Ellen Simmat

Max Planck Institute for Nuclear Physics, Heidelburg, Baden-Württemberg, Germany

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Publications (2)5.11 Total impact

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    ABSTRACT: We present self-consistent star formation rates derived through pan-spectral analysis of galaxies drawn from the Galaxy and Mass Assembly (GAMA) survey. We determine the most appropriate form of dust obscuration correction via application of a range of extinction laws drawn from the literature as applied to Halpha, [O{II}] and UV luminosities. These corrections are applied to a sample of 31,508 galaxies from the GAMA survey at z < 0.35. We consider several different obscuration curves, including those of Milky Way, Calzetti (2001) and Fischera and Dopita (2005) curves and their effects on the observed luminosities. At the core of this technique is the observed Balmer decrement, and we provide a prescription to apply optimal obscuration corrections using the Balmer decrement. We carry out an analysis of the star formation history (SFH) using stellar population synthesis tools to investigate the evolutionary history of our sample of galaxies as well as to understand the effects of variation in the Initial Mass Function (IMF) and the effects this has on the evolutionary history of galaxies. We find that the Fischera and Dopita (2005) obscuration curve with an R_{v} value of 4.5 gives the best agreement between the different SFR indicators. The 2200A feature needed to be removed from this curve to obtain complete consistency between all SFR indicators suggesting that this feature may not be common in the average integrated attenuation of galaxy emission. We also find that the UV dust obscuration is strongly dependent on the SFR. Comment: Accepted by MNRAS. 13 pages. 8 figures
    Monthly Notices of the Royal Astronomical Society 09/2010; 410(4). DOI:10.1111/j.1365-2966.2010.17599.x · 5.11 Impact Factor
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    Ellen Simmat · Richard J. Tuffs · Cristina C. Popescu ·
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    ABSTRACT: Highly resolved images of the edge-on galaxy NGC 7814 from 2MASS and Spitzer were used to extract the morphologies and spectral energy distributions (SEDs) of the disk, bulge and halo components of this galaxy over a wavelength range from 1.25 to 24 μm. This represents the first direct determination of the mid-infrared emission of the bulge and halo components of a galaxy other than the Milky Way. The SEDs of all three structures imply the presence of emission components from direct stellar light and from at least one further component. For the disk, this further component is interpreted as dust emission having properties typical of star forming disks. The emission from the bulge and the halo is very significantly in excess of that from an extrapolation of the near infrared emission from stars. This excess has a flat spectrum between 8 and 24 μm bands and has an unknown origin. I discuss potential explanations such as dust emission in an interstellar medium, galactic winds, star forming regions and circumstellar dust, as well as emission from brown dwarfs. Further analysis is needed to test these hypotheses.
    06/2010; 1240. DOI:10.1063/1.3458570