TANAMI

TANAMI. The Tracking Active Galactic Nuclei with Austral Milliarcsecond Interferometry (TANAMI) program is a long-term, multi-epoch very-long-baseline interferometry (VLBI) monitoring survey of extragalactic jetted active galactic nuclei (AGN) in the Southern Hemisphere. Initiated in 2007, it uniquely combines observations from a network of radio telescopes across the Southern Hemisphere, including the Australian Long Baseline Array and collaborating antennas in South Africa, Chile, and Antarctica. The program focuses on the parsec-scale jets of blazars and other radio galaxies, providing crucial data to understand relativistic jet formation and evolution.

Overview

TANAMI was established to address the historical scarcity of high-resolution radio monitoring of southern-sky AGN, a region rich with important sources like Centaurus A and PKS 2155-304. The survey leverages the technique of very-long-baseline interferometry to achieve milliarcsecond resolution, effectively creating a virtual telescope with a diameter spanning continents. Key facilities in the array include the Australia Telescope Compact Array, the Parkes Observatory, and the Hartebeesthoek Radio Astronomy Observatory. By regularly observing a sample of over 80 sources, TANAMI provides a dynamic view of jet kinematics and structural changes, complementing northern hemisphere surveys like the MOJAVE program and observations by the Very Long Baseline Array.

Scientific objectives and design

The primary scientific goal of TANAMI is to study the physics of relativistic outflows from supermassive black holes, particularly those powering gamma-ray bright blazars detected by the Fermi Gamma-ray Space Telescope. The program design involves dual-frequency observations at 8.4 GHz and 22 GHz to study spectral properties and perform high-precision astrometry. A core objective is to correlate changes in the parsec-scale jet structure with multiwavelength data from instruments like the Swift Gamma-Ray Burst Mission and the Neil Gehrels Swift Observatory to probe emission mechanisms. The survey also aims to measure proper motion and apparent superluminal motion in jets to constrain Lorentz factor and viewing angles, testing models from the Blandford–Znajek process.

Key findings and results

TANAMI has produced a wealth of results, including the first detailed kinematic studies of jets in famous southern sources such as PKS 0521-365 and PKS 0637-752. The program measured superluminal motions in the jet of Centaurus A, providing direct evidence of relativistic outflow from the nearest active galaxy. TANAMI data have been critical for identifying the radio counterparts of Fermi-LAT detected blazars, aiding in source identification and localization. Research using the survey has investigated jet bending and precession in objects like PKS 2123-463, and has constrained the magnetic field structure and particle acceleration sites within jets through polarization studies. Findings have been published in numerous papers in journals like Astronomy & Astrophysics and The Astrophysical Journal.

Collaborating institutions

The TANAMI collaboration is an international consortium led by institutions in Germany and Australia. Principal partners include the Max Planck Institute for Radio Astronomy in Bonn, the University of Erlangen–Nuremberg, and the CSIRO Australia Telescope National Facility. Essential telescope contributions come from the South African Radio Astronomy Observatory, the Hartebeesthoek Radio Astronomy Observatory, and the University of Tasmania's telescopes at Ceduna and Hobart. The program also involves researchers from the Jet Propulsion Laboratory, the University of Würzburg, and the Italian National Institute for Astrophysics, with data correlation performed at the Bonn Correlator.

Related projects and future work

TANAMI is intrinsically linked to broader multiwavelength and multimessenger astrophysics efforts. Its data are used in conjunction with high-energy observations from the H.E.S.S. telescope array and the upcoming Cherenkov Telescope Array. The survey methodology paves the way for next-generation instruments like the Square Kilometre Array and the Event Horizon Telescope, which will study black hole jets at even higher resolutions. Future work includes expanding polarization monitoring and integrating data from optical surveys like the Large Synoptic Survey Telescope. The long-term kinematic database from TANAMI remains a vital resource for understanding jet duty cycles and preparing for observations with the MeerKAT array and the full SKA Observatory.

Category:Astronomical surveys Category:Radio astronomy Category:Very-long-baseline interferometry