Asymmetric Dust Jets and Extended Structure of 22P/Kopff Observed During 2009 Appearance

Abstract

Abstract 22P/Kopff images were taken with Multicolor Imaging Telescopes for Survey and Monstrous Explosions (MITSuME) 3ch simultaneous CCD cameras on the Ishigakijima astronomical observatory 105-cm telescope and a 2kCCD camera on the Kiso 105-cm Schmidt telescope from 2009 August to December after the passage of its perihelion on 2009 May 25. We confirmed that the near-nuclear fan-shaped jet structure extended toward the south. Whereas we detected a dust trail structure on the project orbit of the parent nucleus, we could not confirm the obvious neck-line structure. We deduced a pole orientation of ($ \alpha_{\rm pl}$ , $ \delta_{\rm pl}$ ) $ =$ (302$ \pm$ 30, 62$ \pm$ 10) or ($ \alpha_{\rm pl}$ , $ \delta_{\rm pl}$ ) $ =$ (122$ \pm$ 30, $-$ 62 $ \pm$ 10) in the case of prograde or retrograde rotation, based on the fan-shaped jet. In addition, we conducted a model simulation of the dust orbital evolution, and found that the observed dust morphology of the fan-shaped jet and dust trail can well explain the dust emission near the south polar region. Finally, we conclude that the surface of 22P/Kopff is becoming largely dormant, but the polar region is still active, as we saw in the Deep Space 1 image of 19P/Borrelly.