Abstract
Gravity plays a determining role in the evolution of the molecular ISM. In 2016, we proposed a measure called gravitational energy spectrum to quantify the importance of gravity on multiple physical scales. In this paper, using a wavelet-based decomposition technique, we derive the gravitational energy spectra of the Orion A and the Orion B molecular cloud from observational data. The gravitational energy spectra exhibit power-law-like behaviours. From a few parsec down to similar to 0.1 pc scale, the Orion A and Orion B molecular cloud have E-p(k) similar to k(-1.88) and E-p(k) similar to k(-2.09), respectively. These scaling exponents are close to the scaling exponents of the kinetic energy power spectrum of compressible turbulence (where E similar to k(-2)), with a near-equipartition of turbulent versus gravitational energy on multiple scales. This provides a clear evidence that gravity is able to counteract effectively against turbulent motion for these length-scales. The results confirm our earlier analytical estimates. For the Orion A molecular cloud, gravity inevitably dominates turbulence inside the cloud. Our results provide a clear observational proof that gravity is playing a determining role in the evolution these molecular clouds from the cloud scale down to similar to 0.1 pc. However, turbulence is likely to dominate in clouds such as California. The method is general and should be applicable to all the astrophysical problems where gravity plays a role.
| Dokumententyp: | Zeitschriftenartikel |
|---|---|
| Fakultät: | Physik |
| Themengebiete: | 500 Naturwissenschaften und Mathematik > 530 Physik |
| ISSN: | 0035-8711 |
| Sprache: | Englisch |
| Dokumenten ID: | 55721 |
| Datum der Veröffentlichung auf Open Access LMU: | 14. Jun. 2018, 10:00 |
| Letzte Änderungen: | 04. Nov. 2020, 13:36 |
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