“NGC1052-DF2”的版本间差异
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*号称没有暗物质的星系, [[ultra diffuse galaxy]] [https://arxiv.org/abs/1803.10237] '''Nature March 2018''' [[文件:NGC1052-DF2.JPG|缩略图|HST/ACS image]] |
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*号称没有暗物质的星系 |
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==观测== |
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*如果有暗物质，这些球状星团系统受到暗物质的dynamic friction，会形成nuclear cluster[arXiv:1902.05959 ] |
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*S´ersic index n = 0.6, axis ratio b/a = 0.85, the central surface brightness is µ(V606,0) = 24.4magarcsec−2, D=20Mpc. |
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* effective radius along the major axis is Re = 2.2kpc, M606 = −15.4 mag, Mstars ≈ 2×10^8 Msun. |
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*an extraordinary population of globular clusters, larger and more luminous than average GCs in the Milky Way, total mass is roughly 4 percent of the mass in stars, making DF2 one of the galaxies with the largest specific frequencies known. |
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*the line-of-sight velocity dispersion of the GCs(10km/s) suggests a total dynamical mass for DF2 that leaves little room for any dark matter |
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==模型== |
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* [[https://arxiv.org/abs/1903.11612 | 1903.11612]] Nature 文章：动力学符合MOND |
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*测量误差很大，如果有些球状星团是背景，不能说得那么肯定 [https://arxiv.org/abs/1804.04136] |
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*如果没有暗物质，星系和球状星团质量的比靠近，动力学摩擦效应显著（时标1-2Gyr）,大部分星团团已经被并合了[https://arxiv.org/abs/1806.01812] |
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*考虑NGC1052的tidal效应，改变了DF2中球状星团在相空间的分布函数 （真实空间外围的GC少了，GC在速度空间的弥散小了） [https://arxiv.org/abs/1810.03864] |
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*没有暗物质的dynamical friction没那么简单, core-stalling and GC-GC interactions效应, 让星团掉不进去。反过来，如果有cuspy的NFW暗晕，里面的dynamical friction更强，会形成核心GC [https://arxiv.org/abs/1902.05959 ] |
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*MOND |
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:*不支持MOND，弱引力场（近似于有暗物质）[https://arxiv.org/abs/1804.04167] |
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:*你没考虑NGC1052作用，符合MOND！ [https://arxiv.org/abs/1903.11612] '''Nature March 2019''' |
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==结局== |
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*你们距离算错了 [https://arxiv.org/abs/1806.10141] |
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2020年10月18日 (日) 12:24的最新版本
- 号称没有暗物质的星系, ultra diffuse galaxy [1] Nature March 2018
观测
- S´ersic index n = 0.6, axis ratio b/a = 0.85, the central surface brightness is µ(V606,0) = 24.4magarcsec−2, D=20Mpc.
- effective radius along the major axis is Re = 2.2kpc, M606 = −15.4 mag, Mstars ≈ 2×10^8 Msun.
- an extraordinary population of globular clusters, larger and more luminous than average GCs in the Milky Way, total mass is roughly 4 percent of the mass in stars, making DF2 one of the galaxies with the largest specific frequencies known.
- the line-of-sight velocity dispersion of the GCs(10km/s) suggests a total dynamical mass for DF2 that leaves little room for any dark matter
- 气体含量非常低 [2] [3]
模型
- 测量误差很大，如果有些球状星团是背景，不能说得那么肯定 [4]
- 如果没有暗物质，星系和球状星团质量的比靠近，动力学摩擦效应显著（时标1-2Gyr）,大部分星团团已经被并合了[5]
- 考虑NGC1052的tidal效应，改变了DF2中球状星团在相空间的分布函数 （真实空间外围的GC少了，GC在速度空间的弥散小了） [6]
- 没有暗物质的dynamical friction没那么简单, core-stalling and GC-GC interactions效应, 让星团掉不进去。反过来，如果有cuspy的NFW暗晕，里面的dynamical friction更强，会形成核心GC [7]
- MOND
结局
- 你们距离算错了 [10]
- NGC1052-DF4， same group，第二个号称没有暗物质的星系 [11]（还是球状星团算的速度弥散度）