Shaken and Stirred: The Milky Way's Dark Substructures
arXiv:1609.01718 · doi:10.1093/mnras/stx360
Abstract
The predicted abundance and properties of the low-mass substructures embedded inside larger dark matter haloes differ sharply among alternative dark matter models. Too small to host galaxies themselves, these subhaloes may still be detected via gravitational lensing, or via perturbations of the Milky Way's globular cluster streams and its stellar disk. Here we use the Apostle cosmological simulations to predict the abundance and the spatial and velocity distributions of subhaloes in the range 10^6.5-10^8.5 solar masses inside haloes of mass ~ 10^12 solar masses in LCDM. Although these subhaloes are themselves devoid of baryons, we find that baryonic effects are important. Compared to corresponding dark matter only simulations, the loss of baryons from subhaloes and stronger tidal disruption due to the presence of baryons near the centre of the main halo, reduce the number of subhaloes by ~ 1/4 to 1/2, independently of subhalo mass, but increasingly towards the host halo centre. We also find that subhaloes have non-Maxwellian orbital velocity distributions, with centrally rising velocity anisotropy and positive velocity bias which reduces the number of low-velocity subhaloes, particularly near the halo centre. We parameterise the predicted population of subhaloes in terms of mass, galactocentric distance, and velocities. We discuss implications of our results for the prospects of detecting dark matter substructures and for possible inferences about the nature of dark matter.
19 pages, submitted to MNRAS, comments welcome
References in corpus (25)
- The NumPy array: a structure for efficient numerical computation
- The EAGLE project: Simulating the evolution and assembly of galaxies and their environments
- The EAGLE simulations of galaxy formation: calibration of subgrid physics and model variations
- Too big to fail? The puzzling darkness of massive Milky Way subhaloes
- The effect of photo-ionization on the cooling rates of enriched, astrophysical plasmas
- Chemical enrichment in cosmological, smoothed particle hydrodynamics simulations
- Massloss of galaxies due to a UV-background
- Baryon effects on the internal structure of LCDM halos in the EAGLE simulations
- On the mass-to-light ratio of the local Galactic disc and the optical luminosity of the Galaxy
- Detection of a 63 Degree Cold Stellar Stream in the Sloan Digital Sky Survey
- Equal- and unequal-mass mergers of disk and elliptical galaxies with black holes
- Density profiles of galaxy groups and clusters from SDSS galaxy-galaxy weak lensing
- Phase-space structure in the local dark matter distribution and its signature in direct detection experiments
- Bent by baryons: the low mass galaxy-halo relation
- Inference of the Cold Dark Matter substructure mass function at z=0.2 using strong gravitational lenses
- Globular Cluster Streams as Galactic High-Precision Scales - The Poster Child Palomar 5
- SubHaloes going Notts: The SubHalo-Finder Comparison Project
- The abundance of (not just) dark matter haloes
- How well can cold-dark-matter substructures account for the observed radio flux-ratio anomalies?
- Forensics of Subhalo-Stream Encounters: The Three Phases of Gap Growth
- The emptiness of voids: yet another over-abundance problem for the LCDM model
- Gaps in globular cluster streams: giant molecular clouds can cause them too
- An Orbit Fit for the Grillmair Dionatos Cold Stellar Stream
- The impact of going beyond the Maxwell distribution in direct dark matter detection rates
- The stability of stellar disks in Milky-Way sized dark matter halos