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サトウ コウスケ
SATO KOSUKE
佐藤 浩介 所属 京都産業大学 理学部 宇宙物理・気象学科 職種 教授 |
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| 言語種別 | 英語 |
| 発行・発表の年月 | 2022/10 |
| 形態種別 | 研究論文 |
| 査読 | 査読あり |
| 標題 | The soft X-ray background with Suzaku. I. Milky Way halo |
| 執筆形態 | 共著 |
| 掲載誌名 | Publications of the Astronomical Society of Japan |
| 掲載区分 | 国外 |
| 出版社・発行元 | Oxford University Press (OUP) |
| 巻・号・頁 | 74(6),pp.1396-1414 |
| 著者・共著者 | Masaki Ueda,Hayato Sugiyama,Shogo B Kobayashi,Kotaro Fukushima,Noriko Y Yamasaki,Kosuke Sato,Kyoko Matsushita |
| 概要 | Abstract
We present measurements of the soft X-ray background emission for 130 Suzaku observations at 75° < l < 285° and |b| > 15° obtained from 2005 to 2015, covering nearly one solar cycle. In addition to the standard soft X-ray background model consisting of the local hot bubble and the Milky Way Halo (MWH), we include a hot collisional-ionization-equilibrium component with a temperature of ∼0.8 keV to reproduce spectra of a significant fraction of the lines of sight. Then, the scatter in the relation between the emission measure vs. temperature of the MWH component is reduced. Here, we exclude time ranges with high count rates to minimize the effect of the solar wind charge exchange (SWCX). However, the spectra of almost the same lines of sight are inconsistent. The heliospheric SWCX emissions likely contaminate and give a bias in measurements of temperature and the emission measure of the MWH. Excluding the data around the solar maximum and using the data taken before the end of 2009, at |b| > 35° and 105° < l < 255°, the temperature (0.22 keV) and emission measure (2 × 10−3 cm−6 pc) of the MWH are fairly uniform. The increase of the emission measure toward the lower Galactic latitude at |b| < 35° indicates the presence of a disk-like morphology component. A composite model which consists of disk-like and spherical-morphology components also reproduces the observed emission measure distribution of MWH. In this case, the hydrostatic mass at a few tens of kiloparsec from the Galactic center agrees with the gravitational mass of the Milky Way. The plasma with the virial temperature likely fills the Milky Way halo in nearly hydrostatic equilibrium. Assuming a gas metallicity of 0.3 solar, the upper limit of the gas mass of the spherical component out to 250 kpc, or the virial radius, is ∼ a few × 1010 M⊙. |
| DOI | 10.1093/pasj/psac077 |
| ISSN | 0004-6264/2053-051X |
| PermalinkURL | https://academic.oup.com/pasj/article-pdf/74/6/1396/47470916/psac077.pdf |