The Local Volume Legacy (LVL) is a Spitzer Cycle 4 IRAC and MIPS survey of a complete sample of 258 galaxies within 11 Mpc. The broad goal of LVL is to provide critical insight into two of the primary processes that shape the growth of galaxies: star formation and its interaction with the interstellar medium. This goal will be achieved by investigating the spatially-resolved star formation, dust, and red stellar populations of galaxies that have been drawn from a statistically robust local sample, in which a full diversity of galaxy properties (e.g., luminosities, surface brightnesses, metallicities) are represented. The LVL sample includes:
(i) all known galaxies inside a sub-volume bounded by 3.5 Mpc; and
(ii) an unbiased sample of S-Irr galaxies within the larger, more representative, 11 Mpc volume.
LVL has produced a multi-wavelength census of the Galactic neighborhood, extending to the faintest limits of the galactic luminosity function and exploiting the highest spatial resolution and absolute depth achievable with Spitzer. By combining Spitzer imaging with a range of ancillary data, LVL has assembled a core dataset on star formation and dust, with information on:
(i) the current star formation rate (SFR) from Hα emission, produced by the recombination of gas ionized by the most massive, short-lived OB stars (Kennicutt et al. 2008);
(ii) the SFR averaged over a longer 100 Myr timescale, from the non-ionizing ultraviolet continuum originating in the photospheres of O- through late-type B-stars Lee et al. 2009, 2011);
(iii) the stellar mass, constrained by 3.6 to 4.5 microns luminosities, which are generally dominated by the light from old stellar populations (Johnson et al. in prep); and
(iv) dust content, from both the strength and shape of the infrared emission, which represents the stellar light that has been absorbed and re-radiated by dust (Dale et al. 2009).
A catalog of optical broad-band photometry, important for constraining the overall star formation histories of the galaxies, is also being produced (van Zee et al. in preparation). LVL has made most of this dataset publically available to the community. Information on how to access the data can be found by clicking on the data products link on the sidebar, or through the LVL portal at the NASA/IPAC Infrared Science Archive.
Principal science issues addressed by the LVL team include: constraining the physical mechanisms underlying dust heating and understanding correlations between FIR emission, dust content and global galaxy properties; establishing the primary factors which influence PAH emission and evaluating the robustness of PAH emission as a SFR indicator, particularly at low metallicities and high specific SFRs; probing the temporal variation of star formation as a function of global properties, with special focus on dwarf galaxies.
The montage of images below show the ensemble of galaxies as observed by Spitzer. Click the images to obtain higher resolution versions (29MB and 17 MB) and see here for more information.
Last updated 2011 February.