CS Depletion in Prestellar Cores

Abstract

The CS molecule is known to be adsorbed onto dust in cold and dense conditions, causing it to be significantly depleted in the central region of cores. This study is aimed to investigate the depletion of the CS molecule using the optically thin C34S molecular line observations. We mapped five prestellar cores, L1544, L1552, L1689B, L694-2, and L1197, using two molecular lines, C34S (J = 2 − 1) and N2H+ (J = 1 − 0) with the NRO 45 m telescope, doubling the number of cores where the CS depletion was probed using C34S. In most of our targets, the distribution of C34S emission shows features that suggest that the CS molecule is generally depleted in the center of the prestellar cores. The radial profile of the CS abundance with respect to H2 directly measured from the CS emission and the Herschel dust emission indicates that the CS molecule is depleted by a factor of ∼3 toward the central regions of the cores with respect to their outer regions. The degree of the depletion is found to be even more enhanced, by an order of magnitude, when the contaminating effect introduced by the presence of CS molecules in the surrounding envelope that lie along the line of sight is removed. Except for L1197—which is classified as relatively the least evolved core in our targets, based on its observed physical parameters—we found that the remaining four prestellar cores are suffering from significant CS depletion at their central region, regardless of the relative difference in their evolutionary status.