SMA Observations of the Archetypal Compact Steep-spectrum Radio Source 3C 303.1

Abstract

AGN (active galactic nuclei) feedback plays a crucial role in shaping galaxy evolution. Numerical simulations show that the kinetic energy transfer efficiency from radio jets to interstellar medium (ISM) is relatively high, suggesting a significant role of radio jets in the feedback. We investigate AGN feedback on cold gas in the compact steep-spectrum (CSS) radio source 3C 303.1. CSS sources are largely young radio galaxies evolving through dense environments of their host galaxies. This early evolutionary phase likely represents a critical stage in which the radio source has maximum impact on host galaxy evolution. 3C 303.1 is the only CSS source so far showing alignment in optical, X-ray and UV with the radio structure, making it an interesting source to investigate jet-feedback. We present continuum and spectral line observations of the J=3-2 transition of carbon monoxide ($^{12}$CO) of 3C 303.1, obtained with the Submillimeter Array. We detect continuum emission at 221.1 and 271.2 GHz. We do not detect the $^{12}$CO(J=3-2) line and derive an upper limit on the molecular gas mass of $\sim 2.3 \times 10^{9}\ \mathrm{M_\odot}$. The gas to-dust mass (G/D) ratio is found to be at the lower end of typical Galactic values, and the star-formation rate (SFR) derived is moderate but declining likely due to a recent quenching event. Therefore, $^{12}$CO(J=3-2) non-detection, relatively low G/D ratio, and the moderate but declining SFR point to the shock-heating and/or removal of CO gas by AGN, consistent with the AGN feedback signatures observed in 3C 303.1.