Multiple molecular outflows and fragmentation in the IRDC core G34.43+00.24 MM1

Abstract

Context. The fragmentation of a molecular cloud that leads to the formation of high-mass stars occurs on a hierarchy of different spatial scales. The large molecular clouds harbor massive molecular clumps with massive cores embedded in them. The fragmentation of these cores may determine the initial mass function and the masses of the final stars. Therefore, studying the fragmentation processes in the cores is crucial to understanding how massive stars form. Aims. Detailed studies toward particular objects are needed to collect observational evidence that shed light on star formation processes on the smallest spatial scales. The hot molecular core G34-MM1, embedded in the filamentary infrared dark cloud (IRDC) G34.34+00.24 located at a distance of 3.6 kpc, is a promising object for studying fragmentation and outflow processes. Methods. Using data at 93 and 334 GHz obtained from the Atacama Large Millimeter Array (ALMA) database we studied in great detail the hot molecular core G34-MM1. The angular resolution of the data at 334 GHz is about 0.′′8, which allows us to resolve structures of about 0.014 pc (∼2900 au). Results. We found evidence of fragmentation toward the molecular hot core G34-MM1 on two different spatial scales. The dust condensation MM1-A (about 0.06 pc in size) harbors three molecular subcore candidates (SC1 through SC3) detected in 12CO J = 3-2 emission, with typical sizes of about 0.02 pc and an average spatial separation among them of about 0.03 pc. From the HCO+ J = 1-0 emission, we identify, with better angular resolution than previous observations, two perpendicular molecular outflows arising from MM1-A. We suggest that subcores SC1 and SC2, embedded in MM1-A, respectively harbor the sources responsible for the main and the secondary molecular outflow. Finally, from the radio continuum emission at 334 GHz, we marginally detected another dust condensation, named MM1-E, from which a young (tdyn ∼ 1.6 × 103 yr), massive (M ∼ 5 M·), and energetic (E ∼ 6 × 1046 ergs) molecular outflow arises. Conclusions. The fragmentation of the hot molecular core G34-MM1 at two different spatial scales, together with the presence of multiple molecular outflows associated with it, would support a competitive accretion scenario. Studies like this shed light on the relation between fragmentation and star formation processes occurring within hot molecular cores, only accessible through high angular resolution interferometric observations.