A JWST View of the Overmassive Black Hole in NGC 4486B
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| Format: | Preprint |
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2025
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| _version_ | 1866916875512840192 |
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| author | Tahmasebzadeh, Behzad Taylor, Matthew A. Valluri, Monica Yoshino, Haruka Vasiliev, Eugene Drinkwater, Michael J. Thompson, Solveig Dage, Kristen Côté, Patrick Ferrarese, Laura Akiba, Tatsuya Baldassare, Vivienne Bentz, Misty C. Blakeslee, John P. Baumgardt, Holger Ko, Youkyung Liu, Chengze Madigan, Ann-Marie Peng, Eric W. Roediger, Joel Wang, Kaixiang Woods, Tyrone E. |
| author_facet | Tahmasebzadeh, Behzad Taylor, Matthew A. Valluri, Monica Yoshino, Haruka Vasiliev, Eugene Drinkwater, Michael J. Thompson, Solveig Dage, Kristen Côté, Patrick Ferrarese, Laura Akiba, Tatsuya Baldassare, Vivienne Bentz, Misty C. Blakeslee, John P. Baumgardt, Holger Ko, Youkyung Liu, Chengze Madigan, Ann-Marie Peng, Eric W. Roediger, Joel Wang, Kaixiang Woods, Tyrone E. |
| contents | We present a new stellar dynamical measurement of the supermassive black hole (SMBH) in the compact elliptical galaxy NGC 4486B, based on integral field spectroscopy with JWST/NIRSpec. The two-dimensional kinematic maps reveal a resolved double nucleus and a velocity dispersion peak offset from the photometric center. Utilizing two independent methods-Schwarzschild orbit-superposition and Jeans Anisotropic Modeling-we tightly constrain the black hole mass by fitting the full line-of-sight velocity distribution. Our axisymmetric Schwarzschild models yield a best-fit black hole mass of $M_{BH} = 3.6^{+0.7}_{-0.7} \times 10^8 \, M_{\odot}$, slightly lower but significantly more precise than previous estimates. However, since our models do not account for the non-equilibrium nature of the double nucleus, this value may represent a lower limit. Across all tested dynamical models, the inferred $M_{BH}/M_*$ ratio ranges from ~ 4-13%, providing robust evidence for an overmassive SMBH in NGC 4486B. Combined with the galaxy's location deep within the Virgo Cluster, our results support the interpretation that NGC 4486B is the tidally stripped remnant core of a formerly massive galaxy. As the JWST/NIRSpec field of view is insufficient to constrain the dark matter halo, we incorporate archival ground-based long-slit kinematics extending to 5 arcsec. While this provides some leverage on the dark matter content, the constraints remain relatively weak. We place only an upper limit on the dark matter fraction, with $M_{DM}/M_{*} < 0.5$ within 1 kpc-well beyond the effective radius. The inferred black hole mass remains unchanged with or without a dark matter halo. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2505_14676 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | A JWST View of the Overmassive Black Hole in NGC 4486B Tahmasebzadeh, Behzad Taylor, Matthew A. Valluri, Monica Yoshino, Haruka Vasiliev, Eugene Drinkwater, Michael J. Thompson, Solveig Dage, Kristen Côté, Patrick Ferrarese, Laura Akiba, Tatsuya Baldassare, Vivienne Bentz, Misty C. Blakeslee, John P. Baumgardt, Holger Ko, Youkyung Liu, Chengze Madigan, Ann-Marie Peng, Eric W. Roediger, Joel Wang, Kaixiang Woods, Tyrone E. Astrophysics of Galaxies We present a new stellar dynamical measurement of the supermassive black hole (SMBH) in the compact elliptical galaxy NGC 4486B, based on integral field spectroscopy with JWST/NIRSpec. The two-dimensional kinematic maps reveal a resolved double nucleus and a velocity dispersion peak offset from the photometric center. Utilizing two independent methods-Schwarzschild orbit-superposition and Jeans Anisotropic Modeling-we tightly constrain the black hole mass by fitting the full line-of-sight velocity distribution. Our axisymmetric Schwarzschild models yield a best-fit black hole mass of $M_{BH} = 3.6^{+0.7}_{-0.7} \times 10^8 \, M_{\odot}$, slightly lower but significantly more precise than previous estimates. However, since our models do not account for the non-equilibrium nature of the double nucleus, this value may represent a lower limit. Across all tested dynamical models, the inferred $M_{BH}/M_*$ ratio ranges from ~ 4-13%, providing robust evidence for an overmassive SMBH in NGC 4486B. Combined with the galaxy's location deep within the Virgo Cluster, our results support the interpretation that NGC 4486B is the tidally stripped remnant core of a formerly massive galaxy. As the JWST/NIRSpec field of view is insufficient to constrain the dark matter halo, we incorporate archival ground-based long-slit kinematics extending to 5 arcsec. While this provides some leverage on the dark matter content, the constraints remain relatively weak. We place only an upper limit on the dark matter fraction, with $M_{DM}/M_{*} < 0.5$ within 1 kpc-well beyond the effective radius. The inferred black hole mass remains unchanged with or without a dark matter halo. |
| title | A JWST View of the Overmassive Black Hole in NGC 4486B |
| topic | Astrophysics of Galaxies |
| url | https://arxiv.org/abs/2505.14676 |