We present the first systematic search for UV signatures from radio
source-driven AGN feedback in Compact Steep Spectrum (CSS) radio galaxies.
Owing to their characteristic sub-galactic jets (1-20 kpc projected linear
sizes), CSS hosts are excellent laboratories for probing galaxy scale feedback
via jet-triggered star formation. The sample consists of 7 powerful CSS
galaxies, and 2 galaxies host to radio sources >20 kpc as control, at low to
intermediate redshifts (z<0.6). Our new HST images show extended UV continuum
emission in 6/7 CSS galaxies; with 5 CSS hosts exhibiting UV knots co-spatial
and aligned along the radio-jet axis. Young (5 M⊙​)
stellar populations are likely to be the dominant source of the blue excess
emission in radio galaxies at these redshifts. Hence, the radio-aligned UV
regions could be attributed to jet-induced starbursts. Lower near-UV SFRs
compared to other indicators suggests low scattered AGN light contribution to
the observed UV. Dust attenuation of UV emission appears unlikely from high
internal extinction correction estimates in most sources. Comparison with
evolutionary synthesis models shows that our observations are consistent with
recent (~1-8 Myr old) star forming activity likely triggered by current or an
earlier episode of radio emission, or by a confined radio source that has
frustrated growth due to a dense environment. While follow-up spectroscopic and
polarized light observations are needed to constrain the activity-related
components in the observed UV, the detection of jet-induced star formation is a
confirmation of an important prediction of the jet feedback paradigm.Comment: Submitted to Ap