Gamma-Ray Signal From Earth-Mass Dark Matter Microhalos

Ishiyama, Tomoaki; Makino, Junichiro; Ebisuzaki, Toshikazu

doi:10.1088/2041-8205/723/2/l195

Cited by 85 publications

(140 citation statements)

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“…Given that ultra-high-resolution ΛCDM simulations of structure formation predict subshaloes with masses as low as M1 ∼ 10 −6 M (Ishiyama et al 2010 and references therein), we expect microhaloes to induce a significant tidal heating of self-gravitating objects moving across galaxies like the Milky Way, where the upper limit of the subhalo mass function is M2 ∼ 10 11 M ∼ 10 17 M1, an issue that we study in more detail below.…”

Section: Substructures With Power-law Mass and Size Functionsmentioning

confidence: 95%

Fluctuations of the gravitational field generated by a random population of extended substructures

Peñarrubia

2017

Monthly Notices of the Royal Astronomical Society

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A large population of extended substructures generates a stochastic gravitational field that is fully specified by the function p(F), which defines the probability that a tracer particle experiences a force F within the interval F, F + dF. This paper presents a statistical technique for deriving the spectrum of random fluctuations directly from the number density of substructures with known mass and size functions. Application to the subhalo population found in cold dark matter simulations of Milky Way-sized haloes shows that, while the combined force distribution is governed by the most massive satellites, the fluctuations of the tidal field are completely dominated by the smallest and most abundant subhaloes. In light of this result we discuss observational experiments that may be sufficiently sensitive to Galactic tidal fluctuations to probe the "dark" low-end of the subhalo mass function and constrain the particle mass of warm and ultra-light axion dark matter models.

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Section: Substructures With Power-law Mass and Size Functionsmentioning

confidence: 95%

Fluctuations of the gravitational field generated by a random population of extended substructures

Peñarrubia

2017

Monthly Notices of the Royal Astronomical Society

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“…Computing the merger rate in the small halos discussed above requires us to extrapo-late both the halo mass function and the concentrationmass relation around six orders of magnitude in mass beyond the smallest halos present in the calibration simulations. High-resolution simulations of 10 −4 M cold dark matter micro-halos [31,32] suggest that our assumed concentration-mass relations underestimate the internal density of these halos, making our rates conservative.…”

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confidence: 93%

Did LIGO Detect Dark Matter?

et al. 2016

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We consider the possibility that the black-hole (BH) binary detected by LIGO may be a signature of dark matter. Interestingly enough, there remains a window for masses 20 M M bh 100 M where primordial black holes (PBHs) may constitute the dark matter. If two BHs in a galactic halo pass sufficiently close, they radiate enough energy in gravitational waves to become gravitationally bound. The bound BHs will rapidly spiral inward due to emission of gravitational radiation and ultimately merge. Uncertainties in the rate for such events arise from our imprecise knowledge of the phase-space structure of galactic halos on the smallest scales. Still, reasonable estimates span a range that overlaps the 2 − 53 Gpc −3 yr −1 rate estimated from GW150914, thus raising the possibility that LIGO has detected PBH dark matter. PBH mergers are likely to be distributed spatially more like dark matter than luminous matter and have no optical nor neutrino counterparts. They may be distinguished from mergers of BHs from more traditional astrophysical sources through the observed mass spectrum, their high ellipticities, or their stochastic gravitational wave background. Next generation experiments will be invaluable in performing these tests.The nature of the dark matter (DM) is one of the most longstanding and puzzling questions in physics. Cosmological measurements have now determined with exquisite precision the abundance of DM [1, 2], and from both observations and numerical simulations we know quite a bit about its distribution in Galactic halos. Still, the nature of the DM remains a mystery. Given the efficacy with which weakly-interacting massive particlesfor many years the favored particle-theory explanationhave eluded detection, it may be warranted to consider other possibilities for DM. Primordial black holes (PBHs) are one such possibility [3-6].Here we consider whether the two ∼ 30 M black holes detected by LIGO [7] could plausibly be PBHs. There is a window for PBHs to be DM if the BH mass is in the range 20 M M 100 M [8,9]. Lower masses are excluded by microlensing surveys [10][11][12]. Higher masses would disrupt wide binaries [9,13,14]. It has been argued that PBHs in this mass range are excluded by CMB constraints [15,16]. However, these constraints require modeling of several complex physical processes, including the accretion of gas onto a moving BH, the conversion of the accreted mass to a luminosity, the self-consistent feedback of the BH radiation on the accretion process, and the deposition of the radiated energy as heat in the photon-baryon plasma. A significant (and difficult to quantify) uncertainty should therefore be associated with this upper limit [17], and it seems worthwhile to examine whether PBHs in this mass range could have other observational consequences.In this Letter, we show that if DM consists of ∼ 30 M BHs, then the rate for mergers of such PBHs falls within the merger rate inferred from GW150914. In any galactic halo, there is a chance two BHs will undergo a hard scatter, lose energy to a s...

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“…For precise predictions of the annihilation gammarays in the Milky Way, we need to know the fine structures of dark matter halos, since the gamma-ray flux from dark matter structures is proportional to the square of their density and inverse square of the distance from us. Ishiyama et al (2010) [28] found that the central density of the smallest dark matter structures is very high. If they survive near our Sun, the annihilation signals could be observable as gamma-ray point-sources.…”

Section: Introductionmentioning

confidence: 99%

“…Unfortunately, we cannot simulate such a wide dynamic range with currently available computational resources. Ishiyama et al 2010 [28] simulated only the smallest structures. With the simulation described here, we extend this strategy further.…”

Section: Introductionmentioning

confidence: 99%

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4.45 Pflops astrophysical N-body simulation on K computer -- The gravitational trillion-body problem

Ishiyama

Nitadori

Makino

2012

2012 International Conference for High Performance Computing, Networking, Storage and Analysis

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Abstract-As an entry for the 2012 Gordon-Bell performance prize, we report performance results of astrophysical N -body simulations of one trillion particles performed on the full system of K computer. This is the first gravitational trillion-body simulation in the world. We describe the scientific motivation, the numerical algorithm, the parallelization strategy, and the performance analysis. Unlike many previous Gordon-Bell prize winners that used the tree algorithm for astrophysical N -body simulations, we used the hybrid TreePM method, for similar level of accuracy in which the short-range force is calculated by the tree algorithm, and the long-range force is solved by the particlemesh algorithm. We developed a highly-tuned gravity kernel for short-range forces, and a novel communication algorithm for long-range forces. The average performance on 24576 and 82944 nodes of K computer are 1.53 and 4.45 Pflops, which correspond to 49% and 42% of the peak speed.

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Gamma-Ray Signal From Earth-Mass Dark Matter Microhalos

Cited by 85 publications

References 49 publications

Fluctuations of the gravitational field generated by a random population of extended substructures

Fluctuations of the gravitational field generated by a random population of extended substructures

Did LIGO Detect Dark Matter?

4.45 Pflops astrophysical N-body simulation on K computer -- The gravitational trillion-body problem

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