Characterization of the PDR in LDN1622

Abstract

The objective of this thesis is to physically characterize the Lynds Dark Nebula(LDN)1622. LDN1622 has been studied in infrared (IR) and ultraviolet (UV), and regions of low mass star formation have been contracted. In the microwave range, LDN1622 has also been observed and the results of these observations do not conform to galactic emission models in the vicinity of the Sun. For this reason, this work will plot the morphology of this cloud, to determine where you find the warm and dense nuclei and the transition zones. As future work, we want to compare these results with detailed observations in the microwave range. To analyze the morphology of the cloud we analyzed molecular emission lines, these were 12CO(2-1), 13CO(2-1), C18O(2-1) taken with the APEX telescope, 12CO(3-2) taken by the telescope ASTE, and 12CO(4-3) and CI[P1 􀀀 P0], both taken by the APEX telescope. With the cubes of data obtained by these emission lines, temperature and velocity maps of LDN1622 were made, with which it was possible to trace the densest nuclei, and the zones of transitions called PDR (photodissociation regions), and to make a molecular density map. To determine the PDR, we analyzed the Meudon PDR code, which is usually used to analyze the chemistry and physics of different interstellar clouds. From this model, neutral carbon information was extracted and used as PDR tracer, which made possible to establish a relationship between neutral carbon and visual extinction. Once we could establish the visual extinction where we expect to find PDR, we compared our results with a LDN1622 visual extinction map produced by NICER and with the column density map. It was found that the density of LDN1622 should be less than 105[cm􀀀3]. PDR was estimated precisely in the contours of the density map of LDN1622, this agrees with the idea that the UV radiation of nearby stars does not manage to penetrate the cloud, and this transition zone is established, between a molecular region and an atomic region. As in the neighborhoods, similar morphologies were found for CI and CO(4-3), which suggests that although the PDR is a transition zone, the cloud is sufficiently porous to allow part of the UV radiation to penetrate the cloud and dissociate molecules.