AAS 197, January 2001
Session 6. Planetary Nebulae: Young and Old
Display, Monday, January 8, 2001, 9:30am-7:00pm, Exhibit Hall

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[6.06] Near-Infrared and Millimeter-Wave Imaging of the Young Bipolar Planetary Nebula AFGL 618

R. Sahai, C. Sanchez Contreras (Jet Propulsion Laboratory/Caltech), M. Morris (UCLA)

AFGL 618 is a young, bipolar planetary nebula (PN) in which HST imaging has recently revealed the presence of multiple, highly-collimated lobes. These lobes probably result from the hydrodynamic interaction of multiple high-speed, jet-like outflows with a surrounding dense circumstellar envelope resulting from mass-loss by the progenitor AGB star. Such outflows have been proposed to be the primary agent for producing the complex aspherical structures observed in PNe (Sahai & Trauger 1998). AFGL 618 is thus one of the prime objects for the detailed study of these outflows in the quest for understanding their nature and impact on the surrounding envelope.

We report the results of a multi-wavelength study of AFGL 618 using the Keck 2 telescope at Mauna Kea and the OVRO millimeter-wave interferometer. We have recently obtained high-sensitivity near-infrared imaging in various continuum (at 1.25, 1.65, 2.26 & 3.08\,\mum) and narrow emission-line filters ([FeII]\,1.647\,\mum, H2\,S(1)\,2.125\,\mum, Br\gamma\,2.165\,\mum, & CO\,v=2-0\,2.297\,\mum). We have also partly completed high angular-resolution imaging observations of the millimeter-wave HCO+ and HCN J=1-0 lines from AFGL 618 at OVRO. The near-infrared images show not only the presence of the collimated lobes seen at optical wavelengths with HST, but also more deeply embedded regions of shocked gas, specially within the optically-obscured equatorial toroid separating the optical lobes of the bipolar nebula. Although the central star is deeply embedded and optically invisible, the longest-wavelength Keck images show a very bright compact central peak, which probably corresponds to the location of the central star. Detailed modelling of the near-infrared and millimeter-wave data, in order to understand the physical structure of the lobes, the surrounding extended molecular envelope and the dense equatorial toroid, is in progress.

This work is funded by NASA through a Long Term Space Astrophysics grant. [EOB]

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The author(s) of this abstract have provided an email address for comments about the abstract: sahai@grandpa.jpl.nasa.gov

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