Challenges in probing turbulent and magnetic support in cores: The W43-MM1 protocluster case study

Estimating the level of non thermal support in cores is both challenging yet crucial for constraining the earliest stages of star formation and improving our understanding of the underlying physical processes. We aim to quantify the kinetic and magnetic support operating within the cores of the high-mass protocluster W43-MM1, and to test the simple assumptions behind the approximated virial theorem, which is used to interpret observations. We used ALMA 12,m molecular line observations of DCN,(3–2), ^ 13 CS ,(5–4), and mathrm CH_3CN ,(5_3–4_3) to estimate the kinetic support. The plane-of-sky magnetic field strength (B_ was derived from ALMA 12,m dust-polarization observations using the Davis–Chandrasekhar–Fermi (DCF) method. The B_ estimates were obtained in areas with a diameter of sim12,500,au ( the three-beam scale of polarimetric observations), which ensures statistically meaningful measurements for the DCF analysis. These values were then extrapolated to core scales (sim2,500,au) using the density–field strength relation. -1 . The three-beam scale B_ > 1. These numbers are unexpectedly high, especially for protostellar cores that are expected to be undergoing collapse. values span 1.1–22.5 mG, which extrapolate to 1.1–49.3 mG at the core scale. Using the virial theorem, we find 16 out of the subset of 24 cores with turbulence alone (sim70,%) to be stable against gravitational collapse. From the subset of 21 cores with both estimates, ten cores (∼ 50,%) appear to be magnetically supported against gravity when considering magnetic fields alone. Combining both estimates, 18 cores (∼ 85,%) are found with α_ vir,B -1 and consistent with previous observational studies), together with the omission of surface terms in the observational virial theorem, prevents us from accurately measuring the non thermal support in cores. This highlights that any simplified framework of a virial analysis can introduce significant biases when assessing the physical support mechanisms within cores.