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(Galaxy:) open clusters and associations: general
Abstract:
The fundamental plane (FP) is the relation between the surface brightness (I), velocity dispersion (σ) and radius (R). The tilt of FP from the virial plane (R = σ2 I) not only tells the dynamical states of the system but also its formation and evolution. We motivate to looking for an FP in Galactic open clusters (OCs). To form a sample of OCs, we access the most recent DR 14 data from the SDSS/APOGEE2 and the Gaia-ESO survey. Membership of stars is determined via radial velocity and metallicity, plus star's location in the color-magnitude diagram. Besides the velocity dispersion (σrv) obtained from SDSS/APOGEE2 & Gaia-ESO, the average surface brightness (IKs), and apparent radii (r2) of OCs are taken from known OC catalog. A weak relation is found: log(r2) ~ -0.34 * log(σ) - 0.08 * IKs. An implication of this FP needs further investigation.
