Robust estimate of dark halo structures in the Galactic dwarf galaxies toward the future dark matter indirect detections

• Project Area: Why does the Universe accelerate? - Exhaustive study and challenge for the future -
• Project/Area Number: 18H04359
• Research Category: Grant-in-Aid for Scientific Research on Innovative Areas (Research in a proposed research area)
• Allocation Type: Single-year Grants
• Research Institution: The University of Tokyo
• Principal Investigator: 林 航平 東京大学, 宇宙線研究所, 特別研究員 (20771207)
• Project Period (FY): 2018-04-01 – 2020-03-31
• Project Status: Completed (Fiscal Year 2019)
• Budget Amount: ¥4,030,000 (Direct Cost: ¥3,100,000、Indirect Cost: ¥930,000); Fiscal Year 2019: ¥1,820,000 (Direct Cost: ¥1,400,000、Indirect Cost: ¥420,000); Fiscal Year 2018: ¥2,210,000 (Direct Cost: ¥1,700,000、Indirect Cost: ¥510,000)
• Keywords: 暗黒物質 / 間接的探査 / Ultralight dark matter / 矮小銀河 / 銀河系矮小楕円体銀河 / すばる超広視野多天体分光器 / チェレンコフ望遠鏡アレイ / すばる広視野多天体分光器

Outline of Annual Research Achievements

暗黒物質は宇宙を構成する物質のうち８割を占めるが、その正体は未だ謎のままであり、現代の宇宙物理学および素粒子物理学において最大の問題の１つである。素粒子物理学の側面からこの暗黒物質に対する理論模型が数多く提唱されている。各模型の性質の違いが現れるのは主に非線形領域であるため、その領域に対応する銀河を用いた理論模型への制限が行われている。銀河系矮小銀河は暗黒物質が豊富な系であるため、この研究に最適な天体であるとされている。
本研究では、暗黒物質模型の１つであるultralight dark matterについて矮小銀河の非球対称性を考慮した解析を行い、その制限を行った。その結果、いくつかの矮小銀河でダークマターハローが非常に潰れた形状でなければ観測データを再現できないことが明らかになった。この形状はultralight dark matterでは再現できないほど潰れており、この理論模型の大きな問題点を指摘することができた。
一方で、銀河系矮小銀河はガンマ線を用いたダークマター探査にも最適な天体である。これを用いたダークマター模型の制限には矮小銀河ダークマター分布を反映したJ-factorという量を精度良く決定することが必要不可欠である。しかし、データに含まれるコンタミネーションやサンプリングバイアスによる影響が無視できないことが指摘されている。本研究ではこの影響を統計的に考慮した解析モデルを構築した。このモデルを実際の矮小銀河データに適用し、より信頼度の高いJ-factor値を推定することが出来た。これは次世代分光観測装置すばるPFSによる分光観測によってデータ数が増えるとより高精度決定が可能になり、チェレンコフ望遠鏡アレイを用いたダークマター模型の制限もより厳しくなることが期待される結果である。

Research Progress Status

令和元年度が最終年度であるため、記入しない。

Strategy for Future Research Activity

令和元年度が最終年度であるため、記入しない。

Research Products

• [Int'l Joint Research] ジョンズ・ホプキンス大学/カリフォルニア工科大学(米国)
• [Int'l Joint Research] 中国科学院国家天文台(中国)
• [Int'l Joint Research] カリフォルニア工科大学/ジョンズ・ホプキンス大学(米国)
• [Int'l Joint Research] 中国科学院国家天文台(中国)
• [Int'l Joint Research] Osservatorio Astronomico di Roma(イタリア)
• [Int'l Joint Research] Nicolaus Copernicus Astronomical Center(ポーランド)
• [Journal Article] J-factor estimation of Draco, Sculptor and Ursa Minor dwarf spheroidal galaxies with the member/foreground mixture model (2020)
  • Author(s): S. Horigome, K. Hayashi, M. Ibe, M N. Ishigaki, S. Matsumoto, and H. Sugai
  • Journal Title: Astro-ph Volume: －
  • NAID: 130008157053
  • Open Access
• [Journal Article] Non-sphericity of ultralight-axion dark matter haloes in the Galactic dwarf spheroidal galaxies (2020)
  • Author(s): K. Hayashi, and I. Obata
  • Journal Title: Monthly Notices of the Royal Astronomical Society Volume: 491 Pages: 615-633
  • DOI: 10.1093/mnras/stz2950
  • Peer Reviewed / Open Access
• [Journal Article] Constraining dark matter annihilation with HSC low surface brightness galaxies (2020)
  • Author(s): Hashimoto Daiki、Macias Oscar、Nishizawa Atsushi J.、Hayashi Kohei、Takada Masahiro、Shirasaki Masato、Ando Shin'ichiro
  • Journal Title: Journal of Cosmology and Astroparticle Physics Volume: 2020 Issue: 01 Pages: 059-059
  • DOI: 10.1088/1475-7516/2020/01/059
  • Peer Reviewed / Open Access / Int'l Joint Research
• [Journal Article] Botes. IV. A new Milky Way satellite discovered in the Subaru Hyper Suprime-Cam Survey and implications for the missing satellite problem (2019)
  • Author(s): Homma Daisuke、Chiba Masashi、Komiyama Yutaka、Tanaka Masayuki、Okamoto Sakurako、Tanaka Mikito、Ishigaki Miho N、Hayashi Kohei、Arimoto Nobuo、Carlsten Scott G、Lupton Robert H、Strauss Michael A、Miyazaki Satoshi、Torrealba Gabriel、Wang Shiang-Yu、Murayama Hitoshi
  • Journal Title: Publications of the Astronomical Society of Japan Volume: 71 Issue: 5 Pages: 1-13
  • DOI: 10.1093/pasj/psz076
  • Peer Reviewed / Open Access / Int'l Joint Research
• [Journal Article] The stellar halo of the Milky Way traced by blue horizontal-branch stars in the Subaru Hyper Suprime-Cam Survey (2019)
  • Author(s): Fukushima Tetsuya、Chiba Masashi、Tanaka Mikito、Hayashi Kohei、Homma Daisuke、Okamoto Sakurako、Komiyama Yutaka、Tanaka Masayuki、Arimoto Nobuo、Matsuno Tadafumi
  • Journal Title: Publications of the Astronomical Society of Japan Volume: 71 Issue: 4 Pages: 1-16
  • DOI: 10.1093/pasj/psz052
  • Peer Reviewed / Open Access / Int'l Joint Research
• [Journal Article] Non-sphericity of ultra-light axion dark matter halos in the Galactic dwarf spheroidal galaxies (2019)
  • Author(s): Hayashi Kohei、Ippei Obata
  • Journal Title: Monthly Notices of the Royal Astronomical Society Volume: －
  • Open Access
• [Journal Article] Effects of mass models on dynamical mass estimate: the case of ultradiffuse galaxy NGC 1052-DF2 (2018)
  • Author(s): Hayashi Kohei、Inoue Shigeki
  • Journal Title: Monthly Notices of the Royal Astronomical Society: Letters Volume: 481 Issue: 1 Pages: L59-L63
  • DOI: 10.1093/mnrasl/sly162
  • Peer Reviewed
• [Journal Article] Dark halo structure in the Carina dwarf spheroidal galaxy: joint analysis of multiple stellar components (2018)
  • Author(s): Hayashi Kohei、Fabrizio Michele、Lokas Ewa L、Bono Giuseppe、Monelli Matteo、Dall’Ora Massimo、Stetson Peter B
  • Journal Title: Monthly Notices of the Royal Astronomical Society Volume: 481 Issue: 1 Pages: 250-261
  • DOI: 10.1093/mnras/sty2296
  • Peer Reviewed / Int'l Joint Research
• [Journal Article] The Missing Satellite Problem Outside of the Local Group. I. Pilot Observation (2018)
  • Author(s): Tanaka Masayuki、Chiba Masashi、Hayashi Kohei、Komiyama Yutaka、Okamoto Takashi、Cooper Andrew P.、Okamoto Sakurako、Spitler Lee
  • Journal Title: The Astrophysical Journal Volume: 865 Issue: 2 Pages: 125-125
  • DOI: 10.3847/1538-4357/aad9fe
  • Peer Reviewed / Open Access / Int'l Joint Research
• [Journal Article] Foreground effect on the J-factor estimation of ultrafaint dwarf spheroidal galaxies (2018)
  • Author(s): Ichikawa, K., Horigome, S., Ishigaki, M. N., Matsumoto, S., Ibe, M., Sugai, H., Hayashi, K.
  • Journal Title: Monthly Notices of the Royal Astronomical Society Volume: 479 Issue: 1 Pages: 64-74
  • DOI: 10.1093/mnras/sty1387
  • NAID: 130008148664
  • Peer Reviewed / Open Access / Int'l Joint Research
• [Presentation] Galactic Archaeology: Unveiling the nature of dark matter (2020)
  • Author(s): 林航平
  • Organizer: Berkeley Week
• [Presentation] Milky Way science with HSC Northern-hemisphere Ultra Wide Survey (2020)
  • Author(s): 林航平
  • Organizer: Euclid衛星とすばる望遠鏡のシナジー
  • Invited
• [Presentation] 銀河系矮小銀河を用いたultra-light axion dark matterへの制限 (2020)
  • Author(s): 林航平
  • Organizer: 日本天文学会2020年春季年会
• [Presentation] Diversity of the central dark matter densities in the Galactic dwarf spheroidals (2020)
  • Author(s): 林航平
  • Organizer: Cosmic Acceleration
  • Int'l Joint Research
• [Presentation] Pseudo phase space density of dark matter halos in the dwarf spheroidals (2019)
  • Author(s): 林航平
  • Organizer: 6th Galaxy Evolution Workshop
• [Presentation] PFS, WFIRST, CTAのシナジーで迫る銀河系矮小銀河ダークマター研究の将来展望 (2019)
  • Author(s): 林航平
  • Organizer: 我が国の（近）赤外線広視野観測サイエンスの戦略と展望
• [Presentation] 銀河系矮小銀河コアカスプ問題の再検討 (2019)
  • Author(s): 林航平
  • Organizer: 第８回観測的宇宙論ワークショップ
• [Presentation] Ultralight axion dark matter and small-scale problem (2019)
  • Author(s): 林航平
  • Organizer: Two-day workshop: Axion Cosmology
  • Int'l Joint Research / Invited
• [Presentation] Dark matter distributions in the Galactic dwarf spheroidal galaxies (2019)
  • Author(s): 林航平
  • Organizer: Topics in Astroparticle and Underground Physics (TAUP) 2019
  • Int'l Joint Research
• [Presentation] Diversity of dark matter distributions in the Galactic dwarf satellites (2019)
  • Author(s): 林航平
  • Organizer: Subaru International Conference “Subaru Telescope 20th Anniversary”
  • Int'l Joint Research
• [Presentation] Dark matter in dwarf galaxies in the Subaru-PFS era (2019)
  • Author(s): 林航平
  • Organizer: Subaru International Conference “Subaru Telescope 20th Anniversary”
  • Int'l Joint Research
• [Presentation] Dark matter density profiles in the classical dwarf spheroidal galaxies in Milky Way (2019)
  • Author(s): 林航平
  • Organizer: 新学術シンポジウム「なぜ宇宙は加速するのか？-徹底的究明と将来への挑戦-」
• [Presentation] Non-sphericity of ultralight axion dark matter halos in the Galactic dwarf satellites (2019)
  • Author(s): 林航平
  • Organizer: Accelerating Universe in the Dark
  • Int'l Joint Research
• [Presentation] 銀河系矮小銀河の観測的不定性を考慮した暗黒物質分布推定 (2018)
  • Author(s): 林航平
  • Organizer: 日本天文学会２０１８年秋季年会
• [Presentation] Dark halo structures and star formation histories of the Galactic dwarf spheroidals (2018)
  • Author(s): 林航平
  • Organizer: Workshop in Galactic Archaeology with LAMOST and Subaru
• [Presentation] The universal dark halo scaling relation for the dwarf satellites (2018)
  • Author(s): 林航平
  • Organizer: 第５回銀河進化研究会
• [Presentation] Effects of mass models on dynamical mass estimate: the case for ultra diffuse galaxy NGC1052-DF2 (2018)
  • Author(s): 林航平
  • Organizer: 日本天文学会２０１８年秋季年会
• [Presentation] Universal dark halo scaling relation for the dwarf spheroidal galaxies (2018)
  • Author(s): 林航平
  • Organizer: The 8th KIAS workshop on cosmology and structure formation
  • Int'l Joint Research / Invited
• [Presentation] PFS survey simulations for GA targets (2018)
  • Author(s): 林航平
  • Organizer: The PFS 10th General Collaboration Meeting
  • Int'l Joint Research
• [Presentation] Update on the PFS-DSPH (2018)
  • Author(s): 林航平
  • Organizer: PFS Science Working Group meeting
  • Int'l Joint Research
• [Presentation] Robust estimate of dark matter distributions in the Galactic dwarf spheroidals (2018)
  • Author(s): 林航平
  • Organizer: TeV Particle Astrophysics 2018
  • Int'l Joint Research
• [Funded Workshop] Dark Matter Searches in the 2020s - At the crossroads of WIMP (2019)