19 January 2022Séminaire – Gauri Sharma (University of Western Cape)

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Observational Evidence of Evolving Dark Matter Halos with cosmic time


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, in 2017, of high-redshift SFGs show declining Rotation Curves
(RCs), and thus questioning the “faith of the dark matter halos” back in time. I will present a study of z~1 SFGs, in which I have tested and applied several cutting-edge techniques capable of dealing with
the observational and physical conditions that are commonly encountered in high-redshift observations. My work shows that:
  • RCs of z~1 SFGs are flat and similar to their local counterparts.
  • SFGs at z~1 are dark matter dominated till outer disks (∼ 5 to 15 kpc).
  • Density profile of dark matter halos evolve between z ≈ 0 and z ∼ 1.
I will briefly discuss the above results, and present an interesting work that observationally measures the dark matter response to the 
baryonic (feedback) processes. I will show the empirical relation between the observable properties of dark and luminous matter,
which can be verified with current and future surveys. In future, a comparison of this work with simulations can specify the role
of baryonic (feedback) processes in galaxy evolution, as well as constraints on the mass and cross section of a potential dark matter particle.