Solving the inverse problem in spiral galaxies, that allows the derivation of the spatial distribution of dust, gas and stars, together with their associated physical properties, directly from panchromatic imaging observations, is one of the main goals of this work. To this end we used radiative transfer models to decode the spatial and spectral distribution of the nearby face-on galaxies M101 and NGC 3938. In both cases we provide excellent fits to the surface-brightness distributions derived from GALEX, SDSS, 2MASS, Spitzer and Herschel imaging observations. Together with previous results from M33, NGC 628, M51 and the Milky Way, we obtain a small statistical sample of modelled nearby galaxies that we analyse in this work. We find that in all cases Milky Way-type dust with Draine-like optical properties provide consistent and successful solutions. We do not find any "submm excess", and no need for modified dust-grain properties. Intrinsic fundamental quantities like star-formation rates (SFR), specific SFR (sSFR), dust opacities and attenuations are derived as a function of position in the galaxy and overall trends are discussed. In the SFR surface density versus stellar mass surface density space we find a structurally resolved relation (SRR) for the morphological components of our galaxies, that is steeper than the main sequence (MS). Exception to this is for NGC 628, where the SRR is parallel to the MS.

We work in the physical model of hydrogen-like atoms and use the wave functions provided by solutions of the Schrödinger equation with Coulomb potential. For the hydrogen spectra, we develop a theoretical-spectroscopy method to identify the significant quantum states with the highest probability of transition. We exemplify this method for the α, β, γ Lyman transitions, namely for a fixed principal quantum number n less than 5, and find (2 1 0), (3 2 0), (4 3 0) as significant quantum states. Besides this, we obtain other various results: the numerical tables for the radial distributions and the electron density functions, and some observables like θ nodal angles, nodal surfaces, along with the ordered sequences of the average-radii of the sub-shells for a fixed n , such as: 18 a =〈r〉 < 〈r〉 < 〈r〉 <〈r〉 = 24 a (for the shell n = 4 and a - the first Bohr radius). Afterwards, we build the scientific 3D-visualization of the orbitals shapes and describe them via the nodal values for θ angles.

Using the quantum model of the hydrogen-type atom, we compute the wave-functions and the expressions of Dirac energy both in Bohr approxi-mation as well as in fine structure approximation. Based on this quantum model (QM), we identify some special quantum states called maximum lo-calization sub-shells. Then, we present numerical values of the radial dis-tributions and the electron density functions, as well as the average radii ordered sequences of sub-shells. Analyzing the NIST atomic database, we observe that the transition between these special quantum states explains the occurrence of the maximum relative intensity line of the corresponding fine structure multiplet. Thus, using NIST database, the QM-results are vali-dated for the a-Lyman, a-Balmer, .., and a-Pfund spectral H-lines in fine structure approximation.

In the quantum frame and dipole approximation for the Hydrogen atom, the paper provides a spectral model (QS-Model) based on the concept of the multipletpeaks and also on the theorems of multiplets (BMT). These theorems show the transitions and their associated peaks in their multiplets. On the other hand, in this model, starting from the expression of energy levels of atomic structure in Dirac's theory, the wavelengths of multipletpeaks in fine structure-approximation (fs-apx) are calculated. Based on the available NIST-data for the first five spectral series, the QS-Model is validated. This validation contains an observed-computed (O-C) type-analysis during which the improving-problem of the data for Balmer to Pfund series is examined. We give an analytical method and calculate the proportionality factor equivalent to the Rydberg constant in this model.

ABSTRACT 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 We present an analysis of archival Spitzer InfraRed Spectrograph (IRS) observations of the recurrent nova RS Ophiuchi obtained on several occasions, beginning about 7 months after the outburst in 2006. These data show atomic emission lines, absorption bands due to photospheric SiO, and the well-known silicate dust features at 9.7 and $18\, \mu$m. The dust emission, arising in the wind of the secondary star, is fitted by dusty models for mass-loss rates in the range 1.0–1.7 × 10−7 M⊙ yr−1. The silicate features are similar in profile to those seen in circumstellar environments of isolated late-type stars and some dusty symbiotic binaries, although the longer wavelength feature peaks at $17\, \mu$m, instead of the usual $18\, \mu$m, indicating peculiar grain properties. The dust features are variable, appearing stronger in 2006–2007 during outburst than in 2008–2009 when the system was in the quiescent state. This variability is attributed to changes in the ultraviolet output and the reformation of the accretion disc, although a decline in the mass-loss rate of the red giant secondary star could also play a role. Further observations, in the aftermath of the 2021 eruption, could provide a definitive conclusion.

We present an axi-symmetric model for the ultraviolet (UV)-to-submillimetre (submm) images of the nearly face-on spiral galaxy NGC 628. It was calculated using a radiative transfer (RT) code, accounting for the absorption and re-emission of starlight by dust in the interstellar medium of this galaxy. The code incorporates emission from Polycyclic Aromatic Hydrocarbons, anisotropic scattering, and stochastic heating of the grains. This is the second successful modelling of a face-on spiral galaxy with RT methods, whereby the large-scale geometry of stars and dust is self-consistently determined. The solution was obtained by fitting azimuthally averaged profiles in the UV, optical, and submm. The model predicts remarkably well all characteristics of the profiles, including the increase by a factor of 1.8 of the scale length of the infrared emissivity between 70 and 500 mu m. We find that NGC 628 did not undergo an efficient inside-out disc growth, as predicted by semi-analytical hierarchical models for galaxy formation. We also find large amounts of dust grains at large radii, which could involve efficient transport mechanisms from the inner disc. Our results show that 71 per cent of the dust emission in NGC 628 is powered by the young stellar populations, with the old stellar populations from the bulge contributing 65 per cent to the heating of the dust in the central region (R < 0.5 kpc). The derived star formation rate is SFR = 2.00 +/- 0.15 M-circle dot yr(-1) .

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 SFR = 1.25 +/- 0.2M(circle dot) yr(-1), a stellar mass M-* = (4.9 +/- 0.3) x 10(10) M-circle dot, 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(s)(disc) (K) = 2.2 +/- 0.6 kpc in the NIR, to h(s)(disc) (B) = 3.2 +/- 0.9 kpc at the shorter optical bands, and a scale height that varies with radial distance, from z(s)(disc) (0) = 140 +/- 20 pc in the centre to z(s)(disc) (R-circle dot) = 300 +/- 20 pc at the solar radius. The young stellar populations have a scale length of h(s)(tdisc) = 3.2 +/- 0.9 kpc and a scale height that varies from z(s)(tdisc) (0) = 50 +/- 10 pc in the centre to z(s)(disc) (R-circle dot) = 90 +/- 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(d)(disc) = 5.2 +/- 0.8 kpc and scale height z(d)(disc) = 0.14 +/- 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 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 ${\rm SFR}=0.28^{+0.02}_{-0.01}{\rm M}_{\odot }{\rm yr}^{-1}$.

We present infrared spectroscopy of the classical nova V339 Del, obtained over an similar to 2-yr period. The infrared emission lines were initially symmetrical, with half width half-maximum velocities of 525 km s(-1). In later (t greater than or similar to 77 d, where t is the time from outburst) spectra, however, the lines displayed a distinct asymmetry, with a much stronger blue wing, possibly due to obscuration of the receding component by dust. Dust formation commenced at approximately day 34.75 at a condensation temperature of 1480 +/- 20 K, consistent with graphitic carbon. Thereafter, the dust temperature declined with time as T-d alpha t(-0.346), also consistent with graphitic carbon. The mass of dust initially rose, as a result of an increase in grain size and/or number, peaked at approximately day 100, and then declined precipitously. This decline was most likely caused by grain shattering due to electrostatic stress after the dust was exposed to X-radiation. The appendix summarizes Planck means for carbon and the determination of grain mass and radius for a carbon dust shell.

Classical novae show a rapid rise in optical brightness over a few hours. Until recently the rise phase, particularly the phenomenon of a pre-maximum halt, was observed sporadically. Solar observation satellites observing Coronal Mass Ejections enable us to observe the pre-maximum phase in unprecedented temporal resolution. We present observations of V5589 Sgr with STEREO HI-1B at a cadence of 40 min, the highest to date. We temporally resolve a pre-maximum halt for the first time, with two examples each rising over 40 min then declining within 80 min. Comparison with a grid of outburst models suggests this double peak, and the overall rise timescale, are consistent with a white dwarf mass, central temperature and accretion rate close to 1.0 solar mass, 5x10^7 K and 10^-10 solar masses per year respectively. The modelling formally predicts mass loss onset at JD 2456038.2391+/-0.0139, 12 hrs before optical maximum. The model assumes a main-sequence donor. Observational evidence is for a subgiant companion; meaning the accretion rate is under-estimated. Post-maximum we see erratic variations commonly associated with much slower novae. Estimating the decline rate difficult, but we place the time to decline two magnitudes as 2.1 < t_2(days) < 3.9 making V5589 Sgr a "very fast" nova. The brightest point defines "day 0" as JD 2456038.8224+/-0.0139, although at this high cadence the meaning of the observed maximum becomes difficult to define. We suggest that such erratic variability normally goes undetected in faster novae due to the low cadence of typical observations; implying erratic behaviour is not necessarily related to the rate of decline.

We present a SOFIA FORCAST grism spectroscopic survey to examine the mineralogy of the circumstellar dust in a sample of post-asymptotic giant branch (post-AGB) yellow supergiants that are believed to be the precursors of planetary nebulae. Our mineralogical model of each star indicates the presence of both carbon-rich and oxygen-rich dust species-contrary to simple dredge-up models-with a majority of the dust in the form of amorphous carbon and graphite. The oxygen-rich dust is primarily in the form of amorphous silicates. The spectra do not exhibit any prominent crystalline silicate emission features. For most of the systems, our analysis suggests that the grains are relatively large and have undergone significant processing, supporting the hypothesis that the dust is confined to a Keplerian disk and that we are viewing the heavily processed, central regions of the disk from a nearly face-on orientation. These results help to determine the physical properties of the post-AGB circumstellar environment and to constrain models of post-AGB mass loss and planetary nebula formation.

We present a solution for the ultraviolet (UV) - submillimeter (submm) interstellar radiation fields (ISRFs) of the Milky Way, derived from modelling COBE, IRAS and Planck maps of the all-sky emission in the near-, mid-, far-infrared and submm.The analysis uses the axisymmetric radiative transfer (RT) model that we have previously implemented to model the panchromatic spectral energy distributions (SEDs) of star forming galaxies in the nearby universe, but with a new methodology allowing for optimisation of the radial and vertical geometry of stellar emissivity and dust opacity, as deduced from the highly resolved emission seen from the vantage point of the Sun. As such, this is the first self-consistent model of the broad-band continuum emission from the Milky Way. In this paper, we present model predictions for the spatially integrated SED of the Milky Way as seen from the Sun, showing good agreement with the data, and give a detailed description of the solutions for the distribution of ISRFs, as well as their physical origin, throughout the volume of the galaxy. We explore how the spatial and spectral distribution of our new predictions for the ISRF in the Milky Way affects the amplitude and spectral distribution of the gamma-rays produced via Inverse Compton scattering for cosmic ray electrons situated at different positions in the galaxy, as well as the attenuation of the gamma-rays due to interactions of the gamma-ray photons with photons of the ISRF. We also compare and contrast our solutions for the ISRF with those incorporated in the GALPROP package used for modelling the high energy emission from cosmic rays in the Milky Way.

We quantify the effect of the galaxy group environment (for group masses of 10(12.5) -10(14.0)M(circle dot)) on the current star formation rate (SFR) of a pure, morphologically selected sample of disk-dominated (i. e., late-type spiral) galaxies with redshift <= 0.13. The sample embraces a full representation of quiescent and star-forming disks with stellar mass M-* >= 10(9.5)M(circle dot). We focus on the effects on SFR of interactions between grouped galaxies and the putative intrahalo medium (IHM) of their host group dark matter halos, isolating these effects from those induced through galaxy-galaxy interactions, and utilizing a radiation transfer analysis to remove the inclination dependence of derived SFRs. The dependence of SFR on M-* is controlled for by measuring offsets.log(Psi(*)) of grouped galaxies about a single power-law relation in specific SFR, Psi(*) proportional to M-* (0.45 +/- 0.01), exhibited by non-grouped " field" galaxies in the sample. While a small minority of the group satellites are strongly quenched, the group centrals and a large majority of satellites exhibit levels of Psi(*) statistically indistinguishable from their field counterparts, for all M-*, albeit with a higher scatter of 0.44 dex about the field reference relation (versus 0.27 dex for the field). Modeling the distributions in Delta log(Psi(*)), we find that (i) after infall into groups, disk-dominated galaxies continue to be characterized by a similar rapid cycling of gas into and out of their interstellar medium shown prior to infall, with inflows and outflows of similar to 1.5-5 xSFR and similar to 1-4 x SFR, respectively; and (ii) the independence of the continuity of these gas flow cycles on M-* appears inconsistent with the required fueling being sourced from gas in the circumgalactic medium on scales of similar to 100 kpc. Instead, our data favor ongoing fueling of satellites from the IHM of the host group halo on similar to Mpc scales, i. e., from gas not initially associated with the galaxies upon infall. Consequently, the color-density relation of the galaxy population as a whole would appear to be primarily due to a change in the mix of disk-and spheroid-dominated morphologies in the denser group environment compared to the field, rather than to a reduced propensity of the IHM in higher-mass structures to cool and accrete onto galaxies. We also suggest that the required substantial accretion of IHM gas by satellite disk-dominated galaxies will lead to a progressive reduction in the specific angular momentum of these systems, thereby representing an efficient secular mechanism to transform morphology from star-forming disk-dominated types to more passive spheroid-dominated types.

We present an extensively updated version of the purely ray-tracing 3D dust radiation transfer code DART-Ray. The new version includes five major upgrades: 1) a series of optimizations for the ray-angular density and the scattered radiation source function; 2) the implementation of several data and task parallelizations using hybrid MPI + OpenMP schemes; 3) the inclusion of dust self-heating; 4) the ability to produce surface brightness maps for observers within the models in HEALPix format; 5) the possibility to set the expected numerical accuracy already at the start of the calculation. We tested the updated code with benchmark models where the dust self-heating is not negligible. Furthermore, we performed a study of the extent of the source influence volumes, using galaxy models, which are critical in determining the efficiency of the DART-Ray algorithm. The new code is publicly available, documented for both users and developers, and accompanied by several programmes to create input grids for different model geometries and to import the results of N-body and SPH simulations. These programmes can be easily adapted to different input geometries, and for different dust models or stellar emission libraries.

We present an analysis of optical and infrared spectra of the recurrent nova RS Oph obtained during between 2006 and 2009. The best fit to the optical spectrum for 2006 September 28 gives T-eff = 3900 K for log g = 2.0, while for log g = 0.0 we find T-eff = 4700 K, and a comparison with template stellar spectra provides T-eff similar to 4500 K. The observed spectral energy distribution ( SED), and the intensities of the emission lines, vary on short ( less than or similar to 1 d) time-scales, due to disc variability. We invoke a simple one-component model for the accretion disc, and a model with a hot boundary layer, with high (similar to 3.9 x 10(-6) M circle dot yr(-1)) and low (similar to 2 x 10(- 8) M circle dot yr(--1)) accretion rates, respectively. Fits to the accretion disc- extracted infrared spectrum (2008 July 15) yield effective temperatures for the red giant of T-eff = 3800 +/- 100 K ( log g = 2.0) and T-eff = 3700 +/- 100 K ( log g = 0.0). Furthermore, using a more sophisticated approach, we reproduced the optical and infrared SEDs of the red giant in the RS Oph system with a twocomponent model atmosphere, in which 90 per cent of the surface has T-eff = 3600 K and 10 per cent has T-eff = 5000 K. Such structure could be due to irradiation of the red giant by the white dwarf.