Physical and chemical complexity in the molecular cloud Orion KL
27-06-2014 CAB THESIS

Gisela Bañó Esplugues defended her thesis work at the Complutense University of Madrid entitled "Physical and chemical complexity in the molecular cloud Orión KL" directed by José Cernicharo Quintanilla and Javier Rodríguez Goicoechea, obtaining the qualification of Outstanding "Cum Laude" ".

Through the spectral sweeps carried out with the radio telescope 30 m IRAM (80-280 GHz) and the Herschel space telescope (480-1910 GHz), it has been studied the emission of the molecular gas in the different spectral components (core, plateau and ridge ) of the molecular cloud Orion KL, deepening in the understanding of its physical and chemical properties. < / p>

In this thesis, more than 1,500 spectral lines belonging to two families of molecules have been analyzed; those that contain sulfur and cyanoacetylene. With them, the regions characterized by the presence of gas processed by shocks and the hottest and densest regions of the cloud, respectively, have been drawn, using for this analysis the Madex radiative transfer code. Among the main results, it stands out the obtaining of column densities for each species and isotopic and molecular abundances, the determination of the SO species as the best tracer of collisions that SO 2 and of the species SO 2 as the best hot and dense gas tracer than SO. In addition, the presence of a continuous temperature gradient in the core of the cloud has been detected, suggesting the presence of internal heating in the region. With respect to molecules containing cyanoacetylene, a comparison of the results obtained in this thesis with those of other authors in different regions of massive star formation, shows a correlation between the column density of HC 3 N and the width of its lines with some properties of the molecular nuclei containing said species, such as its mass and luminosity. The deuterated species DC 3 N has also been detected for the first time in a massive star formation nucleus, with a D / H ratio similar to that obtained in dark clouds, suggesting deuterium enrichment in the Orion nucleus. KL A chemical analysis of its evolution has allowed us to know the origin of this species, which is formed in part during the hot gas phase of the cloud.

Finally, the chemical evolution of molecules containing sulfur, both in the core of Orion KL and in the plateau (region affected by collisions), using the code UCL_CHEM. The objective has been to investigate the initial structure of the cloud, the processes that dominate sulfur chemistry and analyze the physical and chemical parameters that most influence the evolution of abundances of SO, SO 2 , OCS , CS, H 2 S and H 2 CS. From the results obtained it is concluded that most of the sulfur atoms present in the collapse phase of the cloud were ionized and that the initial structure of the cloud was inhomogeneous allowing the UV light to penetrate giving rise to said ionization. In addition, it has been obtained that the main reserve of sulfur on the dust grains was ice of OCS (~ 5%) and H 2 S (~ 95%), and that is currently taking place in the plateau a chemical transition where the reactions of formation and destruction of sulfur-containing species go from being dominated by molecular oxygen to being dominated by the OH species.

 

Fuente: UCC-CAB

 

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