Linking fragmentation with the evolutionary stage: grain growth and astrochemistry in the Infrared Dark Cloud G14.225-0.506

Abstract

We present Submillimeter Array observations of the 1 mm dust continuum emission and a molecular line survey towards hub-S of the Infrared Dark Cloud G14.225-0.506. We aim to probe grain growth and chemical composition of the dense cores to determine their evolutionary stage. We detected 7 cores and estimated their dust emissivity index using the Rayleigh Jeans approximation and assuming optically thin emission, finding values from 0 to 1.5, lower than the typical value of the interstellar medium (∼1.6), indicating the presence of large grains (millimeter-sized). We underline the presence of deuterated species and interstellar complex organic molecules, mainly methanol, in some cores. All cores exhibit carbon monoxide and other simple molecules. The results suggest that cores MM1a, MM3a and MM5b are in an advanced evolutionary stage within the protostellar phase, whereas MM4, MM5a and MM7a may be less evolved young stellar objects