Central dark matter content of dwarf galaxies
Kyle Oman | 29 May 2020
Dwarf galaxies typically have very low stellar and gas densities, such that even in their centres the local dark matter density exceeds that of ordinary matter. The dark matter is therefore the primary driver of the dynamics of such systems, making them ideal laboratories to investigate the detailed internal dark matter distribution of galaxies. There is a long-standing debate over whether the central density of dwarfs is compatible with galaxy formation in the fiducial ΛCDM cosmology. While making a measurement of the central density is conceptually straightforward, in practice there are many possible pitfalls and caveats which must be understood...
read moreStrong lensing constraints on the dark matter mass through a forward-modelling procedure
Qiuhan He | 26 May 2020
Introduction Cold and warm dark matter models predict significantly different numbers of dark matter haloes with masses less than ~ 10\(^{-1}\) Msun, which are mostly too small to have a luminous galaxy living in their centres and thus cannot be directly ‘‘seen’’ in the Universe. To visualize those small haloes, strong gravitational lensing is a powerful tool. Light-rays coming from a far background galaxy will not only be deflected by a massive foreground galaxy, but also be perturbed by small haloes happening to fall on the light paths. By studying tiny footprints from small haloes hidden in strong lensing images,...
read moreCompact groups of galaxies
Sylvia Ploeckinger | 20 May 2020
Galaxy interaction critically depend on the presence (or absence) of dark matter. If each galaxy is embedded in a massive dark matter halo, the additional mass of the system leads to a faster merging process. In alternative theories - without dark matter - the individual galaxies can be in each others proximity for longer without merging into one massive galaxy. Comparing the abundance of compact groups of galaxies in a cosmological dark matter simulation with the observed abundance therefore serves as a test for the dark matter paradigm.
read moreThe detailed gaseous structure and the onset of galaxy formation in low-mass dark matter halos
Alejandro Benitez-Llambay | 18 May 2020
The Λ-cold dark matter (ΛCDM) cosmological model makes specific and robust predictions for the growth, structure and abundance of dark matter haloes, the sites where galaxies form. These are: (i) dark matter haloes grow hierarchically: small haloes form first and larger haloes form subsequently by mergers of smaller haloes; (ii) the internal structure of dark matter haloes is self-similar; (iii) the number density of haloes per unit mass rises steeply towards low masses, implying that a large fraction of low-mass haloes must fail to form a galaxy and remain dark at redshift z=0 if ΛCDM is to be reconciled with...
read moreThe dark matter component of the Gaia radially anisotropic substructure
Nassim Bozorgnia | 18 May 2020
The local dark matter distribution is a crucial input in the analysis of results from dark matter direct detection experiments. The commonly adopted model for the dark matter halo of our Galaxy is the Standard Halo Model, in which the halo is assumed to be isothermal and the dark matter velocity distribution is an isotropic Maxwellian distribution. However, the true local dark matter distribution may be different from a Maxwellian distribution. State-of-the-art cosmoligical simulations together with recent astronomical data can provide us with important information on the local dark matter distribution.
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