Intensity Gradients Technique: Synergy with Velocity Gradients and
  Polarization Studies
  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.
