UCI天文学者のシミュレーションが暗黒物質の存在を支持する(UC Irvine astronomers’ simulations support dark matter theory)

ad

2024-04-29 カリフォルニア大学校アーバイン校(UCI)

カリフォルニア大学アーバイン校を含む研究者たちは、暗黒物質（直接検出されていないが、宇宙の多くの側面を説明するために存在すると多くの物理学者が考えている物質）の存在を支持するコンピュータシミュレーションを行いました。この研究は、宇宙の仕組みを説明するために見えない暗黒物質が必要か、または直接観測可能な物質のみで物理学者が説明できるかという基本的な議論に取り組んでいます。シミュレーション結果は、実際の銀河で測定された特徴を説明し、これらの特徴が暗黒物質モデルを支持することを示しています。

＜関連情報＞

ダークマターとMONDの識別テスト：半径加速度関係におけるフックとベンド Hooks & Bends in the radial acceleration relation: discriminatory tests for dark matter and MOND

Francisco J Mercado, James S Bullock, Jorge Moreno, Michael Boylan-Kolchin, Philip F Hopkins, Andrew Wetzel, Claude-André Faucher-Giguère, Jenna Samuel
Monthly Notices of the Royal Astronomical Society  Published:16 April 2024
DOI:https://doi.org/10.1093/mnras/stae819

Schematic examples: a standard RAR and a downward hook. The upper and lower panels show simple examples of how spherically-symmetric 3D density profiles (left) of total mass distributions (magenta) and baryonic mass distributions (cyan) map to radial acceleration profiles (middle) and ultimately to the RAR (right). Each panel assumes a log–log axis scaling. The dashed grey arrow in the middle and right-hand panels is pointed in the direction of decreasing radius. In the upper panels, we assume a baryon-dominated, inner cuspy profile, and this produces a standard-type RAR relation (upper right). In the lower set of figures, we assume a dark-matter-dominated inner mass profile, with a cored density distribution. This assumption gives rise to an RAR profile with a downward hook of the type shown for real galaxies in Fig. 6 and simulated galaxies in Fig. 2. See the end of Section 2 for a more detailed description. Takeaway: Reasonable assumptions for the density makeup of baryon-dominated galaxies allow us to understand the observed average scaling of the RAR in a natural way (top); these expectations break down for dark-matter dominated galaxies with cored inner dark matter density profiles, which should often deviate from the average scaling (bottom).

ABSTRACT

The radial acceleration relation (RAR) connects the total gravitational acceleration of a galaxy at a given radius, atot(r), with that accounted for by baryons at the same radius, abar(r). The shape and tightness of the RAR for rotationally-supported galaxies have characteristics in line with MOdified Newtonian Dynamics (MOND) and can also arise within the cosmological constant + cold dark matter (ΛCDM) paradigm. We use zoom simulations of 20 galaxies with stellar masses of M⋆ ≃ 107–11 M⊙ to study the RAR in the FIRE-2 simulations. We highlight the existence of simulated galaxies with non-monotonic RAR tracks that ‘hook’ down from the average relation. These hooks are challenging to explain in Modified Inertia theories of MOND, but naturally arise in all of our ΛCDM-simulated galaxies that are dark-matter dominated at small radii and have feedback-induced cores in their dark matter haloes. We show, analytically and numerically, that downward hooks are expected in such cored haloes because they have non-monotonic acceleration profiles. We also extend the relation to accelerations below those traced by disc galaxy rotation curves. In this regime, our simulations exhibit ‘bends’ off of the MOND-inspired extrapolation of the RAR, which, at large radii, approach atot ≈ abar/fb, where fb is the cosmic baryon fraction. Future efforts to search for these hooks and bends in real galaxies will provide interesting tests for MOND and ΛCDM.

ad
1701物理及び化学
暗黒物質
ad
ad


Share
Follow
ad
テック・アイ技術情報研究所
ad
ソーダストリーム TERRA(テラ) スターターキット
created by Rinker
タイトルとURLをコピーしました