J/A+A/688/A42 Degree of polarization in debris disks (Olofsson+, 2024)
The near-infrared degree of polarization in debris disks.
Toward a self-consistent approach to model scattered light observations.
Olofsson J., Thebault P., Bayo A., Henning T., Milli J.
<Astron. Astrophys. 688, A42 (2024)>
=2024A&A...688A..42O 2024A&A...688A..42O (SIMBAD/NED BibCode)
ADC_Keywords: Stars, pre-main sequence ; Polarization ; Infrared
Keywords: instrumentation: high angular resolution -
instrumentation: polarimeters - Kuiper belt: general - zodiacal dust -
circumstellar matter
Abstract:
Debris disks give us the unique opportunity to probe the properties of
small mu m-sized particles, allowing us to peer into the constituents
of their parent bodies, young analogs of comets and asteroids of our
solar system.
In the past, studies of the total intensity phase function, the
brightness of the disk as a function of the scattering angle, have
proven powerful to constrain the main characteristics of the dust
particles in debris disks. Nonetheless, there can remain some
degeneracies in the modeling that can be alleviated when considering
polarized intensity observations.
We obtained new near-infrared scattered light observations of four
young debris disks, and used state-of-the-art algorithms to recover
the total intensity and linear polarimetric images of the disks. These
images allow us to constrain the degree of linear polarization as a
function of the scattering angle.
All four debris disks are detected in polarized intensity, and three
are also recovered in total intensity. We measured a peak degree of
polarization of ≲40% for all three disks. For the disk around HD
129590, we are also able to determine the degree of polarization in
the radiation-pressure-driven halo. To reproduce the observed
polarization fractions, we find that the particles must consist of
highly refractive and absorbing material. For HD 129590, by measuring
the polarization fraction beyond the birth ring, we constrain the
width of the size distribution to be increasingly small toward greater
radii, which is compatible with the effect of radiation pressure. We
put these findings to the test and present a self-consistent approach
to producing synthetic images, assuming different profiles for the
radiation pressure strength, and accounting for the presence of
unbound grains. We find the contribution of these grains to be
especially critical in order to reproduce the increasing degree of
polarization with stellocentric distance.
Some of our results - namely a very small blow-out size and very
large (n, k) values for the optical constants, which are required to
reproduce the observed degree of polarization - might seem difficult
to reconcile with our understanding of cosmic dust. Similar results
have been obtained for other disks and we discuss the current
limitation of available light-scattering models as well as possible
avenues to alleviate these limitations.
Description:
The disks were observed using the SPHERE/IRDIS instrument, making use
of the star-hopping technique.
Fits files of the polarimetric and total intensity observations.
Two fits files per object, one for the polarimetric data (ending in
"DPI") and one for the total intensity observations (ending in "ADI").
Objects:
----------------------------------------------------
RA (2000) DE Designation(s)
----------------------------------------------------
14 44 30.963 -39 59 20.628 HD129590 = HIP 72070
13 19 19.541 -59 28 20.441 HD115600 = HIP 64995
17 26 17.332 -10 59 34.786 HD157857 = HIP 85331
20 09 05.216 -26 13 26.520 HD191089 = HIP 99273
----------------------------------------------------
File Summary:
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FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
list.dat 86 8 List of fits files
fits/* . 8 Individual fits files
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Byte-by-byte Description of file: list.dat
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Bytes Format Units Label Explanations
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1- 9 F9.5 deg RAdeg Right Ascension of center (J2000)
10- 18 F9.5 deg DEdeg Declination of center (J2000)
20- 22 I3 --- Nx Number of pixels along X-axis
24- 26 I3 --- Ny Number of pixels along Y-axis
28- 30 I3 Kibyte size Size of FITS file
32- 48 A17 --- FileName Name of FITS file, in subdirectory fits
50- 86 A37 --- Title Title of the FITS file
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Acknowledgements:
Johan Olofsson, johan.olofsson(at)eso.org
(End) Patricia Vannier [CDS] 29-May-2024