Special Session SS9  3 July 2024

Dust enrichment of early galaxies (z>5) in the era of JWST and ALMA

Aims and scope

The first billion years after the Big Bang witnessed the emergence of the first galaxies, whose stellar populations not only reionized the Universe, but also created the first heavy elements and dust. The rise of dust in the interstellar medium of galaxies plays a pivotal role in galaxy evolution as well as our understanding of this process. On the one hand, dust grains, by acting as catalysts for the formation of molecular hydrogen, by radiatively dissipating gravitational energy within collapsing clouds, and by shielding the molecules of these collapsing regions from the relentless emission of starlight, play a critical role in creating the physical conditions necessary for star formation. On the other hand, dust grains also play a somewhat detrimental role, obscuring our direct view of ongoing star formation, hampering our ability to study these fundamental processes. Until recently, the presence of dust and its role in the assembly of early galaxies was mainly studied through theoretical work. However, with the advent of the Atacama Large Millimeter/submillimeter Array (ALMA) and, more recently, the James Webb Space Telescope (JWST), we can now conduct detailed investigations on the dust content of primordial galaxies, either through its direct emission in the far-infrared, or through its imprint on the starlight of these galaxies. The recent discovery by JWST and ALMA of massive, optically dark, highly star-forming galaxies so early in the Universe as to challenge standard theories, undoubtedly highlights the synergy between these observatories. This new era of JWST and ALMA promises to shed ever more light on the complex processes governing the rise of dust in early galaxies and its profound consequences for their evolution.

This special session aims to bring together observers, simulators, theorists, to encourage discussion of the latest discoveries and advances on dust enrichment in the early Universe (z>5), made possible by JWST and ALMA observations. We will have two parts, one on the rise of dust in the early Universe, focusing in particular on the mechanism(s) of formation, the composition of this dust and its impact on starlight and early star formation; and a second on the use of dust as a tracer of galaxy evolution, focusing in particular on its use as proxies for the (cosmic) dust-obscured star formation, the conditions of the interstellar medium and the gas content of primordial galaxies. These parts will be followed by an in-depth discussion to inspire new avenues of research and advance our understanding of dust enrichment and its impact on galaxy formation in the early Universe.


  • The rise of dust in the early Universe (early dust enrichment, early dust composition, impact on early star formation)
  • Dust, a key tracer for understanding early galaxy evolution ([cosmic] dust-obscured SFR, ISM condition, and gas mass tracer)
  • Discussion: Is dust important or irrelevant for early galaxy evolution?

Invited speakers

  • David Elbaz CEA Paris-Saclay
  • Laura Sommovigo Flatiron Institute
  • Joris Witstok Kavli Institute for Cosmology

Scientific organisers

Benjamin Magnelli (DAp-AIM, CEA Paris-Saclay, France), Co-chair
Laure Ciesla (LAM, Marseille, France), Co-chair
Aswin Payyoor Vijayan (DTU, Denmark)
Livia Vallini (INAF, Observatory of Bologna, Italy)
Mengyuan Xiao (University of Genève, Switzerland)


laure.ciesla @ lam.fr

Updated on Wed May 29 15:12:41 CEST 2024