Intensity Gradients Technique: Synergy with Velocity Gradients and Polarization Studies

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