The Spitzer Local Volume Legacy: Survey Description and Infrared Photometry

Creators: Dale, D. A.; Cohen, S. A.; Johnson, L. C.; Schuster, M. D.; Calzetti, D.; Engelbracht, C. W.; Gil de Paz, A.; Kennicutt, R. C.; Lee, J. C.; Begum, A.; Block, M.; Dalcanton, J. J.; Funes, J. G.; Gordon, K. D.; Johnson, B. D.; Marble, A. R.; Sakai, S.; Skillman, E. D.; van Zee, L.; Walter, F.; Weisz, D. R.; Williams, B.; Wu, S.-Y.; Wu, Y.

Abstract

The survey description and the near-, mid-, and far-infrared flux properties are presented for the 258 galaxies in the Local Volume Legacy (LVL). LVL is a Spitzer Space Telescope legacy program that surveys the local universe out to 11 Mpc, built upon a foundation of ultraviolet, Hα, and Hubble Space Telescope imaging from 11HUGS (11 Mpc Hα and Ultraviolet Galaxy Survey) and ANGST (ACS Nearby Galaxy Survey Treasury). LVL covers an unbiased, representative, and statistically robust sample of nearby star-forming galaxies, exploiting the highest extragalactic spatial resolution achievable with Spitzer. As a result of its approximately volume-limited nature, LVL augments previous Spitzer observations of present-day galaxies with improved sampling of the low-luminosity galaxy population. The collection of LVL galaxies shows a large spread in mid-infrared colors, likely due to the conspicuous deficiency of 8 μm polycyclic aromatic hydrocarbon emission from low-metallicity, low-luminosity galaxies. Conversely, the far-infrared emission tightly tracks the total infrared emission, with a dispersion in their flux ratio of only 0.1 dex. In terms of the relation between the infrared-to-ultraviolet ratio and the ultraviolet spectral slope, the LVL sample shows redder colors and/or lower infrared-to-ultraviolet ratios than starburst galaxies, suggesting that reprocessing by dust is less important in the lower mass systems that dominate the LVL sample. Comparisons with theoretical models suggest that the amplitude of deviations from the relation found for starburst galaxies correlates with the age of the stellar populations that dominate the ultraviolet/optical luminosities.

Additional Information

© 2009 The American Astronomical Society. Received 2009 April 8; accepted 2009 July 21; published 2009 August 28. Support for this work, part of the Spitzer Space Telescope Legacy Science Program, was provided by National Aeronautics and Space Administration (NASA) through contract 1336000 issued by the Jet Propulsion Laboratory, California Institute of Technology under NASA contract 1407. This research has made use of the NASA/IPAC Extragalactic Database, which is operated by JPL/Caltech, under contract with NASA. This publication makes use of data products from the Two-Micron All Sky Survey, which is a joint project of the University of Massachusetts and the Infrared Processing and Analysis Center/California Institute of Technology, funded by NASA and the National Science Foundation. IRAF, the Image Reduction and Analysis Facility, has been developed by the National Optical Astronomy Observatories and the Space Telescope Science Institute. We gratefully acknowledge NASA's support for construction, operation, and science analysis for the GALEX mission, developed in cooperation with the Centre National d'Etudes Spatiales of France and the Korean Ministry of Science and Technology.

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