SpS 8: Calibration of Star-Formation Rate Measurements Across the Electromagnetic Spectrum

Star-formation is one of the main processes that shape galaxies, and together with black-hole accretion activity, the two agents of energy production in galaxies. Star formation is important on a range of scales from star clusters/OB associations to galaxy-wide and even group/cluster scales[AU1]. Measuring and mapping the star-forming activity in galaxies has very important implications for our understanding of their broad-band spectra, the structure and evolution of the galaxies we observe in our local Universe (including our own Milky Way), as well as at cosmological distances.

Recently, studies of star-formation in sub-galactic and galaxy-wide scales have met significant advances owing to: (a) developments in the theory of stellar evolution, stellar atmospheres, and radiative transfer in the interstellar medium; (b) the availability of more sensitive and higher resolution data; and (c) observations in previously poorly charted[AU2] wavebands (e.g. Ultraviolet, Infrared, and X-rays).

However, despite the definition of SFR indicators in all accessible wavebands, these indicators give estimates of the SFR that typically differ by a factor of a few and sometimes up to one order of magnitude. This is due partly to physical effects (e.g. influence of interstellar dust; sensitivity to stellar populations of different ages, Initial Mass Function, etc) and partly to poor calibration (e.g. related to radiative transfer effects, uncertainties in stellar population synthesis). Recently attempts have been made to reconcile these differences and has led to the development of the first multi-wavelength SFR indicators and state-of-the art SED fitting tools.

Understanding and cross-calibrating SFR indicators is critical for obtaining a consistent picture of one of the defining processes in galaxies. This need becomes even more important given that current (e.g. Herschel[AU3], AKARI, WISE, Chandra, XMM-Newton) and future (e.g. JWST, ALMA, SPICA) observatories enable us to probe and measure star-forming activity in previously uncharted wavebands and environments. Assessment of the observational and theoretical progress made in the past few years and identification of the still open issues and calibration needs, is most needed in order to make the best use of the available data, and be best prepared for the forthcoming generation of observatories which will provide the next big leap in studies of extragalactic star-formation.

Topics addressed by this special session include:

  • Advances in the theory of stellar evolution and population synthesis.
  • Radiative transfer in the ISM and its effect in SFR measurements.
  • Traditional SFR indicators (resolved stellar populations, H?, [OII], optical continuum, radio, FIR luminosities) .
  • New SFR indicators (PAH, X-ray, new FIR and sub-mm bands) .
  • Measuring star-formation in different environments and redshifts.
  • Physical biases (e.g. effect of IMF, dust, metallicity, stellar population age, binary populations; quantifying the AGN contribution).
  • Cross-calibration issues and uncertainties of the different indicators.
  • Results from new missions (HST-COS, Herschel), and prospects for SFR measurements from future missions (JWST, ALMA, SPICA).