Space reconstruction of the morphology and kinematics of axisymmetric radio sources

Abstract

The unprecedented quality of the observations available from the Atacama Large Millimetre/sub-millimetre Array (ALMA) calls for analysis methods making the best of them. Reconstructing in space the morphology and kinematics of radio sources is an underdetermined problem that requires imposing additional constraints for its solution. The hypothesis of rotational invariance about a well-defined star axis, which is a good approximation to the description of the gas envelopes of many evolved stars and protostars, is particularly efficient in this role. In the first part of the article, a systematic use of simulated observations allows for identifying the main problems and for constructing quantities aimed at solving them. In particular the evaluation of the orientation of the star axis in space and the differentiation between expansion along the star axis and rotation about it are given special attention. The use of polar rather than Cartesian sky coordinates is shown to better match the morphology and kinematics of actual stars. The radial dependence of the gas density and temperature and the possible presence of velocity gradients are briefly considered. In the second part, the results obtained in the first part are applied to a few stars taken as examples with the aim of evaluating their usefulness when applied to concrete cases. A third part takes stock of what precedes and formulates some guidelines for modelling the radio emission of axisymmetric radio sources, limited however to the mathematics and geometry of the problem, physics considerations being ignored.

21 pages, 19 figures, published MNRAS 461, 4276 (2016)

References in corpus (4)

• Formation of a Keplerian disk in the infalling envelope around L1527 IRS: transformation from infalling motions to Kepler motions
• ALMA data suggest the presence of a spiral structure in the inner wind of CW Leo
• The multi-scale environment of RS Cnc from CO and HI observations
• Morphology and kinematics of the gas envelope of protostar L1527 as obtained from ALMA observations of the C${}^{18}$O(2-1) line emission

Cited by in corpus (6)

• The morpho-kinematics of the circumstellar envelope around the AGB star EP Aqr
• Observation of narrow polar jets in the nascent wind of oxygen-rich AGB star EP Aqr
• ALMA observations of the circumstellar envelope around EP Aqr
• The nascent wind of AGB star R Doradus: evidence for a recent episode of enhanced mass loss
• High resolution ALMA observation of the ${}^{12}$CO(3-2) and 350 GHz continuum emissions of the debris disc of 49 Ceti
• De-projection of radio observations of axi-symmetric expanding circumstellar envelopes