J/A+A/691/A148 PDS 70 disk reduced JWST/MIRI MRS spectrum (Jang+, 2024)
Dust mineralogy and variability of the inner PDS 70 disk.
Insights from JWST/MIRI MRS and Spitzer IRS observations.
Jang H., Waters R., Kaeufer T., Tamanai A., Perotti G., Christiaens V.,
Kamp I., Henning T., Min M., Arabhavi A.M., Barrado D., van Dishoeck E.F.,
Gasman D., Grant S.L., Guedel M., Lagage P.-O., Lahuis F., Schwarz K.,
Tabone B., Temmink M.
<Astron. Astrophys. 691, A148 (2024)>
=2024A&A...691A.148J 2024A&A...691A.148J (SIMBAD/NED BibCode)
ADC_Keywords: Stars, double and multiple ; Exoplanets ; Spectra, infrared
Keywords: methods: data analysis - methods: observational -
protoplanetary disks - infrared: planetary systems
Abstract:
The inner disk of the young star PDS 70 may be a site of rocky planet
formation, with two giant planets detected further out. Recently,
JWST/MIRI MRS observations have revealed the presence of warm water
vapour in the inner disk. Solids in the inner disk may inform us about
the origin of this inner disk water and nature of the dust in the
rocky planet-forming regions of the disk.
We aim to constrain the chemical composition, lattice structure, and
grain sizes of small silicate grains in the inner disk of PDS 70,
observed both in JWST/MIRI MRS and Spitzer IRS.
We use a dust fitting model, called DuCK, based on a two-layer disk
model considering three different sets of dust opacities. We use
Gaussian Random Field and Distribution of Hollow Spheres models to
obtain two sets of dust opacities using the optical constants of
cosmic dust analogues derived from laboratory-based measurements.
These sets take into account the grain sizes as well as their shapes.
The third set of opacities is obtained from the experimentally
measured transmission spectra from aerosol spectroscopy. We use
stoichiometric amorphous silicates, forsterite, and enstatite in our
analysis. We also study the iron content of crystalline olivine using
the resonance at 23-24um and test the presence of fayalite. Both
iron-rich and magnesium-rich amorphous silicate dust species are also
employed to fit the observed spectra.
The Gaussian Random Field opacity set agrees well with the observed
spectrum, better than the other two opacity sets. In both MIRI and
Spitzer spectra, amorphous silicates are the dominant dust species.
Crystalline silicates are dominated by iron-poor olivine. The 23-24um
olivine band peaks at 23.44um for the MIRI spectrum and 23.47um for
the Spitzer spectrum, representing around or less than 10% of iron
content in the crystalline silicate. In all of models, we do not find
strong evidence for enstatite. Moreover, the silicate band in the MIRI
spectrum indicates larger grain sizes (a few microns up to 5um) than
the Spitzer spectrum (0.1 to 1um), indicating a time-variable small
grain reservoir.
The inner PDS 70 disk is dominated by a variable reservoir of warm
(T∼350-500K) amorphous silicates, with ∼15% of forsterite in mass
fraction. The 10um and 18um amorphous silicate bands are very
prominent, indicating that most emission originates from optically
thin dust. We suggest that the small grains detected in the PDS 70
inner disk are likely transported inward from the outer disk as a
result of filtration by the pressure bump associated with the gap and
fragmentation into smaller sizes at the ice line. Collisions among
larger parent bodies may also contribute to the small grain reservoir
in the inner disk, but these parent bodies must be enstatite-poor. In
addition, the variation between MIRI and Spitzer data can be explained
by a combination of grain growth over 15 years and a dynamical inner
disk where opacity changes occur resulting from the highly variable
hot (T∼1000K) innermost dust reservoir.
Description:
Reduced JWST/MIRI MRS spectrum of PDS 70 disk shown in Fig. 1. The
columns are wavelength [micron] and flux [Jy]. The observed data is
publicly available on the MAST database(https://mast.stsci.edu), and
the MINDS pipeline to reduce the data is published in Christiaens et
al., 2024A&A...685L...1C 2024A&A...685L...1C.
Objects:
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RA (2000) DE Designation(s)
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14 08 10.15 -41 23 52.5 PDS 70 = V* V1032 Cen
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
pds70sp.dat 38 11507 Reduced JWST/MIRI MRS spectrum of PDS 70 disk
shown in Fig. 1
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See also:
J/A+A/632/A25 : PDS70 VLT/SPHERE images (Mesa+, 2019)
J/A+A/689/A65 : ALMA line emission obs. of PDS 70 disk (Rampinelli+, 2024)
Byte-by-byte Description of file: pds70sp.dat
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Bytes Format Units Label Explanations
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1- 19 F19.16 um lambda Wavelength
21- 38 F18.16 Jy Flux Flux
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Acknowledgements:
Hyerin Jang, hyerin.jang(at)astro.ru.nl
(End) Patricia Vannier [CDS] 07-Sep-2024