2026-04-06 ミシガン大学
This recent image from the Vera Rubin Observatory shows a portion of the Virgo Cluster, where galaxies are packed so densely that they’re pulling each other apart. Because of this, some galaxies have “overmassive” black holes at their core. That is, because the environment of the cluster has plucked away so many stars from some galaxies, their central black holes make up an unusually large fraction of their galaxies’ total mass. Image credit: RubinObs/NOIRLab/SLAC/NSF/DOE/AURA
＜関連情報＞
- https://news.umich.edu/my-what-big-black-holes-you-have-tales-from-the-virgo-cluster/
- https://iopscience.iop.org/article/10.3847/2041-8213/ae52ef
- https://iopscience.iop.org/article/10.3847/2041-8213/ae028e
- https://iopscience.iop.org/article/10.3847/2041-8213/adf728
JWSTによるNGC 4486Bの二重核の観測：最近の連星超大質量ブラックホールの合体と反動の可能性を示す証拠 JWST Observations of the Double Nucleus in NGC 4486B: Possible Evidence for a Recent Binary SMBH Merger and Recoil
Behzad Tahmasebzadeh, Monica Valluri, Shashank Dattathri, Tatsuya Akiba, Fazeel Mahmood Khan, Matthew A. Taylor, Haruka Yoshino, Solveig Thompson, Ann-Marie Madigan, Frank C. van den Bosch,…
The Astrophysical Journal Letters Published: 2026 April 6
DOI:10.3847/2041-8213/ae52ef
Abstract
A recent study of the compact elliptical galaxy NGC 4486B using JWST Near-Infrared Spectrograph integral-field-unit-mode kinematics confirmed a supermassive black hole (SMBH) of mass MBH=3.6±0.7×108(∼8% of the stellar mass). In addition to its double nucleus, the nuclear kinematics show pronounced asymmetries: a velocity dispersion peak displaced by 6 pc from the galaxy center and a ∼16 km s−1 offset in the mean stellar line-of-sight velocity near the SMBH. We examine the origin of the 12 pc double nucleus and show that the observations favor an SMBH surrounded by an eccentric nuclear disk (END). One proposed formation pathway for ENDs involves a gravitational-wave (GW) recoil of the SMBH following a binary merger. Our orbit superposition models contain ∼50% retrograde stars at the edge of the nuclear region, in agreement with END formation simulations. We infer a premerger mass ratio q > 0.15 and a recoil kick of ∼340 km s−1. Our N-body simulations show that with such a kick, the SMBH returns to the center within ∼30 Myr. Its flat central core is also consistent with earlier “binary black hole scouring.” We test two alternative mechanisms—buoyancy-driven oscillations and a premerger SMBH binary—but neither reproduces the observed offsets, favoring the GW kick scenario. Our N-body simulations also show that a prograde SMBH binary in a rotating host can become trapped in a corotation resonance, delaying coalescence. Although NGC 4486B is an old galaxy near the Virgo Cluster center, its SMBH appears to have merged only recently, making its nucleus a rare nearby laboratory for postmerger SMBH dynamics.
JWST/NIRSpec+IFUにより、極小の超コンパクト矮小銀河に存在する超大質量ブラックホールが発見された A Supermassive Black Hole in a Diminutive Ultracompact Dwarf Galaxy Discovered with JWST/NIRSpec+IFU
Matthew A. Taylor, Behzad Tahmasebzadeh, Solveig Thompson, Eugene Vasiliev, Monica Valluri, Michael J. Drinkwater, Patrick Côté, Laura Ferrarese, Joel Roediger, Holger Baumgardt,…
The Astrophysical Journal Letters Published: 2025 September 18
DOI:10.3847/2041-8213/ae028e
Abstract
The integral-field unit mode of the Near-Infrared Spectrograph (NIRSpec+IFU) mounted on the James Webb Space Telescope has now enabled kinematic studies of smaller and less massive compact stellar systems in which to search for central massive black holes (BHs) than ever before. We present here the first such detection using NIRSpec+IFU in its highest resolution (R ∼ 2700) mode. We report the detection of a central BH with mass MBH= 2.1 ± 1.1 × 106 M⊙ (1σ uncertainties) in UCD736 orbiting within the Virgo galaxy cluster. Schwarzschild modeling of the 1D kinematic profile rules out a zero-mass central BH at the 3σ level; however, two other independent modeling approaches fail to rule out a zero-mass BH at >1σ significance. The presence of such a massive BH strongly argues against a globular cluster origin of this ultracompact dwarf galaxy (UCD), and rather suggests a tidally stripped formation route from a former ≳109 M⊙ dwarf galaxy host. This represents the detection of a BH in the most compact (rh ≈ 15 pc) stellar system to date, with a MBH corresponding to ∼8% of the system’s stellar mass, roughly in line with previously reported UCD BH detections and comparable to the BH detected in the compact elliptical galaxy NGC4486B.
JWSTによるNGC 4486Bの超大質量ブラックホールの画像 A JWST View of the Overmassive Black Hole in NGC 4486B
Behzad Tahmasebzadeh, Matthew A. Taylor, Monica Valluri, Haruka Yoshino, Eugene Vasiliev, Michael J. Drinkwater, Solveig Thompson, Kristen Dage, Patrick Côté, Laura Ferrarese,…
The Astrophysical Journal Letters Published: 2025 August 14
DOI:10.3847/2041-8213/adf728
Abstract
We present a new stellar dynamical measurement of the supermassive black hole 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 MBH =3.6+0.7-0.7×108M⊙, slightly lower but significantly more precise than previous estimates. However, since our models do not account for the nonequilibrium nature of the double nucleus, this value may represent a lower limit. Across all tested dynamical models, the inferred MBH /M* ratio ranges from ∼4% to 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″. 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 MDM /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.
