ALMA observations of the Red Rectangle, a preliminary analysis

V Bujarrabal,C Sánchez Contreras,H Van Winckel,A Castro-Carrizo,J Alcolea,M Santander-García,R Neri,R Lucas

doi:10.1051/0004-6361/201322232

Abstract

We aim to study equatorial disks in rotation and axial outflows in post-AGB objects, as to disclose the formation and shaping mechanisms in planetary nebulae. So far, both disks and outflows had not been observed simultaneously. We have obtained high-quality ALMA observations of 12CO and 13CO J=3-2 and 12CO J=6-5 line emission in the Red Rectangle, the only post-AGB/protoplanetary object in which a disk in rotation has been mapped up to date. These observations provide an unprecedented description of the complex structure of this source. Together with an equatorial disk in rotation, we find a low-velocity outflow that occupies more or less the region placed between the disk and the optical X-shaped nebula. From our observations and preliminary modeling of the data, we confirm the previously known properties of the disk and obtain a first description of the structure, dynamics, and physical conditions of the outflow.

Highlights

Many protoplanetary nebulae (PPNe) show very massive (∼0.1 M ) and fast (30–200 km s−1) bipolar outflows, which are thought to be crucial in the formation of planetary nebulae; see, e.g., Bujarrabal et al (2001) and Balick & Frank (2004)
We aim to study equatorial disks in rotation and axial outflows in post-asymptotic giant branch (AGB) objects so as to disclose the formation and shaping mechanisms in planetary nebulae
These outflows carry too much linear momentum to be powered by momentum transfer from stellar photons, and the presence of disks rotating around the central stars and reaccretion from them are often postulated for explaining the nebular dynamics (e.g., Soker 2001; Frank & Blackman 2004)

Summary

Introduction

Many protoplanetary nebulae (PPNe) show very massive (∼0.1 M ) and fast (30–200 km s−1) bipolar outflows, which are thought to be crucial in the formation of planetary nebulae; see, e.g., Bujarrabal et al (2001) and Balick & Frank (2004). Recent single-dish observations of 12CO and 13CO mmwave emission in a sample of similar post-AGB stars (close binary stars with low-mass nebulae and indications of compact disks) systematically yielded characteristic line profiles, Appendix A is available in electronic form at http://www.aanda.org with a prominent single or double peak and moderate-velocity wings, which are strikingly similar to those of the Red Rectangle (Bujarrabal et al 2013, Paper II). Indications of molecule-rich outflows were found for other similar sources, in which the disk-like CO profiles show relatively strong line wings (Paper II) All these nebulae, including the Red Rectangle, show low values of the total mass (

Observations

Results and simple modeling of our ALMA maps

Conclusions