Kinematics of the molecular interstellar medium probed by Gaia: steep velocity dispersion-size relation, isotropic turbulence, and location-dependent energy dissipation

The morphology and kinematics of the molecular interstellar medium are controlled by processes such as turbulence, gravity, stellar feedback, and Galactic shear. Using a sample of 15149 young stellar objects (YSOs) with Gaia Data Release 2 (DR2) astrometric measurements, we study morphology and kinematic structure of their associated molecular gas. We identify 150 YSO associations with distance $d \lesssim 3 \;\rm kpc$. The YSO associations are oriented parallel to the disk midplane, with a median angle of 30$^{\circ}$, and they have a median aspect ratio of 1.97. Along the Galactic longitude direction, the velocity dispersion is related to the separation by $\sigma_{v_l} = 0.58{\;}(r_l/{\rm pc})^{0.66\pm0.05}({\rm km\ s^{-1}})$, along the Galactic latitude direction, $\sigma_{v_b} = 0.54 {\;} (r_b/{\rm pc})^{0.64\pm0.04}({\rm km\ s^{-1}})$, and overall $\sigma_{v,{\rm 2D}} = 0.74 {\;} (r/{\rm pc})^{0.67\pm0.05}({\rm km\ s^{-1}})$. The slope is on the stepper side, yet consistent with previous measurements. The energy dissipation rate of turbulence $\dot{\epsilon} = \sigma_{v,{\rm 3D}}^3 /L$ decreases with the Galactocentric distance $r_{\rm gal}$ by $\dot{\epsilon} = 1.77\times10^{-4}e^{-0.45 \; (r_{\rm gal}/ {\rm kpc})}{\;}({\rm erg\ g^{-1}\ s^{-1}})$ for clouds with $40\; {\rm pc}

Keywords:

• Galaxy
• Young stellar object
• Velocity dispersion
• Astrophysics
• Anisotropy
• Isotropy
• Dissipation
• Interstellar medium
• Physics
• Turbulence

• Correction
• Source
• Cite
• Save
• Machine Reading By IdeaReader