Updated on 2026/09/03

写真a

 
IKEDA Hiroyuki
 

Research Areas

  • Natural Science / Astronomy

Education

  • Ehime University   Graduated

    2005.4 - 2009.3

  • Ehime University   Master's Course   Completed

    2009.4 - 2011.3

  • Ehime University   Doctor's Course   Completed

    2011.4 - 2014.3

 

Papers

  • High-Resolution Infrared Spectroscopy of IRS 16CC and IRS 33N: Stellar Parameters and Implications for Star Formation Near Sgr A* Reviewed International journal

    Shogo Nishiyama, Wakana Sato, Moeka Hotta, Momoka Ikarashi, Hiromi Saida, Yohsuke Takamori, Tetsuya Nagata, Hiroyuki Ikeda, and Masaaki Takahashi

    Universe   11 ( 332 )   2025.10

    　More details

    IRS 16CC and IRS 33N are among more than 100 young, massive stars identified within 0.5 pc from the Galactic central supermassive black hole Sgr A*, where conventional star formation processes are expected to be strongly suppressed. A subset of these stars, including IRS 16CC, has been confirmed to reside in a clockwise rotating stellar disk, and is thought to have formed in a massive, gaseous disk around Sgr A*. In contrast, other young massive stars, such as IRS 33N, exhibit dynamical behaviors that deviate significantly from those of the disk population, and their formation mechanism is still uncertain. To investigate their formation mechanism, we carried out near-infrared, high-resolution spectroscopic observations of IRS 16CC and IRS 33N using the Infrared Camera and Spectrograph on the Subaru telescope, equipped with an adaptive optics system. We compared the profiles of He I absorption lines with synthetic spectra generated from model atmospheres, and then compared derived stellar parameters with stellar evolutionary tracks to estimate their ages and initial masses. Our analysis yields their effective temperatures of ∼23,000 K, surface gravities of ∼2.8, and initial masses of ~37𝑀⊙ and ~27𝑀⊙, consistent with spectral types of B0.5–1.5 supergiants. The ages of IRS 16CC and IRS 33N are estimated to be 4.4 Myr and 5.3 Myr, respectively. These results suggest that, despite their different dynamical properties, the two stars are likely to share a common origin.

Presentations

  • Physical Properties of Broad-Line AGNs in the PFS-SSP Galaxy Evolution Survey: Initial Results from S25A Observations International coauthorship International conference

    Keiya Takeshita, Yoshiki Toba, Yoshiki Matsuoka, Ayumi Takahashi, Kohei Ichikawa, Tohru Nagao, Hiroyuki Ikeda, Jialai Wang, Alberto Rodríguez Ardila, Thaisa Storchi Bergmann

    SMBH growth viewed with large field surveys: special focus on the initial results from Subaru PFS  2026.3 

  • A Red Quasar Survey in the COSMOS Field

    Hiroyuki Ikeda

    17th East Asian VLBI Workshop  2026.9 

  • High-resolution Near-infrared Spectroscopy of Late and Early-type Stars in the Central Parsec International conference

    Shogo Nishiyama, Brian Thorsbro, Wakana Sato, Moeca Hotta, Momoka Ikarashi, Natsumi Sasaki, Takeru Chiba, Hiromi Saida, Yohsuke Takamori, Masaaki Takahashi, Tetsuya Nagata, Hiroyuki Ikeda

    Traversing the Galactic Center in Space and Time  2026.5