Powerful Outflows of Compact Radio Galaxies

Abstract Gigahertz peaked spectrum (GPS) and compact steep spectrum (CSS) sources are compact radio galaxies (RGs), with jets extending up to 20 kpc and ages <10 3 yr. They are considered to evolve to Fanaroff–Riley RGs, but the real scenario to explain the compact sources remains unsolved. The young compact jets make GPS/CSS ideal for studying feedback in the nuclear region of active galactic nuclei because the jets are just starting to leave this region. Numerical simulations and jet power estimates suggest that compact sources can drive outflows on scales several times larger than the radio source itself, but the lack of suitable data limits comparisons between theory and observation. We carried out an optical spectroscopic study of 82 CSS/GPS with Sloan Digital Sky Survey-DR12 data to investigate the influence of compact jets in the gas. We found outflowing gas components in the [O iii ] λ 5007 emission lines in half of our sample. The kinetic energy of the outflowing gas in compact sources is comparable to that observed in extended RGs, indicating that the compact jets can drive powerful outflows similar to those in FR RGs. The observed anticorrelation between the kinetic power of the outflow and the radio luminosity suggests an interaction between the young jet and the interstellar medium (ISM). This finding provides significant observational support for previous simulations of jet–ISM interactions and supports the evolutionary scenario for RGs. However, the lack of sources with high kinetic efficiency indicates that some compact galaxies may be frustrated sources.