JOYS: Disentangling the warm and cold material in the high-mass IRAS 23385+6053 cluster

Context. High-mass star formation occurs in a clustered mode where fragmentation is observed from an early stage onward. Young protostars can now be studied in great detail with the recently launched James Webb Space Telescope (JWST).Aims. We study and compare the warm (>100 K) and cold (<100 K) material toward the high-mass star-forming region (HMSFR) IRAS 23385+6053 (IRAS 23385 hereafter) combining high-angular-resolution observations in the mid-infrared (MIR) with the JWST Observations of Young protoStars (JOYS) project and with the NOrthern Extended Millimeter Array (NOEMA) at millimeter (mm) wavelengths at angular resolutions of approximate to 0.'' 2-1.'' 0.Methods. We investigated the spatial morphology of atomic and molecular species using line-integrated intensity maps. We estimated the temperature and column density of different gas components using H-2 transitions (warm and hot component) and a series of CH3CN transitions as well as 3 mm continuum emission (cold component).Results. Toward the central dense core of IRAS 23385, the material consists of relatively cold gas and dust (approximate to 50 K), while multiple outflows create heated and/or shocked H-2 and show enhanced temperatures (approximate to 400 K) along the outflow structures. An energetic outflow with enhanced emission knots of [Fe II] and [Ni II] suggests J-type shocks, while two other outflows have enhanced emission of only H-2 and [S I] caused by C-type shocks. The latter two outflows are also more prominent in molecular line emission at mm wavelengths (e.g., SiO, SO, H2CO, and CH3OH). Data of even higher angular resolution are needed to unambiguously identify the outflow-driving sources given the clustered nature of IRAS 23385. While most of the forbidden fine structure transitions are blueshifted, [Ne II] and [Ne III] peak at the source velocity toward the MIR source A/mmA2 suggesting that the emission is originating from closer to the protostar.Conclusions. The warm and cold gas traced by MIR and mm observations, respectively, are strongly linked in IRAS 23385. The outflows traced by MIR H-2 lines have molecular counterparts in the mm regime. Despite the presence of multiple powerful outflows that cause dense and hot shocks, a cold dense envelope still allows star formation to further proceed. To study and fully understand the spatially resolved MIR properties, a representative sample of low- and high-mass protostars has to be probed using JWST.

Automated summary

The study focuses on the high-mass star-forming region IRAS 23385, investigating warm and cold gas components using high-angular-resolution mid-infrared and millimeter observations. The results show a strong connection between warm and cold gas, with outflows traced by mid-infrared H-2 lines having molecular counterparts in the millimeter regime. Despite multiple powerful outflows causing dense and hot shocks, a cold dense envelope allows star formation to proceed. Further research with JWST is needed to fully understand the spatially resolved mid-infrared properties of low- and high-mass protostars.