Browsing by Author "Gordon, K. D."

Now showing 1 - 2 of 2
  • No Thumbnail Available
    Item
    Comprehensive comparison of models for spectral energy distributions from 0.1 μm to 1mm of nearby star-forming galaxies
    (2019) Hunt, L. K.; De Looze, I; Boquien, M.; Nikutta, R.; Rossi, A.; Bianchil, S.; Dale, D. A.; Granato, G. L.; Kennicutt, R. C.; Silva, L.; Ciesla, L.; Relano, M.; Viaene, S.; Brandl, B.; Calzetti, D.; Croxall, K., V; Draine, B. T.; Galametz, M.; Gordon, K. D.; Groves, B. A.; Helou, G.; Herrera-Camus, R.; Hinz, J. L.; Koda, J.; Salim, S.; Sandstrom, K. M.; Smith, J. D.; Wilson, C. D.; Zibetti, S.
    We have fit the far-ultraviolet (FUV) to sub-millimeter (850 mu m) spectral energy distributions (SEDs) of the 61 galaxies from the Key Insights on Nearby Galaxies: A Far-Infrared Survey with Herschel (KINGFISH). The fitting has been performed using three models: the Code for Investigating GALaxy Evolution (CIGALE), the GRAphite-SILicate approach (GRASIL), and the Multiwavelength Analysis of Galaxy PHYSical properties (MAGPHYS). We have analyzed the results of the three codes in terms of the SED shapes, and by comparing the derived quantities with simple "recipes" for stellar mass (M-star), star-formation rate (SFR), dust mass (M-dust), and monochromatic luminosities. Although the algorithms rely on different assumptions for star-formation history, dust attenuation and dust reprocessing, they all well approximate the observed SEDs and are in generally good agreement for the associated quantities. However, the three codes show very different behavior in the mid-infrared regime: in the 5-10 mu m region dominated by PAH emission, and also between 25 and 70 mu m where there are no observational constraints for the KINGFISH sample. We find that different algorithms give discordant SFR estimates for galaxies with low specific SFR, and that the standard recipes for calculating FUV absorption overestimate the extinction compared to the SED-fitting results. Results also suggest that assuming a "standard" constant stellar mass-to-light ratio overestimates Mstar relative to the SED fitting, and we provide new SED-based formulations for estimating Mstar from WISE W1 (3.4 mu m) luminosities and colors. From a principal component analysis of M-star, SFR, M-dust, and O/H, we reproduce previous scaling relations among Mstar, SFR, and O/H, and find that Mdust can be predicted to within similar to 0.3 dex using only M-star and SFR.
  • No Thumbnail Available
    Item
    Metallicity effects on dust properties in starbursting galaxies
    (2008) Engelbracht, C. W.; Rieke, G. H.; Gordon, K. D.; Smith, J. -D. T.; Werner, M. W.; Moustakas, J.; Willmer, C. N. A.; Vanzi, L.
    We present infrared observations of 66 starburst galaxies over the full range of oxygen abundances observed in local star-forming galaxies, from 12 + log(O/H) = 7.1 to 8.9. The data include imaging and spectroscopy from the Spitzer Space Telescope, supplemented by ground-based near-infrared imaging. We confirm a strong correlation of aromatic emission with metallicity, with a threshold at 12 + log(O/H) similar to 8. We show that the far-infrared color temperature of the large dust grains increases toward lower metallicity, peaking at a metallicity of 8 before turning over. We compute dust masses and compare them to H I masses from the literature to derive the ratio of atomic gas to dust, which increases by nearly 3 orders of magnitude between solar metallicity and a metallicity of 8, below which it flattens out. The abrupt change in aromatic emission at mid-infrared wavelengths thus appears to be reflected in the far-infrared properties, indicating that metallicity changes affect the composition of the full range of dust grain sizes that dominate the infrared emission. Although the great majority of galaxies show similar patterns of behavior as described above, there are three exceptions, SBS 0335-052E, Haro 11, and SHOC 391. Their infrared SEDs are dominated energetically by the mid-IR near 24 mu m rather than by the 60-200 mu m region. In addition, they have very weak near-infrared outputs and their SEDs are dominated by emission by dust at wavelengths as short as 1.8 mu m. The latter behavior indicates that the dominant star-forming episodes in them are extremely young. The component of the ISM responsible for the usual far-infrared emission appears to be either missing or inefficiently heated in these three galaxies.