The Supermassive Black Hole in the Nearby Spiral Galaxy M81: A Robust Mass from JWST/NIRSpec Stellar Dynamics
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| Main Authors: | , , , , , , , , , , , |
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| Format: | Preprint |
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2026
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| _version_ | 1866912845578371072 |
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| author | Nguyen, Dieu D. Le, Tuan N. Cappellari, Michele Ngo, Hai N. Le, Tinh Q. T. Ho, Tien H. T. Nguyen, Long Q. T. Gallo, Elena Zou, Fan Perna, Michele Thatte, Niranjan Pereira-Santaella, Miguel |
| author_facet | Nguyen, Dieu D. Le, Tuan N. Cappellari, Michele Ngo, Hai N. Le, Tinh Q. T. Ho, Tien H. T. Nguyen, Long Q. T. Gallo, Elena Zou, Fan Perna, Michele Thatte, Niranjan Pereira-Santaella, Miguel |
| contents | Despite its proximity, the mass of the supermassive black hole (SMBH) in the spiral galaxy M81 (NGC~3031) has remained uncertain, with previous dynamical measurements being unreliable. We present the first robust stellar-dynamical measurement of its mass using high-resolution, two-dimensional kinematics from JWST/NIRSpec observations of the central $3''\times3''$. By tracing stellar motions in the near-infrared, our data penetrate the obscuring nuclear dust and allow for the separation of stellar light from the non-thermal AGN continuum. We modeled the kinematics using JAM within a Bayesian framework, exploring a comprehensive suite of models that systematically account for uncertainties in the point-spread function, orbital anisotropy, and stellar mass-to-light ratio. This ensemble modeling approach demonstrates that a central dark mass unambiguously drives the central rise in velocity dispersion. The models yield a robust SMBH mass of $M_{\rm BH} = (4.78^{+0.07}_{-0.10})\times10^7$ M$_\odot$. This result resolves a long-standing uncertainty in the mass of M81's black hole and provides a crucial, reliable anchor point for SMBH-galaxy scaling relations. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2601_17439 |
| institution | arXiv |
| publishDate | 2026 |
| record_format | arxiv |
| spellingShingle | The Supermassive Black Hole in the Nearby Spiral Galaxy M81: A Robust Mass from JWST/NIRSpec Stellar Dynamics Nguyen, Dieu D. Le, Tuan N. Cappellari, Michele Ngo, Hai N. Le, Tinh Q. T. Ho, Tien H. T. Nguyen, Long Q. T. Gallo, Elena Zou, Fan Perna, Michele Thatte, Niranjan Pereira-Santaella, Miguel Astrophysics of Galaxies Despite its proximity, the mass of the supermassive black hole (SMBH) in the spiral galaxy M81 (NGC~3031) has remained uncertain, with previous dynamical measurements being unreliable. We present the first robust stellar-dynamical measurement of its mass using high-resolution, two-dimensional kinematics from JWST/NIRSpec observations of the central $3''\times3''$. By tracing stellar motions in the near-infrared, our data penetrate the obscuring nuclear dust and allow for the separation of stellar light from the non-thermal AGN continuum. We modeled the kinematics using JAM within a Bayesian framework, exploring a comprehensive suite of models that systematically account for uncertainties in the point-spread function, orbital anisotropy, and stellar mass-to-light ratio. This ensemble modeling approach demonstrates that a central dark mass unambiguously drives the central rise in velocity dispersion. The models yield a robust SMBH mass of $M_{\rm BH} = (4.78^{+0.07}_{-0.10})\times10^7$ M$_\odot$. This result resolves a long-standing uncertainty in the mass of M81's black hole and provides a crucial, reliable anchor point for SMBH-galaxy scaling relations. |
| title | The Supermassive Black Hole in the Nearby Spiral Galaxy M81: A Robust Mass from JWST/NIRSpec Stellar Dynamics |
| topic | Astrophysics of Galaxies |
| url | https://arxiv.org/abs/2601.17439 |