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Galaxy properties at the Cosmic Noon
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Resumo(s)
The spectral energy distribution (SED) of galaxies offers essential insights about their stellar populations, interstellar gas, and star formation, making it a key tool for studying galaxy evolution. We investigated the interstellar gas properties in star-forming galaxies at Cosmic Noon (2 ≤ z ≤3), the period of peak star formation in the Universe. Our sample includes five galaxies observed with Near-Infrared Spectrograph (NIRSpec) on the James Webb Space Telescope (JWST), using both low-resolution (PRISM) and medium-resolution (GRISM) spectra. We used FADO (Fitting Analysis using Differential Evolution Optimization) for spectral modeling, which accounts for nebular contributions to the continuum. To assess the impact of missing flux values due to the detector gaps in NIRSpec, we compared approaches and found that retaining these null values leads to more reliable estimates of stellar ages, metallicities, and total stellar masses. FADO masks these gaps during fitting, avoiding the introduction of artificial values. Based on the [NII]-BPT diagram, we classified three galaxies as star-forming, one as composite, and one as AGN. Relative to the SDSS local sample, our galaxies show higher log([OIII]/Hβ) and log([NII]/Hα) values, consistent with previous high-redshift findings and likely due to lower metallicities, higher ionization parameters, and different interstellar medium conditions. The star formation rates range from about 6 to 100 M⊙ yr−1 , and stellar masses span 8.9 < log(M/M⊙) < 10.0. Three galaxies are slightly above the star-forming main sequence, suggesting possible starburst activity, while one falls below. The nebular contribution to the total continuum is low (less than 5%), consistent with low to moderate Hα equivalent widths. Our results show that the choice of spectral basis in FADO significantly affects stellar mass estimates, emphasizing the need to select suitable stellar population models for high-redshift galaxies. This study highlights the importance of careful data handling and self-consistent spectral modeling for accurately determining galaxy properties during peak cosmic star formation. It also establishes a framework for analysing larger JWST-based galaxy samples in future research.
Descrição
Tese de Mestrado, Física (Astrofísica e Cosmologia), 2025, Universidade de Lisboa, Faculdade de Ciências
Palavras-chave
FADO Nebular Continuum Star Formation Galaxy Evolution JWST