Observational constraints on disc sizes in protoplanetary discs in multiple systems in the Taurus region. II. Gas disc sizes
A. A. Rota, C. F. Manara, A. Miotello, G. Lodato, S. Facchini, M. Koutoulaki, G. Herczeg, F. Long, M. Tazzari, S. Cabrit, D. Harsono, F. Menard, P. Pinilla, G. … 展开作者
A. A. Rota, C. F. Manara, A. Miotello, G. Lodato, S. Facchini, M. Koutoulaki, G. Herczeg, F. Long, M. Tazzari, S. Cabrit, D. Harsono, F. Menard, P. Pinilla, G. van der Plas, E. Ragusa, H. -W. Yen
备注：
25 pages, 29 figures, 9 tables. Accepted for publication in A&A
The formation of multiple stellar systems is a natural by-product of the star-formation process, and its impact on the properties of protoplanetary discs and on the formation of planets is still to be fully understood. To date, no detailed uniform study of the gas emission from a sample of protoplanetary discs around multiple stellar systems has been performed. Here we analyse new ALMA observations at a $\sim$21 au resolution of the molecular CO gas emission targeting discs in eight multiple stellar systems in the Taurus star-forming regions. $^{12}$CO gas emission is detected around all primaries and in seven companions. With these data, we estimate the inclination and the position angle for all primary discs and for five secondary or tertiary discs, and measure the gas disc radii of these objects with a cumulative flux technique on the spatially resolved zeroth moment images. When considering the radius including 95\% of the flux as a metric, the estimated gas disc size in multiple stellar systems is found to be on average $\sim 4.2$ times larger than the dust disc size. This ratio is higher than what was recently found in a population of more isolated and single systems. On the contrary, when considering the radius including 68\% of the flux, no difference between multiple and single discs is found in the distribution of ratios. This discrepancy is due to the sharp truncation of the outer dusty disc observed in multiple stellar systems. The measured gas disc sizes are consistent with tidal truncation models in multiple stellar systems assuming eccentricities of $\sim0.15$-$0.5$, as expected in typical binary systems.
Far-infrared and (sub)millimeter fluxes can be used to study dust in protoplanetary disks, the building blocks of planets. Here, we combine observations from the Herschel Space Observatory with ancillary data of 284 protoplanetary disks in the Taurus, Chamaeleon I, and Ophiuchus star-forming regions, covering from the optical to mm/cm wavelengths. We analyze their spectral indices as a function of wavelength and determine their (sub)millimeter slopes when possible. Most disks display observational evidence of grain growth, in agreement with previous studies. No correlation is found between oth…
Measuring the properties of protoplanetary disks around brown dwarfs is central to understanding the formation of brown dwarfs and their planetary companions. We present modeling of CFHT Tau 4 and 2M0444, two brown dwarfs with protoplanetary disks in the Taurus Molecular Cloud. By combining modeling of the spectral energy distributions and ALMA images, we obtain disk radii and masses for these objects; these parameters can be used to constrain brown dwarf formation and planet formation, respectively. We find that the disk around CFHT Tau 4 has a mass of 0.42 M$_{Jup}$ and a radius of 80 au; we…
Context. Studying gas chemistry in protoplanetary disks is key to understanding the process of planet formation. Sulfur chemistry in particular is poorly understood in interstellar environments, and the location of the main reservoirs remains unknown. Protoplanetary disks in Taurus are ideal targets for studying the evolution of the composition of planet forming systems. Aims. We aim to elucidate the chemical origin of sulfur-bearing molecular emission in protoplanetary disks, with a special focus on H$_2$S emission, and to identify candidate species that could become the main molecular sulfur…
Aims: To trace the radial and vertical spatial distribution of H2CS, a key species of the S-bearing chemistry, in protoplanetary disks. To analyse the observed distributions in light of the H2CS binding energy, in order to discuss the role of thermal desorption in enriching the gas disk component. Methods: In the context of the ALMA chemical survey of Disk-Outflow sources in the Taurus star forming region (ALMA-DOT), we observed five Class I or early Class II sources with the o-H2CS(7_1,6-6_1,5) line on a 40 au scale. We estimated the binding energy (BEs) of H2CS using quantum mechanical calcu…
We present the most sensitive 3 mm-survey to date of protoplanetary disks carried in the Taurus-Auriga star forming region (average rms of about 0.3 mJy), using the IRAM PdBI. With our high detection rate of 17/19, we provide the first detections at wavelengths longer than about 1 mm for 12 sources. This enables us to study statistically the mm SED slopes and dust properties of faint disks and compare them to brighter disks using a uniform analysis method. With these new data and literature measurements at sub-millimeter and millimeter wavelengths, we analyze the dust properties of a sample of…
The impact of stellar multiplicity on the evolution of planet-forming disks is still the subject of debate. Here we present and analyze disk structures around ten multiple stellar systems that were included in an unbiased, high spatial resolution survey performed with ALMA of 32 protoplanetary disks in the Taurus star-forming region. At the unprecedented spatial resolution of ~0.12" we detect and spatially resolve the disks around all primary stars, and those around eight secondary and one tertiary star. The dust radii of disks around multiple stellar systems are smaller than those around sing…
Measuring the masses of protoplanetary disks is crucial for understanding their planet-forming potential. Typically, dust masses are derived from (sub-)millimeter flux density measurements plus assumptions for the opacity, temperature, and optical depth of the dust. Here we use radiative transfer models to quantify the validity of these assumptions with the aim of improving the accuracy of disk dust mass measurements. We first carry out a controlled exploration of disk parameter space. We find that the disk temperature is a strong function of disk size, while the optical depth depends on both …
Planets form in protoplanetary disks and inherit their chemical composition. It is therefore crucial to understand the disks molecular content. We aim to characterize the distribution and abundance of molecules in the disk of DG Tau. In the context of the ALMA chemical survey of Disk-Outflow sources in Taurus (ALMA-DOT) we analyse ALMA observations of the disk of DG Tau in H2CO 3(1,2)-2(1,1), CS 5-4, and CN 2-1 at ~0.15", i.e. ~18 au at 121 pc. H2CO and CS originate from a disk ring at the edge of the 1.3mm dust continuum, with CS probing an outer disk region with respect to H2CO (peaking at ~…
The structure of protoplanetary disks is thought to be linked to the temperature and chemistry of their dust and gas. Whether the disk is flat or flaring depends on the amount of radiation that it absorbs at a given radius, and on the efficiency with which this is converted into thermal energy. The understanding of these heating and cooling processes is crucial to provide a reliable disk structure for the interpretation of dust continuum emission and gas line fluxes. Especially in the upper layers of the disk, where gas and dust are thermally decoupled, the infrared line emission is strictly r…
We present the results from a large 850 micron survey of the sigma Orionis cluster using the SCUBA-2 camera on the James Clerk Maxwell Telescope. The 0.5-degree diameter circular region we surveyed contains 297 young stellar objects with an age estimated at about 3Myr. We detect 9 of these objects, 8 of which have infrared excesses from an inner disc. We also serendipitously detect 3 non-stellar sources at > 5sigma that are likely background submillimetre galaxies. The 9 detected stars have inferred disc masses ranging from 5 to about 17MJup, assuming similar dust properties as Taurus discs an…
The chemical composition of planets is inherited from that of the protoplanetary disk at the time of planet formation. Increasing observational evidence suggests that planet formation occurs in less than 1 Myr. This motivates the need for spatially resolved spectral observations of Class I disks, as carried out by the ALMA chemical survey of Disk-Outflow sources in Taurus (ALMA-DOT). In the context of ALMA-DOT, we observe the edge-on disk around the Class I source IRAS 04302+2247 (the butterfly star) in the 1.3mm continuum and five molecular lines. We report the first tentative detection of me…
One of the most well-studied young stellar associations, Taurus-Auriga, will be observed by the extended Kepler mission, K2, in the spring of 2017. K2 Campaign 13 (C13) will be a unique opportunity to study many stars in this young association at high photometric precision and cadence. Using observations from the Kilodegree Extremely Little Telescope (KELT) survey, we identify "dippers", stochastic variables, and periodic variables among K2 C13 target stars. This release of the KELT data (lightcurve data in e-tables) provides the community with long-time baseline observations to assist in the …
We present the largest sample of brown dwarf (BD) protoplanetary disk spectral energy distributions modeled to date. We compile 49 objects with ALMA observations from four star-forming regions: $ρ$ Ophiuchus, Taurus, Lupus, and Upper Scorpius. Studying multiple regions with various ages enables us to probe disk evolution over time. Specifically, from our models we obtain values for dust grain sizes, dust settling, and disk mass; we compare how each of these parameters vary between the regions. We find that disk mass decreases with age. We also find evidence of disk evolution (i.e., grain growt…
Context. Characterizing the evolution of protoplanetary disks is necessary to improve our understanding of planet formation. Constraints on both dust and gas are needed to determine the dominant disk dissipation mechanisms. Aims. We aim to compare the disk dust masses in the Chamaeleon II (Cha II) star-forming region with other regions with ages between 1 and 10Myr. Methods. We use ALMA band 6 observations (1.3 mm) to survey 29 protoplanetary disks in Cha II. Dust mass estimates are derived from the continuum data. Results. Out of our initial sample of 29 disks, we detect 22 sources in the con…
The chemical composition of planets is inherited by the distribution of the various molecular species in the protoplanetary disk at thetime of their formation. As of today, only a handful of disks has been imaged in multiple spectral lines with high spatial resolution. As part of a small campaign devoted to the chemical characterization of disk-outflow sources in Taurus, we report on new ALMA Band 6 observations with 20 au resolution toward the embedded young star DG Tau B. Images of the continuum emission reveals a dust disk with rings and, putatively, a leading spiral arm. The disk, as well …
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 an…
We are conducting a proper-motion survey for young brown dwarfs in the Taurus-Auriga molecular cloud based on the Pan-STARRS1 3$π$ Survey. Our search uses multi-band photometry and astrometry to select candidates, and is wider (370 deg$^{2}$) and deeper (down to $\approx$3 M$_{\rm Jup}$) than previous searches. We present here our search methods and spectroscopic follow-up of our high-priority candidates. Since extinction complicates spectral classification, we have developed a new approach using low-resolution ($R \approx 100$) near-infrared spectra to quantify reddening-free spectral types, …
The 1.33 mm survey of protoplanetary discs in the Taurus molecular cloud found annular gaps and rings to be common in extended sources (>~55 au), when their 1D visibility distributions were fit parametrically. We first demonstrate the advantages and limitations of nonparametric visibility fits for data at the survey's 0.12" resolution. Then we use the nonparametric model in Frankenstein ('frank') to identify new substructure in three compact and seven extended sources. Among the new features we identify three trends: a higher occurrence rate of substructure in the survey's compact discs than p…
Investigating the evolution of protoplanetary disks is crucial for our understanding of star and planet formation. Several theoretical and observational studies have been performed in the last decades to advance this knowledge. FT Tauri is a young star in the Taurus star forming region that was included in a number of spectroscopic and photometric surveys. We investigate the properties of the star, the circumstellar disk, and the accretion and ejection processes and propose a consistent gas and dust model also as a reference for future observational studies. We performed a multi-wavelength dat…
We present new ATCA observations at 3.3 mm of 27 young stellar objects in the rho-Oph young cluster. 25 of these sources have been detected. We analyze the sub-millimeter and millimeter SED for a subsample of 17 isolated class II protoplanetary disks and derive constraints on the grain growth and total dust mass in the disk outer regions. All the disks in our sample show a mm slope of the SED which is significantly shallower than the one observed for the ISM at these long wavelengths. This indicates that 1) class II disks in Ophiuchus host grains grown to mm/cm-sizes in their outer regions, 2)…
The formation of planets strongly depends on the total amount as well as on the spatial distribution of solids in protoplanetary disks. Thanks to the improvements in resolution and sensitivity provided by ALMA, measurements of the surface density of mm-sized grains are now possible on large samples of disks. Such measurements provide statistical constraints that can be used to inform our understanding of the initial conditions of planet formation. We analyze spatially resolved observations of 36 protoplanetary disks in the Lupus star forming complex from our ALMA survey at 890 micron, aiming t…
Evidence for Systematically Larger Dust Grains in Upper Scorpius Relative to Taurus Disks
Southwest Jiaotong University（西南交通大学）；The University of Arizona（亚利桑那大学）；Peking University（北京大学）；Joint ALMA Observatory（ALMA联合观测站）；California Institute of Technology（加州理工学院）；Texas State University（德克萨斯州立大学）；University of Leeds（利兹大学）；Jet Propulsion Laboratory（喷气推进实验室）；Large Binocular Telescope Observatory（大型双筒望远镜天文台）
We present an open access grid of 3930 calculations of externally evaporating protoplanetary discs. This spans a range of disc sizes (1-400AU), disc masses, UV field strengths (10-10$^4$G$_0$) and stellar masses (0.05-1.9M$_\odot$). The grid is publicly available for download, and offers a means of cheaply including external photoevaporation in disc evolutionary calculations. It can also be queried using an online tool for quick estimates of instantaneous mass loss rates (e.g for convenient evaluation of real observed systems). The `FRIED' grid itself illustrates that for discs around stars $\…
Since Protostars and Planets VI (PPVI), our knowledge of the global properties of protoplanetary and debris disks, as well as of young stars, has dramatically improved. At the time of PPVI, mm-observations and optical to near-infrared spectroscopic surveys were largely limited to the Taurus star-forming region, especially of its most massive disk and stellar population. Now, near-complete surveys of multiple star-forming regions cover both spectroscopy of young stars and mm interferometry of their protoplanetary disks. This provides an unprecedented statistical sample of stellar masses and mas…
The high rate of planet detection among solar-type stars argues that planet formation is common. It is also generally assumed that planets form in protoplanetary discs like those observed in nearby star forming regions. On what timescale does the transformation from discs to planets occur? Here we show that current inventories of planets and protoplanetary discs are sensitive enough to place basic constraints on the timescale and efficiency of the planet formation process. A comparison of planet detection statistics and the measured solid reservoirs in T Tauri discs suggests that planet format…
AA Tau, a classical T Tauri star in the Taurus cloud, has been the subject of intensive photometric monitoring for more than two decades due to its quasi-cyclic variation in optical brightness. Beginning in 2011, AA Tau showed another peculiar variation -- its median optical though near-IR flux dimmed significantly, a drop consistent with a 4-mag increase in visual extinction. It has stayed in the faint state since.Here we present 4.7um CO rovibrational spectra of AA Tau over eight epochs, covering an eleven-year time span, that reveal enhanced 12CO and 13CO absorption features in the $J_{\rm …
The UV radiation field is a critical regulator of gas-phase chemistry in surface layers of disks around young stars. In an effort to understand the relationship between photocatalyzing UV radiation fields and gas emission observed at infrared and sub-mm wavelengths, we present an analysis of new and archival HST, Spitzer, ALMA, IRAM, and SMA data for five targets in the Lupus cloud complex and 14 systems in Taurus-Auriga. The HST spectra were used to measure LyA and FUV continuum fluxes reaching the disk surface, which are responsible for dissociating relevant molecular species (e.g. HCN, N2).…
The first stages of planet formation usually occur when the host star is still in a (relatively) dense star-forming region, where the effects of the external environment may be important for understanding the outcome of the planet formation process. In particular, star-forming regions that contain massive stars have strong far ultraviolet (FUV) and extreme ultraviolet (EUV) radiation fields, which can induce mass-loss from protoplanetary discs due to photoevaporation. In this paper we present a parameter-space study of the expected FUV and EUV fields in N-body simulations of star-forming regio…
Nascent Embedded-protostar Survey in Taurus (NEST) II: Measuring Dust Mass, Disk Size, and Gas Mass
University of Virginia（弗吉尼亚大学）；National Radio Astronomy Observatory（美国国家射电天文台）；Space Science Institute（空间科学研究所）；University of Wisconsin-Madison（威斯康星大学麦迪逊分校）；SKA Observatory（平方公里阵列射电望远镜观测站）；University of Arizona（亚利桑那大学）；National Sun Yat-Sen University（国立中山大学）；National Taiwan Normal University（台湾师范大学）
We present the first ALMA survey of protoplanetary discs at 3 mm, targeting 36 young stellar objects in the Lupus star-forming region with deep observations (sensitivity 20-50 microJy/beam) at ~0.35" resolution (~50 au). Building on previous ALMA surveys at 0.89 and 1.3 mm that observed the complete sample of Class II discs in Lupus at a comparable resolution, we aim to assess the level of grain growth in the relatively young Lupus region. We measure 3 mm integrated fluxes, from which we derive disc-averaged 1-3 mm spectral indices. We find that the mean spectral index of the observed Lupus di…
Keck Observations in the INfrared of Taurus and $ρ$ Oph Exoplanets And Ultracool dwarfs (KOINTREAU) I: A Planetary-Mass Companion and a Disk-Obscured Stellar Companion Discovered in Taurus
The cyanide radical CN is abundant in protoplanetary disks, with line fluxes often comparable to those of $^{13}$CO. It is known to be sensitive to UV irradiation of the upper disk atmosphere, with models predicting ring-shaped emission. We seek to characterize the CN emission from 94 Class II disks in the Lupus star forming region, compare it to observations in other regions, and interpret our observations with a grid of models. The CN emission morphology is discussed for two primordial disks, Sz 71 and Sz 98, and modeled in more detail. ALMA observed CN N=3-2 in Lupus disks down to sensitivi…
In order to explain grain growth to mm sized particles and their retention in outer regions of protoplanetary disks, as it is observed at sub-mm and mm wavelengths, we investigate if strong inhomogeneities in the gas density profiles can slow down excessive radial drift and can help dust particles to grow. We use coagulation/fragmentation and disk-structure models, to simulate the evolution of dust in a bumpy surface density profile which we mimic with a sinusoidal disturbance. For different values of the amplitude and length scale of the bumps, we investigate the ability of this model to prod…
The recently discovered exoplanets in binary or higher-order multiple stellar systems sparked a new interest in the study of proto-planetary discs in stellar aggregations. Here we focus on disc solids, as they make up the reservoir out of which exoplanets are assembled and dominate (sub-)millimetre disc observations. These observations suggest that discs in binary systems are fainter and smaller than in isolated systems. In addition, disc dust sizes are consistent with tidal truncation only if they orbit very eccentric binaries. In a previous study we showed that the presence of a stellar comp…
Spectral energy distributions are presented for 94 young stars surrounded by disks in the Serpens Molecular Cloud, based on photometry and Spitzer IRS spectra. Taking a distance to the cloud of 415 pc rather than 259 pc, the distribution of ages is shifted to lower values, in the 1-3 Myr range, with a tail up to 10 Myr. The mass distribution spans 0.2-1.2 Msun, with median mass of 0.7 Msun. The distribution of fractional disk luminosities in Serpens resembles that of the young Taurus Molecular Cloud, with most disks consistent with optically thick, passively irradiated disks in a variety of di…
The transient event labeled as TCP J05074264+2447555 recently discovered towards the Taurus region was quickly recognized to be an ongoing microlensing event on a source located at distance of only $700-800$ pc from Earth. Here, we show that observations with high sampling rate close to the time of maximum magnification revealed features that imply the presence of a binary lens system with very low mass ratio components. We present a complete description of the binary lens system which hosts an Earth-like planet with most likely mass of $9.2\pm 6.6$ M$_{\oplus}$. Furthermore, the source estima…
We present the first high-resolution sub-mm survey of both dust and gas for a large population of protoplanetary disks. Characterizing fundamental properties of protoplanetary disks on a statistical level is critical to understanding how disks evolve into the diverse exoplanet population. We use ALMA to survey 89 protoplanetary disks around stars with $M_{\ast}>0.1~M_{\odot}$ in the young (1--3~Myr), nearby (150--200~pc) Lupus complex. Our observations cover the 890~$μ$m continuum and the $^{13}$CO and C$^{18}$O 3--2 lines. We use the sub-mm continuum to constrain $M_{\rm dust}$ to a few Marti…
(Abridged) We present a study of the disk population in L1688, the densest and youngest region in Ophiuchus, and we compare it with other nearby regions of different age, namely Lupus, Chamaeleon I, Corona Australis, Taurus and Upper Scorpius. We select our L1688 sample using a combination of criteria (ALMA data, Gaia, optical/near-IR spectroscopy) and determine stellar and disk properties, specifically stellar mass (Mstar), average population age, mass accretion rate (Macc) and disk dust mass (Mdust). a) In L1688 the relations between Macc and Mstar, Mdust and Mstar, and Macc and Mdust have a…
This paper shows that the eccentric debris rings seen around the stars Fomalhaut and HD 202628 are narrower than expected in the standard eccentric planet perturbation scenario (sometimes referred to as "pericenter glow"). The standard scenario posits an initially circular and narrow belt of planetesimals at semi-major axis $a$, whose eccentricity is increased to $e_f$ after the gas disc has dispersed by secular perturbations from an eccentric planet, resulting in a belt of width $2ae_f$. In a minor modification of this scenario, narrower belts can arise if the planetesimals are initially ecce…
Photoevaporation of protoplanetary discs by high energy radiation from the central young stellar object is currently the favourite model to explain the sudden dispersal of discs from the inside out. While several theoretical works have provided a detailed pictured of this process, the direct observational validation is still lacking. Emission lines produced in these slow moving protoplanetary disc winds may bear the imprint of the wind structure and thus provide a potential diagnostic of the underlying dispersal process. In this paper we primarily focus on the collisionally excited neutral oxy…
Circumstellar discs may become warped or broken into distinct planes if there is a stellar or planetary companion with an orbit that is misaligned with respect to the disc. There is mounting observational evidence for protoplanetary discs with misaligned inner discs and warps that may be caused by such interactions with a previously undetected companion, giving us a tantalising indication of possible planets forming there. Hydrodynamical and radiative transfer models indicate that the temperature varies azimuthally in warped discs due to the variable angle at which the disc surface faces the s…
The Protoplanetary Discussions conference --- held in Edinburgh, UK, from 7th --11th March 2016 --- included several open sessions led by participants. This paper reports on the discussions collectively concerned with the multiphysics modelling of protoplanetary discs, including the self-consistent calculation of gas and dust dynamics, radiative transfer and chemistry. After a short introduction to each of these disciplines in isolation, we identify a series of burning questions and grand challenges associated with their continuing development and integration. We then discuss potential pathway…
Protoplanetary discs should exhibit a weak vertical variation in their rotation profiles. Typically this `vertical shear' issues from a baroclinic effect driven by the central star's radiation field, but it might also arise during the launching of a magnetocentrifugal wind. As a consequence, protoplanetary discs are subject to a hydrodynamical instability, the `vertical shear instability' (VSI), whose breakdown into turbulence could transport a moderate amount of angular momentum and facilitate, or interfere with, the process of planet formation. Magnetic fields may suppress the VSI, however, …
Nearly all young stars are initially surrounded by `protoplanetary' discs of gas and dust, and in the case of single stars at least 30\% of these discs go on to form planets. The process of protoplanetary disc formation can result in initial misalignments, where the disc orbital plane is different to the stellar equator in single star systems, or to the binary orbital plane in systems with two stars. A quirk of the dynamics means that initially misaligned `circumbinary' discs -- those that surround two stars -- are predicted to evolve to one of two possible stable configurations, one where the…
