# High resolution ALMA observation of the $^{12}$CO(3-2) and 350 GHz continuum emissions of the debris disc of 49 Ceti

## TL;DR

This study uses high-resolution ALMA data to analyze the gas and dust structure of the debris disc around 49 Ceti, revealing shared orientation, gas homogeneity, Keplerian rotation, and a CO deficit at certain velocities.

## Contribution

It provides detailed spatial and kinematic characterization of the gas and dust in 49 Ceti's debris disc using new high-resolution ALMA observations.

## Key findings

- Gas disc is more homogeneous and thinner than dust disc.
- Keplerian rotation is confirmed across a broad range of radii.
- Significant CO emission deficit at velocities near the systemic velocity.

## Abstract

We present high resolution ALMA observations of the CO(3-2) and 350 GHz continuum emissions of the debris disc of 49 Ceti, known to be particularly rich in molecular gas in spite of its age. The main new results are: i) both CO and dust discs share a same position angle and a same inclination but the gas disc is more homogeneous, more central and thinner than the dust disc; ii) evidence is obtained for a significant deficit of observed CO(3-2) emission at Doppler velocities differing from the star systemic velocity by less than 1 \kms; iii) gas velocities are accurately measured and found Keplerian over a broad range of disc radii; iv) the observed CO(3-2) line width is dominated by Keplerian shear and upper limits are obtained to the intrinsic line width. Simple phenomenological models of both CO(3-2) and \mbox{350 GHz} continuum emissions are presented, requiring the use of only very few parameters. The results are discussed in the frame of currently favoured models.