Abstract

Comprehensive and systematic studies of the molecular content of galaxies during the epochs that are associated with the peak (z approx 1-3), and subsequent winding down (z < 1) of star formation in the Universe are enabling us to illustrate the important role that cold gas, the fuel for star formation, has played in the assembly of galaxies across cosmic time. Modest sized surveys already provide robust molecular gas detections in hundreds of normal, star forming galaxies (SFGs), from redshifts 0-2.5. Furthermore, spatially resolved spectroscopy in both the (sub)mm and NIR wavelengths now enable us to study the detailed kinematics, star formation, and ISM properties in SFGs on few kpc scales. In this talk, we focus on results from PHIBSS , an IRAM legacy program with NOEMA , where we are mapping the CO J =3-2 or J-2-1 line emission in approximately 200 such galaxies from z=0.5-2.5; we find that galaxies at these epochs are very gas rich, relative to their star-forming counterparts in the local Universe. These SFGs likely develop from continuous, rapid accretion of gas from their dark matter halos, and their evolution is strongly influenced by internal, secular evolution, and by powerful feedback from star formation and accreting central massive black holes. We also discuss the first scaling relations for massive star forming galaxies that we derive from these data, and the impact of all these new observations on our understanding of galaxy evolution in the early Universe.