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A quantitative derivation of the intrinsic properties of galaxies related to their fundamental building blocks, gas, dust, and stars is essential for our understanding of galaxy evolution. A fully self-consistent derivation of these properties can be achieved with radiative transfer (RT) methods that are constrained by panchromatic imaging observations. Here, we present an axi-symmetric RT model of the UV-optical-FIR/submm spectral and spatial energy distribution of the face-on spiral galaxy M51. The model reproduces reasonably well the azimuthally averaged radial profiles derived from the imaging data available for this galaxy, from GALEX , Sloan Digital Sky Survey, 2MASS, Spitzer , and Herschel. We model the galaxy with three distinct morphological components: a bulge, an inner disc, and a main disc. We derive the length parameters of the stellar emissivity and of the dust distribution. We also derive the intrinsic global and spatially resolved parameters of M51. We find a faint 'outer disc' bridging M51 with its companion galaxy M51b. Finally, we present and discuss an alternative model, with dust properties that change within the galaxy. [ABSTRACT FROM AUTHOR]

We obtained an axisymmetric model for the large-scale distribution of stars and dust in the Milky Way (MW) using a radiative transfer code that can account for the existing near-infrared (NIR)/mid-infrared/submm all-sky emission maps of our Galaxy. We find that the MW has a star-formation rate of |${\rm SFR}=1.25\pm 0.2\, {\rm M}_{\odot }$|  yr−1, a stellar mass |$M_{*}=(4.9\pm 0.3)\times 10^{10}\, {\rm M}_{\odot }$|⁠ , and a specific SFR that is relatively constant with radius (except for the inner 1 kpc). We identified an inner radius R in = 4.5 kpc beyond which the stellar emissivity and dust distribution fall exponentially. For R < R in the emissivities fall linearly towards the centre. The old stellar populations in the disc have an exponential scale length that increases monotonically from |$h_{\rm s}^{\rm disc}(K)=2.2\pm 0.6$|  kpc in the NIR, to |$h_{\rm s}^{\rm disc}(B)=3.2\pm 0.9$|  kpc at the shorter optical bands, and a scale height that varies with radial distance, from |$z_{\rm s}^{\rm disc}(0) =140\pm 20$|  pc in the centre to |$z_{\rm s}^{\rm disc}(R_{\odot }) =300\pm 20$|  pc at the solar radius. The young stellar populations have a scale length of |$h_{\rm s}^{\rm tdisc}=3.2\pm 0.9$|  kpc and a scale height that varies from |$z_{\rm s}^{\rm tdisc}(0)=50\pm 10$|  pc in the centre to |$z_{\rm s}^{\rm tdisc}(R_{\odot })=90\pm 10$|  pc at the solar radius. We discovered an inner stellar disc within the central 4.5 kpc, which we associate with the extended long bar of the MW. Most of the obscured star formation happens within this inner thin disc. The diffuse dust is mainly distributed in a disc with scale length |$h_{\rm d}^{\rm disc}=5.2\pm 0.8$|  kpc and scale height |$z_{\rm d}^{\rm disc}=0.14\pm 0.02$|  kpc. We give the first derivation of the MW attenuation curve and present it as a functional fit to the model data. We find the MW to lie in the Green Valley of the main sequence relation for spiral galaxies. [ABSTRACT FROM AUTHOR]

We present the first radiative transfer (RT) model of a non-edge-on disc galaxy in which the large-scale geometry of stars and dust is self-consistently derived through the fitting of multiwavelength imaging observations from the ultraviolet to the submm. To this end, we used the axisymmetric RT model of Popescu et al. and a new methodology for deriving geometrical parameters, and applied this to decode the spectral energy distribution (SED) of M33. We successfully account for both the spatial and spectral energy distribution, with residuals typically within |$7{{\ \rm per\ cent}}$| in the profiles of surface brightness and within |$8{{\ \rm per\ cent}}$| in the spatially integrated SED. We predict well the energy balance between absorption and re-emission by dust, with no need to invoke modified grain properties, and we find no submm emission that is in excess of our model predictions. We calculate that |$80\pm 8{{\ \rm per\ cent}}$| of the dust heating is powered by the young stellar populations. We identify several morphological components in M33, a nuclear, an inner, a main and an outer disc, showing a monotonic trend in decreasing star formation surface density (ΣSFR) from the nuclear to the outer disc. In relation to surface density of stellar mass, the ΣSFR of these components defines a steeper relation than the 'main sequence' of star-forming galaxies, which we call a 'structurally resolved main sequence'. Either environmental or stellar feedback mechanisms could explain the slope of the newly defined sequence. We find the star formation rate to be |${\rm SFR}=0.28^{+0.02}_{-0.01}{\rm M}_{\odot }{\rm yr}^{-1}$|⁠. [ABSTRACT FROM AUTHOR]

We present the first radiative transfer (RT) model of a non-edge-on disc galaxy in which the large-scale geometry of stars and dust is self-consistently derived through the fitting of multiwavelength imaging observations from the ultraviolet to the submm. To this end, we used the axisymmetric RT model of Popescu et al. and a new methodology for deriving geometrical parameters, and applied this to decode the spectral energy distribution (SED) of M33. We successfully account for both the spatial and spectral energy distribution, with residuals typically within |$7{{\ \rm per\ cent}}$| in the profiles of surface brightness and within |$8{{\ \rm per\ cent}}$| in the spatially integrated SED. We predict well the energy balance between absorption and re-emission by dust, with no need to invoke modified grain properties, and we find no submm emission that is in excess of our model predictions. We calculate that |$80\pm 8{{\ \rm per\ cent}}$| of the dust heating is powered by the young stellar populations. We identify several morphological components in M33, a nuclear, an inner, a main and an outer disc, showing a monotonic trend in decreasing star formation surface density (ΣSFR) from the nuclear to the outer disc. In relation to surface density of stellar mass, the ΣSFR of these components defines a steeper relation than the 'main sequence' of star-forming galaxies, which we call a 'structurally resolved main sequence'. Either environmental or stellar feedback mechanisms could explain the slope of the newly defined sequence. We find the star formation rate to be |${\rm SFR}=0.28^{+0.02}_{-0.01}{\rm M}_{\odot }{\rm yr}^{-1}$|⁠. [ABSTRACT FROM AUTHOR]

We present results of a study to quantify the effects of dust on the derived photometric parameters of disk and bulges obtained from bulge-disk decomposition: scale-length, effective radius, Sérsic index, disk axis-ratio, and bulge-to-disk ratio. The dust induced changes in these parameters were obtained by fitting simulated images of composite systems (containing a disk and a bulge) produced using radiative transfer calculations. The simulations were fitted with the GALFIT 3.0.2 data analysis algorithm. Fits were done with both a combination of an exponential plus a variable-index Sérsic function as well as with a combination of two variable-index Sérsic functions. We find that dust is biasing the derived exponential scale-length of decomposed disks towards smaller values than would be otherwise derived if the galaxy were to have no bulge. Similarly, the derived bulge-to-disk ratio is biased towards smaller values. However, the derived axis-ratio of the disk is not changed in the decomposition process. The derived effective radius of decomposed disks of systems having exponential bulges is found to be less affected by dust when fits are done with two variable-index Sérsic functions. For the same type of fits dust is found to bias the value of the derived effective radius of decomposed disks towards lower values for systems having de Vaucouleurs bulges. [ABSTRACT FROM AUTHOR]

Present and past gas-fuelling of galaxies is expected to depend upon both the properties of the galaxies themselves, as well as their larger-scale environments. In the case of galaxies in groups the environment, i.e the group mass, can be probed by measuring the velocity dispersion of the group members, as done with the GAMA Galaxy Group catalogue (Robotham et al. 2011), probing the halo mass function all the way to small groups. The gas-fuelling rate of normal late-type galaxies can be traced by the SFR under the assumption of a steady state between gas-fuelling and gas-consumption by SF. We present a method to estimate disk opacities from UV/optical photometric characteristics, calibrated using the radiative transfer model of Popescu et al. (2011), applied to UV-Opt-FIR GAMA/H-ATLAS photometry for a subset of GAMA galaxies. We use the method to extract attenuation corrected SFRs for a large sample of late-type GAMA galaxies, which we use in an initial application to constrain the dependency of star formation/gas-fuelling in late-type galaxies on mass of parent DMH, and compactness of galaxy group. [ABSTRACT FROM PUBLISHER]

Based on our sample of 10 095 galaxies with bulge–disc decompositions we derive the empirical -band internal attenuation–inclination relation for galaxy discs and their associated central bulges. Our results agree well with the independently derived dust models of Tuffs et al., leading to a direct constraint on the mean opacity of spiral discs of (central face-on -band opacity). Depending on inclination, the -band attenuation correction varies from 0.2 to 1.1 mag for discs and from 0.8 to 2.6 mag for bulges. We find that, overall, 37 per cent of all -band photons produced in discs in the nearby Universe are absorbed by dust, a figure that rises to 71 per cent for bulge photons. The severity of internal dust extinction is such that one must incorporate internal dust corrections in all optical studies of large galaxy samples. This is particularly pertinent for optical Hubble Space Telescope comparative evolutionary studies as the dust properties will also be evolving. We use the new results to revise our recent estimates of the spheroid and disc luminosity functions. The implied stellar mass densities at redshift zero are somewhat higher than our earlier estimates: and . From our best-fitting dust models we derive a redshift zero cosmic dust density of . This implies that per cent of the baryons in the Universe are in the form of dust and per cent (Salpeter-‘lite’ initial mass function) are in the form of stars (∼58 per cent reside in galaxy discs, ∼10 per cent in red elliptical galaxies, ∼29 per cent in classical galaxy bulges and the remainder in low-luminosity blue spheroid systems/components). [ABSTRACT FROM AUTHOR]

We have carried out a detailed modeling of the dust Spectral Energy Distribution (SED) of the nearby, starbursting dwarf galaxy NGC 4214. A key point of our modeling is that we distinguish the emission from (i) HII regions and their associated photodissociation regions (PDRs) and (ii) diffuse dust. For both components we apply templates from the literature calculated with a realistic geometry and including radiation transfer. The large amount of existing data from the ultraviolet (UV) to the radio allows the direct measurement of most of the input parameters of the models. We achieve a good fit for the total dust SED of NGC 4214. In the present contribution we describe the available data, the data reduction and the determination of the model parameters, whereas a description of the general outline of our work is presented in the contribution of Lisenfeld et al. in this volume. [ABSTRACT FROM PUBLISHER]

A major difficulty hampering the accuracy of UV/optical star formation rate tracers is the effect of interstellar dust, absorbing and scattering light produced by both young and old stellar populations (SPs). Although empirically calibrated corrections or energy balance SED fitting are often used for fast de-reddening of galaxy stellar emission, eventually only radiative transfer calculations can provide self-consistent predictions of galaxy model spectra, taking into account important factors such as galaxy inclination, different morphological components, non-local heating of the dust and scattered radiation. In addition, dust radiative transfer can be used to determine the fraction of monochromatic dust emission powered by either young or old SPs. This calculation needs to take into account the different response of the dust grains to the UV and optical radiation field, depending on the grain size and composition. We determined the dust heating fractions, on both global and local scales, for a high-resolution galaxy model by using our 3D ray-tracing dust radiative transfer code “DART-Ray”. We show the results obtained using this method and discuss the consequences for star formation rate indicators. [ABSTRACT FROM PUBLISHER]