Today, the prevailing model of the Universe is Lambda Cold Dark Matter (ΛCDM), which explains the evolution of the cosmos from its origin in the Big Bang to the present time. ΛCDM predicts that the universe is composed of Dark Energy (DE, 68.3%), which is responsible for the accelerating expansion of the Universe, Dark Matter (DM, 26.8%), composed of unknown particles and baryonic or ordinary matter (4.9%), made of elements in the Periodic Table. Although DM has not been directly detected, the postulated effects of ΛCDM have so far passed many large-scale observational tests. However, at the scale of galaxies and galaxy clusters, some tension (discrepancy) remains between its predictions and observations.
ΛCDM predicts that galaxies grow and evolve by accreting dwarf galaxies that orbit around them, and that their halos are populated by remnants of such accretion events, known as minor mergers. The accretion is driven by the gravitational pull of the host galaxy that rips the stars from the dwarf satellite forming so-called tidal streams. These streams are very faint and therefore difficult to detect beyond our Local Universe, at distances of more than 30 million light-years from the Milky Way (MW), requiring deep imaging surveys to detect the brightest ones.
Our window to the ΛCDM universe is provided by cosmological simulations, models of the evolution of the Universe that incorporate all the contributing elements: baryonic matter (stars and gas) and DM, as well as all relevant physical phenomena, such as star formation, stellar evolution, chemical evolution, metallicity-dependent cooling, supernovae, and black holes (BH) accretion and feedback.
The present paper, in the frame of the Stellar Streams Legacy Survey, compares the predictions of cosmological simulations from state-of-the art codes with observations from the Dark Energy Survey (DES), taken with a 570-megapixel digital camera, DECam, mounted on the Blanco 4-meter telescope at Cerro Tololo Inter-American Observatory, high in the Chilean Andes. The results obtained show no tension between observations and ΛCDM simulations.
In addition, the simulations predict that fordeeper images like the ones expected from the ARRAKIHS satellite, a significantly higher number of streams will be detected. This will allow for a robust test of ΛCDM and related cosmological simulations, and provide deep insight into the low surface brightness (LSB) universe within of galaxies like our Milky Way.
Read the complete paper by Juan Miró-Carretero et al. here.
