A superluminous supernova in high surface density molecular gas within the bar of a metal-rich galaxy

We report the Atacama Large Millimeter/submillimeter Array observations of the metal-rich host galaxy of superluminous supernova (SLSN) PTF10tpz, a barred spiral galaxy at z = 0.03994. We find the CO(1-0) emission to be confined within the bar of the galaxy. The distribution and kinematics of molecular gas in the host galaxy resemble gas flows along two lanes running from the tips of the bar toward the galaxy center. These gas lanes end in a gaseous structure in the inner region of the galaxy, likely associated with an inner Lindblad resonance. The interaction between the large-scale gas flows in the bar and the gas in the inner region plausibly leads to the formation of massive molecular clouds and consequently massive clusters. This in turn can result in formation of massive stars, and thus the likely progenitor of the SLSN in a young, massive cluster. This picture is consistent with SLSN PTF10tpz being located near the intersection regions of the gas lanes and the inner structure. It is also supported by the high molecular gas surface densities that we find in the vicinity of the SLSN, surface densities that are comparable with those in interacting galaxies or starburst regions in nearby galaxies. Our findings therefore suggest in situ formation of massive stars due to the internal dynamics of the host galaxy and also lend support to high densities being favorable conditions for formation of SLSN progenitors.