The large-scale ionized outflow of CH Cygni

Hubble Space Telescope (HST) and ground-based [O II] and [N II] images obta ined in the period 1996-1999 reveal a complex, ionized optical nebula aroun d the symbiotic binary CH Cyg extending out to 18" or 5000 AU from the cent ral stars. The observed velocity range of the nebula, derived from long-sli t echelle spectra, is 130 km s(-1). In spite of its complex appearance, the velocity data show that the basic morphology of the inner regions of the o ptical nebula is that of a bipolar outflow extending nearly along the plane of the sky out to some 2000 AU from the center. Even if the extension of t his bipolar outflow and its position angle are consistent with those of the radio jet produced in 1984 (extrapolated to the time of our optical imager y), no obvious optical counterpart is visible to the original, dense radio bullets ejected by the system. We speculate that the optical bipolar outflo w might be the remnant of the interaction of the bullets with a relatively dense circumstellar medium.