Fragmentation, rotation, and outflows in the high-mass star-forming region IRAS 23033+5951

Abstract

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 ∼0.45 , 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 13 CO (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 CH 3 CN (12 K − 11 K ) 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.

Physical and chemical structure of high-mass star-forming regions

“…The regions show a large diversity of fragmentation properties (Beuther et al 2018): while some regions contain mainly a single isolated core (e.g., AFGL 2591), other regions fragment into up to 20 cores (e.g., IRAS 21078). Individual case-studies were carried out on some of the regions, e.g., the kinematic properties of W3 H2O (Ahmadi et al 2018), IRAS 23385 (Cesaroni et al 2019), IRAS 23033 (Bosco et al 2019), W3 IRS4 (Mottram et al 2020), and IRAS 21078 (Moscadelli et al 2021); the chemical composition of the pilot regions NGC7538 S and NGC7538 IRS1 (Feng et al 2016), and AFGL 2591 (Gieser et al 2019). A multi-wavelength modeling study of AFGL 2591 is presented in Olguin et al (2020).…”

Disc kinematics and stability in high-mass star formation

“…10 for the model simulations at 800 pc. We always fit the 6σ outer edge for a range of radii and always exclude in the fitting the regions closest to the protostar where the velocity decreases with decreasing distance to the protostar as a result of finite resolution (see Appendix A.3.2 of Bosco et al 2019). The resulting mass estimates from fitting the inner, outer, and entire PV curves for the model simulations and synthetic observations are presented in Fig.…”

Multi-scale view of star formation in IRAS 21078+5211: from clump fragmentation to disk wind

“…The analysis of the continuum emission from cold dust shows a large variety in the fragmentation properties of the sample, from regions where a single massive core dominates to regions where as many as 20 cores, with comparable masses, are detected (Beuther et al 2018). In several CORE targets, employing dense-gas molecular tracers such as the CH 3 CN and CH 3 OH rotational transitions, LSR velocity (V LSR ) gradients are often detected towards the most massive cores of the cluster (Ahmadi et al 2018;Bosco et al 2019;Cesaroni et al 2019;Gieser et al 2019). Extending over typical linear scales of 1000 au, these V LSR gradients are interpreted in terms of the edge-on rotation of either a disk around a high-mass YSO or an unresolved binary (or multiple) system, or the combination of both motions.…”