We conduct spectral observations of 138 superthin galaxies (STGs) with high radial-to-vertical stellar disk scale ratios with the Dual Imaging Spectrograph on the 3.5 m telescope at the Apache Point Observatory (APO) to obtain the ionized gas rotation curves with R ∼5000 resolution. We also performed near-infrared (NIR) H and Ks photometry for 18 galaxies with the NICFPS camera on the 3.5 m telescope. The spectra, the NIR photometry, and published optical and NIR photometry are used for modeling that utilizes the thickness of the stellar disk and rotation curves simultaneously. The projection and dust extinction effects are taken into account. We evaluate eight models that differ in their free parameters and constraints. As a result, we estimated the masses and scale lengths of the galactic dark halos. We find systematic differences between the properties of our red and blue STGs. The blue STGs have a large fraction of dynamically underevolved galaxies whose vertical velocity dispersion is low in both gas and stellar disks. The dark halo-to-disk scale ratio is shorter in the red STGs than in the blue ones, but in a majority of all STGs, this ratio is under 2. The optical color (r − i) of the STGs correlates with their rotation curve maximum, vertical velocity dispersion in stellar disks, and mass of the dark halo. We conclude that there is a threshold central surface density of 50 M ⊙ pc−2 below which we do not observe very thin, rotationally supported galactic disks.

Context. The efficiency of the different processes responsible for the evolution of interstellar dust on the scale of a galaxy are, to date, very uncertain, spanning several orders of magnitude in the literature. Yet, precise knowledge of the grain properties is key to addressing numerous open questions about the physics of the interstellar medium and galaxy evolution.

Aims. This article presents an empirical statistical study, aimed at quantifying the timescales of the main cosmic dust evolution processes as a function of the global properties of a galaxy.

Methods. We modeled a sample of ≃800 nearby galaxies, spanning a wide range of metallicities, gas fractions, specific star formation rates, and Hubble stages. We derived the dust properties of each object from its spectral energy distribution. Through an additional level of analysis, we inferred the timescales of dust condensation in core-collapse supernova ejecta, grain growth in cold clouds, and dust destruction by shock waves. Throughout this paper, we have adopted a hierarchical Bayesian approach, resulting in a single large probability distribution of all the parameters of all the galaxies, to ensure the most rigorous interpretation of our data.

Results. We confirm the drastic evolution with metallicity of the dust-to-metal mass ratio (by two orders of magnitude), found by previous studies. We show that dust production by core-collapse supernovae is efficient only at very low metallicity, a single supernova producing on average less than ≃0.03 M_⊙/SN of dust. Our data indicate that grain growth is the dominant formation mechanism at metallicity above ≃1/5 solar, with a grain growth timescale shorter than ≃50 Myr at solar metallicity. Shock destruction is relatively efficient, a single supernova clearing dust on average in at least ≃1200 M_⊙/SN of gas. These results are robust when assuming different stellar initial mass functions. In addition, we show that early-type galaxies are outliers in several scaling relations. This feature could result from grain thermal sputtering in hot X-ray emitting gas, which is a hypothesis supported by a negative correlation between the dust-to-stellar mass ratio and the X-ray photon rate per grain. Finally, we confirm the well-known evolution of the aromatic-feature-emitting grain mass fraction as a function of metallicity and interstellar radiation field intensity. Our data indicate that the relation with metallicity is significantly stronger.

Conclusions. Our results provide valuable constraints for simulations of galaxies. They imply that grain growth is the likely dust production mechanism in dusty high-redshift objects. We also emphasize the determinant role of local, low metallicity systems in order to address these questions.

The vast majority of stars in galaxy groups are contained within their constituent galaxies. Some small fraction of stars is expected, however, to follow the global dark matter (DM) potential of the group. In compact groups, interactions between the galaxies should be frequent. This leads to a more intensive material stripping from the group members, which finally forms an intra-group light component (IGL). Therefore, the distribution of the IGL should be related to the distribution of the total mass in the compact group and its dynamical status. In this study, we consider the distribution and fraction of the IGL in a sample of 36 Hickson compact groups (HCGs). We use deep observations of these compact groups (down to surface brightness ∼28 mag arcsec−2 in the r band) obtained with the WISE 28-in. telescope. For five HCGs with a bright symmetric IGL component, we carry out multicomponent photometric decomposition to simultaneously fit the galaxy profiles and the IGL. For the remaining groups, we only fit the profiles of their constituent galaxies. We find that the mean surface brightness of the IGL correlates with the mean morphology of the group: it becomes brighter in the groups with a larger fraction of early-type galaxies. On the other hand, the IGL brightness depends on the total luminosity of the group. The IGL profile tends to have a Sérsic index n ∼ 0.5−1, which is generally consistent with the mass density profile of DM haloes in compact groups obtained from cosmological simulations.

We exploit a complete sample of 101  810 Gaia DR2 giants, selected in Paper I in the space cylinder with a radius of 700 pc around the Sun and a height of |Z| = 1800 pc, using the Gaia DR2 parallaxes, GBP and GRP photometry, and WISE W3 photometry. We explain the spatial variations of the modes of the observables GBP − GRP and GRP − W3 by the spatial variations of the corresponding reddenings described in the GM20 3D dust distribution model. Presented in this paper, GM20 is an advanced version of the model introduced by Gontcharov in 2009. GM20 proposes two intersecting dust layers, along the Galactic mid-plane and in the Gould Belt, with exponential vertical and sinusoidal longitudinal variations of the dust spatial density in each layer. The Belt layer is an ellipse, oriented nearly between the centre and anticentre of the Galaxy, and with semi-major and semi-minor axes of 600 and 146 pc, respectively. GBP − GRP and GRP − W3 give similar solutions, but different equatorial layer scale heights of 150 ± 15 and 180 ± 15 pc, respectively, and \\$(G\_\\mathrm\\{BP\\}-G\_\\mathrm\\{RP\\})\_0=(1.14\\pm 0.01)-(0.022\\pm 0.010)\\, |Z|\\$, \\$(G\_\\mathrm\\{RP\\}-W3)\_0=(1.44\\pm 0.01)-(0.015\\pm 0.010)\\, |Z|\\$, where Z is in kpc. We compare GM20 with several 3D reddening models and maps in their ability to predict the observed colour modes. GM20 and the 3D map by Gontcharov appear to be the best among the models and maps, respectively. However, the most reliable models and maps mainly disagree only in their estimates of low reddening, including the reddening across the whole dust layer.

We consider a complete sample of 101 810 giants with Gaia Data Realease 2 (DR2) parallaxes ϖ within the red clump domain of the Hertzsprung–Russell diagram in the space cylinder with a radius of 700 pc around the Sun and a height of |Z| = 1800 pc. We use the Gaia DR2 GBP, GRP, and Wide-field Infrared Survey Explorer W3 photometry. We describe the spatial variations of the modes of the observables GBP − GRP, GRP − W3, \\$G\_\\mathrm\\{BP\\}+5+5\\, \\log \_\\{10\\}\\varpi\\$, \\$G\_\\mathrm\\{RP\\}+5+5\\, \\log \_\\{10\\}\\varpi\\$, and \\$W3+5+5\\, \\log \_\\{10\\}\\varpi\\$ by extinction and reddening in combination with linear vertical gradients of the intrinsic colours and absolute magnitudes of the red giant clump. The derived clump median absolute magnitude in W3 agrees with its recent literature estimates. The clump median intrinsic colours and absolute magnitudes in GBP and GRP are derived for the first time at a precision level of 0.01 mag. We confirm the reliability of the derived clump absolute magnitudes, intrinsic colours, and their vertical gradients by comparing them with the theoretical predictions from the PAdova and TRieste Stellar Evolution Code, MESA Isochrones and Stellar Tracks, and Bag of Stellar Tracks and Isochrones. This leads us to the median age and [Fe/H] of the clump within |Z| \\< 1.7 kpc from the Galactic mid-plane as \\$(2.3\\pm 0.5)+(3.2\\pm 1.6)\\, |Z|\\$ Gyr and \\$(-0.08\\pm 0.08)-(0.16\\pm 0.07)\\, |Z|\\$ dex, respectively, where Z is expressed in kpc. These results agree with recent empirical and theoretical estimates. Moreover, all the models give similar age–metallicity relations by use of our results in the optical range. The derived extinctions and reddenings across the whole dust half-layer below or above the Sun converge to the reddening E(B − V) = 0.06 mag by use of the most reliable extinction laws.

Context. Investigating the dust heating mechanisms in galaxies provides a deeper understanding of how the internal energy balance drives their evolution. Over the last decade radiative transfer simulations based on the Monte Carlo method have emphasised the role of the various stellar populations heating the diffuse dust. Beyond the expected heating through ongoing star formation, older stellar populations (≥8 Gyr) and even active galactic nuclei can both contribute energy to the infrared emission of diffuse dust.

Aims. In this particular study we examine how the radiation of an external heating source, such as the less massive galaxy NGC 5195 in the M 51 interacting system, could affect the heating of the diffuse dust of its parent galaxy NGC 5194, and vice versa. Our goal is to quantify the exchange of energy between the two galaxies by mapping the 3D distribution of their radiation field.

Methods. We used SKIRT, a state-of-the-art 3D Monte Carlo radiative transfer code, to construct the 3D model of the radiation field of M 51, following the methodology defined in the DustPedia framework. In the interest of modelling, the assumed centre-to-centre distance separation between the two galaxies is ∼10 kpc.

Results. Our model is able to reproduce the global spectral energy distribution of the system, and it matches the resolved optical and infrared images fairly well. In total, 40.7% of the intrinsic stellar radiation of the combined system is absorbed by dust. Furthermore, we quantify the contribution of the various dust heating sources in the system, and find that the young stellar population of NGC 5194 is the predominant dust-heating agent, with a global heating fraction of 71.2%. Another 23% is provided by the older stellar population of the same galaxy, while the remaining 5.8% has its origin in NGC 5195. Locally, we find that the regions of NGC 5194 closer to NGC 5195 are significantly affected by the radiation field of the latter, with the absorbed energy fraction rising up to 38%. The contribution of NGC 5195 remains under the percentage level in the outskirts of the disc of NGC 5194. This is the first time that the heating of the diffuse dust by a companion galaxy is quantified in a nearby interacting system.