ALMA CO(2-1) Gas Dynamics in NGC 315: A Multi-Method Benchmark for Supermassive Black Hole Mass Measurement
Abstract
We present ALMA Cycle~7 \cotwo\ observations of the circumnuclear disk in NGC~315 at an angular resolution of 0farcs230×0farcs175, improving on past measurements and resolving the sphere of influence (SOI) of the supermassive black hole (SMBH), whose mass has previously been estimated of MBH= (2.08+0.33−0.15) × 109~M⊙ The high spatial resolution and sensitivity enable robust full-cube forward modeling of the molecular gas kinematics and a direct comparison of multiple independent gas-based dynamical modeling techniques. We apply standard Bayesian codes using both MCMC and nested sampling approaches, as well as a frequentist code to the same dataset, exploring systematic uncertainties associated with the stellar mass distribution, gas surface-brightness parameterization, and disk geometry. All methods yield consistent black hole masses, indicating that the inferred MBH is not strongly method-dependent. Combining the ensemble of independent molecular-gas-based models, we derive an ensemble median black hole mass of MBH/109 M⊙ = 2.02+0.04−0.05(stat)+0.05−0.04(sys), where the comparable contributions to the full error budget arise from modeling systematics rather than formal fitting uncertainties. Our MBH is consistent with the empirical MBH--σ⋆ and MBH--Lbulge scaling relations, and lies 32\% below an independent stellar-dynamical measurement, a discrepancy we discuss in the context of systematic differences between gas- and stellar-based methods. NGC~315 serves as a benchmark for quantifying molecular gas-dynamical MBH systematic uncertainties and for future cross-comparisons of gaseous and stellar dynamical approaches.
Related
- Atacama Large Millimeter/submillimeter Array (ALMA) ¹² CO(2–1) Gas Dynamics in NGC 315: A Multimethod Benchmark for Supermassive Black Hole Mass Measurement
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- Stellar Collisions from Self-consistent Stellar Dynamics Around Growing Supermassive black Holes
- Heavy Seeds and the Multi-scale Fueling of Early Supermassive Black Holes and Little Red Dots
- Supermassive black hole binaries in the multi-messenger context of ground and spaceborne VLBI
BibTeX
@misc{nguyen2026alma,
title = {{ALMA CO(2-1) Gas Dynamics in NGC 315: A Multi-Method Benchmark for Supermassive Black Hole Mass Measurement}},
author = {Dieu D. Nguyen and Benjamin D. Boizelle and Hai N. Ngo and Elena Gallo and Tuan N. Le and Sabine Thater and Tien H. T. Ho and Tinh Q. T. Le and Que T. Le and Sam Norcross and Xueyi Li and Huy G. Tong and Nghi K. N. Le and Huy M. B. Tran},
howpublished = {arXiv},
year = {2026},
month = aug,
doi = {10.48550/arxiv.2608.31015},
eprint = {2608.31015},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2608.31015},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - ALMA CO(2-1) Gas Dynamics in NGC 315: A Multi-Method Benchmark for Supermassive Black Hole Mass Measurement
AU - Dieu D. Nguyen
AU - Benjamin D. Boizelle
AU - Hai N. Ngo
AU - Elena Gallo
AU - Tuan N. Le
AU - Sabine Thater
AU - Tien H. T. Ho
AU - Tinh Q. T. Le
AU - Que T. Le
AU - Sam Norcross
AU - Xueyi Li
AU - Huy G. Tong
AU - Nghi K. N. Le
AU - Huy M. B. Tran
PY - 2026
DA - 2026/08/31
PB - arXiv
DO - 10.48550/arxiv.2608.31015
UR - https://arxiv.org/abs/2608.31015
AB - We present ALMA Cycle~7 \cotwo\ observations of the circumnuclear disk in NGC~315 at an angular resolution of 0farcs230×0farcs175, improving on past measurements and resolving the sphere of influence (SOI) of the supermassive black hole (SMBH), whose mass has previously been estimated of M_BH= (2.08^+0.33_−0.15) × 10^9~M_⊙ The high spatial resolution and sensitivity enable robust full-cube forward modeling of the molecular gas kinematics and a direct comparison of multiple independent gas-based dynamical modeling techniques. We apply standard Bayesian codes using both MCMC and nested sampling approaches, as well as a frequentist code to the same dataset, exploring systematic uncertainties associated with the stellar mass distribution, gas surface-brightness parameterization, and disk geometry. All methods yield consistent black hole masses, indicating that the inferred M_BH is not strongly method-dependent. Combining the ensemble of independent molecular-gas-based models, we derive an ensemble median black hole mass of M_BH/10^9 M_⊙ = 2.02^+0.04_−0.05(stat)^+0.05_−0.04(sys), where the comparable contributions to the full error budget arise from modeling systematics rather than formal fitting uncertainties. Our M_BH is consistent with the empirical M_BH--σ_⋆ and M_BH--L_bulge scaling relations, and lies 32\% below an independent stellar-dynamical measurement, a discrepancy we discuss in the context of systematic differences between gas- and stellar-based methods. NGC~315 serves as a benchmark for quantifying molecular gas-dynamical M_BH systematic uncertainties and for future cross-comparisons of gaseous and stellar dynamical approaches.
ER -