Continuum images and N₂H⁺ 3 − 2 integrated intensity maps and spectra. First row: intensity maps of the 284 GHz dust continuum. Contours are drawn at [5, 10, 20, 40, 80, 160...]σ, where σ is the rms listed in Table 3. Note the continuum substructure in the LkCa 15, GM Aur, DM Tau, and AS 209 disks. Second row: integrated intensity maps of N₂H⁺ 3 − 2. Color bars start at 2σ, where σ is the rms of the integrated intensity map. Synthesized beams are drawn in the lower right corners of each panel. The centroid of the continuum image is marked with a cross. The offset from the centroid, in arcseconds, is marked on the y-axis of the upper left corner panel. The N₂H⁺ maps display a range of morphologies from narrow to broad rings. Third row: spectra of N₂H⁺ 3 − 2 show the double-peaked shape characteristic of a Keplerian rotation disk. Even though there are 29 hyperfine components for the N₂H⁺ 3 − 2 line (see Appendix B), the dominant components spread less than 0.4 km s⁻¹. The vertical red line marks the systemic velocity.