JWST Observations of the Double Nucleus in NGC 4486B: Possible Evidence for a Recent Binary SMBH Merger and Recoil

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 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mi class="MJX-tex-calligraphic" mathvariant="script">M</mml:mi> <mml:mi>BH</mml:mi> </mml:msub> <mml:mo>=</mml:mo> <mml:mn>3.6</mml:mn> <mml:mo>±</mml:mo> <mml:mn>0.7</mml:mn> <mml:mo>×</mml:mo> <mml:mn>1</mml:mn> <mml:msup> <mml:mn>0</mml:mn> <mml:mn>8</mml:mn> </mml:msup> </mml:math> (∼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 &gt; 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.

Authors

Institutions

Publication Details

Journal
The Astrophysical Journal Letters
Published
2026-04-06
DOI
https://doi.org/10.3847/2041-8213/ae52ef
Primary Topic
Galaxies: Formation, Evolution, Phenomena
Type
article
Field-Weighted Citation Impact
0.00

Funders

Controls
|||
ALL TIME
JAN
FEB
MAR
APR
MAY
JUN
JUL
AUG
SEP
OCT
article

JWST Observations of the Double Nucleus in NGC 4486B: Possible Evidence for a Recent Binary SMBH Merger and Recoil

S. Jha, Laura Ferrarese, Chengze Liu, Andrea V. Macciò et al.
The Astrophysical Journal Letters
Galaxies: Formation, Evolution, Phenomena
article

JWST Observations of the Double Nucleus in NGC 4486B: Possible Evidence for a Recent Binary SMBH Merger and Recoil

S. Jha, Laura Ferrarese, Chengze Liu, Andrea V. Macciò, Misty C. Bentz, Matthew A. Taylor, Shashank Dattathri, Frank C. van den Bosch, Solveig Thompson, Tatsuya Akiba, Tyrone E. Woods, Fazeel Mahmood Khan, Ann-Marie Madigan, Holger Baumgardt, Kristen C. Dage, Behzad Tahmasebzadeh, Monica Valluri, M. J. Drinkwater, Eric W. Peng, Patrick Côté, Kelly Holley-Bockelmann
article en

Abstract

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 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mi class="MJX-tex-calligraphic" mathvariant="script">M</mml:mi> <mml:mi>BH</mml:mi> </mml:msub> <mml:mo>=</mml:mo> <mml:mn>3.6</mml:mn> <mml:mo>±</mml:mo> <mml:mn>0.7</mml:mn> <mml:mo>×</mml:mo> <mml:mn>1</mml:mn> <mml:msup> <mml:mn>0</mml:mn> <mml:mn>8</mml:mn> </mml:msup> </mml:math> (∼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 &gt; 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.

The Astrophysical Journal LettersVol. 1001(1)
Joint Institute for Laboratory Astrophysics (US), The University of Queensland (AU), University of Calgary (CA), Georgia State University (US), Shanghai Jiao Tong University (CN), University of Colorado Boulder (US), Vanderbilt University (US), Curtin University (AU), University of Victoria (CA), University of Michigan (US), Whitney Museum of American Art (US), Yale University (US), NSF NOIRLab (US), National Research Council Canada (CA), International Centre for Radio Astronomy Research (AU), University of Manitoba (CA), Villanova University (US), Fisk University (US)
Villanova University, New York University Abu Dhabi, Space Telescope Science Institute, York University, National Natural Science Foundation of China, Higher Education Discipline Innovation Project, Tamkeen, Canadian Space Agency
Openalex Percentile: Top 98%
Galaxies: Formation, Evolution, Phenomena
DOIOpen Access PDFOpenAlex
AI Navigator

Ask Laika to Summarize, Analyze, and Connect papers live on the map.

Summarize Papers & Methodologies

Extract key findings, datasets, and comparative methods across publications.

Benchmark Rankings & Visual Analytics

Rank top research institutions, authors, funders, topics, and journals by Field-Weighted Citation Impact (FWCI) and paper volume with instant charts.

Connect Distant Disciplines

Bridge topological clusters on the map to find hidden collaborative intersections.