Zooming towards the Event Horizon - mm-VLBI today and tomorrow

Abstract

Global VLBI imaging at millimeter and sub-millimeter wavelength overcomes the opacity barrier of synchrotron self-absorption in AGN and opens the direct view into sub-pc scale regions not accessible before. Since AGN variability is more pronounced at short millimeter wavelength, mm-VLBI can reveal structural changes in very early stages after outbursts. When combined with observations at longer wavelength, global 3 mm and 1 mm VLBI adds very detailed information on the source structure. This helps to determine fundamental physical properties at the jet base, and in the vicinity of super-massive black holes at the center of AGN. Here we present new results from multi-frequency mm-VLBI imaging of OJ 287 during a major outburst. We also report on a successful 1.3 mm VLBI experiment with the APEX telescope in Chile. This observation sets a new world record in angular resolution. It also opens the path towards future mm-VLBI with ALMA, which aims at the mapping of the black hole event horizon in nearby galaxies, and the study of the roots of jets in AGN.

Quantum gravity effects around Sagittarius A*

“…For instance, quantum gravitational fluctuations of the metric could disrupt the accretion flow in the near-horizon atmosphere region, distort or suppress the photon ring [16], or distort the edge of the shadow [17]. For Sagittarius A* the photon ring has a size of 53 µas and one might even consider the possibility of relating quantum gravity effects to the preliminary apparent discrepancy between the presently observed size and the expected photon ring size of the hole [18].…”

Magnetic Dissipation in Relativistic Jets

“…Studying in detail the structure in these stationary components for a direct comparison with our simulations requires however, resolving the jet structure across the jet width. This can be achieved through mm-VLBI observations by GMVA (Global Millimeter VLBI Array) [36], the Event Horizon Telescope and the Black Hole Cam project [37,38], and the space VLBI mission RadioAstron [39].…”

VLBI at APEX: First fringes

“…For some time intervals the coherence time was surprisingly large ∼ 30 s (see Fig. 6), though was typically ∼ 5 s. First scientific results will be published in [3] and [4].…”