Das dunkle Universum im Lichte seiner Morphologie
Zusammenfassung der Projektergebnisse
The cosmological model that is currently assumed relates the structure in the early Universe, observed in the microwave radiation constituting the cosmic microwave background (CMB), to the structure in the late Universe, observed in galaxy redshift surveys. In order for the two observations to match, the current cosmological model needs to introduce energy components of yet unknown physical origin, namely dark energy and dark matter. To understand the physical nature of these components, more information about their properties are necessary. This can be achieved by more and more precise tests of the current concordance model. To arrive at these more precise tests two routes are possible: One can either collect more data and apply the current statistical tools to it, or one can improve those tools to extract more information from the currently available data. In this project, we investigated the second option. The tool we were using are Minkowski Functionals (MFs). They allow to include information encoded in the lamentary structure of the cosmic matter density eld. We applied this tool to the galaxies embedded in this large scale structure density distribution. The galaxies were observed by the Sloan Digital Sky Survey in its third observational campaign. It provided us with 979, 430 galaxies in reasonably contiguous domains. They had been mainly analyzed with statistics which evaluate the correlation of two points in the survey. We constructed a quantity derived from the MFs which includes complementary information on correlations of three up to n points. This higher-order-only part of the MFs is a useful quantity, because it is supposed to vanish in the early Universe, but grows rapidly in the late universe and its growth and shape encodes our current understanding of the growth of structure which requires the dark components. Models that try to explain these dark components in a non-standard way, for example by modications of Einstein's theory of general relativity, will need to be able to explain both, the growth of the two-point correlations as well as the growth of the higher-order correlations as measured by this new quantity. We demonstrated how it actually contains the correlation information accessible by standard methods for two- and three-point correlations, but that, in addition to those, it is sensitive to higher orders up to the six-point correlation function. In a rst application, we used the new quantity to compare the higher-order correlations in the observed galaxy distribution, to galaxies derived from simulations conducted using the current paradigm. We found that one of these simulations succeeds in describing the higher-orders pretty well. This is encouraging for the assumptions that went into the construction of this simulated catalog. In a further analysis we could show, that also the evolution of this higher-order-only part of the MFs, is consistent with what is found from simulated galaxy catalogs. This analysis also underlined the importance of understanding the connection between the underlying density eld and the observable galaxies. Also for this task, the new quantity can be useful. The evolution analysis also conrmed the generally assumed picture of non-linear structure formation in which the higher order correlations grow faster than the lower orders. A more direct way of relating the parameters of the cosmological model to changes in the new quantity will be possible thanks to a large suite of simulations performed in our working group. We already started their analysis and with their help will be able to use the measurements of this quantity that we made on the data to derive enhanced constraints on cosmic parameters. This will contribute to a better understanding of our Universe and its dark side.
Projektbezogene Publikationen (Auswahl)
- The clustering of galaxies in the SDSS-III Baryon Oscillation Spectroscopic Survey: Evolution of higher-order correlations demonstrated with Minkowski Functionals
J. M. Sullivan, A. Wiegand, D. J. Eisenstein
- Lagrangian theory of structure formation in relativistic cosmology III: gravitoelectric perturbation and solution schemes at any order. Phys. Rev. D 92:023512, 2015
A. Alles, T. Buchert, F. Al Roumi, A. Wiegand
- Lagrangian theory of structure formation in relativistic cosmology IV: Lagrangian approach to gravitational waves. Phys. Rev. D 96:123538, 2017
F. Al Roumi, T. Buchert, A. Wiegand
- The clustering of galaxies in the SDSS-III Baryon Oscillation Spectroscopic Survey: higher-order correlations revealed by germ-grain Minkowski Functionals. MNRAS 467:3361, 2017
A. Wiegand, D. J. Eisenstein
