Large-scale physical and molecular conditions in structures of Cygnus-X
Large-scale physical and molecular conditions in structures of Cygnus-X
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DissertationPrüfungsdatum
12.06.2026Datum der Veröffentlichung
05.08.2026Erstgutachter
Viti, SerenaZweitgutachter
Bigiel, FrankMetadaten
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Inhalt
The physical state of the interstellar medium (ISM) is essential for understanding the intricate processes involved in massive star formation within galaxies. The nearby (d ~ 1.5 kpc) molecular cloud, Cygnus-X, harbors multiples sites of high-mass star-formation, allowing us to probe the various stages as stars form and how the chemistry evolve. Within the Cygnus Allscale Survey of Chemistry and Dynamical Environments (CASCADE), we aim to explore the large-scale distribution of deuterated molecules in Cygnus-X. A plethora of star-forming clumps are observed with the CASCADE survey, where clumps are believed to evolve from quiescent infrared-dark clouds to high-mass protostellar objects to hot molecular cores to ultra-compact HII regions. The most active and dense region within Cygnus-X is the DR21 filament, harboring the prominent HII region DR21 Main with the most intense outflow of the Milky Way. The degree of deuteration, R, can significantly enhance over the elemental D/H-ratio (10−5) depending on physical parameters such as temperature, density, and ionization fraction. Deuterated molecules and their molecular D/H-ratios are important diagnostic tools to study the physical conditions of star-forming regions.
This thesis focuses on probing the deuterated fractions of Cygnus-X. Along the DR21 filament, the deuterated fraction of DCO+, DNC, and DCN exhibit morphological variations, caused by the local physical conditions. Active star-formation along the filamentary structure initiate shock chemistry in these high density region, destroying DCO+, and consequently decreasing R(DCO+). Furthermore, the lower density regions are exposed to FUV, in which the formation of HCO+ is halted, consequently increasing the R(DCO+).
Finally, to further understand how deuterated fractions behave as clumps evolve, we investigate 67 clumps. Utilizing CASCADE observation of the ubiquitous H2CO complemented with higher J-transitions with the APEX telescope, we determine the physical conditions of 67 clumps in Cygnus-X. The methodology of determining the H2 volume density is efficient in probing the bulk of the gas within 0.2 pc of the clumps. With the physical conditions constrained, we model the chemical evolution of these clumps utilizing the plethora of molecules covered with CASCADE, including the 6 deuterated fractions: R(C2D), R(NH2D), R(N2D+), R(DCN), R(DNC), and R(DCO+). We find that the latter two deuterated fractions decrease and increase, respectively, as the clumps evolve and become hotter.
This thesis focuses on probing the deuterated fractions of Cygnus-X. Along the DR21 filament, the deuterated fraction of DCO+, DNC, and DCN exhibit morphological variations, caused by the local physical conditions. Active star-formation along the filamentary structure initiate shock chemistry in these high density region, destroying DCO+, and consequently decreasing R(DCO+). Furthermore, the lower density regions are exposed to FUV, in which the formation of HCO+ is halted, consequently increasing the R(DCO+).
Finally, to further understand how deuterated fractions behave as clumps evolve, we investigate 67 clumps. Utilizing CASCADE observation of the ubiquitous H2CO complemented with higher J-transitions with the APEX telescope, we determine the physical conditions of 67 clumps in Cygnus-X. The methodology of determining the H2 volume density is efficient in probing the bulk of the gas within 0.2 pc of the clumps. With the physical conditions constrained, we model the chemical evolution of these clumps utilizing the plethora of molecules covered with CASCADE, including the 6 deuterated fractions: R(C2D), R(NH2D), R(N2D+), R(DCN), R(DNC), and R(DCO+). We find that the latter two deuterated fractions decrease and increase, respectively, as the clumps evolve and become hotter.
Klassifikation (DDC)
520 Astronomie, KartografieZugehörige Publikation(en)
https://doi.org/10.1051/0004-6361/202450118https://doi.org/10.1051/0004-6361/202558050
Christensen, Ivalu Barlach: Large-scale physical and molecular conditions in structures of Cygnus-X. - Bonn, 2026. - Dissertation, Rheinische Friedrich-Wilhelms-Universität Bonn.
Online-Ausgabe in bonndoc: https://nbn-resolving.org/urn:nbn:de:hbz:5-90698
Online-Ausgabe in bonndoc: https://nbn-resolving.org/urn:nbn:de:hbz:5-90698
@phdthesis{handle:20.500.11811/14363,
urn: https://nbn-resolving.org/urn:nbn:de:hbz:5-90698,
author = {{Ivalu Barlach Christensen}},
title = {Large-scale physical and molecular conditions in structures of Cygnus-X},
school = {Rheinische Friedrich-Wilhelms-Universität Bonn},
year = 2026,
month = aug,
note = {The physical state of the interstellar medium (ISM) is essential for understanding the intricate processes involved in massive star formation within galaxies. The nearby (d ~ 1.5 kpc) molecular cloud, Cygnus-X, harbors multiples sites of high-mass star-formation, allowing us to probe the various stages as stars form and how the chemistry evolve. Within the Cygnus Allscale Survey of Chemistry and Dynamical Environments (CASCADE), we aim to explore the large-scale distribution of deuterated molecules in Cygnus-X. A plethora of star-forming clumps are observed with the CASCADE survey, where clumps are believed to evolve from quiescent infrared-dark clouds to high-mass protostellar objects to hot molecular cores to ultra-compact HII regions. The most active and dense region within Cygnus-X is the DR21 filament, harboring the prominent HII region DR21 Main with the most intense outflow of the Milky Way. The degree of deuteration, R, can significantly enhance over the elemental D/H-ratio (10−5) depending on physical parameters such as temperature, density, and ionization fraction. Deuterated molecules and their molecular D/H-ratios are important diagnostic tools to study the physical conditions of star-forming regions.
This thesis focuses on probing the deuterated fractions of Cygnus-X. Along the DR21 filament, the deuterated fraction of DCO+, DNC, and DCN exhibit morphological variations, caused by the local physical conditions. Active star-formation along the filamentary structure initiate shock chemistry in these high density region, destroying DCO+, and consequently decreasing R(DCO+). Furthermore, the lower density regions are exposed to FUV, in which the formation of HCO+ is halted, consequently increasing the R(DCO+).
Finally, to further understand how deuterated fractions behave as clumps evolve, we investigate 67 clumps. Utilizing CASCADE observation of the ubiquitous H2CO complemented with higher J-transitions with the APEX telescope, we determine the physical conditions of 67 clumps in Cygnus-X. The methodology of determining the H2 volume density is efficient in probing the bulk of the gas within 0.2 pc of the clumps. With the physical conditions constrained, we model the chemical evolution of these clumps utilizing the plethora of molecules covered with CASCADE, including the 6 deuterated fractions: R(C2D), R(NH2D), R(N2D+), R(DCN), R(DNC), and R(DCO+). We find that the latter two deuterated fractions decrease and increase, respectively, as the clumps evolve and become hotter.},
url = {https://hdl.handle.net/20.500.11811/14363}
}
urn: https://nbn-resolving.org/urn:nbn:de:hbz:5-90698,
author = {{Ivalu Barlach Christensen}},
title = {Large-scale physical and molecular conditions in structures of Cygnus-X},
school = {Rheinische Friedrich-Wilhelms-Universität Bonn},
year = 2026,
month = aug,
note = {The physical state of the interstellar medium (ISM) is essential for understanding the intricate processes involved in massive star formation within galaxies. The nearby (d ~ 1.5 kpc) molecular cloud, Cygnus-X, harbors multiples sites of high-mass star-formation, allowing us to probe the various stages as stars form and how the chemistry evolve. Within the Cygnus Allscale Survey of Chemistry and Dynamical Environments (CASCADE), we aim to explore the large-scale distribution of deuterated molecules in Cygnus-X. A plethora of star-forming clumps are observed with the CASCADE survey, where clumps are believed to evolve from quiescent infrared-dark clouds to high-mass protostellar objects to hot molecular cores to ultra-compact HII regions. The most active and dense region within Cygnus-X is the DR21 filament, harboring the prominent HII region DR21 Main with the most intense outflow of the Milky Way. The degree of deuteration, R, can significantly enhance over the elemental D/H-ratio (10−5) depending on physical parameters such as temperature, density, and ionization fraction. Deuterated molecules and their molecular D/H-ratios are important diagnostic tools to study the physical conditions of star-forming regions.
This thesis focuses on probing the deuterated fractions of Cygnus-X. Along the DR21 filament, the deuterated fraction of DCO+, DNC, and DCN exhibit morphological variations, caused by the local physical conditions. Active star-formation along the filamentary structure initiate shock chemistry in these high density region, destroying DCO+, and consequently decreasing R(DCO+). Furthermore, the lower density regions are exposed to FUV, in which the formation of HCO+ is halted, consequently increasing the R(DCO+).
Finally, to further understand how deuterated fractions behave as clumps evolve, we investigate 67 clumps. Utilizing CASCADE observation of the ubiquitous H2CO complemented with higher J-transitions with the APEX telescope, we determine the physical conditions of 67 clumps in Cygnus-X. The methodology of determining the H2 volume density is efficient in probing the bulk of the gas within 0.2 pc of the clumps. With the physical conditions constrained, we model the chemical evolution of these clumps utilizing the plethora of molecules covered with CASCADE, including the 6 deuterated fractions: R(C2D), R(NH2D), R(N2D+), R(DCN), R(DNC), and R(DCO+). We find that the latter two deuterated fractions decrease and increase, respectively, as the clumps evolve and become hotter.},
url = {https://hdl.handle.net/20.500.11811/14363}
}
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