Research

I'm studying how galaxies formed and evolved across cosmic time using large telescopes such as JWST, ALMA, Subaru, and HST.

Observing Early Universe with James Webb Space Telescope

Our team will search for the first galaxies and investigate the physical properties of distant galaxies with the James Webb Space Telescope (JWST).

• Our Cycle 1 observing program for physical properties of galaxies (link to the STScI page)

• Our Cycle 1 observing program for first galaxies (link to the STScI page)

We found many galaxy distant candidates 13.3-13.6 billion light-years away, whose number density is surprizingly higher than model predictions.

• Harikane et al. (2023), The Astrophysical Journal Supplement Series, Volume 265, Issue 1, id.5, 27 pp. (NASA/ADS, arxiv)

We found the most distant galaxy candidate at that time, 13.5 billion light-years away, named HD1. This galaxy candidate will be observed with the JWST.

• Most Distant Galaxy Candidate Yet (UTokyo/ICRR, NAOJ, New York Times)

• Harikane et al., (2022) The Astrophysical Journal, Volume 929, Issue 1, id.1, 15 pp. (NASA/ADS, arxiv)

Statistical Census of Distant Galaxies

Using the Subaru/Hyper Suprime-Cam and Hubble Space Telescope data, we construct the largest sample of high redshift galaxies, and study the luminosity functions and galaxy-dark matter halo connection to understand the star formation history of the universe.

• Harikane et al. (2016), The Astrophysical Journal, Volume 821, Issue 2, article id. 123, 23 pp. (NASA/ADS, arxiv)

• Harikane et al. (2018a), Publications of the Astronomical Society of Japan, Volume 70, Issue SP1, id.S11 (NASA/ADS, arxiv)

• Harikane et al. (2021), The Astrophysical Journal Supplement Series, in press, (NASA/ADS, arxiv)

High Redshift Protocluster

Using the Subaru/Hyper Suprime-Cam data, we search for protocluster, a progenitor of a cluster of galaxies in the present-day universe. We discovered the most distant protocluster ever found, and our discovery was broadcasted in many media (NHK, newspapers, AFP, etc.). 

• Harikane et al. (2019), The Astrophysical Journal, Volume 883, Issue 2, article id. 142, 16 pp. (NASA/ADS, arxiv)

• Oldest Galaxy Protocluster forms "Queen's Court" (NAOJ, UTokyo/ICRR, Nature research highlights)

Interstellar Medium of High Redshift Galaxies

We investigate metal emission/absorption lines such as oxygen and carbon from galaxies with large telescopes such as ALMA, and study properties of interstellar medium of high redshift galaxies.

• Harikane et al. (2018b), The Astrophysical Journal, 859, 2, 84, 21 pp. (NASA/ADS, arxiv)

• Harikane et al. (2020a), The Astrophysical Journal, 896, 2, 93, 19 pp. (NASA/ADS, arxiv)

• Harikane et al. (2020b), The Astrophysical Journal, 902, 2, 117, 12 pp. (NASA/ADS, arxiv)