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Unveiling the Architecture of the Fornax Galaxy Cluster with its Different Stellar Systems

Ordenes Briceño, Yasna

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Abstract

A crucial question in astronomy is how galaxies assemble their mass over cosmic time. In this thesis, we focus on the Fornax Galaxy Cluster as a laboratory to study galaxy evolution processes, as it is the second closest galaxy cluster which allows a detailed view of its cluster members. It hosts a variety of stellar systems from giant galaxies to dwarf galaxies and more compact and dense ones such as globular clusters and ultra-compact dwarf galaxies which we call compact stellar systems (CSSs). We use data from the Next Generation Fornax Survey (NGFS) with optical imaging obtained with the Dark Energy Camera (DECam) mounted at Blanco/CTIO and near-infrared data obtained with VIRCam at VISTA/ESO. This data provides deep and homogeneous photometry in ugiJKs spatially covering the Fornax cluster out to half its virial radius. We investigate the properties of nucleated dwarf galaxies and compact stellar systems in the Fornax core region (r < 0.25r_vir). Furthermore, we study the dwarf galaxy population with M_B > −16 in the outer region of Fornax at radii of 0.25 < r/r_vir < 0.5. The main results of this thesis are as follows: (1) We have discovered 271 previously undetected dwarf galaxies in the outer Fornax cluster region, increasing the the total Fornax dwarf galaxy population from NGFS and other catalogs to a total number of 643 dwarfs with 181 being nucleated. (2) The study of 61 nuclear star clusters in dwarf galaxies showed that the nuclei have a bimodal mass distribution and that the scaling relation between nuclei mass and host galaxy mass holds for dwarf galaxies but at a less steep slope compared to brighter galaxies. The mass ratio M_nuc /M_gal shows a clear anticorrelation with M_gal for the lowest masses, reaching up to 10%. (3) A total of 1666 CSS candidates have been studied in the core region of Fornax, being the most clean photometriccally selected sample using support vector machine techniques. Age, metallicity and mass were estimated for each CSS. A division of the properties in subgroups showed that the metal poor and old CSSs are sparsely distributed, intermediate metallicity and young CSSs are preferentially located along the East-West direction of Fornax centered in NGC 1399 and the most metal rich CSSs are concentrated in the vecinity of NGC 1399 and around the brightest galaxies. These different distributions for the metallicity and age subgroups allow us to constrain the mass assembly history of the Fornax Cluster. (4) Besides the Fornax cluster, we also discover five very diverse dwarf galaxies in another region of the sky, i.e. Hickson Compact Group 90 (HCG 90). Two of these dwarfs are a dwarf galaxy pair and one is a nucleated dwarf galaxy. According to their luminosity and structural parameters, they are similar to the dwarf galaxies we found in Fornax.

Item Type: Dissertation
Supervisor: Grebel, Prof. Dr. Eva
Date of thesis defense: 25 October 2018
Date Deposited: 14 Dec 2018 11:12
Date: 2018
Faculties / Institutes: The Faculty of Physics and Astronomy > Dekanat der Fakultät für Physik und Astronomie
Subjects: 520 Astronomy and allied sciences
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