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تسجيل مستخدم جديدOn the persistence of two small-scale problems in {Lambda}CDM
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We investigate the degree to which the inclusion of baryonic physics can overcome two long-standing problems of the standard cosmological model on galaxy scales: (i) the problem of satellite planes around Local Group galaxies, and (ii) the too big to fail problem. By comparing dissipational and dissipationless simulations, we find no indication that the addition of baryonic physics results in more flattened satellite distributions around Milky-Way-like systems. Recent claims to the contrary are shown to derive in part from a non-standard metric for the degree of flattening, which ignores the satellites radial positions. If the full 3D positions of the satellite galaxies are considered, none of the simulations we analyse reproduce the observed flattening nor the observed degree of kinematic coherence of the Milky Way satellite system. Our results are consistent with the expectation that baryonic physics should have little or no influence on the structure of satellite systems on scales of hundreds of kiloparsecs. Claims that the too big to fail problem can be resolved by the addition of baryonic physics are also shown to be problematic.
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The dark energy plus cold dark matter ($Lambda$CDM) cosmological model has been a demonstrably successful framework for predicting and explaining the large-scale structure of Universe and its evolution with time. Yet on length scales smaller than $si
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The dwarf galaxy NGC 3109 is receding 105 km/s faster than expected in a $Lambda$CDM timing argument analysis of the Local Group and external galaxy groups within 8 Mpc (Banik & Zhao 2018). If this few-body model accurately represents long-range inte
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