In search for an observational correlation between the fragmentation level and the magnetic field properties of massive dense cores

Aina Palau, Qizhou Zhang, Josep M. Girart, Junhao Liu, Ram Rao, Patrick M. Koch, Robert Estalella, Huei-Ru Vivien Chen, Hauyu Baobab Liu, Keping Qiu, Zhi-Yun Li, Luis A. Zapata, Sylvain Bontemps, Tao-Chung Ching, Hiroko Shinnaga, Paul T. P. Ho, Aida Ahmadi, Henrik Beuther

Published 2020-10-22Version 1

Theoretical and numerical works indicate that a strong magnetic field should suppress fragmentation in dense cores. However, this has never been tested observationally in a relatively large sample of fragmenting massive dense cores. Here we use the polarization data obtained in the Submillimeter Array Legacy Survey of Zhang et al. (2014) to build a sample of 17 massive dense cores where both fragmentation and magnetic field properties are studied in a uniform way. We measured the fragmentation level, Nmm, within the field of view common to all regions, of ~0.15 pc, with a mass sensitivity of ~0.5 Msun, and a spatial resolution of ~1000 AU. In order to obtain the magnetic field strength using the Davis-Chandrasekhar-Fermi method, we estimated the dispersion of the polarization position angles, the velocity dispersion of the H13CO+(4-3) gas, and the density of each core, all averaged within 0.15 pc. The magnetic field strength was also inferred using the Angular Dispersion Function method. Surprisingly, we found no apparent relation between the fragmentation level and the magnetic field strength, while a possible trend of Nmm with the average density of the parental core was found. In addition, the average masses of the fragments are comparable to the thermal Jeans mass. Therefore, our results suggest that thermal fragmentation and gravity dominate the fragmentation process in this sample. However, when only cores with similar densities are considered, there are hints of a possible anticorrelation between the fragmentation level and the magnetic field strength.