A Jet Source of Event Horizon Telescope Correlated Flux in M87

TL;DR

This study combines multi-frequency observations to model the base of M87's jet, revealing a tubular structure with specific size constraints and no need for an invisible spine, influenced mainly by flux density and black hole spin.

Contribution

It introduces a tubular jet model constrained by recent high-resolution VLBI and EHT data, providing new insights into jet structure and power without requiring a hidden spine.

Findings

Jet dimensions depend strongly on 86 GHz flux and black hole spin.

The jet power is consistent with the entire M87 jet power budget (~10^44 ergs/sec).

Spectral shape constrains the jet's transverse size to 12-21 microarcseconds.

Abstract

Event Horizon Telescope (EHT) observations at 230 GHz are combined with Very Long Baseline Interferometry (VLBI) observations at 86 GHz and high resolution Hubble Space Telescope optical observations in order to constrain the broadband spectrum of the emission from the base of the jet in M87. The recent VLBI observations of Hada et al provide much stricter limits on the 86 GHz luminosity and component acceleration in the jet base than was available to previous modelers. They reveal an almost hollow jet on sub-mas scales. Thus, tubular models of the jet base emanating from the innermost accretion disk are considered within the region responsible for the EHT correlated flux. There is substantial synchrotron self absorbed opacity at 86 GHz. A parametric analysis indicates that the jet dimensions and power depend strongly on the 86 GHz flux density and the black hole spin, but weakly on other parameters such as jet speed, 230 GHz flux density and optical flux. The entire power budget of the M87 jet, $\lesssim 10^{44}\rm{ergs/sec}$, can be accommodated by the tubular jet. No invisible, powerful spine is required. Even though this analysis never employs the resolution of the EHT, the spectral shape implies a dimension transverse to the jet direction of 12-21 $\mu \rm{as}$ ($\sim$24-27$\, \mu \rm{as}$) for $0.99 > a/M > 0.95$ ($a/M\sim 0.7 $), where $M$ is the mass and $a$ is the angular momentum per unit mass of the central black hole.