Universiteit Leiden

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Dissertation

The alignment of galaxies across all scales

Galaxy intrinsic alignments induce a major astrophysical contamination to weak gravitational lensing measurements and need to be modelled and mitigated when extracting cosmological information from such measurements.

Author
Georgiou, C.
Date
12 December 2019
Links
Thesis in Leiden Repository

Galaxy intrinsic alignments induce a major astrophysical contamination to weak gravitational lensing measurements and need to be modelled and mitigated when extracting cosmological information from such measurements. This dissertation studies the signal of the intrinsic alignment of galaxies in large and small scales. Informative priors are provided for the signal, which improve the constraining power of weak lensing data. Moreover, the dependence of the signal with the observed wavelength is studied, finding significant differences in the alignment of galaxies observed in different bands. The source of this difference appear to be satellite galaxies, and the alignment of galaxies inside galaxy groups is explored, finding that the alignment signal depends on the scale of a galaxy, with outer regions being more strongly aligned that inner ones. Lastly, the alignment of galaxies with their host dark matter halo is probed by measuring the anisotropic weak lensing signal around them, which leads to the conclusion that outer regions of galaxies are also more aligned with their dark matter halo than inner ones.

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