Hollow cores in warm dark matter halos from the Vlasov-Poisson equation

Abstract

We report the results of extended high-resolution numerical integrations of the Vlasov-Poisson equation for the collapse of spherically symmetric WDM halos. For thermal relics with mass m = 1 keV/c 2 , we find collapsed halos with cores of size from 0.1 to 0.6 kpc. The typical core is hollow, with the mass density decreasing towards the core center by almost three orders of magnitude from its maximum near the core radius rc. The core is in equilibrium with the diffused part of the halo but far from virialization. These properties are rooted in the conservation of the squared angular momentum and in the original excess, proper of WDM initial conditions, of kinetic energy in the core region. In a sample of more than one hundred simulated collapses, the values of rc and of the core density ρc are in the range typical of dwarf spheroids, while the maximal circular velocities Vmax are proper of small disk galaxies. The product µc = ρcrc takes values between 116 M /pc 2 and 283 M /pc 2 , while the surface density µ0, as determined from a Burkert fit, is roughly three times larger. From these data and data obtained at smaller values of m, we extrapolate for one particular halo µc = 263(308) M /pc 2 and µ0 = 754(855) M /pc 2 at m = 2(3.3) keV/c 2 , to be compared with the observed value 1402 . In view of the many improvements and enhancements available, we conclude that WDM is a viable solution for explaining the presence and the size of cores in low mass galaxies.

Warm dark matter signatures on the 21cm power spectrum: intensity mapping forecasts for SKA

“…x we can also infer that most of the hydrogen in the intergalactic medium is ionised, and the neutral hydrogen is mainly contained in the so called damped Lyman-α absorber systems (DLAs) with HI column densities N HI above 2 × 10 20 atoms cm −2 and secondarily in Lyman limit systems (LLS), at 19 Figure 5. HI column density distribution function, f HI (N HI ), obtained by assigning HI to gas particles employing two different methods: halo based (dotted lines) and particle based (solid lines) described in 3.1 3.2.…”

“…However, there is also a possible way to alleviate at least some small scales problems, while preserving the success of CDM on large scales, by assuming that the dark matter JCAP07(2015)047 particles have intrinsic thermal velocities (although there are works that disagree, see for example [13,14]). On one hand, the presence of thermal velocities will avoid the cuspy clustering of dark matter particles within gravitational potential wells, allowing the formation of cores [15][16][17][18][19] in the density profile, although most of the works have shown that an unrealistic low value of the WDM mass is needed to match observations. On the other hand, the collapse of dark matter halos can only take place for perturbations larger than the typical free-streaming length of the dark matter particles, thus, the presence of thermal velocities in the dark matter particles will naturally suppress the abundance of low mass subhalos [20][21][22].…”

The SLUGGS survey: multipopulation dynamical modelling of the elliptical galaxy NGC 1407 from stars and globular clusters

“…The prior on γ was chosen to be positive for consistency with similar studies (e.g., Barnabè et al 2012;Cappellari et al 2013;Adams et al 2014) and because inner DM depression with γ < 0 is a regime not yet explored by numerical simulations, with a few exceptions (e.g., Destri 2014).…”

“…The prior on the stellar mass-to-light ratio includes the values predicted by stellar population models for NGC 1407 (Zhang et al 2007;Humphrey et al 2006) The prior on γ was chosen to be positive for consistency with similar studies (e.g., Barnabè et al 2012;Cappellari et al 2013;Adams et al 2014) and because inner DM depression with γ < 0 is a regime not yet explored by numerical simulations, with a few exceptions (e.g., Destri 2014).…”

Stellar Profile Independent Determination of the Dark Matter Distribution of the Fornax Local Group Dwarf Spheroidal Galaxy

“…The 'core-cusp' problem may evince DM properties beyond the CDM paradigm. McDonald & Sahu (2009); Angulo et al (2013); Destri (2014); González-Samaniego et al (2016) argue that DM particles would be less prone to forming cusped halos if primordial DM either remained relativistic for longer or decoupled later than canonically predicted. Rocha et al (2013); Peter et al (2013); Robles et al (2017); Sokolenko et al (2018); Harvey et al (2018); Robertson et al (2019); Sameie et al (2018); Fitts et al (2019); Robles et al (2019) claim that self-interacting dark matter (SIDM) could virialize dense DM cusps, turning them into a cores.…”