Astronomers from the University of Tokyo and the Max Planck Institute for Astrophysics have developed a novel technique for analyzing three-dimensional galaxy maps that uncovers hidden information about dark matter and dark energy. The method, termed 'field-level inference' (FLI), employs advanced computer algorithms to compare the relative positions of galaxies in a three-dimensional universe map with detailed simulations that depict the growth and behavior of galaxies and dark matter halos.
Traditionally, astronomers conducted galaxy surveys by capturing deep-space images on photographic plates and measuring the spatial distribution of galaxies in two dimensions. They sought answers to questions such as 'How close are these galaxies to their neighbors?' and 'How well are they aligned with each other?' Modern surveys have added a third dimension through multi-object spectroscopy, which measures the redshift of galaxies, thereby determining their distance in the expanding universe. This advancement enabled the creation of three-dimensional maps of the universe, but researchers suspected that critical information was lost in this compression.
The new FLI method works directly with three-dimensional galaxy maps represented in computer voxels—three-dimensional pixels in a grid. The team, led by astronomer Minh Nguyen, applied FLI alongside a set of algorithms within the LEFTfield system, which models galaxy growth and clustering from the early universe to the present. Results demonstrated a 3-5 times improvement in detail and accuracy compared to two- and three-point correlation functions.
This additional information may assist scientists in testing the standard cosmological model and identifying possible deviations that could enhance understanding of the 'dark universe.' FLI has the potential to reveal asymmetries in quantum fluctuations from the Big Bang that led to galaxy formation or anomalies in the gravitational evolution of galaxies, potentially providing new insights into dark matter or gravity itself.
'With access to the entire underlying field of dark matter associated with the observed galaxy field, we can be more sensitive to local effects,' explained Nguyen. Such local effects are averaged out when analyzing using n-point functions.
The next step involves applying FLI to real data from instruments such as the Dark Energy Spectroscopic Instrument at the Kitt Peak National Observatory, the Subaru Telescope Spectrograph, and the European Space Agency's Euclid mission. Future applications are planned with data from the Vera C. Rubin Observatory and the Nancy Grace Roman Space Telescope.
Fabian Schmidt, a co-author of the study, noted, 'It is quite elegant, considering we cannot directly observe dark matter, and it complements dark matter maps constructed using gravitational lensing.'
This new analytical method could not only enhance understanding of galaxy distribution in the universe but also lead to discoveries about the origins of everything observed in space.