2009AJ....137.4670L

We present the Heterodyne Receiver Array CO Line Extragalactic Survey, an atlas of CO emission from 18 nearby galaxies that are also part of The H I Nearby Galaxy Survey and the Spitzer Infrared Nearby Galaxies Survey. We used the HERA multipixel receiver on the IRAM 30-m telescope to map the CO J = 2 {x2192} 1 line over the full optical disk (defined by the isophotal radius r₂₅) of each target, at 13'' angular resolution and 2.6 km/s velocity resolution. Here we describe the observations and reduction of the data and show channel maps, azimuthally averaged profiles, integrated intensity maps, and peak intensity maps. The implied H₂ masses range from 7x10⁶ to 6x10⁹ M_☉, with four low metallicity dwarf irregular galaxies yielding only upper limits. In the cases where CO is detected, the integrated H₂-to-H I ratios range from 0.02 to 1.13 and H₂-to-stellar mass ratios from 0.01 to 0.25. Exponential scale lengths of the CO emission for our targets are in the range 0.8-3.2 kpc, or 0.2±0.05r₂₅. The intensity-weighted mean velocity of CO matches that of H I very well, with a 1σ scatter of only 6 km/s. The CO J = 2 {x2192} 1/J = 1 {x2192} 0 line ratio varies over a range similar to that found in the Milky Way and other nearby galaxies, ∼0.6-1.0, with higher values found in the centers of galaxies. The typical line ratio, ∼0.8, could be produced by optically thick gas with an excitation temperature of ∼10 K.