Probing the physical and chemical structure of the CS core in LDN 673: multitransitional and continuum observations

Abstract

High angular resolution observations of dense molecular cores show that these cores can be clumpier at smaller scales and that some of these clumps can also be unbound or transient. The use of chemical models of the evolution of the molecular gas provides a way to probe the physical properties of the clouds. We study the properties of the clump and interclump medium in the starless CS core in LDN 673 by carrying out a molecular line survey with the IRAM 30‐m telescope towards two clumps and two interclump positions. We also observed the 1.2‐mm continuum with the MAMBO‐II bolometer at IRAM. The dust continuum map shows four condensations, three of them centrally peaked, coinciding with previously identified submillimetre sources. We confirm that the denser clump of the region, n ∼ 3.6 × 105 cm−3, is also the more chemically evolved, and it could still undergo further fragmentation. The interclump medium positions are denser than previously expected, likely n ∼ 1 × 103–1 × 104 cm−3 due to contamination, and are chemically young, similar to the gas in the lower density clump position. We argue that the density contrast between these positions and their general young chemical age would support the existence of transient clumps in the lower density material of the core. We were also able to find reasonable fits of the observationally derived chemical abundances to models of the chemistry of transient clumps.

Earliest Stages of Protocluster Formation: Substructure and Kinematics of Starless Cores in Orion

“…Although in general the morphology and sizes of our gas derived cores are consistent with the 850 µm dust continuum emission derived cores (Nutter & Ward-Thompson 2007), there are some clear discrepancies (e.g. Cores 5 and 7) that could suggest that the dust and gas traced by CS(2-1) are not well correlated in the early stage of star formation, which is also seen in other studies (Morata et al 2012).…”

Cs Emission Near Mir-Bubbles

“…It has been detected in outflows from protostars, infall, disks and in hot cores (Dutrey et al 1997;Bronfman et al 1996;Morata et al 2012). The chemistry is, naturally, complex, and it appears that CS can play several roles (Beuther et al 2002), such as tracing outflows (Wolf-Chase et al 1998) or hot cores (Chandler & Wood 1997).…”