J/A+A/642/L15 Near-infrared spectra for TW Hya (McLure+, 2020)
Measuring the atomic composition of planetary building blocks.
McLure M., Dominik C., Kama M.
<Astron. Astrophys. 642, L15 (2020)>
=2020A&A...642L..15M 2020A&A...642L..15M (SIMBAD/NED BibCode)
ADC_Keywords: Stars, pre-main sequence ; Spectra, infrared
Keywords: astrochemistry - techniques: spectroscopic -
stars: variables: T Tauri - Herbig Ae/Be - protoplanetary disks
Abstract:
Volatile molecules are critical to terrestrial planetary habitability,
yet they are difficult to observe directly where planets form at the
midplanes of protoplanetary disks. It is unclear whether the inner
∼1AU of disks are volatile-poor or if this region is resupplied
with ice-rich dust from colder disk regions. Dust traps at radial
pressure maxima bounding disk gaps can cut off the inner disk from
these types of volatile reservoirs. However, the trap retention
efficiency and atomic composition of trapped dust have not been
measured.
We present a new technique to measure the absolute atomic abundances
in the gas accreting onto T Tauri stars and infer the bulk atomic
composition and distribution of midplane solids that have been
retained in the disk around the young star TW Hya.
We identify near-infrared atomic line emission from gas-phase material
inside the dust sublimation rim of TW Hya. Gaussian decomposition of
the strongest H Paschen lines isolates the inner disk hydrogen
emission. We measure several key elemental abundances, relative to
hydrogen, using a chemical photoionization model and infer dust
retention in the disk. With a 1D transport model, we determine
approximate radial locations and retention efficiencies of dust traps
for different elements.
Volatile and refractory elements are depleted from TW Hya's hot gas by
factors of ∼102 and up to 105, respectively. The abundances of the
trapped solids are consistent with a combination of primitive Solar
System bodies. Dust traps beyond the CO and N2 snow line cumulatively
sequester 96% of the total dust flux, while the trap at 2AU, near the
H2O snow line, retains 3%. The high depletions of Si, Mg, and Ca are
explained by a third trap at 0.3AU with >95% dust retention.
TW Hya sports a significant volatile reservoir rich in C- and N-ices
in its outer submillimeter ring structure. However, unless the inner
disk was enhanced in C by earlier radial transport, typical C
destruction mechanisms and the lack of a C resupply should leave the
terrestrial planet-forming region of TW Hya "dry" and carbon-poor. Any
planets that form within the silicate dust trap at 0.3 AU could
resemble Earth in terms of the degree of their volatile depletion.
Description:
Catalog contains three fits files, each containing one epoch of
near-infrared spectra for TW Hya. Epoch 1 and 2 are archival ESO
VLT-Xshooter spectra that were downloaded from the ESO archive and
corrected for telluric absorption with the MOLECFIT tool. Epoch 3 was
observed with Magellan FIRE and corrected for telluric absorption with
the standard FIREHose pipeline and a telluric standard star. All other
information regarding these data can be found in Appendix A of the
paper.
One spectrum of TW Hya was obtained with the FIRE spectrograph (Simcoe
et al., 2013PASP..125..270S 2013PASP..125..270S) at Las Campanas (R∼6000,
0.8<λ<2.5um)(30) on January 2, 2013 (PI McClure). Two 6.0
second exposures in the Fowler 1 read mode were obtained with the 0.6"
slit under 0.45" seeing at an airmass of 1.009 in excellent conditions.
We obtained the usual suite of arc lamp and flat-field calibrations and
extracted the FIRE spectrum using the standard FIREhose pipeline, with
MCN 7202 as the telluric calibrator star. The other two spectra were
obtained with VLT X-shooter (Vernet et al., 2011A&A...536A.105V 2011A&A...536A.105V)
(visible: 0.8-1um, R∼18000; near-IR arm: 1-2.5um, R∼11000) on April 7,
2010 and May 3, 2010. We corrected ESO's Phase 3 reduced data for
telluric absorption using the MolecFit software package. Spectra from
all three epochs were corrected for their heliocentric velocities, and
the X-Shooter spectra were convolved down to the resolution of the
FIRE spectrum.
Objects:
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RA (2000) DE Designation(s)
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11 01 51.91 -34 42 17.0 TW Hya = HIP 53911
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
list.dat 125 3 List of fits spectra
fits/* . 3 Individual fits spectra
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See also:
J/A+A/592/A49 : TW Hya CO (2-1), CN (2-1) & CS (5-4) data cubes (Teague+, 2016)
J/A+A/592/A83 : HD 100546 and TW Hya model abundances (Kama+, 2016)
J/ApJ/862/L2 : First detection of HCOOH in TW Hya disk with ALMA (Favre+ 2018)
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- 24 I5 --- Nx Number of pixels along X-axis
26- 49 A24 "datime" Obs.date Observation date
51- 54 I4 Kibyte size Size of FITS file
56- 66 A11 --- FileName Name of FITS file, in subdirectory fits
68-125 A58 --- Title Title of the FITS file
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Acknowledgements:
Melissa McLure, mcclure(at)strw.leidenuniv.nl
(End) Patricia Vannier [CDS] 25-Sep-2020