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Context. Interstellar dust particles, in particular carbonaceous nano-grains (like polycyclic aromatic hydrocarbons, fullerenes, and amorphous hydrogenated carbon), are critical players for the composition, energy budget, and dynamics of the interstellar medium (ISM). The dust properties, specifically the composition and size of dust grains are not static; instead, they exhibit considerable evolution triggered by variations in local physical conditions such as the density and gas temperature within the ISM, as is the case in photon-dominated regions (PDRs). The evolution of dust and its impact on the local physical and chemical conditions is thus a key question for understanding the first stages of star formation. Aims. From the extensive spectral and imaging data of the JWST PDRs4All program, we study the emission of dust grains within the Orion Bar – a well-known, highly far-UV (FUV)-irradiated PDR situated at the intersection between cold, dense molecular clouds, and warm ionized regions. The Orion Bar because of its edge-on geometry provides an exceptional benchmark for characterizing dust evolution and the associated driving processes under varying physical conditions. Our goal is to constrain the local properties of dust by comparing its emission to models. Taking advantage of the recent JWST data, in particular the spectroscopy of dust emission, we identify new constraints on dust and further previous works of dust modelling. Methods. To characterize interstellar dust across the Orion Bar, we follow its emission as traced by JWST NIRCam (at 3.35 and 4.8 μm) and MIRI (at 7.7, 11.3, 15.0, and 25.5 μm) broad band images, along with NIRSpec and MRS spectroscopic observations. First, we constrain the minimum size and hydrogen content of carbon nano-grains from a comparison between the observed dust emission spectra and the predictions of the Heterogeneous dust Evolution Model for Interstellar Solids (THEMIS) coupled to the numerical code DustEM. Using this dust model, we then perform 3D radiative transfer simulations of dust emission with the SOC code (Scattering with OpenCL) and compare to data obtained along well chosen profiles across the Orion Bar. Results. The JWST data allows us, for the first time, to spatially resolve the steep variation of dust emission at the illuminated edge of the Orion Bar PDR. By considering a dust model with carbonaceous nano-grains and submicronic coated silicate grains, we derive unprecedented constraints on the properties of across the Orion Bar. To explain the observed emission profiles with our simulations, we find that the nano-grains must be strongly depleted with an abundance (relative to the gas) 15 times less than in the diffuse ISM. The NIRSpec and MRS spectroscopic observations reveal variations in the hydrogenation of the carbon nano-grains. The lowest hydrogenation levels are found in the vicinity of the illuminating stars suggesting photo-processing while more hydrogenated nano-grains are found in the cold and dense molecular region, potentially indicative of larger grains. [ABSTRACT FROM AUTHOR]

Context. The diffuse interstellar bands (DIBs) are a set of hundreds of unidentified absorption features that appear almost ubiquitously throughout the interstellar medium. Most DIBs appear at optical wavelengths, but some are in the near-infrared. Aims. We aim to characterise near-infrared DIBs at high spectral resolving power towards multiple targets. Methods. We observed 76 early-type stars at a resolving power of 50 000 (velocity resolution 6 km s1) and signal-to-noise ratios of several hundreds using the CRyogenic high-resolution InfraRed Echelle Spectrograph (CRIRES). These data allow us to investigate the DIBs around 1318.1, 1527.4, 1561.1, 1565.1, 1567.0, 1574.4, and 1624.2 nm. We detected a total of six DIB features and 17 likely stellar features through comparisons with a model spectrum computed with CMFGEN. Additionally, we measured equivalent widths of the DIBs at 1318.1 and 1527.4 nm using observations with X-shooter towards ten very highly reddened (3:2 < E(BV) < 6:5) Cepheid variable stars and towards four stars observed at low values of precipitable water vapour as well as by using other archive data. Results. We measured correlations (correlation coefficient r 0:73-0.96, depending on the subsample used) between DIB equivalent width and reddening for the DIBs at 1318.1, 1561.1, 1565.1, and 1567.0 nm. Comparing the near-infrared DIBs with 50 of the strongest optical DIBs, we find correlations r > 0:8 between the 1318, 1527, 1561, 1565, and 1567 nm and the optical DIBs 5705, 5780, 6203, 6283, and 6269 Å. The 5797 Å DIB is less well correlated with the near-infrared DIBs. The DIB at 9632.1 Å, which is likely C+ 60, is not well correlated with the 1318.1 nm DIB. Partial correlation coefficients using E(B-V) as the covariate were also determined. For stars earlier than B2, the 1318.1 nm DIB is affected by an emission line on its blue wing that is likely stellar in nature, although we cannot rule out an interstellar or circumstellar origin for this line caused by, for example, a DIB in emission. The 1318.1 nm DIB also has an extended red wing. The line is reasonably well fitted by two Gaussian components, although neither the component equivalent width (EW) ratios nor the separation between components are obviously correlated with such indicators as --5780/5797 and reddening. The EW at 1318 nm correlates with H I with EW(1318 nm)/E(B V) decreasing with f (H2). Five pairs of stars within one arcmin of each other show very similar 1318.1 nm DIB profiles. Possible variation in the 1318.1 nm feature is seen between HD145501 and HD145502 (separated by 41 arcsec, equivalent to 7200 au) and HD168607 and HD168625 (separated by 67 arcsec, equivalent to 0.52 pc on the plane of the sky). Seventeen sightlines have repeat CRIRES observations separated by six to 14 months, and two sightlines have repeat X-shooter observations separated by 9.9 yr. No time variability was detected in the 1318.1 nm DIB in the CRIRES data nor in the 5780.5 Å, 5797.1 Å, 1318.1 nm, and 1527.4 nm DIBs. Tentative time variation is observed in the C+ 60 DIBs at 9577 and 9632 Å towards HD183143, although it is very close to the noise level and requires confirmation. Conclusions. The Near Infrared (NIR) DIBs observed occur more in more UV-irradiated regions than the 5797 Å DIB allowing the study of heavily reddened sightlines. Future searches for time variability in DIBs will require either higher quality data, larger intervals between epochs, or both. [ABSTRACT FROM AUTHOR]

The Nearby Evolved Stars Survey (NESS) is a volume-complete sample of ∼850 Galactic evolved stars within 3 kpc at (sub-)mm wavelengths, observed in the CO J  = (2–1) and (3–2) rotational lines, and the sub-mm continuum, using the James Clark Maxwell Telescope and Atacama Pathfinder Experiment. NESS consists of five tiers, based on distances and dust-production rate (DPR). We define a new metric for estimating the distances to evolved stars and compare its results to Gaia EDR3. Replicating other studies, the most-evolved, highly enshrouded objects in the Galactic Plane dominate the dust returned by our sources, and we initially estimate a total DPR of 4.7 × 10−5 M⊙ yr−1 from our sample. Our sub-mm fluxes are systematically higher and spectral indices are typically shallower than dust models typically predict. The 450/850 |$\mu$| m spectral indices are consistent with the blackbody Rayleigh–Jeans regime, suggesting a large fraction of evolved stars have unexpectedly large envelopes of cold dust. [ABSTRACT FROM AUTHOR]

We present infrared (IR) and submillimetre observations of the Crab-like supernova remnant (SNR) G54.1+0.3 including 350 $$\mu$$ m (SHARC-II), 870 $$\mu$$ m (LABOCA), 70, 100, 160, 250, 350, and 500  $$\mu$$ m (Herschel), and 3–40  $$\mu$$ m (Spitzer). We detect dust features at 9, 11, and 21  $$\mu$$ m and a long-wavelength continuum dust component. The 21  $$\mu$$ m dust coincides with [Ar  ii ] ejecta emission, and the feature is remarkably similar to that in Cas A. The IRAC 8 $$\mu$$ m image including Ar ejecta is distributed in a shell-like morphology which is coincident with dust features, suggesting that dust has formed in the ejecta. We create a cold dust map that shows excess emission in the northwestern shell. We fit the spectral energy distribution of the SNR using the continuous distributions of ellipsoidal grain model of pre-solar grain SiO2 that reproduces the 21 and 9  $$\mu$$ m dust features and discuss grains of silicon carbide and polycyclic aromatic hydrocarbon that may be responsible for the 10–13  $$\mu$$ m dust features. To reproduce the long-wavelength continuum, we explore models consisting of different grains including Mg2SiO4, MgSiO3, Al2O3, FeS, carbon, and Fe3O4. We tested a model with a temperature-dependent silicate absorption coefficient. We detect cold dust (27–44 K) in the remnant, making this the fourth such SNR with freshly formed dust. The total dust mass in the SNR ranges from $$0.08\text{ to }0.9\, {\rm M}_{\odot }$$ depending on the grain composition, which is comparable to predicted masses from theoretical models. Our estimated dust masses are consistent with the idea that SNe are a significant source of dust in the early Universe. [ABSTRACT FROM AUTHOR]

It is well known that the dust properties of the di use interstellar medium exhibit variations towards di erent sight-lines on a large scale.We have investigated the variability of the dust characteristics on a small scale and from cloud-to-cloud.We use low-resolution spectro-polarimetric data obtained in the context of the Large Interstellar Polarisation Survey (LIPS) towards 59 sight-lines in the Southern Hemisphere and we fit these data using a dust model composed of silicate and carbon particles with sizes from the molecular to the sub-micrometre domain. Large (⩾6 nm) silicates of prolate shape account for the observed polarisation. For 32 sight-lines we complement our data set with UVES archive high-resolution spectra, which enable us to establish the presence of single-cloud or multiple-clouds towards individual sight-lines. We find that the majority of these 35 sight-lines intersect two or more clouds, while eight of them are dominated by a single absorbing cloud. We confirm several correlations between extinction and parameters of the Serkowski law with dust parameters, but we also find previously undetected correlations between these parameters that are valid only in single-cloud sight-lines. We find that interstellar polarisation from multiple-clouds is smaller than from single-cloud sightlines, showing that the presence of a second or more clouds depolarises the incoming radiation. We find large variations of the dust characteristics from cloud-to-cloud. However, when we average a suffciently large number of clouds in single-cloud or multiple-cloud sight-lines, we always retrieve similar mean dust parameters. The typical dust abundances of the single-cloud cases are [C]/[H] = 92 ppm and [Si]/[H] = 20 ppm. [ABSTRACT FROM AUTHOR]

Supernovae (SNe) produce, fragment and destroy dust, molecules and nucleosynthetic elements, and reshape and modify the ISM. I will review recent infrared observations of supernova remnants (SNRs) and SNe which show that SNe are important sites of dust and molecule formation and are major dust creators in the Universe. Detection of carbon monoxide (CO) fundamental band from the young SNR Cas A indicates that astrochemical processes in SNRs interacting with molecular clouds provide astrophysical laboratories to study evolution of the ISM returning material from dense clouds into the more diffuse medium and galactic halo. Two dozen SNRs are known to be interacting with molecular clouds using H2 and millimeter observations. Recent Spitzer, Herschel and SOFIA observations along with ground-based observations have greatly advanced our understanding shock processing and astrochemistry of dust, H2, high J CO, and other neutral and ionized molecules and polycyclic aromatic hydrocarbon (PAH). Ionized molecules and warm layer of molecules that are excited by UV radiation, X-rays, or cosmic rays will be described. Finally I will discuss how astrochemical processes of dust and molecules in SNRs impact the large scale structures in the ISM. [ABSTRACT FROM PUBLISHER]