A Redline Starburst: CO(2-1) Observations of an Eddington-limited Galaxy Reveal Star Formation at Its Most Extreme
Moustakas, J.; Rudnick, G. H.; Krips, M.; Hickox, R. C.; Geach, J. E.; Diamond-Stanic, A. M.; Tremonti, C. A.; Coil, A. L.; Sell, P. H.
Canada, United States, France
Abstract
We report observations of the CO(2-1) emission of SDSS J1506+54, a compact (r e ≈ 135 pc) starburst galaxy at z = 0.6. SDSS J1506+54 appears to be forming stars close to the limit allowed by stellar radiation pressure feedback models: the measured L_IR/L^{\prime }_CO\approx 1500 is one of the highest measured for any galaxy. With its compact optical morphology but extended low surface brightness envelope, post-starburst spectral features, high infrared luminosity (L IR > 1012.5 L ⊙), low gas fraction (M_H_2/M_\star \approx 15%), and short gas depletion time (tens of Myr), we speculate that this is a feedback-limited central starburst episode at the conclusion of a major merger. Taken as such, SDSS J1504+54 epitomizes the brief closing stage of a classic model of galaxy growth: we are witnessing a key component of spheroid formation during what we term a "redline" starburst.