J/A+A/683/A22 HD181327 SI,Q_phi and U_phi SPHERE/IRDIS images (Milli+, 2024)
The polarisation properties of the HD 18327 debris ring.
Evidence for sub-micron particles from scattered light observations.
Milli J., Choquet E., Tazaki R., Menard F., Augereau J.-C., Olofsson J.,
Thebault P., Poch O., Levasseur-Regourd A.-C., Lasue J., Renard J.-B.,
Hadamcik E., Baruteau C., Schmid H.M., Engler N., van Holstein R.G.,
Zubko E., Lagrange A.-M., Marino S., Pinte C., Dominik C., Boccaletti A.,
Langlois M., Zurlo A., Desgrange C., Gluck L., Mouillet D., Costille A.,
Sauvage J.-F.
<Astron. Astrophys. 683, A22 (2024)>
=2024A&A...683A..22M 2024A&A...683A..22M (SIMBAD/NED BibCode)
ADC_Keywords: Stars, early-type ; Polarization ; Infrared
Keywords: polarization - scattering - instrumentation: high angular resolution -
comets: general - Kuiper belt: general - planetary systems
Abstract:
Polarisation is a powerful remote-sensing tool to study the nature of
particles scattering the starlight. It is widely used to characterise
interplanetary dust particles in the Solar System and increasingly
employed to investigate extrasolar dust in debris discs' systems.
We aim to measure the scattering properties of the dust from the
debris ring around HD 181327 at near-infrared wavelengths.
We obtained high-contrast polarimetric images of HD 181327 in the H
band with the SPHERE/IRDIS instrument on the Very Large Telescope
(ESO). We complemented them with archival data from HST/NICMOS in
the F110W filter reprocessed in the context of the Archival Legacy
Investigations of Circumstellar Environments (ALICE) project. We
developed a combined forward-modelling framework to simultaneously
retrieve the scattering phase function in polarisation and intensity.
We detected the debris disc around HD 181327 in polarised light and
total intensity. We measured the scattering phase function and the
degree of linear polarisation of the dust at 1.6um in the birth
ring. The maximum polarisation is 23.6%±2.6% and occurs between a
scattering angle of 70° and 82°.
We show that compact spherical particles made of a highly refractive
and relatively absorbing material in a differential power-law size
distribution of exponent -3.5 can simultaneously reproduce the
polarimetric and total intensity scattering properties of the dust.
This type of material cannot be obtained with a mixture of silicates,
amorphous carbon, water ice, and porosity, and requires a more
refracting component such as iron-bearing minerals. We reveal a
striking analogy between the near-infrared polarisation of comets and
that of HD 181327. The methodology developed here combining VLT/SPHERE
and HST/NICMOS may be applicable in the future to combine the
polarimetric capabilities of SPHERE with the sensitivity of JWST.
Description:
The fits files contain the final reduced images of Stokes I, Q_phi and
U_phi of HD181327, obtained with the SPHERE IRDIS instrument in the
broad-band H filter on the night of 2017-05-15. The astrophysical
signal of the disc is contained in the I and Q_phi image while the
U_phi image contains only noise. The images have a size of
400x400 pixels and are expressed in mJy/arcsec2 with a pixel size of
0.0122-arcsec. These 3 images are presented in Fig. 2 of the paper.
Objects:
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RA (2000) DE Designation(s)
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19 22 58.94 -54 32 16.9 HD 181327 = CD-54 8270
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
list.dat 98 3 List of fits images
fits/* . 3 Individual fits images
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See also:
J/A+A/595/A31 : SAM detection limits of 8 debris disks (Gauchet+, 2016)
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- 25 F6.4 arcsec/pix scale Scale of the image
27- 29 I3 --- Nx Number of pixels along X-axis
31- 33 I3 --- Ny Number of pixels along Y-axis
35- 56 A22 "datime" Obs.date Observation date
58- 60 I3 Kibyte size Size of FITS file
62- 70 A9 --- FileName Name of FITS file, in subdirectory fits
72- 98 A27 --- Title Title of the FITS file
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Acknowledgements:
Julien Milli, julien.milli(at)univ-grenoble-alpes.fr
(End) Julien Milli [IPAG, France], Patricia Vannier [CDS] 11-Dec-2023