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It has recently been suggested that a gravitational transition of the effective Newton's constant G eff by about 10%, 50–150 Myrs ago could lead to the resolution of both the Hubble crisis and the growth tension of the standard Λ CDM model. Hints for such an abrupt transition with weaker gravity at times before the transition, have recently been identified in Tully–Fisher galactic mass-velocity data, and also in Cepheid SnIa calibrator data. Here we use Monte-Carlo simulations to show that such a transition could significantly increase (by a factor of 3 or more) the number of long period comets (LPCs) impacting the solar system from the Oort cloud (semi-major axis of orbits ≳ 10 4 AU ). This increase is consistent with observational evidence from the terrestrial and lunar cratering rates, indicating that the impact flux of kilometer sized objects increased by at least a factor of 2 over that last 100 Myrs compared to the long term average. This increase may also be connected with the Chicxulub impactor event that produced the Cretaceous–Tertiary (K-T) extinction of 75% of life on Earth (including dinosaurs) about 66 Myrs ago. We use Monte-Carlo simulations to show that for isotropic Oort cloud comet distribution with initially circular orbits, random velocity perturbations (induced e.g., by passing stars and/or galactic tidal effects), lead to a deformation of the orbits that increases significantly when G eff increases. A 10% increase in G eff leads to an increase in the probability of the comets to enter the loss cone and reach the planetary region (pericenter of less than 10 AU) by a factor that ranges from 5% (for velocity perturbation much smaller than the comet initial velocity) to more than 300% (for total velocity perturbations comparable with the initial comet velocity). [ABSTRACT FROM AUTHOR]

We use an up-to-date compilation of Tully-Fisher data to search for transitions in the evolution of the Tully-Fisher relation. Using an up-to-date data compilation, we find hints at ≈3σ level for a transition at critical distances Dc ≃ 9 Mpc and Dc ≃ 17 Mpc. We split the full sample in two subsamples, according to the measured galaxy distance with respect to splitting distance Dc, and identify the likelihood of the best-fit slope and intercept of one sample with respect to the best-fit corresponding values of the other sample. For Dc ≃ 9 Mpc and Dc ≃ 17 Mpc, we find a tension between the two subsamples at a level of Δχ²x2 > 17 (3.5σ). Using Monte Carlo simulations, we demonstrate that this result is robust with respect to random statistical and systematic variations of the galactic distances and is unlikely in the context of a homogeneous dataset constructed using the Tully-Fisher relation. If the tension is interpreted as being due to a gravitational strength transition, it would imply a shift in the effective gravitational constant to lower values for distances larger than Dc by ΔG/G ≃ -0.1. Such a shift is of the anticipated sign and magnitude but at a somewhat lower distance (redshift) than the gravitational transition recently proposed to address the Hubble and growth tensions ( ΔG/G ≃ -0.1 at the transition redshift of zt ≲ 0.01 (Dc ≲ 40 Mpc)). [ABSTRACT FROM AUTHOR]

In this paper, we find a four-dimensional metric for a large black hole immersed in dark matter. Specifically, we look for and find a static spherically symmetric black hole solution to the Einstein equations which gives, in the Newtonian limit, the rotation curves of galaxies, including the flat region and the baryonic Tully–Fisher relation, and which has a regular horizon. We obtain as well the energy–momentum tensor of the dark matter sourcing this spacetime and it turns, in special, to satisfy the four energy conditions (dominant, weak, null and strong) everywhere outside the horizon. This black-hole-dark-matter system represents a successful simplified model for galaxies, opens a new area for exploring the relativistic regime of dark matter, and shows that the theory of General Relativity together with dark matter can account for the rotation curves of galaxies. [ABSTRACT FROM AUTHOR]

Highlights • Nordstrom (1912)'s theory is presented as an alternative theory to the rotation curve problem of spiral galaxies. • No darkmatter is needed, but a new gravitational potential comes into play. • The theory can — in-principle, explain the Tully-Fisher (1977) Relation. Abstract 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. [ABSTRACT FROM AUTHOR]

Direct, inverse, and orthogonal regression fits for Tully-Fisher (TF) relations in the B and K bands are constructed for isolated galaxies in the 2MIG catalog based on data from the catalog and the HyperLEDA data base. The slope of the TF relations becomes steeper on going from the B to the K band, as well as from earlier to later morphological types. The scatter in these relations for highly inclined late type spirals turn out to be factors of 1.3 (B) and 1.8 (K) smaller than for spirals with arbitrary inclinations. Statistically significant regressors are found for multiparameter generalizations of the inverse TF relations in the B-band. [ABSTRACT FROM AUTHOR]

Galactic dynamics is the foundation for simulating galactic structure and for solving other problems. However, the traditional dynamic equations include some unreasonable assumptions and are therefore scientifically invalid. In this paper, by introducing the following three working assumptions, we established the galactic dynamics of high precision and convenient formalism. 1. In the research of large-scale structure, the retarded potential of the gravitational field should be taken into account, and the weak field and low velocity approximation of Einstein's field equation should be adopted. 2. The stars in a fully developed galaxy should be zero-pressure and inviscid fluid, and the equation of motion is different from that of ordinary continuum mechanics. Stars move along geodesics. 3. The structure of the galaxy is only related to the total mass density distribution. The equation of state of dark halo is different from that of ordinary luminous interstellar matter, so their trajectories are also very different. In a galaxy, the dark halo and the ordinary matter are automatically separated. The total mass density distribution can be presupposed according to the observation data, and then it can be determined by comparing the solution of the equations with the observed data. These assumptions and treatments are supported by theory and observation. The variables of the equations of simplified galactic dynamics are separated from each other, and the equations are well-posed and can be solved according to a definite procedure. The solution explains the Tully–Fisher relation. Therefore, this simplified dynamic equation system provides a more reasonable and practical framework for the further study of galactic structure, and can solve many practical problems. In addition, it is closely related to the study of dark matter halo in galaxy. [ABSTRACT FROM AUTHOR]

The 2MFGC catalog we have used contains 18020 galaxies selected from the extended objects in the 2MASS infrared sky survey as having apparent ratios of the axes b/a<0.3. Most of them are spiral galaxies of later morphological types whose disks are seen almost edge-on. The individual distances to the 2724 2MFGC galaxies with known rotation velocities and radial velocities are determined using a multiparameter infrared Tully-Fisher relation. A list of the distances and peculiar velocities of these galaxies is presented. The collective motion of the 2MFGC galaxies relative to the cosmic microwave background is characterized by a velocity V = 199 ± 37 km/s in the direction l = 304° ±11°, b = −8°±8°. Our list is currently the most representative and uniform sample for analyzing non-Hubble motions of galaxies on a scale of ∼100 Mpc. [ABSTRACT FROM AUTHOR]

We analyze the peculiar velocity field for 2400 flat spiral galaxies selected from an infrared sky survey (2MFGC). The distances to the galaxies have been determined from the Tully-Fisher relation in the photometric J band with a dispersion of 0m.45. The bulk motion of this sample relative to the cosmic microwave background (3K) frame has an amplitude of 199 ± 37 km s−1 in the direction l = 290° ± 11°, b = +1° ± 9°. The amplitude of the dipole motion tends to decrease with distance in accordance with the expected convergence of bulk flows in the 3K frame. We believe that external massive attractors similar to the Shapley cluster concentration are responsible for ∼60% of the local flow velocity in the z = 0.03 volume. [ABSTRACT FROM AUTHOR]

Recent data on the Tully–Fisher relation for spiral galaxies are compatible with the traditional correlation for astrophysical systems, where the angular momentum varies as the square of the mass. Such a correlation is consistent with standard gravitational theory, but is not explained by it. We here show that the noted relation follows from currently popular accounts of extended or higher-dimensional gravitational theory. The latter also predicts that the spins of spirals should decay as the universe expands, which can be tested by extending the Tully–Fisher data to higher redshifts. [ABSTRACT FROM AUTHOR]