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Post Info TOPIC: Proto-Planetary Nebula CRL 618


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Planetary Nebula CRL 618
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Title: Collimated Fast Wind in the Pre-Planetary Nebula CRL 618
Authors: Chin-Fei Lee, Ming-Chien Hsu, Raghvendra Sahai

Collimated fast winds (CFWs) have been proposed to operate during the post-AGB evolutionary phase (and even earlier during the late AGB phase), responsible for the shaping of pre-planetary nebulae (PPNs) and young planetary nebulae (PNs). This paper is a follow-up to our previous study of CFW models for the well-studied PPN CRL 618. Previously, we compared our CFW models with optical observations of CRL 618 in atomic and ionic lines and found that a CFW with a small opening angle can readily reproduce the highly collimated shape of the northwestern (W1) lobe of CRL 618 and the bow-like structure seen at its tip. In this paper, we compare our CFW models with recent observations of CRL 618 in CO J=2-1, J=6-5, and H2 1-0 S(1). In our models, limb-brightened shell structures are seen in CO and H2 at low velocity arising from the shocked AGB wind in the shell, and can be identified as the low-velocity (LV) components in the observations. However, the shell structure in CO J=2-1 is significantly less extended than that seen in the observations. None of our models can properly reproduce the observed high-velocity (HV) molecular emission near the source along the body of the lobe. In order to reproduce the HV molecular emission in CRL 618, the CFW is required to have a different structure. One possible CFW structure is the cylindrical jet, with the fast wind material confined to a small cross section and collimated to the same direction along the outflow axis.

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Posts: 131433
Date:
Proto-Planetary Nebula CRL 618
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Title: Submillimeter Array Observation of the Proto-Planetary Nebula CRL 618 in the CO J=6-5 Line
Authors: Jun-ichi Nakashima (1), David Fong (2), Tatsuhiko Hasegawa (1), Naomi Hirano (1), Nico Koning (3), Sun Kwok (1,4), Jeremy Lim (1), Dinh-Van-Trung (1), Ken Young (5) ((1) ASIAA, (2) CfA/SMA, (3) U. of Calgary, (4) U. of Hong Kong, (5) CfA)
(Version v2)

We report on the results of a Submillimeter Array interferometric observation of the proto-planetary nebula CRL 618 in the 12CO J=6-5 line. With the new capability of SMA enabling us to use two receivers at a time, we also observed simultaneously in the 12CO J=2-1 and 13CO J=2-1 lines. The 12CO J=6-5 and 13CO J=2-1 lines were first interferometrically observed toward CRL 618. The flux of the high velocity component of the 12CO J=6-5 line is almost fully recovered, while roughly 80% of the flux of the low velocity component is resolved out. The low recovery rate suggests that the emission region of the low velocity component of the 12CO J=6-5 line is largely extended. Continuum emission is detected both at 230 and 690 GHz. The flux of the 690 GHz continuum emission seems to be partially resolved out, suggesting dust emission partly contaminates the 690 GHz continuum flux. The cavity structure, which has been confirmed in a previous observation in the 12CO J=2-1 line, is not clearly detected in the 12CO J=6-5 line, and only the south wall of the cavity is detected. This result suggests that the physical condition of the molecular envelope of CRL 618 is not exactly axial symmetric.

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