Gauri Sharma - Evolution of dark matter halos with redshift

 

by Gauri Sharma (SISSA)

 

Abstract: In the late 1970s, Vera Rubin showed that flat rotation curves are ubiquitous in local Star-Forming Galaxies (SFGs) and concluded that “galaxies are surrounded by an invisible matter, the so-called dark matter halo, that extends much farther than their visible matter”. However, recent observations of high-redshift SFGs revealed declining rotation curves (e.g., see Genzel et al. 2017 and Lang et al. 2017), thus questioning the presence of dark matter halos in these systems. Understanding this apparent discrepancy would allow us to gain useful insights to determine the nature, evolution and distribution of dark matter. To investigate this, I have recently performed a detailed study of z~1 SFGs, by analysing the large sample of KROSS data with dedicated cutting-edge techniques, to face the challenges commonly encountered in high-redshift observations. Here I will present my results, showing that the rotation curves of z~1 SFGs are flat and similar to their local counterparts, that these galaxies are dark matter dominated till their outer disks (~5 to 20 kpc), and that the density profiles of dark matter halos evolve between z≈0 and z~1. This also allowed me to observationally measure the dark matter response to baryonic (feedback) processes, and to obtain an empirical relation between the observable properties of dark and luminous matter, which can be verified with current and future surveys. In the future, a comparison of this work with simulations will specify the role of baryonic processes in galaxy evolution, and constrain the mass and cross section of potential dark matter particles.

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