Testing the Larson relations in massive clumps

Abstract

We tested the validity of the three Larson relations in a sample of 213\nmassive clumps selected from the Herschel Hi-GAL survey and combined with data\nfrom the MALT90 survey of 3mm emission lines. The clumps have been divided in 5\nevolutionary stages to discuss the Larson relations also as function of\nevolution. We show that this ensemble does not follow the three Larson\nrelations, regardless of clump evolutionary phase. A consequence of this\nbreakdown is that the virial parameter $\\alpha_{vir}$ dependence with mass (and\nradius) is only a function of the gravitational energy, independent of the\nkinetic energy of the system, and $\\alpha_{vir}$ is not a good descriptor of\nclump dynamics. Our results suggest that clumps with clear signatures of infall\nmotions are statistically indistinguishable from clumps with no such\nsignatures. The observed non-thermal motions are not necessarily ascribed to\nturbulence acting to sustain the gravity, but they may be due to the\ngravitational collapse at the clump scales. This seems particularly true for\nthe most massive (M$\\geq$1000 M$_{\\odot}$) clumps in the sample, where also\nexceptionally high magnetic fields may not be enough to stabilize the collapse.\n