Rotation Curves Of Spiral Galaxies Research Articles

Thermodynamic Constraints on the Non-Baryonic Dark Matter Gas Composing Galactic Halos

To explain rotation curves of spiral galaxies through Newtonian orbital models, massive halos of non-baryonic dark matter (NBDM) are commonly invoked. The postulated properties are that NBDM interacts gravitationally with baryonic matter, yet negligibly interacts with photons. Since halos are large, low-density gaseous bodies, their postulated attributes can be tested against classical thermodynamics and the kinetic theory of gas. Macroscopic models are appropriate because these make few assumptions. NBDM–NBDM collisions must be elastic to avoid the generation of light, but this does not permit halo gas temperature to evolve. If no such collisions exist, then the impossible limit of absolute zero would be attainable since the other available energy source, radiation, does not provide energy to NBDM. The alternative possibility, an undefined temperature, is also inconsistent with basic thermodynamic principles. However, a definable temperature could be attained via collisions with baryons in the intergalactic medium since these deliver kinetic energy to NBDM. In this case, light would be produced since some proportion of baryon collisions are inelastic, thereby rendering the halo detectable. Collisions with baryons are unavoidable, even if NBDM particles are essentially point masses. Note that <0.0001 × the size of a proton is needed to avoid scattering with γ-rays, the shortest wavelength used to study halos. If only elastic collisions exist, NBDM gas would collapse to a tiny, dense volume (zero volume for point masses) during a disturbance—e.g., cosmic rays. NBDM gas should occupy central galactic regions, not halos, since self-gravitating objects are density stratified. In summary, properties of NBDM halos as postulated would result in violations of thermodynamic laws and in a universe unlike that observed.

Towards exterior/interior correspondence of black-holes

We describe a simple approach for a possible connection between the exterior and interior of black-holes. According to our result, the Schwarzschild radius determines a [Formula: see text]-dimensional sphere that separates two worlds: the exterior, where ordinary matter moves with velocities less than the light velocity, and the interior, where tachyons move with velocities greater than the light velocity. Moreover, we find a geometric map in the complex plane that connects ordinary matter with faster than light particles. Motivated by these results, we also find that the exterior and the interior structures of black-holes can be unified in a world of [Formula: see text]-dimensions. Finally, we comment about the possibility that superluminal particles in the interior of a black-hole may provide an alternative solution of the rotation curves of spiral galaxies.

Eleanor Margaret Burbidge

Eleanor Margaret Burbidge

Self-Interacting Dark Matter Subhalos in the Milky Way’s Tides

We study evolution of self-interacting dark matter subhalos in the MilkyWay tidal field. The interaction between the subhalos and the MilkyWay's tides lead to more diverse dark matter distributions in the inner region, compared to their cold dark matter counterparts. We test this scenario with two MilkyWay satellite galaxies, Draco and Fornax, opposite extremes in the inner dark matter content, and find that they can be accommodated within the self-interacting dark matter model proposed to explain the diverse rotation curves of spiral galaxies in the field.

Slowly rotating Bose–Einstein condensate compared with the rotation curves of 12 dwarf galaxies

Context.The high plateaus of the rotation curves of spiral galaxies suggest either that there is a dark component or that the Newtonian gravity requires modifications on galactic scales to explain the observations. We assemble a database of 12 dwarf galaxies, for which optical (R-band) and near-infrared (3.6 μm) surface brightness density together with spectroscopic rotation curve data are available, in order to test the slowly rotating Bose–Einstein condensate (BEC) dark matter model.Aims.We aim to establish the angular velocity range compatible with observations, bounded from above by the requirement of finite-size halos, to check the model fits with the dataset, and the universality of the BEC halo parameter ℛ.Methods.We constructed the spatial luminosity density of the stellar component of the dwarf galaxies based on their 3.6 μm andR-band surface brightness profiles, assuming an axisymmetric baryonic mass distribution with arbitrary axis ratio. We built up the gaseous component of the mass by employing an inside-truncated disk model. We fitted a baryonic plus dark matter combined model, parametrized by theM/Lratios of the baryonic components and parameters of the slowly rotating BEC (the central densityρc, size of the BEC halo ℛ in the static limit, angular velocityω) to the rotation curve data.Results.The 3.6 μm surface brightness of six galaxies indicates the presence of a bulge and a disk component. The shape of the 3.6 μm andR-band spatial mass density profiles being similar is consistent with the stellar mass of the galaxies emerging wavelength-independent. The slowly rotating BEC model fits the rotation curve of 11 galaxies out of 12 within the 1σsignificance level, with the average of ℛ as 7.51 kpc and standard deviation of 2.96 kpc. This represents an improvement over the static BEC model fits, also discussed. For the 11 best-fitting galaxies the angular velocities allowing for a finite-size slowly rotating BEC halo are less then 2.2 × 10−16s−1.For a scattering length of the BEC particle ofa ≈ 106fm, as allowed by terrestrial laboratory experiments, the mass of the BEC particle is slightly better constrained than in the static case asm ∈ [1.26 × 10−17 ÷ 3.08 × 10−17] (eV c−2).

Cold or Warm Dark Matter?: A Study of Galaxy Stellar Mass Distributions

We compare the observed galaxy stellar mass distributions in the redshift range with expectations of the cold ΛCDM and warm ΛWDM dark matter models, and obtain the warm dark matter cut-off wavenumber: . This result is in agreement with the independent measurements with spiral galaxy rotation curves, confirms that kfs is due to warm dark matter free-streaming, and is consistent with the scenario of dark matter with no freeze-in and no freeze-out. Detailed properties of warm dark matter can be derived from kfs. The data disfavors the ΛCDM model.

Fermion or Boson Dark Matter?

We measure properties of dark matter in four well motivated scenarios: fermions with ultra-relativistic thermal equilibrium (URTE), bosons with URTE, fermions with non-relativistic thermal equilibrium (NRTE), and bosons with NRTE. We attempt to discriminate between these four scenarios with studies of spiral galaxy rotation curves, and galaxy stellar mass distributions. The measurements show evidence for boson dark matter with a significance of 3.5σ, and obtain no significant discrimination between URTE and NRTE.

Physics in one dimension with perpendicular non-locality

A single momentum-carrying dimension connected by Lorentz transformations to a perpendicular non-local dimension having time but lacking spatial measures is applied to electromagnetic radiation, thermal radiation, the Schrödinger equation, Kepler’s 3:rd law, the rotation curve of spiral galaxies, and the universe as a whole represented by the linear part of its apparent expansion. This is made possible by identifying and making local terms equal to non-local ones as prescribed by the geometry. For example, 1-D momentum, the oscillating orbited radius of a system and baryonic mass are local whereas field components, oscillation periods and the electron cloud of an atom are non-local. Accordingly, in thermal radiation the physical process of a single quantum transfer replaces field radiation intensity as a function value. The Schrödinger equation can be rearranged and split into factors of circulating current carried by electrons surrounding magnetic charge. The latter result derives from a suitable factorization of the Bohr atom. Based on the assumption that the geometrical framework is valid generally for the rest frame the so-called ‘dark matter’ of galaxies can be identified by analogy with black body radiation and with the electron cloud as being non-local as might be expected of a ‘massive field’. The basic theory yields a radius that is the inverse of a line increment per unit length and per unit time as in Hubble’s constant. A tentative numerical value of this line increment appears as a residue when the Bohr atom is factorized for the purpose of providing a circular current to the Schrödinger equation.

The dichotomy of dark matter fraction and total mass density slope of galaxies over five dex in mass

AbstractWe analyse the mass density distribution in the centres of galaxies across five orders of magnitude in mass range. Using high-quality spiral galaxy rotation curves and infrared photometry from SPARC, we conduct a systematic study of their central dark matter (DM) fraction (fDM) and their mass density slope (α), within their effective radius. We show that lower mass spiral galaxies are more DM dominated and have more shallow mass density slopes when compared with more massive galaxies, which have density profiles closer to isothermal. Low-mass (${M_{*}}\lesssim 10^{10}\, {\mathrm{M}_\odot}$) gas-rich spirals span a wide range of fDM values, but systematically lower than in gas-poor systems of similar mass. With increasing galaxy mass, the values of fDM decrease and the density profiles steepen. In the most massive late-type gas-poor galaxies, a possible flattening of these trends is observed. When comparing these results to massive (${M_{*}}\gtrsim 10^{10}\, {\mathrm{M}_\odot}$) elliptical galaxies from SPIDER and to dwarf ellipticals (dEs) from SMACKED, these trends result to be inverted. Hence, the values of both fDM and α, as a function of M*, exhibit a U-shape trend. At a fixed stellar mass, the mass density profiles in dEs are steeper than in spirals. These trends can be understood by stellar feedback from a more prolonged star formation period in spirals, causing a transformation of the initial steep density cusp to a more shallow profile via differential feedback efficiency by supernovae, and by galaxy mergers or AGN feedback in higher mass galaxies.

Effect of magnetic field on the rotation curves of spiral galaxies

Discrepancies between expected and observed rotation curves in spiral galaxies are commonly interpreted as evidence for the existence of dark matter. Dark matter can explain the observed flat rotation curves at the outer radii. However, some rotation curves of spiral galaxies exhibit rising features at large distances from the galactic centers that cannot be attributed to dark matter alone. Addition of magnetic field contribution to the rotation curves of spiral galaxies has been proposed in some literature to explain the rising features. In this work we investigated the rotation curves of three spiral galaxies, i.e. NGC 2841, NGC 6946, and M 31, whose profiles of azimuthal magnetic field are available in literature. In general, decomposition scenarios using four components (stellar disk, gas, bulge, and dark matter halo) with magnetic field fit better to the observational data.

A note on cosmological features of modified Newtonian potentials

Considering some modified Newtonian potentials and the Hubble law in writing the total energy of a test mass located at the edge of a flat Friedmann–Robertson–Walker (FRW) universe, we obtain several modified Friedmann equations. Interestingly enough, our study shows that the employed potentials, while some of them have some successes in modeling the spiral galaxies rotation curves, may also address an accelerated universe. This fact indicates that dark energy and dark matter may have some common origins and aspects.

Probing dark matter and dark energy through gravitational time advancement

The expression of gravitational time advancement (negative time delay) for particles with non-zero mass in Schwarzschild geometry has been obtained. The influences of the gravitational field that describes the observed rotation curves of spiral galaxies and that of dark energy (in the form of cosmological constant) on time advancement of particles have also been studied. The present findings suggest that in presence of dark matter gravitational field the time advancement may take place irrespective of gravitational field of the observer, unlike the case of pure Schwarzschild geometry where gravitational time advancement takes place only when the observer is situated at stronger gravitational field compare to the gravitational field encountered by the particle during its journey. When applied to the well known case of SN 1987a, it is found that the net time delay of a photon/gravitational wave is much smaller than quoted in the literature. In the presence of dark matter field, the photon and neutrinos from SN 1987a should have been suffered gravitational time advancement rather than the delay.

Biases in inferring dark matter profiles from dynamical and lensing measurements

The degeneracy between disc and halo contributions in spiral galaxy rotation curves makes it difficult to obtain a full understanding of the distribution of baryons and dark matter in disc galaxies like our own Milky Way. Using mock data, we study how constraints on dark matter profiles obtained from kinematics, strong lensing, or a combination of the two are affected by assumptions about the halo model. We compare four different models: spherical isothermal and Navarro-Frenk-White halos, along with spherical and elliptical Burkert halos. For both kinematics and lensing we find examples where different models fit the data well but give enclosed masses that are inconsistent with the true (i.e., input) values. This is especially notable when the input and fit models differ in having cored or cuspy profiles (such as fitting an NFW model when the underlying dark matter distribution follows a different profile). We find that mass biases are more pronounced with lensing than with kinematics, and using both methods can help reduce the bias and provide stronger constraints on the dark matter distributions.

Simulations and Measurements of Warm Dark Matter Free-Streaming and Mass

We compare simulated galaxy distributions in the cold ΛCDM and warm ΛWDM dark matter models. The ΛWDM model adds one parameter to the ΛCDM model, namely the cut-off wavenumber kfs of linear density perturbations. The challenge is to measure kfs. This study focuses on “smoothing lengths” π/kfs in the range from 12 Mpc to 1 Mpc. The simulations reveal two distinct galaxy populations at any given redshift z: hierarchical galaxies that form bottom up starting at the transition mas Mfs, and stripped down galaxies that lose mass to neighboring galaxies during their formation, are near larger galaxies, often have filamentary distributions, and seldom fill voids. We compare simulations with observations, and present four independent measurements of kfs, and the mass mh of dark matter particles, based on the redshift of first galaxies, galaxy mass distributions, and rotation curves of spiral galaxies.

Rotation Curve of the Milky Way from Classical Cepheids

Abstract Flat rotation curves of spiral galaxies are considered as an evidence for dark matter, but the rotation curve of the Milky Way is difficult to measure. Various objects were used to track the rotation curve in the outer parts of the Galaxy, but most studies rely on incomplete kinematical information and inaccurate distances. Here, we use a sample of 773 Classical Cepheids with precise distances based on mid-infrared period–luminosity relations coupled with proper motions and radial velocities from Gaia to construct the accurate rotation curve of the Milky Way up to the distance of ∼20 kpc from the Galactic center. We use a simple model of Galactic rotation to measure the rotation speed of the Sun Θ0 = 233.6 ± 2.8 km s−1, assuming a prior on the distance to the Galactic center R 0 = 8.122 ± 0.031 kpc from the GRAVITY Collaboration. The rotation curve at Galactocentric distances 4 ≲ R ≲ 20 kpc is nearly flat with a small gradient of −1.34 ± 0.21 km s−1 kpc−1. This is the most accurate Galactic rotation curve at distances R > 12 kpc constructed so far.

A Study of Dark Matter with Spiral Galaxy Rotation Curves. Part II

In Part II of this study of spiral galaxy rotation curves we apply corrections and estimate all identified systematic uncertainties. We arrive at a detailed, precise, and self-consistent picture of dark matter.

A Study of Dark Matter with Spiral Galaxy Rotation Curves

To constrain the properties of dark matter, we study spiral galaxy rotation curves measured by the THINGS collaboration. A model that describes a mixture of two self-gravitating non-relativistic ideal gases, “baryons” and “dark matter”, reproduces the measured rotation curves within observational uncertainties. The model has four parameters that are obtained by minimizing a x2 between the measured and calculated rotation curves. From these four parameters, we calculate derived galaxy parameters. We find that dark matter satisfies the Boltzmann distribution. The onset of Fermi-Dirac or Bose-Einstein degeneracy obtains disagreement with observations and we determine, with 99% confidence, that the mass of dark matter particles is mh> 16 eV if fermions, or mh> 45 eV if bosons. We measure the root-mean-square velocity of dark matter particles in the spiral galaxies. This observable is of cosmological origin and allows us to obtain the root-mean-square velocity of dark matter particles in the early universe when perturbations were still linear. Extrapolating to the past we obtain the expansion parameter at which dark matter particles become non-relativistic: ahNR=[4.17±0.34(STAT)±2.50(SYST)]×10−6. Knowing we then obtain the dark matter particle mass mh=69.0±4.2(stat)±31.0(syst)eV, and the ratio of dark matter-to-photon temperature Th/T=0.389±0.008(stat)±0.058(syst) after e+e− annihilation while dark matter remains ultra-relativistic. We repeat these measurements with ten galaxies with masses that span three orders of magnitude, and angular momenta that span five orders of magnitude, and obtain fairly consistent results. We conclude that dark matter was once in thermal equilibrium with the (pre?) Standard Model particles (hence the observed Boltzmann distribution) and then decoupled from the Standard Model and from self-annihilation at temperatures above mμ. These results disfavor models with freeze-out or freeze-in. We also measure the primordial amplitude of vector modes, and constrain the baryon-dark matter cross-section: . Finally, we consider sterile Majorana neutrinos as a dark matter candidate.

Large scale hydrodynamic modes of oscillations in gaseous disks of flat galaxies with a kink on rotation curves

Abstract The properties of unstable large-scale hydrodynamic (HD) modes of oscillations in the gaseous disk of a flat galaxy with a rotation curve having a velocity jump in the inner region of the disk are numerically investigated. It is shown that some of these modes can form a regular pseudo-ring, and others can generate a spiral structure in a model galactic disk, with the rotation curve that can approximate the observed rotation curves in nearby massive spiral galaxies (such as M31, M81). The characteristic time of formation of the regular structure turns out to be . (1 − 2) GY, the corotation is located in the region of the velocity jump (on the radius∼ 2 − 4 kpc). The properties of the generated densitywaves are determined by the parameters of the velocity jumpon the rotation curve (relative amplitude and steepness of the velocity profile decrease), as well as the temperature (velocity dispersion) of the gas in the disk. For the first time, it was investigated how the global HD modes and the spiral structures formed by them will change in the case of the presence of a jump in the profile of the equilibrium surface density. This model profile was set in the form of a slightly smeared falling density step. Main results were obtained for two-arm m = 2 azimuthal harmonic.

On the gravitomagnetic origins of the anomalous flat rotation curves of spiral galaxies

We demonstrate that in-principle, one of the five solutions presented in the reading Nyambuya (2015b), i.e., a solution of the Four Poisson-Laplace equation of gravitation [or Nordström (1912) equation of gravitation] can be used to explain the anomalous flat rotation curves of spiral galaxies. The proposed solution does not invoke the exotic hypothesis of darkmatter but makes the assumption that our existing Laws of Gravitation need to be amended. Our proposed amendment falls well within the accepted domain of legitimate gravitational field equations.

Mass of Spiral Galaxies by Means of a Maximum Disc Model

Maximum disc mass models for a set of spiral galaxies from the Ursa Major Cluster are presented. We construct the models using the Hunther method and the particular solutions are chosen in such away that the circular velocities are adjusted very accurately to the observed rotation curves of some specific spiral galaxies. Under the maximum disc hypothesis, we consider that the rotation curves of the analyzed galaxies can be modeled with only the contribution of the disc. This implies that it is not necessary to consider the contribution of the dark matter halo in the inner part of the spiral. In this way, the models reproduce the global behavior of the rotation curves in the great majority of galaxies. Producing good adjustments to calculate the total mass of these galaxies, and yielding values of the order of 1010M0. Based on the verticalstability criterion presented by Viera & Ramos-Caro(2016), we find that all the galaxies analyzed present a vertically stable behavior.On the other hand, from the analysis of the epicyclic frequency we find that al lthe models exhibit mainly a radial stable behaviour except at the edge of the disc.