2008ApJ...683..862C

We present interferometric observations of the isolated, low-mass protostellar double cores CG 30 and BHR 71 in the N₂H⁺ (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 ∼21.7" (∼8700 AU). In BHR 71, strong dust-continuum emission is detected at the position of the mid-infrared source IRS 1, while only weak emission is detected from the secondary mid-infrared source IRS 2. Assuming the standard gas-to-dust ratio and optically thin 3 mm dust-continuum emission, we derive hydrogen gas masses of 0.05-2.1 M_☉ for the four subcores. N₂H⁺ (1-0) line emission is detected in both CG 30 and BHR 71. By simultaneously fitting the seven hyperfine line components of N₂H⁺, we derive the velocity fields and find symmetric velocity gradients in both sources. Estimated virial masses of the subcores range from 0.1 to 0.6 M_☉. Spitzer images show the mid-infrared emission from all four subcores, which is spatially associated with the 3 mm dust-continuum emission. All four sources appear to drive their own outflows, as seen in the Spitzer 4.5 µm images. Based on the ATCA and Spitzer observations, we construct spectral energy distributions (SEDs) and derive temperatures and luminosities for all cores. We suggest that the subcores 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.