2025/05/15 by Dieu D. Nguyen, Nguyen, Dieu D., Hai N. Ngo +27 · 4 citations
Physics and Astronomy · #Adaptive optics and wavefront sensing #Astronomy and Astrophysical Research #Astrophysical Phenomena and Observations #Astrophysics of Galaxies (astro-ph.GA) #FOS: Physical sciences
paper · pdf · doi:10.48550/arxiv.2505.09941
openalex publication_date 2025/05/15 · openalex created_date 2025/10/15 · openalex updated_date 2026/07/28
We present accurate mass measurements of the central supermassive black hole (SMBH) in NGC 4736 (M 94). We used the ``gold-standard" stellar absorption features (CO band heads) at ∼2.3 \rm μm, as opposed to gas emission lines, to trace the dynamics in the nuclear region, easily resolving the SMBH's sphere of influence. The analysis uses observations made with the integral field unit of the Near-Infrared Spectrograph (NIRSpec) on the \it James Webb Space Telescope and a surface brightness profile derived from \it Hubble Space Telescope archival images. We used Jeans anisotropic models within a Bayesian framework, and comprehensive Markov chain Monte Carlo optimization, to determine the best-fit black hole mass, orbital anisotropy, mass-to-light ratio, and nucleus kinematical inclination. We obtained a SMBH mass M\rm BH=(1.60±0.16)×107 M_\odot (1σ random error), which is consistent with the M\rm BH-σ and M\rm BH-M_⋆ relations. This is the first dynamical measurement of a M\rm BH in NGC 4736 based on the stellar kinematics observed with NIRSpec. We thus settle a longstanding inconsistency between estimates based on nuclear emission-line tracers and the M\rm BH-σ relation. Our analysis shows that NIRSpec can detect SMBHs with M\rm BH,min≈ 5×106 M_\odot in galaxies within 5 Mpc and σ≈100 km s-1