High-Resolution Simulation on Structure Formation with Extremely Light Bosonic Dark Matter

An alternative bosonic dark matter model is examined in detail via high-resolution simulations. These bosons have particle mass of order $10^{-22}eV$ and are non-interacting. If they do exist and can account for structure formation, these bosons must be condensed into the Bose-Einstein state and described by a coherent wave function. This matter, also known as Fuzzy Dark Matter (Hu, Barkana & Gruzinov 2000),, is speculated to be able, first, to eliminate the sub-galactic halos to solve the problem of over-abundance of dwarf galaxies, and, second, to produce flat halo cores in galaxies suggested by some observations. Our simulation results show that although this extremely light bosonic dark matter indeed suppresses low-mass halos, it can, to the contrary of expectation, yield singular halo cores. The density profile of the singular halo is almost identical to the halo profile of Navarro, Frenk & White (1997). Such a profile seems to be universal, in that it can be produced via either accretion or merger.Comment: 21 pages, 10 figure

The Case Against Warm or Self-Interacting Dark Matter as Explanations for Cores in Low Surface Brightness Galaxies

Warm dark matter (WDM) and self-interacting dark matter (SIDM) are often motivated by the inferred cores in the dark matter halos of low surface brightness (LSB) galaxies. We test thermal WDM, non-thermal WDM, and SIDM using high-resolution rotation curves of nine LSB galaxies. We fit these dark matter models to the data and determine the halo core radii and central densities. While the minimum core size in WDM models is predicted to decrease with halo mass, we find that the inferred core radii increase with halo mass and also cannot be explained with a single value of the primordial phase space density. Moreover, if the core size is set by WDM particle properties, then even the smallest cores we infer would require primordial phase space density values that are orders of magnitude smaller than lower limits obtained from the Lyman alpha forest power spectra. We also find that the dark matter halo core densities vary by a factor of about 30 from system to system while showing no systematic trend with the maximum rotation velocity of the galaxy. This strongly argues against the core size being directly set by large self-interactions (scattering or annihilation) of dark matter. We therefore conclude that the inferred cores do not provide motivation to prefer WDM or SIDM over other dark matter models.Comment: Accepted to ApJL; additions to Figs 3 and 4; minor changes to tex

Comparing the Dark Matter Halos of Spiral, Low Surface Brightness and Dwarf Spheroidal Galaxies

We consider dark masses measured from kinematic tracers at discrete radii in galaxies for which baryonic contributions to overall potentials are either subtracted or negligible. Recent work indicates that rotation curves due to dark matter (DM) halos at intermediate radii in spiral galaxies are remarkably similar, with a mean rotation curve given by $\log_{10}[V_{c,\mathrm{DM}}/(\mathrm{km s^{-1}})]=1.47_{-0.19}^{+0.15}+0.5\log_{10}[r/\mathrm{kpc}]$. Independent studies show that while estimates of the dark mass of a given dwarf spheroidal (dSph) galaxy are robust only near the half-light radius, data from the Milky Way's (MW's) dSph satellites are consistent with a narrow range of mass profiles. Here we combine published constraints on the dark halo masses of spirals and dSphs and include available measurements of low surface brightness galaxies for additional comparison. We find that most measured MW dSphs lie on the extrapolation of the mean rotation curve due to DM in spirals. The union of MW-dSph and spiral data appears to follow a mass-radius relation of the form $M_{\mathrm{DM}}(r)/M_{\odot}=200_{-120}^{+200}(r/\mathrm{pc})^2$, or equivalently a constant acceleration $g_{\mathrm{DM}}=3_{-2}^{+3}\times 10^{-9}\mathrm{cm s^{-2}}$, spanning 0.02\la r \la 75 kpc. Evaluation at specific radii immediately generates two results from the recent literature: a common mass for MW dSphs at fixed radius and a constant DM central surface density for galaxies ranging from MW dSphs to spirals. However, recent kinematic measurements indicate that M31's dSph satellites are systematically less massive than MW dSphs of similar size. Such deviations from what is otherwise a surprisingly uniform halo relation presumably hold clues to individual formation and evolutionary histories.Comment: ApJL in press (minor edits to text in order to match version in press

Two Dimensional Velocity Fields of Low Surface Brightness Galaxies

We present high resolution two dimensional velocity fields from integral field spectroscopy along with derived rotation curves for nine low surface brightness galaxies. This is a positive step forward in terms of both data quality and number of objects studied. We fit NFW and pseudo-isothermal halo models to the observations. We find that the pseudo-isothermal halo better represents the data in most cases than the NFW halo, as the resulting concentrations are lower than would be expected for LCDM.Comment: 2 pages, 1 figure, to appear in the XXIst IAP Colloquium "Mass Profiles and Shapes of Cosmological Structures", Paris 4-9 July 2005, (Eds.) G. Mamon, F. Combes, C. Deffayet, B. Fort, (EDP Sciences

Recovering cores and cusps in dark matter haloes using mock velocity field observations

We present mock DensePak Integral Field Unit (IFU) velocity fields, rotation curves and halo fits for disc galaxies formed in spherical and triaxial cuspy dark matter haloes and spherical cored dark matter haloes. The simulated galaxies are ‘observed' under a variety of realistic conditions to determine how well the underlying dark matter halo can be recovered and to test the hypothesis that cuspy haloes can be mistaken for cored haloes. We find that the appearance of the velocity field is distinctly different depending on the underlying halo type. We also find that we can successfully recover the parameters of the underlying dark matter halo. Cuspy haloes appear cuspy in the data and cored haloes appear cored. Our results suggest that the cores observed using high-resolution velocity fields in real dark matter dominated galaxies are genuine and cannot be ascribed to systematic errors, halo triaxiality or non-circular motion