HCO⁺ in the disk of AB Aur

 HCO⁺(J=1-0) emission was detected with the Plateau de Bure Interferometer towards the known disk around the Herbig Ae star AB Aurigae. The morphology of the disk and the shape of the spectra are similar to the ¹³CO measurements by Mannings and Sargent (1997, ApJ 490, 792). However, the spectra are much better resolved. The map of the integrated HCO⁺(J=1-0) line (left: green contours; levels 0.05 to 0.25 by 0.05 Jy/beam) is overlaid with the NICMOS image by Grady et al. (1999, ApJ 523, L151). Three spectra are displayed on the right. At the top, the integrated spectrum over the region inside the 0.15 Jy/beam contour level is shown. The positions of spectra in the middle and at the bottom are marked with an arrow. The strong variation of the HCO⁺ line profiles over the disk area is caused by the rotation of the gas disk.

More details you can find in "Millimeter Observations and Modeling of the AB Aurigae System" (Semenov, Pavlyuchenkov, Schreyer et al. 2005, ApJ 621, p. 853).