2002A&A...382..573F

The inner three arcminutes surrounding the Class 0/1 binary protostar L1551 IRS5 have been observed using the J=1->0 transitions of the HCO⁺, H¹³CO⁺, ¹²CO and ¹³CO molecular species. Since the line core of HCO⁺ is self reversed over a substantial part of our map, observations of isotopomers such as H¹³CO⁺ are required in order to estimate the mass of the molecular gas in the immediate vicinity of IRS5. Our observations demonstrate the presence of a large (∼7000AU radius) dense, possibly rotating, molecular disk with a mass of a few M_☉ oriented perpendicular to the major axis of an extended molecular outflow. The disk is surrounded by an envelope with a radius of ∼10000AU that contains two massive (each ∼1M_☉) clumps. One of these features appears to be kinematically disconnected from both the disk and the molecular outflow.