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Identifier 000456538
Title Discriminating power of milli-lensing observations for dark matter models
Alternative Title Διακριτική ικανότητα παρατηρήσεων βαρυτικών μιλλι-φακών για μοντέλα σκοτεινής ύλης
Author Λούδας, Νικόλαος Α.
Thesis advisor Παυλίδου, Βασιλική
Reviewer Παπαδάκης, Ιωσήφ
Casadio, Carolina
Abstract The nature of dark matter (DM) is still under intense debate. Subgalactic scales are particularly critical, as different, currently viable DM models make diverse predictions on the expected abundance and density profile of DM haloes on these scales. In this thesis, we investigate the ability of subgalactic DM haloes to act as strong lenses on background compact sources, producing gravitational lensing events on milli-arcsecond scales (milli-lenses), for different DM models. For each DM scenario, we explore whether a sample of ∼ 5000 distant sources is sufficient to detect at least one milli-lens. We developed a semi-analytical model to estimate the milli-lensing optical depth as a function of the source’s redshift for various DM models. We employed the Press-Schechter formalism, as well as results from recent N-body simulations to compute the halo mass function, taking into account the appropriate spherically averaged density profile of haloes for each DM model. We treated the lensing system as a point-mass lens and invoked the effective surface mass density threshold to calculate the fraction of a halo that acts as a gravitational lens. We studied three classes of dark matter models: cold DM, warm DM, and self-interacting DM. We find that haloes consisting of warm DM turn out to be optically thin for strong gravitational milli-lensing (zero expected lensing events). Cold DM haloes may produce lensing events depending on the steepness of the concentration-mass relation. Self-interacting DM haloes can efficiently act as gravitational milli-lenses only if haloes experience gravothermal collapse, resulting in highly dense central cores. The redshift distribution of the source sample is fundamental in estimating the expectation number of detected milli-lenses under a specified DM scenario.
Language English
Subject Dark matter
Galaxies: halos
Gravitational lensing: strong
Methods: analytical
Βαρυτικός φακός: ισχυρός
Γαλαξίες: άλως
Μέθοδος: αναλυτική
Σκοτεινή ύλη
Issue date 2023-07-28
Collection   School/Department--School of Sciences and Engineering--Department of Physics--Post-graduate theses
  Type of Work--Post-graduate theses
Permanent Link https://elocus.lib.uoc.gr//dlib/e/7/1/metadata-dlib-1687435006-765846-11615.tkl Bookmark and Share
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