Methyl acetylene in G331.512-0.103: Looking at massive star formation through the lens of chemistry

• Ano de defesa: 2021
• Autor(a) principal: Santos, Julia de Carvalho
• Tipo de documento: Dissertação
• Tipo de acesso: Acesso aberto
• Idioma: eng
• Instituição de defesa: Biblioteca Digitais de Teses e Dissertações da USP
• Palavras-chave em Português: Astrochemistry; Astroquímica; Hot Molecular Cores; Methyl acetylene; Metil acetileno; Radio astronomia; Radio astronomy
• Link de acesso: https://www.teses.usp.br/teses/disponiveis/14/14131/tde-09032021-113432/

In the present master\'s thesis, we aim to explore the physical properties of massive star-forming regions by means of their molecular emission spectra, which can provide powerful information on the source. Thus, we conducted a spectral survey of methyl acetylene (CH3CCH) toward the Hot Molecular Core/massive outflow G331.512-0.103, using the APEX 12 m telescope. Our observations yielded the detection of 41 clear and uncon-taminated rotational lines of CH3CCH in the frequency range between 172356 GHz. Through an analysis under the Local Thermodynamic Equilibrium (LTE) assumption, by means of rotational diagrams, we determined Texc=47.1 ± 1.2 K, Ntot(CH3CCH) = 6.9 ± 0.5 x 1015 cm2 and X[CH3CCH/H2] (1.57.6) x 10-8 for an extended emitting region (~10). We observed that the relative intensities of the K=2 and K=3 lines within a given K-ladder are strongly negatively correlated to the transitions\' upper J quantum-number (r=-0.84). Pure rotational spectra of CH3CCH were simulated at different temperatures, in order to explore this observation. Conjointly, adaptations to the rotational diagram technique were also employed. The results indicate that the emission is characterized by a non-negligible temperature gradient with upper and lower limits of ~40 and ~60 K, respectively. Moreo-ver, the line widths and peak velocities show an overall strong correlation with their rest frequencies, suggesting that the warmer gas is also associated with stronger turbulence effects. The K=0 transitions present a slightly different kinematic signature than the re-mainder, indicating that they might be tracing a different gas component. We speculate that this component is characterized by lower temperatures, and therefore larger sizes. However, observations with higher angular resolution are imperative to verify our conclu-sions.