2001/05/31 by Pablo Fosalba, Alex Lazarian, A. Lazarian +4 · 1 citation
Physics and Astronomy · #Astronomy #Astrophysics #Astrophysics and Star Formation Studies #Circular polarization #Degree of polarization #Galactic plane #Galaxy #Interstellar medium #Linear polarization #Magnetic field #Milky Way #Multipole expansion #Optics #Physics #Polarization (electrochemistry) #Polarization in astronomy #Scattering #Sky #Solar and Space Plasma Dynamics #Starlight #Stars #Stellar, planetary, and galactic studies #astro-ph
paper · pdf · doi:10.1086/324297
published as Astrophys.J. 564 (2002) 762-772 · 31 pages, 11 figures. Minor corrections and some clarifications included. Matches version accepted for publication by the Astrophysical Journal
arxiv created 2001/08/22 · openalex publication_date 2002/01/10 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/06
We present a statistical analysis of Galactic interstellar polarization from the largest compilation available of starlight data. The data comprises ~9300 stars, of which we have selected ~5500 for our analysis. We find a nearly linear growth of mean polarization degree with extinction. The amplitude of this correlation shows that interstellar grains are not fully aligned with the Galactic magnetic field, which can be interpreted as the effect of a large random component of the field. In agreement with earlier studies of more limited scope, we estimate the ratio of the uniform to the random plane-of-the-sky components of the magnetic field to be B u / B r ≈ 0.8. Moreover, a clear correlation exists between polarization degree and polarization angle that provides evidence that the magnetic field geometry follows Galactic structures on large scales. The angular power spectrum C ℓ of the starlight polarization degree for Galactic plane data (| b | < 10°) is consistent with a power law, C ℓ ∝ ℓ -1.5 (where ℓ ≈ 180°/θ is the multipole order), for all angular scales θ ≳ 10'. An investigation of sparse and inhomogeneous sampling of the data shows that the starlight data analyzed traces an underlying polarized continuum that has the same power-spectrum slope, C ℓ ∝ ℓ -1.5 . Our findings suggest that starlight data can be safely used for the modeling of Galactic polarized continuum emission at other wavelengths.