In this work, we computed the distances to three molecular clouds in the central molecular zone (CMZ), the 50 kms-1 , 20 kms-1, and the Brick clouds, and investigated their CMZ membership. We used the colour magnitude diagrams Ks versus H−Ks to compare stars detected towards the target clouds with stars detected towards three reference regions in the nuclear stellar disc (NSD) and the Galactic bulge. We used red clump (RC) stars to estimate the distance to each region.
We found that all the clouds present a double RC feature. Such a double RC has been reported in previous work for the NSD, but not for the bulge adjacent to it. We exclude the possibility that the different RC features are located at significantly different distances. The obtained absolute and relative distances are compatible with the Galactic centre distance (∼8 kpc).