The Parkes quarter-Jansky flat-spectrum sample 2. New optical spectra and redshift measurements

The N-galaxy 3C 99, a Compact Steep-spectrum Source showing a triple asymmetric structure, has been observed with several arrays of radio telescopes at sub-arcsecond resolution. New images from MERLIN, European VLBI Network and the Very Long Baseline Array show that the source components detected in the central region of 3C 99 have steep spectral indices, making it difficult to determine which of them is the core. The asymmetric radio structure of 3C 99 is explained using the Scheuer-Baldwin continuous streaming model with a rather large difference in the interstellar medium density on the two sides of the central region. The age of 3C 99 has been estimated; the source is found younger than 106 years.