Compact steep-spectrum and peaked-spectrum radio sources

Compact steep-spectrum (CSS) and peaked-spectrum (PS) radio sources are compact, powerful sources. The multi-frequency observational properties current theories reviewed with emphasis on developments since the earlier review of O’Dea (PASP 110:493–532, https://doi.org/10.1086/316162, 1998). There three main hypotheses for nature PS CSS (1) might be very young galaxies which will evolve into their way to becoming large galaxies. (2) because they confined (and enhanced in power) by interaction dense gas environments. (3) Alternately, transient or intermittent Each these may apply individual objects. relative number each population have significant implications galaxy paradigm. Proper motion studies over long time baselines helped determine hotspot speeds dozen establish that Multi-frequency polarization observations demonstrated many CSS/PS embedded a interstellar medium vigorously interacting it. detection emission line aligned source, blue-shifted Hi absorption, [OIII] lines indicates AGN feedback is present objects—possibly driven source. Also, evidence episodic range time-scales been discussed. closes discussion open questions prospects future.