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Ultraviolet Spectropolarimetry with Polstar: Interstellar Medium ScienceContinuum polarization over the UV-to-microwave range is due to dichroic extinction (or emission) by asymmetric, aligned dust grains. Scattering can also be an important source of polarization, especially at short wavelengths. Because of both grain alignment and scattering physics, the wavelength dependence of the polarization, generally, traces the size of the aligned grains. Similarly because of the differing wavelength dependencies of dichroic extinction and scattering polarization, the two can generally be reliably separated. Ultraviolet (UV) polarimetry therefore provides a unique probe of the smallest dust grains (diameter<0.09 μm
), their mineralogy and interaction with the environment. However, the current observational status of interstellar UV polarization is very poor with less than 30 lines of sight probed. With the modern, quantitative and well-tested, theory of interstellar grain alignment now available, we have the opportunity to advance the understanding of the interstellar medium (ISM) by executing a systematic study of the UV polarization in the ISM of the Milky Way and near-by galaxies. The Polstar mission will provide the sensitivity and observing time needed to carry out such a program (probing hundreds of stars in the Milky Way and dozens of stars in the LMC/SMC), addressing questions of dust composition as a function of size and location, radiation- and magnetic-field characteristics as well as unveiling the carrier of the 2175 Å extinction feature. In addition, using high-resolution UV line spectroscopy Polstar will search for and probe the alignment of, and polarization from, aligned atoms and ions - so called “Ground State Alignment”, a potentially powerful new probe of magnetic fields in the diffuse ISM.
Document ID
20230006140
Acquisition Source
Goddard Space Flight Center
Document Type
Reprint (Version printed in journal)
Authors
B-G Andersson
(Universities Space Research Association Columbia, Maryland, United States)
G. C. Clayton
(Louisiana State University Baton Rouge, Louisiana, United States)
K. D. Doney
(Lockheed Martin (United States) Bethesda, Maryland, United States)
G. V. Panopoulou
(California Institute of Technology Pasadena, California, United States)
T. Hoang
(Korea Astronomy and Space Science Institute Daejeon, South Korea)
A. M. Magalhaes
(Universidade de São Paulo São Paulo, Brazil)
H. Yan
(Deutsches Elektronen-Synchrotron DESY Hamburg, Germany)
R. Ignace ORCID
(East Tennessee State University Johnson City, Tennessee, United States)
P. A. Scowen
(Goddard Space Flight Center Greenbelt, Maryland, United States)
Date Acquired
April 20, 2023
Publication Date
December 14, 2022
Publication Information
Publication: Astrophysics and Space Science
Publisher: Springer
Volume: 367
Issue: 12
Issue Publication Date: December 1, 2022
ISSN: 0004-640X
e-ISSN: 1572-946X
Subject Category
Astrophysics
Space Sciences (General)
Funding Number(s)
WBS: 981698.01.03.51.02.07.05
CONTRACT_GRANT: NNA17BF53C
CONTRACT_GRANT: NSF AST-1715876
CONTRACT_GRANT: HST-GO-15268.001
CONTRACT_GRANT: HST-HF2-51444.001-A
CONTRACT_GRANT: NAS5-26555
CONTRACT_GRANT: FAPESP 01/12589-1
CONTRACT_GRANT: FAPESP 10/19694-4
CONTRACT_GRANT: CNPq 310506/2015-8
CONTRACT_GRANT: NFR Korea MSIT (No. 2019R1A2C1087045)
CONTRACT_GRANT: NSF AST-2009412
Distribution Limits
Public
Copyright
Portions of document may include copyright protected material.
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