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| Format: | Preprint |
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2025
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| Online-Zugang: | https://arxiv.org/abs/2511.00661 |
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| author | Mazoochi, Farideh Tabatabaei, Fatemeh S. Barnes, Ashley T. Colzi, Laura García, Pablo Henkel, Christian Hu, Yue Longmore, Steven N. Martín, Sergio Sánchez-Monge, Álvaro Rivilla, Víctor M. Schmiedeke, Anika Ott, Juergen Walke, Daniel L. Wang, Q. Daniel Williams, Gwenllian M. Zhang, Suinan |
| author_facet | Mazoochi, Farideh Tabatabaei, Fatemeh S. Barnes, Ashley T. Colzi, Laura García, Pablo Henkel, Christian Hu, Yue Longmore, Steven N. Martín, Sergio Sánchez-Monge, Álvaro Rivilla, Víctor M. Schmiedeke, Anika Ott, Juergen Walke, Daniel L. Wang, Q. Daniel Williams, Gwenllian M. Zhang, Suinan |
| contents | The circumnuclear region of the Galactic Center offers a unique laboratory to study energy balance and structure formation around Sgr A$\star$. This work investigates thermal and nonthermal processes within 7 pc distance from Sgr A$\star$. Using MeerKAT 1.3 GHz radio continuum data and ALMA H40 radio recombination line emission from the ACES survey, we separate free-free and synchrotron components at $\sim$0.2 pc resolution. With a thermal fraction of $\simeq$13%, the 1.3 GHz emission shows tight correlations with the Herschel PACS infrared data. The correlation between the equipartition magnetic field and molecular gas traced by JCMT $^{12}$CO (J=3$\rightarrow$2) observations reveals a balance between the magnetic field, cosmic rays, and molecular gas pressures south of the circumnuclear disk on $\sim$0.7 pc scales. Unlike the magnetic field and ionized gas, the molecular gas density declines in the cavity (R$\leq$2 pc) toward the center, likely due to feedback from Sgr A$\star$. We find that nonthermal pressure from turbulent gas nearly balances magnetic and cosmic ray pressures and exceeds thermal pressure by two orders of magnitude. The medium surrounding Sgr A$\star$ is filled by a low-$β$ (thermal-to-magnetic energy), supersonic plasma, with an Alfvén Mach number $\simeq$ 4 (assuming equipartition). Analysis of the mass-to-magnetic flux ratio suggests that the circumnuclear region is mostly subcritical and, therefore, the magnetic field can help stabilize gas clouds against gravitational collapse. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2511_00661 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | Nonthermal Pressures: Key to Energy Balance and Structure Formation Near Sgr A* in the Milky Way Mazoochi, Farideh Tabatabaei, Fatemeh S. Barnes, Ashley T. Colzi, Laura García, Pablo Henkel, Christian Hu, Yue Longmore, Steven N. Martín, Sergio Sánchez-Monge, Álvaro Rivilla, Víctor M. Schmiedeke, Anika Ott, Juergen Walke, Daniel L. Wang, Q. Daniel Williams, Gwenllian M. Zhang, Suinan Astrophysics of Galaxies The circumnuclear region of the Galactic Center offers a unique laboratory to study energy balance and structure formation around Sgr A$\star$. This work investigates thermal and nonthermal processes within 7 pc distance from Sgr A$\star$. Using MeerKAT 1.3 GHz radio continuum data and ALMA H40 radio recombination line emission from the ACES survey, we separate free-free and synchrotron components at $\sim$0.2 pc resolution. With a thermal fraction of $\simeq$13%, the 1.3 GHz emission shows tight correlations with the Herschel PACS infrared data. The correlation between the equipartition magnetic field and molecular gas traced by JCMT $^{12}$CO (J=3$\rightarrow$2) observations reveals a balance between the magnetic field, cosmic rays, and molecular gas pressures south of the circumnuclear disk on $\sim$0.7 pc scales. Unlike the magnetic field and ionized gas, the molecular gas density declines in the cavity (R$\leq$2 pc) toward the center, likely due to feedback from Sgr A$\star$. We find that nonthermal pressure from turbulent gas nearly balances magnetic and cosmic ray pressures and exceeds thermal pressure by two orders of magnitude. The medium surrounding Sgr A$\star$ is filled by a low-$β$ (thermal-to-magnetic energy), supersonic plasma, with an Alfvén Mach number $\simeq$ 4 (assuming equipartition). Analysis of the mass-to-magnetic flux ratio suggests that the circumnuclear region is mostly subcritical and, therefore, the magnetic field can help stabilize gas clouds against gravitational collapse. |
| title | Nonthermal Pressures: Key to Energy Balance and Structure Formation Near Sgr A* in the Milky Way |
| topic | Astrophysics of Galaxies |
| url | https://arxiv.org/abs/2511.00661 |