THE INITIAL CONDITIONS OF CLUSTERED STAR FORMATION. I. NH₃OBSERVATIONS OF DENSE CORES IN OPHIUCHUS

We present combined interferometer and single dish telescope data of NH 3 ( J , K ) = (1,1) and (2,2) emission toward the clustered star forming Ophiuchus B, C, and F Cores at high spatial resolution (∼1200 AU) using the Australia Telescope Compact Array, the Very Large Array, and the Green Bank Telescope. While the large-scale features of the NH 3 (1,1) integrated intensity appear similar to 850 μm continuum emission maps of the Cores, on 15'' (1800 AU) scales we find significant discrepancies between the dense gas tracers in Oph B, but good correspondence in Oph C and F. Using the clumpfind structure identifying algorithm, we identify 15 NH 3 clumps in Oph B, and three each in Oph C and F. Only five of the Oph B NH 3 clumps are coincident within 30'' (3600 AU) of a submillimeter clump. We find v LSR varies little across any of the cores, and additionally varies by only ∼1.5 km s −1 between them. The observed NH 3 line widths within the Oph B and F Cores are generally large and often mildly supersonic, while Oph C is characterized by narrow line widths which decrease to nearly thermal values. We find several regions of localized narrow line emission (Δ v ≲ 0.4 km s −1 ), some of which are associated with NH 3 clumps. We derive the kinetic temperatures of the gas, and find they are remarkably constant across Oph B and F, with a warmer mean value ( T K = 15 K) than typically found in isolated regions and consistent with previous results in clustered regions. Oph C, however, has a mean T K = 12 K, decreasing to a minimum T K = 9.4 K toward the submillimeter continuum peak, similar to previous studies of isolated starless clumps. There is no significant difference in temperature toward protostars embedded in the Cores. NH 3 column densities, N (NH 3 ), and abundances, X (NH 3 ), are similar to previous work in other nearby molecular clouds. We find evidence for a decrease in X (NH 3 ) with increasing N (H 2 ) in Oph B2 and C, suggesting the NH 3 emission may not be tracing well the densest core gas.

Fetched live from OpenAlex and de-inverted. Abstracts are not stored in this database: the inverted indexes are 8.6 GB of the frame’s 9.3 GB of text, and the host has 13 GB free.