Sample

The LITTLE THINGS sample includes 42 dwarf irregular (dIm) and Blue Compact Dwarf (BCD) galaxies. We obtained new VLA HI-line observations of 21 galaxies; the other 21 have data in the NRAO archives. (However, NGC 1156 was dropped from our sample because the archival observations did not have any line-free channels for determining continuum. Also, we obtained data on NGC 6822, but there is a zero-spacing issue and no maps are available with these data.) The galaxies are listed in Table 1 and the datasets in Table 2. The LITTLE THINGS sample was drawn from a larger multi-wavelength survey that includes 94 dIm, 24 BCDs, and 18 Sm galaxies (Hunter & Elmegreen 2004, 2006), the result of 15 years of observations. The HI sample covers a large range of dIm parameter space of the full survey (see Figure 1), including the extremes---from high star formation rate BCDs to low surface brightness dwarfs without any current star formation. Distances have been updated from those used by Hunter & Elmegreen (2004, 2006), and references for the new distances used here are given by Hunter et al. (in preparation).

^aR_H is the Holmberg radius, the radius of the galaxy at a B-band isophote, corrected for reddening, of 26.7 mag of one arcsec².

^bSFR_D is the star formation rate, measured from Halpha, normalized to the pi×R_D², where R_D is the disk scale length measured from V-band images. A galaxy without any detectable Halpha emission is listed as having a SFR of 0.

References for published datasets: Halpha images (Hunter & Elmegreen 2004); UBVJHK images (Hunter & Elmegreen 2006); Spitzer IRAC images (Hunter, Elmegreen, & Martin 2006); Spitzer IRS spectra (Hunter & Kaufman 2006, AJ, submitted); individual HI studies (Hunter, Elmegreen, & van Woerden 2001; Simpson, Hunter, & Knezek 2005; Simpson, Hunter, & Nordgren 2005; Kepley, Wilcots, Hunter, & Nordgren 2007).

Figure 1: Properties of the LITTLE THINGS HI sample (new observations [hashed +45° ]+archive [hashed -45°]) compared to the entire optical survey (open) of Hunter & Elmegreen (2004, 2006). The HI sample covers the range of parameters of the full survey. dIm and BCD galaxies have been combined. A star formation rate (SFR) of 0 is plotted as a log of -6. SFR_D is the SFR normalized to pi×R_D², where R_D is the disk scale length.