The Water-ice Feature in Near-infrared Disk-scattered Light around HD 142527: Micron-sized Icy Grains Lifted up to the Disk Surface?

Abstract We study the 3 μm scattering feature of water ice detected in the outer disk of HD 142527 by performing radiative transfer simulations. We show that an ice mass abundance at the outer disk surface of HD 142527 is much lower than estimated in a previous study. It is even lower than inferred from far-infrared ice observations, implying ice disruption at the disk surface. Next, we demonstrate that a polarization fraction of disk-scattered light varies across the ice-band wavelengths depending on ice grain properties; hence, polarimetric spectra would be another tool for characterizing water-ice properties. Finally, we argue that the observed reddish disk-scattered light is due to grains a few microns in size. To explain the presence of such grains at the disk surface, we need a mechanism that can efficiently oppose dust settling. If we assume turbulent mixing, our estimate requires α ≳ 2 × 10−3, where α is a nondimensional parameter describing the vertical diffusion coefficient of grains. Future observations probing gas kinematics would be helpful to elucidate vertical grain dynamics in the outer disk of HD 142527.

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Carbon depletion observed inside T Tauri inner rims

Astronomy and Astrophysics ◽

10.1051/0004-6361/201834361 ◽

2019 ◽

Vol 632 ◽

pp. A32 ◽

Cited By ~ 2

Author(s):

M. K. McClure

Keyword(s):

Carbon Content ◽

Near Infrared ◽

Protoplanetary Disks ◽

Far Infrared ◽

T Tauri Stars ◽

Outer Disk ◽

Carbon Abundance ◽

T Tauri ◽

Medium Resolution ◽

Complete Set

Context. The carbon content of protoplanetary disks is an important parameter to characterize planets formed at different disk radii. There is some evidence from far-infrared and submillimeter observations that gas in the outer disk is depleted in carbon, with a corresponding enhancement of carbon-rich ices at the disk midplane. Observations of the carbon content inside of the inner sublimation rim could confirm how much carbon remains locked in kilometer size bodies in the disk. Aims. I aim to determine the density, temperature, and carbon abundance inside the disk dust sublimation rim in a set of T Tauri stars with full protoplanetary disks. Methods. Using medium-resolution, near-infrared (0.8–2.5 μm) spectra and the new Gaia DR2 distances, I self-consistently determine the stellar, extinction, veiling, and accretion properties of the 26 stars in my sample. From these values, and non-accreting T Tauri spectral templates, I extract the inner disk excess of the target stars from their observed spectra. Then I identify a series of C0 recombination lines in 18 of these disks and use the CHIANTI atomic line database with an optically thin slab model to constrain the average ne, Te, and nc for these lines in the five disks with a complete set of lines. By comparing these values with other slab models of the inner disk using the Cloudy photoionization code, I also constrain nH and the carbon abundance, XC, and hence the amount of carbon “missing” from the slab. For one disk, DR Tau, I use relative abundances for the accretion stream from the literature to also determine XSi and XN. Results. The inner disks modeled here are extremely dense (nH ~ 1016 cm−3), warm (Te ~ 4500 K), and moderately ionized (log Xe ~ 3.3). Three of the five modeled disks show robust carbon depletion up to a factor of 42 relative to the solar value. I discuss multiple ways in which the “missing” carbon could be locked out of the accreting gas. Given the high-density inner disk gas, evidence for radial drift, and lack of obvious gaps in these three systems, their carbon depletion is most consistent with the “missing” carbon being sequestered in kilometer size bodies. For DR Tau, nitrogen and silicon are also depleted by factors of 45 and 4, respectively, suggesting that the kilometer size bodies into which the grains are locked were formed beyond the N2 snowline. I explore briefly what improvements in the models and observations are needed to better address this topic in the future.

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The dry and carbon-poor inner disk of TW Hydrae: evidence for a massive icy dust trap

Astronomy and Astrophysics ◽

10.1051/0004-6361/201936638 ◽

2019 ◽

Vol 632 ◽

pp. L10 ◽

Cited By ~ 2

Author(s):

Arthur D. Bosman ◽

Andrea Banzatti

Keyword(s):

Elemental Carbon ◽

Near Infrared ◽

Giant Planet ◽

Giant Planets ◽

Low Carbon ◽

Dust Trap ◽

Water Ice ◽

Carbon Carrier ◽

Outer Disk ◽

Best Fitting

Context. Gas giants accrete their envelopes from the gas and dust of proto-planetary disks, and therefore it is important to determine the composition of the inner few astronomical units, where most giant planets are expected to form. Aims. We aim to constrain the elemental carbon and oxygen abundance in the inner disk (R < 2.3 AU) of TW Hya and compare with the outer disk (R > 2.3 AU) where carbon and oxygen appear underabundant by a factor of approximately 50. Methods. Archival Spitzer-IRS and VLT-CRIRES observations of TW Hya were compared with a detailed thermo-chemical model, DALI. The inner disk gas mass and elemental C and O abundances were varied to fit the mid-infrared H2 and H2O line fluxes as well as the near-infrared CO line flux. Results. Best-fitting models have an inner disk that has a gas mass of 2 × 10−4 M⊙ with C/H ≈ 3 × 10−6 and O/H ≈ 6 × 10−6. The elemental oxygen and carbon abundances of the inner disk are about 50 times lower than in the interstellar medium and are consistent with those found in the outer disk. Conclusions. The uniformly low volatile abundances imply that the inner disk is not enriched by ices on drifting bodies that evaporate. This indicates that drifting grains are stopped in a dust trap outside the water ice line. Such a dust trap would also form a cavity as seen in high-resolution submillimeter continuum observations. If CO is the major carbon carrier in the ices, dust needs to be trapped efficiently outside the CO ice line of ∼20 AU. This would imply that the shallow submillimeter rings in the TW Hya disk outside of 20 AU correspond to very efficient dust traps. The most likely scenario is that more than 98% of the CO has been converted into less volatile species, for example CO2 and CH3OH. A giant planet forming in the inner disk would be accreting gas with low carbon and oxygen abundances as well as very little icy dust, potentially leading to a planet atmosphere with strongly substellar C/H and O/H ratios.

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Dust modeling of the combined ALMA and SPHERE datasets of HD 163296

Astronomy and Astrophysics ◽

10.1051/0004-6361/201732299 ◽

2018 ◽

Vol 614 ◽

pp. A24 ◽

Cited By ~ 19

Author(s):

G. A. Muro-Arena ◽

C. Dominik ◽

L. B. F. M. Waters ◽

M. Min ◽

L. Klarmann ◽

...

Keyword(s):

Near Infrared ◽

Thermal Emission ◽

Scattered Light ◽

Spectral Energy Distribution ◽

Spectral Energy ◽

Dust Grains ◽

Outer Disk ◽

Group I ◽

Dust Evolution ◽

Small Dust

Context. Multiwavelength observations are indispensable in studying disk geometry and dust evolution processes in protoplanetary disks. Aims. We aim to construct a three-dimensional model of HD 163296 that is capable of reproducing simultaneously new observations of the disk surface in scattered light with the SPHERE instrument and thermal emission continuum observations of the disk midplane with ALMA. We want to determine why the spectral energy distribution of HD 163296 is intermediary between the otherwise well-separated group I and group II Herbig stars. Methods. The disk was modeled using the Monte Carlo radiative transfer code MCMax3D. The radial dust surface density profile was modeled after the ALMA observations, while the polarized scattered light observations were used to constrain the inclination of the inner disk component and turbulence and grain growth in the outer disk. Results. While three rings are observed in the disk midplane in millimeter thermal emission at ~80, 124, and 200 AU, only the innermost of these is observed in polarized scattered light, indicating a lack of small dust grains on the surface of the outer disk. We provide two models that are capable of explaining this difference. The first model uses increased settling in the outer disk as a mechanism to bring the small dust grains on the surface of the disk closer to the midplane and into the shadow cast by the first ring. The second model uses depletion of the smallest dust grains in the outer disk as a mechanism for decreasing the optical depth at optical and near-infrared wavelengths. In the region outside the fragmentation-dominated regime, such depletion is expected from state-of-the-art dust evolution models. We studied the effect of creating an artificial inner cavity in our models, and conclude that HD 163296 might be a precursor to typical group I sources.

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Discovery of a planetary-mass companion within the gap of the transition disk around PDS 70

Astronomy and Astrophysics ◽

10.1051/0004-6361/201832957 ◽

2018 ◽

Vol 617 ◽

pp. A44 ◽

Cited By ~ 153

Author(s):

M. Keppler ◽

M. Benisty ◽

A. Müller ◽

Th. Henning ◽

R. van Boekel ◽

...

Keyword(s):

Rayleigh Scattering ◽

Near Infrared ◽

Planet Formation ◽

Scattered Light ◽

Position Angle ◽

Brightness Distribution ◽

Young Star ◽

Outer Disk ◽

Planetary Mass ◽

Differential Imaging

Context. Young circumstellar disks are the birthplaces of planets. Their study is of prime interest to understand the physical and chemical conditions under which planet formation takes place. Only very few detections of planet candidates within these disks exist, and most of them are currently suspected to be disk features. Aims. In this context, the transition disk around the young star PDS 70 is of particular interest, due to its large gap identified in previous observations, indicative of ongoing planet formation. We aim to search for the presence of an embedded young planet and search for disk structures that may be the result of disk–planet interactions and other evolutionary processes. Methods. We analyse new and archival near-infrared images of the transition disk PDS 70 obtained with the VLT/SPHERE, VLT/NaCo, and Gemini/NICI instruments in polarimetric differential imaging and angular differential imaging modes. Results. We detect a point source within the gap of the disk at about 195 mas (~22 au) projected separation. The detection is confirmed at five different epochs, in three filter bands and using different instruments. The astrometry results in an object of bound nature, with high significance. The comparison of the measured magnitudes and colours to evolutionary tracks suggests that the detection is a companion of planetary mass. The luminosity of the detected object is consistent with that of an L-type dwarf, but its IR colours are redder, possibly indicating the presence of warm surrounding material. Further, we confirm the detection of a large gap of ~54 au in size within the disk in our scattered light images, and detect a signal from an inner disk component. We find that its spatial extent is very likely smaller than ~17 au in radius, and its position angle is consistent with that of the outer disk. The images of the outer disk show evidence of a complex azimuthal brightness distribution which is different at different wavelengths and may in part be explained by Rayleigh scattering from very small grains. Conclusions. The detection of a young protoplanet within the gap of the transition disk around PDS 70 opens the door to a so far observationally unexplored parameter space of planetary formation and evolution. Future observations of this system at different wavelengths and continuing astrometry will allow us to test theoretical predictions regarding planet–disk interactions, planetary atmospheres, and evolutionary models.

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Evolution of protoplanetary disks from their taxonomy in scattered light: spirals, rings, cavities, and shadows

Astronomy and Astrophysics ◽

10.1051/0004-6361/201833872 ◽

2018 ◽

Vol 620 ◽

pp. A94 ◽

Cited By ~ 27

Author(s):

A. Garufi ◽

M. Benisty ◽

P. Pinilla ◽

M. Tazzari ◽

C. Dominik ◽

...

Keyword(s):

Main Sequence ◽

Near Infrared ◽

Scattered Light ◽

Selection Effect ◽

Protoplanetary Disks ◽

Young Stars ◽

Outer Disk ◽

Disk Mass ◽

Dust Mass ◽

Taxonomical Study

Context. Dozens of protoplanetary disks have been imaged in scattered light during the last decade. Aims. The variety of brightness, extension, and morphology from this census motivates a taxonomical study of protoplanetary disks in polarimetric light to constrain their evolution and establish the current framework of this type of observation. Methods. We classified 58 disks with available polarimetric observations into six major categories (Ring, Spiral, Giant, Rim, Faint, and Small disks) based on their appearance in scattered light. We re-calculated the stellar and disk properties from the newly available Gaia DR2 and related these properties with the disk categories. Results. More than half of our sample shows disk substructures. For the remaining sources, the absence of detected features is due to their faintness, their small size, or the disk geometry. Faint disks are typically found around young stars and typically host no cavity. There is a possible dichotomy in the near-infrared (NIR) excess of sources with spiral-disks (high) and ring-disks (low). Like spirals, shadows are associated with a high NIR excess. If we account for the pre-main sequence evolutionary timescale of stars with different mass, spiral arms are likely associated with old disks. We also found a loose, shallow declining trend for the disk dust mass with time. Conclusions. Protoplanetary disks may form substructures like rings very early in their evolution but their detectability in scattered light is limited to relatively old sources ( ≳5 Myr) where the recurrently detected disk cavities cause the outer disk to be illuminate. The shallow decrease of disk mass with time might be due to a selection effect, where disks observed thus far in scattered light are typically massive, bright transition disks with longer lifetimes than most disks. Our study points toward spirals and shadows being generated by planets of a fraction of a Jupiter mass to a few Jupiter masses in size that leave their (observed) imprint on both the inner disk near the star and the outer disk cavity.

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Accretion and Outflow Activity in the Earliest Phases of Star-Formation: CO, Sub-mm Continuum, and Near-Infrared Observations

International Astronomical Union Colloquium ◽

10.1017/s0252921100043645 ◽

1997 ◽

Vol 163 ◽

pp. 725-726

Author(s):

K.-W. Hodapp ◽

E. F. Ladd

Keyword(s):

Near Infrared ◽

Spectral Energy Distribution ◽

Far Infrared ◽

Point Sources ◽

Spectral Energy ◽

Infrared Observations ◽

Circumstellar Material ◽

Dense Cores ◽

Wavelength Radiation ◽

Main Component

Stars in the earliest phases of their formation, i.e., those accreting the main component of their final mass, are deeply embedded within dense cores of dust and molecular material. Because of the high line-of-sight extinction and the large amount of circumstellar material, stellar emission is reprocessed by dust into long wavelength radiation, typically in the far-infrared and sub-millimeter bands. Consequently, the youngest sources are strong submillimeter continuum sources, and often undetectable as point sources in the near-infrared and optical. The most deeply embedded of these sources have been labelled “Class 0” sources by André, Ward-Thompson, & Barsony (1994), in an extension of the spectral energy distribution classification scheme first proposed by Adams, Lada, & Shu (1987).

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Atmospheres on Callisto composed of sublimated water vapor and its photochemical products

10.5194/epsc2021-3 ◽

2021 ◽

Author(s):

Shane Carberry Mogan ◽

Orenthal Tucker ◽

Robert Johnson ◽

Audrey Vorburger ◽

Andre Galli ◽

...

Keyword(s):

Monte Carlo ◽

Near Infrared ◽

Hubble Space Telescope ◽

Mass Movement ◽

Complex Surface ◽

Atmospheric Modeling ◽

Galilean Satellites ◽

Geophysical Research ◽

Water Ice ◽

Remote Determination

The parameter space for the very uncertain composition of sublimated H2O and its photochemical products H and H2 in Callisto's atmosphere is examined using the Direct Simulaton Monte Carlo (DSMC) method. We focus on two significantly different versions of H2O production in which: (1) the ice and dark, non-ice/ice-poor material are intimately mixed and H2O sublimates at Callisto's warm day-side temperatures (e.g., as in most atmospheric modeling efforts at Callisto to date [1-4]); and (2) the ice and dark, non-ice/ice-poor material are segregated (e.g., consistent with interpretations of images of Callisto's surface taken by Voyager [5, 6] and Galileo [7]) and H2O sublimates at "ice" temperatures [8]. Our 2D molecular kinetic models track the motion H2O, whose sublimation yield varies several orders of magnitude depending on the description of Callisto's surface, its photochemical products H and H2, and a relatively dense O2 component. Whereas H is assumed to react in the regolith on return to the surface, H2 is assumed to thermalize and re-enter the atmosphere. We compare the simulated LOS column densities of H to the detected H corona at Callisto [9], which was suggested to be produced primarily by photodissociation of sublimated H2O. Our goal is to use the corona observations to help constrain the source rate for H2O from Callisto&#8217;s complex surface. References [1] Liang et al., 2005. Atmosphere of Callisto. Journal of Geophysical Research: Planets. [2] Vorburger et al., 2015. Monte-Carlo simulation of Callisto&#8217;s exosphere. Icarus. [3] Hartkorn et al., 2017. Structure and density of Callisto&#8217;s atmosphere from a fluid-kinetic model of its ionosphere: Comparison with Hubble Space Telescope and Galileo observations. Icarus. [4] Carberry Mogan et al., 2021 (under review). A tenuous, collisional atmosphere on Callisto. Icarus. [5] Spencer and Maloney, 1984. Mobility of water ice on Callisto: Evidence and implications. Geophysical Research Letters. [6] Spencer, 1987. Thermal segregation of water ice on the Galilean satellites. Icarus. [7] Moore et al., 1999. Mass movement and landform degradation on the icy Galilean satellites: Results of the Galileo nominal mission. Icarus. [8] Grundy et al., 1999. Near-infrared spectra of icy outer solar system surfaces: Remote determination of H2O ice temperatures. Icarus. [9] Roth et al., 2017. Detection of a hydrogen corona at Callisto. Journal of Geophysical Research: Planets.

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“TNOs are Cool”: A survey of the trans-Neptunian region

Astronomy and Astrophysics ◽

10.1051/0004-6361/201732564 ◽

2018 ◽

Vol 618 ◽

pp. A136 ◽

Cited By ~ 7

Author(s):

E. Vilenius ◽

J. Stansberry ◽

T. Müller ◽

M. Mueller ◽

C. Kiss ◽

...

Keyword(s):

Power Law ◽

Total Mass ◽

Size Range ◽

Family Members ◽

Far Infrared ◽

Effective Diameter ◽

Water Ice ◽

The Family ◽

The Individual ◽

Geometric Albedo

Context. A group of trans-Neptunian objects (TNOs) are dynamically related to the dwarf planet 136108 Haumea. Ten of them show strong indications of water ice on their surfaces, are assumed to have resulted from a collision, and are accepted as the only known TNO collisional family. Nineteen other dynamically similar objects lack water ice absorptions and are hypothesized to be dynamical interlopers. Aims. We have made observations to determine sizes and geometric albedos of six of the accepted Haumea family members and one dynamical interloper. Ten other dynamical interlopers have been measured by previous works. We compare the individual and statistical properties of the family members and interlopers, examining the size and albedo distributions of both groups. We also examine implications for the total mass of the family and their ejection velocities. Methods. We use far-infrared space-based telescopes to observe the target TNOs near their thermal peak and combine these data with optical magnitudes to derive sizes and albedos using radiometric techniques. Using measured and inferred sizes together with ejection velocities, we determine the power-law slope of ejection velocity as a function of effective diameter. Results. The detected Haumea family members have a diversity of geometric albedos ~0.3–0.8, which are higher than geometric albedos of dynamically similar objects without water ice. The median geometric albedo for accepted family members is pV = 0.48−0.18+0.28, compared to 0.08−0.05+0.07 for the dynamical interlopers. In the size range D = 175−300 km, the slope of the cumulative size distribution is q = 3.2−0.4+0.7 for accepted family members, steeper than the q = 2.0 ± 0.6 slope for the dynamical interlopers with D < 500 km. The total mass of Haumea’s moons and family members is 2.4% of Haumea’s mass. The ejection velocities required to emplace them on their current orbits show a dependence on diameter, with a power-law slope of 0.21–0.50.

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Investigating the young solar system analog HD 95086

Astronomy and Astrophysics ◽

10.1051/0004-6361/201732077 ◽

2018 ◽

Vol 617 ◽

pp. A76 ◽

Cited By ~ 18

Author(s):

G. Chauvin ◽

R. Gratton ◽

M. Bonnefoy ◽

A.-M. Lagrange ◽

J. de Boer ◽

...

Keyword(s):

Radial Velocity ◽

Near Infrared ◽

Scattered Light ◽

Spectral Energy Distribution ◽

Giant Planet ◽

Giant Planets ◽

Dual Band ◽

Spectral Energy ◽

Semi Major Axis ◽

Integral Field Spectrograph

Context. HD 95086 (A8V, 17 Myr) hosts a rare planetary system for which a multi-belt debris disk and a giant planet of 4–5 MJup have been directly imaged. Aims. Our study aims to characterize the global architecture of this young system using the combination of radial velocity and direct imaging observations. We want to characterize the physical and orbital properties of HD 95086 b, search for additional planets at short and wide orbits and image the cold outer debris belt in scattered light. Methods. We used HARPS at the ESO 3.6 m telescope to monitor the radial velocity of HD 95086 over two years and investigate the existence of giant planets at less than 3 au orbital distance. With the IRDIS dual-band imager and the IFS integral field spectrograph of SPHERE at VLT, we imaged the faint circumstellar environment beyond 10 au at six epochs between 2015 and 2017. Results. We do not detect additional giant planets around HD 95086. We identify the nature (bound companion or background contaminant) of all point-like sources detected in the IRDIS field of view. None of them correspond to the ones recently discovered near the edge of the cold outer belt by ALMA. HD 95086 b is resolved for the first time in J-band with IFS. Its near-infrared spectral energy distribution is well fitted by a few dusty and/or young L7–L9 dwarf spectral templates. The extremely red 1–4 μm spectral distribution is typical of low-gravity objects at the L/T spectral type transition. The planet’s orbital motion is resolved between January 2015 and May 2017. Together with past NaCo measurements properly re-calibrated, our orbital fitting solutions favor a retrograde low to moderate-eccentricity orbit e = 0.2+0.3−0.2, with a semi-major axis ~52 au corresponding to orbital periods of ~288 yr and an inclination that peaks at i = 141°, which is compatible with a planet-disk coplanar configuration. Finally, we report the detection in polarimetric differential imaging of the cold outer debris belt between 100 and 300 au, consistent in radial extent with recent ALMA 1.3 mm resolved observations.

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Summertime stratospheric processes at northern mid-latitudes: comparisons between MANTRA balloon measurements and the Canadian Middle Atmosphere Model

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-7-11621-2007 ◽

2007 ◽

Vol 7 (4) ◽

pp. 11621-11646 ◽

Cited By ~ 1

Author(s):

S. M. L. Melo ◽

R. Blatherwick ◽

J. Davies ◽

P. Fogal ◽

J. de Grandpré ◽

...

Keyword(s):

Middle Atmosphere ◽

Polar Vortex ◽

Late Summer ◽

Atmospheric Nitrogen ◽

Vertical Diffusion ◽

Trend Assessment ◽

Atmosphere Model ◽

Vertical Diffusion Coefficient ◽

Self Consistency ◽

Balloon Measurements

Abstract. In this paper we report on a study conducted using the Middle Atmospheric Nitrogen TRend Assessment (MANTRA) balloon measurements of stratospheric constituents and temperature and the Canadian Middle Atmosphere Model (CMAM) in order to evaluate the ability of the model to reproduce the measured fields and to thereby test our ability to describe mid-latitude summertime stratospheric processes. The MANTRA measurements used here are vertical profiles of ozone, temperature, N2O, CH4, HNO3, and HCl obtained during four campaigns, involving the launch of both ozonesondes and large balloons from Vanscoy, Saskatchewan, Canada (52° N, 107° W). The campaigns were conducted in August and September 1998, 2000, 2002 and 2004. During late summer at mid-latitudes, the stratosphere is close to photochemical control, providing an ideal scenario for the study reported here. From this analysis we found that: (1) reducing the value for the vertical diffusion coefficient in CMAM to a more physically reasonable value results in the model better reproducing the measured profiles of long-lived species; (2) the existence of compact correlations among the constituents, as expected from independent measurements in the literature and from models, confirms the self-consistency of the MANTRA measurements; and (3) the 1998 ozone measurements show a narrow layer of low ozone centered near 25 km that is consistent with fossil debris from the polar vortex, suggesting that localized springtime ozone anomalies can persist through summer, affecting ozone levels at mid-latitudes.

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