Detailed Interstellar Polarimetric Properties of the Pipe Nebula at Core Scales

TL;DR

This study uses extensive R-band polarimetry data of the Pipe nebula to analyze magnetic fields, dust grain properties, and turbulence at core scales, revealing a magnetically dominated, sub-Alfvénic environment conducive to early low-mass star formation.

Contribution

It provides detailed polarization measurements at core scales and analyzes magnetic and turbulence properties, offering new insights into the initial conditions of low-mass stellar formation in the Pipe nebula.

Findings

Polarization vectors are aligned perpendicularly to the cloud's long axis.

Dust grains in the diffuse regions are similar to typical Galactic interstellar medium.

Most of the nebula is magnetically dominated with sub-Alfvénic turbulence.

Abstract

We use R-band CCD linear polarimetry collected for about 12000 background field stars in 46 fields of view toward the Pipe nebula to investigate the properties of the polarization across this dark cloud. Based on archival 2MASS data we estimate that the surveyed areas present total visual extinctions in the range 0.6 < Av < 4.6. While the observed polarizations show a well ordered large scale pattern, with polarization vectors almost perpendicularly aligned to the cloud's long axis, at core scales one see details that are characteristics of each core. Although many observed stars present degree of polarization which are unusual for the common interstellar medium, our analysis suggests that the dust grains constituting the diffuse parts of the Pipe nebula seem to have the same properties as the normal Galactic interstellar medium. Estimates of the second-order structure function of the polarization angles suggest that most of the Pipe nebula is magnetically dominated and that turbulence is sub-Alvenic. The Pipe nebula is certainly an interesting region where to investigate the processes prevailing during the initial phases of low mass stellar formation.