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The circumgalactic medium (CGM) hosts many physical processes with different kinematic signatures that affect galaxy evolution. We address the CGM–galaxy kinematic connection by quantifying the fraction of H  i that is aligned with galaxy rotation with the equivalent width co-rotation fraction, |$f_{\rm EWcorot}$|⁠. Using 70 quasar sightlines having Hubble Space Telescope /Cosmic Origins Spectrograph H  i absorption (⁠|${12\lt \log (N(\rm{{\rm H}\,{\small I}})/{\rm cm}^{-2})\lt 20}$|⁠) within |$5R_{\rm vir}$| of |$z\lt 0.6$| galaxies we find that |$f_{\rm EWcorot}$| increases with increasing H  i column density. |$f_{\rm EWcorot}$| is flat at |$\sim 0.6$| within |$R_{\rm vir}$| and decreases beyond |$R_{\rm vir}$| to |$f_{\rm EWcorot}$| |$\sim 0.35$|⁠. |$f_{\rm EWcorot}$| also has a flat distribution with azimuthal and inclination angles within |$R_{\rm vir}$|⁠ , but decreases by a factor of two outside of |$R_{\rm vir}$| for minor axis gas and by a factor of 2 for edge-on galaxies. Inside |$R_{\rm vir}$|⁠ , co-rotation dominated H i is located within |$\sim 20$| deg of the major and minor axes. We surprisingly find equal amounts of H  i absorption consistent with co-rotation along both major and minor axes within |$R_{\rm vir}$|⁠. However, this co-rotation disappears along the minor axis beyond |$R_{\rm vir}$|⁠ , suggesting that if this gas is from outflows, then it is bound to galaxies. |$f_{\rm EWcorot}$| is constant over two decades of halo mass, with no decrease for log(M |$_{\rm h}/{\rm M}_{\odot })\gt 12$| as expected from simulations. Our results suggest that co-rotating gas flows are best found by searching for higher column density gas within |$R_{\rm vir}$| and near the major and minor axes. [ABSTRACT FROM AUTHOR]

Recent theory of tachyon neutrinos, providing an explanation for Dark Matter, leads to two sets of experiments for testing that theory. One predicts an enhanced signal in detection of the Cosmic Neutrino Background. The other compares models of Dark Matter used to fit data on galaxy rotation curves and also gravitational lensing. This paper starts with a semi-review of the previous theoretical work. One sees new symmetries in comparing the theory of tachyons to that of ordinary particles. In addition, we present a debunking of the false claim that tachyons would produce a causal paradox; and an apparent contradiction within the new theory, related to Dark Energy, is identified and addressed. [ABSTRACT FROM AUTHOR]

Context. Recent measurements of gas velocity in the outer parts of high redshift galaxies suggest that steeply falling rotation curves may be common or even universal in these galaxies, in contrast to the near universal flat, non-declining rotation curves in nearby galaxies. Aims. The aim was to investigate the implications of these postulated steeply falling rotation curves for the role of dark matter in galaxy formation. Methods. Using an established computer code, the collapse of dark matter and baryonic matter together, starting with a variety of initial conditions, was simulated for comparison with the observed rotation curves. A simulation of collapsing baryonic matter on its own without dark matter was also carried out. The masses of the protogalaxies were chosen to produce a stellar disc in the same mass range as the observed galaxies at roughly the same redshift. Results. As soon as a smooth stellar disc was formed in the baryonic matter, with properties similar to the observed high redshift galaxies, the computed rotation curves were without exception relatively flat to large radius in the gas disc. Only a simulation without a dark matter halo was able to reproduce the observed rotation curves. Conclusions. This implies that if the high redshift steeply falling rotation curves turn out to be common, then the standard scenario of galaxy formation by baryonic matter falling into the potential well of a massive dark matter halo must be wrong, unless there is pressure support via velocity dispersion significantly higher than has so far been observed or resulted from our simulations. It would also imply that for these galaxies the flat rotation curves at low redshift must be due to dark matter which has subsequently fallen into the galactic potential well, or there must be some other explanation for their contemporary flat rotation curves other than dark matter. [ABSTRACT FROM AUTHOR]

The existing reservoirs of neutral atomic hydrogen gas (H I) in galaxies are insufficient to have maintained the observed levels of star formation without some kind of replenishment. This refuelling of the H I reservoirs is likely to occur at column densities an order of magnitude lower than previous observational limits (NH I, limit ∼ 1019 cm−2 at a 30″ resolution over a linewidth of 20 km s−1). In this paper, we present recent deep H I observations of NGC 5068, a nearby isolated star-forming galaxy observed by MeerKAT as part of the MHONGOOSE survey. With these new data, we were able to detect low column density H I around NGC 5068 with a 3σ detection limit of NH I = 6.4 × 1017 cm−2 at a 90″ resolution over a 20 km s−1 linewidth. The high sensitivity and resolution of the MeerKAT data reveal a complex morphology of the H I in this galaxy – a regularly rotating inner disk coincident with the main star-forming disk of the galaxy, a warped outer disk of low column density gas (NH I < 9 × 1019 cm−2), in addition to clumps of gas on the north-western side of the galaxy. We employed a simple two disk model that described the inner and outer disks, which enabled us to identify anomalous gas that deviates from the rotation of the main galaxy. The morphology and the kinematics of the anomalous gas suggest a possible extra-galactic origin. We explore a number of possible origin scenarios that may explain the anomalous gas, and conclude that fresh accretion is the most likely scenario. [ABSTRACT FROM AUTHOR]

Polycyclic Aromatic Hydrocarbons (PAHs) are organic molecules which comprise the smallest particles of dust in the interstellar medium (ISM). Due to their broad/complex emission profiles, obtaining kinematics is a challenge with traditional methods, especially before the advent of the JWST. In this work, we employ Principal Component Analysis (PCA) tomography to analyse JWST /NIRSpec IFU data of three nearby luminous infrared galaxies (LIRGs), namely, NGC 3256 N, NGC 3256 S, and NGC 7469. We detect the signature of rotation in the second principal component of the 3.3  |$\mu$| m PAH feature in all three targets. We construct velocity maps from the principal components for the 3.3  |$\mu$| m PAH feature, Br β (2.625  |$\mu$| m) and molecular hydrogen, H2 1–0 S(1) (2.12  |$\mu$| m). We find that in each target, the PAHs qualitatively follow the rotation of the galaxy, consistent with the rotational signature derived from Br β and H2. There are however some differences, with the PAH rotation in NGC 3256 N appearing at a different position angle, which suggest differences in the motion of the dust as compared to the gas. This kind of analysis opens a new window into this key component of the ISM. [ABSTRACT FROM AUTHOR]

We investigate a mechanism to form and keep a planar spatial distribution of satellite galaxies in the Milky Way (MW), which is called the satellite plane. It has been pointed out that the ΛCDM cosmological model hardly explains the existence of such a satellite plane, so it is regarded as one of the serious problems in the current cosmology. We here focus on a rotation of the gravitational potential of a host galaxy, i.e. a so-called figure rotation, following the previous suggestion that this effect can induce the tilt of a so-called tube orbit. Our calculation shows that a figure rotation of a triaxial potential forms a stable orbital plane perpendicular to the rotational axis of the potential. Thus, it is suggested that the MW's dark halo is rotating with its axis being around the normal line of the satellite plane. Additionally, we find that a small velocity dispersion of satellites is required to keep the flatness of the planar structure, namely the standard derivation of their velocities perpendicular to the satellite plane needs to be smaller than their mean rotational velocity on the plane. Although not all the MW's satellites satisfy this condition, a fraction of them, called member satellites, which are prominently on the plane, do satisfy it. We suggest that this picture explaining the observed satellite plane can be achieved by the filamentary accretion of dark matter associated with the formation of the MW and a group infall of member satellites along this cosmic filament. [ABSTRACT FROM AUTHOR]

We examine some of the consequences of the Exochronous (timeless) metric and the associated Σ GR cosmological model for the formation of galaxies, and, in particular, their characteristic rotation curves. We show how the cumulative curvature from the multiple spatial hypersurfaces in this model leads to a modified version of the Poisson equation, in which the gravitational potential is computed over 4D space. Using this new form of the Poisson equation, we derive an analytic expression for gravitational potential as a function of radial distance for a uniform gas cloud undergoing gravitational collapse. We show that this results in a radial velocity profile that provides an excellent fit with commonly observed galaxy rotation curves, and hence fully accounts for the effects previously ascribed to dark matter. An expression can be derived for the equivalent matter density profile corresponding to the Σ GR gravitational potential, from which it is evident that this is very similar in form to the well-known Navarro–Frenk–White profile. As a further illustration of the consequences of adopting the Exochronous metric, we show how the principle can readily be incorporated into particle-mesh N-body simulations of large-scale structure evolution, using a relaxation solver for the solution to the Poisson equation and the evolution of the gravitational potential. Examples of the use of this simulation model are shown for the following cases: (a) the initial evolution of a large-scale structure, and (b) galaxy formation from a gravitationally collapsing gas cloud. In both cases, it is possible to directly visualise the build-up of the gravitational potential in 3D space as the simulation evolves and note how this corresponds to what is currently assumed to be dark matter. [ABSTRACT FROM AUTHOR]

The radial acceleration relation (RAR) connects the total gravitational acceleration of a galaxy at a given radius, a tot(r), with that accounted for by baryons at the same radius, a bar(r). The shape and tightness of the RAR for rotationally-supported galaxies have characteristics in line with MOdified Newtonian Dynamics (MOND) and can also arise within the cosmological constant + cold dark matter (ΛCDM) paradigm. We use zoom simulations of 20 galaxies with stellar masses of M ⋆ ≃ 107–11 M⊙ to study the RAR in the FIRE-2 simulations. We highlight the existence of simulated galaxies with non-monotonic RAR tracks that 'hook' down from the average relation. These hooks are challenging to explain in Modified Inertia theories of MOND, but naturally arise in all of our ΛCDM-simulated galaxies that are dark-matter dominated at small radii and have feedback-induced cores in their dark matter haloes. We show, analytically and numerically, that downward hooks are expected in such cored haloes because they have non-monotonic acceleration profiles. We also extend the relation to accelerations below those traced by disc galaxy rotation curves. In this regime, our simulations exhibit 'bends' off of the MOND-inspired extrapolation of the RAR, which, at large radii, approach a tot ≈ a bar/ f b, where f b is the cosmic baryon fraction. Future efforts to search for these hooks and bends in real galaxies will provide interesting tests for MOND and ΛCDM. [ABSTRACT FROM AUTHOR]

This work presents the results of a kinematic analysis of the Galaxy that uses a new model as applied to the newest available Gaia data. We carry out the Taylor decomposition of the velocity field up to second order for 18 million high luminosity stars (i.e. OBAF-type stars, giants, and subgiants) from the Gaia DR3 data. We determine the components of mean stellar velocities and their first and second partial derivatives (relative to cylindrical coordinates) for more than 28 thousand points in the plane of our Galaxy. We estimate Oort's constants A, B, C , and K and other kinematics parameters and map them as a function of Galactocentric coordinates. The values found confirm the results of our previous works and are in excellent agreement with those obtained by other authors in the solar neighbourhood. In addition, the introduction of second order partial derivatives of the stellar velocity field allows us to determine the values of the vertical gradient of the Galaxy azimuthal, radial, and vertical velocities. Also, we determine the mean of the Galaxy rotation curve for Galactocentric distances from 4 to 18 kpc by averaging Galactic azimuths in the range −30° < θ <  + 30° about the direction Galactic Centre – Sun – Galactic anticentre. Maps of the velocity components and of their partial derivatives with respect to coordinates within 10 kpc of the Sun reveal complex substructures, which provide clear evidence of non-axisymmetric features of the Galaxy. Finally, we show evidence of differences in the Northern and Southern hemispheres stellar velocity fields. [ABSTRACT FROM AUTHOR]

We present N -body simulations of the process of bulge formation in disc galaxies due to inward migration of massive stellar clumps. The process is accompanied by dark halo heating, with a quasi-isothermal core replacing the initial central density cusp, transforming an initially dark matter dominated central region into a baryon dominated one. The characteristics of the clumps are chosen to be compatible with low redshift observations of stellar clumps in DYNAMO-HST galaxies, which may be relatively long lived in terms of being robust against internal starburst-instigated disruption. We thus test for disruption due to tidal stripping using different clump internal radial profiles; Plummer, Hernquist, and Jaffe, in ascending order of see per central density profile. Our calculations predict that in order for clump migration to be effective in building galactic bulges and dark halo cores, steeply increasing central clump profiles, or a less massive or less concentrated haloes, are preferred. The dependence on such factors may contribute to the diversity in observed total mass distributions and resulting rotation curves in galaxies. When the process is most efficient, a 'bulge-halo conspiracy', with a singular isothermal total density akin to that observed bright galaxies, results. [ABSTRACT FROM AUTHOR]

'Small-scale cosmology' is a theory designed to incorporate the linear redshift versus distance relation, which is inferred from observations, into the theoretical framework independent of the global Robertson–Walker–Friedman (RWF)-type models. The motivation behind this is that the RWF cosmological models, based on the assumptions of homogeneity and a constant matter density, as well as the concept of expanding space inherent to them are not applicable on the scales of observations from which the linear Hubble law is inferred. Therefore, explaining the Hubble law as the small redshift limit of the RWF model or as an effect of expanding space is inconsistent. Thus, the Hubble linear relation between the redshift of an extragalactic object and its distance should be considered an independent law of nature valid in the range of the distances where the RWF cosmology is not valid. In general, the theory, based on that concept, can be developed in different ways. In the present paper, 'small-scale cosmology' is formulated as a theory operating in the (redshift–object coordinates) space, which allows developing a conceptual and computational basis of the theory along the lines of that of special relativity. In such a theory, the condition of invariance of the Hubble law with respect to a change in the observer acceleration plays a central role. In pursuing this approach, the effectiveness of group theoretical methods is exploited. Applying the Lie group method yields transformations of the variables (the redshift and space coordinates of a cosmological object) between the reference frames of the accelerated observers. In this paper, the transformations are applied to studying the effects of the solar system observer acceleration on the observed shape, distribution and rotation curves of galaxy clusters. [ABSTRACT FROM AUTHOR]

We address the galaxy rotation curves through the Yukawa gravitational potential emerging as a correction of the Newtonian potential in extended theories of gravity. On the one hand, we consider the contribution of the galactic bulge, galactic disk, and the dark matter halo of the Navarro–Frenk–White profile, in the framework of the standard Λ CDM model. On the other hand, we use modified Yukawa gravity to show that the rotational velocity of galaxies can be addressed successfully without the need for dark matter. In Yukawa gravity, we recover MOND and show that dark matter might be seen as an apparent effect due to the modification of the law of gravitation in terms of two parameters: the coupling constant α and the characteristic length λ . We thus test our theoretical scenario using the Milky Way and M31 rotation velocity curves. In particular, we place observational constraints on the free parameters of Yukawa cosmology through the Monte Carlo method and then compare our results with the predictions of the Λ CDM paradigm by making use of Bayesian information criteria. Specifically, we find that λ is constrained to be of the order of kpc, while cosmological data suggest λ of the order of Gpc. To explain this discrepancy, we argue that there is a fundamental limitation in measuring λ due to the role of quantum mechanics on cosmological scales. [ABSTRACT FROM AUTHOR]

The Alpha Centauri system has two close stars Alpha and Beta (A & B) and one much further away: Proxima Centauri. All three stars are co-moving with similar chemistry, which implies they are bound, but the fast orbit of Proxima implies it is gravitationally unbound given the visible mass of A and B. This problem cannot be fixed with the addition of dark matter, which must be uniform on such scales, or adding mass to A and B (their mass is well constrained) or by Modified Newtonian Dynamics. A new model for inertia called Quantized Inertia (QI) has been proposed that solves the galaxy rotation problem by reducing the inertia of low-acceleration stars at the galaxies' edge in a new way, thus keeping them bound without the need for dark matter. It is shown here that if QI is applied to Proxima Centauri in the same way, it predicts the observed orbital velocity, within the bounds of observational uncertainty, and binds Proxima, without the need for extra mass. [ABSTRACT FROM AUTHOR]

Antonie ('Anton') Pannekoek (1873 -1960), the founder of the Astronomical Institute of the University of Amsterdam, is remembered as one of the initiators of the field of stellar atmospheres. A second, maybe equally significant part of his research and legacy did not concern stellar, but Galactic astronomy. He was awarded an honorary doctorate by Harvard University and the Gold Medal of the Royal Astronomical Society (UK) for his total research effort. From his long-term interest in viewing and mapping the Milky Way he became convinced that the sidereal system was built up of clouds of stars, condensations of various sizes in a smooth but low-density stratum of stars. In addition, there were dark clouds together with streaks with little or no extinction in between them. So, he took the opposite view of Jacobus C. Kapteyn, concerning the stellar distribution, which the latter regarded in first approximation to be smooth and uniform in longitude so that star counts as a function of apparent magnitude depended primarily on latitude. Pannekoek's research into the structure of the stellar system consisted of various parts. He first looked at bright clouds of the Milky Way, such as in Cygnus, and assuming these were isolated structures he estimated their distance from their contribution to star counts by stars far out in the bright tail of the luminosity function. He found values of tens of kpc, which would mean their distribution was similar in extent to that of Shapley's globular cluster system. Later he had to reduce his distance by a factor over two, and later still to admit he had to retract the method altogether. He developed a rigorous method of estimating distances of dark clouds from modeling star counts off and on the cloud, preceding Wolf's quick and crude method that became very widely applied. He should have received more credit for this. During the 1920s it became clear that extinction was a major effect and that the Galaxy rotated around a distant center. Pannekoek unsuccessfully looked for the large central mass, that Oort found had to be in the center of rotation in the Galaxy, by estimating masses of some bright star clouds in the Milky Way. He also pioneered the mapping of the local structure in the Galaxy from spectroscopic parallaxes, using the fact--following Kapteyn's study of 'helium stars'--that for B- and A-stars and K-giants the intrinsic dispersion in absolute magnitude is small. The distributions of different spectral types are substantially different. He tried without success to explain Kapteyn's Star Streams from the gravitational pull of the irregular distribution of matter in the solar neighborhood. As a teenager he was fascinated by the appearance of the Milky Way and he started producing sketches of the Milky Way by drawing curves of equal (surface) brightness or in modern terms isophotes. In the course of his career this resulted in isophotal maps of both the northern and the southern Milky Way, first from visual observations, later from photographic surface photometry using out-of-focus exposures. The care and patience with which he visually produced his maps is admirable. For the photographic work he enlisted help from Wolf in Heidelberg and Vote at Lembang, who both provided extensive plate material. Unlike the care that has been employed for photographic surface photometry in more recent times, a wide range of photographic emulsions and developers was used and calibration of the characteristic curve was done on separate plates "... of the same type, if possible!" (my italics). In this paper I compare Pannekoek's resulting isophotal maps with detailed photographic surface photometry of the southern Milky Way in the 1980s and 1990s by the group in Bochum and to the almost all-sky mapping by the Pioneer 10 spacecraft, free of zodiacal light, from beyond the asteroid belt. This shows Pannekoek's visual and photographic maps to be surprisingly accurate, in spite of all the non-uniformity in observers for the first category and in exposure, emulsion, etc., with magnitude scale and zero point errors of a few tenths of a magnitude, except in the southern Coalsack, where he quoted a surface brightness that is much too faint. The legacy of Pannekoek in the area of Galactic research consists of his mapping of the structure of the nearby part of the Galaxy, the distances of dark clouds, and isophotal maps of the Milky Way. His other contributions turned out inconclusive or wrong as a result of his conviction, resulting from his many years of observing and mapping the Milky Way, that the nearby distribution is characterized primarily by more or less isolated clouds of stars and by dust restricted to isolated dark clouds and streaks. In Appendix 1 I show that the widespread notion that the center of the Galaxy is located in the constellation Sagittarius is not so compelling as usually thought and could with equal justification be placed in Scorpius. Appendix 2 provides short curriculae vitae of a few Dutch PhDs that have been referred to in this paper. [ABSTRACT FROM AUTHOR]

Spiral density waves can arise in galactic discs as linear instabilities of the underlying stellar distribution function. Such an instability grows exponentially in amplitude at some fixed growth rate β before saturating non-linearly. However, the mechanisms behind saturation, and the resulting saturated spiral amplitude, have received little attention. Here, we argue that one important saturation mechanism is the non-linear trapping of stars near the spiral's corotation resonance. Under this mechanism, we show analytically that an m -armed spiral instability will saturate when the libration frequency of resonantly trapped orbits reaches |$\omega _\mathrm{lib} \sim \mathrm{a\, \, few}\times m^{1/2} \beta$|⁠. For a galaxy with a flat rotation curve, this implies a maximum relative spiral surface density |$\vert \delta \Sigma /\Sigma _0\vert \sim \mathrm{a\, \, few} \times (\beta /\Omega _\mathrm{p})^2 \cot \alpha$|⁠ , where Ωp is the spiral pattern speed and α is its pitch angle. This result is in reasonable agreement with recent N -body simulations, and suggests that spirals driven by internally-generated instabilities reach relative amplitudes of at most a few tens of per cent; higher amplitude spirals, like in M51 and NGC 1300, are likely caused by very strong bars and/or tidal perturbations. [ABSTRACT FROM AUTHOR]

The f(R, T) gravity models, for which R is the Ricci scalar and T is the trace of the energy–momentum tensor, elevate the degrees of freedom of the renowned f(R) theories, by making the Einstein field equations of the theory to also depend on T. While such a dependence can be motivated by quantum effects, the existence of imperfect or extra fluids, or even a cosmological "constant" which effectively depends on T, the formalism can truly surpass some deficiencies of f(R) gravity. As the f(R, T) function is arbitrary, several parametric models have been proposed ad hoc in the literature and posteriorly confronted with observational data. In the present article, we use gaussian process to construct an f (R , T) = R + f (T) model. To apply the gaussian process we use a series of measurements of the Hubble parameter. We then analytically obtain the functional form of the function. By construction, this form, which is novel in the literature, is well-adjusted to cosmological data. In addition, by extrapolating our reconstruction to redshift z = 0 , we were able to constrain the Hubble constant value to H 0 = 69.97 ± 4.13 km s - 1 Mpc - 1 with 5 % precision. Lastly, we encourage the application of the functional form herewith obtained to other current problems of observational cosmology and astrophysics, such as the rotation curves of galaxies. [ABSTRACT FROM AUTHOR]

We consider an alternative to dark matter as a potential solution to various remaining problems in physics: the addition of stochastic perturbations to spacetime to effectively enforce a minimum length and establish a fundamental uncertainty at minimum length (ML) scale. To explore the symmetry of spacetime to such perturbations both in classical and quantum theories, we develop some new tools of stochastic calculus. We derive the generators of rotations and boosts, along with the connection, for stochastically perturbed, minimum length spacetime ("ML spacetime"). We find the metric, the directional derivative, and the canonical commutator preserved. ML spacetime follows the Lie algebra of the Poincare group, now expressed in terms of the two-point functions of the stochastic fields (per Ito's lemma). With the fundamental uncertainty at ML scale a symmetry of spacetime, we require the translational invariance of any classical theory in classical spacetime to also include the stochastic spacetime perturbations. As an application of these ideas, we consider galaxy rotation curves for massive bodies to find that—under the Robertson–Walker minimum length theory—rotational velocity becomes constant as the distance to the center of the galaxy becomes very large. The new tools of stochastic calculus also set the stage to explore new frontiers at the quantum level. We consider a massless scalar field to derive the Ward-like identity for ML currents. [ABSTRACT FROM AUTHOR]

Modified Newtonian dynamics (MOND) and similar proposals can (at least partially) explain the excess rotation of galaxies or the equivalent mass-discrepancy acceleration, without (or by reducing) the requirement of dark matter halos. This paper develops a modified gravity model to obtain local limit to the general relativity (GR) compatible with a cosmological metric different to the standard Friedmann–Lemaître–Robertson–Walker metric. Specifically, the paper uses a distorted stereographic projection of hyperconical universes, which are 4D hypersurfaces embedded into 5D Minkowski spacetime. This embedding is a key in the MOND effects found in galactic scales. To adequately describe the mass-discrepancy acceleration relation, centrifugal force would present a small time-like contribution at large-scale dynamics due to curvature of the Universe. Therefore, the Lagrangian density is very similar to the GR but with subtracting the background curvature (or vacuum energy density) of the perturbed hyperconical metric. Results showed that the proposed model adjusts well to 123 galaxy rotation curves obtained from the Spitzer Photometry and Accurate Rotation Curves database, using only a free parameter. [ABSTRACT FROM AUTHOR]

The myth of this "quasi-magical" gravity and its "effect at a distance" endures, and our brains remain "hardwired" to this perception. However, "quantum gravity" is increasingly closer to nullifying the importance of this mysterious force by treating it with the outmost contempt as a "negligible force." We concur with this interpretation, and more: We claim in this article that not only is gravity negligible but also explain how it can be completely eliminated as one of four fundamental forces of the universe. This article is, in fact, a continuation, a widening, and a confirmation of an article I wrote in 1993, titled "The proportional expansion of each and every celestial body as the cause of gravitation" [Phys. Essays 6, 473 (1993)]. There, I had argued that not only is empty space expanding in the classically understood sense, but that all celestial bodies are also subject to an accelerated expansion. According to Einstein's principle of equivalence, acceleration generates an opposite, "fictitious" force that is perceived as gravity. I had concluded there that "in terms of quantum mechanics, in this interpretation, the very existence of the predicted 'graviton' becomes extremely questionable." Thirty years have passed since then. And in spite of the development of the Large Hadron Collider and its impressive capabilities, the above claim has been confirmed, and the graviton has been quietly replaced by the Higgs boson in the nomenclature of the Standard Model of elementary particles. In this article, we revisit Galileo and Newton to show that the latter could not have arrived at any other conclusion than an "attractive" force of gravity. We also ask why Albert Einstein did not apply his own principle of equivalence to the Newtonian interpretation of gravity. At the same time, some very "peculiar" interpretations have arisen since my above-mentioned article from 1993. "Dark matter" and "dark energy," both very speculative conceptualizations, have been forced upon us to explain two phenomena: The anomaly discovered in the speed of rotation of the galaxies, and the accelerated expansion of the universe, despite the potentially shrinking effect of gravity. Of all the positive advances in physics, the most fundamental is the genesis of "quantum gravity," the tenets of which relegate gravity to the level of a "negligible" force. This is followed by the characterization of the Higgs boson, which has replaced the graviton in the Standard Model. This conceptually translates into the fact that the gravitational mass has possibly been replaced by the inertial mass of celestial bodies. The confirmation and measurements of the accelerated expansion of the universe, while there is still some controversies regarding the exact results of these measurements. Finally, the most important discovery in this regard was recently made in 2019, regarding the exceptionally high pressure inside protons and neutrons, (1035 Pa). This lends credence to the concept of the expansion of these subatomic particles. The multiplicity of these hadrons (3.26x1080) and their ubiquitous distribution in the baryonic matter of the entire universe explain its expansion. These hadrons are highly "diluted" in empty space but, on the contrary, are highly clustered and concentrated inside solid matter, where this explains the difference in density between these media and the massive dissimilarity in the magnitudes of their relative accelerated expansion. It also explains why what we call "gravity" is not an active force, but merely the consequence of the density-proportional accelerated radial expansion of each and every celestial body. As such, this baryonic expansion explains the expansion of the universe as a whole, and replaces gravity as a concept as well as its perceived effects. By dint of its ubiquitous nature, this notion of baryonic expansion provides a bridge between the microscopic and macroscopic universe. Quantum physics reconnects with general relativity in this formalism and clarifies the "what and how". [ABSTRACT FROM AUTHOR]

This is the second paper of the Mapping Nearby Galaxies at Apache Point Observatory (MaNGA) Dynamics and stellar Population (DynPop) series, which analyses the global stellar population, radial gradients, and non-parametric star-formation history of ∼10K galaxies from the MaNGA Survey final data release 17 and relates them with dynamical properties of galaxies. We confirm the correlation between the stellar population properties and the stellar velocity dispersion σe, but also find that younger galaxies are more metal-poor at fixed σe. Stellar age, metallicity, and mass-to-light ratio (M */ L) all decrease with increasing galaxy rotation, while their radial gradients become more negative (i.e. lower value at the outskirts). The exception is the slow rotators, which also appear to have significantly negative metallicity gradients, confirming the mass–metallicity gradient correlation. Massive disc galaxies in the green valley, on the |$(\sigma _{\rm e},\rm age)$| plane, show the most negative age and metallicity gradients, consistent with their old central bulges surrounded by young star-forming discs and metal-poor gas accretion. Galaxies with high σe, steep total mass-density slope, low dark matter fraction, high M */ L , and high metallicity have the highest star-formation rate at earlier times, and are currently quenched. We also discover a population of low-mass star-forming galaxies with low rotation but physically distinct from the massive slow rotators. A catalogue of these stellar population properties is provided publicly. [ABSTRACT FROM AUTHOR]

Galaxies have been observed to exhibit a level of simplicity unexpected in the complex galaxy formation scenario posited by standard cosmology. This is particularly apparent in their dynamics, where scaling relations display much regularity and little intrinsic scatter. However, the parameters responsible for this simplicity have not been identified. Using the Spitzer Photometry & Accurate Rotation Curves galaxy catalogue, we argue that the radial acceleration relation (RAR) between galaxies' baryonic and total dynamical accelerations is the fundamental 1D correlation governing the radial (in-disc) dynamics of late-type galaxies. In particular, we show that the RAR cannot be tightened by the inclusion of any other available galaxy property, that it is the strongest projection of galaxies' radial dynamical parameter space, and that all other statistical radial dynamical correlations stem from the RAR plus the non-dynamical correlations present in our sample. We further provide evidence that the RAR's fundamentality is unique in that the second most significant dynamical relation does not possess any of these features. Our analysis reveals the root cause of the correlations present in galaxies' radial dynamics: they are nothing but facets of the RAR. These results have important ramifications for galaxy formation theory because they imply that to explain statistically late-type galaxy dynamics within the disc it is necessary and sufficient to explain the RAR and lack of any significant, partially independent correlation. While simple in some modified dynamics models, this poses a challenge to standard cosmology. [ABSTRACT FROM AUTHOR]

This letter presents a mathematical model that may help address the long-standing problem of galaxy rotation curves. The strategy involves exploring the variation of circular velocity V with respect to radial distance 'r' as a result of which a Bessel differential equation is developed, yielding a general functional form of the potential as a Bessel function. Employing this potential in the case of galaxies, we find the velocity profile in terms of Bessel functions. This approach establishes Bessel functions as a powerful choice for investigating galactic rotation and deepening our understanding of the universe. [ABSTRACT FROM AUTHOR]

We investigate the properties of mergers comparable to the Gaia–Sausage–Enceladus (GSE) using cosmological hydrodynamical simulations of Milky Way-like galaxies. The merger progenitors span an order of magnitude in their peak stellar mass (⁠|$3\times 10^8\lt M_{\star }/\rm {M}_{\odot }\lt 4\times 10^9$|⁠) and include both rotation and pressure-supported galaxies (0.10 < D / T < 0.77). In a minority of cases, the GSE-like debris is comprised of stars from more than one merger progenitor. However, there is a close similarity in their chemodynamical properties and the triaxial shapes of their debris, and so it is not always possible to distinguish them. The merger progenitors host a variety of luminous satellites (0 and 8 with |$M_{\star }\gt 10^6\, \rm {M}_{\odot }$|⁠), but most of these do not follow the merger to low orbital energies. Between 0 and 1 of these satellites may survive to z  = 0, but with no clear signatures of their past association. We show that the fraction of stars originating from GSE-like mergers is reduced for lower metallicities (reaching a minimum around [Fe/H] = −2), and also within 5 kpc of the Galactic Centre. Whilst these central regions are dominated by in-situ stars, the ex-situ fraction trends towards a 100 per cent asymptote when considering the most metal-poor stars ([Fe/H] ≪ −2.5). Considering this, its near proximity, and its small volume on the sky, the Galactic Centre lends itself as a prime environment in the search for the stars from the earliest galaxies, whilst avoiding contamination from GSE stars. [ABSTRACT FROM AUTHOR]

We analysed the ionized gas kinematics of the dwarf galaxy NGC 4214 using high resolution Fabry–Perot interferometry observations and present a set of narrowband images in the Hα, [S  ii ] λ6717 Å, [N  ii ] λ6584 Å, and [O  iii ] λ5007 Å emission lines. The high-resolution Fabry–Perot observations of the Hα emission line, allowed us to derive the velocity field, the velocity dispersion σ, and the rotation curve of the galaxy. We also present for the first time, 3D kinematic maps of the complexes NGC 4214-I and NGC 4214-II and analysed the kinematics of the ionized gas of two new superbubbles, as well as the supernova remnants previously detected in this galaxy by other authors, in radio, optical, and X-ray emission. We computed the expansion velocities of the superbubbles and supernova remnants fitting their velocity profiles and obtained their respective physical parameters. We found that the superbubbles have an expansion velocity of ∼50 km s −1, dynamical age about ∼2 Myr and wind luminosity LW of ∼9 × 1038 erg s−1 produced probably by massive stars in OB associations. For supernova remnants, their expansion velocities are between ∼48 and ∼80 km s−1 with ages of about 104 yr and kinetic energy of about 1051 erg assuming they are in the radiative phase of evolution. [ABSTRACT FROM AUTHOR]

The kinetic Sunyaev–Zeldovich (kSZ) effect has now become a clear target for ongoing and future studies of the cosmic microwave background (CMB) and cosmology. Aside from the bulk cluster motion, internal motions also lead to a kSZ signal. In this work, we study the rotational kSZ effect caused by coherent large-scale motions of the cluster medium using cluster hydrodynamic cosmological simulations. To utilize the rotational kSZ as a cosmological probe, simulations offer some of the most comprehensive data sets that can inform the modelling of this signal. In this work, we use the MACSIS data set to investigate the rotational kSZ effect in massive clusters specifically. Based on these models, we test stacking approaches and estimate the amplitude of the combined signal with varying mass, dynamical state, redshift, and map-alignment geometry. We find that the dark matter, galaxy and gas spins are generally misaligned, an effect that can cause a suboptimal estimation of the rotational kSZ effect when based on galaxy motions. Furthermore, we provide halo-spin–mass scaling relations that can be used to build a statistical model of the rotational kSZ. The rotational kSZ contribution, which is largest in massive unrelaxed clusters (≳100  |$\mu$| K), could be relevant to studies of higher order CMB temperature signals, such as the moving lens effect. The limited mass range of the MACSIS sample strongly motivates an extended investigation of the rotational kSZ effect in large-volume simulations to refine the modelling, particularly towards lower mass and higher redshift, and provide forecasts for upcoming cosmological CMB experiments (e.g. Simons Observatory, SKA-2) and X-ray observations (e.g. Athena /X-IFU). [ABSTRACT FROM AUTHOR]

Recent independent observations using several different telescope systems and analysis methods have provided evidence of parity violation between the numbers of galaxies that spin in opposite directions. On the other hand, other studies argue that no parity violation can be identified. This paper provides detailed analysis, statistical inference, and reproduction of previous reports that show no preferred spin direction. Code and data used for the reproduction are publicly available. The results show that the data used in all of these studies agree with the observation of a preferred direction as observed from Earth. In some of these studies, the datasets were too small, or the statistical analysis was incomplete. In other papers, the results were impacted by experimental design decisions that led directly to showing nonpreferred direction. In some of these cases, these decisions were not stated in the papers but were revealed after further investigation in cases where the reproduction of the work did not match the results reported in the papers. These results show that the data used in all of these previous studies, in fact, agree with the contention that galaxies as observed from Earth have a preferred spin direction, and the distribution of galaxy spin directions as observed from Earth forms a cosmological-scale dipole axis. This study also shows that the reason for the observations is not necessarily an anomaly in the large-scale structure, and can also be related to internal structure of galaxies. [ABSTRACT FROM AUTHOR]

Galaxy rotation curve (RC) fitting is an important technique which allows the placement of constraints on different kinds of dark matter (DM) halo models. In the case of non-phenomenological DM profiles with no analytic expressions, the art of finding RC best-fits including the full baryonic + DM free parameters can be difficult and time-consuming. In the present work, we use a gradient descent method used in the backpropagation process of training a neural network, to fit the so-called Grand Rotation Curve of the Milky Way (MW) ranging from ∼1 pc all the way to ∼ 10 5 pc. We model the mass distribution of our Galaxy including a bulge (inner + main), a disk, and a fermionic dark matter (DM) halo known as the Ruffini-Argüelles-Rueda (RAR) model. This is a semi-analytical model built from first-principle physics such as (quantum) statistical mechanics and thermodynamics, whose more general density profile has a dense core–diluted halo morphology with no analytic expression. As shown recently and further verified here, the dark and compact fermion-core can work as an alternative to the central black hole in SgrA* when including data at milliparsec scales from the S-cluster stars. Thus, we show the ability of this state-of-the-art machine learning tool in providing the best-fit parameters to the overall MW RC in the 10 − 2 – 10 5 pc range, in a few hours of CPU time. [ABSTRACT FROM AUTHOR]

In this paper we analyse a sample of 46 barred galaxies of MaNGA. Our goal is to investigate the stellar kinematics of these galaxies and obtain their rotation curves. Additionally, we aim to derive the total stellar and dynamical masses, as well as the maximum rotation velocity, in order to examine their distributions and scaling relations. Using the Pipe3D dataproducts publicly available we obtained the rotation curves, which were fitted considering two components of an axisymmetric Miyamoto–Nagai gravitational potential. We found a wide range of the maximum rotation velocities (117–340  |${\rm km\, s^{-1}}$|⁠), with a mean value of 200  |${\rm km\, s^{-1}}$|⁠. In addition we found that the total stellar and dynamical masses are in the range of log(M star /M⊙) = 10.1−11.5, with a mean value of log(M star /M⊙) = 10.8, and log(M dyn /M⊙) = 10.4−12.0, with a mean value of log(M dyn /M⊙) = 11.1, respectively. We found a strong correlation between dynamical mass and maximum velocity, between maximum velocity and magnitude, and between stellar mass and maximum velocity. According to these results, barred galaxies exhibit similar behaviour to that of normal spiral galaxies with respect to these relations, as well as in terms of the distribution of their dynamical mass and maximum rotation velocity. However, we found that the distribution of stellar masses of barred galaxies is statistically different from other samples including non-barred galaxies. Finally, analysing the galaxies that show nuclear activity, we find no difference with the rotation curves of normal galaxies. [ABSTRACT FROM AUTHOR]

Using the PMAS Integral Field Unit on the Calar Alto 3.5 m telescope, we observed the southern component (Markarian 59) of the 'cometary' starburst galaxy NGC 4861. Mrk 59 is centred on a giant nebula and concentration of stars 1 kpc in diameter. Strong |$\rm H\,\alpha$| emission points to a star-formation rate (SFR) at least 0.47  |$\rm M_{\odot }\, yr^{-1}$|⁠. Mrk 59 has a very high [O  iii ] |$\rm \lambda 5007/H\,\beta$| ratio, reaching 7.35 in the central nebula, with a second peak at a star-forming hotspot further north. Fast outflows are not detected but nebular motion and galaxy rotation produce relative velocities up to 40 km  |$\rm s^{-1}$|⁠. Spectral analysis of different regions with 'Fitting Analysis using Differential evolution Optimization' (FADO) finds that the stars in the central and 'spur' nebulae are very young, |$\rm \le 125~Myr$| with a large |$\rm \lt 10~Myr$| contribution. Older stars (⁠|$\rm \sim 1~Gyr$|⁠) make up the northern disk component, while the other regions show mixtures of 1 Gyr age with very young stars. This and the high specific SFR |$\rm \sim 3.5~Gyr^{-1}$| imply a bimodal star formation history, with Mrk 59 formed in ongoing starbursts fuelled by a huge gas inflow, turning the galaxy into an asymmetric 'green pea' or blue compact dwarf. We map the He  ii  λ4686 emission, and identify a broad component from the central nebula, consistent with the emission of ∼300 Wolf–Rayet stars. About a third of the He  ii  λ4686 flux is a narrow line emitted from a more extended area covering the central and spur nebulae, and may have a different origin. [ABSTRACT FROM AUTHOR]

We present an analysis of nearly 1000 near-infrared, integrated-light spectra from APOGEE in the inner ∼7 kpc of M31. We utilize full-spectrum fitting with A-LIST simple stellar population spectral templates that represent a population of stars with the same age, [M/H], and [ α /M]. With this, we determine the mean kinematics, metallicities, α abundances, and ages of the stellar populations of M31's bar, bulge, and inner disk (∼4–7 kpc). We find a nonaxisymmetric velocity field in M31 resulting from the presence of a bar. The bulge of M31 is less metal-rich (mean [M/H] = − 0.149 − 0.081 + 0.067 dex) than the disk, features minima in metallicity on either side of the bar ([M/H] ∼ −0.2), and is enhanced in α abundance (mean [ α /M] = 0.281 − 0.038 + 0.035 ). The disk of M31 within ∼7 kpc is enhanced in both metallicity ([M/H] = − 0.023 − 0.052 + 0.050 ) and α abundance ([ α /M] = 0.274 − 0.025 + 0.020 ). Both of these structural components are uniformly old at ≃12 Gyr. We find the mean metallicity increases with distance from the center of M31, with the steepest gradient along the disk major axis (0.043 ± 0.021 dex kpc−1). This gradient is the result of changing light contributions from the bulge and disk. The chemodynamics of stellar populations encodes information about a galaxy's chemical enrichment, star formation history, and merger history, allowing us to discuss new constraints on M31's formation. Our results provide a stepping stone between our understanding of the Milky Way and other external galaxies. [ABSTRACT FROM AUTHOR]

It is routinely assumed that galaxy rotation curves are equal to their circular velocity curves (modulo some corrections) such that they are good dynamical mass tracers. We take a visualization-driven approach to exploring the limits of the validity of this assumption for a sample of 33 low-mass galaxies (⁠|$60\lt v_\mathrm{max}/\mathrm{km}\, \mathrm{s}^{-1}\lt 120$|) from the APOSTLE suite of cosmological hydrodynamical simulations. Only three of these have rotation curves nearly equal to their circular velocity curves at z  = 0, the rest are undergoing a wide variety of dynamical perturbations. We use our visualizations to guide an assessment of how many galaxies are likely to be strongly perturbed by processes in several categories: mergers/interactions (affecting 6/33 galaxies), bulk radial gas inflows (19/33), vertical gas outflows (15/33), distortions driven by a non-spherical DM halo (17/33), warps (8/33), and winds due to motion through the intergalactic medium (5/33). Most galaxies fall into more than one of these categories; only 5/33 are not in any of them. The sum of these effects leads to an underestimation of the low-velocity slope of the baryonic Tully–Fisher relation (α ∼ 3.1 instead of α ∼ 3.9, where M bar ∝  v α) that is difficult to avoid, and could plausibly be the source of a significant portion of the observed diversity in low-mass galaxy rotation curve shapes. [ABSTRACT FROM AUTHOR]

Despite over a century of research, the physics of galaxy rotation is not yet fully understood, and there is a clear discrepancy between the observed mass of galaxies and their rotational velocity. Here, we report on another observation of tension between the physical properties of galaxies and their rotational velocity. We compare the apparent magnitude of galaxies and find a statistically significant asymmetry between galaxies that rotate in the same direction relative to the Milky Way and galaxies that rotate in the opposite direction relative to the Milky Way. While asymmetry in the brightness is expected due to the Doppler shift effect, such asymmetry is expected to be subtle. The observations shown here suggest that the magnitude difference is sufficiently large to be detected by Earth-based telescopes. The asymmetry is consistent in both the northern and southern galactic poles. The difference is also consistent across several different instruments such as DECam, SDSS, Pan-STARRS, and HST as well as different annotation methods, which include automatic, manual, or crowdsourcing annotations through "Galaxy Zoo". The observation can also explain other anomalies such as the H o tension. Analysis of Ia supernovae where the host galaxies rotate in the same direction relative to the Milky Way shows a much smaller tension with the H o value as estimated by the CMB. [ABSTRACT FROM AUTHOR]

We study the dependence of the kinematic properties of the subsystems of Galactic open clusters on their ages. It was found that the angular velocity of Galactic rotation in the solar vicinity decreases to 25.6 km s kpc for clusters older than 600 Myrs. According to the rotation curves of the Galaxy for different age intervals at a galactocentric distance of 6.0 to 13.0 kpc, it is found that older open clusters rotate much more slowly than young and middle-aged clusters. The rotation curve decreases with increasing galactocentric distance in the entire distance interval under consideration. We can observe the separation of open clusters into thick and thin disk objects. A near-sinusoidal dependence of the radial cluster velocity component on galactocentric distance is obtained for distances ranging from 6.0 to 13.0 kpc. No dependence of the vertical velocity component on galactocentric distance is found. [ABSTRACT FROM AUTHOR]

We use ΛCDM cosmological hydrodynamical simulations to explore the kinematics of gaseous discs in late-type dwarf galaxies. We create high-resolution 21-cm 'observations' of simulated dwarfs produced in two variations of the EAGLE galaxy formation model: one where supernova-driven gas flows redistribute dark matter and form constant-density central 'cores', and another where the central 'cusps' survive intact. We 'observe' each galaxy along multiple sightlines and derive a rotation curve for each observation using a conventional tilted-ring approach to model the gas kinematics. We find that the modelling process introduces systematic discrepancies between the recovered rotation curve and the actual circular velocity curve driven primarily by (i) non-circular gas orbits within the discs; (ii) the finite thickness of gaseous discs, which leads to overlap of different radii in projection; and (iii) departures from dynamical equilibrium. Dwarfs with dark matter cusps often appear to have a core, whilst the inverse error is less common. These effects naturally reproduce an observed trend which other models struggle to explain: late-type dwarfs with more steeply rising rotation curves appear to be dark matter-dominated in the inner regions, whereas the opposite seems to hold in galaxies with core-like rotation curves. We conclude that if similar effects affect the rotation curves of observed dwarfs, a late-type dwarf population in which all galaxies have sizeable dark matter cores is most likely incompatible with current measurements. [ABSTRACT FROM AUTHOR]

We propose to test the viability of the recently introduced f (R) gravity model in the galactic scales. For this purpose we consider test particles moving in stable circular orbits around the galactic center. We study the Palatini approach of f (R) gravity via Weyl transformation, which is the frame transformation from the Jordan frame to the Einstein frame. We derive the expression of rotational velocities of test particles in the new f (R) gravity model. For the observational data of samples of high surface brightness and low surface brightness galaxies, we show that the predicted rotation curves are well fitted with observations, thus implying that this model can explain flat rotation curves of galaxies. We also study an ultra diffuse galaxy, AGC 242019 which has been claimed in literature to be a dark matter dominated galaxy similar to low surface brightness galaxies with a slowly rising rotation curve. The rotation curve of this galaxy also fits well with the model prediction in our study. Furthermore, we studied the Tully–Fisher relation for the entire sample of galaxies and found that the model prediction shows the consistency with the data. [ABSTRACT FROM AUTHOR]

Context. Early-type galaxies (ETGs) are divided into slow and fast rotators (FRs and SRs) according to the degree of ordered rotation of their stellar populations. Cosmological hydrodynamical simulations indicate that galaxies form as FRs before their rotational support decreases, usually because of mergers. Aims. We aimed to investigate this process observationally for galaxies outside of clusters. Methods. We made use of the fact that different merger types leave different traces that have different lifetimes. We statistically analyzed multiple characteristics of galaxies that are expected to be influenced by mergers, such as tidal features, kinematically distinct cores, and stellar ages. They were taken from the MATLAS and ATLAS3D databases. Through multilinear regression we identified the quantities that, at a fixed mass and environmental density of the galaxy, significantly correlate with a measure of the ordered rotation of the galaxy, -NR e. Results. We found a negative correlation of the rotational support with the occurrence of tidal disturbances and kinematic substructures, and a positive correlation with metallicity and metallicity gradients. For massive galaxies, the rotational support correlates negatively with the abundance of α-elements, and for the galaxies in low-density environments, it correlates negatively with the central photometric cuspiness. These and additional literature observational constraints are explained the easiest if the mergers that decreased the rotational support of ETGs were typically minor, wet, and happening at z 2. They did not form the currently observed tidal features. The observed frequency of tidal features implies a merging rate of 0.07-0.2 per Gyr. This is insuffcient to explain the observed growth of the radii of ETGs with redshift by mergers. [ABSTRACT FROM AUTHOR]

We write the Kerr–Schild tetrads in terms of the flat space–time tetrads and of a (1, 1) tensor S μ λ . This tensor can be considered as a projection operator, since it transforms (i) flat space–time tetrads into non-flat tetrads, and vice-versa, and (ii) the Minkowski space–time metric tensor into a non-flat metric tensor, and vice-versa. The S μ λ tensor and its inverse are constructed in terms of the standard null vector field l μ that defines the Kerr–Schild form of the metric tensor in general relativity, and that yields black holes and non-linear gravitational waves as solutions of the vacuum Einstein's field equations. We demonstrate that the condition for the vanishing of the Ricci tensor obtained by Kerr and Schild, in empty space–time, is also a condition for the vanishing of the Nijenhuis tensor constructed out of S μ λ . Thus, a theory based on the Nijenhuis tensor yields an important class of solutions of the Einstein's field equations, namely, black holes and non-linear gravitational waves. We also demonstrate that the present mathematical framework can easily admit modifications of the Newtonian potential that may explain the long range gravitational effects related to galaxy rotation curves. [ABSTRACT FROM AUTHOR]

Logarithmic superfluid theory of physical vacuum suggests that gravity has a multiple-scale structure, where one can recognise sub-Newtonian, Newtonian, logarithmic, linear and quadratic (de Sitter) terms in the induced space–time metric and effective potential. To test the theory's predictions on a galactic scale, we apply best-fitting procedures to the rotation curve data obtained from 15 galaxies by the HI Nearby Galaxy Survey, assuming their stellar disk's parameters to be fixed to the mean values measured using photometric methods. Although the fitting results seem to be sensitive to the stellar disk model chosen, they correspond closely with the observational data, even for those galaxies for which the rotation velocity profiles do not have flat regions. [ABSTRACT FROM AUTHOR]

We present multiwavelength time-series spectroscopy of SN 2013aa and SN 2017cbv, two Type Ia supernovae (SNe Ia) on the outskirts of the same host galaxy, NGC 5643. This work utilizes new nebular-phase near-infrared (NIR) spectra obtained by the Carnegie Supernova Project-II, in addition to previously published optical and NIR spectra. Using nebular-phase [Fe ii ] lines in the optical and NIR, we examine the explosion kinematics and test the efficacy of several common emission-line-fitting techniques. The NIR [Fe ii ] 1.644 μ m line provides the most robust velocity measurements against variations due to the choice of the fit method and line blending. The resulting effects on velocity measurements due to choosing different fit methods, initial fit parameters, continuum and line profile functions, and fit region boundaries were also investigated. The NIR [Fe ii ] velocities yield the same radial shift direction as velocities measured using the optical [Fe ii ] λ 7155 line, but the sizes of the shifts are consistently and substantially lower, pointing to a potential issue in optical studies. The NIR [Fe ii ] 1.644 μ m emission profile shows a lack of significant asymmetry in both SNe, and the observed low velocities elevate the importance for correcting for any velocity contribution from the host galaxy's rotation. The low [Fe ii ] velocities measured in the NIR at nebular phases disfavor progenitor scenarios in close double-degenerate systems for both SN 2013aa and SN 2017cbv. The time evolution of the NIR [Fe ii ] 1.644 μ m line also indicates moderately high progenitor white dwarf central density and potentially high magnetic fields. [ABSTRACT FROM AUTHOR]

Galaxies show different halo scaling relations such as the radial acceleration relation, the mass discrepancy acceleration relation (MDAR), or the dark matter (DM) surface density relation. At difference with traditional studies using phenomenological ΛCDM halos, we analyze the above relations assuming that DM halos are formed through a maximum entropy principle (MEP) in which the fermionic (quantum) nature of the DM particles is dully accounted for. For the first time, a competitive DM model based on first physical principles, such as (quantum) statistical-mechanics and thermodynamics, is tested against a large data set of galactic observables. In particular, we compare the fermionic DM model with empirical DM profiles: the Navarro–Frenk–White (NFW) model, a generalized NFW model accounting for baryonic feedback, the Einasto model, and the Burkert model. For this task, we use a large sample of 120 galaxies taken from the Spitzer Photometry and Accurate Rotation Curves data set, from which we infer the DM content to compare with the models. We find that the radial acceleration relation and MDAR are well explained by all the models with comparable accuracy, while the fits to the individual rotation curves, in contrast, show that cored DM halos are statistically preferred with respect to the cuspy NFW profile. However, very different physical principles justify the flat inner-halo slope in the most-favored DM profiles: while generalized NFW or Einasto models rely on complex baryonic feedback processes, the MEP scenario involves a quasi-thermodynamic equilibrium of the DM particles. [ABSTRACT FROM AUTHOR]

In this paper, we present our calibrations of the Tully–Fisher relation in the mid-infrared W 1 (3.4  |$\mu$| m) and W 2 (4.6   |$\mu$| m) bands, using large samples of 877 galaxies and 876 galaxies from 31 clusters in the W 1 and W 2 bands, respectively. Using a new, iterative bivariate fitting procedure we performed two corrections, one for the cluster population incompleteness bias and a second morphological type correction. We initially performed calibrations using total absolute magnitudes and H  i line widths W F 50 derived from the H  i global profiles as a measure of rotational velocity. We then used (i) isophotal magnitudes and (ii) average rotational velocities measured along the flat sections of the spatially resolved rotation curves of the galaxies, which were obtained from the empirical conversion between rotational velocity definitions. We determined that the calibrations using total magnitudes and H  i line widths had smaller total scatter around the TF relations in the W1 and W2 bands than those using either isophotal magnitudes or spatially resolved rotational velocities. These calibrations are M Tot,W1 = (1.77 ± 0.40) − (9.99 ± 0.16)log10(W F 50) and M Tot,W2 = (2.03 ± 0.40) − (10.12 ± 0.16)log10(W F 50), with associated total scatters of σ W 1 = 0.66 and σ W 2 = 0.67. We compared these with previous calibrations in the near-infrared J, H , and K bands and the long-wavelength optical I band which used the same two corrections. The differences between calibrations can be explained by considering the different regions and components of spiral galaxies that are traced by the different wavelengths. The codes used for the calibrations of the Tully–Fisher relation are available from https://github.com/RiannaBell/WISE-TF-Calibration. [ABSTRACT FROM AUTHOR]

We present the results from the analysis of galaxy rotation curves with Verlinde's emergent gravity. We use the data in the Spitzer Photometry and Accurate Rotation Curves database, which contains a sample of 175 nearby disk galaxies with 3.6 µ m surface photometry and rotation curves. We compute the gravitational acceleration at different galactocentric radii expected from the baryon distribution of the galaxies with the emergent gravity, and compare it with the observed gravitational acceleration derived from galactic rotation curves. The predicted and observed accelerations agree well with a mean offset μ [ l o g (g o b s ) − l o g (g V e r ) ] = − 0.060 ± 0.004 and a scatter σ [ l o g (g o b s ) − l o g (g V e r ) ] = 0.137 ± 0.004 by assuming a de Sitter Universe. These offset and scatter become smaller when we assume a more realistic Universe, quasi de Sitter Universe, as μ = − 0.027 ± 0.003 and σ = 0.129 ± 0.003. Our results suggest that Verlinde's emergent gravity could be a good solution to the missing mass problem without introducing dark matter. [ABSTRACT FROM AUTHOR]

The reconstruction of Faraday depth structure from incomplete spectral polarization radio measurements using the RM synthesis technique is an underconstrained problem requiring additional regularization. In this paper, we present cs-romer : a novel object-oriented compressed sensing framework to reconstruct Faraday depth signals from spectropolarization radio data. Unlike previous compressed sensing applications, this framework is designed to work directly with data that are irregularly sampled in wavelength-squared space and to incorporate multiple forms of compressed sensing regularization. We demonstrate the framework using simulated data for the VLA telescope under a variety of observing conditions, and we introduce a methodology for identifying the optimal basis function for reconstruction of these data, using an approach that can also be applied to data sets from other telescopes and over different frequency ranges. In this work, we show that the delta basis function provides optimal reconstruction for VLA L -band data and we use this basis with observations of the low-mass galaxy cluster Abell 1314 in order to reconstruct the Faraday depth of its constituent cluster galaxies. We use the cs-romer framework to de-rotate the Galactic Faraday depth contribution directly from the wavelength-squared data and to handle the spectral behaviour of different radio sources in a direction-dependent manner. The results of this analysis show that individual galaxies within Abell 1314 deviate from the behaviour expected for a Faraday-thin screen such as the intra-cluster medium and instead suggest that the Faraday rotation exhibited by these galaxies is dominated by their local environments. [ABSTRACT FROM AUTHOR]

This work aims to explore some dynamic aspects of the problem of star motion that is impacted by the rotation of the galaxy, which we model as a bisymmetric potential based on a two-dimensional harmonic oscillator with sextic perturbations. We demonstrate analytically that the motion is non-integrable when certain conditions are met. The analytical results for the non-integrability are confirmed by showing the irregularity of the behavior of the motion through utilizing the Poincaré surface of a section as a numerical method. The motion equilibrium positions are detected, and their stability is discussed. We show that the force generated by the rotating frame acts as a stabilizer for the maximum equilibrium points. We display graphically that the size of the stability regions relies on the angular velocity magnitude for the frame. Through the application of Lyapunov's theorem, periodic solutions can be constructed which are close to the equilibrium positions. Furthermore, we demonstrate that there are one or two families of periodic solutions relying on whether the equilibrium point is a saddle or stable, respectively. [ABSTRACT FROM AUTHOR]

We present a didactic approach to the concept of dark matter that can be used in secondary schools. Evidence for dark matter is studied by analyzing galaxy rotation curves, using only elements that are already familiar to the students: mechanics of the uniform circular motion, basic concepts of Newtonian gravitation and Kepler's third law. We also report on an application of this approach. [ABSTRACT FROM AUTHOR]

We apply a statistical deconvolution of the parallax errors based on Lucy's inversion method (LIM) to the Gaia DR3 sources to measure their 3D velocity components in the range of Galactocentric distances R between 8 and 30 kpc with their corresponding errors and rms values. We find results that are consistent with those obtained by applying LIM to the Gaia DR2 sources, and we conclude that the method gives convergent and more accurate results by improving the statistics of the data set and lowering observational errors. The kinematic maps reconstructed with LIM up to R ≈ 30 kpc show that the Milky Way is characterized by asymmetrical motions with significant gradients in all velocity components. Furthermore, we determine the Galaxy rotation curve V C (R) up to ≈27.5 kpc with the cylindrical Jeans equation assuming an axisymmetric gravitational potential. We find that V C (R) is significantly declining up to the largest radius investigated. Finally, we also measure V C (R) at different vertical heights, showing that, for R < 15 kpc, there is a marked dependence on Z, whereas at larger R the dependence on Z is negligible. [ABSTRACT FROM AUTHOR]