A multiwavelength view of the protostellar binary IRAS 04325+2402: a case for turbulent fragmentation

Abstract

IRAS 04325+2402 (hereinafter IRAS 04325) is a complex protostellar system hosting two young stellar objects (AB and C) at a separation of 1250 au. Here, we present a new deep Gemini imaging and spectroscopy for the system covering the wavelength regime from 1 to 12 μm as well as Submillimeter Array interferometry at 870 μm, in combination with Spitzer and literature data. Based on this rich data set, we provide a comprehensive picture of IRAS 04325 over scales from a few au to several parsec. Object AB is a low‐mass star with a disc/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 ∼3400 K. It features an edge‐on disc and an elongated envelope, and shows strong indications for accretion and ejection activities. 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 1 Myr. The disc/outflow systems of objects AB and C are misaligned by ∼60° against each other and by 80° and 40° 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 time‐scale 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 disc/envelope systems. Our analysis provides reassurance in the established paradigm for the structure and early evolution of young stellar objects, but stresses the importance of developing three‐dimensional models with sophisticated dust chemistry.

Complex Structure in Class 0 Protostellar Envelopes. Ii. Kinematic Structure From Single-Dish and Interferometric Molecular Line Mapping

“…The primary is possibly a sub-arcsecond binary with a wider companion separated by 8.2 (Hartmann et al 1999). The 8µm extinction around IRAS 04325 was found in our envelope study but not published in Paper I due to its low signal-to-noise; however, Scholz et al (2010) noticed the 8µm extinction in their study of the system. These authors pointed out that there is a bright diffuse region of emission at 3.6 and 4.5µm, at the peak of the 8µm extinction.…”

The young low-mass star ISO-Oph-50: extreme variability induced by a clumpy, evolving circumstellar disc

“…The colours near minimum are only slightly redder than expected for a mid M dwarf (according to BCAH, H − K ∼ 0.2 − 0.3, J − K ∼ 1.0), in line with the presence of an edge-on disk, as in this case the radiation near minimum is expected to be dominated by scattered light, which makes the object appear bluer (for reference, see the models by (Kenyon et al 1993)). This is not unlike the color-magnitude trends seen in other young sources seen through an edge-on disk (Scholz et al 2010;Jayawardhana et al 2002).…”

RESOLVED DEPLETION ZONES AND SPATIAL DIFFERENTIATION OF N2H+AND N2D+

“…IRAS 04325+2402 -This protostar is a multiple Class I source in Taurus, but with a large, dense core in close proximity, approximately located at (10, 25) in Figure 6 and offset from the protostar by ∼63 (Scholz et al 2010;Hogerheijde & Sandell 2000). The peak N 2 H + emission is found to be north of the protostar, coincident with the nearby dense core seen in 8 µm extinction, with emission extending southward toward the protostars.…”