ALMA-IMF XX: Core fragmentation in the W51 high-mass star-forming region
T. Yoo, A. Ginsburg, J. Braine, N. Budaiev, F. Louvet, F. Motte, A. M. Stutz, B. Thomasson, M. Armante, M. Bonfand, S. Bontemps, L. Bronfman, G. Busquet, T. Csengeri, N. Cunningham, J. Di Francesco, D. J. Díaz-González, M. Fernández-Lopez, R. Galván-Madrid, C. Goddi, A. Gusdorf, N. Kessler, A. Koley, H. -L Liu, T. Nony, F. Olguin, P. Sanhueza, M. Valeille-Manet, L. A. Zapata, Q. Zhang
Published: 2025/9/8
Abstract
We present a study of core fragmentation in the W51-E and W51-IRS2 protoclusters in the W51 high-mass star-forming region. The identification of core fragmentation is achieved by the spatial correspondence of cores and compact sources which are detected in the short (low resolution) and the long baseline (high resolution) continuum images with the Atacama Large Millimeter/submillimeter Array (ALMA) in Bands 3 (3 mm) and 6 (1.3 mm), respectively. We characterize the compact sources found in the long baseline image, and conclude that the compact sources are pre/protostellar objects (PPOs) that are either prestellar dust cores or dust disks or envelopes around protostars. The observed trend of core fragmentation in W51 is that (i) massive cores host more PPOs, (ii) bright PPOs are preferentially formed in massive cores, (iii) equipartition of flux between PPOs is uncommon. Thermal Jeans masses of parent cores are insufficient to explain the masses of their fragments, and this trend is more prominent at high-mass cores. We also find that unfragmented cores are large, less massive, and less dense than fragmented cores.