IAU 250:
Massive Stars as
Cosmic Engines


Maintained by W-W

Scientific Rationale

Within the past few years, great progress has been made towards our understanding of the astrophysical role played by massive stars. From an observational perspective, temperatures of OB stars have been revised downward based on the most recent observations with FUSE, HST and ground-based facilities; the role of clumping in stellar winds has been recognized, with potentially dramatic consequences for stellar evolution, due to its influence on derived mass-loss rates; close binaries with masses of up to 80 solar masses have been identified and studied visually and with exquisite detail using Chandra, XMM, VLA; visibly obscured young massive clusters have been identified at our Galactic Centre, elsewhere in our own Milky Way and in external galaxies. These have been studied with HST, VLT, Gemini and Subaru, exploiting natural guide star Adaptive Optics (AO) techniques from the ground. Increasingly the use of AO with laser guide stars is expected to revolutionise the study of massive star forming regions.

Quantitative spectroscopy of massive stars beyond the Local Group has been undertaken with VLT and Keck to disentangle chemical evolution of galaxies in the nearby Universe and to determine independent distances; star formation histories have been inferred from population/spectrum ynthesis of resolved/unresolved populations of nearby star forming galaxies; nearby starbursts – templates for high redshift counterparts - have been studied with FUSE, HST, GALEX and Spitzer. Large surveys for star forming galaxies from redshifts 1 to 6, making use of colour selection techniques at optical, infrared and sub-mm wavelengths, have provided quantitative measures of their massive stellar populations over most of the age of the universe, including their past history of star formation, the IMF, assembled stellar masses, metallicities and chemical yields; from space, HETE and SWIFT have allowed an increasing number of GRBs to be studied in detail, with rapid follow-up from ground-based facilities permitting chemical information on their host galaxies to be obtained. These are all tremendously exciting topics, at the forefront of present-day astrophysical research and providing some of the core scientific cases for the next generation of extremely large telescopes currently under development.

Theoretically, great advances have been made towards improved evolutionary and atmospheric models for massive stars allowing for rotation and magnetic fields, and towards the evolution of massive binary systems; the impact of internal waves generated at the boundary of the convective core on the transport of angular momentum and chemical species in the stellar interior; important developments have taken place with respect to spectral synthesis of starbursts, improved spectral energy distributions of young stellar populations, hydrodynamic simulations of GRB explosions, and notably numerical simulations of star formation at the earliest epochs, including very massive Population III stars which are thought to play the dominant role in the reionization of the universe at redshift z > 6.

The key astrophysical problems for the symposium are:

  • Atmospheres of massive stars;
  • Physics and evolution of massive stars;
  • Massive stellar populations in the nearby Universe;
  • Hydrodynamics and feedback from massive stars in galaxy evolution;
  • Massive stars as probes of the early Universe.