Punyakoti Ganeshaiah Veena successfully defended PhD thesis "Cosmic Ballet: spinning in the web"

On October 16, Tartu Observatory's Junior Research Fellow Punyakoti Ganeshaiah Veena successfully defended her PhD dissertation "Cosmic Ballet: spinning in the web". She gained a doctoral degree from the University of Groningen.

Colleagues of Tartu Observatory gifted Veena with the chance to support the education of two girls in her country of birth India.


Prof. Rien van de Weijgaert (University of Groningen), Prof. Elmo Tempel (University of Tartu), PhD Marius Cautun (Leiden University)


All the celestial objects, from small asteroids and planets to large galaxies and even the long filaments of the cosmic web are rotating. The origin of rotation is yet to be fully understood, especially in the context of galaxies and their dark matter haloes. In the young Universe, as matter began to clump together, the resulting anisotropic distribution of matter torqued up proto-galaxies. Simultaneously, the matter overdensities collapsed to form the large-scale filaments, clusters, walls and voids of the cosmic web that we see today. As a result, we expect a correlation between galaxy spin and the cosmic web. In this thesis, we uncover the role of the cosmic web environment in establishing the rotation of haloes and galaxies using large cosmological simulations. We show that haloes in filaments are in general spinning faster than in other web components. We have studied the correlations between the spin-axis of haloes/galaxies with the orientation of the cosmic filaments that they are growing in. The thesis explores in detail the spin transition from parallel to perpendicular as a function of the halo or galaxy mass with respect to the spine of the host filament. We show how these trends evolve with cosmic time and filament properties using the MMF/Nexus and Bisous formalisms for cosmic web detection. The results from this thesis are important for various reasons. They not only hold information on how structure in the Universe emerged but also the notion of spin-transition mass promises to be a potential tool to probe the Universe.

Read the thesis