2024/07/26 by Motoki Kino, Hyunwook Ro, Kino, Motoki +11 · 1 citation
Physics and Astronomy · #Astrophysics of Galaxies (astro-ph.GA) #FOS: Physical sciences #Gamma-ray bursts and supernovae #High Energy Astrophysical Phenomena (astro-ph.HE) #Pulsars and Gravitational Waves Research #Solar and Space Plasma Dynamics
paper · pdf · doi:10.48550/arxiv.2407.18444
openalex publication_date 2024/07/26 · openalex created_date 2024/09/12 · openalex updated_date 2026/07/28
We study magnetic field strengths along the jet in NGC~315. First, we estimated the angular velocity of rotation in the jet magnetosphere by comparing the measured velocity profile of NGC~315 with the magneto-hydrodynamic jet model of proposed by Tomimatsu and Takahashi. Similar to the case of M87, we find that the model can reproduce the logarithmic feature of the velocity profile and suggest a slowly rotating black hole magnetosphere for NGC~315. By substituting the estimated ΩF into the jet power predicted by the Blandford-Znajek mechanism, we estimate the magnetic field strength near the event horizon of the central black hole as 5× 103~\rm G\lesssim BH\lesssim 2× 104~\rm G. We then estimate magnetic-field strengths along the jet by comparing the spectral index distribution obtained from VLBI observations with a synchrotron-emitting jet model. Then we constrain the magnetic field strength at a de-projected distance z from the black hole to be in the range 0.06~\rm G\lesssim B(z)\lesssim 0.9~\rm G for 5.2 × 103~rg\lesssim z \lesssim 4.9 × 104~rg, where rg represents the gravitational radius. By combining the obtained field strengths at the event horizon and the downstream section of the jet, we find that the accretion flow at the jet base is consistent with a magnetically arrested disk (MAD). We discuss a comparison of the jet power and the magnetic flux anchored to the event horizon in NGC~315 and M87.