Quantifying the ISM based on GeV gamma-ray and multiwavelength obervations

2021 Fiscal Year Final Research Report

• Project/Area Number: 17H02866
• Research Category: Grant-in-Aid for Scientific Research (B)
• Allocation Type: Single-year Grants
• Section: 一般
• Research Field: Astronomy
• Research Institution: Hiroshima University
• Principal Investigator: Mizuno Tsunefumi 広島大学, 宇宙科学センター, 准教授 (20403579)
• Project Period (FY): 2017-04-01 – 2021-03-31
• Keywords: 星間ガス / 宇宙線 / ガンマ線 / 多波長観測

Outline of Final Research Achievements

We have quantified the interstellar medium (ISM) and coscmi-rays (CRs) based on GeV gamma-ray and multiwavelength obervations, as well as studied the CR accelerator data in detail. On the latter we have published a detailed study of the X-ray morphology of VER J2019+368. On the former, we published the analysis of Chamaeleon molecular clouds (in particular the study of non-linearity between the dust emission and ISM density) and high-latitude HI clouds (in particular measurement of ISM density without an assuption of spin temperature). In addition, we have shown that by using HI line profile we can significantly improve the accuracy of ISM/CR measurements. The method has been applied to the MBM 53-55 molecular clouds and Pegasus loop region, and a dedicated paper is in preparation.

Free Research Field

X線ガンマ線天文学

Academic Significance and Societal Importance of the Research Achievements

星間空間を満たす星間ガスの定量は、星間現象（超新星爆発、分子雲形成、星形成など）を理解する根幹であり、現代天文学の主要テーマの一つである。星間ガスの測定は伝統的に21cm 線（原子ガス）および2.6mm 線（分子ガス）の電波サーベイによってなされてきたが、factor2 程度の大きな不定性があった。本研究はGeVガンマ線観測というロバストな星間ガスのトレーサーを基軸とした多波長観測により，星間ガスの定量を目指すもので，ダスト放射と星間ガスの非線形性，スピン温度の仮定によらないガスの定量，HI21cm線の輝線幅を用いた精密解析の提唱など多くの成果を上げることができた。