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A Tough Egg to Crack

Published online by Cambridge University Press:  30 December 2019

Jeremy Lim
Affiliation:
Department of Physics, The University of Hong Kong, Pokfulam Road, Hong Kong email: jjlim@hku.hk
Dinh- van-Trung
Affiliation:
Institute of Physics, Vietnam Academy of Science and Technology, 10 DaoTan, ThuLe, BaDinh, Hanoi, Vietnam email: dvtrung@iop.vast.ac.vn
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Abstract

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The sculpting of the Egg Nebula continues to defy a coherent explanation. Bipolar outflows from the center of the nebula have created bipolar optical lobes that are illuminated by searchlight beams; multiple bipolar outflows orthogonal to the lobes create the appearance of a dark lane; and quasi-circular arcs are imprinted on an approximately spherically-symmetric wind from the progenitorAGB-star. Here, we use archival data from ALMA to study at high angular resolution dust and molecular gas at the center of the nebula. We find that: (i) dust is concentrated in multiple blobs that outline the base of the northern optical lobe; (ii) dense molecular gas forms the wall of a channel swept up and compressed by the outflows that created the bipolar optical lobes; (iii) the expansion and illumination center of the nebula lies at or close to center of the outflow channel. We present a simple working model for the Egg Nebula, and highlight the difficulties that any model face for explaining all the features seen in this nebula.

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