Temperature Dependence of the Submillimeter Absorption Coefficient of Amorphous Silicate Grains

Boudet, Nathalie; Mutschke, H.; Nayral, Céline; Jäger, Cornelia; Bernard, J.-P.; Henning, Th.; Meny, C.

doi:10.1086/432966

Cited by 123 publications

(163 citation statements)

References 27 publications

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“…At low temperatures (T < 30 K), the dust optical properties appear to change significantly in terms of absolute value of the emissivity and the spectral index β. As also seen in laboratory measurements (e.g., Agladze et al 1996;Mennella et al 1998;Boudet et al 2005), the physical processes responsible for these effects probably involve ice mantle formation, grain coagulation, and low-energy structural transformations (e.g., Meny et al 2007). …”

Section: Interstellar Dustmentioning

confidence: 73%

Evolution of interstellar dust withHerschel. First results in the photodissociation regions of NGC 7023

Abergel¹,

Arab²,

Compiègne

et al. 2010

A&A

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Context. In photodissociation regions (PDRs), the physical conditions and the excitation evolve on short spatial scales as a function of depth within the cloud, providing a unique opportunity to study how the dust and gas populations evolve with the excitation and physical conditions. The mapping of the PDRs in NGC 7023 performed during the science demonstration phase of Herschel is part of the "Evolution of interstellar dust" key program. The goal of this project is to build a coherent database on interstellar dust emission from diffuse clouds to the sites of star formation. Aims. We study the far-infrared/submillimeter emission of the PDRs and their fainter surrounding regions. We combine the Herschel and Spitzer maps to derive at each position the full emission spectrum of all dust components, which we compare to dust and radiative transfer models in order to learn about the spatial variations in both the excitation conditions and the dust properties. Methods. We adjust the emission spectra derived from PACS and SPIRE maps using modified black bodies to derive the temperature and the emissivity index β of the dust in thermal equilibrium with the radiation field. We present a first modeling of the NGC 7023-E PDR with standard dust properties and abundances. Results. At the peak positions, a value of β equal to 2 is compatible with the data. The detected spectra and the spatial structures are strongly influenced by radiative transfer effects. We are able to reproduce the spectra at the peak positions deduced from Herschel maps and emitted by dust particles at thermal equilibrium, and also the evolution of the spatial structures observed from the near infrared to the submillimeter. On the other hand, the emission of the stochastically heated smaller particles is overestimated by a factor ∼2.

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Section: Interstellar Dustmentioning

confidence: 73%

Evolution of interstellar dust withHerschel. First results in the photodissociation regions of NGC 7023

Abergel¹,

Arab²,

Compiègne

et al. 2010

A&A

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show abstract

“…A favored explanation for the high β-values in these cold clumps is that the opacity becomes temperature dependent. Several laboratory studies show that low temperatures suppress the emissivity at longer wavelengths (Mennella et al 1998;Boudet et al 2005;Demyk et al, in prep). The observed correlation between β and decreasing T (e.g., Désert et al 2008) gives credibility to this scenario.…”

Section: Opacities At Sub-mm Wavelengthsmentioning

confidence: 99%

Dust coagulation and fragmentation in molecular clouds

Ormel

Min

Tielens

et al. 2011

A&A

156

180

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The dust size distribution in molecular clouds can be strongly affected by ice-mantle formation and (subsequent) grain coagulation. Following previous work where the dust size distribution has been calculated from a state-of-the art collision model for dust aggregates that involves both coagulation and fragmentation (Paper I), the corresponding opacities are presented in this study. The opacities are calculated by applying the effective medium theory assuming that the dust aggregates are a mix of 0.1 μm silicate and graphite grains and vacuum. In particular, we explore how the coagulation affects the near-IR opacities and the opacity in the 9.7 μm silicate feature. We find that as dust aggregates grow to μm-sizes both the near-IR color excess and the opacity in the 9.7 μm feature increases. Despite their coagulation, porous aggregates help to prolong the presence of the 9.7 μm feature. We find that the ratio between the opacity in the silicate feature and the near-IR color excess becomes lower with respect to the ISM, in accordance with many observations of dark clouds. However, this trend is primarily a result of ice mantle formation and the mixed material composition of the aggregates, rather than being driven by coagulation. With stronger growth, when most of the dust mass resides in particles of size ∼10 μm or larger, both the near-IR color excess and the 9.7 μm silicate feature significantly diminish. Observations at additional wavelengths, in particular in the sub-mm range, are essential to provide quantitative constraints on the dust size distribution within dense cores. Our results indicate that the sub-mm index β will increase appreciably, if aggregates grow to ∼100 μm in size.

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“…Laboratory measurements of the opacity and the spectral index at millimeter wavelengths found a dependence of the mass absorption with temperature for different grain compositions (Agladze et al 1996;Mennella et al 1998;Boudet et al 2005;Coupeaud et al 2011;Demyk et al 2013). Agladze et al (1996) found two different behaviors depending on the temperature range: for very low temperatures (1.2 -20 K) the millimeter opacity decreases with increasing temperature, while for temperatures between 20 and 30 K, it increases or is constant with temperature.…”

Section: Introductionmentioning

confidence: 99%

Search for grain growth toward the center of L1544

Chacón-Tanarro

Caselli

Bizzocchi

et al. 2017

A&A

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In dense and cold molecular clouds dust grains are surrounded by thick icy mantles. It is however not clear if dust growth and coagulation take place before the switch-on of a protostar. This is an important issue, as the presence of large grains may affect the chemical structure of dense cloud cores, including the dynamically important ionization fraction, and the future evolution of solids in protoplanetary disks. To study this further, we focus on L1544, one of the most centrally concentrated pre-stellar cores on the verge of star formation, and with a well-known physical structure. We observed L1544 at 1.2 and 2 mm using NIKA, a new receiver at the IRAM 30 m telescope, and we used data from the Herschel Space Observatory archive. We find no evidence of grain growth towards the center of L1544 at the available angular resolution. Therefore, we conclude that single dish observations do not allow us to investigate grain growth toward the pre-stellar core L1544 and high sensitivity interferometer observations are needed. We predict that dust grains can grow to 200 µm in size toward the central ∼300 au of L1544. This will imply a dust opacity change by a factor of ∼2.5 at 1.2 mm, which can be detected using the Atacama Large Millimeter and submillimeter Array (ALMA) at different wavelengths and with an angular resolution of 2 .

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Temperature Dependence of the Submillimeter Absorption Coefficient of Amorphous Silicate Grains

Cited by 123 publications

References 27 publications

Evolution of interstellar dust withHerschel. First results in the photodissociation regions of NGC 7023

Evolution of interstellar dust withHerschel. First results in the photodissociation regions of NGC 7023

Dust coagulation and fragmentation in molecular clouds

Search for grain growth toward the center of L1544

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