ATOMIUM: ALMA tracing the origins of molecules in dust forming oxygen rich M-type stars: Motivation, sample, calibration, and initial results
Journal article, 2022
This overview paper presents atomium, a Large Programme in Cycle 6 with the Atacama Large Millimeter/submillimeter Array (ALMA). The goal of atomium is to understand the dynamics and the gas phase and dust formation chemistry in the winds of evolved asymptotic giant branch (AGB) and red supergiant (RSG) stars. A more general aim is to identify chemical processes applicable to other astrophysical environments. Seventeen oxygen-rich AGB and RSG stars spanning a range in (circum)stellar parameters and evolutionary phases were observed in a homogeneous observing strategy allowing for an unambiguous comparison. Data were obtained between 213.83 and 269.71 GHz at high (0.025-0.050), medium (0.13-0.24), and low (~1) angular resolution. The sensitivity per ~1.3 km s-1 channel was 1.5-5 mJy beam-1, and the line-free channels were used to image the millimetre wave continuum. Our primary molecules for studying the gas dynamics and dust formation are CO, SiO, AlO, AlOH, TiO, TiO2, and HCN; secondary molecules include SO, SO2, SiS, CS, H2O, and NaCl. The scientific motivation, survey design, sample properties, data reduction, and an overview of the data products are described. In addition, we highlight one scientific result - the wind kinematics of the atomium sources. Our analysis suggests that the atomium sources often have a slow wind acceleration, and a fraction of the gas reaches a velocity which can be up to a factor of two times larger than previously reported terminal velocities assuming isotropic expansion. Moreover, the wind kinematic profiles establish that the radial velocity described by the momentum equation for a spherical wind structure cannot capture the complexity of the velocity field. In fifteen sources, some molecular transitions other than 12CO v = 0 J = 2 - 1 reach a higher outflow velocity, with a spatial emission zone that is often greater than 30 stellar radii, but much less than the extent of CO. We propose that a binary interaction with a (sub)stellar companion may (partly) explain the non-monotonic behaviour of the projected velocity field. The atomium data hence provide a crucial benchmark for the wind dynamics of evolved stars in single and binary star models.
Astrochemistry
Circumstellar matter
Stars: mass-loss
Binaries: general
Stars: AGB and post-AGB
Instrumentation: interferometers
Author
C. A. Gottlieb
Harvard-Smithsonian Center for Astrophysics
L. Decin
University of Leeds
KU Leuven
A. M.S. Richards
University of Manchester
F. De Ceuster
KU Leuven
University College London (UCL)
W. Homan
KU Leuven
Sofia Wallström
KU Leuven
Taissa Danilovich
KU Leuven
T.J. Millar
Queen's University Belfast
M. Montargès
Paris Observatory
KU Leuven
K. T. Wong
Institut de Radioastronomie Millimétrique (IRAM)
I. McDonald
University of Manchester
Open University
A. Baudry
University of Bordeaux
J. Bolte
KU Leuven
E. Cannon
KU Leuven
Elvire De Beck
Chalmers, Space, Earth and Environment, Astronomy and Plasmaphysics
A. de Koter
KU Leuven
Anton Pannekoek Institute for Astronomy
I. El Mellah
Departement Wiskunde
KU Leuven
S. Etoka
University of Manchester
D. Gobrecht
KU Leuven
M. Gray
National Astronomical Research Institute of Thailand
University of Manchester
F. Herpin
University of Bordeaux
M. Jeste
Max Planck Society
P. Kervella
Paris Observatory
Theo Khouri
Chalmers, Space, Earth and Environment, Astronomy and Plasmaphysics
E. Lagadec
Observatoire de la Cote d'Azur
S. Maes
KU Leuven
J. Malfait
KU Leuven
K. Menten
Max Planck Society
Holger Muller
University of Cologne
B. Pimpanuwat
National Astronomical Research Institute of Thailand
University of Manchester
J. M. C. Plane
University of Leeds
R. Sahai
California Institute of Technology (Caltech)
M. Van De Sande
KU Leuven
University of Leeds
Lbfm Waters
Netherlands Institute for Space Research (SRON)
Radboud University
J. A. Yates
University College London (UCL)
A. Zijlstra
University of Manchester
The University of Hong Kong
Astronomy and Astrophysics
0004-6361 (ISSN) 1432-0746 (eISSN)
Vol. 660 A94Subject Categories (SSIF 2011)
Astronomy, Astrophysics and Cosmology
Atom and Molecular Physics and Optics
Geophysics
DOI
10.1051/0004-6361/202140431