Experimental Phase Function and Degree of Linear Polarization Curves of Millimeter- sized Cosmic Dust Analogs

Olga Muñoz (1) , Fernando Moreno (1) , J.C. Gómez-Martín (1) , Fernando Vargas-Martin (2) , Daniel Guirado (1) , J. L. Ramos (1) , I. Bustamante (1) , Ivano Bertini (3) , E. Frattin (3) , J. Markannen (4) , Cécilia Tubiana (4) , Marco Fulle (5) , Carsten Güttler (4) , Holger Sierks (4) , Alessandra Rotundi (6) , Vincenzo Della corte (6) , Stavro L. Ivanovski (6) , V.V. Zakharov (6, 7) , Dominique Bockelée-Morvan (7) , Jürgen Blum (8) , Sihane Merouane (4) , Anny Chantal Levasseur-Regourd (9) , Ludmilla Kolokolova (10) , T. Jardiel (11) , A. Caballero (11)

1 IAA - Instituto de Astrofísica de Andalucía
2 Department of Electromagnetism and Electronics [Murcia]
3 Dipartimento di Fisica e Astronomia "Galileo Galilei"
4 MPS - Max-Planck-Institut für Sonnensystemforschung
5 OAT - INAF - Osservatorio Astronomico di Trieste
6 IAPS - Istituto di Astrofisica e Planetologia Spaziali - INAF
7 LESIA - Laboratoire d'études spatiales et d'instrumentation en astrophysique = Laboratory of Space Studies and Instrumentation in Astrophysics
8 IGEP - Institut für Geophysik und Extraterrestrische Physik [Braunschweig]
9 PLANETO - LATMOS
10 Department of Astronomy [College Park]
11 ICV - Instituto de Cerámica y Vidrio

We present laboratory measurements of the phase functions and degree of linear polarization (DLP) curves of a selection of millimeter-sized cosmic dust analog particles. The set includes particles with similar sizes but diverse internal structure (compact and porous) and absorbing properties. The measured phase functions are found to be in all cases very different from those of micron-sized particles. They show a monotonic decrease with increasing phase angle from the back- to the side-scattering region, reaching a minimum at large phase angles before a steep increase of the forward peak. This is in stark contrast to the phase functions of micron-sized particles, which are rather flat at low and intermediate phase angles. The maximum of the DLP for millimeter-sized compact particles is shifted toward larger phase angles (∼130°) compared to that of micron-sized particles (∼90°). Porosity plays an important role in the measured DLP curves: the maximum significantly decreases for increasing porosity as a result of multiple scattering within the particle. Large porous particles with highly absorbing inclusions can reproduce both the OSIRIS/Rosetta phase functions and ground-based DLP observations of comet 67P/Churyumov-Gerasimenko.

Keywords: Circumstellar dust; Polarimetry; Circumstellar disks; Debris disks; Comets; Experimental techniques; Protoplanetary disks

Domains: Astrophysics [astro-ph]

Olga Muñoz, Fernando Moreno, J.C. Gómez-Martín, Fernando Vargas-Martin, Daniel Guirado, et al.. Experimental Phase Function and Degree of Linear Polarization Curves of Millimeter- sized Cosmic Dust Analogs. The Astrophysical Journal Supplement, 2020, 247 (March), pp.19. ⟨10.3847/1538-4365/ab6851⟩. ⟨insu-02434855⟩