Submillimeter Observations of the Young Low-Mass Object IRAS 04158+2805

TL;DR

This study uses high-resolution submillimeter observations to analyze the gas and dust environment of the young low-mass star IRAS 04158+2805, revealing a toroidal dust structure and signs of rotation.

Contribution

It provides detailed imaging and kinematic analysis of a low-mass young stellar object, supporting star formation via core collapse rather than ejection.

Findings

Revealed a large, elongated dust structure aligned with optical absorption features.

Detected a velocity gradient consistent with rotation, implying a low-mass central object.

Suggested the environment includes a flattened envelope or circumbinary ring.

Abstract

We present high spatial resolution Submillimeter Array observations and supplementary single-dish photometry of the molecular gas and dust around IRAS 04158+2805, a young source with spectral type M5-M6 in the Taurus star-forming region. A bright, highly elongated dust structure that extends 8" (~1120 AU) in diameter is revealed in a 883 micron thermal continuum image. This emission geometry is in good agreement with optical observations that show a similar structure in absorption, aligned perpendicular to bipolar scattered light nebulae. However, the interferometric data also clearly demonstrate that the submillimeter continuum emission is not centrally concentrated, but rather appears to have a toroidal geometry with substantially lower intensities inside a radius of ~250-300 AU. Spatially resolved emission from the CO J=3-2 transition exhibits a velocity gradient along the major axis of the dust structure. If this kinematic pattern is interpreted as the signature of rotation around a central object, a relatively low mass is inferred (M_star = 0.3 M_sun, with a ~50% uncertainty). We discuss several possible explanations for the observed gas and dust environment around IRAS 04158+2805, including a flattened envelope with an outflow cavity and a large circumbinary ring. This source offers unique views of the gas and dust environment surrounding a young low-mass stellar system. Its properties are generally not commensurate with formation scenarios for such low-mass objects that rely on dynamical ejection, but rather confirms that a single mechanism - molecular cloud core collapse and fragmentation - can produce stars over a wide range of stellar masses (at least an order of magnitude).