ISOCAM observations of the L1551 star formation region

. The results of a deep mid-IR ISOCAM survey of the L1551 dark molecular cloud are presented. The aim of this survey is a search for new YSO (Young Stellar Object) candidates, using two broad-band filters centred at 6.7 and 14.3 µ m. Although two regions close to the centre of L1551 had to be avoided due to saturation problems, 96 sources were detected in total (76 sources at 6.7 µ m and 44 sources at 14.3 µ m). Using the 24 sources detected in both filters, 14 were found to have intrinsic mid-IR excess at 14.3 µ m and were therefore classified as YSO candidates. Using additional observations in B , V , I , J , H and K obtained from the ground, most candidates detected at these wavelengths were confirmed to have mid-IR excess at 6.7 µ m as well, and three additional YSO candidates were found. Prior to this survey only three YSOs were known in the observed region (avoiding L1551 IRS5 / NE and HL / XZTau). This survey reveals 15 new YSO candidates, although several of these are uncertain due to their extended nature either in the mid-IR or in the optical / near-IR observations. Two of the sources with mid-IR excess are previously known YSOs, one is a brown dwarf (MHO5) and the other is the well known T Tauri star HH30, consisting of an outflow and an optically thick disk seen edge on.