Conference

Stellar dynamical measurements of black hole masses have become the de facto standard method. I will give a brief review of how this measurement method works, along with arguments for its overall reliability and caveats. Then I will turn my attention to the case of the black hole in M87. The black hole is undeniably large ? billions of solar masses ? but has a stellar dynamical mass measurement in disagreement with gas dynamical mass measurements at about the 2 sigma level. I will discuss potential systematic uncertainties in both measurements and avenues to reconciling the discrepancy.

We examine the structure and dynamics of the M87 jet based on both multi-frequency observations and MHD jet theories. Millimeter (mm) VLBI cores are considered as innermost jet emissions. Resolved parabolic streamline may suggest that the jet collimation maintains in five orders of magnitude in the distance starting from the vicinity of the supermassive black hole (SMBH), less than 10 r_s where the VLBI core at 1.3 mm is located. Observed sub-to-superluminal motions may indicate an MHD acceleration takes place from non-relativistic to relativistic regimes. We discuss that the M87 jet consists hybrid spine/sheath structure from either a spinning super massive black hole and or radiatively inefficient accretion flow. Future sub-mm VLBI imaging play an essential role in resolving the origin (i.e., formation mechanism) of the M87 jet as well as constraining the SMBH spin parameter. Based on our understanding of M87, we also discuss about the key science in other AGN jets with sub-mm VLBI experiments.

Both the continuum-fitting and Fe-line methods of measuring black hole spin will be discussed and compared, with attention to sources of systematic error. Both methods rely on estimating the inner radius of the black hole's accretion disk and identifying it with the radius of the ISCO. The Fe-line method is extremely important because of its dominant role in measuring the spins of supermassive black holes, which is problematic for the continuum-fitting method. Meantime, both methods are applicable to stellar-mass black holes, and we will discuss current efforts to cross-check the spins of individual black holes. Finally, a comprehensive summary of spin results for both stellar-mass and supermassive black holes will be presented.

There are good reasons to believe that relativistic jets of AGN are powered by rotating black holes via the Blandford-Znajek mechanism. Although the original mathematical solution, which demonstrated the possibility of such energy extraction, was found 37 years ago, its physical nature still remains a subject of debate. I will give a brief review of some recent developments in this area with focus on the roles played by the EH and the Ergoregion in the Blandford-Znajek mechanism.

Christiann Brinkerink, Radboud University Nijmegen

What closure phase measurements at 86 GHz can tell us about Sagittarius A*

Thomas Bronzwaer, Radboud University Nijmegen

Predicted VLBI Observables for SMBH's Based on GRMHD Simulations

Alejandro Cardenas-Avendano, Universidad Nacional de Colombia

Probing the Regular Nature of the Spacetime by Measuring the Shadow of a Black Hole

Andrew Chael, Harvard-Smithsonian Center for Astrophysics

Maximum Entropy Polarimetric Imaging

Laura Chajet, York University

AGNs: Line Width Distribution of MHD Disc Winds

Pierre Christian, Harvard Smithsonian Center for Astrophysics

complimentary observations to the EHT for understanding strong gravity

Riley Connors, University of Amsterdam

Jet Physics Across the Black Hole Mass Scale: Sgr A* and A0620-00

Roger Deane, University of Cape Town

Extreme Interferometry with MeqTrees: advanced interferometric simulation and analysis

Salome Dibi, Radboud University Nijmegen

The emission mechanisms from Sgr A*’s inner gravitational radii

Ciriaco Goddi, Radboud University Nijmegen

mm-VLBI in Europe

Svetlana Jorstad, Boston University

Linear Polarization in the Jet of the Quasar 3C279 at near-EHT resolution 

Motoki Kino, Korea Astronomy & Space Science Institute

Magnetic field strength at the jet base of M87

Michael Landry, LIGO Hanford Observatory

Advanced LIGO status

Alan Marscher, Boston University

Linear Polarization at 1 mm as a Probe of the "Core" of Blazar Jets

Gisela Ortiz, Universidad Nacional Autónoma de México

Testing a 3 mm VLBI system at the Large Millimeter Telescope: Observations of Sgr A*.

Percy Paul, University of Saskatchewan

Gravity Waves in RS models

Hung-Pi Pu, Academia Sinica Institute of Astronomy & Astrophysics

Semi-analytical GRMHD jet model and its Synchrotron Image on Horizon Scale

Angelo Ricarte, Yale University

Probing Strong Gravity and Accretion Physics with the Event Horizon Telescope

Frank Roelofs, Radboud University Nijmegen

imaging Sgr A* through time-variability

Eduard Ros, Max Planck Institute for Radio Astronomy

Jet formation region of NGC 1052 with mm-VLBI

Fumie Tazaki, National Astronomical Observatory of Japan

super-resolution images of M87 with compressed sensing

The radio community pioneered the use of closure phases to allow interferometric imaging even when fringe phases are compromised by atmospheric turbulence or unstable reference clocks. Eventually, better receivers and observing methods allowed phase referencing to provide direct measures of complex visibilities and eased the uncertainties using Fourier inversions required for imaging. At the same time, optical and infrared (O/IR) interferometers have been developed recently that can combine up to 6 telescopes simultaneously, at which point the inadequacies of classic imaging methods such as CLEAN were apparent. Here I report on dramatic progress within the O/IR interferometry to develop new image reconstruction techniques taking advantage of advances in ``compressed sensing'' theory and new approaches afforded by modern computing. Because the Event Horizon Telescope must rely on closure phases instead of direct Fourier phases, the new algorithms from the O/IR could be essential to extracting the most information from EHT observations and we demonstrate promising results using simulated EHT data.

The Event Horizon Telescope has measured compact emission in Sgr A* and M87 at resolutions comparable to their event horizons. Polarimetry with the EHT enables a powerful extension of this work, mapping magnetic field structures via the highly polarized synchrotron emission that is thought to dominate the compact emission. Sgr A* provides an especially attractive target for linear polarization studies with the EHT because it is unpolarized at the longer wavelengths where facility instruments are available. I will report on polarimetric results from our 2013 campaign, which demonstrate a sharp increase in the linear polarization fraction and variability of Sgr A* with increasing baseline. These data allow rich model-independent inferences about the polarization images and morphology and reveal that polarization is a sensitive probe of intrinsic variability.

I summarize several physical processes that can produce efficient particle acceleration in radiatively inefficient accretion flows. I then describe the implications for non-thermal emission and EHT observations of Sgr A*.