Turbulence and Magnetic Field Alignment in Small Molecular Clouds: The Role of Cloud Size, Mass, and Density
In this study, we investigate the relationship between turbulence (Δ V ) and different physical parameters in 22 isolated small molecular clouds and their cores, extending the analysis to a hierarchical scenario from core to cloud. Using ^12 CO line width as a tracer of turbulence, we find that Δ V...
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2025-01-01
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| author | Bhaskarjyoti Barman Himadri Sekhar Das Pritibhajan Byakti |
| author_facet | Bhaskarjyoti Barman Himadri Sekhar Das Pritibhajan Byakti |
| author_sort | Bhaskarjyoti Barman |
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| description | In this study, we investigate the relationship between turbulence (Δ V ) and different physical parameters in 22 isolated small molecular clouds and their cores, extending the analysis to a hierarchical scenario from core to cloud. Using ^12 CO line width as a tracer of turbulence, we find that Δ V correlates with both cloud size and mass, following $\propto {({L}_{\mathrm{cl}})}^{0.30\pm 0.04}$ and $\propto {({M}_{\mathrm{cl}})}^{0.21\pm 0.08}$ . Further, the surface density of the clouds (Σ _cl ) influences the Δ V – L _cl relation, with ${\rm{\Delta }}V\propto {({L}_{\mathrm{cl}}\times {\Sigma }_{\mathrm{cl}})}^{0.50\pm 0.13}$ . This indicates that gravitational energy drives turbulence in clouds, indicating possible virial equilibrium. We observe that L _cl correlates with M _cl and volume gas density of the cloud ( ρ _cl ), implying nearly constant Σ _cl across the clouds. In cloud cores, C ^18 O line-width data show complex behavior, with no direct correlation between Δ V and core size ( L _co ). However, a positive correlation emerges when the surface density of the core is included in L _co . Notably, the relation between volume gas density ( ρ _co ) and core size ( L _co ) deviates from constant core surface density. Our analysis reveals that turbulent pressure increases with gravitational pressure to maintain global equilibrium. Finally, on the core-to-cloud scale, physical relationships remain continuous, reflecting the interconnected nature of clouds and cores. Extending our previous work, where we demonstrated a nonlinear dependence of turbulence on the alignment of the local magnetic field in molecular clouds with the Galactic plane, we now compare observations with a theoretical model based on kinetic theory. Our result confirms that higher turbulence causes greater magnetic misalignment consistent with the derived second-order polynomial relationship. |
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| language | English |
| publishDate | 2025-01-01 |
| publisher | IOP Publishing |
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| series | The Astrophysical Journal |
| spelling | doaj-art-2b445098961e45eebfe3bbda3273b05b2025-08-20T03:11:42ZengIOP PublishingThe Astrophysical Journal1538-43572025-01-01980225210.3847/1538-4357/ada562Turbulence and Magnetic Field Alignment in Small Molecular Clouds: The Role of Cloud Size, Mass, and DensityBhaskarjyoti Barman0https://orcid.org/0009-0006-7902-1200Himadri Sekhar Das1https://orcid.org/0000-0003-0262-7264Pritibhajan Byakti2https://orcid.org/0000-0001-7412-2463Department of Physics, Assam University , Silchar 788011, India ; bhaskarjyotibarman86@gmail.com, himadri.sekhar.das@aus.ac.inDepartment of Physics, Assam University , Silchar 788011, India ; bhaskarjyotibarman86@gmail.com, himadri.sekhar.das@aus.ac.inPandit Deendayal Upadhyaya Adarsha Mahavidyalaya , Eraligool, Sribhumi 788723, India ; priti137@gmail.comIn this study, we investigate the relationship between turbulence (Δ V ) and different physical parameters in 22 isolated small molecular clouds and their cores, extending the analysis to a hierarchical scenario from core to cloud. Using ^12 CO line width as a tracer of turbulence, we find that Δ V correlates with both cloud size and mass, following $\propto {({L}_{\mathrm{cl}})}^{0.30\pm 0.04}$ and $\propto {({M}_{\mathrm{cl}})}^{0.21\pm 0.08}$ . Further, the surface density of the clouds (Σ _cl ) influences the Δ V – L _cl relation, with ${\rm{\Delta }}V\propto {({L}_{\mathrm{cl}}\times {\Sigma }_{\mathrm{cl}})}^{0.50\pm 0.13}$ . This indicates that gravitational energy drives turbulence in clouds, indicating possible virial equilibrium. We observe that L _cl correlates with M _cl and volume gas density of the cloud ( ρ _cl ), implying nearly constant Σ _cl across the clouds. In cloud cores, C ^18 O line-width data show complex behavior, with no direct correlation between Δ V and core size ( L _co ). However, a positive correlation emerges when the surface density of the core is included in L _co . Notably, the relation between volume gas density ( ρ _co ) and core size ( L _co ) deviates from constant core surface density. Our analysis reveals that turbulent pressure increases with gravitational pressure to maintain global equilibrium. Finally, on the core-to-cloud scale, physical relationships remain continuous, reflecting the interconnected nature of clouds and cores. Extending our previous work, where we demonstrated a nonlinear dependence of turbulence on the alignment of the local magnetic field in molecular clouds with the Galactic plane, we now compare observations with a theoretical model based on kinetic theory. Our result confirms that higher turbulence causes greater magnetic misalignment consistent with the derived second-order polynomial relationship.https://doi.org/10.3847/1538-4357/ada562Star forming regionsMolecular cloudsStellar kinematicsMagnetic fieldsStar formationInterstellar magnetic fields |
| spellingShingle | Bhaskarjyoti Barman Himadri Sekhar Das Pritibhajan Byakti Turbulence and Magnetic Field Alignment in Small Molecular Clouds: The Role of Cloud Size, Mass, and Density The Astrophysical Journal Star forming regions Molecular clouds Stellar kinematics Magnetic fields Star formation Interstellar magnetic fields |
| title | Turbulence and Magnetic Field Alignment in Small Molecular Clouds: The Role of Cloud Size, Mass, and Density |
| title_full | Turbulence and Magnetic Field Alignment in Small Molecular Clouds: The Role of Cloud Size, Mass, and Density |
| title_fullStr | Turbulence and Magnetic Field Alignment in Small Molecular Clouds: The Role of Cloud Size, Mass, and Density |
| title_full_unstemmed | Turbulence and Magnetic Field Alignment in Small Molecular Clouds: The Role of Cloud Size, Mass, and Density |
| title_short | Turbulence and Magnetic Field Alignment in Small Molecular Clouds: The Role of Cloud Size, Mass, and Density |
| title_sort | turbulence and magnetic field alignment in small molecular clouds the role of cloud size mass and density |
| topic | Star forming regions Molecular clouds Stellar kinematics Magnetic fields Star formation Interstellar magnetic fields |
| url | https://doi.org/10.3847/1538-4357/ada562 |
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