The first ALMA view of IRAS 16293-2422: Direct detection of infall onto source B and high-resolution kinematics of source A

TL;DR

This study uses high-resolution ALMA observations to detect infall and analyze the kinematics of gas in the proto-binary IRAS 16293-2422, revealing infall onto source B and rotational motion in source A.

Contribution

First detection of infall onto source B via inverse P-Cygni profiles and detailed kinematic analysis of both sources using ALMA's high spectral resolution.

Findings

Infall rate of 4.5x10^-5 Msun/yr onto source B

Detection of rotation in source A with an axis near the line-of-sight

Infall detection challenges the T Tauri star hypothesis for source B

Abstract

Aims: We focus on the kinematical properties of a proto-binary to study the infall and rotation of gas towards its two protostellar components. Methods: We present ALMA Science Verification observations with high-spectral resolution of IRAS 16293-2422 at 220.2 GHz. The wealth of molecular lines in this source and the very high spectral resolution offered by ALMA allow us to study the gas kinematics with unprecedented detail. Results: We present the first detection of an inverse P-Cygni profile towards source B in the three brightest lines. The line profiles are fitted with a simple two-layer model to derive an infall rate of 4.5x10^-5 Msun/yr. This infall detection would rule-out the previously suggested possibility that source B is a T Tauri star. A position velocity diagram for source A shows evidence for rotation with an axis close to the line-of-sight.