%0 Journal Article %T Molecular hydrogen in absorption at high redshifts %+ Institut d'Astrophysique de Paris (IAP) %A Balashev, S. A. %A Noterdaeme, P. %< avec comité de lecture %J Experimental Astronomy %8 2022 %D 2022 %Z 2203.15582 %Z 2022ExA...tmp...28B %R 10.1007/s10686-022-09843-y %K Molecular hydrogen %K Quasar absorption lines %K Active galactic nuclei %Z Sciences of the Universe [physics]Journal articles %X Absorption lines from molecular hydrogen (H2) in the spectra of background sources are a powerful probe of the physical conditions in intervening cold neutral medium. At high redshift, z >2 , H2 lines are conveniently shifted in the optical domain, allowing the use of ground-based telescopes to perform high-resolution spectroscopy, which is essential for a proper analysis of the cold gas. We describe recent observational progress, based on the development of efficient pre-selection techniques in low-resolution spectroscopic surveys such as the Sloan Digital Sky Survey (SDSS). The next generation of spectrographs with high blue-throughput, such as CUBES, will certainly significantly boost the efficiency and outcome of follow-up observations. In this paper, we discuss high priority science cases for CUBES, building on recent H2 observations at high-z: probing the physical conditions in the cold phase of regular galaxies and outflowing gas from active galactic nucleus. %G English %L insu-03748289 %U https://insu.hal.science/insu-03748289 %~ INSU %~ CNRS %~ IAP %~ SORBONNE-UNIVERSITE %~ SORBONNE-UNIV %~ SU-SCIENCES %~ SU-TI %~ ANR %~ ALLIANCE-SU