scholarly journals Dynamical estimates of the local density of dark matter

1988 ◽  
Vol 215 (1) ◽  
pp. 73-80 ◽  
Author(s):  
Ricardo A. Flores
Keyword(s):  
Dark Matter ◽  
Local Density

scholarly journals Photons in a cold axion background and strong magnetic fields: Polarimetric consequences

2015 ◽  
Vol 30 (17) ◽  
pp. 1550099 ◽  
Author(s):  
Domènec Espriu ◽  
Albert Renau
Keyword(s):  
Magnetic Field ◽  
Dark Matter ◽  
Galactic Halo ◽  
Local Density ◽  
Polarization Plane ◽  
Strong Magnetic Fields ◽  
Two Photon ◽  
Main Effect ◽  
Optical Table ◽  
The Magnetic Field

In this work, we analyze the propagation of photons in an environment where a strong magnetic field (perpendicular to the photon momenta) coexists with an oscillating cold axion background with the characteristics expected from dark matter in the galactic halo. Qualitatively, the main effect of the combined background is to produce a three-way mixing among the two photon polarizations and the axion. It is interesting to note that in spite of the extremely weak interaction of photons with the cold axion background, its effects compete with those coming from the magnetic field in some regions of the parameter space. We determine (with one plausible simplification) the proper frequencies and eigenvectors as well as the corresponding photon ellipticity and induced rotation of the polarization plane that depend both on the magnetic field and the local density of axions. We also comment on the possibility that some of the predicted effects could be measured in optical table-top experiments.

scholarly journals Angular Momentum Growth around Local Density Maxima

1988 ◽  
Vol 130 ◽  
pp. 552-552
Author(s):  
A. F. Heavens ◽  
J. A. Peacock
Keyword(s):  
Dark Matter ◽  
Angular Momentum ◽  
Power Spectrum ◽  
Total Angular Momentum ◽  
Cold Dark Matter ◽  
Local Density ◽  
Probability Distributions ◽  
Power Spectra ◽  
Elliptical Galaxies ◽  
Angular Momenta

We have calculated the growth of angular momentum about local density maxima at early epochs. We find that high peaks experience higher torques than low peaks, counteracting the short collapse time during which the high peaks can acquire angular momentum. Which effect is dominant depends on the perturbation power spectrum: for power spectra characteristic of both cold dark matter and hot dark matter, the effects nearly cancel, and the total angular momentum acquired by a collapsing object is almost independent of the height of the peak. Furthermore, the distributions of angular momenta acquired by collapsing protosystems are extremely broad, for all power spectra, far exceeding any modest differences between peaks of different height.These results indicate that it is not possible to account for the systematic differences in angular momentum properties of disk and elliptical galaxies simply by postulating that the latter arise from fluctuations of greater overdensity, contrary to some recent suggestions. The figure shows the probability distributions for the final angular momentum acquired by peaks of dimensionless height 1–4, for a power spectrum similar to cold dark matter. A fuller account of this work has been submitted to MNRAS.

scholarly journals The distinct stellar-to-halo mass relations of satellite and central galaxies: insights from the IllustrisTNG simulations

2020 ◽  
Vol 500 (3) ◽  
pp. 3957-3975
Author(s):  
Christoph Engler ◽  
Annalisa Pillepich ◽  
Gandhali D Joshi ◽  
Dylan Nelson ◽  
Anna Pasquali ◽  
...  
Keyword(s):  
Dark Matter ◽  
Environmental Effects ◽  
Total Mass ◽  
Local Density ◽  
Stellar Mass ◽  
Mass Relation ◽  
Systematic Deviation ◽  
Dynamical Mass ◽  
Mass Fractions ◽  
Satellite Galaxies

ABSTRACT We study the stellar-to-halo mass relation (SHMR) for central and satellite galaxies with total dynamical masses above $10^{10.5}\, \rm {M}_\odot$ using the suite of cosmological magnetohydrodynamical simulations IllustrisTNG. In particular, we quantify environmental effects on satellite populations from TNG50, TNG100, and TNG300 located within the virial radius of group- and cluster-like hosts with total masses of $10^{12\!-\!15.2}\, \rm {M}_\odot$. At fixed stellar mass, the satellite SHMR exhibits a distinct shift towards lower dynamical mass compared to the SHMR of centrals. Conversely, at fixed dynamical mass, satellite galaxies appear to have larger stellar-to-total mass fractions than centrals by up to a factor of a few. The systematic deviation from the central SHMR is larger for satellites in more massive hosts, at smaller cluster-centric distances, with earlier infall times, and that inhabits higher local density environments; moreover, it is in place already at early times (z ≲ 2). Systematic environmental effects might contribute to the perceived galaxy-to-galaxy variation in the measured SHMR when galaxies cannot be separated into satellites and centrals. The SHMR of satellites exhibits a larger scatter than centrals (by up to ∼0.8 dex), over the whole range of dynamical mass. The shift of the satellite SHMR results mostly from tidal stripping of their dark matter, which affects satellites in an outside-in fashion: The departure of the satellite SHMR from the centrals’ relation diminishes for measurements of dynamical mass in progressively smaller apertures. Finally, we provide a family of fitting functions for the SHMR predicted by IllustrisTNG.

scholarly journals DARK ENERGY AND KEY PHYSICAL PARAMETERS OF CLUSTERS OF GALAXIES

2013 ◽  
Vol 53 (A) ◽  
pp. 550-554
Author(s):  
Gennady S. Bisnovatyi-Kogan ◽  
Artur Chernin ◽  
Marco Merafina
Keyword(s):  
Dark Matter ◽  
Dark Energy ◽  
Local Density ◽  
Critical Value ◽  
Virgo Cluster ◽  
Physical Parameters ◽  
Zero Gravity ◽  
Clusters Of Galaxies ◽  
Coma Cluster ◽  
Static Solutions

We study physics of clusters of galaxies embedded in the cosmic dark energy background. The equilibrium and stability of polytropic spheres with equation of state of the matter             <em>P = Kp<sup>γ</sup></em>, <em>γ</em> = 1 + 1/n, in presence of a non-zero cosmological constant is investigated. The equilibrium state exists only for central densities <em>p</em><sub>0</sub> larger than the critical value <em>p</em><sub>c</sub> and there are no static solutions at <em>p</em><sub>0</sub>&lt;<em>p</em><sub>c</sub>. At this density the radius of the configuration is equal to the zero-gravity radius, at which the dark matter gravity is balanced by the dark energy antigravity. It is shown, that dark energy reduces the dynamic stability of the configuration. We show that the dynamical effects of dark energy are strong in clusters like the Virgo cluster, which halo radius is close to the zero-gravity radius. It is shown, that the empirical data on clusters like the Virgo cluster or the Coma cluster, are consistent with the assumption that the local density of dark energy on the scale of clusters of galaxies is the same as on the global cosmological scales.

scholarly journals Velocity independent constraints on spin-dependent DM-nucleon interactions from IceCube and PICO

2020 ◽  
Vol 80 (9) ◽  
Author(s):  
M. G. Aartsen ◽  
◽  
M. Ackermann ◽  
J. Adams ◽  
J. A. Aguilar ◽  
...  
Keyword(s):  
Dark Matter ◽  
Velocity Distribution ◽  
Cross Section ◽  
Local Density ◽  
Bubble Chamber ◽  
High Energy ◽  
The Self ◽  
The Sun ◽  
The Galaxy ◽  
Spin Dependent Scattering

AbstractAdopting the Standard Halo Model (SHM) of an isotropic Maxwellian velocity distribution for dark matter (DM) particles in the Galaxy, the most stringent current constraints on their spin-dependent scattering cross-section with nucleons come from the IceCube neutrino observatory and the PICO-60 $$\hbox {C}_3\hbox {F}_8$$ C 3 F 8 superheated bubble chamber experiments. The former is sensitive to high energy neutrinos from the self-annihilation of DM particles captured in the Sun, while the latter looks for nuclear recoil events from DM scattering off nucleons. Although slower DM particles are more likely to be captured by the Sun, the faster ones are more likely to be detected by PICO. Recent N-body simulations suggest significant deviations from the SHM for the smooth halo component of the DM, while observations hint at a dominant fraction of the local DM being in substructures. We use the method of Ferrer et al. (JCAP 1509: 052, 2015) to exploit the complementarity between the two approaches and derive conservative constraints on DM-nucleon scattering. Our results constrain $$\sigma _{\mathrm{SD}} \lesssim 3 \times 10^{-39} \mathrm {cm}^2$$ σ SD ≲ 3 × 10 - 39 cm 2 ($$6 \times 10^{-38} \mathrm {cm}^2$$ 6 × 10 - 38 cm 2 ) at $$\gtrsim 90\%$$ ≳ 90 % C.L. for a DM particle of mass 1 TeV annihilating into $$\tau ^+ \tau ^-$$ τ + τ - ($$b\bar{b}$$ b b ¯ ) with a local density of $$\rho _{\mathrm{DM}} = 0.3~\mathrm {GeV/cm}^3$$ ρ DM = 0.3 GeV / cm 3 . The constraints scale inversely with $$\rho _{\mathrm{DM}}$$ ρ DM and are independent of the DM velocity distribution.

scholarly journals Dark matter halo properties versus local density and cosmic web location

2018 ◽  
Vol 483 (2) ◽  
pp. 2101-2122 ◽  
Author(s):  
Tze Goh ◽  
Joel Primack ◽  
Christoph T Lee ◽  
Miguel Aragon-Calvo ◽  
Doug Hellinger ◽  
...  
Keyword(s):  
Dark Matter ◽  
Local Density ◽  
Dark Matter Halo

scholarly journals Variable G versus the Accelerated Expansion of the Universe

2017 ◽  
Vol 26 (1) ◽  
pp. 293-296
Author(s):  
Bernard G. Colenbrander ◽  
Willem S. Hulscher
Keyword(s):  
Dark Matter ◽  
Local Density ◽  
Accelerated Expansion ◽  
Astronomical Observations ◽  
History Of ◽  
Expansion Of The Universe ◽  
Valid Evidence ◽  
Newtonian Constant ◽  
The Universe ◽  
Variable G

Abstract It is shown that the hypothesis of permitting variability of the Newtonian constant G, increasing with the local density of dark matter, implies that there is no need for the introduction of a cosmological constant or accelerated expansion of the universe. A higher value of G in the younger universe leads to an enhanced redshift of the spectra from e.g. supernovae, which results in an estimation of a larger distance and magnitude. Interpreting relevant astronomical observations in terms of both effects leads remarkably to a linear relationship between the redshift and the magnitude of the supernovae throughout the history of the universe. Furthermore it is shown, that from CMB measurements, no reliable conclusions can be drawn about the structure and geometry of the universe. It is concluded that, if the hypothesis survives further tests, no valid evidence is available that would point to an accelerated expansion of the universe and therefore it is not necessary to assume the existence of dark energy.

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