Collimated Fast Wind in the Preplanetary Nebula CRL 618

Abstract

Collimated fast winds (CFWs) have been proposed to operate during the post asymptotic giant branch (post-AGB) evolutionary phase (and even earlier during the late AGB phase), responsible for the shaping of preplanetary 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 bowlike 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 H 2 1-0 S(1). In our models, limb-brightened shell structures are seen in CO and H 2 at low velocity (LV) arising from the shocked AGB wind in the shell, and can be identified as the 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.

The jet feedback mechanism (JFM) in stars, galaxies and clusters

“…Many new observations and theoretical studies since the turn of the Millennium further consolidated the jet-shaping scenario of many PNe (e.g., Parthasarathy et al 2000;Bujarrabal et al 2001;Miranda et al 2001;Corradi et al 2001b;Guerrero et al 2001;Imai et al 2002;Riera et al 2003;Vinković et al 2004;Huggins et al 2004;Peña et al 2004;Balick & Hajian 2004;Arrieta et al 2005;Oppenheimer et al 2005;Sahai et al 2005;Vlemmings et al 2006;Miranda et al 2010;Nakashima et al 2010;Phillips et al 2010;Sahai et al 2011;Szyszka et al 2011;López et al 2012;Clark et al 2013;Pérez-Sánchez et al 2013;Vlemmings et al 2014;Fang et al 2015 Dennis et al 2008Dennis et al , 2009Lee et al 2009;Huarte-Espinosa et al 2012;Velázquez et al 2012;Balick et al 2013;Velázquez et al 2014 for theoretical studies; these papers composed a small fraction of the papers studying jets in PNe). X-ray observations seem also to support the presence of jet-inflated bubbles and of jets Sahai et al 2003), similar to X-ray jets in symbiotic systems (e.g., Kellogg et al 2001;Galloway & Sokoloski 2004).…”

STIS optical spectroscopy of the lobes of CRL 618

“…The first scenario should be ruled out as responsible for the high velocity molecular outflow in CRL 618 due to the high density values derived from the optical lines (Suttner et al 1997). The presence of a molecular A118, page 8 of 9 jet in CRL 618 was proposed by Sánchez Contreras et al (2004) and Lee et al (2009). The presence of a molecular jet, which could not originate from the source of the HII region, reinforces the binary system scenario (with the jet source in orbital motion around a remnant AGB star) for CRL 618.…”

“…The existence of a time dependent collimated outflow or jet acting during the PPN transition phase has been studied over the last 10 years. Periodic variations of the ejection velocity have been recently invoked to reproduce the morphology and kinematics of the PPNe Hen 3-1475 (Velázquez et al 2004), and CRL 618 (Lee 2009) and the outer bow-shocks of the point-symmetric PN IC 4634 (Guerrero et al 2008). Planetary nebulae simulations have also been carried forward which include the efects of clumps (Steffen & López 2004).…”

Distinguishing post-AGB impostors in a sample of pre-main sequence stars

“…The most recent results for PDS465 are presented by Lee et al (2009) (2008), among others. CO emission associated to PDS581 has been reported by Urquhart et al (2008).…”