東京大学 : 宇宙航空研究開発機構宇宙科学研究所(JAXA)(ISAS)
宇宙航空研究開発機構宇宙科学研究所(JAXA)(ISAS)
University of California, Los Angeles
宇宙航空研究開発機構宇宙科学研究所(JAXA)(ISAS)
宇宙航空研究開発機構宇宙科学研究所(JAXA)(ISAS)
東京大学 : 宇宙航空研究開発機構宇宙科学研究所(JAXA)(ISAS)
東京大学 : 宇宙航空研究開発機構宇宙科学研究所(JAXA)(ISAS)
DePaul University
著者所属（英）
The University of Tokyo : Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency (JAXA)(ISAS)
Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency (JAXA)(ISAS)
University of California, Los Angeles
Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency (JAXA)(ISAS)
Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency (JAXA)(ISAS)
The University of Tokyo : Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency (JAXA)(ISAS)
The University of Tokyo : Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency (JAXA)(ISAS)
DePaul University
出版者
宇宙航空研究開発機構(JAXA)
出版者（英）
Japan Aerospace Exploration Agency (JAXA)
雑誌名
宇宙航空研究開発機構特別資料
雑誌名(英)
JAXA Special Publication: The Cosmic Wheel and the Legacy of the AKARI archive: from galaxies and stars to planets and life
巻
JAXA-SP-17-009E
ページ
379 - 382
発行年
2018-03-09
会議概要（会議名, 開催地, 会期, 主催者等）
第4回「あかり」国際会議 (2017年10月17-20日. 東京大学), 文京区, 東京
会議概要（会議名, 開催地, 会期, 主催者等）（英）
The 4th AKARI International Conference: The Cosmic Wheel and the Legacy of the AKARI archive: from galaxies and stars to planets and life (October 17-20, 2017. The University of Tokyo), Bunkyo-ku, Tokyo, Japan
抄録（英）
We made systematic observations of the HI Br alpha (4.05 micrometers) and Br beta (2.63 micrometers) lines in 52 nearby (z less than 0.3) ULIRGs with AKARI. Our observations show that ULIRGs have a tendency to indicate higher Br beta/Br alpha line ratios than those observed in Galactic HII regions, and three galaxies in the observed sample show the anomaly of the Br beta/Br alpha line ratios (in the order of 1.0), which are significantly higher than that of case B (0.565). The high Br beta/Br alpha line ratios cannot be explained by the combination of the dust extinction and the case B, since dust extinction reduces the ratio. We simulate HII regions in the ULIRGs with the Cloudy code, and show that the high Br beta/Br alpha line ratios can be explained with the combination of the optically thick Br alpha line and the optically thin Br beta line. To achieve the column density large enough to make the Br alpha line optically thick, the gas density is required as high as n in the order of 10(exp 8) cm(exp -3). Hence our results suggest that star-formation activity in ULIRGs occurs preferentially in high-density clouds.
内容記述
形態: カラー図版あり
内容記述（英）
Physical characteristics: Original contains color illustrations
Anomaly of Hydrogen Recombination Line Ratio in Ultraluminous Infrared Galaxies
AA1730026077.pdf
(278.51KB)
