Kinematic properties of the TW Hya association
TLDR
A kinematic analysis of the TW Hya association confirms its expansion and age, but finds conflicting evidence for rigid-body rotation.
Key contributions
- Performed a kinematic analysis of the young stellar TW Hya association.
- Confirmed the association's volume expansion (103 km/s/kpc) and estimated its dynamical age (9.7 Myr).
- Presented conflicting evidence for rigid-body rotation, with one method suggesting rotation and another showing none.
Why it matters
Understanding the kinematics of young stellar associations like TW Hya is crucial for modeling star formation and evolution. This paper provides new insights into its expansion and age, while highlighting the complexities of determining rotational properties in such systems.
Original Abstract
A kinematic analysis of the young stellar association TWHya has been performed. The components of the displacement matrix in the Ogorodnikov-Milne linear model have been estimated both graphically and by solving the basic kinematic equations. The association's volume expansion with a coefficient of $K_{xyz}=103\pm9$ km s$^{-1}$ kpc$^{-1}$ was confirmed, which yields a dynamical age estimate of $t=9.7 \pm0.8$ Myr. Using the graphical method, estimates of the association's proper rigid-body rotation parameters $ω$ around the galactic axes x and y have been obtained for the first time, with velocity values in the range of 50-70 km s$^{-1}$ kpc$^{-1}$ and errors in their determination of 14-19 km s$^{-1}$ kpc$^{-1}$. However, these values are not confirmed by another method. For example, when solving kinematic equations only using proper motions, all three components of rigid body rotation do not differ significantly from zero, $(ω_x,ω_y,ω_z)=(4,7,11)\pm(5,5,5)$ km s$^{-1}$ kpc$^{-1}$.
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