DSpace Angular :: Browsing by Author "Sierra, Anibal"

Browsing by Author "Sierra, Anibal"

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A Dust-trapping Ring in the Planet-hosting Disk of Elias 2-24
(2024) Carvalho, Adolfo S.; Perez, Laura M.; Sierra, Anibal; Mellado, Maria Jesus; Hillenbrand, Lynne A.; Andrews, Sean; Benisty, Myriam; Birnstiel, Tilman; Carpenter, John M.; Guzman, Viviana V.; Huang, Jane; Isella, Andrea; Kurtovic, Nicolas; Ricci, Luca; Wilner, David J.
Rings and gaps are among the most widely observed forms of substructure in protoplanetary disks. A gap-ring pair may be formed when a planet carves a gap in the disk, which produces a local pressure maximum following the gap that traps inwardly drifting dust grains and appears as a bright ring owing to the enhanced dust density. A dust-trapping ring would provide a promising environment for solid growth and possibly planetesimal production via the streaming instability. We present evidence of dust trapping in the bright ring of the planet-hosting disk Elias 2-24, from the analysis of 1.3 and 3 mm Atacama Large Millimeter/submillimeter Array observations at high spatial resolution (0.'' 029, 4.0 au). We leverage the high spatial resolution to demonstrate that larger grains are more efficiently trapped and place constraints on the local turbulence (8 x 10(-4) < alpha( turb) < 0.03) and the gas-to-dust ratio (Sigma (g) /Sigma (d) < 30) in the ring. Using a scattering-included marginal probability analysis, we measure a total dust disk mass of M-dust=13.8(-0.5)+0.7x10(-4)M(circle dot) . We also show that at the orbital radius of the proposed perturber the gap is cleared of material down to a flux contrast of 10(-3) of the peak flux in the disk.
Constraints on the Physical Origin of Large Cavities in Transition Disks from Multiwavelength Dust Continuum Emission
(2024) Sierra, Anibal; Perez, Laura M.; Sotomayor, Benjamin; Benisty, Myriam; Chandler, Claire J.; Andrews, Sean; Carpenter, John; Henning, Thomas; Testi, Leonardo; Ricci, Luca; Wilner, David
The physical origin of the large cavities observed in transition disks is to date still unclear. Different physical mechanisms (e.g., a companion, dead zones, enhanced grain growth) produce disk cavities of different depth, and the expected spatial distribution of gas and solids in each mechanism is not the same. In this work, we analyze the multiwavelength interferometric visibilities of dust continuum observations obtained with Atacama Large Millimeter/submillimeter Array and Very Large Array for six transition disks: CQTau, UXTau A, LkCa15, RXJ1615, SR24S, and DMTau, and calculate brightness radial profiles, where diverse emission morphology is revealed at different wavelengths. The multiwavelength data are used to model the spectral energy distribution and compute constraints on the radial profile of the dust surface density, maximum grain size, and dust temperature in each disk. They are compared with the observational signatures expected from various physical mechanisms responsible for disk cavities. The observational signatures suggest that the cavities observed in the disks around UXTau A, LkCa15, and RXJ1615 could potentially originate from a dust trap created by a companion. Conversely, in the disks around CQTau, SR24S, DMTau, the origin of the cavity remains unclear, although it is compatible with a pressure bump and grain growth within the cavity.
Molecules with ALMA at Planet-forming Scales (MAPS). I. Program Overview and Highlights
(2021) Oberg, Karin, I; Guzman, Viviana V.; Walsh, Catherine; Aikawa, Yuri; Bergin, Edwin A.; Law, Charles J.; Loomis, Ryan A.; Alarcon, Felipe; Andrews, Sean M.; Bae, Jaehan; Bergner, Jennifer B.; Boehler, Yann; Booth, Alice S.; Bosman, Arthur D.; Calahan, Jenny K.; Cataldi, Gianni; Cleeves, L. Ilsedore; Czekala, Ian; Furuya, Kenji; Huang, Jane; Ilee, John D.; Kurtovic, Nicolas T.; Le Gal, Romane; Liu, Yao; Long, Feng; Menard, Francois; Nomura, Hideko; Perez, Laura M.; Qi, Chunhua; Schwarz, Kamber R.; Sierra, Anibal; Teague, Richard; Tsukagoshi, Takashi; Yamato, Yoshihide; van't Hoff, Merel L. R.; Waggoner, Abygail R.; Wilner, David J.; Zhang, Ke
Planets form and obtain their compositions in dust- and gas-rich disks around young stars, and the outcome of this process is intimately linked to the disk chemical properties. The distributions of molecules across disks regulate the elemental compositions of planets, including C/N/O/S ratios and metallicity (O/H and C/H), as well as access to water and prebiotically relevant organics. Emission from molecules also encodes information on disk ionization levels, temperature structures, kinematics, and gas surface densities, which are all key ingredients of disk evolution and planet formation models. The Molecules with ALMA at Planet-forming Scales (MAPS) ALMA Large Program was designed to expand our understanding of the chemistry of planet formation by exploring disk chemical structures down to 10 au scales. The MAPS program focuses on five disks-around IM Lup, GM Aur, AS 209, HD 163296, and MWC 480-in which dust substructures are detected and planet formation appears to be ongoing. We observed these disks in four spectral setups, which together cover similar to 50 lines from over 20 different species. This paper introduces the Astrophysical Journal Supplement's MAPS Special Issue by presenting an overview of the program motivation, disk sample, observational details, and calibration strategy. We also highlight key results, including discoveries of links between dust, gas, and chemical substructures, large reservoirs of nitriles and other organics in the inner disk regions, and elevated C/O ratios across most disks. We discuss how this collection of results is reshaping our view of the chemistry of planet formation.
Molecules with ALMA at Planet-forming Scales (MAPS). III. Characteristics of Radial Chemical Substructures
(2021) Law, Charles J.; Loomis, Ryan A.; Teague, Richard; Oberg, Karin, I; Czekala, Ian; Andrews, Sean M.; Huang, Jane; Aikawa, Yuri; Alarcon, Felipe; Bae, Jaehan; Bergin, Edwin A.; Bergner, Jennifer B.; Boehler, Yann; Booth, Alice S.; Bosman, Arthur D.; Calahan, Jenny K.; Cataldi, Gianni; Cleeves, L. Ilsedore; Furuya, Kenji; Guzman, Viviana V.; Ilee, John D.; Le Gal, Romane; Liu, Yao; Long, Feng; Menard, Francois; Nomura, Hideko; Qi, Chunhua; Schwarz, Kamber R.; Sierra, Anibal; Tsukagoshi, Takashi; Yamato, Yoshihide; van't Hoff, Merel L. R.; Walsh, Catherine; Wilner, David J.; Zhang, Ke
The Molecules with ALMA at Planet-forming Scales (MAPS) Large Program provides a detailed, high-resolution (similar to 10-20 au) view of molecular line emission in five protoplanetary disks at spatial scales relevant for planet formation. Here we present a systematic analysis of chemical substructures in 18 molecular lines toward the MAPS sources: IM Lup, GM Aur, AS 209, HD 163296, and MWC 480. We identify more than 200 chemical substructures, which are found at nearly all radii where line emission is detected. A wide diversity of radial morphologies-including rings, gaps, and plateaus-is observed both within each disk and across the MAPS sample. This diversity in line emission profiles is also present in the innermost 50 au. Overall, this suggests that planets form in varied chemical environments both across disks and at different radii within the same disk. Interior to 150 au, the majority of chemical substructures across the MAPS disks are spatially coincident with substructures in the millimeter continuum, indicative of physical and chemical links between the disk midplane and warm, elevated molecular emission layers. Some chemical substructures in the inner disk and most chemical substructures exterior to 150 au cannot be directly linked to dust substructure, however, which indicates that there are also other causes of chemical substructures, such as snowlines, gradients in UV photon fluxes, ionization, and radially varying elemental ratios. This implies that chemical substructures could be developed into powerful probes of different disk characteristics, in addition to influencing the environments within which planets assemble. This paper is part of the MAPS special issue of the Astrophysical Journal Supplement.
Molecules with ALMA at Planet-forming Scales (MAPS). V. CO Gas Distributions
(2021) Zhang, Ke; Booth, Alice S.; Law, Charles J.; Bosman, Arthur D.; Schwarz, Kamber R.; Bergin, Edwin A.; Oberg, Karin, I; Andrews, Sean M.; Guzman, Viviana V.; Walsh, Catherine; Qi, Chunhua; van 't Hoff, Merel L. R.; Long, Feng; Wilner, David J.; Huang, Jane; Czekala, Ian; Ilee, John D.; Cataldi, Gianni; Bergner, Jennifer B.; Aikawa, Yuri; Teague, Richard; Bae, Jaehan; Loomis, Ryan A.; Calahan, Jenny K.; Alarcon, Felipe; Menard, Francois; Le Gal, Romane; Sierra, Anibal; Yamato, Yoshihide; Nomura, Hideko; Tsukagoshi, Takashi; Perez, Laura M.; Trapman, Leon; Liu, Yao; Furuya, Kenji
Here we present high-resolution (15-24 au) observations of CO isotopologue lines from the Molecules with ALMA on Planet-forming Scales (MAPS) ALMA Large Program. Our analysis employs observations of the (J = 2-1) and (1-0) lines of (CO)-C-13 and (CO)-O-18 and the (J = 1-0) line of (CO)-O-17 for five protoplanetary disks. We retrieve CO gas density distributions, using three independent methods: (1) a thermochemical modeling framework based on the CO data, the broadband spectral energy distribution, and the millimeter continuum emission; (2) an empirical temperature distribution based on optically thick CO lines; and (3) a direct fit to the (CO)-O-17 hyperfine lines. Results from these methods generally show excellent agreement. The CO gas column density profiles of the five disks show significant variations in the absolute value and the radial shape. Assuming a gas-to-dust mass ratio of 100, all five disks have a global CO-to-H-2 abundance 10-100 times lower than the interstellar medium ratio. The CO gas distributions between 150 and 400 au match well with models of viscous disks, supporting the long-standing theory. CO gas gaps appear to be correlated with continuum gap locations, but some deep continuum gaps do not have corresponding CO gaps. The relative depths of CO and dust gaps are generally consistent with predictions of planet-disk interactions, but some CO gaps are 5-10 times shallower than predictions based on dust gaps. This paper is part of the MAPS special issue of the Astrophysical Journal Supplement.
Molecules with ALMA at Planet-forming Scales (MAPS). XIV. Revealing Disk Substructures in Multiwavelength Continuum Emission
(2021) Sierra, Anibal; Perez, Laura M.; Zhang, Ke; Law, Charles J.; Guzman, Viviana V.; Qi, Chunhua; Bosman, Arthur D.; Oberg, Karin, I; Andrews, Sean M.; Long, Feng; Teague, Richard; Booth, Alice S.; Walsh, Catherine; Wilner, David J.; Menard, Francois; Cataldi, Gianni; Czekala, Ian; Bae, Jaehan; Huang, Jane; Bergner, Jennifer B.; Ilee, John D.; Benisty, Myriam; Le Gal, Romane; Loomis, Ryan A.; Tsukagoshi, Takashi; Liu, Yao; Yamato, Yoshihide; Aikawa, Yuri
Constraining dust properties of planet-forming disks via high-angular-resolution observations is fundamental to understanding how solids are trapped in substructures and how dust growth may be favored or accelerated therein. We use ALMA dust continuum observations of the Molecules with ALMA at Planet-forming Scales (MAPS) disks and explore a large parameter space to constrain the radial distribution of solid mass and maximum grain size in each disk, including or excluding dust scattering. In the nonscattering model, the dust surface density and maximum grain size profiles decrease from the inner disks to the outer disks, with local maxima at the bright ring locations, as expected from dust trapping models. The inferred maximum grain sizes from the inner to outer disks decrease from 1 cm to 1 mm. For IM Lup, HD 163296, and MWC 480 in the scattering model, two solutions are compatible with their observed inner disk emission: one solution corresponding to a maximum grain size of a few millimeters (similar to the nonscattering model), and the other corresponding to a size of a few hundred micrometers. Based on the estimated Toomre parameter, only IM Lup-which shows a prominent spiral morphology in millimeter dust-is found to be gravitationally unstable. The estimated maximum Stokes number in all the disks lies between 0.01 and 0.3, and the estimated turbulence parameters in the rings of AS 209 and HD 163296 are close to the threshold where dust growth is limited by turbulent fragmentation. This paper is part of the MAPS special issue of the Astrophysical Journal Supplement.
Molecules with ALMA at Planet-forming Scales (MAPS). XV. Tracing Protoplanetary Disk Structure within 20 au
(2021) Bosman, Arthur D.; Bergin, Edwin A.; Loomis, Ryan A.; Andrews, Sean M.; Van't Hoff, Merel L. R.; Teague, Richard; Oberg, Karin, I; Guzman, Viviana V.; Walsh, Catherine; Aikawa, Yuri; Alarcon, Felipe; Bae, Jaehan; Bergner, Jennifer B.; Booth, Alice S.; Cataldi, Gianni; Cleeves, L. Ilsedore; Czekala, Ian; Huang, Jane; Ilee, John D.; Law, Charles J.; Le Gal, Romane; Liu, Yao; Long, Feng; Menard, Francois; Nomura, Hideko; Perez, Laura M.; Qi, Chunhua; Schwarz, Kamber R.; Sierra, Anibal; Tsukagoshi, Takashi; Yamato, Yoshihide; Wilner, David J.; Zhang, Ke
Constraining the distribution of gas and dust in the inner 20 au of protoplanetary disks is difficult. At the same time, this region is thought to be responsible for most planet formation, especially around the water ice line at 3-10 au. Under the assumption that the gas is in a Keplerian disk, we use the exquisite sensitivity of the Molecules with ALMA at Planet-forming Scales (MAPS) ALMA large program to construct radial surface brightness profiles with a similar to 3 au effective resolution for the CO isotopologue J = 2-1 lines using the line velocity profile. IM Lup reveals a central depression in (CO)-C-13 and (CO)-O-18 that is ascribed to a pileup of similar to 500 M (circle plus) of dust in the inner 20 au, leading to a gas-to-dust ratio of around <10. This pileup is consistent with an efficient drift of grains (greater than or similar to 100 M (circle plus) Myr(-1)) and a local gas-to-dust ratio that suggests that the streaming instability could be active. The CO isotopologue emission in the GM Aur disk is consistent with a small (similar to 15 au), strongly depleted gas cavity within the similar to 40 au dust cavity. The radial surface brightness profiles for both the AS 209 and HD 163296 disks show a local minimum and maximum in the (CO)-O-18 emission at the location of a known dust ring (similar to 14 au) and gap (similar to 10 au), respectively. This indicates that the dust ring has a low gas-to-dust ratio (>10) and that the dust gap is gas-rich enough to have optically thick (CO)-O-18. This paper is part of the MAPS special issue of the Astrophysical Journal Supplement.
Molecules with ALMA at Planet-forming Scales (MAPS). XVIII. Kinematic Substructures in the Disks of HD 163296 and MWC 480
(2021) Teague, Richard; Bae, Jaehan; Aikawa, Yuri; Andrews, Sean M.; Bergin, Edwin A.; Bergner, Jennifer B.; Boehler, Yann; Booth, Alice S.; Bosman, Arthur D.; Cataldi, Gianni; Czekala, Ian; Guzman, Viviana V.; Huang, Jane; Ilee, John D.; Law, Charles J.; Le Gal, Romane; Long, Feng; Loomis, Ryan A.; Menard, Francois; Oberg, Karin, I; Perez, Laura M.; Schwarz, Kamber R.; Sierra, Anibal; Walsh, Catherine; Wilner, David J.; Yamato, Yoshihide; Zhang, Ke
We explore the dynamical structure of the protoplanetary disks surrounding HD 163296 and MWC 480 as part of the Molecules with ALMA at Planet-forming Scales (MAPS) large program. Using the J = 2-1 transitions of (CO)-C-12, (CO)-C-13, and (CO)-O-18 imaged at spatial resolutions of similar to 0.'' 15 and with a channel spacing of 200 m s(-1), we find perturbations from Keplerian rotation in the projected velocity fields of both disks (less than or similar to 5% of the local Keplerian velocity), suggestive of large-scale (tens of astronomical units in size), coherent flows. By accounting for the azimuthal dependence on the projection of the velocity field, the velocity fields were decomposed into azimuthally averaged orthogonal components, v ( phi ), v ( r ), and v ( z ). Using the optically thick (CO)-C-12 emission as a probe of the gas temperature, local variations of approximate to 3 K (approximate to 5% relative changes) were observed and found to be associated with the kinematic substructures. The MWC 480 disk hosts a suite of tightly wound spiral arms. The spirals arms, in conjunction with the highly localized perturbations in the gas velocity structure (kinematic planetary signatures), indicate a giant planet, similar to 1 M (Jup), at a radius of approximate to 245 au. In the disk of HD 163296, the kinematic substructures were consistent with previous studies of Pinte et al. and Teague et al. advocating for multiple similar to 1 M (Jup) planets embedded in the disk. These results demonstrate that molecular line observations that characterize the dynamical structure of disks can be used to search for the signatures of embedded planets. This paper is part of the MAPS special issue of the Astrophysical Journal Supplement.
Molecules with ALMA at Planet-forming Scales (MAPS): A Circumplanetary Disk Candidate in Molecular-line Emission in the AS 209 Disk
(2022) Bae, Jaehan; Teague, Richard; Andrews, Sean M.; Benisty, Myriam; Facchini, Stefano; Galloway-Sprietsma, Maria; Loomis, Ryan A.; Aikawa, Yuri; Alarcon, Felipe; Bergin, Edwin; Bergner, Jennifer B.; Booth, Alice S.; Cataldi, Gianni; Cleeves, L. Ilsedore; Czekala, Ian; Guzman, Viviana V.; Huang, Jane; Ilee, John D.; Kurtovic, Nicolas T.; Law, Charles J.; Le Gal, Romane; Liu, Yao; Long, Feng; Menard, Francois; Oberg, Karin, I; Perez, Laura M.; Qi, Chunhua; Schwarz, Kamber R.; Sierra, Anibal; Walsh, Catherine; Wilner, David J.; Zhang, Ke
We report the discovery of a circumplanetary disk (CPD) candidate embedded in the circumstellar disk of the T Tauri star AS 209 at a radial distance of about 200 au (on-sky separation of 1.'' 4 from the star at a position angle of 161 degrees), isolated via (CO)-C-13 J = 2-1 emission. This is the first instance of CPD detection via gaseous emission capable of tracing the overall CPD mass. The CPD is spatially unresolved with a 117 x 82 mas beam and manifests as a point source in (CO)-C-13, indicating that its diameter is less than or similar to 14 au. The CPD is embedded within an annular gap in the circumstellar disk previously identified using (CO)-C-12 and near-infrared scattered-light observations and is associated with localized velocity perturbations in (CO)-C-12. The coincidence of these features suggests that they have a common origin: an embedded giant planet. We use the (CO)-C-13 intensity to constrain the CPD gas temperature and mass. We find that the CPD temperature is greater than or similar to 35 K, higher than the circumstellar disk temperature at the radial location of the CPD, 22 K, suggesting that heating sources localized to the CPD must be present. The CPD gas mass is greater than or similar to 0.095 M (Jup) similar or equal to 30 M (circle plus) adopting a standard (CO)-C-13 abundance. From the nondetection of millimeter continuum emission at the location of the CPD (3 sigma flux density less than or similar to 26.4 mu Jy), we infer that the CPD dust mass is less than or similar to 0.027 M (circle plus) similar or equal to 2.2 lunar masses, indicating a low dust-to-gas mass ratio of less than or similar to 9 x 10(-4). We discuss the formation mechanism of the CPD-hosting giant planet on a wide orbit in the framework of gravitational instability and pebble accretion.

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