Abstract
Dark matter (DM) is predicted to be the dominant mass component in galaxies. In the central region of early-type galaxies it is expected to account for a large amount of the total mass, although the stellar mass should still represent the majority of the mass budget, depending on the stellar initial mass function (IMF). We discuss latest results on the DM fraction and mean DM density for local galaxies and explore their evolution with redshifts in the last 8 Gyr of the cosmic history. We compare these results with expectations from the ΛCDM model and discuss the role of the IMF and galaxy model through the central total mass density slope. We finally present future perspectives offered by next-generation instruments/surveys (Rubin/LSST, Euclid, CSST, WEAVE, 4MOST, and DESI), which will provide the unique chance to measure the DM evolution with time for an unprecedented number of galaxies and constrain their evolutionary scenario.
Highlights
Early-type galaxies (ETGs) are the most massive galaxy systems in the Universe and represent the final stage of galaxy evolution
Among the others, using SPIDER data, we have found a larger stellar mass in the most massive galaxies than that provided by a MilkyWay Chabrier initial mass function (IMF), which can be translated into a bottom-heavy IMF (Salpeter-like) or a larger dwarf-to-giant star ratio (Tortora et al, 2013)
In this article we have summarized a simple but accurate dynamical method based on Jeans equations, to estimate the Dark matter (DM) content within 1 effective radius in early-type galaxies, making use of high quality surface photometry and aperture internal kinematics
Summary
Early-type galaxies (ETGs) are the most massive galaxy systems in the Universe and represent the final stage of galaxy evolution As such, they carry the fossil record of the assembly of stellar and dark matter through time, and, because they are bright and massive, can be studied in detail from low to high redshifts. In the last two decades, increasing evidences have been collected, showing that the central DM fraction (typically within one effective radius, Re hereafter) is higher in larger and more massive galaxies (e.g., Hyde and Bernardi 2009b; Ruszkowski and Springel 2009; Tortora et al, 2009; Auger et al, 2010a; Napolitano et al, 2010; Thomas et al, 2011; Tortora et al, 2012) This positive correlation with mass seems almost insensitive to the adopted galaxy mass profile or initial mass function (IMF)
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