The M87 Black Hole Mass from JWST and Keck Stellar Kinematics Spanning 10 pc to 10 kpc
Abstract
We combine JWST NIRSpec and Keck KCWI observations to construct a contiguous 2D map of M87's stellar kinematics spanning three decades in projected radius, from ∼10 pc to ∼10 kpc, and measure the mass of its central supermassive black hole. The innermost stellar kinematic measurements probe projected radii as small as ∼3% of the black hole's sphere of influence radius, or approximately 30,000 Schwarzschild radii. The NIRSpec spectra within R < 0.45'' are contaminated by quasiperiodic "wiggle" artifacts. We develop hyphen, which uses detector spectral traces to predict how the wiggle frequency varies with wavelength, then fits and subtracts the wiggle pattern from each spectrum in each exposure before combining the data. The cleaned spectra reveal a pronounced central rise in stellar velocity dispersion and h4. Triaxial Schwarzschild stellar orbit modeling with the TriOS code, fitting ∼5,000 kinematic constraints across 618 spatial bins from JWST and Keck, yields a black hole mass of MBH=(5.38 ± 0.13± 0.22)×109 M⊙. This result is consistent with our prior KCWI-only determination but with the statistical uncertainty reduced by a factor of 2-3, now subdominant to the systematic uncertainty in the distance (D) to M87. Our inferred mass-to-distance ratio is θg=GMBH/(c2 D) = 3.16 ± 0.08 μas, whose 90% credible interval overlaps with that obtained from the multi-epoch Event Horizon Telescope (EHT) analysis, providing a robust and independent prior for future EHT studies.
Related
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BibTeX
@misc{liepold2026black,
title = {{The M87 Black Hole Mass from JWST and Keck Stellar Kinematics Spanning 10 pc to 10 kpc}},
author = {Emily R. Liepold and Chung-Pei Ma and Refa M. Al-Amri and Jonelle L. Walsh},
howpublished = {arXiv},
year = {2026},
month = nov,
doi = {10.48550/arxiv.2611.05486},
eprint = {2611.05486},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2611.05486},
}
RIS
TY - UNPB
TI - The M87 Black Hole Mass from JWST and Keck Stellar Kinematics Spanning 10 pc to 10 kpc
AU - Emily R. Liepold
AU - Chung-Pei Ma
AU - Refa M. Al-Amri
AU - Jonelle L. Walsh
PY - 2026
DA - 2026/11/03
PB - arXiv
DO - 10.48550/arxiv.2611.05486
UR - https://arxiv.org/abs/2611.05486
AB - We combine JWST NIRSpec and Keck KCWI observations to construct a contiguous 2D map of M87's stellar kinematics spanning three decades in projected radius, from ∼10 pc to ∼10 kpc, and measure the mass of its central supermassive black hole. The innermost stellar kinematic measurements probe projected radii as small as ∼3% of the black hole's sphere of influence radius, or approximately 30,000 Schwarzschild radii. The NIRSpec spectra within R < 0.45'' are contaminated by quasiperiodic "wiggle" artifacts. We develop hyphen, which uses detector spectral traces to predict how the wiggle frequency varies with wavelength, then fits and subtracts the wiggle pattern from each spectrum in each exposure before combining the data. The cleaned spectra reveal a pronounced central rise in stellar velocity dispersion and h_4. Triaxial Schwarzschild stellar orbit modeling with the TriOS code, fitting ∼5,000 kinematic constraints across 618 spatial bins from JWST and Keck, yields a black hole mass of M_BH=(5.38 ± 0.13± 0.22)×10^9 M_⊙. This result is consistent with our prior KCWI-only determination but with the statistical uncertainty reduced by a factor of 2-3, now subdominant to the systematic uncertainty in the distance (D) to M87. Our inferred mass-to-distance ratio is θ_g=GM_BH/(c^2 D) = 3.16 ± 0.08 μas, whose 90% credible interval overlaps with that obtained from the multi-epoch Event Horizon Telescope (EHT) analysis, providing a robust and independent prior for future EHT studies.
ER -