FIRST DETECTION OF WATER VAPOR IN A PRE-STELLAR CORE
- School of Physics and Astronomy, University of Leeds, Leeds LS2 9JT (United Kingdom)
- Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States)
- Department of Astronomy, The University of Michigan, 500 Church Street, Ann Arbor, MI 48109-1042 (United States)
- Observatorio Astronomico Nacional (IGN), Calle Alfonso XII, 3, E-28014 Madrid (Spain)
- Department of Earth and Planetary Sciences, Kobe University, Nada, 657-8501 Kobe (Japan)
- LERMA and UMR 8112 du CNRS, Observatoire de Paris, 61 Av. de l'Observatoire, F-75014 Paris (France)
- Leiden Observatory, Leiden University, P.O. Box 9513, 2300 RA Leiden (Netherlands)
- INAF-Osservatorio Astrofisico di Arcetri, Largo E. Fermi 5, I-50125 Firenze (Italy)
- INAF-Osservatorio Astronomico di Roma, I-00040 Monte Porzio Catone (Italy)
Water is a crucial molecule in molecular astrophysics as it controls much of the gas/grain chemistry, including the formation and evolution of more complex organic molecules in ices. Pre-stellar cores provide the original reservoir of material from which future planetary systems are built, but few observational constraints exist on the formation of water and its partitioning between gas and ice in the densest cores. Thanks to the high sensitivity of the Herschel Space Observatory, we report on the first detection of water vapor at high spectral resolution toward a dense cloud on the verge of star formation, the pre-stellar core L1544. The line shows an inverse P-Cygni profile, characteristic of gravitational contraction. To reproduce the observations, water vapor has to be present in the cold and dense central few thousand AU of L1544, where species heavier than helium are expected to freeze out onto dust grains, and the ortho:para H{sub 2} ratio has to be around 1:1 or larger. The observed amount of water vapor within the core (about 1.5 Multiplication-Sign 10{sup -6} M{sub Sun }) can be maintained by far-UV photons locally produced by the impact of galactic cosmic rays with H{sub 2} molecules. Such FUV photons irradiate the icy mantles, liberating water vapor in the core center. Our Herschel data, combined with radiative transfer and chemical/dynamical models, shed light on the interplay between gas and solids in dense interstellar clouds and provide the first measurement of the water vapor abundance profile across the parent cloud of a future solar-type star and its potential planetary system.
- OSTI ID:
- 22078437
- Journal Information:
- Astrophysical Journal Letters, Vol. 759, Issue 2; Other Information: Country of input: International Atomic Energy Agency (IAEA); ISSN 2041-8205
- Country of Publication:
- United States
- Language:
- English
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