Hα emission observations of nearby baryonic structures
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2022
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Abstract
A fundamental question in astronomy is how the environment affects galaxy evolution. Baryonic structures in the nearby universe can be used as laboratories to study the influence of the environment on galaxy evolution processes, since their close distances allow a detailed view of its member galaxies and their substructures. It is believed that the structures that we observe in the nearby universe form through the accretion of smaller groups of galaxies; thus, environmental processes can influence galaxies even before they enter larger clusters. The synergy between numerical simulations and surveys dedicated to observing large samples of galaxies is fundamental to trace and understand the physical properties of different galaxy components. In this context, star formation is one of the most fundamental parameters that characterizes galaxies, and can be heavily influenced by environmental conditions. We use data from the Next Generation Fornax Survey (NGFS) obtained with the Dark Energy Camera (DECam) g’r’i’ broadbands and N662 narrow-band covering the H-alpha + [N II] emission lines to study star formation in the central region (~R_vir/4) of the Fornax cluster of galaxies. We present a method for continuum subtraction in narrow-band images. From the continuum-subtracted H-alpha emission, we derived star formation rates (SFR) for a sample of dwarf galaxies in the central region of the Fornax cluster. Most of the dwarfs presenting H-alpha emission have large nuclei, with high temperatures in their very centers, suggesting the presence of a young stellar population. H-alpha emission concentrates in the centers of these galaxies. Considering the proposed scenarios for the formation of nucleated dwarf galaxies, our observations are in agreement with the model of in-situ star formation in their centers. We have found a spatial asymmetry in the distribution of H-alpha emitting nucleated dwarf galaxies around the Fornax center, suggesting different formation histories. We also discuss SFRs for NGC 1427A, a dwarf irregular galaxy with an intense burst of star formation. Broadband DECam data also allowed us to generate mass maps, from which we constructed diagrams of specific star formation rates versus pixel mass. In these diagrams, we can identify different substructures in the galaxies.
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Tesis (Master in Astrophysics)--Pontificia Universidad Católica de Chile, 2022