Special Session SS5  26 June 2019

Aims and scope

The rest-frame UV spectrum of galaxies (~[1000A-3000A]) abounds with information. It is a tracer of the recent star-formation activity: young, massive, stars shine bright in the UV. In other words, UV light provides us a direct means to probe young galaxies in the process of formation -- understanding of which is a major challenge of modern astronomy. The slope of the UV stellar continuum can be used to constrain the dust content of galaxies at very high redshift. Bright nebular lines -- the Lyman-alpha line of Hydrogen in particular (1216A) can contain up to 40% of the bolometric luminosity of a young galaxy -- are used to get a systemic redshift of distant objects, and a clue on their ionisation state, and metal enrichment. Metallic absorption lines also tell us about the kinematics and porosity of the interstellar medium. However, this part of the spectral energy distribution of galaxies can only be observed from the ground during the first billion years of galaxy formation and evolution, when it is conveniently redshifted into IR domains (z > 6) and in the optical (z >~2). The next 10 billion years of cosmic time, during which tiny young galaxies have matured and grown, is entirely accessible to us in the rest-frame UV window, albeit only with space-based telescopes given the atmospheric opacity.

Over the past 4 decades, only four major UV missions have been launched (IUE 1978-1996, HST 1990-today, GALEX 2003-2013, Astrosat 2015-today), starting to bridge the gap and allowing us to see the more local galaxies in the same light as the most distant ones. These facilities have made it possible to investigate the physics of star-formation (UV being the direct probe) at the smallest scale possible e.g., individual HII regions in local galaxies. The last three years have witnessed a series of discoveries (with due credit to HST) of galaxies leaking Extreme UV (EUV, lambda < 912 A) radiation that have revolutionised our understanding of Cosmic Reionization.

The primary goal of this symposium is to gather the broad community of researchers using UV facilities for their science, to discuss on-going and future survey strategies, access to precious data, and design future missions. In this context, it is worth mentioning that the Astronomical Society of India, invited participant of EWASS 2019, is strongly involved in the successful AstroSat mission: an Indian Space Observatory, having on-board UltraViolet Imaging Telescope (UVIT) plus a low-resolution slit-less spectrograph.


  • From emission to absorption: the richness of the (ionising) UV spectrum of galaxies
  • Galaxy assembly through cosmic time, as probed in the UV
  • UV astronomy: existing and future facilities/surveys, synergies with next-generation instruments

Invited speakers

  • Matthew Hayes (Stockholm University)
  • Claudia Scarlata (University of Minnesota)
  • Jane Rigby (NASA)

Scientific organisers

  • Francoise Combe (OBSPM, France)
  • John Chisholm (UCA Santa Cruz, USA)
  • Alaina Henry (StScI, USA)
  • Pascal Oesch (University of Geneva)
  • Kanak Saha (IUCAA, India)
  • Anne Verhamme (University of Geneva)


Anne Verhamme: anne.verhamme @ unige.ch; Pascal Oesch: pascal.oesch @ unige.ch; Kanak Saha: kanak @ iucaa.in

Updated on Wed Feb 06 23:37:44 CET 2019