ontheformationofsstarsfromarecentmassiveblackholemergerinthegalacticcenter |