Revealing Gravitational Collapse in Serpens G3-G6 Molecular Cloud using Velocity Gradients

Abstract

The relative role of turbulence, magnetic fields, self-gravity in star formation is a subject of intensive debate. We present IRAM 30m telescope observations of the 13 CO (1-0) emission in the Serpens G3-G6 molecular cloud and apply to the data a set of statistical methods. Those include the probability density functions (PDFs) of column density and the Velocity Gradients Technique (VGT). We combine our data with the Planck 353 GHz polarized dust emission observations, Hershel H 2 column density. We suggest that the Serpens G3-G6 south clump is undergoing a gravitational collapse. Our analysis reveals that the gravitational collapse happens at volume density n HI ≥ 10 3 cm −3 . We estimate the plane-of-the-sky magnetic field strength of approximately 120 µG using the traditional Davis-Chandrasekhar-Fermi method and 100 µG using a new technique proposed in Lazarian et al. (2020). We find the Serpens G3-G6 south clump's total magnetic field energy significantly surpasses kinetic energy and gravitational energy. We conclude that the gravitational collapse could be successfully triggered in a supersonic and sub-Alfvénic cloud.

Unveiling polarized emission from interstellar dust of the Large Magellanic Cloud with Planck

“…These studies have shown a good correspondence between the magnetic field directions inferred using VGT and that obtained from polarimetry, e.g. with the Planck, BLASTPOL, and HAWC+ data (Hu et al 2019;Alina et al 2022;Hu et al 2020Hu et al , 2021. The property of intensity gradients being related to magnetic field direction has also been used in the developments of Koch et al (2012) to infer magnetic field direction in molecular clouds.…”