Characterizing molecular clouds in the earliest phases of high-mass star formation

High-mass stars play a key role in the energetics and chemical evolution of molecular clouds and galaxies. However, the mechanisms that allow the formation of high-mass stars are far less clear than those of their low-mass counterparts. Most of the research on high-mass star formation has focused on regions currently undergoing star formation. In contrast, objects in the earlier prestellar stage have been more difficult to identify. Recently, it has been suggested that the cold, massive, and dense Infrared Dark Clouds (IRDCs) host the earliest stages of high-mass star formation. The chemistry of IRDCs remains poorly explored. In this dissertation, an observational program to search for chemical variations in IRDC clumps as a function of their age is described. An increase in N2H+ and HCO+ abundances is found from the quiescent, cold phase to the protostellar, warmer phases, reflecting chemical evolution. For HCO+ abundances, the observed trend is consistent with theoretical predictions. However, chemical models fail to explain the observed trend of increasing N2H+ abundances. Pristine high-mass prestellar clumps are ideal for testing and constraining theories of high-mass star formation because their predictions differ the most at the early stages of evolution. From the initial IRDC sample, a high-mass clump that is the best candidate to be in the prestellar phase was selected (IRDC G028.23-00.19 MM1). With a new set of observations, the prestellar nature of the clump is confirmed. High-angular resolution observations of IRDC G028.23-00.19 suggest that in order to form high-mass stars, the detected cores have to accrete a large amount of material, passing through a low- to intermediate-mass phase before having the necessary mass to form a high-mass star. The turbulent core accretion model is inconsistent with this observational result, but on the other hand, the observations support the competitive accretion model. Embedded cores have to grow in mass during the star-formation process itself; the mass is not set at early times as the turbulent core accretion model predicts. The observed gas velocity dispersion in the cores is transonic and mildly supersonic, resulting in low virial parameters (neglecting magnetic fields). The turbulent core accretion model assumes highly supersonic linewidths and virial parameters $sim$1, inconsistent with the observations, unless magnetic fields in the cores have strengths of the order of 1 mG

Experiencias del Programa ILE: prestación de servicios en el primer nivel de atención

Presentación en el Primer encuentro latinoamericano de prestadores públicos de abortos seguros y legales. CLACAI; CEDES, Buenos Aires, 11 y 12 de Agosto de 201

Difusión y Acceso a Datos e Información Científica y Tecnológica en la Normativa de Fondos Públicos para la Innovación en Chile

This paper analyzes the regulatory framework in the public funds of the National Innovation System in Chile regarding diffusion and access to scientific and technological data. The results show several failures in the innovation regulatory framework. Concerning data diffusion, most funds do not clearly define who should carry out the diffusion activities, do not promote sufficiently the diffusion of non-confidential information and show little interest in defining and planning diffusion activities. Regarding data sharing, it should be clearly specified the means in which R+D+i data and process are to be delivered. In addition, open access requirements to researchers present serious deficiencies, while compliance of commitments, although show better results, should further improve

Massive and low-mass protostars in massive "starless" cores

The infrared dark clouds (IRDCs) G11.11$-$0.12 and G28.34$+$0.06 are two of the best-studied IRDCs in our Galaxy. These two clouds host clumps at different stages of evolution, including a massive dense clump in both clouds that is dark even at 70 and 100$\mu$m. Such seemingly quiescent massive dense clumps have been speculated to harbor cores that are precursors of high-mass stars and clusters. We observed these two "prestellar" regions at 1mm with the Submillimeter Array (SMA) with the aim of characterizing the nature of such cores. We show that the clumps fragment into several low- to high-mass cores within the filamentary structure of the enveloping cloud. However, while the overall physical properties of the clump may indicate a starless phase, we find that both regions host multiple outflows. The most massive core though 70 $\mu$m dark in both clumps is clearly associated with compact outflows. Such low-luminosity, massive cores are potentially the earliest stage in the evolution of a massive protostar. We also identify several outflow features distributed in the large environment around the most massive core. We infer that these outflows are being powered by young, low-mass protostars whose core mass is below our detection limit. These findings suggest that low-mass protostars have already formed or are coevally formed at the earliest phase of high-mass star formation.Comment: in print at A&