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1. Inferring the dust emission at submillimeter and millimeter wavelengths using neural networks.

Author

Paradis, D., Mény, C., Noriega-Crespo, A., Demyk, K., Ristorcelli, I., and Ysard, N.

Subjects
MACHINE learning, SUPERVISED learning, EMISSIVITY, MOLECULAR spectra, DUST
Abstract

Context. The Planck mission provided all-sky dust emission maps in the submillimeter (submm) to millimeter (mm) range at an angular resolution of 5′. In addition, some specific sources can be observed at long wavelengths and higher resolution using ground-based telescopes. These observations are limited to small scales and are sometimes not delivered to the community. These ground-based observations require extensive data processing before they become available for scientific analysis, and suffer from extended emission filtering. Aims. At present, we are still unable to fully understand the emissivity variations observed in different astrophysical environments at long (submm and mm) wavelengths. Several models have been developed to reproduce the diffuse Galactic medium, and each distinct environment requires an adjustment of the models. It is therefore challenging to estimate any dust emission in the submm-mm at a better resolution than the 5′ from Planck. In this analysis, based on supervised deep learning algorithms, we produced dust emission predictions in the two Planck bands centered at 850 µm (353 GHz) and 1.38 mm (217 GHz) at the Herschel resolution (37″). Prediction or forecasting is a frequently used term in machine learning or neural network research that refers to the output of an algorithm that has been trained on a given dataset and that is being used for modeling purposes. Methods. Herschel data of Galactic environments, ranging from 160 µm to 500 µm and smoothed to an angular resolution of 5′, were used to train the neural network. This training aimed to provide the most accurate model for reproducing Planck maps of dust emission at 850 µm and 1.38 mm. Then, using Herschel data only, the model was applied to predict dust emission maps at 37″. Results. The neural network is capable of reproducing dust emission maps of various Galactic environments with a difference of only a few percent at the Planck resolution. Remarkably, it also performs well for nearby extragalactic environments. This could indicate that large dust grains, probed by submm or mm observations, have similar properties in both our Galaxy and nearby galaxies, or at least that their spectral behaviors are comparable in Galactic and extragalactic environments. For the first time, we provide to the community dust emission prediction maps at 850 µm and 1.38 mm at the 37″ of several surveys: Hi-GAL, Gould Belt, Cold Cores, HERITAGE, Helga, HerM33es, KINGFISH, and Very Nearby Galaxies. The ratio of these two wavelength brightness bands reveals a derived emissivity spectral index statistically close to 1 for all the surveys, which favors the hypothesis of a flattened dust emission spectrum for wavelengths larger than 850 µm. Conclusions. Neural networks appear to be powerful algorithms that are highly efficient at learning from large datasets and achieving accurate reproductions with a deviation of only a few percent. However, to fully recover the input data during the training, it is essential to sample a sufficiently large range of datasets and physical conditions. [ABSTRACT FROM AUTHOR]

Published
2024
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2. Low temperature MIR to submillimeter mass absorption coefficient of interstellar dust analogues

Author

Demyk, K., Meny, C., Lu, X. -H., Papatheodorou, G., Toplis, M. J., Leroux, H., Depecker, C., Brubach, J. -B., Roy, P., Nayral, C., Ojo, W. -S., Delpech, F., Paradis, D., Gromov, V., Institut de recherche en astrophysique et planétologie (IRAP), Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Centre National de la Recherche Scientifique (CNRS), Synchrotron SOLEIL (SSOLEIL), Centre National de la Recherche Scientifique (CNRS), Unité Matériaux et Transformations - UMR 8207 (UMET), Centrale Lille-Institut de Chimie du CNRS (INC)-Université de Lille-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE), Laboratoire de physique et chimie des nano-objets (LPCNO), Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Institut National des Sciences Appliquées (INSA)-Université de Toulouse (UT)-Institut National des Sciences Appliquées (INSA)-Université de Toulouse (UT)-Institut de Chimie de Toulouse (ICT), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)-Institut National Polytechnique (Toulouse) (Toulouse INP), Université de Toulouse (UT)-Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)-Institut National Polytechnique (Toulouse) (Toulouse INP), Université de Toulouse (UT)-Fédération de recherche « Matière et interactions » (FeRMI), Institut National des Sciences Appliquées (INSA)-Université de Toulouse (UT)-Institut National des Sciences Appliquées (INSA)-Université de Toulouse (UT)-Université Toulouse III - Paul Sabatier (UT3), and Université de Toulouse (UT)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS)

Subjects
infrared: ISM, [SDU.ASTR]Sciences of the Universe [physics]/Astrophysics [astro-ph], extinction, astrochemistry, [SDU]Sciences of the Universe [physics], Space and Planetary Science, methods: laboratory: solid state, submillimeter: ISM, Astronomy and Astrophysics, dust, addenda, errata
Abstract

International audience; Data from this article are publicly available through the STOP-CODA (SpecTroscopy and Optical Properties of Cosmic Dust Analogues) database of the SSHADE infrastructure of solid spectroscopy (https://doi.org/10.26302/SSHADE/STOPCODA). The dataset is accessible via the following link: https://www.sshade.eu/data/experiment/EXPERIMENT_KD_20170711

Published
2022
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3. Low temperature MIR to submillimeter mass absorption coefficient of interstellar dust analogues: I. Mg-rich glassy silicates

Author

Demyk, K., Meny, C., Lu, X.-H., Papatheodorou, G., Toplis, M. J., Leroux, H., Depecker, C., Brubach, J.-B., Roy, P., Nayral, Céline, Ojo, Wilfried-Solo, Delpech, Fabien, Paradis, D., Gromov, V., Institut de recherche en astrophysique et planétologie (IRAP), Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Centre National de la Recherche Scientifique (CNRS), Institut de Physique et Chimie des Matériaux de Strasbourg (IPCMS), Université de Strasbourg (UNISTRA)-Centre National de la Recherche Scientifique (CNRS)-Matériaux et Nanosciences Grand-Est (MNGE), Université de Strasbourg (UNISTRA)-Université de Haute-Alsace (UHA) Mulhouse - Colmar (Université de Haute-Alsace (UHA))-Institut National de la Santé et de la Recherche Médicale (INSERM)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)-Université de Strasbourg (UNISTRA)-Université de Haute-Alsace (UHA) Mulhouse - Colmar (Université de Haute-Alsace (UHA))-Institut National de la Santé et de la Recherche Médicale (INSERM)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)-Réseau nanophotonique et optique, Université de Strasbourg (UNISTRA)-Université de Haute-Alsace (UHA) Mulhouse - Colmar (Université de Haute-Alsace (UHA))-Centre National de la Recherche Scientifique (CNRS)-Université de Strasbourg (UNISTRA)-Centre National de la Recherche Scientifique (CNRS), College of Materials Science and Engineering [Nanjing Forestry University], Nanjing Forestry University (NFU), Department of Geology, University of Patras, Observatoire Midi-Pyrénées (OMP), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France, Unité Matériaux et Transformations - UMR 8207 (UMET), Institut National de la Recherche Agronomique (INRA)-Ecole Nationale Supérieure de Chimie de Lille (ENSCL)-Institut de Chimie du CNRS (INC)-Université de Lille-Centre National de la Recherche Scientifique (CNRS), Synchrotron SOLEIL (SSOLEIL), Centre National de la Recherche Scientifique (CNRS), Laboratoire de physique et chimie des nano-objets (LPCNO), Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Institut National des Sciences Appliquées (INSA)-Université Fédérale Toulouse Midi-Pyrénées-Institut National des Sciences Appliquées (INSA)-Université Fédérale Toulouse Midi-Pyrénées-Institut de Chimie de Toulouse (ICT-FR 2599), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)-Institut National Polytechnique (Toulouse) (Toulouse INP), Université Fédérale Toulouse Midi-Pyrénées-Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)-Institut National Polytechnique (Toulouse) (Toulouse INP), Université Fédérale Toulouse Midi-Pyrénées-Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), Nexdot, Geological Survey of Canada [Québec] (GSC Québec), Geological Survey of Canada - Office (GSC), Natural Resources Canada (NRCan)-Natural Resources Canada (NRCan), Russian Academy of Sciences [Moscow] (RAS), French National Research Agency (ANR), program Physique et Chimie du Milieu Interstellaire (PCMI) - Conseil National de la Recherche Scientifique (CNRS) Centre National D'etudes Spatiales, Region Occitanie, and Sciences, EDP

Subjects
infrared: ISM, extinction, astrochemistry, methods: laboratory: solid state, Astrophysics::Solar and Stellar Astrophysics, submillimeter: ISM, Astrophysics::Earth and Planetary Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, dust, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], [PHYS.ASTR] Physics [physics]/Astrophysics [astro-ph], Astrophysics::Galaxy Astrophysics
Abstract

International audience; 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 – xSiO2 with x = 0.35 (close to forsterite, Mg2SiO4), 0.50 (close to enstatite, MgSiO3) and 0.40 (close to Mg1.5SiO3.5 or MgSiO3:Mg2SiO4 = 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 300–10 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 30 K, 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.

Published
2017
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4. Modelling the dust emission from dense interstellar clouds: disentangling the effects of radiative transfer and dust properties.

Author

Ysard, N., Juvela, M., Demyk, K., Guillet, V., Abergel, A., Bernard, J.-P., Malinen, J., Mérry, C., Montier, L., Paradis, D., Ristorcelli, I., and Verstraete, L.

Subjects
INTERSTELLAR medium, ASTROPHYSICS, MOLECULAR clouds, RADIATIVE transfer, WAVELENGTHS
Abstract

Context. Dust emission is increasingly used as a tracer of the mass in the interstellar medium. With the combination of Planck and Herschel observatories, we now have both the spectral coverage and the angular resolution required to observe dense and cold molecular clouds. However, as these clouds are optically thick at short wavelengths but optically thin at long wavelengths, it is tricky to conclude anything about dust properties without a proper treatment of the radiative transfer. Aims. Our aim is to disentangle the effects of radiative transfer and dust properties on the variations in the dust emission at long wavelengths. This enables us to provide observers with tools to analyse the dust emission arising from dense clouds. Methods. We model cylindrical clouds with visual extinctions between 1 and 20 mag, illuminated by the standard interstellar radiation field, and carry out full radiative transfer calculations using a Monte Carlo code. Dust temperatures are solved using the DustEM code for amorphous carbons and silicates representative of dust at high Galactic latitude (DHGL), carbon and silicate grains coated with carbon mantles, and mixed aggregates of carbon and silicate. We also allow for variations in the optical properties of the grains with wavelength and temperature. We determine observed colour temperatures, Tcolour, and emissivity spectral indices, βcolour, by fitting the dust emission with modified blackbodies using a standard χ2 fitting method, in order to compare our models with observational results. Results. Radiative transfer effects can explain neither the low Tcolour, the increased submillimetre emissivity measured at the centre of dense clouds, nor the observed βcolour - Tcolour anti-correlation for the models considered. Adding realistic noise to the modelled data, we show that it is unlikely to be the only explanation of the βcolour - Tcolour anti-correlation observed in starless clouds, which may instead be explained by intrinsic variations in the grain optical properties with temperature. Similarly the higher submillimetre emissivity and the low Tcolour have to originate in variations in the grain optical properties, probably caused by their growth to form porous aggregates. We find it difficult to infer the nature of the grains from the spectral variations in their emission, owing to radiative transfer effects for λ ≲300 pm, and to the mixture of different grain populations for longer wavelengths. Finally, the column density is underestimated when determined with modified blackbody fitting because of the discrepancy between Tcolour and the "true" dust temperature in the innermost layers of the clouds. [ABSTRACT FROM AUTHOR]

Published
2012
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