Interstellar polarization from 3 to 5 microns in reddened stars
P. G. Martin, A. J. Adamson, D. C. B. Whittet, J. H. Hough, J. A. Bailey, S. H. Kim, S. Sato, M. Tamura, T. Yamashita;
ApJ, 1992, 392, 691
ABSTRACT:The study reports measurements of IR interstellar linear polarization in the spectral range 2-5
microns for 18 highly reddened stars.
The observations covered lines of sight
with wavelengths of peak polarization lambda(max) ranging from the
blue-UV (0.35 micron) to the near-IR (0.78 micron).
It is shown that excess
polarization occurs at 3-5 microns relative to the standard Serkowski/Wilking
empirical formula describing the wavelength dependence of polarization in the
optical and near-IR out to 2.2 microns.
The results of Nagata (1990) and Jones
(1990) that significant excess exists at 3.6-3.8 microns are confirmed, and
it is shown that it persists to 5 microns.
It is found that neither the
excess polarization relative to the Serkowski/Wilking formula nor the value
of the power-law index is correlated to changes in lambda(max).
Hence,
the IR polarization does not respond to changes in the properties of the
grains which give rise to dramatic variations in the wavelength dependence of
polarization at shorter wavelengths, suggesting a degree of invariance in the form
of the IR polarization law.
KEYWORDS: cosmic dust, infrared stars, interstellar extinction, linear polarization, infrared astronomy, molecular clouds
PERSOKEY:polarisation, nir, extinction, ,
CODE: martin92