Jet-driven star formation in kpc-scale infant radio sources
We present the first systematic study of jet-induced star formation in Compact Steep Spectrum (CSS) radio galaxies. The powerful galaxy-sized radio sources hosted in CSS galaxies are the infancy stage of radio galaxy evolution, and hence, crucial in understanding the radio-mode AGN feedback. Radio source driven starbursts only have observational evidence in older, large-scale radio galaxies so far, and are predicted for compact radio sources in theoretical simulations. Using UV continuum as a direct diagnostic for massive young stellar population, we detected extended UV continuum emitting regions in Hubble imaging of six nearby (z < 0.6) CSS host galaxies. Likely to be star forming regions, these UV knots are found spatially aligned along radio jet structure, which suggests jet-induced star formation. Age estimations with stellar population synthesis shows the observations are consistent with star forming activity triggered by the current or an earlier episode of radio emission. Our findings are a strong candidate for positive AGN feedback in compact radio galaxies.