Are Stellar Embryos in Perseus Radio-Synchrotron Emitters? Statistical data analysis with Herschel and LOFAR paving the way for the SKA

Abstract

Cosmic rays (CRs) are fundamental to the chemistry and physics of star-forming regions, influencing molecular gas ionization, mediating interactions with interstellar magnetic fields, and regulating star formation from the diffuse interstellar medium to the creation of stellar cores. The electronic GeV component of CRs is expected to produce non-thermal synchrotron radiation detectable at radio frequencies, yet such emissions from Galactic star-forming regions remain elusive. This study reports the first statistical attempt to detect synchrotron emission at 144 MHz using the LOw Frequency ARray (LOFAR) in the nearby Perseus molecular cloud (300 pc). By median-stacking 353 prestellar and 132 protostellar cores from the Herschel Gould Belt Survey and using LOFAR Two-Meter Sky Survey (LoTSS) data (20" resolution), 18 protostellar and 5 prestellar radio candidates were initially identified. However, these were likely extragalactic contaminants within the Herschel catalog. Stacked analyses did not reveal significant radio counterparts for prestellar and protostellar cores, with upper limits of $5\mu$Jy beam${}^{-1}$ and $8\mu$Jy beam${}^{-1}$, respectively. Non-detections suggest strong extinction mechanisms like free-free absorption and the Razin-Tsytovich effect for protostellar cores. For prestellar cores, analytical magnetostatic-isothermal models constrain the maximum ordered magnetic-field strength to 100 $\mu$G. Future predictions suggest that Square Kilometre Array-Low (SKA-Low) arrays could detect this emission in 9 hours (AA*) or 4 hours (AA4), enabling more sensitive constraints on synchrotron radiation in star-forming cores.

13 pages, 14 figures, 2 Appendices. Accepted for publication in Astronomy & Astrophysics

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