An Accretion-Jet Model for M87: Interpreting the Spectral Energy Distribution and Faraday Rotation Measure

Abstract

M87 is arguably the best supermassive black hole (BH) to explore the jet and/or accretion physics due to its proximity and fruitful high-resolution multi-waveband observations. We model the multiwavelength spectral energy distribution (SED) of M87 core that observed at a scale of 0.4 arcsec (∼ 10 5 R g , R g is gravitational radius) as recently presented by Prieto et al. Similar to Sgr A*, we find that the millimeter bump as observed by Atacama Large Millimeter/submillimeter Array (ALMA) can be modeled by the synchrotron emission of the thermal electrons in advection dominated accretion flow (ADAF), while the low-frequency radio emission and X-ray emission may dominantly come from the jet. The millimeter radiation from ADAF dominantly come from the region within 10R g , which is roughly consistent with the recent very long baseline interferometry observations at 230 GHz. We further calculate the Faraday rotation measure (RM) from both ADAF and jet models, and find that the RM predicted from the ADAF is roughly consistent with the measured value while the RM predicted from the jet is much higher if jet velocity close to the BH is low or moderate (e.g., v jet 0.6 c). With the constraints from the SED modeling and RM, we find that the accretion rate close to the BH horizon isBondi accretion rate), where the electron density profile, n e ∝ r ∼−1 , in the accretion flow is consistent with that determined from X-ray observation inside the Bondi radius and recent numerical simulations.

Faraday rotation in GRMHD simulations of the jet launching zone of M87

“…parameters. The possibility that the RM originates in the jet rather than the extended accretion flow is natural given the low inclination of M87 jet, and was considered previously (Kuo et al 2014;Li et al 2016;Feng et al 2016). We have demonstrated this with self-consistent MHD disk+jet models that can match the radio observations.…”

Constraint on the black hole spin of M87 from the accretion-jet model

“…The millimeter bump of M87 as observed in the highresolution quasi-simultaneous multi-waveband SED at a scale of 0.4 arcsec most possibly come from the innermost region of the ADAF close to the BH horizon (Feng et al 2016;Li et al 2016). The radio and X-ray emission should be dominated by the jet.…”

“…We adopt a coupled ADAF-jet model surrounding a Kerr BH to constrain the BH spin in M87, where both the multibands emission and jet power are considered. We simply introduce the accretion and jet model as below, and more details can be found in Wu et al (2013), Feng et al (2016) and references therein.…”

A New Chapter in Hard X-rays of the M87 AGN

“…It is interesting that in another nearby radio galaxy, 3C 84, no cut-off in the power-law spectrum was found, and the hard X-ray emission is also more consistent with a jet origin [17]. The jet origin of the M87 core is also supported by Faraday rotation measure observations [18,19]. A more detailed discussion can be found in Wong et al [13].…”