The central parsecs of M87: jet emission and an elusive accretion disc

Abstract

We present the first simultaneous spectral energy distribution (SED) of M87 core at a scale of 0.4 arcsec (∼ 32 pc) across the electromagnetic spectrum. Two separate, quiescent, and active states are sampled that are characterized by a similar featureless SED of power-law form, and that are thus remarkably different from that of a canonical active galactic nuclei (AGN) or a radiatively inefficient accretion source. We show that the emission from a jet gives an excellent representation of the core of M87 core covering ten orders of magnitude in frequency for both the active and the quiescent phases. The inferred total jet power is, however, one to two orders of magnitude lower than the jet mechanical power reported in the literature. The maximum luminosity of a thin accretion disc allowed by the data yields an accretion rate of < 6 × 10 −5 M yr −1 , assuming 10% efficiency. This power suffices to explain M87 radiative luminosity at the jet-frame, it is however two to three order of magnitude below that required to account for the jet's kinetic power. The simplest explanation is variability, which requires the core power of M87 to have been two to three orders of magnitude higher in the last 200 yr. Alternatively, an extra source of power may derive from black hole spin. Based on the strict upper limit on the accretion rate, such spin power extraction requires an efficiency an order of magnitude higher than predicted from magnetohydrodynamic simulations, currently in the few hundred per cent range.

Far-Uv Emission Properties of Fr1 Radio Galaxies

“…This same broadband SED was also used by Broderick et al (2015) to place similar constraints on the accretion rate and on the presence of an event horizon. Prieto et al (2016) also derive a similarly low accretion rate from the previous HST imaging data on the Hα emission line in the ionized gas disk discovered by Ford et al (1994). The absence of significant Faraday rotation for the M 87 nuclear source at sub-mm wavelengths is also consistent with a very low accretion rate (Kuo et al 2014).…”

“…Detailed fitting of the spectral energy distribution (SED) within ∼ 30 pc of the nucleus of M87 by Prieto et al (2016) finds an SED dominated by jet emission throughout the electromagnetic spectrum excepting a small contribution from a cool accretion disk longward of 1µm. This corroborates earlier work by Perlman et al (2001Perlman et al ( , 2007.…”

The Global Jet Structure of the Archetypical Quasar 3C 273

“…For M87 whose bolometric luminosity is ∼10 −6 times smaller than the Eddington luminosity (L edd ) [21], Asada and Nakamura [2] suggest that the jet may be confined by a radiatively inefficient hot accretion flow (RIAF) with a geometrically-thick quasi-spherical shape (e.g., [22]). Indeed, recent 86 GHz observations of M87 have shown that the jet pressure at the 86 GHz core is comparable to the RIAF pressure, indicating that the pressure support from the hot accretion flow may be capable of shaping the M87 jet [5].…”

Powerful outflows in the central parsecs of the low-luminosity active galactic nucleus NGC 1386

“…Schartmann et al 2014). Low Eddington sources are often powerful radio sources, best prototype is M87 (Prieto et al 2016, and references therein), and thus a jet in NGC 1386 is a plausible cause of the outflowing shells. NGC 1386 shows extended radio emission at each side of the nucleus along the N-S direction, the Southern emission being better defined and detached-from-the-core while the northern one appears as a protuberance.…”