Observaciones de moléculas deuteradas = Observations of deuterated molecules.

Abstract

The study of stars has been a relevant field for the scientific community for several decades, and these days is still an active field of study because of the important effect of stars into their galactic ecosystem. The contribution of stars to their surroundings consists mostly on the stellar feedback that is released during their lives, including the huge amount of energy released when these objects die. In the specific case of massive stars, they die in a violent supernovae explosion where a great amount of material and energy is released in a short period of time, instantly supplying the interstel lar gas with a wide variety of chemical species and producing perturbations even on distant objects. Understanding how these stars form and evolve is then fundamental to understand the lifecycle of the interstellar medium. Stars form by gravitational contraction of molecular cloud cores. The evolution of these cores and the subsequent formation of a star depends on the mass of these regions. There are different forma tion scenarios depending on the final mass of the stars, from stars with masses of a few solar masses to stars with more than 8 M , called massive stars. During the early phases of star formation, the volume density of molecular hydrogen, n(H2) > 104 cm−3 , and the temperature of the clouds are T < 20 K, reaching the ideal conditions to favour processes like freeze-out or depletion. Several C-, N- and O- bearing species are efficiently removed from the gas phase and frozen onto the surface of dust grains, especially CO. This segregation of CO enhances the enrichment of the deuterium atoms, compared to the hydrogen in the molecules, boosting the abundance of o-H2D+ and other deuterated species. The measurements of timescales in processes like star formation are crucial to distinguish between the competing star formation theories. Chemistry is a powerful tool to infer how long the star form ing gas remains cold and especially deuteration has been suggested to be a reliable chemical clock of star-forming regions due to its strong dependence on density and temperature changes during cloud contraction.