The Riddle of Infrared Faint Radio Sources

faint_sources.jpgInfrared-faint radio sources (IFRS) form a new class of galaxies characterized by radio flux densities ~ milli-Janskys, with faint or absent infrared counterparts. It has been suggested that these objects are radio-loud active galactic nuclei (AGNs), at high redshift, although very young starburst galaxies at lower redshift cannot be ruled out. Herzog et al report the results of a 1.4 GHz VLBA survey of 57 IFRS at 10mas resolution and a sensitivity of ~ 60 micro-Jansky/beam rms. They detect compact cores in 35 of the 57 galaxies they surveyed. These results answer conclusively that IFRS are indeed radio AGN at substantial redshifts, and provide a sample of lower luminosity radio AGN to study in the distant Universe, possibly the youngest radio jet sources.

View Paper: Active galactic nuclei cores in infrared-faint radio sources: Very long baseline interferometry observations using the Very Long Baseline Array, A. Herzog (Bochum, Macquarie, CSIRO), E. Middelberg (Bochum), R.P. Norris (CSIRO), L.R. Spitler (Macquarie, AAO), A.T. Deller (ASTRON), J.D. Collier (Western Sydney, CSIRO), and Q.A. Parker (Macquarie, AAO), 2015 A&A, 578, A67 (published online 5 June 2015).

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