A redline starburst: CO(2-1) observations of an Eddington-limited galaxy
  reveal star formation at its most extreme
  We report observations of the CO(2-1) emission of SDSSJ1506+54, a compact
(r_e~135pc) starburst galaxy at z=0.6. SDSSJ1506+54 appears to be forming stars
close to the limit allowed by stellar radiation pressure feedback models: the
measured L_IR/L'_CO 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>10^12.5
L_Sun), low gas fraction (M_H2/M_stars~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, SDSSJ1504+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.
