ALMA unveils rings and gaps in the protoplanetary system HD 169142: signatures of two giant protoplanets
TL;DR: In this paper, the authors used ALMA observations of the dust continuum at 1.3 mm, 12 CO, 13 CO, and C18 O J = 2−1 emission from the system HD 169142 (which is observed almost face-on) at an angular resolution of ~ 35 × 20 au, revealing a double-ring structure with an inner ring between 20−35 au and an outer ring between 56−83 au.
Abstract: The protoplanetary system HD 169142 is one of the few cases where a potential candidate protoplanet has recently been detected by direct imaging in the near-infrared. To study the interaction between the protoplanet and the disk itself, observations of the gas and dust surface density structure are needed. This paper reports new ALMA observations of the dust continuum at 1.3 mm, 12 CO, 13 CO, and C18 O J = 2−1 emission from the system HD 169142 (which is observed almost face-on) at an angular resolution of ~ (~35 × 20 au). The dust continuum emission reveals a double-ring structure with an inner ring between (~20−35 au) and an outer ring between (~56−83 au). The size and position of the inner ring is in good agreement with previous polarimetric observations in the near-infrared and is consistent with dust trapping by a massive planet. No dust emission is detected inside the inner dust cavity (R ≲ 20 au) or within the dust gap (~35−56 au) down to the noise level. In contrast, the channel maps of the J = 2−1 line of the three CO isotopologs reveal gas inside the dust cavity and dust gap. The gaseous disk is also much larger than the compact dust emission; it extends to ~1 (~180 au) in radius. This difference and the sharp drop of the continuum emission at large radii point to radial drift of large dust grains (>μ m size). Using the thermo-chemical disk code dali, we modeled the continuum and the CO isotopolog emission to quantitatively measure the gas and dust surface densities. The resulting gas surface density is reduced by a factor of ~30−40 inward of the dust gap. The gas and dust distribution indicate that two giant planets shape the disk structure through dynamical clearing (dust cavity and gap) and dust trapping (double-ring dust distribution).
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Harvard University1, University of Chile2, Rice University3, Heidelberg University4, Pontifical Catholic University of Chile5, University of Nevada, Las Vegas6, Ludwig Maximilian University of Munich7, Tsinghua University8, University of Grenoble9, Wesleyan University10, California State University, Northridge11
TL;DR: The Disk Substructures at High Angular Resolution Project (DSHARP) as mentioned in this paper was the first large-scale project to find and characterize substructures in the spatial distributions of solid particles for a sample of 20 nearby protoplanetary disks, using very high resolution (similar to 0'' 035 or 5 au, FWHM) observations of their 240 GHz (1.25 mm) continuum emission.
Abstract: We introduce the Disk Substructures at High Angular Resolution Project (DSHARP), one of the initial Large Programs conducted with the Atacama Large Millimeter/submillimeter Array (ALMA). The primary goal of DSHARP is to find and characterize substructures in the spatial distributions of solid particles for a sample of 20 nearby protoplanetary disks, using very high resolution (similar to 0.'' 035, or 5 au, FWHM) observations of their 240 GHz (1.25 mm) continuum emission. These data provide a first homogeneous look at the small-scale features in disks that are directly relevant to the planet formation process, quantifying their prevalence, morphologies, spatial scales, spacings, symmetry, and amplitudes, for targets with a variety of disk and stellar host properties. We find that these substructures are ubiquitous in this sample of large, bright disks. They are most frequently manifested as concentric, narrow emission rings and depleted gaps, although large-scale spiral patterns and small arc-shaped azimuthal asymmetries are also present in some cases. These substructures are found at a wide range of disk radii (from a few astronomical units to more than 100 au), are usually compact (less than or similar to 10 au), and show a wide range of amplitudes (brightness contrasts). Here we discuss the motivation for the project, describe the survey design and the sample properties, detail the observations and data calibration, highlight some basic results, and provide a general overview of the key conclusions that are presented in more detail in a series of accompanying articles. The DSHARP data-including visibilities, images, calibration scripts, and more-are released for community use at https://almascience.org/alma-data/lp/DSHARP.
822 citations
Cites background from "ALMA unveils rings and gaps in the ..."
...…including azimuthal asymmetries (Casassus et al. 2013; van der Marel et al. 2013; Isella et al. 2013; Pérez et al. 2014), additional rings (Fedele et al. 2017; van der Plas et al. 2017), warped geometries (and/or radial inflows; Rosenfeld et al. 2012, 2014; Marino et al. 2015; Casassus…...
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Peking University1, University of Arizona2, Leiden University3, University of Leicester4, University of Cambridge5, University of Milan6, Vassar College7, Smith College8, University of Grenoble9, University of Victoria10, Chinese Academy of Sciences11, Max Planck Society12, Rice University13, University of Paris14, European Southern Observatory15, University of Chicago16, INAF17, Space Telescope Science Institute18, Ames Research Center19
TL;DR: In this article, the authors identify the most frequently revealed substructure in ALMA dust observations of protoplanetary disks, and measure their properties to investigate how they form, including axisymmetric rings and gaps.
Abstract: Rings are the most frequently revealed substructure in ALMA dust observations of protoplanetary disks, but their origin is still hotly debated. In this paper, we identify dust substructures in 12 disks and measure their properties to investigate how they form. This subsample of disks is selected from a high-resolution ($\sim0.12''$) ALMA 1.33 mm survey of 32 disks in the Taurus star-forming region, which was designed to cover a wide range of sub-mm brightness and to be unbiased to previously known substructures. While axisymmetric rings and gaps are common within our sample, spiral patterns and high contrast azimuthal asymmetries are not detected. Fits of disk models to the visibilities lead to estimates of the location and shape of gaps and rings, the flux in each disk component, and the size of the disk. The dust substructures occur across a wide range of stellar mass and disk brightness. Disks with multiple rings tend to be more massive and more extended. The correlation between gap locations and widths, the intensity contrast between rings and gaps, and the separations of rings and gaps could all be explained if most gaps are opened by low-mass planets (super-Earths and Neptunes) in the condition of low disk turbulence ($\alpha=10^{-4}$). The gap locations are not well correlated with the expected locations of CO and N$_2$ ice lines, so condensation fronts are unlikely to be a universal mechanism to create gaps and rings, though they may play a role in some cases.
395 citations
Harvard University1, Heidelberg University2, Rice University3, University of Chile4, Pontifical Catholic University of Chile5, University of Nevada, Las Vegas6, Tsinghua University7, University of Grenoble8, Ludwig Maximilian University of Munich9, Wesleyan University10, California State University, Northridge11
TL;DR: In this article, the authors present a systematic analysis of annular substructures in the 18 single-disk systems targeted in this survey, and find that annular structures can occur at virtually any radius where millimeter continuum emission is detected and range in widths from a few astronomical units to tens of astronomical units.
Abstract: The Disk Substructures at High Angular Resolution Project (DSHARP) used ALMA to map the 1.25 mm continuum of protoplanetary disks at a spatial resolution of similar to 5 au. We present a systematic analysis of annular substructures in the 18 single-disk systems targeted in this survey. No dominant architecture emerges from this sample;instead, remarkably diverse morphologies are observed. Annular substructures can occur at virtually any radius where millimeter continuum emission is detected and range in widths from a few astronomical units to tens of astronomical units. Intensity ratios between gaps and adjacent rings range from near-unity to just a few percent. In a minority of cases, annular substructures coexist with other types of substructures, including spiral arms (3/18) and crescent-like azimuthal asymmetries (2/18). No clear trend is observed between the positions of the substructures and stellar host properties. In particular, the absence of an obvious association with stellar host luminosity (and hence the disk thermal structure) suggests that substructures do not occur preferentially near major molecular snowlines. Annular substructures like those observed in DSHARP have long been hypothesized to be due to planet-disk interactions. A few disks exhibit characteristics particularly suggestive of this scenario, including substructures in possible mean-motion resonance and "double gap" features reminiscent of hydrodynamical simulations of multiple gaps opened by a planet in a low-viscosity disk.
376 citations
Cites background from "ALMA unveils rings and gaps in the ..."
...Colloquially, the “bright” and “dark” features are often referred to as “rings” and “gaps,” respectively (e.g., ALMA Partnership et al. 2015; Isella et al. 2016; Fedele et al. 2017)....
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...Observed features also include annular gaps and rings, spiral arms, and azimuthal asymmetries (e.g., Fedele et al. 2017; Dong et al. 2018b)....
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...…Long et al. 2018a), but have also been observed in scattered light tracing sub-micron-sized dust grains in the disk atmosphere (e.g., van Boekel et al. 2017; Avenhaus et al. 2018; Muro-Arena et al. 2018) and in molecular emission (e.g., Isella et al. 2016; Fedele et al. 2017; Teague et al. 2017)....
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TL;DR: In this article, the authors test the hypothesis that these dust rings are caused by dust trapping in radial pressure bumps, and if confirmed, put constraints on the physics of the dust trapping mechanism.
Abstract: A large fraction of the protoplanetary disks observed with ALMA display multiple well-defined and nearly perfectly circular rings in the continuum, in many cases with substantial peak-to-valley contrast. The DSHARP campaign shows that several of these rings are very narrow in radial extent. In this Letter we test the hypothesis that these dust rings are caused by dust trapping in radial pressure bumps, and if confirmed, put constraints on the physics of the dust trapping mechanism. We model this process analytically in 1D, assuming axisymmetry. By comparing this model to the data, we find that all rings are consistent with dust trapping. Based on a plausible model of the dust temperature we find that several rings are narrower than the pressure scale height, providing strong evidence for dust trapping. The rings have peak absorption optical depth in the range between 0.2 and 0.5. The dust masses stored in each of these rings is of the order of tens of Earth masses, though much ambiguity remains due to the uncertainty of the dust opacities. The dust rings are dense enough to potentially trigger the streaming instability, but our analysis cannot give proof of this mechanism actually operating. Our results show, however, that the combination of very low alpha(turb) > 0.1 cm grain can be excluded by the data for all the rings studied in this Letter.
270 citations
Cites background from "ALMA unveils rings and gaps in the ..."
...…multi-ringed disk observation of HL Tau (ALMA Partnership et al. 2015) a number of such multi-ringed disks have been detected (Andrews et al. 2016; Isella et al. 2016; Cieza et al. 2017; Fedele et al. 2017, 2018; Dipierro et al. 2018; van Terwisga et al. 2018; Clarke et al. 2018; Long et al. 2018)....
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TL;DR: In this paper, the first kinematical detection of embedded protoplanets within a protoplanetary disk using archival Atacama Large Millimetre Array (ALMA) observations of HD.
Abstract: We present the first kinematical detection of embedded protoplanets within a protoplanetary disk. Using archival Atacama Large Millimetre Array (ALMA) observations of HD. 163296, we demonstrate a new technique to measure the rotation curves of CO isotopologue emission to sub-percent precision relative to the Keplerian rotation. These rotation curves betray substantial deviations caused by local perturbations in the radial pressure gradient, likely driven by gaps carved in the gas surface density by Jupiter-mass planets. Comparison with hydrodynamic simulations shows excellent agreement with the gas rotation profile when the disk surface density is perturbed by two Jupiter-mass planets at 83 and 137 au. As the rotation of the gas is dependent upon the pressure of the total gas component, this method provides a unique probe of the gas surface density profile without incurring significant uncertainties due to gas-to-dust ratios or local chemical abundances that plague other methods. Future analyses combining both methods promise to provide the most accurate and robust measures of embedded planetary mass. Furthermore, this method provides a unique opportunity to explore wide-separation planets beyond the mm. continuum edge and to trace the gas pressure profile essential in modeling grain evolution in disks.
203 citations
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TL;DR: The first Gaia data release, Gaia DR1 as mentioned in this paper, consists of the positions, parallaxes, and mean proper motions for about 2 million of the brightest stars in common with the Hipparcos and Tycho-2 catalogues.
Abstract: At about 1000 days after the launch of Gaia we present the first Gaia data release, Gaia DR1, consisting of astrometry and photometry for over 1 billion sources brighter than magnitude 20.7. We summarize Gaia DR1 and provide illustrations of the scientific quality of the data, followed by a discussion of the limitations due to the preliminary nature of this release. Gaia DR1 consists of: a primary astrometric data set which contains the positions, parallaxes, and mean proper motions for about 2 million of the brightest stars in common with the Hipparcos and Tycho-2 catalogues and a secondary astrometric data set containing the positions for an additional 1.1 billion sources. The second component is the photometric data set,consisting of mean G-band magnitudes for all sources. The G-band light curves and the characteristics of ~3000 Cepheid and RR Lyrae stars, observed at high cadence around the south ecliptic pole, form the third component. For the primary astrometric data set the typical uncertainty is about 0.3 mas for the positions and parallaxes, and about 1 mas/yr for the proper motions. A systematic component of ~0.3 mas should be added to the parallax uncertainties. For the subset of ~94000 Hipparcos stars in the primary data set, the proper motions are much more precise at about 0.06 mas/yr. For the secondary astrometric data set, the typical uncertainty of the positions is ~10 mas. The median uncertainties on the mean G-band magnitudes range from the mmag level to ~0.03 mag over the magnitude range 5 to 20.7. Gaia DR1 represents a major advance in the mapping of the heavens and the availability of basic stellar data that underpin observational astrophysics. Nevertheless, the very preliminary nature of this first Gaia data release does lead to a number of important limitations to the data quality which should be carefully considered before drawing conclusions from the data.
2,256 citations
Anthony G. A. Brown1, Antonella Vallenari2, T. Prusti2, J. H. J. de Bruijne3 +587 more•Institutions (89)
TL;DR: The first Gaia data release, Gaia DR1 as discussed by the authors, consists of three components: a primary astrometric data set which contains the positions, parallaxes, and mean proper motions for about 2 million of the brightest stars in common with the Hipparcos and Tycho-2 catalogues.
Abstract: Context. At about 1000 days after the launch of Gaia we present the first Gaia data release, Gaia DR1, consisting of astrometry and photometry for over 1 billion sources brighter than magnitude 20.7. Aims: A summary of Gaia DR1 is presented along with illustrations of the scientific quality of the data, followed by a discussion of the limitations due to the preliminary nature of this release. Methods: The raw data collected by Gaia during the first 14 months of the mission have been processed by the Gaia Data Processing and Analysis Consortium (DPAC) and turned into an astrometric and photometric catalogue. Results: Gaia DR1 consists of three components: a primary astrometric data set which contains the positions, parallaxes, and mean proper motions for about 2 million of the brightest stars in common with the Hipparcos and Tycho-2 catalogues - a realisation of the Tycho-Gaia Astrometric Solution (TGAS) - and a secondary astrometric data set containing the positions for an additional 1.1 billion sources. The second component is the photometric data set, consisting of mean G-band magnitudes for all sources. The G-band light curves and the characteristics of 3000 Cepheid and RR Lyrae stars, observed at high cadence around the south ecliptic pole, form the third component. For the primary astrometric data set the typical uncertainty is about 0.3 mas for the positions and parallaxes, and about 1 mas yr-1 for the proper motions. A systematic component of 0.3 mas should be added to the parallax uncertainties. For the subset of 94 000 Hipparcos stars in the primary data set, the proper motions are much more precise at about 0.06 mas yr-1. For the secondary astrometric data set, the typical uncertainty of the positions is 10 mas. The median uncertainties on the mean G-band magnitudes range from the mmag level to0.03 mag over the magnitude range 5 to 20.7. Conclusions: Gaia DR1 is an important milestone ahead of the next Gaia data release, which will feature five-parameter astrometry for all sources. Extensive validation shows that Gaia DR1 represents a major advance in the mapping of the heavens and the availability of basic stellar data that underpin observational astrophysics. Nevertheless, the very preliminary nature of this first Gaia data release does lead to a number of important limitations to the data quality which should be carefully considered before drawing conclusions from the data.
2,174 citations
2,001 citations
"ALMA unveils rings and gaps in the ..." refers background in this paper
...…gas is primarily due to an optical depth effect (e.g., Dutrey et al. 1996), but the sharp drop in dust emission hints at the radial drift of the dust particles (Weidenschilling 1977; Birnstiel & Andrews 2014), with the grains trapped at local pressure maxima induced by the planet-disk interaction....
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TL;DR: In this paper, a survey for 1.3 mm radiation toward 86 stars in the Taurus-Auriga dark clouds, including classical T Tauri stars, stars in T associations, and a few weak emission-line stars or naked T-Tauri stars was conducted.
Abstract: Results are presented from a survey for 1.3 mm radiation toward 86 stars in the Taurus-Auriga dark clouds, including classical T Tauri stars, stars in T associations, and a few weak emission-line stars or naked T Tauri stars. The results show that 42 percent of the stars have detectable emission from small particles. The aggregate particle masses are found to be between 0.00001 and 0.01 solar mass, suggesting total disk masses between 0.001 and 1 solar mass. For several source between 1.3 and 2.7 mm, the spectral indices indicate that the particle emissivities are weaker functions of frequency, compared to the usual case of interstellar grains. Particle growth via adhesion in the dense disks is proposed to explain this result. The results show that disks more massive than the minimum mass of the protosolar system commonly accompany the birth of solar-mass stars, indicating that planetary systems are probably common in the Galaxy. 59 refs.
1,657 citations
"ALMA unveils rings and gaps in the ..." refers background in this paper
...…= S ν,gap d2 kν Bν (Tdust,gap) , (1) where S ν,gap (Jy) is the upper limit on the flux density, d (cm) the distance, kν = 2 (cm2 g−1) the mass absorption coefficient at 230 GHz (Beckwith et al. 1990), Tdust,gap (K) the dust temperature inside the gap and Bν (Jy sr−1) the Planck function....
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TL;DR: In this article, a comprehensive survey of the stellar content of the OB associations within 1 kpc from the Sun is presented, based on Hipparcos positions, proper motions, and parallaxes.
Abstract: A comprehensive census of the stellar content of the OB associations within 1 kpc from the Sun is presented, based on Hipparcos positions, proper motions, and parallaxes. It is a key part of a long-term project to study the formation, structure, and evolution of nearby young stellar groups and related star-forming regions. OB associations are unbound moving groups, which can be detected kinematically because of their small internal velocity dispersion. The nearby associations have a large extent on the sky, which traditionally has limited astrometric membership determination to bright stars (V 6 mag), with spectral types earlier than ~B5. The Hipparcos measurements allow a major improvement in this situation. Moving groups are identified in the Hipparcos Catalog by combining de Bruijne's refurbished convergent point method with the Spaghetti method of Hoogerwerf & Aguilar. Astrometric members are listed for 12 young stellar groups, out to a distance of ~650 pc. These are the three subgroups Upper Scorpius, Upper Centaurus Lupus, and Lower Centaurus Crux of Sco OB2, as well as Vel OB2, Tr 10, Col 121, Per OB2, α Persei (Per OB3), Cas–Tau, Lac OB1, Cep OB2, and a new group in Cepheus, designated as Cep OB6. The selection procedure corrects the list of previously known astrometric and photometric B- and A-type members in these groups and identifies many new members, including a significant number of F stars, as well as evolved stars, e.g., the Wolf-Rayet stars γ2 Vel (WR 11) in Vel OB2 and EZ CMa (WR 6) in Col 121, and the classical Cepheid δ Cep in Cep OB6. Membership probabilities are given for all selected stars. Monte Carlo simulations are used to estimate the expected number of interloper field stars. In the nearest associations, notably in Sco OB2, the later-type members include T Tauri objects and other stars in the final pre–main-sequence phase. This provides a firm link between the classical high-mass stellar content and ongoing low-mass star formation. Detailed studies of these 12 groups, and their relation to the surrounding interstellar medium, will be presented elsewhere. Astrometric evidence for moving groups in the fields of R CrA, CMa OB1, Mon OB1, Ori OB1, Cam OB1, Cep OB3, Cep OB4, Cyg OB4, Cyg OB7, and Sct OB2, is inconclusive. OB associations do exist in many of these regions, but they are either at distances beyond ~500 pc where the Hipparcos parallaxes are of limited use, or they have unfavorable kinematics, so that the group proper motion does not distinguish it from the field stars in the Galactic disk. The mean distances of the well-established groups are systematically smaller than the pre-Hipparcos photometric estimates. While part of this may be caused by the improved membership lists, a recalibration of the upper main sequence in the Hertzsprung-Russell diagram may be called for. The mean motions display a systematic pattern, which is discussed in relation to the Gould Belt. Six of the 12 detected moving groups do not appear in the classical list of nearby OB associations. This is sometimes caused by the absence of O stars, but in other cases a previously known open cluster turns out to be (part of) an extended OB association. The number of unbound young stellar groups in the solar neighborhood may be significantly larger than thought previously.
1,354 citations