Special Session SS14  28 June 2017

Aims and scope

Damped Lyman-alpha absorbers (DLAs), and in general Quasar absorbers are hydrogen-rich systems that are observed in unparalleled detail in absorption, but elusively detected in emission as low-mass galaxies. Since their selection is independent of luminosity and morphology, they are complementary to the study of galaxies at high z and low metallicity. In this session we intend to bring together the communities that study DLAs in emission and in absorption with the community that offers a theoretical perspective on the formation of- and relation of absorbers with galaxies.

Galaxy counterparts

The next challenge in the study of galaxy evolution is to understand the physical processes of the formation of galaxies and structures and their interactions with the medium surrounding them. Of particular importance are the processes through which these galaxies accrete gas and subsequently form stars. The identification and characterization of galaxy counterparts associated with DLAs and other absorbers is crucial to understand the nature of these systems, and the role of gas inside and around galaxies. In recent years there has been a strong development in the characterisation of DLA galaxies with metal-rich absorbers that are detected in emission (X-Shooter, SINFONI, MUSE, ALMA).

Interstellar medium

Absorption-line spectroscopy of QSOs, Gamma-Ray Bursts, and more recently SNe, allowed the community to characterize the interstellar medium of the absorbing systems in terms of chemistry, metals, dust, and molecular content, kinematics, and physical properties, such as ionization, out to high redshift and low metallicities. In the recent years there have been exciting advances. For instance, the detection of high-metallicity dusty DLA systems, strong DLAs, and molecules. On the low metallicity end, a picture is emerging where DLAs are associated with dwarf galaxies. The relative abundances of DLAs have been recently characterized in terms of dust depletion, nucleosynthesis, and metallicity, indicating significant presence of dust in some DLAs, and recent star formation in others. This has a strong impact in our understanding of the evolution of DLA metallicity with redshift. Overall, large DLA abundance compilations have been now collected from the literature. Finally, the results from the X-shooter surveys of DLAs towards QSOs and GRBs are coming up.

Numerical simulations

While observations of galaxy-DLA pairs in the past decade have given us more insight in the diverse nature of absorbers, our current understanding is primarily based on the most metal-rich ones. To reach a greater understanding therefore hinges on numerical simulations that are carried out with an ever greater resolution. Previous simulations have yielded varied results because of differences in assumed input physics, but recently have seen a much improved agreement with observations. In particular, simulations are fundamental when exploring the full sample of DLAs, both metal-poor and -rich ones. Metal-rich absorbers are observed to have relatively massive host galaxies, low-metallicity counterparts have few assigned host galaxies. Simulations largely agree with this bias and suggest that average DLA hosts have low masses with some DLAs arising in more massive LBGs.

While observations of DLAs only probe a pencil-beam through a cloud and direct observations of DLA sizes are few and far between, the impact parameters between the host galaxy and the QSO line of sight is a useful proxy. Recent simulations can now reproduce correlations between column density and galaxy masses. The observed relation between velocity width and absorber metallicity can also largely be explained by simulations that include feedback from galaxy winds, although problems still arise in explaining the highest velocity width absorbers, and the observed spread of the relation is not well reproduced.


Topics of interest include:

  • DLAs and similar absorbing systems
  • Galaxy counterparts of DLAs (and other absorbers)
  • Scaling relations, observed and theoretical
  • Radio and optical IFU DLA emission
  • DLA formation theory
  • DLA chemistry
  • Star formation in DLAs
  • High-metallicity and strong DLAs
  • Low-metallicity DLAs
  • Dust and metals in DLAs
  • Molecules in DLAs
  • DLA galaxy simulations
  • Absorbing systems towards Gamma-Ray Bursts
  • Absorbing systems towards Superluminous Supernovae

Invited speakers

  • Johan Fynbo (DARK Copenhagen)
  • Marcel Neeleman (University of California)
  • Pasquier Noterdaeme (CNRS Paris)
  • Joop Schaye (Leiden University)
  • Lorrie Straka (Leiden University)

Scientific organisers

  • Lise Christensen (DARK Copenhagen) co-chair
  • Annalisa De Cia (ESO HQ) co-chair
  • Sara Ellison (University of Victoria)
  • Jens-Kristian Krogager (IAP Paris)
  • Thomas Krühler (MPE Garching)
  • Cédric Ledoux (ESO Chile)
  • Palle Møller (ESO HQ)
  • Céline Péroux (LAM Marseille)
  • Patrick Petitjean (Université Paris)
  • Lorrie Straka (Leiden University)

adecia @ eso.org

Updated on Wed Dec 21 12:44:39 CET 2016