Narrow Results

We review results from recent high resolution cosmological structure formation simulations, namely the Via Lactea I & II and GHALO projects. These simulations study the formation of Milky Way sized objects within a cosmological framework. We discuss the general properties of cold dark matter halos at redshift z = 0 and focus on new insights into the structure of halos we got due to the unprecedented high resolution in these simulations.

We show that the generally held view that the gravity of weak-field nonrelativistic-velocity sources being invariably almost equivalent to Newtonian gravity (NG) (the “Newtonian limit” approach) is in some instances misleading and in other cases incorrect. A particularly transparent example is provided by comparing the Newtonian and general relativistic analyses of a simple variant of van Stockum’s infinite rotating dust cylinder. We show that some very recent criticisms of our work that had been motivated by the Newtonian limit approach were incorrect and note that no specific errors in our work were found in the critique. In the process, we underline some problems that arise from inappropriate coordinate transformations. As further support for our methodology, we note that our weak-field general relativistic treatment of a model galaxy was vindicated recently by the observations of Xu et al. regarding our prediction that the Milky Way was 19–21 kpc in radius as opposed to the commonly held view that the radius was 15 kpc.

The history of science can be recounted in many ways: by addressing the work of one person or school; by starting with the ancients and working chronologically up to the present; by focusing on a particular century; or by tracing a particular important idea as far back and forward as it can be found. The present discussion does none of these. Rather, it adopts the ordering of a standard introductory astronomy textbook, from the solar system via stars and galaxies, to the universe as a whole, and in each regime picks out a few issues that were controversial or wrongly decided for a long time. For each, I attempt to identify a duration of the period of uncertainty or error and some of the causes of the confusion. This is surely not an original idea, though I am not aware of having encountered it elsewhere, and it is not one that is likely to appeal to most 21st century historians of science, for whom the question "Who first got it right?" is not necessarily an important, or even appropriate, one. Some of the stories have been told as historical introductions to conferences and are here summarized and brought up to date. Others I had not previously addressed.

We test precision of the Cosmological Paczynski–Wiita (CPW) potential reflecting properties of the Schwarzschild–de Sitter (SdS) spacetimes in modeling dynamical phenomena related to galaxy motion. We consider a simplified model of Magellanic Clouds moving in the field of Milky Way as test particles. Time evolution of their position along trajectories obtained in the CPW framework using the notion of Newtonian time is compared to the one obtained in the fully general relativistic (GR) approach when the time evolution is expressed in terms of time related to the location of Earth in the Galaxy field. The differences in the position-evolution of the Magellanic Clouds obtained in the CPW and GR approaches are given for appropriately chosen values of the Milky Way mass. It is shown that the integrated relativistic corrections represent ~10^-5 part of the Newtonian CPW predictions for the orbital characteristics of the motion and slightly grow with Galaxy mass growing, being at least by one order higher than the local scaling GR corrections. The integrated orbital GR corrections thus could be important only in very precise modeling of the motion of Magellanic Clouds. The CPW framework is used to show that, quite surprisingly, the influence of the cosmological constant on the Magellanic Clouds motion can be strong and significantly alters the trajectories of Magellanic Clouds and time evolution along them. The relative contribution of the cosmological constant is ~10^-1 or higher. It is most profoundly demonstrated by the increase of the binding mass that represents 22% for Small Magellanic Cloud and even 47% for Large Magellanic Cloud, putting serious doubts on gravitational binding to the Milky Way in the later case.

In this paper, we focus on the astrophysical results and the related cosmological implications derived from recent microwave surveys, with emphasis to those coming from the Planck mission. We critically discuss the impact of systematic effects and the role of methods to separate the cosmic microwave background (CMB) signal from the astrophysical emissions and each different astrophysical component from the others. We then review the state-of-the-art diffuse emissions, extragalactic sources, cosmic infrared background and galaxy clusters, addressing the information they provide to our global view of the cosmic structure evolution and for some crucial physical parameters, as the neutrino mass. Finally, we present three different kinds of scientific perspectives for fundamental physics and cosmology offered by the analysis of on-going and future CMB projects at different angular scales dedicated to anisotropies in total intensity and polarization and to absolute temperature.

We provide a description of the latest status and performance of the Planck satellite, focusing on the final predicted sensitivity of Planck. The optimization of the observational strategy for the additional surveys following the nominal 15 months of integration (about two surveys) originally allocated and the limitation represented by astrophysical foreground emissions are presented. An outline of early and intermediate astrophysical results from the Planck Collaboration is provided. A concise view of some fundamental cosmological results that will be achieved by exploiting Planck's full set of temperature and polarization data are presented. Finally, the perspectives opened by Planck in answering some key questions in fundamental physics, with particular attention to parity symmetry analyses, are described.

Using GAIA EDR3 catalog, we present the detailed analysis of the two-component Milky Way stellar disk in the solar neighborhood. To determine the kinematical properties of the thin and of the Thick disks, we select the complete sample of about 278,000 evolved red giant branch (RGB) stars distributed in the cylinder of 1 kpc radius and 0.5 kpc height centered at the Sun. We measured the following mean velocities and dispersions for the thin and the Thick disks, respectively: $(V_R,V_{\varphi },V_Z)=(-1,-239,0)$km s${}^{-1}$ with $({\sigma }_R,{\sigma }_{\varphi },{\sigma }_Z)=(31,20,11)$km s${}^{-1}$, and $(V_R,V_{\varphi },V_Z)=(+1,-225,0)$km s${}^{-1}$ with $({\sigma }_R,{\sigma }_{\varphi },{\sigma }_Z)=(49,35,22)$km s${}^{-1}$. Errors in mean velocities and dispersions are all less than 1km s${}^{-1}$. Same values were computed on much smaller subsamples of our Gaia data with RAVE DR5 [Fe/H] values, from which a metallicity selection was added. Results are basically the same. We find that up to 500 pc height above/below the galactic plane, Thick disk stars comprise about half the stars of the disk. We also find evidence of a substructure in $Z$ versus $V_Z$ in the thick disk population mostly that would give support to the accretion scenario for the formation of the thick disk.

The GAIA DR3 measurement campaign has produced a MW rotation curve with significantly improved accuracy compared with previous campaigns. In 2023, several authors presented accurate rotation curves calculated from these measurements, within the framework of the dark matter hypothesis. They established new estimates of the Milky Way’s dynamical mass of around $2\times {10}^{11}{M}_{\odot }$. Some of these authors showed that, from a radial distance of around 18kpc, the Milky Way presents a significant Keplerian decay in the rotation curve, rather than a plateau zone. In this paper, we use a set of data tables from four different authors in a single database. Without making any assumptions about the existence or absence of dark matter, we analyze the observed radial acceleration as a function of the baryonic acceleration. We show that the observed acceleration is an accurate linear function of the baryonic acceleration, making the dark matter hypothesis problematic. Furthermore, we prove that the MW rotation curve can be calculated within the framework of General Relativity without dark matter, using the dynamic metric we published earlier in 2023: “On the incompleteness’ of Birkhoff’s theorem: A new approach to the central symmetric Gravitational Field in Vacuum Space.” In particular, this metric allows us to predict and model the Keplerian decay zone of the rotation curve. Our dynamical mass evaluation does not differ significantly from the value $2\times 10^{11}{M}_{\odot }$.

In the scalar theory of gravitation with a preferred reference frame, a consistent formulation of electrodynamics in the presence of gravitation needs to introduce an additional energy tensor: the interaction energy tensor. This energy is gravitationally active and might contribute to the dark matter, because it has an exotic character and it is not localized inside matter. In order to check if that energy might form representative dark halos, one has to model the interstellar radiation field in a galaxy as a complete electromagnetic field obeying the Maxwell equations. A model has been built for this purpose, based on assuming axial symmetry and on recent results about axisymmetric Maxwell fields. Its predictions for the variation of the spectral energy density inside our Galaxy are relatively close to those of a recent radiation transfer model, except on the symmetry axis of the Galaxy, where the present model predicts extremely high values of the energy density.

The characteristics of the largely-unidentified Galactic sources of gamma rays that were detected by EGRET are reviewed. Proposed source populations that may have the correct spatial, spectral, luminosity, and variability properties to be the origins of the EGRET sources are also presented. Finally, the prospects for studying Galactic gamma-ray sources with the GLAST LAT are reviewed.

Every star-forming galaxy is thought to host a large-scale population of cosmic rays accelerated in the various astrophysical shocks that accompany the evolution of massive stars from the main sequence to the compact remnant. As they propagate in the interstellar medium, these non-thermal particles radiate in the radio and gamma-ray bands through interactions with matter and radiation fields. The resulting diffuse glow bears the marks of the cosmic-ray acceleration and transport processes, and the comparison of the emissions from different galactic systems thus can provide insights into both aspects of the cosmic-ray phenomenon. Such a population study was however not possible before the LAT gamma-ray telescope onboard the Fermi satellite came into operation about two years ago. In this paper, we review the detections of external star-forming systems achieved by the Fermi/LAT so far, and we emphasise how these observations hold potential for improving our understanding of galactic cosmic rays.

In over two years of operation Fermi-LAT has revolutionized our knowledge of the gamma-ray sky. Interstellar gamma rays are part of this new era and allow unprecedented tests for models of cosmic rays in the Galaxy. The extension to lower energies with INTEGRAL/SPI data is also evolving. The global multi-wavelength luminosity of the Milky Way has been derived, with implications for the Galactic energy balance and the radio-FIR correlation.

We provide a description of the latest status and performance of the Planck satellite, focusing on the final predicted sensitivity of Planck. The optimization of the observational strategy for the additional surveys following the nominal fifteen months of integration (about two surveys) originally allocated and the limitation represented by astrophysical foreground emissions are presented. An outline of early and intermediate astrophysical results from the Planck Collaboration is provided. A concise view of some fundamental cosmological results that will be achieved by exploiting Planck's full set of temperature and polarization data is presented. Finally, the perspectives opened by Planck in answering some key questions in fundamental physics, with particular attention to Parity symmetry analyses, are described.

In this article we focus on the astrophysical results and the related cosmological implications derived from recent microwave surveys, with emphasis to those coming from the Planck mission. We critically discuss the impact of systematics effects and the role of methods to separate the cosmic microwave background signal from the astrophysical emissions and each different astrophysical component from the others. We then review of the state of the art in diffuse emissions, extragalactic sources, cosmic infrared background, and galaxy clusters, addressing the information they provide to our global view of the cosmic structure evolution and for some crucial physical parameters, as the neutrino mass. Finally, we present three different kinds of scientific perspectives for fundamental physics and cosmology offered by the analysis of on-going and future cosmic microwave background projects at different angular scales dedicated to anisotropies in total intensity and polarization and to absolute temperature.

Using the pseudo-Newtonian (PN) potential, we estimate the influence of the repulsive cosmological constant Ʌ ~ 1.3×10^–56cm^–2 implied by recent cosmological tests onto the motion of both Small and Large Magellanic Clouds (SMC and LMC) in the gravitational field of the Milky Way. The role of the cosmological constant is most conspicuous when binding mass is estimated for the satellite galaxies. We have found a strong influence of cosmic repulsion on the total binding mass for both galaxies. We have found that in some cases, the effect of the cosmic repulsion can be even comparable to the effects of the dynamical friction and the Andromeda galaxy.

These are promising times for the study of cosmic microwave background and foregrounds. While, at the date of this meeting, WMAP is close to release its final maps and products, Planck early and intermediate results have been presented with the first release of the compact source catalog, and the presentation of the first cosmological products is approaching. This parallel session is focussed on the astrophysical sky as seen by Planck and other observatories, and on their scientific exploitation, regarding diffuse emissions, sources, galaxy clusters, cosmic infrared background, as well as on critical issues coming from systematic effects and data analysis, in the view of fundamental physics and cosmology perspectives. At the same time, a new generation of CMB anisotropy and polarization experiments is currently operated using large arrays of detectors, boosting the sensitivity and resolution of the surveys to unprecedented levels. Mainstream projects are observations of the polarization of the CMB, looking for the inflationary B-modes at large and intermediate angular scales, fine-scale measurements of the Sunyaev-Zel'dovich effect in clusters of galaxies, and the precise measure of CMB spectrum.