Search

Dwarf galaxies are a key component in understanding the evolution of galaxies and provide tests on the standard cosmological $\Lambda$ Cold Dark Matter model. According to the formation hierarchy, dwarf galaxies are the pieces that create all galaxies. Our current understanding of dwarf galaxies faces discrepancies between theory and observations. These problems are mostly due to incompleteness in observational data and the low number of simulations available. Simulations are based on the physics that drive the Universe yet they are limited by resolution and our understanding of the Universe. Observations are limited by technology and brightness limitations. The purpose of this project is to study the effect of last major merger modifications on the properties of satellites, such as the satellite luminosity function, the satellite ages and the quenching fraction, around Milky Way-like galaxies. We also show the effect that surface brightness limits have on the number of satellites and the total mass of satellites that a survey might see. To fulfil this, we use 8 cosmological hydrodynamic+N-body zoom-in simulations of Milky Way-mass galaxies. Five of those simulations are from a project called {\footnotesize VINTERGATAN-GM}, where the last major merger mass is modified to create five different simulations of identical final dynamical mass. For this project, these simulations provide an excellent investigation of the effect on the satellite population for the last major merger. In our analysis, we find that the surface brightness limit greatly effects the number of satellite and the masses that surveys would see. Going form a limit of 26 mag/arcsec$^2$, the value of today's surveys, to a limit of 32 mag/arcsec$^2$ the number of satellites increased and the masses of already detected satellites increased. Using the {\footnotesize VINTERGATAN-GM} simulations, we show how the satellite luminosity function evolves. We see that the assembly history of the functions change, Some of the most exotic objects in the universe are galaxies. Galaxies are observed on the night sky as majestic, colourful and beautifully structured objects, that are the pieces in the Universe puzzle. Galaxies are gravitationally bound systems of stars, gas, dust, and dark matter. Galaxies can only be observed through a telescope since they are far away and too faint to see with the naked eye. Galaxies come in all shapes and sizes. The theory of evolution in the Universe states that smaller galaxies merge to create bigger galaxies. This has the implication that galaxies like our own Milky Way will have a population of dwarf galaxies (often called satellites) floating around them. The Milky Way has a dwarf galaxy population that effects the dynamics and the overall evolution of it. In this project, we ask if the satellite populations around host galaxies can tell us anything about the evolution of the Milky Way. The field of galaxy formation and evolution is a growing field. Today, we see many discrepancies between theory and observations. That means our simulations are not showing the same results as observations. The simulations account for dark matter, baryons, stellar feedback and multiple other properties, but the lack of computational power and resolution is still hindering the completeness of models. Observations are also not free from faults. Observations are limited by technology in a way that depends on distance and brightness. When seeing satellites far away, the telescopes see only down to a certain brightness limit. In this thesis, we have shown that reaching fainter limitations in brightness, gives a greater number of satellites and more mass. This means that observations today are not seeing the full picture and lack data to make their analysis. Luckily for us, there are multiple telescopes in preparation and simulations are always being improved that will solve the discrepancies in the future. The future will provide us with a better understanding

Low-mass "dwarf" galaxies (stellar mass, M* <= 3 x 10^9 Msun), being ubiquitous in the universe, are excellent laboratories for testing critical components of galaxy evolution. The current and future photometric and spectroscopic surveys, including the Sloan Digital Sky Survey (SDSS), the Dark Energy Survey (DES), the Dark Energy Spectroscopic Instrument (DESI) survey, and the Legacy Survey of Space and Time (LSST) are facilitating the study of these galaxies in great detail. In this dissertation, I probe three different aspects of galaxy evolution using dwarf galaxies. Firstly, by conducting the widest (1.5 deg diameter field of view) and the deepest (down to g ~ 26.5 mag) survey of resolved stars in a Local Group dwarf galaxy, IC 1613, I found evidence of hierarchical accretion in the galaxy. This is an important first step in understanding structure formation in dwarf galaxies. Secondly, I demonstrated that the compact morphologies of Lyman-Alpha Emitters (LAEs), i.e., low-mass, high-redshift galaxies, are key to Ly-alpha escape, a process that is crucial for understanding the epoch of reionization. Finally, using an unprecedented spectroscopic sample of ~190,000 low-mass galaxies from the DESI survey, I identified >2,500 active galactic nuclei (AGNs) out to z ~ 0.45, more than tripling the existing census of optical dwarf AGN candidates. Compared to previous systematic searches, I have extended the discovery space of such candidates to lower galaxy masses and to higher redshifts. Additionally, I extended the black hole (BH) mass - galaxy stellar mass (M_BH - M*) scaling relation down to log (M*/Msun) ~ 8.4. This statistical sample of AGN in low-mass galaxies will have important implications for the study of galaxy-BH co-evolution at the low-mass end of the galaxy mass function. Furthermore, I created four publicly available Jupyter Notebooks that show how to access and analyze photometric and spectroscopic data for the scientific analysis of galaxies.