Scientific Rationale

Hydrogen Lyα emission and absorption are two of the major signatures for understanding galaxy star formation, the interstellar medium (ISM), the circumgalactic medium (CGM), and the intergalactic medium (IGM). Historically, it has been predicted that very young, metal-poor galaxies should show strong Lyα emission, the recombination line of the most abundant element. Observational studies have used Lyα emission as a signpost of star formation and active galactic nucleus activity, pushing galaxy observations to the highest-redshift frontiers. Increasingly, many projects focused on deep imaging and spectroscopy exploit the resonant nature of Lyα emission to measure and map HI gas distributions in the ISM, the CGM, and the IGM over the large-scale structure (LSS) at the epoch of reionization and post-reionization. Synchronized with this observational progress and supported by strong computational power, recent numerical simulations have successfully reproduced the observational properties of Lyα emission with various advanced techniques including radiative transfer modeling. It is time to discuss the progress of recent observational and theoretical studies of Lyα emission and absorption and to explore the next generation of Lyα studies with forthcoming large facilities and technologies, such as the James Webb Space Telescope. More specifically, we will focus on discussing three topics and their relevant science results and projects:

• Lyα emission as a probe of galaxy formation and evolution
• Lyα emission and absorption as a probe of the ISM/CGM/IGM/LSS
• Lyα emission as a probe of reionization

This is the second Lyα workshop after the successful one held in Utah in March 2017:

Confirmed Speakers

Roland Bacon   (Lyon)
Jeremy Blaizot   (CRAL)
Sebastiano Cantalupo   (ETH Zurich)
Len Cowie   (Hawaii)
Dawn Erb   (Wisconsin)
Andrea Ferrara   (Pisa)
Steve Finkelstein   (UT Austin)
Matthew Hayes   (Stockholm)
Khee-Gan Lee   (LBNL)
Sangeeta Malhotra   (Arizona State)
Chris Martin   (Caltech)
Masami Ouchi   (Tokyo)
Dan Stark   (Arizona)
Tommaso Treu   (UCLA)
Anne Verhamme   (Geneva)
Hidenobu Yajima   (Tohoku)

Scientific Organizing Committee

Len Cowie   (Hawaii)
Andrea Ferrara   (Pisa)
Anne Jaskot   (Massachusetts)
Yuichi Matsuda   (NAOJ)
Masami Ouchi   (Tokyo) [Chair]
Laura Pentericci   (Rome)
Alice Shapley   (UCLA)
Anne Verhamme   (Geneva) [Co-Chair]
Lutz Wisotzki   (Potsdam)
Zheng Zheng   (Utah) [Co-Chair]
Zhenya Zheng   (Shanghai)

Local Organizing Committee at U.Tokyo

Yoshiaki Ono
Masami Ouchi
Takatoshi Shibuya
Kazuhiro Shimasaku
Jun Toshikawa


Sakura CLAW is supported by:



Contact: lya2018 @

The webpage banner: LARS galaxy (courtesy of Matthew Hayes) and cherry blossoms