Aims: We aim to study the fraction of stellar radiation absorbed by dust, fabs, in 814 galaxies of different morphological types. The targets constitute the vast majority (93%) of the DustPedia sample, including almost all large (optical diameter larger than 1'), nearby (v ≤ 3000 km s-1) galaxies observed with the Herschel Space Observatory.

Methods: For each object, we modelled the spectral energy distribution from the ultraviolet to the sub-millimetre using the dedicated, aperture-matched DustPedia photometry and the Code Investigating GALaxy Evolution (CIGALE). The value of fabs was obtained from the total luminosity emitted by dust and from the bolometric luminosity, which are estimated by the fit.

Results: On average, 19% of the stellar radiation is absorbed by dust in DustPedia galaxies. The fraction rises to 25% if only late-type galaxies are considered. The dependence of fabs on morphology, showing a peak for Sb-Sc galaxies, is weak; it reflects a stronger, yet broad, positive correlation with the bolometric luminosity, which is identified for late-type, disk-dominated, high-specific-star-formation rate, gas-rich objects. We find no variation of fabs with inclination, at odds with radiative transfer models of edge-on galaxies. These results call for a self-consistent modelling of the evolution of the dust mass and geometry along the build-up of the stellar content. We also provide template spectral energy distributions in bins of morphology and luminosity and study the variation of fabs with stellar mass and specific star-formation rate. We confirm that the local Universe is missing the high fabs, luminous and actively star-forming objects necessary to explain the energy budget in observations of the extragalactic background light.

We have compiled the all-sky data on optical interstellar linear polarization from 13 data sources for 6420 stars without considerable intrinsic polarization from Gaia DR2 within 500 pc from the Sun. We display these data versus the stellar reddening estimates from five 3D maps and models. We have considered variations of the polarization degree P, its positional angle θ, reddening E(B-V), and polarization efficiency P/E(B-V) with the Galactic coordinates l and b, distance R, and dereddened color. A border between the Local Bubble with lower polarization and the Gould Belt with higher polarization can be drawn at P=0.1%. P has a maximum at the mid-plane of the Gould Belt, but not at the Galactic mid-plane. Too high values of P/E(B-V) from the reddening maps/models of Arenou et al., Drimmel et al., and Lallement et al. in some regions of space lead us to suggest that the reddening is systematically underestimated in these cases. The most reliable maps/models show nearly similar dust volume density E(B-V)/R everywhere in the space under consideration. The drop of P inside, compared to outside, the Bubble together with constant E(B-V)/R, i.e. dust volume density everywhere within 500 pc can be explained by a much lower volume density of neutral gas, a much higher volume density of ionized gas, the same volume density of dust, and the same gas/dust ratio inside, compared to outside, the Bubble. In the Belt, all variations of P and E(B-V) dependent on dereddened color and coordinates compensate each other, resulting in a nearly constant P/E(B-V), including a variation for different stellar spectral classes. In the Bubble, θ demonstrates a chaotic behaviour, while the Belt is dominated by a giant envelope of aligned dust oriented nearly along the Local interstellar tunnel.

This is the first study from a series on the determination of the distances, ages and extinction laws (extinction versus wavelength dependence) for the Galactic globular clusters from the comparison of their multi-color photometry with the theoretical isochrones. For the globular cluster NGC 5904 (M5), we use 24-band photometry from the UV to mid-IR range, unprecedented in accuracy and richness, presenting the H-R diagram from the tip of the red giant branch to the red part of the main sequence. The basis of this study is the space-borne observations by the Hubble, Gaia, and WISE telescopes. We use some new PARSEC, MIST, DSEP and BaSTI isochrones, for solar-scaled metallicity as well as for higher He and alpha-elements abundances. Based on spectroscopic measurements, we accept [Fe/H]=-1.33. We obtain: the distance 7.4±0.3 kpc, true distance modulus (m0-M)=14.60±0.11, age 12±1 Gyr, extinction Av=0.24±0.05, reddenings E(B-V)=0.054±0.018 and E(J-Ks)=0.050±0.011. The derived distance agrees with the commonly accepted 7.5 kpc (in the Harris catalogue), but considerably deviates from the result of Gaia DR2 (8.8 kpc). A similar effect appears for other Galactic globular clusters, which may indicate a systematic error of the Gaia DR2 parallaxes of the order of 0.02 mas for this crowded field. The derived extinction law differs from the standard one of Cardelli-Clayton-Mathis 1989 with Rv=3.1, mainly by much higher extinction in the range from 770 to 3300 nm, i.e. between Gaia DR2 RP and WISE W1 bands. As a result, the true extinction in the optical range is about 2.5 times higher than the commonly accepted value (Av=0.24 instead of 0.09 from the Harris catalogue). Similar deviations of the extinction law from the standard one are supposed by us for many Galactic globular clusters.

We present results of the detailed dust energy balance study for the seven large edge-on galaxies in the HEROES sample using three-dimensional (3D) radiative transfer (RT) modelling. Based on available optical and near-infrared (NIR) observations of the HEROES galaxies, we derive the 3D distribution of stars and dust in these galaxies. For the sake of uniformity, we apply the same technique to retrieve galaxy properties for the entire sample: we use a stellar model consisting of a Sérsic bulge and three double-exponential discs (a superthin disc for a young stellar population and thin and thick discs for old populations). For the dust component, we adopt a double-exponential disc with the new THEMIS dust-grain model. We fit oligochromatic RT models to the optical and NIR images with the fitting algorithm FITSKIRT and run panchromatic simulations with the SKIRT code at wavelengths ranging from ultraviolet to submillimeter. We confirm the previously stated dust energy balance problem in galaxies: for the HEROES galaxies, the dust emission derived from our RT calculations underestimates the real observations by a factor 1.5-4 for all galaxies except NGC 973 and NGC 5907 (apparently, the latter galaxy has a more complex geometry than we used). The comparison between our RT simulations and the observations at mid-infrared-submillimetre wavelengths shows that most of our galaxies exhibit complex dust morphologies (possible spiral arms, star-forming regions, more extended dust structure in the radial and vertical directions). We suggest that, in agreement with results from the literature, the large- and small-scale structure is the most probable explanation for the dust energy balance problem.

Gaia DR1 Tycho-Gaia Astrometric Solution parallaxes, Tycho-2 photometry, and reddening/extinction estimates from nine data sources for 38 074 giants within 415 pc from the Sun are used to compare their position in the Hertzsprung-Russell diagram with theoretical estimates, which are based on the PARSEC and MIST isochrones and the TRILEGAL model of the Galaxy with its parameters being widely varied. We conclude that (1) some systematic errors of the reddening/extinction estimates are the main uncertainty in this study; (2) any emission-based 2D reddening map cannot give reliable estimates of reddening within 415 pc due to a complex distribution of dust; (3) if a TRILEGAL's set of the parameters of the Galaxy is reliable and if the solar metallicity is Z < 0.021, then the reddening at high Galactic latitudes behind the dust layer is underestimated by all 2D reddening maps based on the dust emission observations of IRAS, COBE, and Planck and by their 3D followers (we also discuss some explanations of this underestimation); (4) the reddening/extinction estimates from recent 3D reddening map by Gontcharov, including the median reddening E(B - V) = 0.06 mag at |b| > 50°, give the best fit of the empirical and theoretical data with each other.

Aims: The DustPedia project is capitalising on the legacy of the Herschel Space Observatory, using cutting-edge modelling techniques to study dust in the 875 DustPedia galaxies - representing the vast majority of extended galaxies within 3000 km s-1 that were observed by Herschel. This work requires a database of multiwavelength imagery and photometry that greatly exceeds the scope (in terms of wavelength coverage and number of galaxies) of any previous local-Universe survey.

Methods: We constructed a database containing our own custom Herschel reductions, along with standardised archival observations from GALEX, SDSS, DSS, 2MASS, WISE, Spitzer, and Planck. Using these data, we performed consistent aperture-matched photometry, which we combined with external supplementary photometry from IRAS and Planck.

Results: We present our multiwavelength imagery and photometry across 42 UV-microwave bands for the 875 DustPedia galaxies. Our aperture-matched photometry, combined with the external supplementary photometry, represents a total of 21 857 photometric measurements. A typical DustPedia galaxy has multiwavelength photometry spanning 25 bands. We also present the Comprehensive & Adaptable Aperture Photometry Routine (CAAPR), the pipeline we developed to carry out our aperture-matched photometry. CAAPR is designed to produce consistent photometry for the enormous range of galaxy and observation types in our data. In particular, CAAPR is able to determine robust cross-compatible uncertainties, thanks to a novel method for reliably extrapolating the aperture noise for observations that cover a very limited amount of background. Our rich database of imagery and photometry is being made available to the community.