Letters of Intent for 2015

LoI 2015-208
The Lyman alpha Universe


3 August 2015 to 14 August 2015


Honolulu, Hawaii, United States


Daniel Schaerer (daniel.schaerer@unige.ch)

Coordinating division:

Division J Galaxies and Cosmology

Co-Chairs of SOC:

SCHAERER Daniel (Geneva Observatory)
HU Esther (Institute for Astronomy, Honolulu)

Chair of LOC:




Topics for the proposed 2-3 day 'Focus Meeting' at the IAU General Assembly 2015:

- Lyman-alpha emitters and their connection with other galaxy populations
- Star-formation probed by Lyman-alpha
- The nature of Lyman-alpha blobs
- The interstellar and circum-galactic medium at high and low redshift
- Probing the high-redshift inter-galactic medium and reionization
- Cosmological uses of Lyman-alpha (galaxy clustering, dark energy)



Over recent years, the Lyman-alpha line has become a widely used astrophysical
tool used in many studies related to galaxy formation and evolution, the interstellar
and intergalactic medium (ISM and IGM), structure formation, cosmic reionization,
and even dark energy.

For example Lyman-alpha is used to determine redshifts and star-formation rates.
Its profile and strength can also provide constraints on the age of star-forming
galaxies, on their dust content and other ISM properties and on gas outflows.
Furthermore Lyman-alpha luminosity functions (LFs), their redshift evolution and
comparison with e.g. UV LFs provide invaluable information on galaxy populations and
their evolution. Lyman-alpha is of great interest to identify very distant galaxies,
it serves as a signpost for extremely metal-poor/PopIII galaxies, and is established
as a crucial tool to measure cosmic reionization. This line is used to trace the
cosmic web and its dynamics, including the fundamental in- and outflow processes.
Finally, Lyman-alpha galaxy surveys are also being used to map large scale structure,
and to probe dark matter properties.

Expanding the discoveries made during the last decade, new data is being acquired
at a rapid pace with many ground-based telescopes and recent HST instruments (e.g. COS,
WFC3/grism), and new facilities/instruments (e.g. HETDEX, HyperSuprimeCam@SUBARU, MUSE@VLT)
are starting to operate. A diversity of new models, ranging e.g. from radiation transfer codes
to galaxy formation models, have also been developped to interpret these observations.

To discuss these latest developments, observational and modeling results, we propose
a 2-3 day Focus Meeting on the topics described above, fostering interactions
between the various communities. The timing of the meeting is optimal to present many
expected results from the above mentioned facilities and ongoing projects.


* Andrea Ferrara, Scuola Normale Superiore, Pisa, Italy
* Matthew Hayes, Stockholm Observatory, Sweden
* Esther Hu, Institute for Astronomy, Honolulu, USA (co-chair(
* Masami Ouchi, University of Tokyo, Japan
* Claudia Scarlata, Caltech, USA
* Daniel Schaerer, Geneva Observatory and University, Switzerland (co-chair)

IAU General Assembly
Honolulu, 3-14 August 2015

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