Circumstellar and interstellar material in the CO3 chondrite ALHA77307: An isotopic and elemental investigation

Bose, Maitrayee; Floss, C.; Stadermann, F. J.; Stroud, Rhonda M.; Speck, A. K.

doi:10.1016/j.gca.2012.06.027

Cited by 54 publications

(71 citation statements)

References 89 publications

(147 reference statements)

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“…They are mostly amorphous and often non-stoichiometric with sometimes internal nm-scale compositional variations (Nguyen et al 2016). Bose et al (2012) found in the CO3 chondrite ALHA 77307 many presolar grains having intermediate stoichiometry between olivine-like and pyroxenelike material (see their Fig.6), similar to the X40 sample. These presolar grains come from AGB circumstellar envelops, supernovae, novae: they are the interstellar grains that emit in the FIR/submm domain.…”

Section: Comparaison With Cosmic Dust Modelsmentioning

confidence: 78%

Low temperature MIR to submillimeter mass absorption coefficient of interstellar dust analogues

Demyk

Meny

Lü

et al. 2017

A&A

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Context. The submillimeter spectral domain has been extensively explored by the Herschel and Planck satellites and is now reachable from the ground with ALMA. A wealth of data, revealing cold dust thermal emission, is available for astronomical environments ranging from interstellar clouds, cold clumps, circumstellar envelops, and protoplanetary disks. The interpretation of these observations relies on the understanding and modeling of cold dust emission and on the knowledge of the dust optical properties. Aims. The aim of this work is to provide astronomers with a set of spectroscopic data of realistic interstellar dust analogues that can be used to interpret the observations. It pursues the experimental effort aimed at characterizing the spectroscopic properties of interstellar dust analogues at low temperature in the mid infrared (MIR) to millimeter spectral domain. Compared to previous studies, it extends the range of studied dust analogues in terms of composition and of structure of the material. Methods. Glassy silicates of mean composition (1-x)MgO -xSiO 2 with x = 0.35 (close to forsterite, Mg 2 SiO 4 ), 0.50 (close to enstatite, MgSiO 3 ) and 0.40 (close to Mg 1.5 SiO 3.5 or MgSiO 3 :Mg 2 SiO 4 = 50:50) were synthesized. The mass absorption coefficient (MAC) of the samples was measured in the spectral domain 30 -1000 µm for grain temperature in the range 300 K -10 K and at room temperature in the 5 -40 µm domain. Results. We find that the MAC of all samples varies with the grains temperature and that its spectral shape cannot be approximated by a single power law in λ −β . In the FIR/submm, and above 30K, the MAC value at a given wavelength increases with the temperature as thermally activated absorption processes appear. The studied materials exhibit different and complex behaviors at long wavelengths (λ ≥ 200 to 700 µm depending on the samples).These behaviors are attributed to the amorphous nature of dust and to the amount and nature of the defects within this amorphous structure. We do not observe MAC variations in the 10-30 K range. Above 20 µm, the measured MAC are much higher than the MAC calculated from interstellar silicate dust models indicating that the analogues measured in this study are more emissive than the silicates in cosmic dust models. Conclusions. The underestimated value of the MAC deduced from cosmic dust models in the FIR/submm has important astrophysical implications because masses are overestimated by the models. Moreover, constraints on elemental abundance of heavy elements in cosmic dust models are relaxed.

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Section: Comparaison With Cosmic Dust Modelsmentioning

confidence: 78%

Low temperature MIR to submillimeter mass absorption coefficient of interstellar dust analogues

Demyk

Meny

Lü

et al. 2017

A&A

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“…Iron could also be present in the amorphous silicate network either in the form of ferric iron (Fe 3+ ) and/or in the form of ferrous iron (Fe 2+ ). Interestingly, Bose et al (2012) and reference therein, showed that a number of presolar silicates are ferromagnesian. Such silicates thus constitute relevant analogues of interstellar silicates.…”

Section: Introductionmentioning

confidence: 96%

Low-temperature MIR to submillimeter mass absorption coefficient of interstellar dust analogues

Demyk

Meny

Leroux

et al. 2017

A&A

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Context. To model the cold dust emission observed in the diffuse interstellar medium, in dense molecular clouds or in cold clumps that could eventually form new stars, it is mandatory to know the physical and spectroscopic properties of this dust and to understand its emission. Aims. This work is a continuation of previous studies aiming at providing astronomers with spectroscopic data of realistic cosmic dust analogues for the interpretation of observations. The aim of the present work is to extend the range of studied analogues to iron-rich silicate dust analogues. Methods. Ferromagnesium amorphous silicate dust analogues were produced by a sol-gel method with a mean composition close to Mg 1−x Fe x SiO 3 with x = 0.1, 0.2, 0.3, 0.4. Part of each sample was annealed at 500• C for two hours in a reducing atmosphere to modify the oxidation state of iron. We have measured the mass absorption coefficient (MAC) of these eight ferromagnesium amorphous silicate dust analogues in the spectral domain 30−1000 µm for grain temperature in the range 10−300 K and at room temperature in the 5−40 µm range. Results. The MAC of ferromagnesium samples behaves in the same way as the MAC of pure Mg-rich amorphous silicate samples. In the 30−300 K range, the MAC increases with increasing grain temperature whereas in the range 10−30 K, we do not see any change of the MAC. The MAC cannot be described by a single power law in λ −β . The MAC of the samples does not show any clear trend with the iron content. However the annealing process has, on average, an effect on the MAC that we explain by the evolution of the structure of the samples induced by the processing. The MAC of all the samples is much higher than the MAC calculated by dust models. Conclusions. The complex behavior of the MAC of amorphous silicates with wavelength and temperature is observed whatever the exact silicate composition (Mg vs. Fe amount). It is a universal characteristic of amorphous materials, and therefore of amorphous cosmic silicates, that should be taken into account in astronomical modeling. The enhanced MAC of the measured samples compared to the MAC calculated for cosmic dust model implies that dust masses are overestimated by the models.

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“…The presolar grains traversed the ISM, eventually becoming a part of the forming solar system, where some were preserved in meteorites. Studies have found presolar silicate grains with stoichiometry intermediate between olivine and pyroxene (Bose 2011, Bose et al 2012, Vollmer et al 2009). Models using interstellar and protoplanetary dust should consider amorphous grains of intermediate stoichiometry between olivine and pyroxene, given the meteoritic evidence for non-stoichiometric amorphous silicates from presolar grains.…”

Section: Introductionmentioning

confidence: 99%

Silicate Composition of the Interstellar Medium

Fogerty

Forrest

Watson

et al. 2016

ApJ

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The composition of silicate dust in the diffuse interstellar medium and in protoplanetary disks around young stars informs our understanding of the processing and evolution of the dust grains leading up to planet formation. Analysis of the well-known 9.7µm feature indicates that small amorphous silicate grains represent a significant fraction of interstellar dust and are also major components of protoplanetary disks. However, this feature is typically modelled assuming amorphous silicate dust of olivine and pyroxene stoichiometries. Here, we analyze interstellar dust with models of silicate dust that include non-stoichiometric amorphous silicate grains. Modelling the optical depth along lines of sight toward the extinguished objects Cyg OB2 No. 12 and ζ Ophiuchi, we find evidence for interstellar amorphous silicate dust with stoichiometry intermediate between olivine and pyroxene, which we simply refer to as "polivene." Finally, we compare these results to models of silicate emission from the Trapezium and protoplanetary disks in Taurus.

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Circumstellar and interstellar material in the CO3 chondrite ALHA77307: An isotopic and elemental investigation

Cited by 54 publications

References 89 publications

Low temperature MIR to submillimeter mass absorption coefficient of interstellar dust analogues

Low temperature MIR to submillimeter mass absorption coefficient of interstellar dust analogues

Low-temperature MIR to submillimeter mass absorption coefficient of interstellar dust analogues

Silicate Composition of the Interstellar Medium

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