Self-Consistent Analysis of OH-Zeeman Observations: Too Much Noise about Noise

TL;DR

This paper re-analyzes OH-Zeeman observations in molecular clouds, challenging previous claims about magnetic field behavior, and presents new evidence of magnetic field variations, emphasizing the importance of less restrictive assumptions in data analysis.

Contribution

It introduces a self-consistent analysis method that relaxes previous assumptions, and refutes claims of a missing cosine factor while providing independent evidence of magnetic field variations.

Findings

No evidence that mass-to-flux ratio decreases from envelopes to cores.

The missing cosine factor claim is false.

Independent evidence suggests magnetic field variations in cloud envelopes.

Abstract

We had recently re-analyzed in a self-consistent way OH-Zeeman observations in four molecular-cloud envelopes and we had shown that, contrary to claims by Crutcher et al., there is no evidence that the mass-to-flux ratio decreases from the envelopes to the cores of these clouds. The key difference between our data analysis and the earlier one by Crutcher et al. is the relaxation of the overly restrictive assumption made by Crutcher et al, that the magnetic field strength is independent of position in each of the four envelopes. In a more recent paper, Crutcher et al. (1) claim that our analysis is not self-consistent, in that it misses a cosine factor, and (2) present new arguments to support their contention that the magnetic-field strength is indeed independent of position in each of the four envelopes. We show that the claim of the missing cosine factor is false, that the new arguments contain even more serious problems than the Crutcher et al. original data analysis, and we present new observational evidence, independent of the OH-Zeeman data, that suggests significant variations in the magnetic-field strength in the four cloud envelopes.