Poster Presentation

Limb brightening of black hole jets as a consequence of angle-dependent energy flux: Centaurus A

Author(s): Dyon Su(Institute of Astronomy and Astrophysics, Academia Sinica, Taipei 10617, Taiwan), Kouichi Hirotani(Institute of Astronomy and Astrophysics, Academia Sinica, Taipei 10617, Taiwan), Hsien Shang(Institute of Astronomy and Astrophysics, Academia Sinica, Taipei 10617, Taiwan), Ruben Krasnopolsky(Institute of Astronomy and Astrophysics, Academia Sinica, Taipei 10617, Taiwan)

Presenter: Dyon Su (Academia Sinica Institute ofAstronomy and Astrophysics)

Limb brightening is a feature observed across various blackhole jets(3C84, M87, Cygnus A), where the jet possesses an edge brightened transverse intensity profile. Jets can be launched via the electromagnetic extraction of a black hole's rotational energy, which will produce an energy outflow with its maximum magnitude at the equator and declining to zero towards the poles. Such angular dependence of the energy flux may be the cause of limb brightening. We model jets produced by this energy flux, parameterizing the jet geometry, conversion of electromagnetic energy into the kinetic energy of particles, and the emissions of the jet from synchrotron radiation. By integrating the radiative transfer equation along the line of sight we can obtain a synthetic VLBI map of the jet. Recent EHT observations of Centaurus A provides clear VLBI imaging of the innermost regions of its jet, making it an optimal subject for the verification of our model. We constrain the model parameters according to available observational data of Centaurus A, and produce synthetic observations of the VLBI map and Spectral energy distribution(SED) to correspond to real observations. Using ALMA’s band 1 to perform multi-frequency surveys from 35 to 50GHz will provide information about the SED useful for the inference of our synthetic results, allowing us to study the properties of the jet emission region(e.g., matter content, magnetic field strength, plasma density). We find that the model indeed produces a limb brightened jet, providing evidence that limb brightening may indeed be a consequence of the angle dependence of the energy flux.