Shaken and stirred: the Milky Way's dark substructures

Sawala, Till; Pihajoki, Pauli; Johansson, Peter H.; Frenk, Carlos S.; Navarro, Julio F.; Oman, Kyle A.; White, Simon D. M.

doi:10.1093/mnras/stx360

Cited by 139 publications

(179 citation statements)

References 119 publications

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“…Any of these processes may act to blow out gas from the galaxies in our baryonic simulations, shallowing their gravitational potential significantly in lowermass galaxies like dwarfs, which in turn allows for easier removal of dark matter mass through gravitational interactions. Sawala et al (2017) also found that the abundance of for subhalos with masses below 10 9.5 M in the APOSTLE simulations was reduced at all distances out to 200 kpc from the hosts. For the largest distances they examine, between 50 and 200 kpc, Sawala et al (2017) found a reduction in substructure abundance of 23 per cent.…”

Section: Comparison With Dark Matter-only Simulationsmentioning

confidence: 54%

“…Sawala et al (2017) also found that the abundance of for subhalos with masses below 10 9.5 M in the APOSTLE simulations was reduced at all distances out to 200 kpc from the hosts. For the largest distances they examine, between 50 and 200 kpc, Sawala et al (2017) found a reduction in substructure abundance of 23 per cent. This is similar to our baryons given the cosmic baryon fraction ( f b ≡ Ω b /Ω m ) of our baryonic simulations.…”

Section: Comparison With Dark Matter-only Simulationsmentioning

confidence: 54%

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A profile in FIRE: resolving the radial distributions of satellite galaxies in the Local Group with simulations

Samuel

Wetzel

Tollerud

et al. 2019

Monthly Notices of the Royal Astronomical Society

122

139

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While many tensions between Local Group (LG) satellite galaxies and ΛCDM cosmology have been alleviated through recent cosmological simulations, the spatial distribution of satellites remains an important test of physical models and physical versus numerical disruption in simulations. Using the FIRE-2 cosmological zoom-in baryonic simulations, we examine the radial distributions of satellites with M * > 10 5 M around 8 isolated Milky Way-(MW) mass host galaxies and 4 hosts in LG-like pairs. We demonstrate that these simulations resolve the survival and physical destruction of satellites with M * 10 5 M . The simulations broadly agree with LG observations, spanning the radial profiles around the MW and M31. This agreement does not depend strongly on satellite mass, even at distances 100 kpc. Host-to-host variation dominates the scatter in satellite counts within 300 kpc of the hosts, while time variation dominates scatter within 50 kpc. More massive host galaxies within our sample have fewer satellites at small distances, likely because of enhanced tidal destruction of satellites via the baryonic disks of host galaxies. Furthermore, we quantify and provide fits to the tidal depletion of subhalos in baryonic relative to dark matter-only simulations as a function of distance. Our simulated profiles imply observational incompleteness in the LG even at M * 10 5 M : we predict 2-10 such satellites to be discovered around the MW and possibly 6-9 around M31. To provide cosmological context, we compare our results with the radial profiles of satellites around MW analogs in the SAGA survey, finding that our simulations are broadly consistent with most SAGA systems.

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Section: Comparison With Dark Matter-only Simulationsmentioning

confidence: 54%

Section: Comparison With Dark Matter-only Simulationsmentioning

confidence: 54%

A profile in FIRE: resolving the radial distributions of satellite galaxies in the Local Group with simulations

Samuel

Wetzel

Tollerud

et al. 2019

Monthly Notices of the Royal Astronomical Society

122

139

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“…Finally, it is important to note that our DM limits are subject to potentially large uncertainties. In addition to the already mentioned caveats in the computation of the minimum detection flux (see Section 3.1), 10 there exist important theoretical uncertainties in the N-body simulation predictions, such as the survival probability of the lightest subhalos near the Galactic center [67][68][69], 11 the precise subhalo structural properties, the impact of baryons on the subhalo population [22,70] or the value of the minimum subhalo mass that is adopted to separate between visible and dark satellites [71]. These and other issues that affect the Galactic subhalo population will be addressed elsewhere.…”

Section: Resultsmentioning

confidence: 99%

Constraints to Dark Matter Annihilation from High-Latitude HAWC Unidentified Sources

Coronado-Blázquez

2019

Galaxies

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The ΛCDM cosmological framework predicts the existence of thousands of subhalos in our own Galaxy not massive enough to retain baryons and become visible. Yet, some of them may outshine in gamma rays provided that the dark matter is made of weakly interacting massive particles (WIMPs), that would self-annihilate and would appear as unidentified gamma-ray sources (unIDs) in gamma-ray catalogs. Indeed, unIDs have proven to be competitive targets for dark matter searches with gamma rays. In this work, we focus on the three high-latitude (|b| ≥ 10 o ) sources present in the 2HWC catalog of the High Altitude Water Cherenkov (HAWC) observatory with no clear associations at other wavelenghts. Indeed, only one of these sources, 2HWC J1040+308, is found to be above the HAWC detection threshold when considering 760 days of data, i.e., a factor 1.5 more exposure time than in the original 2HWC catalog. Other gamma-ray instruments such as Fermi-LAT or VERITAS at lower energies do not detect the source. Also, this unID is reported as spatially extended, making it even more interesting in a dark matter search context. While waiting for more data that may shed further light on the nature of this source, we set competitive upper limits on the annihilation cross section by comparing this HAWC unID to expectations based on state-of-the-art N-body cosmological simulations of the Galactic subhalo population. We find these constraints to be particularly competitive for heavy WIMPs, i.e., masses above ∼ 25 (40) TeV in the case of the bb (τ + τ − ) annihilation channel, reaching velocity-averaged cross section values of 2 · 10 −25 (5 · 10 −25 ) cm 3 s −1 . Although far from testing the thermal relic cross section value, the obtained limits are independent and nicely complementary to those from radically different DM analyses and targets, demonstrating once again the high potential of this DM search approach.

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“…This is another indication that it is the radial sub-halo distribution that drives min ∆ rms to lower values, not the presence of actual satellite planes. In this regard it is important to note that the analysed simulations are collision-less, and that the host halos do not contain central galaxy disks, whose tidal effects can result in a depletion of sub-halos in the innermost regions which results in more radially extended sub-halo systems (Garrison-Kimmel et al 2017;Sawala et al 2017). This effect on the distribution of satellite sub-halos is present in the Phat ELVIS sample that includes a central galaxy potential.…”

Section: Plane Thickness Vs Halo Propertiesmentioning

confidence: 99%

Do Halos that Form Early, Have High Concentration, Are Part of a Pair, or Contain a Central Galaxy Potential Host More Pronounced Planes of Satellite Galaxies?

Pawlowski

Bullock

Kelley

et al. 2019

ApJ

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The Milky Way, the Andromeda galaxy, and Centaurus A host flattened distributions of satellite galaxies which exhibits coherent velocity trends indicative of rotation. Comparably extreme satellite structures are very rare in cosmological ΛCDM simulations, giving rise to the "satellite plane problem". As a possible explanation it has been suggested that earlier-forming, higher concentration host halos contain more flattened and kinematically coherent satellite planes. We have tested for such a proposed correlation between the satellite plane and host halo properties in the ELVIS suite of simulations. We find evidence neither for a correlation of plane flattening with halo concentration or formation time, nor for a correlation of kinematic coherence with concentration. The height of the thinnest sub-halo planes does correlate with the host virial radius and with the radial extent of the sub-halo system. This can be understood as an effect of not accounting for differences in the radial distribution of sub-halos, and selecting them from different volumes than covered by the actual observations. Being part of a halo pair like the Local Group does not result in more narrow or more correlated satellite planes either. Additionally, using the PhatELVIS simulations we show that the presence of a central galaxy potential does not favor more narrow or more correlated satellite planes, it rather leads to slightly wider planes. Such a central potential is a good approximation of the dominant effect baryonic physics in cosmological simulations has on a sub-halo population. This suggests that, in contrast to other small-scale problems, the planes of satellite galaxies issue is made worse by accounting for baryonic effects. 1 We refer the interested reader to two of our recent contribution on this topic: and Pawlowski et al. (2015b).

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Shaken and stirred: the Milky Way's dark substructures

Cited by 139 publications

References 119 publications

A profile in FIRE: resolving the radial distributions of satellite galaxies in the Local Group with simulations

A profile in FIRE: resolving the radial distributions of satellite galaxies in the Local Group with simulations

Constraints to Dark Matter Annihilation from High-Latitude HAWC Unidentified Sources

Do Halos that Form Early, Have High Concentration, Are Part of a Pair, or Contain a Central Galaxy Potential Host More Pronounced Planes of Satellite Galaxies?

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