The SSA22 H i Tomography Survey (SSA22-HIT). I. Data Set and Compiled Redshift Catalog

Ken Mawatari, Akio K. Inoue, Toru Yamada, Tomoki Hayashino, J. Xavier Prochaska, Khee Gan Lee, Nicolas Tejos, Nobunari Kashikawa, Takuya Otsuka, Satoshi Yamanaka, David J. Schlegel, Yuichi Matsuda, Joseph F. Hennawi, Ikuru Iwata, Hideki Umehata, Shiro Mukae, Masami Ouchi, Yuma Sugahara, Yoichi Tamura

Research output: Contribution to journalArticlepeer-review


We conducted a deep spectroscopic survey, named SSA22-HIT, in the SSA22 field with the DEep Imaging MultiObject Spectrograph (DEIMOS) on the Keck telescope, designed to tomographically map high-z H i gas through analysis of Lyα absorption in background galaxies’ spectra. In total, 198 galaxies were spectroscopically confirmed at 2.5 < z < 6 with a few low-z exceptions in the 26 × 15 arcmin2 area, of which 148 were newly determined in this study. Our redshift measurements were merged with previously confirmed redshifts available in the 34 × 27 arcmin2 area of the SSA22 field. This compiled catalog containing 730 galaxies of various types at z > 2 is useful for various applications, and it is made publicly available. Our SSA22-HIT survey has increased by approximately twice the number of spectroscopic redshifts of sources at z > 3.2 in the observed field. From a comparison with publicly available redshift catalogs, we show that our compiled redshift catalog in the SSA22 field is comparable to those among major extragalactic survey fields in terms of a combination of wide area and high surface number density of objects at z > 2. About 40% of the spectroscopically confirmed objects in SSA22-HIT show reasonable quality of spectra in the wavelengths shorter than Lyα when a sufficient amount of smoothing is adopted. Our data set enables us to make the H i tomographic map at z ≳ 3, which we present in a parallel study.

Original languageEnglish
Article number208
JournalAstronomical Journal
Issue number5
StatePublished - 1 May 2023


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