A multiwavelength view of the protostellar binary IRAS04325+2402: a case for turbulent fragmentation

TL;DR

This study uses multiwavelength observations to analyze the protostellar binary IRAS04325+2402, providing insights into its structure, formation, and early evolution, and supporting turbulent fragmentation as its formation mechanism.

Contribution

It presents new multiwavelength data and radiative transfer models that support turbulent fragmentation over rotational fragmentation in the formation of this binary system.

Findings

Both objects are very young, likely under 1 million years old.

The system shows significant misalignment in disk and outflow orientations.

Evidence favors turbulent fragmentation as the formation scenario.

Abstract

IRAS04325+2402 (herafter IRAS04325) is a complex protostellar system hosting two young stellar objects (AB and C in the following) at a separation of 1250AU. Here we present new deep Gemini imaging and spectroscopy for the system covering the wavelength regime from 1-12mu as well as Sub-Millimeter Array interferometry at 870mu, in combination with Spitzer and literature data. Object AB is a low-mass star with a disk/envelope system and an outflow cavity, which is prominently seen in infrared images. Object C, previously suspected to be a brown dwarf, is likely a very low mass star, with an effective temperature of ~3400K. It features an edge-on disk and an elongated envelope, and shows strong indications for accretion and ejection activity. Both objects are likely to drive parsec-scale molecular outflows. The two objects are embedded in an isolated, dense molecular cloud core. High extinction, lack of X-ray emission, and relatively high bolometric luminosity argue for a very young age below 1Myr. The disk/outflow systems of AB and C are misaligned by ~60deg against each other and by 80 and 40deg against the orbital plane of the binary. The system might be a good case for primordial misalignment, as opposed to misalignment caused by dynamical interactions, because the outflow direction is constant and the realignment timescale is likely larger than the system age. This favours turbulent fragmentation, rather than rotational fragmentation, as the formation scenario. We show that the spectral energy distributions and images for the two objects can be reproduced with radiative transfer models for disk/envelope systems. Our analysis provides reassurance in the established paradigm for the structure and early evolution of YSOs, but stresses the importance of developing 3D models with sophisticated dust chemistry (abridged).