Far-Infrared Emission from Dust in the ISOPHOT Virgo Cluster Deep Sample

We review the characteristics of the dust continuum emission from normal galaxies, as revealed by the ISOPHOT Virgo Cluster Deep Survey (Tuffs et al. 2002; Popescu et al. 2002, Popescu & Tuffs 2002b).Comment: 5 pages (Latex), 4 included figures (eps and ps); selected topics from the invited talk held at the Ringberg Workshop on the Virgo Cluster, 14-17 June 200

Modelling the spectral energy distribution of galaxies from the ultraviolet to submillimeter

We present results from a new modelling technique which can account for the observed optical/NIR - FIR/submm spectral energy distributions (SEDs) of normal star-forming galaxies in terms of a minimum number of essential parameters specifying the star-formation history and geometrical distribution of stars and dust. The model utilises resolved optical/NIR images to constrain the old stellar population and associated dust, and geometry-sensitive colour information in the FIR/submm to constrain the spatial distributions of young stars and associated dust. It is successfully applied to the edge-on spirals NGC891 and NGC5907. In both cases the young stellar population powers the bulk of the FIR/sub-mm emission. The model also accounts for the observed surface brightness distribution and large-scale radial brightness profiles in NGC891 as determined using the Infrared Space Observatory (ISO) at 170 and 200 mcrions and at 850 micron using SCUBA.Comment: 20 pages (Latex), Highlight talk at the Joint European and National Astronomical Meeting JENAM 2001, to be published in Reviews in Modern Astronomy 15: Five Days of Creation: Astronomy with Large Telescopes from Ground and Base. Germany : Astronomische Gesellschaft, 200

Normal Nearby Galaxies

Following on from IRAS, ISO has provided a huge advancement in our knowledge of the phenomenology of the infrared (IR) emission of normal galaxies and the underlying physical processes. Highlights include: the discovery of an extended cold dust emission component, present in all types of gas-rich galaxies and carrying the bulk of the dust luminosity; the definitive characterisation of the spectral energy distribution in the IR, revealing the channels through which stars power the IR light; the derivation of realistic geometries for stars and dust from ISO imaging; the discovery of cold dust associated with HI extending beyond the optical body of galaxies; the remarkable similarity of the near-IR (NIR)/ mid-IR (MIR) SEDs for spiral galaxies, revealing the importance of the photo-dissociation regions in the energy budget for that wavelength range; the importance of the emission from the central regions in shaping up the intensity and the colour of the global MIR luminosity; the discovery of the ``hot'' NIR continuum emission component of interstellar dust; the predominance of the diffuse cold neutral medium as the origin for the main interstellar cooling line, [CII] 158 micron, in normal galaxies.Comment: 47 pages, 15 figures, to be published in the ISO Special Issue of Space Science Reviews: "ISO science legacy - a compact review of ISO major achievements", Springer 2005. See http://www.iso.vilspa.esa.es/science/SSR/ for a higher resolution version and for all papers in the volum

Normal Gas-Rich Galaxies in the Far-Infrared: The Legacy of ISOPHOT

Following on from IRAS, the ISOPHOT instrument on board the Infrared Space Observatory (ISO) has provided a huge advancement in our knowledge of the phenomenology of the far-infrared (FIR) emission of normal galaxies and the underlying physical processes. Highlights include: the discovery of an extended cold dust emission component, present in all types of gas-rich galaxies and carrying the bulk of the dust luminosity; the definitive characterisation of the spectral energy distribution in the FIR, revealing the channels through which stars power the FIR light; the derivation of realistic geometries for stars and dust from ISOPHOT imaging and the discovery of cold dust associated with HI extending beyond the optical body of galaxies.Comment: Invited review presented at "The Spectral Energy Distribution of Gas-Rich Galaxies: Confronting Models with Data", Heidelberg, 4-8 Oct. 2004 (to be published in AIP Conf. Ser.); for a version with full resolution figures go to http://edoc.mpg.de/207563.

Dust effects on the derived Sersic indexes of disks and bulges in spiral galaxies

We present a theoretical study that quantifies the effect of dust on the derived Sersic indexes of disks and bulges. The changes in the derived parameters from their intrinsic values (as seen in the absence of dust) were obtained by fitting Sersic distributions on simulated images of disks and bulges produced using radiative transfer calculations and the model of Popescu et al. 2011. We found that dust has the effect of lowering the measured Sersic index in most cases, with stronger effects for disks and bulges seen through more optically thick lines of sight.Comment: 3 pages, 2 figures, to appear in the Proceedings of the IAU Symposium No.284, "The Spectral Energy Distribution of Galaxies", 5-9 sept. 2011, editors Richard J. Tuffs and Cristina C. Popesc

Far-infrared Emission from Dust in Normal Galaxies

We review the morphological and spectral energy distribution characteristics of the dust continuum emission (emitted in the 40-200 micron spectral range) from normal galaxies, as revealed by detailed ISOPHOT mapping observations of nearby spirals and by ISOPHOT observations of the integrated emissions from representative statistical samples in the local universe.Comment: 7 pages with 5 figures included (eps format); invited review talk held at the ESA Workshop ``Exploiting the ISO Data Archive. Infrared Astronomy in the Internet Age'', Siguenza, Spain 24-27 June, 200

The percentage of stellar light re-radiated by dust in late-type Virgo Cluster galaxies

We show that the mean percentage of stellar light re-radiated by dust is ~30 percent for the Virgo Cluster late-spirals measured with ISOPHOT by Tuffs et al. (2002). A strong dependence of this ratio with morphological type was found, ranging from typical values of ~15 percent for early spirals to up to ~50 percent for some late spirals. The extreme BCDs can have even higher percentages of their bolometric output re-radiated in the thermal infrared. Luminosity correction factors for the cold dust component are given for general use in converting far-infrared (FIR) luminosities derived from IRAS.Comment: 5 pages, 3 eps figures, accepted for publication in MNRAS Letter

A radiative transfer model for the spiral galaxy M33

We present the first radiative transfer (RT) model of a non-edge-on disk galaxy in which the large-scale geometry of stars and dust is self-consistently derived through fitting of multiwavelength imaging observations from the UV to the submm. To this end we used the axi-symmetric 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% in the profiles of surface brightness and within 8% 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±8% 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 define 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 SFR=0.28+0.02−0.01M⊙yr−1