Interstellar Dust Grains

Draine, B. T.

doi:10.1146/annurev.astro.41.011802.094840

Cited by 2,214 publications

(2,322 citation statements)

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“…The above time-scales require that the flux of E > 5 eV dissociating photons is small compared to those producing fluorescence. This depends on the specific dust absorption properties, that sharply change with A V as dust populations evolve (Draine 2003), on the strength and width of the 2175 Å extinction bump, and on the role of molecular electronic transitions blanketing the FUV spectrum. The similar trans-HCOOH line intensities observed towards the three positions of the Bar (Fig.…”

Section: Photoisomerization Rates and Discussionmentioning

confidence: 99%

“…Grain populations are known to evolve in molecular clouds, especially in PDRs where the sharp attenuation of a strong FUV field results in a stratification of the dust and PAH properties with A V (Draine 2003). Therefore, although the varying optical properties of grains are difficult to quantify and include in PDR models, they likely play a role on how FUV photons of different energies are differentially absorbed as a function of A V (Goicoechea & Le Bourlot 2007).…”

Section: Appendix B: Estimation Of the Photoisomerization Rate In Thementioning

confidence: 99%

“…For the particular case of HCOOH, the strength and width of the 2175 Å extinction bump (Cardelli et al 1989) naturally divides the range of photons producing HCOOH photodissociation (those with E > 5 eV) from those producing fluorescence (E < 5 eV). The extinction bump has been related with the absorption of FUV photons by PAH mixtures and small carbonaceous grains (Joblin et al 1992;Draine 2003). Although it is not known how the bump evolves with A V , it clearly determines how the lower-energy FUV photons are absorbed.…”

Section: Appendix B: Estimation Of the Photoisomerization Rate In Thementioning

confidence: 99%

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Trans-cismolecular photoswitching in interstellar space

Cuadrado

Goicoechea

Roncero

et al. 2016

A&A

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As many organic molecules, formic acid (HCOOH) has two conformers (trans and cis). The energy barrier to internal conversion from trans to cis is much higher than the thermal energy available in molecular clouds. Thus, only the most stable conformer (trans) is expected to exist in detectable amounts. We report the first interstellar detection of cis-HCOOH. Its presence in ultraviolet (UV) irradiated gas exclusively (the Orion Bar photodissociation region), with a low trans-to-cis abundance ratio of 2.8 ± 1.0, supports a photoswitching mechanism: a given conformer absorbs a stellar photon that radiatively excites the molecule to electronic states above the interconversion barrier. Subsequent fluorescent decay leaves the molecule in a different conformer form. This mechanism, which we specifically study with ab initio quantum calculations, was not considered in Space before but likely induces structural changes of a variety of interstellar molecules submitted to UV radiation.

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Section: Photoisomerization Rates and Discussionmentioning

confidence: 99%

Section: Appendix B: Estimation Of the Photoisomerization Rate In Thementioning

confidence: 99%

Section: Appendix B: Estimation Of the Photoisomerization Rate In Thementioning

confidence: 99%

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Trans-cismolecular photoswitching in interstellar space

Cuadrado

Goicoechea

Roncero

et al. 2016

A&A

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“…There is extensive recycling of the grains within the interstellar medium (ISM) and in diverse stars; only a limited sampling is available. Much earlier generations of stellar debris are, of course, involved in making up the solar inventory; this includes gas (atoms, molecules, and ions) and stellar dust that has been cycled-recycled by a variety of processes in the ISM (see Draine [54] [55], [56]). The gas is depleted in "non-volatile" elements which are mostly resident in the dust phase.…”

Section: Circumstellar Dust Grainsmentioning

confidence: 99%

“…It is now known that dust grains from diverse AGB stars are a substantial or major source of the condensed matter that was incorporated into the early solar system. Reviews of astronomical observations on dust are given by Draine [54] [55] [56].…”

Section: Introductionmentioning

confidence: 99%

Short-lived nuclei in the early Solar System: Possible AGB sources

et al. 2006

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The abundances of short-lived radionuclides in the early solar system (ESS) are reviewed, as well as the methodology used in determining them. These results are compared with the inventory estimated for a uniform galactic production model. It is shown that, to within a factor of two, the observed abundances of 238 U, 235 U, 232 Th, 244 Pu, 182 Hf, 146 Sm, and 53 Mn are roughly compatible with long-term galactic nucleosynthesis. 129 I is an exception, with an ESS inventory much lower than expected from uniform production. The isotopes 107 Pd, 60 Fe, 41 Ca, 36 Cl, 26 Al, and 10 Be require late addition to the protosolar nebula. 10 Be is the product of energetic particle irradiation of the solar system as most probably is 36 Cl. Both of these nuclei appear to be present when 26 Al is absent. A late injection by a supernova (SN) cannot be responsible for most of the short-lived nuclei without excessively producing 53 Mn; it can however be the source of 53 Mn itself and possibly of 60 Fe. If a late SN injection is responsible for these two nuclei, then there remains the problem of the origin of 107 Pd and several other isotopes. Emphasis is given to an AGB star as a source of many of the nuclei, including 60 Fe; this possibility is explored with a new generation of stellar models. It is shown that if the dilution factor (i.e. the ratio of the contaminating mass to the solar parental cloud mass) is f 0 ∼ 4×10 −3 , a reasonable representation for many nuclei is obtained; this requires that ( 60 Fe/ 56 Fe) ESS ∼ 10 −7 to 2×10 −6 . The nuclei produced by an AGB source do not include 53 Mn, 10 Be or 36 Cl if it is very abundant. The role of irradiation is discussed with regard to 26 Al, 36 Cl and 41 Ca, and the estimates of bulk solar abundances of these isotopes are commented on. The conflict between various scenarios is emphasized as well as the current absence of an astrophysically plausible global interpretation for all the existing data. Examination of abundances for the actinides indicates that a quiescent interval of ∼ 10 8 years is required for actinide group production. This is needed in order to explain the data on 244 Pu and the new bounds on 247 Cm. Because this quiescent interval is not compatible with the 182 Hf data, a separate type of r-process event is needed for at least the actinides, distinct from the two types that have previously been identified. The apparent coincidence of the 129 I and trans-actinide time scales suggests that the last heavy r contribution was from an r-process that produced very heavy nuclei but without fission recycling so that the yields at Ba and below (including I) were governed by fission.

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Promises and Prospects

Grijs

2011

An Introduction to Distance Measurement in Astronomy

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Interstellar Dust Grains

Cited by 2,214 publications

References 251 publications

Trans-cismolecular photoswitching in interstellar space

Trans-cismolecular photoswitching in interstellar space

Short-lived nuclei in the early Solar System: Possible AGB sources

Promises and Prospects

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