Intensity Gradients Technique: Synergy with Velocity Gradients and Polarization Studies

TL;DR

This paper introduces the Intensity Gradients Technique (IGT), a new method that, combined with Velocity Gradient Technique (VGT) and polarization data, enhances the study of magnetic fields, shocks, and gravity in the interstellar medium.

Contribution

The paper presents IGT as a novel tool that complements VGT and polarization studies for analyzing magnetic fields and structures in the interstellar medium.

Findings

IGT successfully maps magnetic fields in HI regions.

IGT can identify shocks and self-gravitating regions.

Combining IGT with VGT and polarimetry improves analysis accuracy.

Abstract

Magnetic fields are ubiquitous in the interstellar medium but are notoriously difficult to study through observation. Making use of the advances in our understanding of MHD turbulence and turbulent reconnection, the Velocity Gradient Technique (VGT) was suggested and successfully applied to study magnetic fields utilizing spectroscopic data. Applying the tools developed for VGT to intensity statistics, we introduce the Intensity Gradients Technique (IGT) as a complementary tool that can be used synergistically with VGT. In this paper, we apply IGT to a diffuse HI region selected from the GALFA-HI survey and compare the intensity gradient maps with those obtained using velocity gradients as well as Planck polarization measurements. We demonstrate the possibility of using IGT and VGT for both studying the magnetic field and identifying shocks in the diffuse interstellar medium. We also explore the ability of IGT in locating self-gravitating regions and calculating Alfvenic Mach number, both alone and in combination with VGT and polarimetry. We compare IGT with the Histogram of Relative Orientation (HRO), which utilizes intensity gradients to characterize the relative orientation of column density structures and local magnetic fields.