Need For Non-baryonic Dark Matter Research Articles

Debated Models for Galactic Rotation Curves: A Review and Mathematical Assessment

Proposed explanations of galactic rotation curves (RC = tangential velocity vs. equatorial radius, determined from Doppler measurements) involve dramatically different assumptions. A dominant, original camp invoked huge amounts of unknown, non-baryonic dark matter (NBDM) in surrounding haloes to reconcile RC simulated using their Newtonian orbital models (NOMs) for billions of stars in spiral galaxies with the familiar Keplerian orbital patterns of the few, tiny planets in our Solar System. A competing minority proposed that hypothetical, non-relativistic, non-Newtonian forces govern the internal motions of galaxies. More than 40 years of controversy has followed. Other smaller groups, unsatisfied by explanations rooted in unknown matter or undocumented forces, have variously employed force summations, spin models, or relativistic adaptations to explain galactic rotation curves. Some small groups have pursued inverse models and found no need for NBDM. The successes, failures, and underlying assumptions of the above models are reviewed in this paper, focusing on their mathematical underpinnings. We also show that extractions of RC from Doppler measurements need revising to account for the effect of galaxy shape on flux-velocity profiles and for the possible presence of a secondary spin axis. The latter is indicated by complex Doppler shift patterns. Our findings, combined with independent evidence such as hadron collider experiments failing to produce non-baryonic matter, suggest that a paradigm shift is unfolding.

Dark Matter Dogma: A Study of 214 Galaxies

The aim of this paper is to test the need for non-baryonic dark matter in the context of galactic rotation and the apparent difference between distributions of galactic mass and luminosity. We present a set of rotation curves and 3.6 μm surface brightness profiles for a diverse sample of 214 galaxies. Using rotation curves as the sole input into our Newtonian disk model, we compute non-parametric radial profiles of surface mass density. All profiles exhibit lower density than parametric models with dark halos and provide a superior fit with observed rotation curves. Assuming all dynamical mass is in main-sequence stars, we estimate radial distributions of characteristic star mass implied by the corresponding pairs of density and brightness profiles. We find that for 132 galaxies or 62% of the sample, the relation between density and brightness can be fully explained by a radially declining stellar mass gradient. Such idealized stellar population fitting can also largely address density and brightness distributions of the remaining 82 galaxies, but their periphery shows, on average, 14 M⊙/pc2 difference between total density and light-constrained stellar density. We discuss how this density gap can be interpreted, by considering a low-luminosity baryonic matter, observational uncertainties, and visibility cutoffs for red dwarf populations. Lastly, we report tight correlation between radial density and brightness trends, and the discovered flattening of surface brightness profiles—both being evidence against dark matter. Our findings make non-baryonic dark matter unnecessary in the context of galactic rotation.

Neutrinos and cosmology

Neutrinos have provided the major consummated connection between particle physics and astrophsycis and cosmology. This talk emphasizes cosmological neutrinos and dark matter. It also reviews the basic big bang nucleosynthesis arguments which are critical to the need for non-baryonic dark matter and constrain the number of families of neutrinos (including “sterile” families).

Cosmological implications of light element abundances: theory.

Primordial nucleosynthesis provides (with the microwave background radiation) one of the two quantitative experimental tests of the hot Big Bang cosmological model (versus alternative explanations for the observed Hubble expansion). The standard homogeneous-isotropic calculation fits the light element abundances ranging from 1H at 76% and 4He at 24% by mass through 2H and 3He at parts in 105 down to 7Li at parts in 1010. It is also noted how the recent Large Electron Positron Collider (and Stanford Linear Collider) results on the number of neutrinos (Nnu) are a positive laboratory test of this standard Big Bang scenario. The possible alternate scenario of quark-hadron-induced inhomogeneities is also discussed. It is shown that when this alternative scenario is made to fit the observed abundances accurately, the resulting conclusions on the baryonic density relative to the critical density (Omegab) remain approximately the same as in the standard homogeneous case, thus adding to the robustness of the standard model and the conclusion that Omegab approximately 0.06. This latter point is the driving force behind the need for nonbaryonic dark matter (assuming total density Omegatotal = 1) and the need for dark baryonic matter, since the density of visible matter Omegavisible < Omegab. The recent Population II B and Be observations are also discussed and shown to be a consequence of cosmic ray spallation processes rather than primordial nucleosynthesis. The light elements and Nnu successfully probe the cosmological model at times as early as 1 sec and a temperature (T) of approximately 10(10) K (approximately 1 MeV). Thus, they provided the first quantitative arguments that led to the connections of cosmology to nuclear and particle physics.

Light element nucleosynthesis - A false clue?

It is proposed that the dynamically estimated value for the cosmological density parameter, Omega(dy) = 0.15 x 10 exp +/- 0.20, reflects the baryon density at decoupling, resulting in lower initial, primordial values of D and the He-3 than are observed. An early generation of massive stars, forming somewhat after decoupling, collapses to black holes with masses of about 10 exp 6.5 solar masses. If they later accrete gas and emit a quasarlike (X, gamma)-ray spectrum, then (gamma, (He-4)) photodisintegration reactions will increase D and He-3 to the observed range, leaving a high-energy background radiation field similar to that observed. The massive black holes become the dynamically observed dark matter galactic halos. This scenario obviates the need for nonbaryonic dark matter and provides a specific form for the requisite baryonic dark matter; it thus reduces the number of density parameters: Omega(0) - Omega(dy) = Omega(BBN) is approximately equal to 0.15.

Big Bang nucleosynthesis: the Standard Model and alternatives

Big bang nucleosynthesis provides (with the microwave background radiation) one of the two quantitative experimental tests of the big bang cosmological model. This paper reviews the standard homogeneous-isotropic calculation and shows how it fits the light element abundances ranging from 4He at 24% by mass through 2H and 3He at parts in 105 down to 7Li at parts in 1010. Furthermore, the recent LEP (and SLC) results on the number of neutrinos are discussed as a positive laboratory test of the standard scenario. Discussion is presented on the improved observational data as well as the improved neutron lifetime data. Alternate scenarios of decaying matter or of quark-hadron induced inhomogeneities are discussed. It is shown that when these scenarios are made to fit the observed abundances accurately, the resulting conclusions on the baryonic density relative to the critical density, Ωb, remain approximately the same as in the standard homogeneous case, thus, adding to the robustness of the conclusion that Ωb ≃ 0.06. This latter point is the driving force behind the need for non-baryonic dark matter (assuming Ωtotal = 1) and the need for dark baryonic matter, since Ωvisible < Ωb.

The consistency problems of large scale structure

The combined problems of large scale structure, the need for non-baryonic dark matter if Ω = 1, and the need to make galaxies early in the history of the universe seem to be placing severe constraints on cosmological models. In addition, it is shown that the bulk of the baryonic matter is also dark and must be accounted for as well. The nucleosynthesis arguments are now strongly supported by high energy collider experiments as well as astronomical abundance data. The arguments for dark matter are reviewed and it is shown that observational dynamical arguments and nucleosynthesis are all still consistent at Ω ∼ 0.1. However, the inflation paradigm requires Ω = 1, thus, the need for non-baryonic dark matter. A non-zero cosmological constant is argued to be an inappropriate solution. Dark matter candidates fall into two categories, hot (neutrino-like) and cold (axion or massive photino-like). New observations of large scale structure in the universe (voids, foam, and large scale velocity fields) seem to be most easily understood if the dominant matter of the universe is in the form of low mass (9eV ≤ mv ≤ 35eV) neutrinos. Cold dark matter, even with biasing, seems unable to duplicate the combination of these observations (of particular significance here are the large velocity fields, if real). However, galaxy formation is difficult with hot matter. The potentially fatal problems of galaxy formation with neutrinos may be remedied by combining them with either cosmic strings or explosive galaxy formation. The former naturally gives the scale-free correlation function for galaxies, clusters, and superclusters. The latter requires fine tuning and percolation to get the large scales and the scale-free correlation function. However, combining hot matter and strings reduces the ability of the hot matter to give some of the large scale features and still yield Ω = 1. Questions to be examined are raised.