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We build a rigorous statistical framework to provide constraints on the chemical and dust evolution parameters for nearby late-type galaxies with a wide range of gas fractions ($3\%

We build a rigorous statistical framework to provide constraints on the chemical and dust evolution parameters for nearby late-type galaxies with a wide range of gas fractions ($3\%

Dust emission, an important diagnostic of star formation and ISM mass throughout the Universe, can be powered by sources unrelated to ongoing star formation. In the framework of the DustPedia project we have set out to disentangle the radiation of the ongoing star formation from that of the older stellar populations. This is done through detailed, 3D radiative transfer simulations of face-on spiral galaxies. In this particular study, we focus on NGC 1068, which contains an active galactic nucleus (AGN). The effect of diffuse dust heating by AGN (beyond the torus) was so far only investigated for quasars. This additional dust heating source further contaminates the broadband fluxes on which classic galaxy modelling tools rely to derive physical properties. We aim to fit a realistic model to the observations of NGC 1068 and quantify the contribution of the several dust heating sources. Our model is able to reproduce the global spectral energy distribution of the galaxy. It matches the resolved optical and infrared images fairly well, but deviates in the UV and the submm. We find a strong wavelength dependency of AGN contamination to the broadband fluxes. It peaks in the MIR, drops in the FIR, but rises again at submm wavelengths. We quantify the contribution of the dust heating sources in each 3D dust cell and find a median value of 83% for the star formation component. The AGN contribution is measurable at the percentage level in the disc, but quickly increases in the inner few 100 pc, peaking above 90%. This is the first time the phenomenon of an AGN heating the diffuse dust beyond its torus is quantified in a nearby star-forming galaxy. NGC 1068 only contains a weak AGN, meaning this effect can be stronger in galaxies with a more luminous AGN. This could significantly impact the derived star formation rates and ISM masses for such systems., Comment: 18 pages, 11 figures, accepted for publication in A&A

Scaling laws of dust, HI gas and metal mass with stellar mass, specific star formation rate and metallicity are crucial to our understanding of the buildup of galaxies through their enrichment with metals and dust. In this work, we analyse how the dust and metal content varies with specific gas mass ($M_{\text{HI}}$/$M_{\star}$) across a diverse sample of 423 nearby galaxies. The observed trends are interpreted with a set of Dust and Element evolUtion modelS (DEUS) - incluidng stellar dust production, grain growth, and dust destruction - within a Bayesian framework to enable a rigorous search of the multi-dimensional parameter space. We find that these scaling laws for galaxies with $-1.0\lesssim \log M_{\text{HI}}$/$M_{\star}\lesssim0$ can be reproduced using closed-box models with high fractions (37-89$\%$) of supernova dust surviving a reverse shock, relatively low grain growth efficiencies ($\epsilon$=30-40), and long dus lifetimes (1-2\,Gyr). The models have present-day dust masses with similar contributions from stellar sources (50-80\,$\%$) and grain growth (20-50\,$\%$). Over the entire lifetime of these galaxies, the contribution from stardust ($>$90\,$\%$) outweighs the fraction of dust grown in the interstellar medium ($<$10$\%$). Our results provide an alternative for the chemical evolution models that require extremely low supernova dust production efficiencies and short grain growth timescales to reproduce local scaling laws, and could help solving the conundrum on whether or not grains can grow efficiently in the interstellar medium., Comment: 56 pages, 30 figures, accepted for publication in MNRAS

Scaling laws of dust, HI gas and metal mass with stellar mass, specific star formation rate and metallicity are crucial to our understanding of the buildup of galaxies through their enrichment with metals and dust. In this work, we analyse how the dust and metal content varies with specific gas mass ($M_{\text{HI}}$/$M_{\star}$) across a diverse sample of 423 nearby galaxies. The observed trends are interpreted with a set of Dust and Element evolUtion modelS (DEUS) - incluidng stellar dust production, grain growth, and dust destruction - within a Bayesian framework to enable a rigorous search of the multi-dimensional parameter space. We find that these scaling laws for galaxies with $-1.0\lesssim \log M_{\text{HI}}$/$M_{\star}\lesssim0$ can be reproduced using closed-box models with high fractions (37-89$\%$) of supernova dust surviving a reverse shock, relatively low grain growth efficiencies ($\epsilon$=30-40), and long dus lifetimes (1-2\,Gyr). The models have present-day dust masses with similar contributions from stellar sources (50-80\,$\%$) and grain growth (20-50\,$\%$). Over the entire lifetime of these galaxies, the contribution from stardust ($>$90\,$\%$) outweighs the fraction of dust grown in the interstellar medium ($<$10$\%$). Our results provide an alternative for the chemical evolution models that require extremely low supernova dust production efficiencies and short grain growth timescales to reproduce local scaling laws, and could help solving the conundrum on whether or not grains can grow efficiently in the interstellar medium., Comment: 56 pages, 30 figures, accepted for publication in MNRAS

Dust emission, an important diagnostic of star formation and ISM mass throughout the Universe, can be powered by sources unrelated to ongoing star formation. In the framework of the DustPedia project we have set out to disentangle the radiation of the ongoing star formation from that of the older stellar populations. This is done through detailed, 3D radiative transfer simulations of face-on spiral galaxies. In this particular study, we focus on NGC 1068, which contains an active galactic nucleus (AGN). The effect of diffuse dust heating by AGN (beyond the torus) was so far only investigated for quasars. This additional dust heating source further contaminates the broadband fluxes on which classic galaxy modelling tools rely to derive physical properties. We aim to fit a realistic model to the observations of NGC 1068 and quantify the contribution of the several dust heating sources. Our model is able to reproduce the global spectral energy distribution of the galaxy. It matches the resolved optical and infrared images fairly well, but deviates in the UV and the submm. We find a strong wavelength dependency of AGN contamination to the broadband fluxes. It peaks in the MIR, drops in the FIR, but rises again at submm wavelengths. We quantify the contribution of the dust heating sources in each 3D dust cell and find a median value of 83% for the star formation component. The AGN contribution is measurable at the percentage level in the disc, but quickly increases in the inner few 100 pc, peaking above 90%. This is the first time the phenomenon of an AGN heating the diffuse dust beyond its torus is quantified in a nearby star-forming galaxy. NGC 1068 only contains a weak AGN, meaning this effect can be stronger in galaxies with a more luminous AGN. This could significantly impact the derived star formation rates and ISM masses for such systems., Comment: 18 pages, 11 figures, accepted for publication in A&A

Aims: We compare the far-infrared to sub-millimetre dust emission properties measured in high Galactic latitude cirrus with those determined in a sample of 204 late-type DustPedia galaxies. The aim is to verify if it is appropriate to use Milky Way dust properties to derive dust masses in external galaxies. Methods: We used Herschel observations and atomic and molecular gas masses to estimate the disc-averaged dust emissivity at 250 micrometres, and from this, the absorption cross section per H atom and per dust mass. The emissivity requires one assumption, which is the CO-to-H_2 conversion factor, and the dust temperature is additionally required for the absorption cross section per H atom; yet another constraint on the dust-to-hydrogen ratio D/H, depending on metallicity, is required for the absorption cross section dust mass. Results: We find epsilon(250) = 0.82 +/- 0.07 MJy sr^-1 (1E20 H cm^-2)^-1 for galaxies with 4 < F(250)/F(500) < 5. This depends only weakly on the adopted CO-to-H_2 conversion factor. The value is almost the same as that for the Milky Way at the same colour ratio. Instead, for F(250)/F(500) > 6, epsilon(250) is lower than predicted by its dependence on the heating conditions. The reduction suggests a variation in dust emission properties for spirals of earlier type, higher metallicity, and with a higher fraction of molecular gas. When the standard emission properties of Galactic cirrus are used for these galaxies, their dust masses might be underestimated by up to a factor of two. Values for the absorption cross sections at the Milky Way metallicity are also close to those of the cirrus. Mild trends of the absorption cross sections with metallicity are found, although the results depend on the assumptions made., Comment: 13 pages, 6 figures, 2 tables, A&A accepted

The Herschel-ATLAS unbiased survey of cold dust in the local Universe is dominated by a surprising population of very blue (FUV-K < 3.5), dust-rich galaxies with high gas fractions (f_HI = M_HI/(M*+M_HI)>0.5)). Dubbed `Blue and Dusty Gas Rich Sources' (BADGRS) they have cold diffuse dust temperatures, and the highest dust-to-stellar mass ratios of any galaxies in the local Universe. Here, we explore the molecular ISM in a representative sample of BADGRS, using very deep CO(J_up=1,2,3) observations across the central and outer disk regions. We find very low CO brightnesses (Tp=15-30 mK), despite the bright far-infrared emission and metallicities in the range 0.5

We use a sub-set of the DustPedia galaxy sample (461 galaxies) to investigate the effect the environment has had on galaxies. We consider Virgo cluster and field samples and also assign a density contrast parameter to each galaxy, as defined by the local density of SDSS galaxies. We consider their chemical evolution (using M_{Dust}/M_{Baryon} and M_{Gas}/M_{Baryon}), their specific star formation rate (SFR/M_{Stars}), star formation efficiency (SFR/M_{Gas}), stars-to-dust mass ratio (M_{Stars}/M_{Dust}), gas-to-dust mass ratio (M_{Gas}/M_{Dust}) and the relationship between star formation rate per unit mass of dust and dust temperature (SFR/M_{Dust} and T_{Dust}). Late type galaxies (later than Sc) in all of the environments can be modelled using simple closed box chemical evolution and a simple star formation history (SFR(t) \propto t\exp{-t/\tau}). For earlier type galaxies the physical mechanisms that give rise to their properties are clearly much more varied and require a more complicated model (mergers, gas in or outflow). However, we find little or no difference in the properties of galaxies of the same morphological type within the cluster, field or with different density contrasts. It appears that it is morphology, how and whenever this is laid down, and consistent internal physical processes that primarily determine the derived properties of galaxies in the DustPedia sample and not processes related to differences in the local environment., Comment: Accepted for publication in Astronomy and Astrophysics

Observations of evolution in the dust-to-metal ratio allow us to constrain the dominant dust processing mechanisms. In this work, we present a study of the dust-to-metal and dust-to-gas ratios in a sub-sample of ~500 DustPedia galaxies. Using literature and MUSE emission line fluxes, we derived gas-phase metallicities (oxygen abundances) for over 10000 individual regions and determine characteristic metallicities for each galaxy. We study how the relative dust, gas, and metal contents of galaxies evolve by using metallicity and gas fraction as proxies for evolutionary state. The global oxygen abundance and nitrogen-to-oxygen ratio are found to increase monotonically as galaxies evolve. Additionally, unevolved galaxies (gas fraction > 60%, metallicity 12 + log(O/H) < 8.2) have dust-to-metal ratios that are about a factor of 2.1 lower (a factor of six lower for galaxies with gas fraction > 80%) than the typical dust-to-metal ratio (Md/MZ ~ 0.214) for more evolved sources. However, for high gas fractions, the scatter is larger due to larger observational uncertainties as well as a potential dependence of the dust grain growth timescale and supernova dust yield on local conditions and star formation histories. We find chemical evolution models with a strong contribution from dust grain growth describe these observations reasonably well. The dust-to-metal ratio is also found to be lower for low stellar masses and high specific star formation rates (with the exception of some sources undergoing a starburst). Finally, the metallicity gradient correlates weakly with the HI-to-stellar mass ratio, the effective radius and the dust-to-stellar mass ratio, but not with stellar mass., Comment: 24 pages, 15 figures, published in A&A, bibref: 2019A&A...623A...5D, This Version 2 has increased accuracy in Table B1 in appendix B

Within the framework of the DustPedia project we investigate the properties of cosmic dust and its interaction with the stellar radiation (originating from different stellar populations) for 814 galaxies in the nearby Universe, all observed by the Herschel Space Observatory. We take advantage of the widely used galaxy SED fitting code CIGALE, properly adapted to include the state-of-the-art dust model THEMIS. Using the DustPedia photometry we determine the physical properties of the galaxies, such as, the dust and stellar mass, the star-formation rate, the bolometric luminosity as well as the unattenuated and the absorbed by dust stellar light, for both the old (> 200 Myr) and young (<= 200 Myr) stellar populations. We show how the mass of stars, dust, and atomic gas, as well as the star-formation rate and the dust temperature vary between galaxies of different morphologies and provide recipes to estimate these parameters given their Hubble stage (T). We find a mild correlation between the mass fraction of the small a-C(:H) grains with the specific star-formation rate. On average, young stars are very efficient in heating the dust, with absorption fractions reaching as high as ~77% of the total, unattenuated luminosity of this population. On the other hand, the maximum absorption fraction of old stars is ~24%. Dust heating in early-type galaxies is mainly due to old stars, up to a level of ~90%. Young stars progressively contribute more for `typical' spiral galaxies and they become the dominant source of dust heating for Sm type and irregular galaxies, donating up to ~60% of their luminosity to this purpose. Finally, we find a strong correlation of the dust heating fraction by young stars with morphology and the specific star-formation rate., Comment: 22 pages, 18 figures

We use a sub-set of the DustPedia galaxy sample (461 galaxies) to investigate the effect the environment has had on galaxies. We consider Virgo cluster and field samples and also assign a density contrast parameter to each galaxy, as defined by the local density of SDSS galaxies. We consider their chemical evolution (using M_{Dust}/M_{Baryon} and M_{Gas}/M_{Baryon}), their specific star formation rate (SFR/M_{Stars}), star formation efficiency (SFR/M_{Gas}), stars-to-dust mass ratio (M_{Stars}/M_{Dust}), gas-to-dust mass ratio (M_{Gas}/M_{Dust}) and the relationship between star formation rate per unit mass of dust and dust temperature (SFR/M_{Dust} and T_{Dust}). Late type galaxies (later than Sc) in all of the environments can be modelled using simple closed box chemical evolution and a simple star formation history (SFR(t) \propto t\exp{-t/\tau}). For earlier type galaxies the physical mechanisms that give rise to their properties are clearly much more varied and require a more complicated model (mergers, gas in or outflow). However, we find little or no difference in the properties of galaxies of the same morphological type within the cluster, field or with different density contrasts. It appears that it is morphology, how and whenever this is laid down, and consistent internal physical processes that primarily determine the derived properties of galaxies in the DustPedia sample and not processes related to differences in the local environment., Comment: Accepted for publication in Astronomy and Astrophysics

Within the framework of the DustPedia project we investigate the properties of cosmic dust and its interaction with the stellar radiation (originating from different stellar populations) for 814 galaxies in the nearby Universe, all observed by the Herschel Space Observatory. We take advantage of the widely used galaxy SED fitting code CIGALE, properly adapted to include the state-of-the-art dust model THEMIS. Using the DustPedia photometry we determine the physical properties of the galaxies, such as, the dust and stellar mass, the star-formation rate, the bolometric luminosity as well as the unattenuated and the absorbed by dust stellar light, for both the old (> 200 Myr) and young (<= 200 Myr) stellar populations. We show how the mass of stars, dust, and atomic gas, as well as the star-formation rate and the dust temperature vary between galaxies of different morphologies and provide recipes to estimate these parameters given their Hubble stage (T). We find a mild correlation between the mass fraction of the small a-C(:H) grains with the specific star-formation rate. On average, young stars are very efficient in heating the dust, with absorption fractions reaching as high as ~77% of the total, unattenuated luminosity of this population. On the other hand, the maximum absorption fraction of old stars is ~24%. Dust heating in early-type galaxies is mainly due to old stars, up to a level of ~90%. Young stars progressively contribute more for `typical' spiral galaxies and they become the dominant source of dust heating for Sm type and irregular galaxies, donating up to ~60% of their luminosity to this purpose. Finally, we find a strong correlation of the dust heating fraction by young stars with morphology and the specific star-formation rate., Comment: 22 pages, 18 figures

Observations of evolution in the dust-to-metal ratio allow us to constrain the dominant dust processing mechanisms. In this work, we present a study of the dust-to-metal and dust-to-gas ratios in a sub-sample of ~500 DustPedia galaxies. Using literature and MUSE emission line fluxes, we derived gas-phase metallicities (oxygen abundances) for over 10000 individual regions and determine characteristic metallicities for each galaxy. We study how the relative dust, gas, and metal contents of galaxies evolve by using metallicity and gas fraction as proxies for evolutionary state. The global oxygen abundance and nitrogen-to-oxygen ratio are found to increase monotonically as galaxies evolve. Additionally, unevolved galaxies (gas fraction > 60%, metallicity 12 + log(O/H) < 8.2) have dust-to-metal ratios that are about a factor of 2.1 lower (a factor of six lower for galaxies with gas fraction > 80%) than the typical dust-to-metal ratio (Md/MZ ~ 0.214) for more evolved sources. However, for high gas fractions, the scatter is larger due to larger observational uncertainties as well as a potential dependence of the dust grain growth timescale and supernova dust yield on local conditions and star formation histories. We find chemical evolution models with a strong contribution from dust grain growth describe these observations reasonably well. The dust-to-metal ratio is also found to be lower for low stellar masses and high specific star formation rates (with the exception of some sources undergoing a starburst). Finally, the metallicity gradient correlates weakly with the HI-to-stellar mass ratio, the effective radius and the dust-to-stellar mass ratio, but not with stellar mass., Comment: 24 pages, 15 figures, published in A&A, bibref: 2019A&A...623A...5D, This Version 2 has increased accuracy in Table B1 in appendix B

The Herschel-ATLAS unbiased survey of cold dust in the local Universe is dominated by a surprising population of very blue (FUV-K < 3.5), dust-rich galaxies with high gas fractions (f_HI = M_HI/(M*+M_HI)>0.5)). Dubbed `Blue and Dusty Gas Rich Sources' (BADGRS) they have cold diffuse dust temperatures, and the highest dust-to-stellar mass ratios of any galaxies in the local Universe. Here, we explore the molecular ISM in a representative sample of BADGRS, using very deep CO(J_up=1,2,3) observations across the central and outer disk regions. We find very low CO brightnesses (Tp=15-30 mK), despite the bright far-infrared emission and metallicities in the range 0.5

Aims: We compare the far-infrared to sub-millimetre dust emission properties measured in high Galactic latitude cirrus with those determined in a sample of 204 late-type DustPedia galaxies. The aim is to verify if it is appropriate to use Milky Way dust properties to derive dust masses in external galaxies. Methods: We used Herschel observations and atomic and molecular gas masses to estimate the disc-averaged dust emissivity at 250 micrometres, and from this, the absorption cross section per H atom and per dust mass. The emissivity requires one assumption, which is the CO-to-H_2 conversion factor, and the dust temperature is additionally required for the absorption cross section per H atom; yet another constraint on the dust-to-hydrogen ratio D/H, depending on metallicity, is required for the absorption cross section dust mass. Results: We find epsilon(250) = 0.82 +/- 0.07 MJy sr^-1 (1E20 H cm^-2)^-1 for galaxies with 4 < F(250)/F(500) < 5. This depends only weakly on the adopted CO-to-H_2 conversion factor. The value is almost the same as that for the Milky Way at the same colour ratio. Instead, for F(250)/F(500) > 6, epsilon(250) is lower than predicted by its dependence on the heating conditions. The reduction suggests a variation in dust emission properties for spirals of earlier type, higher metallicity, and with a higher fraction of molecular gas. When the standard emission properties of Galactic cirrus are used for these galaxies, their dust masses might be underestimated by up to a factor of two. Values for the absorption cross sections at the Milky Way metallicity are also close to those of the cirrus. Mild trends of the absorption cross sections with metallicity are found, although the results depend on the assumptions made., Comment: 13 pages, 6 figures, 2 tables, A&A accepted

Galaxies continuously reprocess their interstellar material. One can therefore expect changing dust grain properties in galaxies which have followed different evolutionary pathways. Determining the intrinsic dust grain mix of a galaxy helps in reconstructing its evolutionary history. Early-type galaxies occasionally display regular dust lanes in their central regions. Due to the relatively simple geometry and composition of their stellar bodies, these galaxies are ideal to disentangle dust mix variations from geometric effects. We therefore model the various components of such a galaxy (FCC 167). We reconstruct its recent history, and investigate the possible fate of the dust lane. MUSE and ALMA observations reveal a nested ISM structure. An ionised-gas disk pervades the central regions of FCC 167, including those occupied by the main dust lane. Inward of the dust lane, we also find a disk/ring of cold molecular gas where stars are forming and HII regions contribute to the ionised-gas emission. Further in, the gas ionisation points towards an active galactic nucleus and the fuelling of a central supermassive black hole from its surrounding ionised and molecular reservoir. Observational constraints and radiative transfer models suggest the dust and gas are distributed in a ring-like geometry and the dust mix lacks small grains. The derived dust destruction timescales from sputtering in hot gas are short and we conclude that the dust must be strongly self-shielding and clumpy, or will quickly be eroded and disappear. Our findings show how detailed analysis of individual systems can complement statistical studies of dust-lane ETGs., Comment: 14 pages, 9 figures, accepted for publication in Astronomy & Astrophysics

We study the fraction of stellar radiation absorbed by dust, f_abs, 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) galaxies observed with the Herschel Space Observatory. For each object, we model the spectral energy distribution from the ultraviolet to the sub-millimetre using the dedicated, aperture-matched DustPedia photometry and the fitting code CIGALE. The value of f_abs is obtained from the total luminosity emitted by dust and from the bolometric luminosity, which are estimated by the fit. 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 f_abs 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 f_abs 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 f_abs with stellar mass and specific star formation rate. We confirm that the local Universe is missing the high f_abs}, luminous and actively star-forming objects necessary to explain the energy budget in observations of the extragalactic background light., Comment: 21 pages, 14 figures, A&A accepted. Template SEDs available at the DustPedia Archive: http://dustpedia.astro.noa.gr

Most radiative transfer models assume that dust in spiral galaxies is distributed exponentially. In this paper our goal is to verify this assumption by analysing the two-dimensional large-scale distribution of dust in galaxies from the DustPedia sample. For this purpose, we make use of Herschel imaging in five bands, from 100 to 500{\mu}m, in which the cold dust constituent is primarily traced and makes up the bulk of the dust mass in spiral galaxies. For a subsample of 320 disc galaxies, we successfully perform a simultaneous fitting with a single S\'ersic model of the Herschel images in all five bands using the multiband modelling code GALFITM. We report that the S\'ersic index $n$, which characterises the shape of the S\'ersic profile, lies systematically below 1 in all Herschel bands and is almost constant with wavelength. The average value at 250{\mu}m is $0.67\pm0.37$ (187 galaxies are fitted with $n_{250}\leq0.75$, 87 galaxies have $0.751.25$). Most observed profiles exhibit a depletion in the inner region (at $r<0.3-0.4$ of the optical radius $r_{25}$ ) and are more or less exponential in the outer part. We also find breaks in the dust emission profiles at longer distances $(0.5-0.6)r_{25}$ which are associated with the breaks in the optical and near-infrared. We assume that the observed deficit of dust emission in the inner galaxy region is related to the depression in the radial profile of the HI surface density in the same region because the atomic gas reaches high enough surface densities there to be transformed into molecular gas. If a galaxy has a triggered star formation in the inner region (for example, because of a strong bar instability, which transfers the gas inwards to the centre, or a pseudobulge formation), no depletion or even an excess of dust emission in the centre is observed., Comment: 24 pages, 17 figures, Accepted for publication in Astronomy & Astrophysics

Galaxies continuously reprocess their interstellar material. One can therefore expect changing dust grain properties in galaxies which have followed different evolutionary pathways. Determining the intrinsic dust grain mix of a galaxy helps in reconstructing its evolutionary history. Early-type galaxies occasionally display regular dust lanes in their central regions. Due to the relatively simple geometry and composition of their stellar bodies, these galaxies are ideal to disentangle dust mix variations from geometric effects. We therefore model the various components of such a galaxy (FCC 167). We reconstruct its recent history, and investigate the possible fate of the dust lane. MUSE and ALMA observations reveal a nested ISM structure. An ionised-gas disk pervades the central regions of FCC 167, including those occupied by the main dust lane. Inward of the dust lane, we also find a disk/ring of cold molecular gas where stars are forming and HII regions contribute to the ionised-gas emission. Further in, the gas ionisation points towards an active galactic nucleus and the fuelling of a central supermassive black hole from its surrounding ionised and molecular reservoir. Observational constraints and radiative transfer models suggest the dust and gas are distributed in a ring-like geometry and the dust mix lacks small grains. The derived dust destruction timescales from sputtering in hot gas are short and we conclude that the dust must be strongly self-shielding and clumpy, or will quickly be eroded and disappear. Our findings show how detailed analysis of individual systems can complement statistical studies of dust-lane ETGs., Comment: 14 pages, 9 figures, accepted for publication in Astronomy & Astrophysics

Most radiative transfer models assume that dust in spiral galaxies is distributed exponentially. In this paper our goal is to verify this assumption by analysing the two-dimensional large-scale distribution of dust in galaxies from the DustPedia sample. For this purpose, we make use of Herschel imaging in five bands, from 100 to 500{\mu}m, in which the cold dust constituent is primarily traced and makes up the bulk of the dust mass in spiral galaxies. For a subsample of 320 disc galaxies, we successfully perform a simultaneous fitting with a single S\'ersic model of the Herschel images in all five bands using the multiband modelling code GALFITM. We report that the S\'ersic index $n$, which characterises the shape of the S\'ersic profile, lies systematically below 1 in all Herschel bands and is almost constant with wavelength. The average value at 250{\mu}m is $0.67\pm0.37$ (187 galaxies are fitted with $n_{250}\leq0.75$, 87 galaxies have $0.751.25$). Most observed profiles exhibit a depletion in the inner region (at $r<0.3-0.4$ of the optical radius $r_{25}$ ) and are more or less exponential in the outer part. We also find breaks in the dust emission profiles at longer distances $(0.5-0.6)r_{25}$ which are associated with the breaks in the optical and near-infrared. We assume that the observed deficit of dust emission in the inner galaxy region is related to the depression in the radial profile of the HI surface density in the same region because the atomic gas reaches high enough surface densities there to be transformed into molecular gas. If a galaxy has a triggered star formation in the inner region (for example, because of a strong bar instability, which transfers the gas inwards to the centre, or a pseudobulge formation), no depletion or even an excess of dust emission in the centre is observed., Comment: 24 pages, 17 figures, Accepted for publication in Astronomy & Astrophysics

We study the fraction of stellar radiation absorbed by dust, f_abs, 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) galaxies observed with the Herschel Space Observatory. For each object, we model the spectral energy distribution from the ultraviolet to the sub-millimetre using the dedicated, aperture-matched DustPedia photometry and the fitting code CIGALE. The value of f_abs is obtained from the total luminosity emitted by dust and from the bolometric luminosity, which are estimated by the fit. 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 f_abs 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 f_abs 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 f_abs with stellar mass and specific star formation rate. We confirm that the local Universe is missing the high f_abs}, luminous and actively star-forming objects necessary to explain the energy budget in observations of the extragalactic background light., Comment: 21 pages, 14 figures, A&A accepted. Template SEDs available at the DustPedia Archive: http://dustpedia.astro.noa.gr

We present the dust mass function (DMF) of 15,750 galaxies with redshift $z< 0.1$, drawn from the overlapping area of the GAMA and {\it H-}ATLAS surveys. The DMF is derived using the density corrected $V_{\rm max}$ method, where we estimate $V_{\rm max}$ using: (i) the normal photometric selection limit ($pV_{\rm max}$) and (ii) a bivariate brightness distribution (BBD) technique, which accounts for two selection effects. We fit the data with a Schechter function, and find $M^{*}=(4.65\pm0.18)\times 10^{7}\,h^2_{70}\, M_{\odot}$, $\alpha=(1.22\pm 0.01)$, $\phi^{*}=(6.26\pm 0.28)\times 10^{-3}\,h^3_{70}\,\rm Mpc^{-3}\,dex^{-1}$. The resulting dust mass density parameter integrated down to $10^4\,M_{\odot}$ is $\Omega_{\rm d}=(1.11 \pm0.02)\times 10^{-6}$ which implies the mass fraction of baryons in dust is $f_{m_b}=(2.40\pm0.04)\times 10^{-5}$; cosmic variance adds an extra 7-17\,per\,cent uncertainty to the quoted statistical errors. Our measurements have fewer galaxies with high dust mass than predicted by semi-analytic models. This is because the models include too much dust in high stellar mass galaxies. Conversely, our measurements find more galaxies with high dust mass than predicted by hydrodynamical cosmological simulations. This is likely to be from the long timescales for grain growth assumed in the models. We calculate DMFs split by galaxy type and find dust mass densities of $\Omega_{\rm d}=(0.88\pm0.03)\times 10^{-6}$ and $\Omega_{\rm d}=(0.060\pm0.005)\times 10^{-6}$ for late-types and early-types respectively. Comparing to the equivalent galaxy stellar mass functions (GSMF) we find that the DMF for late-types is well matched by the GMSF scaled by $(8.07\pm0.35) \times 10^{-4}$., Comment: 25 Pages, 18 Figures. Submitted December 2017

We combine samples of nearby galaxies with Herschel photometry selected on their dust, metal, HI, and stellar mass content, and compare these to chemical evolution models in order to discriminate between different dust sources. In a companion paper, we used a HI-selected sample of nearby galaxies to reveal a sub-sample of very gas rich (gas fraction > 80 per cent) sources with dust masses significantly below predictions from simple chemical evolution models, and well below $M_d/M_*$ and $M_d/M_{gas}$ scaling relations seen in dust and stellar-selected samples of local galaxies. We use a chemical evolution model to explain these dust-poor, but gas-rich, sources as well as the observed star formation rates (SFRs) and dust-to-gas ratios. We find that (i) a delayed star formation history is required to model the observed SFRs; (ii) inflows and outflows are required to model the observed metallicities at low gas fractions; (iii) a reduced contribution of dust from supernovae (SNe) is needed to explain the dust-poor sources with high gas fractions. These dust-poor, low stellar mass galaxies require a typical core-collapse SN to produce 0.01 - 0.16 $M_{\odot}$ of dust. To match the observed dust masses at lower gas fractions, significant grain growth is required to counteract the reduced contribution from dust in SNe and dust destruction from SN shocks. These findings are statistically robust, though due to intrinsic scatter it is not always possible to find one single model that successfully describes all the data. We also show that the dust-to-metals ratio decreases towards lower metallicity., Comment: 15 pages (+10 pages appendix), 8 figures, Accepted for publication in MNRAS

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. 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. 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, Comment: Accepted for publication in Astronomy & Astrophysics

The purpose of this work is the characterization of the radial distribution of dust, stars, gas, and star-formation rate (SFR) in a sub-sample of 18 face-on spiral galaxies extracted from the DustPedia sample. This study is performed by exploiting the multi-wavelength, from UV to sub-mm bands, DustPedia database, in addition to molecular (12CO) and atomic (HI) gas maps and metallicity abundance information available in the literature. We fitted the surface brightness profiles of the tracers of dust and stars, the mass surface density profiles of dust, stars, molecular gas, and total gas, and the SFR surface density profiles with an exponential curve and derived their scale-lengths. We also developed a method to solve for the CO-to-H2 conversion factor (alpha_CO) per galaxy by using dust and gas mass profiles. Although each galaxy has its own peculiar behaviour, we identified a common trend of the exponential scale-lengths vs. wavelength. On average, the scale-lengths normalized to the B-band 25 mag/arcsec^2 radius decrease from UV to 70 micron, from 0.4 to 0.2, and then increase back up to 0.3 at 500 microns. The main result is that, on average, the dust mass surface density scale-length is about 1.8 times the stellar one derived from IRAC data and the 3.6 micron surface brightness, and close to that in the UV. We found a mild dependence of the scale-lengths on the Hubble stage T: the scale-lengths of the Herschel bands and the 3.6 micron scale-length tend to increase from earlier to later types, the scale-length at 70 micron tends to be smaller than that at longer sub-mm wavelength with ratios between longer sub-mm wavelengths and 70 micron that decrease with increasing T. The scale-length ratio of SFR and stars shows a weak increasing trend towards later types., Comment: 33 pages, 9 figures (at low resolution here), 8 tables, Accepted for publication in A&A

We present the dust mass function (DMF) of 15,750 galaxies with redshift $z< 0.1$, drawn from the overlapping area of the GAMA and {\it H-}ATLAS surveys. The DMF is derived using the density corrected $V_{\rm max}$ method, where we estimate $V_{\rm max}$ using: (i) the normal photometric selection limit ($pV_{\rm max}$) and (ii) a bivariate brightness distribution (BBD) technique, which accounts for two selection effects. We fit the data with a Schechter function, and find $M^{*}=(4.65\pm0.18)\times 10^{7}\,h^2_{70}\, M_{\odot}$, $\alpha=(1.22\pm 0.01)$, $\phi^{*}=(6.26\pm 0.28)\times 10^{-3}\,h^3_{70}\,\rm Mpc^{-3}\,dex^{-1}$. The resulting dust mass density parameter integrated down to $10^4\,M_{\odot}$ is $\Omega_{\rm d}=(1.11 \pm0.02)\times 10^{-6}$ which implies the mass fraction of baryons in dust is $f_{m_b}=(2.40\pm0.04)\times 10^{-5}$; cosmic variance adds an extra 7-17\,per\,cent uncertainty to the quoted statistical errors. Our measurements have fewer galaxies with high dust mass than predicted by semi-analytic models. This is because the models include too much dust in high stellar mass galaxies. Conversely, our measurements find more galaxies with high dust mass than predicted by hydrodynamical cosmological simulations. This is likely to be from the long timescales for grain growth assumed in the models. We calculate DMFs split by galaxy type and find dust mass densities of $\Omega_{\rm d}=(0.88\pm0.03)\times 10^{-6}$ and $\Omega_{\rm d}=(0.060\pm0.005)\times 10^{-6}$ for late-types and early-types respectively. Comparing to the equivalent galaxy stellar mass functions (GSMF) we find that the DMF for late-types is well matched by the GMSF scaled by $(8.07\pm0.35) \times 10^{-4}$., Comment: 25 Pages, 18 Figures. Submitted December 2017

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. 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. 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, Comment: Accepted for publication in Astronomy & Astrophysics

The purpose of this work is the characterization of the radial distribution of dust, stars, gas, and star-formation rate (SFR) in a sub-sample of 18 face-on spiral galaxies extracted from the DustPedia sample. This study is performed by exploiting the multi-wavelength, from UV to sub-mm bands, DustPedia database, in addition to molecular (12CO) and atomic (HI) gas maps and metallicity abundance information available in the literature. We fitted the surface brightness profiles of the tracers of dust and stars, the mass surface density profiles of dust, stars, molecular gas, and total gas, and the SFR surface density profiles with an exponential curve and derived their scale-lengths. We also developed a method to solve for the CO-to-H2 conversion factor (alpha_CO) per galaxy by using dust and gas mass profiles. Although each galaxy has its own peculiar behaviour, we identified a common trend of the exponential scale-lengths vs. wavelength. On average, the scale-lengths normalized to the B-band 25 mag/arcsec^2 radius decrease from UV to 70 micron, from 0.4 to 0.2, and then increase back up to 0.3 at 500 microns. The main result is that, on average, the dust mass surface density scale-length is about 1.8 times the stellar one derived from IRAC data and the 3.6 micron surface brightness, and close to that in the UV. We found a mild dependence of the scale-lengths on the Hubble stage T: the scale-lengths of the Herschel bands and the 3.6 micron scale-length tend to increase from earlier to later types, the scale-length at 70 micron tends to be smaller than that at longer sub-mm wavelength with ratios between longer sub-mm wavelengths and 70 micron that decrease with increasing T. The scale-length ratio of SFR and stars shows a weak increasing trend towards later types., Comment: 33 pages, 9 figures (at low resolution here), 8 tables, Accepted for publication in A&A

We combine samples of nearby galaxies with Herschel photometry selected on their dust, metal, HI, and stellar mass content, and compare these to chemical evolution models in order to discriminate between different dust sources. In a companion paper, we used a HI-selected sample of nearby galaxies to reveal a sub-sample of very gas rich (gas fraction > 80 per cent) sources with dust masses significantly below predictions from simple chemical evolution models, and well below $M_d/M_*$ and $M_d/M_{gas}$ scaling relations seen in dust and stellar-selected samples of local galaxies. We use a chemical evolution model to explain these dust-poor, but gas-rich, sources as well as the observed star formation rates (SFRs) and dust-to-gas ratios. We find that (i) a delayed star formation history is required to model the observed SFRs; (ii) inflows and outflows are required to model the observed metallicities at low gas fractions; (iii) a reduced contribution of dust from supernovae (SNe) is needed to explain the dust-poor sources with high gas fractions. These dust-poor, low stellar mass galaxies require a typical core-collapse SN to produce 0.01 - 0.16 $M_{\odot}$ of dust. To match the observed dust masses at lower gas fractions, significant grain growth is required to counteract the reduced contribution from dust in SNe and dust destruction from SN shocks. These findings are statistically robust, though due to intrinsic scatter it is not always possible to find one single model that successfully describes all the data. We also show that the dust-to-metals ratio decreases towards lower metallicity., Comment: 15 pages (+10 pages appendix), 8 figures, Accepted for publication in MNRAS

We present a study of the dust, stars and atomic gas (HI) in an HI-selected sample of local galaxies (z<0.035) in the Herschel Astrophysical Terahertz Large Area Survey (H-ATLAS) fields. This HI-selected sample reveals a population of very high gas fraction (>80 per cent), low stellar mass sources that appear to be in the earliest stages of their evolution. We compare this sample with dust and stellar mass selected samples to study the dust and gas scaling relations over a wide range of gas fraction (proxy for evolutionary state of a galaxy). The most robust scaling relations for gas and dust are those linked to NUV-r (SSFR) and gas fraction, these do not depend on sample selection or environment. At the highest gas fractions, our additional sample shows the dust content is well below expectations from extrapolating scaling relations for more evolved sources, and dust is not a good tracer of the gas content. The specific dust mass for local galaxies peaks at a gas fraction of ~75 per cent. The atomic gas depletion time is also longer for high gas fraction galaxies, opposite to the trend found for molecular gas depletion timescale. We link this trend to the changing efficiency of conversion of HI to H2 as galaxies increase in stellar mass surface density as they evolve. Finally, we show that galaxies start out barely obscured and increase in obscuration as they evolve, yet there is no clear and simple link between obscuration and global galaxy properties., Comment: 16 pages (+11 pages appendix), 12 figures, Published in 2017 in MNRAS, 464, 4680; This version 2 has corrected a small error in the table heading of Table 1, but is otherwise unchanged

The radiation of stars heats dust grains in the diffuse interstellar medium and in star-forming regions in galaxies. Modelling this interaction provides information on dust in galaxies, a vital ingredient for their evolution. It is not straightforward to identify the stellar populations heating the dust, and to link attenuation to emission on a sub-galactic scale. Radiative transfer models are able to simulate this dust-starlight interaction in a realistic, three-dimensional setting. We investigate the dust heating mechanisms on a local and global galactic scale, using the Andromeda galaxy (M31) as our laboratory. We perform a series of panchromatic radiative transfer simulations of Andromeda with our code SKIRT. The high inclination angle of M31 complicates the 3D modelling and causes projection effects. However, the observed morphology and flux density are reproduced fairly well from UV to sub-millimeter wavelengths. Our model reveals a realistic attenuation curve, compatible with previous, observational estimates. We find that the dust in M31 is mainly (91 % of the absorbed luminosity) heated by the evolved stellar populations. The bright bulge produces a strong radiation field and induces non-local heating up to the main star-forming ring at 10 kpc. The relative contribution of unevolved stellar populations to the dust heating varies strongly with wavelength and with galactocentric distance.The dust heating fraction of unevolved stellar populations correlates strongly with NUV-r colour and specific star formation rate. These two related parameters are promising probes for the dust heating sources at a local scale., Comment: 16 pages + appendix, 13 figures, accepted for publication in A&A

We present a study of the dust, stars and atomic gas (HI) in an HI-selected sample of local galaxies (z<0.035) in the Herschel Astrophysical Terahertz Large Area Survey (H-ATLAS) fields. This HI-selected sample reveals a population of very high gas fraction (>80 per cent), low stellar mass sources that appear to be in the earliest stages of their evolution. We compare this sample with dust and stellar mass selected samples to study the dust and gas scaling relations over a wide range of gas fraction (proxy for evolutionary state of a galaxy). The most robust scaling relations for gas and dust are those linked to NUV-r (SSFR) and gas fraction, these do not depend on sample selection or environment. At the highest gas fractions, our additional sample shows the dust content is well below expectations from extrapolating scaling relations for more evolved sources, and dust is not a good tracer of the gas content. The specific dust mass for local galaxies peaks at a gas fraction of ~75 per cent. The atomic gas depletion time is also longer for high gas fraction galaxies, opposite to the trend found for molecular gas depletion timescale. We link this trend to the changing efficiency of conversion of HI to H2 as galaxies increase in stellar mass surface density as they evolve. Finally, we show that galaxies start out barely obscured and increase in obscuration as they evolve, yet there is no clear and simple link between obscuration and global galaxy properties., Comment: 16 pages (+11 pages appendix), 12 figures, Published in 2017 in MNRAS, 464, 4680; This version 2 has corrected a small error in the table heading of Table 1, but is otherwise unchanged

The radiation of stars heats dust grains in the diffuse interstellar medium and in star-forming regions in galaxies. Modelling this interaction provides information on dust in galaxies, a vital ingredient for their evolution. It is not straightforward to identify the stellar populations heating the dust, and to link attenuation to emission on a sub-galactic scale. Radiative transfer models are able to simulate this dust-starlight interaction in a realistic, three-dimensional setting. We investigate the dust heating mechanisms on a local and global galactic scale, using the Andromeda galaxy (M31) as our laboratory. We perform a series of panchromatic radiative transfer simulations of Andromeda with our code SKIRT. The high inclination angle of M31 complicates the 3D modelling and causes projection effects. However, the observed morphology and flux density are reproduced fairly well from UV to sub-millimeter wavelengths. Our model reveals a realistic attenuation curve, compatible with previous, observational estimates. We find that the dust in M31 is mainly (91 % of the absorbed luminosity) heated by the evolved stellar populations. The bright bulge produces a strong radiation field and induces non-local heating up to the main star-forming ring at 10 kpc. The relative contribution of unevolved stellar populations to the dust heating varies strongly with wavelength and with galactocentric distance.The dust heating fraction of unevolved stellar populations correlates strongly with NUV-r colour and specific star formation rate. These two related parameters are promising probes for the dust heating sources at a local scale., Comment: 16 pages + appendix, 13 figures, accepted for publication in A&A

We present a study of the dust, stars and atomic gas (H i) in an H i-selected sample of local galaxies (z < 0.035) in the Herschel Astrophysical Terahertz Large Area Survey fields. This H i-selected sample reveals a population of very high gas fraction (>80 per cent), low stellar mass sources that appear to be in the earliest stages of their evolution. We compare this sample with dust- and stellar-mass-selected samples to study the dust and gas scaling relations over a wide range of gas fractions (proxy for evolutionary state of a galaxy). The most robust scaling relations for gas and dust are those linked to near-ultraviolet − r (specific star formation rate) and gas fraction; these do not depend on sample selection or environment. At the highest gas fractions, our additional sample shows that the dust content is well below expectations from extrapolating scaling relations for more evolved sources, and dust is not a good tracer of the gas content. The specific dust mass for local galaxies peaks at a gas fraction of ∼75 per cent. The atomic gas depletion time is also longer for high gas fraction galaxies, opposite to the trend found for molecular gas depletion time-scale. We link this trend to the changing efficiency of conversion of H i to H2 as galaxies increase in stellar mass surface density during their evolution. Finally, we show that galaxies start out barely obscured and increase in obscuration as they evolve, yet there is no clear and simple link between obscuration and global galaxy properties.

We present a study of the dust, stars and atomic gas (H i) in an H i-selected sample of local galaxies (z < 0.035) in the Herschel Astrophysical Terahertz Large Area Survey fields. This H i-selected sample reveals a population of very high gas fraction (>80 per cent), low stellar mass sources that appear to be in the earliest stages of their evolution. We compare this sample with dust- and stellar-mass-selected samples to study the dust and gas scaling relations over a wide range of gas fractions (proxy for evolutionary state of a galaxy). The most robust scaling relations for gas and dust are those linked to near-ultraviolet − r (specific star formation rate) and gas fraction; these do not depend on sample selection or environment. At the highest gas fractions, our additional sample shows that the dust content is well below expectations from extrapolating scaling relations for more evolved sources, and dust is not a good tracer of the gas content. The specific dust mass for local galaxies peaks at a gas fraction of ∼75 per cent. The atomic gas depletion time is also longer for high gas fraction galaxies, opposite to the trend found for molecular gas depletion time-scale. We link this trend to the changing efficiency of conversion of H i to H2 as galaxies increase in stellar mass surface density during their evolution. Finally, we show that galaxies start out barely obscured and increase in obscuration as they evolve, yet there is no clear and simple link between obscuration and global galaxy properties.

We present a study of the dust, stars and atomic gas (H i) in an H i-selected sample of local galaxies (z < 0.035) in the Herschel Astrophysical Terahertz Large Area Survey fields. This H i-selected sample reveals a population of very high gas fraction (>80 per cent), low stellar mass sources that appear to be in the earliest stages of their evolution. We compare this sample with dust- and stellar-mass-selected samples to study the dust and gas scaling relations over a wide range of gas fractions (proxy for evolutionary state of a galaxy). The most robust scaling relations for gas and dust are those linked to near-ultraviolet − r (specific star formation rate) and gas fraction; these do not depend on sample selection or environment. At the highest gas fractions, our additional sample shows that the dust content is well below expectations from extrapolating scaling relations for more evolved sources, and dust is not a good tracer of the gas content. The specific dust mass for local galaxies peaks at a gas fraction of ∼75 per cent. The atomic gas depletion time is also longer for high gas fraction galaxies, opposite to the trend found for molecular gas depletion time-scale. We link this trend to the changing efficiency of conversion of H i to H2 as galaxies increase in stellar mass surface density during their evolution. Finally, we show that galaxies start out barely obscured and increase in obscuration as they evolve, yet there is no clear and simple link between obscuration and global galaxy properties.

We present a study of the dust, stars and atomic gas (H i) in an H i-selected sample of local galaxies (z < 0.035) in the Herschel Astrophysical Terahertz Large Area Survey fields. This H i-selected sample reveals a population of very high gas fraction (>80 per cent), low stellar mass sources that appear to be in the earliest stages of their evolution. We compare this sample with dust- and stellar-mass-selected samples to study the dust and gas scaling relations over a wide range of gas fractions (proxy for evolutionary state of a galaxy). The most robust scaling relations for gas and dust are those linked to near-ultraviolet − r (specific star formation rate) and gas fraction; these do not depend on sample selection or environment. At the highest gas fractions, our additional sample shows that the dust content is well below expectations from extrapolating scaling relations for more evolved sources, and dust is not a good tracer of the gas content. The specific dust mass for local galaxies peaks at a gas fraction of ∼75 per cent. The atomic gas depletion time is also longer for high gas fraction galaxies, opposite to the trend found for molecular gas depletion time-scale. We link this trend to the changing efficiency of conversion of H i to H2 as galaxies increase in stellar mass surface density during their evolution. Finally, we show that galaxies start out barely obscured and increase in obscuration as they evolve, yet there is no clear and simple link between obscuration and global galaxy properties.