Fragmentation, rotation and outflows in the high-mass star-forming region IRAS 23033+5951: A case study of the IRAM NOEMA large program CORE

Context. The formation process of high-mass stars (> 8 M�) is poorly constrained, particularly, the effects of clump fragmentation creating multiple

systems and the mechanism of mass accretion onto the cores.

Aims. We study the fragmentation of dense gas clumps, and trace the circumstellar rotation and outflows by analyzing observations of the highmass (∼ 500 M�) star-forming region IRAS 23033+5951.

Methods. Using the Northern Extended Millimeter Array (NOEMA) in three configurations and the IRAM 30-m single-dish telescope at 220 GHz,

we probe the gas and dust emission at an angular resolution of ∼0.4500, corresponding to 1900 au.

Results. In the mm continuum emission, we identify a protostellar cluster with at least four mm-sources, where three of them show a significantly

higher peak intensity well above a signal-to-noise ratio of 100. Hierarchical fragmentation from large to small spatial scales is discussed. Two

fragments are embedded in rotating structures and drive molecular outflows, traced by 13CO (2–1) emission. The velocity profiles across two of the

cores are similar to Keplerian but are missing the highest velocity components close to the center of rotation, which is a common phenomena from

observations like these, and other rotation scenarios are not excluded entirely. Position-velocity diagrams suggest protostellar masses of ∼ 6 and

19 M�. Rotational temperatures from fitting CH3CN (12K − 11K) spectra are used for estimating the gas temperature and by that the disk stability

against gravitational fragmentation, utilizing Toomre’s Q parameter. Assuming that the candidate disk is in Keplerian rotation about the central

stellar object and considering different disk inclination angles, we identify only one candidate disk to be unstable against gravitational instability

caused by axisymmetric perturbations.

Conclusions. The dominant sources cover different evolutionary stages within the same maternal gas clump. The appearance of rotation and

outflows of the cores are similar to those found in low-mass star-forming regions.