TANAMI: Tracking active galactic nuclei with austral millarsecond interferometry
Ojha, R and Kadler, M and Bock, M and Booth, R and Dutka, MS and Edwards, PG and Fey, AL and Fuhrmann, L and Gaume, RA and Hase, H and Horiuchi, S and Jauncey, DL and Johnson, KJ and Katz, U and Lister, M and Lovell, JEJ and Mueller, C and Plotz, C and Quick, JFH and Ros, E and Taylor, GB and Thompson, DJ and Tingay, SJ and Tosti, G and Tzioumis, AK and Wilms, J and Zensus, JA, TANAMI: Tracking active galactic nuclei with austral millarsecond interferometry, Astronomy and Astrophysics, 519, (Sept) EJ ISSN 0004-6361 (2010) [Refereed Article]
Context. A number of theoretical models vie to explain the ã-ray emission from active galactic nuclei (AGN). This was a key discovery of
EGRET. With its broader energy coverage, higher resolution, wider field of view and greater sensitivity, the Large Area Telescope (LAT) of
the Fermi Gamma-ray Space Telescope is dramatically increasing our knowledge of AGN ã-ray emission. However, discriminating between
competing theoretical models requires quasi-simultaneous observations across the electromagnetic spectrum. By resolving the powerful parsecscale
relativistic outflows in extragalactic jets and thereby allowing us to measure critical physical properties, Very Long Baseline Interferometry
observations are crucial to understanding the physics of extragalactic ã-ray objects.
Aims. We introduce the TANAMI program (Tracking Active Galactic Nuclei with Austral Milliarcsecond Interferometry) which is monitoring an
initial sample of 43 extragalactic jets located south of −30 degrees declination at 8.4GHz and 22GHz since 2007. All aspects of the program are
discussed. First epoch results at 8.4GHz are presented along with physical parameters derived therefrom.
Methods. These observations were made during 2007/2008 using the telescopes of the Australian Long Baseline Array in conjunction with
Hartebeesthoek in South Africa. These data were correlated at the Swinburne University correlator.
Results. We present first epoch images for 43 sources, some observed for the first time at milliarcsecond resolution. Parameters of these images
as well as physical parameters derived from them are also presented and discussed. These and subsequent images from the TANAMI survey are
available at http://pulsar.sternwarte.uni-erlangen.de/tanami/.
Conclusions. We obtain reliable, high dynamic range images of the southern hemisphere AGN. All the quasars and BL Lac objects in the sample
have a single-sided radio morphology. Galaxies are either double-sided, single-sided or irregular. About 28% of the TANAMI sample has been
detected by LAT during its first three months of operations. Initial analysis suggests that when galaxies are excluded, sources detected by LAT
have larger opening angles than those not detected by LAT. Brightness temperatures of LAT detections and non-detections seem to have similar
distributions. The redshift distributions of the TANAMI sample and sub-samples are similar to those seen for the bright ã-ray AGN seen by LAT
and EGRET but none of the sources with a redshift above 1.8 have been detected by LAT
galaxies: active – galaxies: jets – galaxies: nuclei – gamma rays: observations – quasars: general