The Complex Organic Molecular Content in the L1498 Starless Core
Jiménez-Serra, I, Vasyunin, AI, Spezzano, S, Caselli, P, Cosentino, G, Viti, S
Abstract
Observations carried out toward starless and prestellar cores have revealed that complex organic molecules are \nprevalent in these objects, but it is unclear what chemical processes are involved in their formation. Recently, it \nhas been shown that complex organics are preferentially produced at an intermediate-density shell within the \nL1544 prestellar core at radial distances of ∼4000 au with respect to the core center. However, the spatial \ndistribution of complex organics has only been inferred toward this core, and it remains unknown whether \nthese species present a similar behavior in other cores. We report high-sensitivity observations carried out \ntoward two positions in the L1498 starless core, the dust peak and a position located at a distance of ∼11,000 au \nfrom the center of the core where the emission of CH3OH peaks. Similarly to L1544, our observations reveal \nthat small O-bearing molecules and N-bearing species are enhanced by factors of ∼4–14 toward the outer shell \nof L1498. However, unlike L1544, large O-bearing organics such as CH3CHO, CH3OCH3, or CH3OCHO \nare not detected within our sensitivity limits. For N-bearing organics, these species are more abundant toward \nthe outer shell of the L1498 starless core than toward the one in L1544. We propose that the differences \nobserved between O-bearing and N-bearing species in L1498 and L1544 are due to the different physical \nstructure of these cores, which in turn is a consequence of their evolutionary stage, with L1498 being younger \nthan L1544.