Magnetic threads and gravity: ALMA Observations of IRDC G14.225-0.506

TL;DR

This study uses ALMA observations to analyze magnetic field structures in IRDC G14.225-0.506, revealing their evolving role in cloud fragmentation and collapse processes at different scales.

Contribution

It provides detailed magnetic field morphology and strength measurements across multiple regions, highlighting their influence on cloud fragmentation and collapse.

Findings

Magnetic field strength is similar across regions with different fragmentation levels.

Distinct magnetic field morphologies are observed at core scales.

Massive condensations show signs of gravitational collapse with supercritical mass-to-flux ratios.

Abstract

During the star formation process, the interplay between gravity, turbulence, and B-fields is significant, with B-fields apparently serving a regulatory function. However, the extent to which B-fields are decisive relative to turbulence and gravity remains uncertain. This study aims to ascertain the role of B-fields in the fragmentation of molecular clouds. We examine the B-field observed with ALMA at core scales towards the infrared dark cloud G14.225-0.506, focusing on 3 regions with shared physical conditions, and juxtapose it with prior observations at the Hub-filament system scale. Our findings indicate a similar B-field strength and fragmentation level between the 2 hubs. However, distinct B-field morphologies are identified across the 3 regions where polarized emission is detected. In the region N, the large-scale B-field, which is perpendicular to the filamentary structure, persists at smaller scales in the southern half but becomes distorted near the more massive condensations in the northern half. Notably, these condensations exhibit signs of impending collapse, as evidenced by supercritical mass-to-flux values. In the region S, the B-field is considerably inhomogeneous among the detected condensations, and we do not observe a direct correlation between the field morphology and the condensation density. Lastly, in an isolated dust clump located within a southern filament of the northern hub, the B-field aligns parallel to the elongated emission, suggesting a transition in the field geometry. The B-field shows a clear evolution with spatial scales. We propose that the most massive condensations detected in the northern Hub are undergoing gravitational collapse, as revealed by the relative significance of the magnetic field and gravitational potential and mass-to-flux ratio. The distortion of the B-field could be a response to the flow of material due to the collapse.