Properties of dust in the high-latitude translucent cloud L1780

Ridderstad, M.; Juvela, M.; Lehtinen, K.; Lemke, D.; Liljeström, T.

doi:10.1051/0004-6361:20053467

Cited by 42 publications

(50 citation statements)

References 31 publications

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“…The value of dust opacity is uncertain and is observed to vary from region to region (e.g. Kramer et al 2003;Stepnik et al 2003;Lehtinen et al 2004Lehtinen et al , 2007Ridderstad et al 2006;Martin et al 2012). In diffuse medium the expected value of κ is lower by a factor of two (Boulanger et al 1996).…”

Section: Column Density Maps and Massesmentioning

confidence: 99%

Galactic cold cores

Juvela

Ristorcelli

Pagani

et al. 2012

A&A

Self Cite

143

221

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Context. In the project galactic cold cores we are carrying out Herschel photometric observations of cold regions of the interstellar clouds as previously identified with the Planck satellite. The aim of the project is to derive the physical properties of the population of cold clumps and to study its connection to ongoing and future star formation. Aims. We examine the cloud structure around the Planck detections in 71 fields observed with the Herschel SPIRE instrument by the summer of 2011. We wish to determine the general physical characteristics of the fields and to examine the morphology of the clouds where the cold high column density clumps are found. Methods. Using the Herschel SPIRE data, we derive colour temperature and column density maps of the fields. Together with ancillary data, we examine the infrared spectral energy distributions of the main clumps. The clouds are categorised according to their large scale morphology. With the help of recently released WISE satellite data, we look for signs of enhanced mid-infrared scattering ("coreshine"), an indication of growth of the dust grains, and have a first look at the star formation activity associated with the cold clumps. Results. The mapped clouds have distances ranging from ∼100 pc to several kiloparsecs and cover a range of sizes and masses from cores of less than 10 M to clouds with masses in excess of 10 000 M . Most fields contain some filamentary structures and in about half of the cases a filament or a few filaments dominate the morphology. In one case out of ten, the clouds show a cometary shape or have sharp boundaries indicative of compression by an external force. The width of the filaments is typically ∼0.2-0.3 pc. However, there is significant variation from 0.1 pc to 1 pc and the estimates are sensitive to the methods used and the very definition of a filament. Enhanced mid-infrared scattering, coreshine, was detected in four clouds with six additional tentative detections. The cloud LDN 183 is included in our sample and remains the best example of this phenomenon. About half of the fields are associated with active star formation as indicated by the presence of mid-infrared point sources. The mid-infrared sources often coincide with structures whose sub-millimetre spectra are still dominated by the cold dust.

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Section: Column Density Maps and Massesmentioning

confidence: 99%

Galactic cold cores

Juvela

Ristorcelli

Pagani

et al. 2012

A&A

Self Cite

143

221

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“…The observed changes in the dust opacity at long wavelengths might be evidence for changes in the dust properties, suggesting that these changes occur due to the accretion of mantles (del Burgo et al 2003;Kiss et al 2006) and grain coagulation (Bernard et al 1999;del Burgo et al 2003;Stepnik et al 2003; Kiss et al 2006;Ridderstad et al 2006;Paradis et al 2009). Gas accretion forms grain mantles composed mainly of water ice and other molecular species (e.g.…”

Section: Introductionmentioning

confidence: 98%

“…Lagache et al 1998;Bernard et al 1999;Stepnik et al 2003;del Burgo et al 2003;Planck Collaboration 2011b). Additionally, an increase in the dust opacity by a factor between 2 and 4 is observed in these denser regions at long wavelengths, which is inferred from the low dust temperature, and not always by comparison to the gas or A V (Bernard et al 1999;Hotzel et al 2001;Cambrésy et al 2001;Stepnik et al 2003;Bianchi et al 2003;del Burgo et al 2003;del Burgo & Laureijs 2005;Kiss et al 2006;Lehtinen et al 2007;Ridderstad et al 2006;Bot et al 2009;Paradis et al 2009;Planck Collaboration 2011b). Moreover, the abundance of the very small grains (VSGs, 1−15 nm in radius), that are stochastically heated and responsible for the 60 μm emission, decreases by ∼80-100% in the transition from diffuse to dense molecular clouds (Laureijs et al 1991;Abergel et al 1994Abergel et al , 1996Lagache et al 1998;Stepnik et al 2003;Kramer et al 2003).…”

Section: Introductionmentioning

confidence: 99%

Dust coagulation processes as constrained by far-infrared observations

Koehler

Stepnik

Jones

et al. 2012

A&A

111

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Aims. We develop a simple model of coagulated dust particles of two sizes (3.5 and 60 nm radius) to understand the nature and the effects of coagulation, which could explain the evolution of the far-infrared (FIR) dust opacity observed in the transition between the diffuse and the dense interstellar medium (ISM) (n H > 10 3 cm −3 ). Methods. Using the discrete-dipole approximation (DDA) method, we have calculated the absorption coefficient, directly proportional to the opacity, of coagulated grains with varying numbers of sub-grains and of different grain composition. Results. We show that, in the transition from diffuse to dense clouds, an increase in the FIR opacity by a factor of about 2.7 is possible and a decrease in the grain temperature by up to 3−4 K can be explained by the presence of coagulated aggregates composed of four big grains and 4000 very small grains (40% of the volume of the BGs). The coagulation of very small grains into the aggregates leads to a decrease in the 60 μm emission. Conclusions. This model can explain the observed increase in opacity at long wavelengths, the decrease in temperature from the diffuse ISM to denser regions with the coagulation of grains into aggregates and the absence of the 60 μm emission with the coagulation of very small grains onto the surface of the big grains.

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“…An increase of the dust emissivity by a factor of 3 compared to the standard diffuse value was needed to reproduce the cold temperatures observed in the Taurus filament L1506 (Stepnik et al 2003). In dense regions, several studies have shown an opacity increase by a factor between 2 to 4 (Cambrésy et al 2001;Kramer et al 2003;Bianchi et al 2003;del Burgo et al 2003;Kiss et al 2006;Ridderstad et al 2006;Lehtinen et al 2007). More recently, similar results have been obtained with Herschel and Planck in molecular clouds and cold cores Planck Collaboration XXV 2011;Martin et al 2012;Roy et al 2013).…”

Section: Introductionmentioning

confidence: 99%

Galactic cold cores

Juvela

Ristorcelli

Marshall

et al. 2015

A&A

Self Cite

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Context. The project Galactic Cold Cores has carried out Herschel photometric observations of interstellar clouds where the Planck satellite survey has located cold and compact clumps. The sources represent different stages of cloud evolution from starless clumps to protostellar cores and are located in different Galactic environments. Aims. We examine this sample of 116 Herschel fields to estimate the submillimetre dust opacity and to search for variations that might be attributed to the evolutionary stage of the sources or to environmental factors, including the location within the Galaxy. Methods. The submillimetre dust opacity was derived from Herschel data, and near-infrared observations of the reddening of background stars are converted into near-infrared optical depth. We investigated the systematic errors affecting these parameters and used modelling to correct for the expected biases. The ratio of 250 μm and J band opacities is correlated with the Galactic location and the star formation activity. We searched for local variations in the ratio τ(250 μm)/τ(J) using the correlation plots and opacity ratio maps. Results. We find a median ratio of τ(250 μm)/τ(J) = (1.6 ± 0.2) × 10 −3 , which is more than three times the mean value reported for the diffuse medium. Assuming an opacity spectral index β = 1.8 instead of β = 2.0, the value would be lower by ∼30%. No significant systematic variation is detected with Galactocentric distance or with Galactic height. Examination of the τ(250 μm)/τ(J) maps reveals six fields with clear indications of a local increase of submillimetre opacity of up to τ(250 μm)/τ(J) ∼ 4 × 10 −3 towards the densest clumps. These are all nearby fields with spatially resolved clumps of high column density. Conclusions. We interpret the increase in the far-infrared opacity as a sign of grain growth in the densest and coldest regions of interstellar clouds.

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Properties of dust in the high-latitude translucent cloud L1780

Cited by 42 publications

References 31 publications

Galactic cold cores

Galactic cold cores

Dust coagulation processes as constrained by far-infrared observations

Galactic cold cores

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