Abstract
We present high-resolution Karl G. Jansky Very Large Array (VLA) observations of the protostar L1527 IRS at 7 mm, 1.3 cm, and 2 cm wavelengths. We detect the edge-on dust disk at all three ...wavelengths and find that it is asymmetric, with the southern side of the disk brighter than the northern side. We confirm this asymmetry through analytic modeling and also find that the disk is flared at 7 mm. We test the data against models including gap features in the intensity profile, and though we cannot rule such models out, they do not provide a statistically significant improvement in the quality of fit to the data. From these fits, we can, however, place constraints on allowed properties of any gaps that could be present in the true, underlying intensity profile. The physical nature of the asymmetry is difficult to associate with physical features owing to the edge-on nature of the disk, but it could be related to spiral arms or asymmetries seen in other imaging of more face-on disks.
Abstract
We present high-resolution high-sensitivity observations of the Class 0 protostar RCrA IRS5N as part of the Atacama Large Milimeter/submilimeter Array large program Early Planet Formation in ...Embedded Disks. The 1.3 mm continuum emission reveals a flattened continuum structure around IRS5N, consistent with a protostellar disk in the early phases of evolution. The continuum emission appears smooth and shows no substructures. However, a brightness asymmetry is observed along the minor axis of the disk, suggesting that the disk is optically and geometrically thick. We estimate the disk mass to be between 0.007 and 0.02
M
⊙
. Furthermore, molecular emission has been detected from various species, including C
18
O (2–1),
12
CO (2–1),
13
CO (2–1), and H
2
CO (3
0,3
− 2
0,2
, 3
2,1
− 2
2,0
, and 3
2,2
− 2
2,1
). By conducting a position–velocity analysis of the C
18
O (2–1) emission, we find that the disk of IRS5N exhibits characteristics consistent with Keplerian rotation around a central protostar with a mass of approximately 0.3
M
⊙
. Additionally, we observe dust continuum emission from the nearby binary source IRS5a/b. The emission in
12
CO toward IRS5a/b seems to emanate from IRS5b and flow into IRS5a, suggesting material transport between their mutual orbits. The lack of a detected outflow and large-scale negatives in
12
CO observed toward IRS5N suggests that much of the flux from IRS5N is being resolved out. Using a 1D radiative transfer model, we infer the mass of the envelope surrounding IRS5N to be ∼1.2
M
⊙
. Due to this substantial surrounding envelope, the central IRS5N protostar is expected to be significantly more massive in the future.
Abstract We performed radiative transfer calculations and observing simulations to reproduce the 1.3 mm dust-continuum and C 18 O (2–1) images in the Class I protostar R CrA IRS7B-a, observed with ...the ALMA Large Program “Early Planet Formation in Embedded Disks (eDisk).” We found that a dust disk model passively heated by the central protostar cannot reproduce the observed peak brightness temperature of the 1.3 mm continuum emission (∼195 K), regardless of the assumptions about the dust opacity. Our calculation suggests that viscous accretion heating in the disk is required to reproduce the observed high brightness temperature. The observed intensity profile of the 1.3 mm dust-continuum emission along the disk minor axis is skewed toward the far side of the disk. Our modeling reveals that this asymmetric intensity distribution requires flaring of the dust along the disk vertical direction with the scale height following h / r ∼ r 0.3 as a function of radius. These results are in sharp contrast to those of Class II disks, which show geometrically flat dust distributions and lower dust temperatures. From our modeling of the C 18 O (2–1) emission, the outermost radius of the gas disk is estimated to be ∼80 au, which is larger than that of the dust disk (∼62 au), to reproduce the observed distribution of the C 18 O (2–1) emission in IRS 7B-a. Our modeling unveils a hot and thick dust disk plus a larger gas disk around one of the eDisk targets, which could be applicable to other protostellar sources in contrast to more evolved sources.
We explore the orbital dynamics of systems consisting of three planets, each as massive as the Earth, on coplanar, initially circular, orbits about a star of one solar mass. The initial semimajor ...axes of the planets are equally spaced in terms of their mutual Hill radius, which is equivalent to a geometric progression of orbital periods for small planets of equal mass. Our simulations explore a wide range of spacings of the planets, and were integrated for virtual times of up to 10 billion years or until the orbits of any pair of planets crossed. We find the same general trend of system lifetimes increasing exponentially with separation between orbits seen by previous studies of systems of three or more planets. One focus of this paper is to go beyond the rough trends found by previous numerical studies and quantitatively explore the nature of the scatter in lifetimes and the destabilizing effects of mean motion resonances. In contrast to previous results for five-planet systems, a nontrivial fraction of three-planet systems survive at least several orders of magnitude longer than most other systems with similar initial separation between orbits, with some surviving 1010 years at much smaller orbital separations than any found for five-planet systems. Substantial shifts in the initial planetary longitudes cause a scatter of roughly a factor of two in system lifetime, whereas the shift of one planet's initial position by 100 m along its orbit results in smaller changes in the logarithm of the time to orbit crossing, especially for systems with short lifetimes.
•Lifetimes of 3 planet systems depend strongly on initial longitudes.•Phasing of early conjunctions is important to the stability of 3 planet systems.•Some closely-spaced 3 planet systems are very long-lived.
ABSTRACT
Recent observational missions have uncovered a significant number of compact multi-exoplanet systems. The tight orbital spacing of these systems has led to much effort being applied to the ...understanding of their stability; however, a key limitation of the majority of these studies is the termination of simulations as soon as the orbits of two planets cross. In this work we explore the stability of compact, three-planet systems, and continue our simulations all the way to the first collision of planets to yield a better understanding of the lifetime of these systems. We perform over 25 000 integrations of a Sun-like star orbited by three Earth-like secondaries for up to a billion orbits to explore a wide parameter space of initial conditions in both the co-planar and inclined cases, with a focus on the initial orbital spacing. We calculate the probability of collision over time and determine the probability of collision between specific pairs of planets. We find systems that persist for over 108 orbits after an orbital crossing and show how the post-instability survival time of systems depends upon the initial orbital separation, mutual inclination, planetary radius, and the closest encounter experienced. Additionally, we examine the effects of very small changes in the initial positions of the planets upon the time to collision and show the effect that the choice of integrator can have upon simulation results. We generalize our results throughout to show both the behaviour of systems with an inner planet initially located at 1 and 0.25 AU.
Abstract
We present an overview of the Large Program, “Early Planet Formation in Embedded Disks (eDisk),” conducted with the Atacama Large Millimeter/submillimeter Array (ALMA). The ubiquitous ...detections of substructures, particularly rings and gaps, in protoplanetary disks around T Tauri stars raise the possibility that at least some planet formation may have already started during the embedded stages of star formation. In order to address exactly how and when planet formation is initiated, the program focuses on searching for substructures in disks around 12 Class 0 and 7 Class I protostars in nearby (<200 pc) star-forming regions through 1.3 mm continuum observations at a resolution of ∼7 au (0.″04). The initial results show that the continuum emission, mostly arising from dust disks around the sample protostars, has relatively few distinctive substructures, such as rings and spirals, in marked contrast to Class II disks. The dramatic difference may suggest that substructures quickly develop in disks when the systems evolve from protostars to Class II sources, or alternatively that high optical depth of the continuum emission could obscure internal structures. Kinematic information obtained through CO isotopologue lines and other lines reveals the presence of Keplerian disks around protostars, providing us with crucial physical parameters, in particular, the dynamical mass of the central protostars. We describe the background of the eDisk program, the sample selection and their ALMA observations, and the data reduction, and we also highlight representative first-look results.
Abstract
While dust disks around optically visible, Class II protostars are found to be vertically thin, when and how dust settles to the midplane are unclear. As part of the Atacama Large ...Millimeter/submillimeter Array large program, Early Planet Formation in Embedded Disks, we analyze the edge-on, embedded, Class I protostar IRAS 04302+2247, also nicknamed the “Butterfly Star.” With a resolution of 0.″05 (8 au), the 1.3 mm continuum shows an asymmetry along the minor axis that is evidence of an optically thick and geometrically thick disk viewed nearly edge-on. There is no evidence of rings and gaps, which could be due to the lack of radial substructure or the highly inclined and optically thick view. With 0.″1 (16 au) resolution, we resolve the 2D snow surfaces, i.e., the boundary region between freeze-out and sublimation, for
12
CO
J
= 2–1,
13
CO
J
= 2–1, C
18
O
J
= 2–1,
H
2
CO
J
= 3
0,3
–2
0,2
, and SO
J
= 6
5
–5
4
, and constrain the CO midplane snow line to ∼130 au. We find Keplerian rotation around a protostar of 1.6 ± 0.4
M
⊙
using C
18
O. Through forward ray-tracing using RADMC-3D, we find that the dust scale height is ∼6 au at a radius of 100 au from the central star and is comparable to the gas pressure scale height. The results suggest that the dust of this Class I source has yet to vertically settle significantly.
Abstract
We present observations of the Class 0 protostar IRAS 16544–1604 in CB 68 from the “Early Planet Formation in Embedded Disks (eDisk)” ALMA Large program. The ALMA observations target ...continuum and lines at 1.3 mm with an angular resolution of ∼5 au. The continuum image reveals a dusty protostellar disk with a radius of ∼30 au seen close to edge-on and asymmetric structures along both the major and minor axes. While the asymmetry along the minor axis can be interpreted as the effect of the dust flaring, the asymmetry along the major axis comes from a real nonaxisymmetric structure. The C
18
O image cubes clearly show the gas in the disk that follows a Keplerian rotation pattern around a ∼0.14
M
⊙
central protostar. Furthermore, there are ∼1500 au scale streamer-like features of gas connecting from northeast, north–northwest, and northwest to the disk, as well as the bending outflow as seen in the
12
CO (2–1) emission. At the apparent landing point of the NE streamer, there is SO (6
5
–5
4
) and SiO (5–4) emission detected. The spatial and velocity structure of the NE streamer can be interpreted as a free-falling gas with a conserved specific angular momentum, and the detection of the SO and SiO emission at the tip of the streamer implies the presence of accretion shocks. Our eDisk observations have unveiled that the Class 0 protostar in CB 68 has a Keplerian-rotating disk with a flaring and nonaxisymmetric structure associated with accretion streamers and outflows.
Abstract
Studying the physical and chemical conditions of young embedded disks is crucial to constrain the initial conditions for planet formation. Here we present Atacama Large ...Millimeter/submillimeter Array observations of dust continuum at ∼0.″06 (8 au) resolution and molecular line emission at ∼0.″17 (24 au) resolution toward the Class 0 protostar L1527 IRS from the Large Program eDisk (Early Planet Formation in Embedded Disks). The continuum emission is smooth without substructures but asymmetric along both the major and minor axes of the disk as previously observed. The detected lines of
12
CO,
13
CO, C
18
O, H
2
CO, c-C
3
H
2
, SO, SiO, and DCN trace different components of the protostellar system, with a disk wind potentially visible in
12
CO. The
13
CO brightness temperature and the H
2
CO line ratio confirm that the disk is too warm for CO freezeout, with the snowline located at ∼350 au in the envelope. Both molecules show potential evidence of a temperature increase around the disk–envelope interface. SO seems to originate predominantly in UV-irradiated regions such as the disk surface and the outflow cavity walls rather than at the disk–envelope interface as previously suggested. Finally, the continuum asymmetry along the minor axis is consistent with the inclination derived from the large-scale (100″ or 14,000 au) outflow, but opposite to that based on the molecular jet and envelope emission, suggesting a misalignment in the system. Overall, these results highlight the importance of observing multiple molecular species in multiple transitions to characterize the physical and chemical environment of young disks.
We explore the orbital dynamics of systems consisting of three planets, each as massive as the Earth, on coplanar, initially circular, orbits about a star of one solar mass. The initial semimajor ...axes of the planets are equally spaced in terms of their mutual Hill radius, which is equivalent to a geometric progression of orbital periods for small planets of equal mass. Our simulations explore a wide range of spacings of the planets, and were integrated for virtual times of up to 10 billion years or until the orbits of any pair of planets crossed. We find the same general trend of system lifetimes increasing exponentially with separation between orbits seen by previous studies of systems of three or more planets. One focus of this paper is to go beyond the rough trends found by previous numerical studies and quantitatively explore the nature of the scatter in lifetimes and the destabilizing effects of mean motion resonances. In contrast to previous results for five-planet systems, a nontrivial fraction of three-planet systems survive at least several orders of magnitude longer than most other systems with similar initial separation between orbits, with some surviving \(10^{10}\) years at much smaller orbital separations than any found for five-planet systems. Substantial shifts in the initial planetary longitudes cause a scatter of roughly a factor of two in system lifetime, whereas the shift of one planet's initial position by 100 meters along its orbit results in smaller changes in the logarithm of the time to orbit crossing, especially for systems with short lifetimes.
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