Matched filter galaxy group finder

Saha, Navonil (2023) Matched filter galaxy group finder. Masters thesis, Indian Institute of Science Education and Research Kolkata.

Text (MS dissertation of Navonil Saha (18MS079)) Thesis_18MS079.pdf - Submitted Version Restricted to Repository staff only Download (9MB)

Abstract

It is now well established that structure in our universe formed by gravitational instability, which magnifies initial density fluctuations and concentrates matter (predominantly dark matter) into nonlinear clumps called dark matter “haloes”. Galaxies form within these structures, and a central task for cosmology is to understand how the resulting galaxy populations depend on the properties of the haloes that they inhabit. Next-generation galaxy surveys aim to use the galaxy distribution as a proxy for the overall mass density, in order to study fundamental issues such as the nature of gravity and the properties of the ”dark energy” that drives the accelerating cosmic expansion. In this work, it is therefore essential to have a detailed knowledge of the mapping between dark and visible matter. One way of approaching this is to study galaxy groups and clusters, since these systems must correspond to individual dark matter haloes. The state of the art in galaxy groups is the catalogue created from the GAMA spectroscopic survey. The current state of the art group finding algorithms use only spectroscopically observed galaxies, ignoring much larger samples with photometric redshifts. In this project we will focus on developing a new group finding algorithm based on the technique of matched filtering, which has recently been applied with great success in gravitational wave detection and black-hole imaging. We will focus on building filters for groups based on analytical profiles of haloes, and test these by applying the filters to simulated mock universes. A successful group finding algorithm going beyond the current state of the art will pave the way to many science questions in both cosmology and physics, concerning the formation and evolution of galaxies.

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