Morphology of the $^{13}$CO(3-2) millimeter emission across the gas disc surrounding the triple protostar GG Tau A using ALMA observations

TL;DR

This study uses ALMA observations to analyze the gas and dust morphology of the GG Tau A triple protostar system, revealing a rotating gas disc with Keplerian motion, a hot spot, and detailed intensity variations.

Contribution

It provides detailed characterization of the gas disc's properties, including rotation, scale height limits, and intensity variations, expanding previous analyses of GG Tau A.

Findings

Evidence for a Keplerian rotating gas disc

Detection of a hot spot in the southeastern quadrant

Constraints on disc scale height and in-fall velocity

Abstract

Observations by the Atacama Large Millimeter/sub-millimeter Array of the dust continuum and $^{13}$CO(3-2) millimeter emissions of the triple stellar system GG Tau A are analysed, giving evidence for a rotating gas disc and a concentric and coplanar dust ring. The present work complements an earlier analysis (Tang et al. 2016) by exploring detailed properties of the gas disc. A 95% confidence level upper limit of 0.24 arcsec (34 au) is placed on the disc scale height at a distance of 1 arcsec (140 au) from the central stars. Evidence for Keplerian rotation of the gas disc is presented, the rotation velocity reaching ~3.1 kms$^{-1}$ at 1 arcsec from the central stars, and a 99% confidence level upper limit of 9% is placed on a possible in-fall velocity relative contribution. Variations of the intensity across the disc area are studied in detail and confirm the presence of a hot spot in the south-eastern quadrant. However several other significant intensity variations, in particular a depression in the northern direction, are also revealed. Variations of the intensity are found to be positively correlated to variations of the line width. Possible contributions to the measured line width are reviewed, suggesting an increase of the disc temperature and opacity with decreasing distance from the stars.