| Nota di contenuto |
1 Introduction -- 1.1 Star formation process -- 1.1.1 The challenge of high-mass star formation -- 1.2 The importance of high-mass star-forming regions for the Solar system formation -- 1.3 Astrochemical processes in the interstellar medium 1.3.1 Gas-phase chemistry -- 1.3.2 Type of reactions -- 1.4 Isotopic fractionation in the context of star formation -- 1.4.1 The evolution of chemical complexity during star forma- tion -- 1.4.2 The heritage of the Solar system -- 1.4.3 Deuterium enrichment during star formation -- 1.4.4 Nitrogen fractionation in the ISM -- 1.5 Thesis project -- 2 Nitrogen and hydrogen fractionation in high-mass star-forming regions -- 2.1 Introduction -- 2.2 Observations and data reduction -- 2.3 Results: column densities and isotopic ratios -- 2.3.1 HNC, HN13C, HCN, and H13CN -- 2.3.2 DNC -- 2.4 Isotopic fractionation -- 2.4.1 15N-fractionation as a function of evolutionary stages -- 2.4.2 D-fractionation -- 2.4.3 Comparison between D/H and 14N/15N -- 2.5 The HCN/HNC ratio -- 2.6 Conclusions -- 3 Nitrogen fractionation across the Galaxy -- 3.1 Introduction -- 3.2 Sample and observations -- 3.2.1 Description of the sample -- 3.2.2 Observations -- 3.3 Results -- 3.3.1 Line detection -- 3.3.2 Fitting procedure and column density calculation 3.3.3 14N/N ratios -- 3.4 The Galactocentric behaviour -- 3.4.1 Linear analysis -- 3.4.2 Parabolic analysis -- 3.5 Discussion and Conclusions -- 4 Enhanced nitrogen fractionation at core scales -- 4.1 Introduction -- 4.2 Source and observations -- 4.3 Results -- 4.3.1 Continuum map -- 4.3.2 Morphology of NH and 15N-isotopologues emission 4.3.3 Fitting procedure and column density calculation 4.3.4 14N/15N ratios -- 4.4 Discussion of the results -- 4.4.1 Comparison between line and continuum emission maps 4.4.2 Is N-fractionation a core-scale effect? -- 4.4.3 15NNH vs N15NH+ -- 4.4.4 14N/15N ratios in diffuse regions -- 4.5 Conclusions -- 5 Carbon isotopic fractionation: a new detailed chemical study -- 5.1 Introduction -- 5.2 Model -- 5.2.1 Chemical model -- 5.2.2 Introduction of 13C-fractionation in the chemical model 5.2.3 Isotopic exchange reactions -- 5.3 Results and Discussion -- 5.3.1 The fiducial model -- 5.3.2 The importance of Cs isotopic-exchange reaction 5.3.3 Parameter space exploration -- 5.4 Conclusions -- 6 Summary and Main Conclusions -- A Appendix: Spectra simulation tests -- A.1 15N-isotopologues at lower spectral resolution -- A.2 NH at higher spectral resolution -- A.3 The effect of a possible N2H+ line saturation -- Bibliography -- Ringraziamenti -- Acknowledgments.
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Isotopic fractionation study towards massive star-forming regions across the Galaxy / / Laura Colzi
