Oral Presentation
Turbulence modes and star formation efficiency in the Milky Way
Presenter: Raffaele Rani (NTNU)
The nature of turbulence in molecular clouds is one of the driving factors that
influence star formation efficiency. It is speculated that the high star formation
efficiency observed in spiral-arm clouds is linked to the prevalence of compressive
(curl-free) turbulent modes, while the shear-driven solenoidal (divergence-free)
modes appear to be the main cause of the low star formation efficiency that
characterises clouds in the Central Molecular Zone (CMZ). Similarly, the anal-
ysis of the Orion B molecular cloud confirmed that, although turbulent modes
vary locally and at different scales within the cloud, the dominant solenoidal
turbulence is compatible with its low star formation rate. This evidence points
to inter-and intra-cloud fluctuations of the solenoidal modes being an agent
for the variability of star formation efficiency. We present a quantitative esti-
mation of the relative fractions of momentum density in the solenoidal modes
of turbulence in a large sample of plane molecular clouds in the 13CO/C18O
(J = 3 → 2) Heterodyne Inner Milky Way Plane Survey (CHIMPS). Our goal
is to obtain a quantitative estimation of the fraction of solenoidal and compres-
sive modes across clouds with varying features, and to compare their ratio to the
star-formation efficiency, derived independently. We investigate how different
fractions of compressive and solenoidal modes may probe the variation of the
star formation efficiency in different Galactic molecular environments.
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