Diffuse interstellar bands as a tool for exploring galactic interstellar mediumVogrinčič, Rok (Avtor) Kos, Janez (Mentor) methods: data analysisAstronomical data bases: cataloguesAstronomical data bases: surveysISM: abundancesISM: cloudsISM: dustextinctionISM: generalISM: lines and bandsISM: moleculesISM: structureDiffuse interstellar bands (DIBs) are interstellar absorption features observed in spectra of stars reddened by dust. These bands were discovered in the early 20th century, and to date, approximately 500 of them have been identified in the optical and near-infrared wavelengths. Their exact nature is unknown, but they are likely linked to large carbon-based molecules in gaseous form, that are stable in the cold diffuse interstellar medium. Only recently has the Fullerene cation $C_{60}$ been confirmed as a carrier through laboratory studies focused on a few near-infrared DIBs. DIBs are characterized by their broad widths, spanning several \AA, which is why they are referred to as diffuse. The goal of this thesis is to explore DIBs in approximately one million spectra observed in the wavelength range from 4700 to 7900 \AA, obtained by the GALAH survey. We produce $\sim$400,000 spectra of interstellar medium (ISM) absorption features and present the first extensive DIB catalogue of the GALAH survey which contains 183 DIBs. We create a synthetic DIB spectrum at unit reddening which may permit us to narrow down the possible carriers of DIBs and explore the composition of the ISM and ultimately better model dust and star formation as well as to correct Galactic and extragalactic observations. We find that DIBs are a valuable tool for studying the galactic ISM. By utilizing the extensive DIB database from the GALAH sky survey and precise measurements of stellar positions and distances provided by Gaia, we can investigate both DIB clouds and different components of the ISM, such as interstellar dust, neutral and molecular hydrogen. We find positive and moderately high correlation between DIBs and dust reddening using various surveys of interstellar dust. We utilize two DIB families based on the sensitivity of DIBs to UV radiation. Correlations between DIBs, reddening, and other ISM tracers reveal some commonalities between the DIB families. We also study the spatial distribution of DIB carriers, explore DIB dependencies on other ISM tracers, and investigate Doppler splitting and positions of DIB clouds in the Galaxy. Our findings align with previous studies, but comparisons are limited due to diverse observing instruments, methods and sometimes poorly sampled parts of the sky.20232023-10-01 08:15:09Doktorsko delo/naloga151234sl