We present millimeter interferometric observations of the young stellar object SVS 13 in NCG 1333 in the N _ { 2 } H ^ { + } ( 1–0 ) line and at 1.4 and 3 mm 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 VLA 3 ) in SVS 13 .
With the dust continuum images , we derive gas masses of 0.2 - 1.1 M _ { \odot } for the sources .
N _ { 2 } H ^ { + } ( 1–0 ) line emission is detected and spatially associated with the dust continuum sources B and VLA 3 .
The observed mean line width is \sim 0.48 km s ^ { -1 } and the estimated virial mass is \sim 0.7 M _ { \odot } .
By simultaneously fitting the seven hyperfine line components of N _ { 2 } H ^ { + } , we derive the velocity field and find a symmetric velocity gradient of \sim 28 km s ^ { -1 } pc ^ { -1 } across sources B and VLA 3 , which could be explained by core rotation .
The velocity field suggests that sources B and VLA 3 are forming a physically bound protobinary system embedded in a common N _ { 2 } H ^ { + } 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 SVS 13 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 VLA 3 ) was formed by rotational fragmentation of a single collapsing sub-core .