Dark Matter Substructure and Gamma-Ray Annihilation in the Milky Way Halo

By J. Diemand, Michael Kuhlen, P. Madau. 2006

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We present initial results from "Via Lactea," the highest resolution simulation to date of Galactic CDM substructure. It follows the formation of a Milky Way-sized halo with Mhalo = 1.8 × 1012 M☉ in a WMAP three-year cosmology, using 234 million particles. Over 10,000 subhalos can be identified at z = 0: their cumulative mass function is well-fit by N(> Msub) = 0.0064 (Msub/Mhalo)-1 down to Msub = 4 × 106 M☉. The total mass fraction in subhalos is 5.3%, while the fraction of surface mass density in substructure within a projected distance of 10 kpc from the halo center is 0.3%. Because of the significant contribution from the smallest resolved subhalos, these fractions have not converged yet. Sub-substructure is apparent in all the larger satellites, and a few dark matter lumps are resolved even in the solar vicinity. The number of dark satellites with peak circular velocities above 10 km s-1 (5 km s-1) is 124 (812): of these, five (26) are found within 0.1rvir, a region that appeared practically smooth in previous simulations. The neutralino self-annihilation γ-ray emission from dark matter clumps is approximately constant per subhalo mass decade. Therefore, while in our run the contribution of substructure to the γ-ray luminosity of the Galactic halo amounts to only 40% of the total spherically averaged smooth signal, we expect this fraction to grow significantly as resolution is increased further. An all-sky map of the expected annihilation γ-ray flux reaching a fiducial observer at 8 kpc from the Galactic center shows that at the current resolution a small number of subhalos start to be bright enough to be visible against the background from the smooth density field surrounding the observer.

Subfields: Astronomy and Astrophysics, Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/7d34e79fffa13f2b2c58bba971abccf5cfd51d7b

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Citations in the corpus

Small scale problems of the $\Lambda$CDM model: a short review (2016, background): “Tidal stripping from the satellites’ parent: presently observed satellites had the largest masses before accretion (LBA), large enough to retain visible stars, resisting tides when accreted by their parent [378].”
FORMING REALISTIC LATE-TYPE SPIRALS IN A ΛCDM UNIVERSE: THE ERIS SIMULATION (2011, methodology): “Dubbed “Eris”, the simulation described in this paper is part of a campaign of extreme resolution simulations of the formation of Milky Way-sized galaxies (Diemand et al. 2007, 2008).”
Gamma Ray Signals from Dark Matter: Concepts, Status and Prospects (2012, background): “-of-sight integral to the one obtained assuming a smooth (e.g. Einasto) component only. Roughly, every decade in subhalo masses down to the cutoﬀ scale contributes the same to the total gamma-ray ﬂux [103] (with small subhalos possibly being slightly more important [79]), though the details depend c”
Bayesian strong gravitational-lens modelling on adaptive grids: objective detection of mass substructure in Galaxies (2008, methodology): “Nevertheless subsequent studiesof similar gravitationally lensed systems have shown that therequired mass fraction in substructure is higher than what is obtained numerical simulations (Mao et al. 2004; Macciò & Miranda 2006; Diemand et al. 2007a).”
THE ULTRA-LONG GAMMA-RAY BURST 111209A: THE COLLAPSE OF A BLUE SUPERGIANT? (2012, background): “However, as pointed out by several authors, such a mechanism is not efficient at 100% (e.g., Klypin et al. 1999; Diemand et al. 2007), and galaxies with a very low metallicity should still exist in the local universe.”
THE UNORTHODOX ORBITS OF SUBSTRUCTURE HALOS (2008, background): “…discrepancy between the simulation results and the naive expectation of the SSIM was pointed out by Balogh, Navarro & Morris (2000), and confirmed by subsequent studies (Mamon et al 2004, Gill et al 2005, Diemand et al 2007) but its physical origin has not yet been conclusively pinned down.”
History of dark matter (2018, neutral): “Alternative targets for indirect searches have also been proposed, including Galactic dark matter subhalos not associated with dwarf galaxies (Diemand, Kuhlen, and Madau, 2007; Pieri, Bertone, and Branchini, 2008), and density “spikes” of dark matter around black holes (Gondolo and Silk, 1999;…”
Resolving cosmic structure formation with the Millennium-II simulation (2009, background): “An alternative tack is to focus all of one’s computational resources on the formation of a single galaxy-mass halo, thus allowing substantially enhanced mass resolution (Diemand et al. 2007, 2008; Springel et al. 2008; Stadel et al. 2008).”
Redefining the Missing Satellites Problem (2007, methodology): “The recently-completed Via Lactea run is the highestresolution simulation of galactic substructure to date, containing an order of magnitude more particles than its predecessors (Diemand et al. 2007).”
Colloquium: Annual modulation of dark matter (2013, methodology): “High-resolution cosmological dark matter simulations, such as Via Lactea (Diemand, Kuhlen, and Madau, 2007; Diemand et al., 2008), GHALO (Stadel et al., 2008), and Aquarius (Springel et al., 2008), find residual substructure from the merging process that includes dark matter clumps, cold streams, an”
Ahf: AMIGA'S HALO FINDER (2009, background): “It has been found before (e.g. Ghigna et al. 2000; Helmi et al. 2002; De Lucia et al. 2004; Gao et al. 2004; van den Bosch et al. 2005; Diemand et al. 2007; Giocoli et al. 2008; Springel et al. 2008) that the subhalo mass function can be described with a functional form Nsub(> M) ∝ M −α, with α =…”
ELVIS: Exploring the Local Volume in Simulations (2013, methodology): “The correlation between apeak and Vmax is a combination of the apeak − Vpeak correlation and the effects of orbital evolution on subhalo density structure (for discussions on these expected trends see, e.g., Zentner & Bullock 2003; Kazantzidis et al. 2004; Diemand et al. 2007b).”
CLUMPY STREAMS FROM CLUMPY HALOS: DETECTING MISSING SATELLITES WITH COLD STELLAR STRUCTURES (2010, background): “However, they predict an order of magnitude more dark-matter subhalos within the halos of typical galaxies than the number of known satellite galaxies orbiting the Milky Way (Klypin et al. 1999; Moore et al. 1999; Diemand et al. 2007; Springel et al. 2008).”
Optimized dark matter searches in deep observations of Segue 1 with MAGIC (2013, background): “Given how the number of known dSphs was orders of magnitude lower that the one predicted by the N-body simulations (the so-called missing satellite problem, [103], it was reasonable to assume that the existing census of Milky Way satellites was incomplete, and that new detections may be expected fro”