The galaxy population in cold and warm dark matter cosmologies

Wang, Lan; González-Pérez, Violeta; Xie, Lizhi; Cooper, Andrew P.; Frenk, Carlos S.; Gao, Liang; Hellwing, Wojciech A.; Helly, John; Lovell, Mark R.; Jiang, Lu

doi:10.1093/mnras/stx788

Cited by 22 publications

(25 citation statements)

References 123 publications

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“…1 Since WDM particles have non-negligible velocities at high redshifts, structure formation is suppressed at scales below the DM's free-streaming length, delaying the halo and star formation periods. It is precisely this suppression in the growth of small scale structures what allows solving some of the problems of CDM cosmologies mentioned above [25,[78][79][80][81][82][83][84][85][86][87][88][89][90][91][92]. Furthermore, if the WDM candidate is identified with a keV sterile neutrino, this could provide the origin for the recently observed X-ray signals in galaxy clusters, the galactic center and the cosmic X-ray background [93][94][95][96].…”

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confidence: 92%

Warm dark matter and the ionization history of the Universe

et al. 2017

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In warm dark matter scenarios structure formation is suppressed on small scales with respect to the cold dark matter case, reducing the number of low-mass halos and the fraction of ionized gas at high redshifts and thus, delaying reionization. This has an impact on the ionization history of the Universe and measurements of the optical depth to reionization, of the evolution of the global fraction of ionized gas and of the thermal history of the intergalactic medium, can be used to set constraints on the mass of the dark matter particle. However, the suppression of the fraction of ionized medium in these scenarios can be partly compensated by varying other parameters, as the ionization efficiency or the minimum mass for which halos can host star-forming galaxies. Here we use different data sets regarding the ionization and thermal histories of the Universe and, taking into account the degeneracies from several astrophysical parameters, we obtain a lower bound on the mass of thermal warm dark matter candidates of mX > 1.3 keV, or ms > 5.5 keV for the case of sterile neutrinos non-resonantly produced in the early Universe, both at 90% confidence level. I. INTRODUCTIONThe appearance of the first generation of galaxies, when the Universe was a few hundred million years old, lead to the end of the so-called dark ages of the Universe. The ultraviolet (UV) photons emitted in these galaxies, gradually ionized the neutral hydrogen which had rendered the Universe transparent following the epoch of recombination, in a process known as reionization [1]. However, so far, the exact moment when cosmic reionization took place is not precisely known [2].The reionization transition in the late Universe increases the number density of free electrons, n e , which can scatter the Cosmic Microwave Background (CMB), with a probability related to the optical depth at reionization, τ , i.e., the line-of-sight integral of n e weighted with the Thomson cross section, and dominated by single-ionized hydrogen and helium states. The effect of free electrons on the CMB temperature anisotropies leads to a suppression of the acoustic peaks by a factor e −2τ at scales within the horizon at the reionization period, a signature which is very degenerate with the amplitude of the primordial power spectrum, A s . Nevertheless, the reionization process creates linear polarization on the CMB spectrum due to the scattering between free electrons and the large-scale CMB quadrupole. This signature, usually dubbed as the "reionization bump", with the induced polarized power scaling as τ 2 (see, e.g., Fig. 2 of Ref.[3]), and peaks at scales larger than the horizon size at the reionization period, resulting in a determination of τ almost free of degeneracies (see Ref. [3] or corresponding chapter in Ref. [2] for an exhaustive description of the epoch of reionization (EoR) and its impact on the CMB). Measurements by the Wilkinson Microwave Anisotropy Probe (WMAP) of the optical depth to reionization, τ = 0.089 ± 0.014, indicated an early-reionization scenario ...

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confidence: 92%

Warm dark matter and the ionization history of the Universe

et al. 2017

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“…In order to ease comparison with previous studies, we shall also study the case of thermal warm dark matter (WDM) with mass in the keV range (see Refs. [33,34,[42][43][44][45][46][47][48][49][50][51][52][53][54][55][56][57][84][85][86][87][88][89][90][91][92][93][94][95][96][97][98][99][100][101][102] and the most recent works of Refs. [77,79]).…”

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confidence: 99%

Dark matter microphysics and 21 cm observations

2019

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Dark matter interactions with massless or very light Standard Model particles, as photons or neutrinos, may lead to a suppression of the matter power spectrum at small scales and of the number of low mass haloes. Bounds on the dark matter scattering cross section with light degrees of freedom in such interacting dark matter (IDM) scenarios have been obtained from e.g. early time cosmic microwave background physics and large scale structure observations. Here we scrutinize dark matter microphysics in light of the claimed 21 cm EDGES 78 MHz absorption signal. IDM is expected to delay the 21 cm absorption features due to collisional damping effects. We identify the astrophysical conditions under which the existing constraints on the dark matter scattering cross section could be largely improved due to the IDM imprint on the 21 cm signal, providing also an explicit comparison to the WDM scenario.

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“…The latter is related to predictions within the ΛCDM cosmology for the number of DM sub-halos, which is much larger than the observed number of satellite galaxies that orbit close to the Milky Way. A number of solutions to these two problems have been proposed in the literature (see, e.g., the recent works [11,12] and references therein). Possible avenues range from lowering the total mass of the satellites by different means (e.g., via baryon or supernovae feedback effects [13,14]; see also Ref.…”

Section: Introductionmentioning

confidence: 99%

Cold dark matter plus not-so-clumpy dark relics

Diamanti

Ando

Gariazzo

et al. 2017

J. Cosmol. Astropart. Phys.

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Abstract. Various particle physics models suggest that, besides the (nearly) cold dark matter that accounts for current observations, additional but sub-dominant dark relics might exist. These could be warm, hot, or even contribute as dark radiation. We present here a comprehensive study of two-component dark matter scenarios, where the first component is assumed to be cold, and the second is a non-cold thermal relic. Considering the cases where the non-cold dark matter species could be either a fermion or a boson, we derive consistent upper limits on the non-cold dark relic energy density for a very large range of velocity dispersions, covering the entire range from dark radiation to cold dark matter. To this end, we employ the latest Planck Cosmic Microwave Background data, the recent BOSS DR11 and other Baryon Acoustic Oscillation measurements, and also constraints on the number of Milky Way satellites, the latter of which provides a measure of the suppression of the matter power spectrum at the smallest scales due to the free-streaming of the non-cold dark matter component. We present the results on the fraction f ncdm of non-cold dark matter with respect to the total dark matter for different ranges of the non-cold dark matter masses. We find that the 2σ limits for non-cold dark matter particles with masses in the range 1-10 keV are f ncdm ≤ 0.29 (0.23) for fermions (bosons), and for masses in the 10-100 keV range they are f ncdm ≤ 0.43 (0.45), respectively.

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The galaxy population in cold and warm dark matter cosmologies

Cited by 22 publications

References 123 publications

Warm dark matter and the ionization history of the Universe

Warm dark matter and the ionization history of the Universe

Dark matter microphysics and 21 cm observations

Cold dark matter plus not-so-clumpy dark relics

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