Star Formation Through Cosmic Time

Coordinators: Tom Abel, Alyssa A. Goodman, Christopher F. McKee, Paolo Padoan

Star formation is at the nexus of much of modern astrophysics, ranging from cosmology to planet formation. Massive stars are of particular importance, since they are responsible for creating most of the elements heavier than helium, for driving the evolution of galaxies and, quite likely, reionizing the universe. This workshop will focus on five areas of critical importance in contemporary research on star formation:

  1. Turbulence and magnetic fields in star formation. Turbulence and magnetic fields are dominant effects in the interstellar medium of galaxies. Magneto-hydrodynamic turbulence is an important fragmentation process for star forming clouds. Indeed, turbulent flows are ubiquitous in the star-forming gas; a self-consistent theory of star formation must account for how they are generated and how they affect star formation.
  2. The formation of massive stars. The formation of massive stars is a complex problem in radiation magnetohydrodynamics. The energy injected by newborn stars can either trigger or inhibit further star formation. Massive stars are particularly important in this regard because of their large ionizing luminosities, their powerful protostellar outflows and stellar winds, and their final supernova explosions. Thus, understanding massive star formation becomes critical to modeling feedback processes associated with star formation, both now and in the epoch of the first stars.
  3. The formation of star clusters. Stars, particularly massive stars, are usually formed in clusters, isolated star formation being an exception. This significantly enhances the feedback effects of star formation. It also emphasizes the importance of modeling star formation in a large scale environment, rather than in the context of isolated protostar evolution. The clustering of young stars may hold clues to their origin and provide an integral part of the star formation theory. Furthermore, star clusters are the only signposts of star formation that are directly observable in distant galaxies.
  4. Evolution of galaxy-scale star formation with redshift. Most star formation today occurs in disk galaxies, where it is organized by spiral density waves, and in irregular galaxies. Elliptical galaxies, galactic bulges, and thick disks of spiral galaxies formed at moderate redshifts, when most of the star formation in the universe occurred. What determines the rate and spatial distribution of star formation in galaxies at these different cosmic times?
  5. Primoridal star formation. Lastly, the formation of the first stars is in some respects the best defined star formation mode. The initial conditions are believed to be well constrained, turbulence and magnetic fields may be of secondary importance, and the gas chemistry is simpler than in present day molecular clouds. The stars formed are expected to be massive and short-lived. Primordial star formation is the ideal setting to study some fundamental problems of star formation in general, namely angular momentum transfer and star formation feedback. It is also timely, since observers are actively searching for evidence of primordial stars, both directly in galaxies at high redshift and indirectly in the composition of stars of very low metallicity.

The problem of star formation is vast, and we are explicitly excluding several important aspects: Low-mass star formation will not be a focus of this workshop since it has been more extensively studied in the past; and planets, disks and jets will not be a focus in view of the very successful recent KITP workshops on these topics. It should be noted that although disks and jets are not a focus of this workshop, they will be included when they are important to one of the four main topics of the workshop.

CONFERENCE: A one-week conference will be held from August 13-17 on ”Star Formation Through Cosmic Time.” One need not be a workshop participant to attend the conference.