Giant cold satellites from low-concentration haloes. (arXiv:1901.05460v1 [astro-ph.GA])
<a href="http://arxiv.org/find/astro-ph/1/au:+Amorisco_N/0/1/0/all/0/1">Nicola C. Amorisco</a>
The dwarf satellite galaxies of the Milky Way Crater II and Antlia II have
uncommonly low dynamical mass densities, due to their large size and low
velocity dispersion. Previous work have failed to identify formation scenarios
within the $Lambda$CDM framework and have invoked cored dark matter haloes,
processed by tides. I show that the tidal evolution of $Lambda$CDM NFW haloes
is richer than previously recognised: tidal heating causes the innermost
regions of haloes that fall short of the mass-concentration relation to expand
significantly, resulting in the formation of giant, kinematically cold
satellites like Crater II and Antlia II. Furthermore, while the satellite is
reaching apocenter, extra-tidal material can cause an even more inflated
appearance. When present, as likely for the larger Antlia II, nominally unbound
material can be recognised thanks to its somewhat hotter kinematics and
line-of-sight velocity gradient. Contrary to other formation scenarios, Crater
II and Antlia II may well have experienced very little mass loss, as in fact
hinted by their observed metallicity. If indeed a satellite of NGC1052, tidal
evolution of a low-concentration halo may similarly have led to the formation
of NGC1052-DF2.
The dwarf satellite galaxies of the Milky Way Crater II and Antlia II have
uncommonly low dynamical mass densities, due to their large size and low
velocity dispersion. Previous work have failed to identify formation scenarios
within the $Lambda$CDM framework and have invoked cored dark matter haloes,
processed by tides. I show that the tidal evolution of $Lambda$CDM NFW haloes
is richer than previously recognised: tidal heating causes the innermost
regions of haloes that fall short of the mass-concentration relation to expand
significantly, resulting in the formation of giant, kinematically cold
satellites like Crater II and Antlia II. Furthermore, while the satellite is
reaching apocenter, extra-tidal material can cause an even more inflated
appearance. When present, as likely for the larger Antlia II, nominally unbound
material can be recognised thanks to its somewhat hotter kinematics and
line-of-sight velocity gradient. Contrary to other formation scenarios, Crater
II and Antlia II may well have experienced very little mass loss, as in fact
hinted by their observed metallicity. If indeed a satellite of NGC1052, tidal
evolution of a low-concentration halo may similarly have led to the formation
of NGC1052-DF2.
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