IRAM-PdBI Observations of Binary Protostars I: The Hierarchical System SVS13 in NGC1333

TL;DR

This study uses millimeter interferometry and infrared data to analyze the hierarchical structure and formation processes of the binary protostar system SVS13 in NGC1333, revealing core rotation and fragmentation mechanisms.

Contribution

It provides the first detailed millimeter and infrared observational analysis of SVS13, highlighting hierarchical fragmentation and core rotation in binary protostar formation.

Findings

Sources B and VLA3 form a bound protobinary system.

Hierarchical fragmentation explains the formation of multiple sources.

Velocity gradient suggests core rotation.

Abstract

We present millimeter interferometric observations of the young stellar object SVS13 in NCG1333 in the N2H+(1-0) line and at 1.4 and 3mm dust continuum, using the IRAM Plateau de Bure interferometer. The results are complemented by infrared data from the Spitzer Space Telescope. The millimeter dust continuum images resolve four sources (A, B, C, and VLA3) in SVS13. With the dust continuum images, we derive gas masses of 0.2-1.1 M_sun for the sources. N2H+(1-0) line emission is detected and spatially associated with the dust continuum sources B and VLA3. The observed mean line width is ~0.48 km/s and the estimated virial mass is ~0.7 M_sun. By simultaneously fitting the seven hyperfine line components of N2H+, we derive the velocity field and find a symmetric velocity gradient of about 28 km/s/pc across sources B and VLA3, which could be explained by core rotation. The velocity field suggests that sources B and VLA3 are forming a physically bound protobinary system embedded in a common N2H+ core. Spitzer images show mid-infrared emission from sources A and C, which is spatially associated with the mm dust continuum emission. No infrared emission is detected from source B, implying that the source is deeply embedded. Based on the morphologies and velocity structure, we propose a hierarchical fragmentation picture for SVS13 where the three sources (A, B, and C) were formed by initial fragmentation of a filamentary prestellar core, while the protobinary system (sources B and VLA3) was formed by rotational fragmentation of a single collapsing sub-core.