N ov 2 00 3 Proper motion and kinematics of the ansae in NGC 7009
نویسنده
چکیده
We have measured the proper motion (PM) and kinematics of the ansae in NGC 7009 using high dispersion echelle spectra and archive narrow band HST images. Assuming that the ansae are moving at equal and opposite velocities from the central star we obtain a system radial velocity of −53± 2 km.s, the eastern ansa approaching and the western ansa receding at vr = 5.3± 1 km.s −1 with respect to this value. The PM of the eastern ansa is 28± 8 mas.yr, which with our weighted distance to NGC 7009 of 0.86±0.34 kpc gives Vexp = 112±32 km.s. The electron temperature and density in both ansae were determined to be Te ∼ 9000± 400 K and ne ∼ 2300± 400 cm . The dynamic age of the ansae is ∼ 925 ± 260 yrs. and the implied PM of the central star is μCS = 1 ± 0.5 mas.yr. This is in qualitative but not quantitative agreement with previous work. Subject headings: astrometry — ISM: kinematics and dynamics — planetary nebulae: individual (NGC7009)
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