{"id":10015,"date":"2021-02-18T16:12:24","date_gmt":"2021-02-18T07:12:24","guid":{"rendered":"https:\/\/www.icrr.u-tokyo.ac.jp\/?post_type=news&p=10015"},"modified":"2021-02-18T16:12:24","modified_gmt":"2021-02-18T07:12:24","slug":"%e3%80%90%e3%83%97%e3%83%ac%e3%82%b9%e3%83%aa%e3%83%aa%e3%83%bc%e3%82%b9%e3%80%91%e3%83%80%e3%83%bc%e3%82%af%e3%83%9e%e3%82%bf%e3%83%bc%e3%81%af%e3%80%8c%e5%af%86%e3%80%8d%e3%81%ab%e3%81%aa%e3%82%8a-2","status":"publish","type":"news","link":"https:\/\/www.icrr.u-tokyo.ac.jp\/en\/news\/10015\/","title":{"rendered":"\u3010Press Release\u3011The Smallest Galaxies in Our Universe Bring More About Dark Matter to Light"},"content":{"rendered":"\n

Graduate School of Science,Tohoku University
Institute for Cosmic Ray Research(ICRR),The University of Tokyo
Kavli Institute for the Physics and Mathematics of the Universe(Kavli IPMU),The University of Tokyo
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Our universe is dominated by a mysterious matter known as dark matter. Its name comes from the fact that dark matter does not absorb, reflect or emit electromagnetic radiation, making it difficult to detect.  <\/p>\n\n\n\n

Now, a team of researchers has investigated the strength of dark matter scattered across the smallest galaxies in the universe using stellar kinematics.<\/p>\n\n\n\n

\u201cWe discovered that the strength of dark matter is quite small, suggesting that dark matter does not easily scatter together,\u201d said professor Kohei Hayashi, lead author of the study.<\/p>\n\n\n\n

Much is unknown about dark matter, but theoretical and experimental research, from particle physics to astronomy, are elucidating more about it little by little.<\/p>\n\n\n\n

One prominent theory surrounding dark matter is the \u201cself-interacting dark matter (SIDM) theory.\u201d It purports that dark matter distributions in galactic centers become less dense because of the self-scattering of dark matter. <\/p>\n\n\n\n

However, supernova explosions, which occur toward the end of a massive star\u2019s life, can also form less dense distributions. This makes it challenging to distinguish whether it is the supernova explosion or the nature of dark matter that causes a less dense distribution of dark matter.<\/p>\n\n\n\n

To clarify this, Hayashi and his team focused on ultra-faint dwarf galaxies. Here a few stars exist, rendering the influences of supernova explosions negligible.<\/p>\n\n\n\n

Their findings showed that dark matter is dense at the center of the galaxy, challenging the basic premise of SIDM. Images from the dwarf galaxy Segue 1 revealed high dark matter density at the center of the galaxy, and that scattering is limited. \u201cOur study showed how useful stellar kinematics in ultra-faint dwarf galaxies are for testing existing theories on dark matter,\u201d noted Hayashi. \u201cFurther observations using next-generation wide-field spectroscopic surveys with the Subaru Prime Focus Spectrograph, will maximize the chance of obtaining dark matter\u2019s smoking gun.\u201d<\/p>\n\n\n\n

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Fig.1: Dark matter distributions. The redder colored regions show high dark matter density regions. The left panel shows the case that dark matter distribution becomes high dense in the center of a galaxy, while right one show less dense dark matter distribution predicted by self-interacting dark matter theory. Segue1 prefers high dark matter density like that the left panel. Copyright: Kohei HAYASHI<\/figcaption><\/figure>\n\n\n\n
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Fig.2: The strength of dark matter scattering (y-axis) versus the averaged relative velocity between dark matter and itself (x-axis). The points with error bars come from other galaxies estimated by previous studies. The red shaded region shows the result from Segue 1 ultra-faint dwarf galaxy. Copyright: HAYASHI et al.<\/figcaption><\/figure>\n\n\n\n

\uff1cPublication Detail\uff1e<\/strong>
Title:<\/strong> \u201cProbing Dark Matter Self-interaction with Ultra-faint Dwarf Galaxies\u201d
Authors: <\/strong>Kohei Hayashi, Masahiro Ibe, Shin Kobayashi, Yuhei Nakayama,\u3000Satoshi Shirai
Journal: <\/strong>Physical Review <\/em>
DOI\uff1a<\/strong>10.1103\/PhysRevD.103.023017
URL\uff1a<\/strong>https:\/\/journals.aps.org\/prd\/abstract\/10.1103\/PhysRevD.103.023017<\/p>\n\n\n\n

\u3010Web Link\u3011<\/strong><\/p>\n\n\n\n

\u25b7Tohoku University<\/a>, Graduate School of Science, Tohoku University<\/a>

<\/p>\n","protected":false},"excerpt":{"rendered":"

Graduate School of Science,Tohoku UniversityInstitute for Cosmic Ray Research(ICRR),The University of TokyoKav…<\/p>\n","protected":false},"featured_media":9959,"parent":0,"template":"","taxo_news":[21],"tag_news":[],"class_list":["post-10015","news","type-news","status-publish","has-post-thumbnail","hentry","taxo_news-press-releases","en-US"],"aioseo_notices":[],"aioseo_head":"\n\t\t\n\t\n\t\n\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t