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Identifier 000446576
Title Studying the Spectra of Luminous Infrared Galaxies (LIRGs)
Alternative Title Μελέτη φασμάτων από Φωτεινούς Υπέρυθρους Γαλαξίες
Author Μαρκοπουλιώτη Λυδία Ε.
Thesis advisor Diaz Santos, Tanio
Χαρμανδάρης, Βασίλης
Abstract The Great Observatories All-Sky LIRG Survey (GOALS) is a comprehensive, multi- wavelength study of luminous infrared galaxies (LIRGs) in the local universe. Its aim is to provide a multi-wavelength understanding of the evolution and the formation mechanisms of local LIRGs. In this project we built the spectral cubes of 55 luminous infrared galaxies from the GOALS sample for which there are mapping observations obtained with the IRS instrument of the Spitzer Space Telescope.We extracted the spectra of the nuclear and the extended emission. The spectra of the extended emission allows us to study the properties of the ISM in the extended regions of the galaxy and compare them with the nucleus. The extraction was conducted following four different aperture extraction methods, which varied as a function of wavelength and also as a function of the luminosity distance of the galaxies. After doing a spectral decomposition analysis of the extended emission spectra of the galaxies in our sample, we measured the most prominent PAH features and the silicate absorption. We also took under consideration that the galaxies of our sample cover a range of masses, silicate strengths, AGN fractions and merger stages. By stacking the extended emission spectra using bins, we identified that high AGN fraction could be affecting the extended emission of the galaxy. While the extended spectrum of galaxies with the highest AGN fractions exhibit the same PAH features with the spectrum coming from the lower AGN fractions, at longer wavelengths (> 14μm) the extended spectrum of the galaxies with high AGN fraction turns into a featureless continuum and it seems hotter. This suggests that the AGN could be able to heat the extended regions of the galaxy. The diagnostic plot of 6.2/7.7 μm - 11.3/7.7μm PAH features shows change in the grain size and the ionization of the medium between the nuclear and the extended regions of the galaxy. We infer that the degree of ionization of the extended regions appear smaller than the ionization of the nucleus.
Language English
Subject AGN
Extended emission
Merger stage
Nuclear emission
Silicate absorption
Silicate strength
Spectral cubes
Απομακρυσμένες περιοχές
Υπέρυθροι γαλαξίες
Issue date 2022-04-01
Collection   School/Department--School of Sciences and Engineering--Department of Physics--Post-graduate theses
  Type of Work--Post-graduate theses
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