We present interferometric observations with resolution of \sim 3 ^ { \prime \prime } of the isolated , low-mass protostellar double cores CG 30 and BHR 71 in the N _ { 2 } H ^ { + } ( 1 - 0 ) line and at 3 mm dust continuum , using the Australian Telescope Compact Array ( ATCA ) .
The results are complemented by infrared data from the Spitzer Space Telescope .
In CG 30 , the 3 mm dust continuum images resolve two compact sources with a separation of \sim 21 \farcs 7 ( \sim 8700 AU ) .
In BHR 71 , strong dust continuum emission is detected at the position of the mid-infrared source IRS1 , while only weak emission is detected from the secondary mid-infrared source IRS2 .
Assuming standard gas to dust ratio and optically thin 3 mm dust continuum emission , we derive hydrogen gas masses of 0.05 - 2.1 M _ { \odot } for the four sub-cores .
N _ { 2 } H ^ { + } ( 1 - 0 ) line emission is detected in both CG 30 and BHR 71 , and is spatially associated with the thermal dust continuum emission .
By simultaneously fitting the seven hyperfine line components of N _ { 2 } H ^ { + } , we derive the velocity fields and find symmetric velocity gradients in both sources .
Assuming that these gradients are due to core rotation , we estimate the specific angular momenta and ratios of rotational energy to gravitational energy for all cores .
Estimated virial masses of the sub-cores range from 0.1 - 0.6 M _ { \odot } .
We also find that the N _ { 2 } H ^ { + } emission is strongly affected by the outflows , both in terms of entrainment and molecule destruction . Spitzer images show the mid-infrared emission from all four sub-cores , which is spatially associated with the 3 mm dust continuum emission .
All four sources appear to drive their own outflows , as seen in the shock-excited 4.5 \mu m images .
Based on the ATCA and Spitzer observations , we construct spectral energy distributions ( SEDs ) and derive temperatures and luminosities for all cores .
The analysis of the SEDs suggests an evolutionary discrepancy between the two sub-cores in both CG 30 and BHR 71 , which could be due to effects of relative inclinations .
Based on the morphology and velocity structure , we suggest that the sub-cores in CG 30 were formed by initial fragmentation of a filamentary prestellar core , while those in BHR 71 could originate from rotational fragmentation of a single collapsing protostellar core .