Probing Active Galactic Nuclei with Radio Techniques

Active galactic nuclei (AGNs) derive their power from accretion onto supermassive black holes located in the centers of galaxies.  Many phenomena connected with active galaxies derive from physical processes associated with the central engine’s accretion flow, which, depending on the mass accretion rate and possibly other parameters, such as black hole spin, generate outflows and relativistic jets.  The energy output from the nucleus, whether it be radiative or kinetic, may have a profound influence on the evolution of the host galaxy and its larger scale environment.
Many of the processes associated with AGNs emit broad-band spectra across the electromagnetic spectrum.  Observations at radio wavelengths, in particular, provide an especially valuable probe of a variety of physical processes, including the radiation mechanisms of radiatively inefficient accretion flows, synchrotron radiation arising from jets, thermal emission from ionized gas, and polarization signal from magnetized plasma.  Radio interferometric techniques also enable the highest possible angular resolution available to any waveband, providing a unique tool to image details close to the black hole.  On the scales of the host galaxy, radio continuum emission can constrain its star formation rate, and line emission diagnoses the content of neutral and molecular hydrogen gas, as well as their large-scale spatial distribution and velocity field.

The Chinese astronomical community currently operates a 13.7m millimeter-wave dish at Delingha, the 65m Tianma telescope near Shanghai, the Shanghai 25m and Urumqi 25m telescopes.  A number of researchers actively participate in the international VLBI network, and Shanghai Astronomical Observatory has special access to the VLBA through a memorandum signed with NRAO. Meanwhile, the 500m FAST telescope in Guizhou is under construction, and Xinjiang Astronomical Observatory is planning a 110m telescope.  All of these facilities are relevant to AGN science.

The purpose of this meeting is to gather researchers  to exchange new results and views, especially with expertise in utilizing radio techniques to probe AGNs. This is both an opportunity for mainland Chinese astronomers to get to know each other and form collaborations, and for them to interact with foreign experts, especially from neighboring countries/region such as Japan, Taiwan, South Korea, and India, all of whom have a substantial community of radio astronomers whose research focuses on AGNs.

Topics covered in the meeting include:

  • Observations and theory of AGN jets on all scales
  • AGN jets and feedback
  • Polarization measurements and inferences of magnetic fields near AGNs
  • The interstellar medium content of AGN host galaxies, and scattering in our Galaxy
  • Binary supermassive black holes