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Black Hole

Lensing of space time around a black hole. At Oxford we study black holes observationally and theoretically on all size and time scales - it is some of our core work.

Credit: ALAIN RIAZUELO, IAP/UPMC/CNRS. CLICK HERE TO VIEW MORE IMAGES.

Michele Cappellari

Professor of Astrophysics

Research theme

  • Astronomy and astrophysics

Sub department

  • Astrophysics

Research groups

  • Galaxy formation and evolution
  • Extremely Large Telescope
michele.cappellari@physics.ox.ac.uk
Telephone: 01865 (2)73647
Denys Wilkinson Building, room 755
  • About
  • Publications

Simulating Intermediate Black Hole Mass Measurements for a Sample of Galaxies with Nuclear Star Clusters Using ELT/HARMONI High Spatial Resolution Integral-field Stellar Kinematics

Astronomical Journal American Astronomical Society 170:2 (2025) 124

Authors:

Dieu D Nguyen, Michele Cappellari, Hai N Ngo, Tinh QT Le, Tuan N Le, Khue NH Ho, An K Nguyen, Phong T On, Huy G Tong, Niranjan Thatte, Miguel Pereira-Santaella

Abstract:

Understanding the demographics of intermediate-mass black holes (IMBHs, MBH ≈ 102–105 M⊙) in low-mass galaxies is key to constraining black hole seed formation models, but detecting them is challenging due to their small gravitational sphere of influence (SOI). The upcoming Extremely Large Telescope (ELT) High Angular Resolution Monolithic Optical and Near-infrared Integral Field Spectrograph (HARMONI) instrument, with its high angular resolution, offers a promising solution. We present simulations assessing HARMONI’s ability to measure IMBH masses in nuclear star clusters (NSCs) of nearby dwarf galaxies. We selected a sample of 44 candidates within 10 Mpc. For two representative targets, NGC 300 and NGC 3115 dw01, we generated mock HARMONI integral-field data cubes using realistic inputs derived from Hubble Space Telescope imaging, stellar population models, and Jeans anisotropic models (JAM), assuming IMBH masses up to 1% of the NSC mass. We simulated observations across six near-infrared gratings at 10 mas resolution. Analyzing the mock data with standard kinematic extraction and JAM models in a Bayesian framework, we demonstrate that HARMONI can resolve the IMBH SOI and accurately recover masses down to ≈0.5% of the NSC mass within feasible exposure times. These results highlight HARMONI’s potential to revolutionize IMBH studies.
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TDCOSMO XXIII. First spatially resolved kinematics of the lens galaxy obtained using JWST-NIRSpec to improve time-delay cosmography

(2025)

Authors:

Anowar J Shajib, Tommaso Treu, Sherry H Suyu, David Law, AkÄ N Yıldırım, Michele Cappellari, Aymeric Galan, Shawn Knabel, Han Wang, Simon Birrer, Frà dà ric Courbin, Christopher D Fassnacht, Joshua A Frieman, Alejandra Melo, Takahiro Morishita, Pritom Mozumdar, Dominique Sluse, Massimo Stiavelli
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Project Dinos II: redshift evolution of dark and luminous matter density profiles in strong-lensing elliptical galaxies across 0.1 < z < 0.9

Monthly Notices of the Royal Astronomical Society Oxford University Press 541:1 (2025) 1-27

Authors:

William Sheu, Anowar J Shajib, Tommaso Treu, Alessandro Sonnenfeld, Simon Birrer, Michele Cappellari, Lindsay J Oldham, Chin Yi Tan

Abstract:

We present a new measurement of the dark and luminous matter distribution of massive elliptical galaxies, and their evolution with redshift, by combining strong lensing and dynamical observables. Our sample of 56 lens galaxies covers a redshift range of . By combining new Hubble Space Telescope imaging with previously observed velocity dispersion and line-of-sight measurements, we decompose the luminous matter profile from the dark matter profile and perform a Bayesian hierarchical analysis to constrain the population-level properties of both profiles. We find that the inner slope of the dark matter density profile (‘cusp’; ) is consistent ( with intrinsic scatter) with a standard Navarro–Frenk–White (NFW; ) at . Additionally, we find an appreciable evolution with redshift () resulting in a shallower slope (of tension from NFW) at redshifts . This is in excellent agreement with previous population-level observational studies, as well as with predictions from hydrodynamical simulations such as IllustrisTNG. We also find the stellar mass-to-light ratio at the population level is consistent with that of a Salpeter initial mass function, a small stellar mass-to-light gradient [, with ], and isotropic stellar orbits. Our averaged total mass density profile is consistent with a power-law profile within 0.25 to 4 Einstein radii (), with an internal mass-sheet transformation parameter consistent with no mass sheet. Our findings confirm the validity of the standard mass models used for time-delay cosmography.
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Project Dinos II: Redshift evolution of dark and luminous matter density profiles in strong-lensing elliptical galaxies across $0.1 < z < 0.9$

(2025)

Authors:

William Sheu, Anowar J Shajib, Tommaso Treu, Alessandro Sonnenfeld, Simon Birrer, Michele Cappellari, Lindsay J Oldham, Chin Yi Tan
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XXII. Accurate stellar velocity dispersions of the SL2S lens sample and the lensing mass fundamental plane

(2025)

Authors:

Pritom Mozumdar, Shawn Knabel, Tommaso Treu, Alessandro Sonnenfeld, Anowar J Shajib, Michele Cappellari, Carlo Nipoti
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