Testing $Lambda$CDM With Dwarf Galaxy Morphology. (arXiv:1904.08949v1 [astro-ph.GA])

Testing $Lambda$CDM With Dwarf Galaxy Morphology. (arXiv:1904.08949v1 [astro-ph.GA])
<a href="http://arxiv.org/find/astro-ph/1/au:+Xu_W/0/1/0/all/0/1">Weishuang Linda Xu</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Randall_L/0/1/0/all/0/1">Lisa Randall</a>

The leading tensions to the collisionless cold dark matter (CDM) paradigm are
the “small-scale controversies”, discrepancies between observations at the
dwarf-galactic scale and their simulational counterparts. In this work we
consider methods to infer 3D morphological information on Local Group dwarf
spheroidals, and test the fitness of CDM+hydrodynamics simulations to the
observed galaxy shapes. We find that the subpopulation of dwarf galaxies with
mass-to-light ratio $gtrsim 100 M_odot/L_odot$ reflects an oblate
morphology. This is discrepant with the dwarf galaxies with mass-to-light ratio
$lesssim 100 M_odot/L_odot$, which reflect prolate morphologies, and more
importantly with simulations of CDM-sourced galaxies which are explicitly
prolate. Although more simulations and data are called for, if evidence of
oblate pressure-supported stellar distributions persists, we argue that an
underlying oblate non-CDM dark matter halo may be required, and present this as
motivation for future studies.

The leading tensions to the collisionless cold dark matter (CDM) paradigm are
the “small-scale controversies”, discrepancies between observations at the
dwarf-galactic scale and their simulational counterparts. In this work we
consider methods to infer 3D morphological information on Local Group dwarf
spheroidals, and test the fitness of CDM+hydrodynamics simulations to the
observed galaxy shapes. We find that the subpopulation of dwarf galaxies with
mass-to-light ratio $gtrsim 100 M_odot/L_odot$ reflects an oblate
morphology. This is discrepant with the dwarf galaxies with mass-to-light ratio
$lesssim 100 M_odot/L_odot$, which reflect prolate morphologies, and more
importantly with simulations of CDM-sourced galaxies which are explicitly
prolate. Although more simulations and data are called for, if evidence of
oblate pressure-supported stellar distributions persists, we argue that an
underlying oblate non-CDM dark matter halo may be required, and present this as
motivation for future studies.

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