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5 results on '"ISM : evolution"'

1. Turbulence in the Diffuse Interstellar Medium.

Author

Falgarone, Edith, Godard, Benjamin, and Hily-Blant, Pierre

Abstract

The diffuse interstellar medium (ISM) hosts the first steps of interstellar chemistry and the seeds of dense structures. Since its turbulent pressure by far exceeds its thermal pressure, turbulence must play a prominent role in its evolution. Fed at galactic scales, turbulent energy cascades down to the dissipation scales, but as in both laboratory and atmospheric turbulence, it does so in an intermittent way : only a tiny fraction of the small-scales is fed by the turbulent cascade, so that dissipation occurs in bursts. In diffuse molecular clouds, where they can be observed, the signatures of intermittency are: (1) the non-Gaussian statistics of velocity increments, and (2) the existence of coherent structures of intense velocity-shear that appear to channel the large-scale turbulent energy down to milliparsec scales. Attempts at modelling the warm chemistry triggered in the diffuse ISM by bursts of turbulent dissipation are promising : in this framework, the so far unexplained molecular richness observed in this medium is naturally understood, in particular its CH+, HCO+ and CO abundances. Turbulent dissipation is also likely at the origin of the H2 rotational line emission of the diffuse ISM and of a significant fraction of its [C II] emission. [ABSTRACT FROM PUBLISHER]

Published
2011
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2. Laboratory studies of thermally processed H2O-CH3OH-CO2 ice mixtures and their astrophysical implications

Subjects
DESORPTION, ANALOGS, extinction, GRAIN MANTLES, ISM : abundances, INFRARED SPECTRAL PROPERTIES, NITROGEN, ISM : molecules, infrared : ISM : lines and bands, ISM : dust, MOLECULAR CLOUDS, ISM : evolution, CO2, METHANOL, methods : laboratory, CARBONYL SULFIDE OCS, DIOXIDE
Abstract

Data of the Infrared Space Observatory ISO have strongly influenced the current view of interstellar ice chemistry. ISO and ground-based results have confirmed that the most abundant ice species in warm regions close to massive protostars are H2O, CO2, and CH3OH. Ice segregation in those environments reflects the extensive thermal processing of grains over the Lifetime of protostars. We present here a systematic set of laboratory infrared spectra of ice mixtures dominated by H2O, CO2 and CH3OH which have been exposed to thermal and UV irradiation processing. It is shown that the infrared bands of CO2 and of CH3OH are particularly sensitive to the ice composition, temperature and applied UV irradiation. The laboratory data suggest partial crystallization of interstellar ices in the protostellar environment. We present a detailed laboratory study of the CO2 bending mode at 15.2 mu m. The observed multipeak structure of the CO2 bending mode is a result of thermal processing and can not be produced by UV irradiation in the laboratory. Laboratory results show that annealed CO2 ice has a lower stability against UV irradiation than cold amorphous CO2 ice. Annealed ice mixtures containing H2O, CO2 and CH3OH show that the multipeak structure of the CO2 bending mode is not destroyed by UV fluxes of less than or similar to 10(18) photons.cm(-2). Detailed analysis of H2O, CO2 and CH3OH bands show that their profiles can be effectively used to trace the Line of sight conditions and the origin and evolution of the ice composition in dense clouds. The datafiles discussed in this paper can be retrieved from the Leiden observatory database (www.strw.leidenuniv.nl/similar to lab/isodb).

Published
1999

3. Intergalactic medium heating by dark matter

Author

E. Ripamonti, Michela Mapelli, Andrea Ferrara, Ripamonti, E., Mapelli, M., Ferrara, Andrea, and Kapteyn Astronomical Institute

Subjects
Sterile neutrino, STERILE NEUTRINOS, Dark matter, UNIVERSE, FOS: Physical sciences, LINE, Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, PHOTONS, ISM: evolution, Ionization, Thermal, Neutrinos, Light dark matter, Physics, Astrophysics (astro-ph), REIONIZATION, Mass–energy equivalence, CONSTRAINTS, Astronomy and Astrophysics, Redshift, Space and Planetary Science, Intergalactic medium, X-RAY, High Energy Physics::Experiment, ISM : evolution, EMISSION, DECAY
Abstract

We derive the evolution of the energy deposition in the intergalactic medium (IGM) by dark matter (DM) decays/annihilations for both sterile neutrinos and light dark matter (LDM) particles. At z > 200 sterile neutrinos transfer a fraction f_abs~0.5 of their rest mass energy into the IGM; at lower redshifts this fraction becomes 300) redshift, dropping to ~0.1 below z=100. These results indicate that the impact of DM decays/annihilations on the IGM thermal and ionization history is less important than previously thought. We find that sterile neutrinos (LDM) decays are able to increase the IGM temperature by z=5 at most up to 4K (100K), about 50-200 times less than predicted by estimates based on the assumption of complete energy transfer to the gas., Comment: 13 pages, 7 figures; MNRAS, in press; matches the published version

Published
2007

4. Laboratory studies of thermally processed H2O-CH3OH-CO2 ice mixtures and their astrophysical implications

Author

Ehrenfreund, P, Kerkhof, O, Schutte, WA, Boogert, ACA, Gerakines, PA, Dartois, E, d'Hendecourt, L, Tielens, AGGM, van Dishoeck, EF, Whittet, DCB, and Kapteyn Astronomical Institute

Subjects
DESORPTION, ANALOGS, GRAIN MANTLES, ISM : abundances, INFRARED SPECTRAL PROPERTIES, NITROGEN, ISM : molecules, infrared : ISM : lines and bands, ISM : dust, extinction, MOLECULAR CLOUDS, ISM : evolution, CO2, METHANOL, Astrophysics::Earth and Planetary Astrophysics, methods : laboratory, CARBONYL SULFIDE OCS, Physics::Atmospheric and Oceanic Physics, Astrophysics::Galaxy Astrophysics, DIOXIDE
Abstract

Data of the Infrared Space Observatory ISO have strongly influenced the current view of interstellar ice chemistry. ISO and ground-based results have confirmed that the most abundant ice species in warm regions close to massive protostars are H2O, CO2, and CH3OH. Ice segregation in those environments reflects the extensive thermal processing of grains over the Lifetime of protostars. We present here a systematic set of laboratory infrared spectra of ice mixtures dominated by H2O, CO2 and CH3OH which have been exposed to thermal and UV irradiation processing. It is shown that the infrared bands of CO2 and of CH3OH are particularly sensitive to the ice composition, temperature and applied UV irradiation. The laboratory data suggest partial crystallization of interstellar ices in the protostellar environment. We present a detailed laboratory study of the CO2 bending mode at 15.2 mu m. The observed multipeak structure of the CO2 bending mode is a result of thermal processing and can not be produced by UV irradiation in the laboratory. Laboratory results show that annealed CO2 ice has a lower stability against UV irradiation than cold amorphous CO2 ice. Annealed ice mixtures containing H2O, CO2 and CH3OH show that the multipeak structure of the CO2 bending mode is not destroyed by UV fluxes of less than or similar to 10(18) photons.cm(-2). Detailed analysis of H2O, CO2 and CH3OH bands show that their profiles can be effectively used to trace the Line of sight conditions and the origin and evolution of the ice composition in dense clouds. The datafiles discussed in this paper can be retrieved from the Leiden observatory database (www.strw.leidenuniv.nl/similar to lab/isodb).

Published
1999

5. The origin of short-lived radionuclides and the astrophysical environment of solar system formation

Author

Gounelle, Matthieu and Meibom, Anders

Subjects
supernovae : general, Carina-Nebula, Protoplanetary Disks, stars : formation, Astrophysics::High Energy Astrophysical Phenomena, Star-Forming Region, Astrophysics::Cosmology and Extragalactic Astrophysics, Luminosity Function, ISM : clouds, Orion Nebula Cluster, solar system : formation, Molecular Clouds, planetary systems : protoplanetary disks, Planetesimal Formation, Circumstellar Disks, Astrophysics::Solar and Stellar Astrophysics, ISM : evolution, Massive Stars, Astrophysics::Earth and Planetary Astrophysics, Far-Ultraviolet Radiation, Astrophysics::Galaxy Astrophysics
Abstract

Based on early solar system abundances of short-lived radionuclides (SRs), such as Al-26 (T-1/2 = 0.74 Myr) and Fe-60 (T-1/2 1.5 Myr), it is often asserted that the Sun was born in a large stellar cluster, where a massive star contaminated the protoplanetary disk with freshly nucleosynthesized isotopes from its supernova (SN) explosion. To account for the inferred initial solar system abundances of short-lived radionuclides, this supernova had to be close (similar to 0.3 pc) to the young (similar to 1 Myr) protoplanetary disk. Here we show that massive star evolution timescales are too long, compared to typical timescales of star formation in embedded clusters, for them to explode as supernovae within the lifetimes of nearby disks. This is especially true in an Orion Nebular Cluster ( ONC) type of setting, where the most massive star will explode as a supernova similar to 5 Myr after the onset of star formation, when nearby disks will have already suffered substantial photoevaporation and/or formed large planetesimals. We quantify the probability for any protoplanetary disk to receive SRs from a nearby supernova at the level observed in the early solar system. Key constraints on our estimate are: ( 1) SRs have to be injected into a newly formed (

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