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| Paper: |
Fitting the SEDs of Galaxies in the Local Volume |
| Volume: |
440, UP2010: Have Observations Revealed a Variable Upper End of the Initial Mass Function? |
| Page: |
227 |
| Authors: |
Johnson, B. D. |
| Abstract: |
The distribution of the Hα/UV flux ratio in local, low-luminosity galaxies is suggestive of a varying high-mass end of the Initial Mass Function (IMF), though several additional effects may be responsible. I describe the fitting of population synthesis models with an invariant IMF to the Spectral Energy Distributions of a subset of the Local Volume Legacy (LVL) sample. I pay special attention to the types of star formation histories and dust properties required to match simultaneously the UV and Hα fluxes of these low luminosity galaxies, under the assumption that the IMF does not vary. The observed SEDs to be fit include UV, optical, and IR broadband photometry from GALEX, SDSS, and Spitzer respectively, as well as narrowband Hα photometry from the 11Mpc Survey. Of special importance is the observed thermal Far-IR emission, which places a useful constraint on the dust attenuation. I find that recently ended bursts adequately describe the UV through Far-IR SED of ≲10% of the sample, while the rest, including some galaxies with ‘low' Hα/UV flux ratios, are well fit by a smooth or continuous recent star formation history. I consider the physical properties of local volume galaxies, derived from indicators that are not sensitive to the upper IMF, and find the suggestion of a large spread in specific star formation rate at low stellar mass, possibly indicating a range of long-term star formation history in these galaxies. |
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