2008ApJS..174..396R

Recent extinction studies of the Pipe Nebula (d=130 pc) reveal many cores spanning a range in mass from 0.2 to 20.4 M_☉. These dense cores were identified via their high extinction and comprise a starless population in a very early stage of development. Here we present a survey of NH₃(1,1), NH₃(2,2), CCS (2₁-1₀), and HC₅ N (9,8) emission toward 46 of these cores. An atlas of the 2MASS extinction maps is also presented. In total, we detect 63% of the cores in NH₃(1,1), 22% in NH₃(2,2), 28% in CCS, and 9% in HC₅ N emission. We find the cores are associated with dense gas (∼10⁴/cm3) with 9.5 K≤T_K≤17 K. Compared to C¹⁸O, we find the NH₃ line widths are systematically narrower, implying that the NH₃is tracing the dense component of the gas and that these cores are relatively quiescent. We find no correlation between core line width and size. The derived properties of the Pipe cores are similar to cores within other low-mass star-forming regions: the only differences are that the Pipe cores have weaker NH₃ emission and most show no current star formation as evidenced by the lack of embedded infrared sources. Such weak NH₃ emission could arise due to low column densities and abundances or reduced excitation due to relatively low core volume densities. Either alternative implies that the cores are relatively young. Thus, the Pipe cores represent an excellent sample of dense cores in which to study the initial conditions for star formation and the earliest stages of core formation and evolution.