Observational Constraints on Submillimeter Dust Opacity

Shirley, Yancy L.; Huard, Tracy L.; Pontoppidan, K. M.; Wilner, David J.; Stutz, Amelia M.; Bieging, John H.; Evans, Neal J.

doi:10.1088/0004-637x/728/2/143

Cited by 77 publications

(88 citation statements)

References 72 publications

(110 reference statements)

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“…We do not expect this trend to emerge, however, when the increase in β is driven by a low temperature. In this light, it is interesting that our findings regarding the opacity ratio between 850 and 2.2 μm for the (ic-sil, ic-gra) model after 3 × 10 6 yr are consistent with Shirley et al (2011) for the B335 class 0 source.…”

Section: Opacities At Sub-mm Wavelengthssupporting

confidence: 77%

“…Recently, too, near-IR scattered light has been detected from dense cloud cores and this is indicative of grain growth to micron-sizes Steinacker et al 2010). Finally, grain growth in dense clouds is also supported by an analysis of the sub-millimeter emission (Bianchi et al 2003;Kramer et al 2003;Shirley et al 2011).…”

Section: Introductionmentioning

confidence: 85%

“…The n g = 10 5 data in Table 2 has been retrieved from the online data. of individual cores (e.g., Schnee et al 2010;Shirley et al 2005Shirley et al , 2011 indicate that β is likely to be larger than 2. A favored explanation for the high β-values in these cold clumps is that the opacity becomes temperature dependent.…”

Section: Opacities At Sub-mm Wavelengthsmentioning

confidence: 99%

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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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Section: Opacities At Sub-mm Wavelengthssupporting

confidence: 77%

Section: Introductionmentioning

confidence: 85%

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Dust coagulation and fragmentation in molecular clouds

Ormel

Min

Tielens

et al. 2011

A&A

156

180

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“…Differences in the values of γ, such as those observed here, are probably to be related to differences in the dust composition. Differences in the opacity ratios are indeed common for many similar studies carried out in the past: for example, Kramer et al (2003) found that the opacity ratios determined toward four cores of the IC 5146 span the range (1.9 ± 0.2) × 10 −4 to (5.4 ± 0.3) × 10 −4 , which in terms of γ would correspond to the range 2000-5700 (see also Shirley et al 2011). Using the data in Table 1 of Mathis (1990), we can estimate the expected value of γ.…”

Section: Extinction Conversionmentioning

confidence: 82%

Herschel-Planckdust optical-depth and column-density maps

Lombardi

Bouy

Alves

et al. 2014

A&A

203

353

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We present high-resolution, high dynamic range column-density and color-temperature maps of the Orion complex using a combination of Planck dust-emission maps, Herschel dust-emission maps, and 2MASS NIR dust-extinction maps. The column-density maps combine the robustness of the 2MASS NIR extinction maps with the resolution and coverage of the Herschel and Planck dustemission maps and constitute the highest dynamic range column-density maps ever constructed for the entire Orion complex, covering 0.01 mag < A K < 30 mag, or 2 × 10 20 cm −2 < N < 5 × 10 23 cm −2 . We determined the ratio of the 2.2 µm extinction coefficient to the 850 µm opacity and found that the values obtained for both Orion A and B are significantly lower than the predictions of standard dust models, but agree with newer models that incorporate icy silicate-graphite conglomerates for the grain population. We show that the cloud projected probability distribution function, over a large range of column densities, can be well fitted by a simple power law. Moreover, we considered the local Schmidt-law for star formation, and confirm earlier results, showing that the protostar surface density Σ * follows a simple law Σ * ∝ Σ β gas , with β ∼ 2.

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“…There are a number of problems with this approach, however. One complication is the notoriously uncertain value of the dust emissivity at long wavelengths (Bianchi et al 2003;Kramer et al 2003;Alton et al 2004;Shirley et al 2011) and the mysterious anti-correlation between the dust emissivity index and dust temperature (Dupac et al 2003;Shetty et al 2009;Veneziani et al 2010;Juvela & Ysard 2012b,a;Kelly et al 2012;Smith et al 2012a). A second problem is the difficulty to observe in the FIR/submm window, which necessarily needs to be done from space using cryogenically cooled instruments.…”

Section: Introductionmentioning

confidence: 99%

FitSKIRT: genetic algorithms to automatically fit dusty galaxies with a Monte Carlo radiative transfer code

Geyter

Baes

Fritz

et al. 2013

A&A

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We present FitSKIRT, a method to efficiently fit radiative transfer models to UV/optical images of dusty galaxies. These images have the advantage that they have better spatial resolution compared to FIR/submm data. FitSKIRT uses the GAlib genetic algorithm library to optimize the output of the SKIRT Monte Carlo radiative transfer code. Genetic algorithms prove to be a valuable tool in handling the multi-dimensional search space as well as the noise induced by the random nature of the Monte Carlo radiative transfer code. FitSKIRT is tested on artificial images of a simulated edge-on spiral galaxy, where we gradually increase the number of fitted parameters. We find that we can recover all model parameters, even if all 11 model parameters are left unconstrained. Finally, we apply the FitSKIRT code to a V-band image of the edge-on spiral galaxy NGC 4013. This galaxy has been modeled previously by other authors using different combinations of radiative transfer codes and optimization methods. Given the different models and techniques and the complexity and degeneracies in the parameter space, we find reasonable agreement between the different models. We conclude that the FitSKIRT method allows comparison between different models and geometries in a quantitative manner and minimizes the need of human intervention and biasing. The high level of automation makes it an ideal tool to use on larger sets of observed data.

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Observational Constraints on Submillimeter Dust Opacity

Cited by 77 publications

References 72 publications

Dust coagulation and fragmentation in molecular clouds

Dust coagulation and fragmentation in molecular clouds

Herschel-Planckdust optical-depth and column-density maps

FitSKIRT: genetic algorithms to automatically fit dusty galaxies with a Monte Carlo radiative transfer code

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