FERIA: Flat Envelope Model with Rotation and Infall under Angular Momentum Conservation

Abstract

Radio observations of low-mass star formation in molecular spectral lines have rapidly progressed since the advent of the Atacama Large Millimeter/submillimeter Array (ALMA). The gas distribution and its kinematics within a few hundreds of astronomical unit scale around a Class 0–I protostar are spatially resolved, and the region where a protostellar disk is being formed is now revealed in detail. In such studies, it is essential to characterize the complex physical structure around a protostar consisting of an infalling envelope, a rotationally supported disk, and an outflow. For this purpose, we have developed a general-purpose computer code “FERIA” (Flat Envelope model with Rotation and Infall under Angular momentum conservation) to generate the image data cube based on the infalling-rotating envelope model and the Keplerian disk model, both of which are often used in observational studies. In this paper, we present the description and the user manual of FERIA and summarize caveats in actual applications. This program outputs cube FITS files, which can be used for direct comparison with observations. It can also be used to generate mock data for machine/deep learning. Examples of these applications are described and discussed to demonstrate how the model analyses work with actual observational data.