First Detection of Water Vapor in a Pre-stellar Core

摘要: Water is a crucial molecule in molecular astrophysics as it controls much of the gas/grain chemistry, including formation and evolution more complex organic molecules ices. Pre-stellar cores provide original reservoir material from which future planetary systems are built, but few observational constraints exist on water its partitioning between gas ice densest cores. Thanks to high sensitivity Herschel Space Observatory, we report first detection vapor at spectral resolution toward dense cloud verge star formation, pre-stellar core L1544. The line shows an inverse P-Cygni profile, characteristic gravitational contraction. To reproduce observations, has be present cold central thousand AU L1544, where species heavier than helium expected freeze out onto dust grains, ortho:para H2 ratio around 1:1 or larger. observed amount within (about 1.5 × 10–6 M ☉) can maintained by far-UV photons locally produced impact galactic cosmic rays with molecules. Such FUV irradiate icy mantles, liberating center. Our data, combined radiative transfer chemical/dynamical models, shed light interplay solids interstellar clouds measurement abundance profile across parent solar-type potential system.