Unveiling the architecture of the Fornax galaxy cluster with its different stellar systems
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2018
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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
u'g'i' JKs 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 < 0.25rvir). Furthermore, we study the dwarf
galaxy population with MB > −16 in the outer region of Fornax at radii of
0.25 < r/rvir < 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 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 nucleus
mass and host galaxy mass holds for dwarf galaxies but at a less steep slope
compared to brighter galaxies. The mass ratio Mnuc/Mgal shows a clear anticorrelation with Mgal 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 photometrically 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 vicinity 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.
Description
Tesis (Doctor of Natural Science)--Pontificia Universidad Católica de Chile, 2018
Tesis (Dissertation in Astronomy)--Ruperto-Carola-University of Heidelberg, 2018
Tesis (Dissertation in Astronomy)--Ruperto-Carola-University of Heidelberg, 2018