Stacked images for the CO detections (top row) and CO non-detections (bottom row). From left to right, we stacked HST ACS mosaic images in gray scale, HI total intensity (moment 0) maps in blue, and CO maps collapsed over the channels indicated in Figure 5 in orange. In each image the concentric circles represent [2, 4, 6] arcsec radius apertures over which we extracted the CO spectra. Inset in the lower right corresponds to the stacked non-detections, smoothed to 4 arcsec resolution (see text). Consistently across all images, the CO-detected galaxies in the top row appear spatially larger on the sky.

Fig. 5.

Spectra extracted from the [2, 4, 6] arcsec apertures for the CO detections (top) and over the 4 arcsec aperture for the CO non-detections (bottom). Light gray regions indicate channels over which emission is detected and the cubes are collapsed make the CO maps in Figure 4. See text for further details.