Aims. We study the dependence of protoplanetary disk evolution on stellar mass using a large sample of young stellar objects in nearby young star-forming regions. Methods. We update the ...protoplanetary disk fractions presented in our recent work (Paper I of this series) derived for 22 nearby (<500 pc) associations between 1 and 100 Myr. We use a subsample of 1428 spectroscopically confirmed members to study the impact of stellar mass on protoplanetary disk evolution. We divide this sample into two stellar mass bins (2 M⊙ boundary) and two age bins (3 Myr boundary), and use infrared excesses over the photospheric emission to classify objects in three groups: protoplanetary disks, evolved disks, and diskless. The homogeneous analysis and bias corrections allow for a statistically significant inter-comparison of the obtained results. Results. We find robust statistical evidence of disk evolution dependence with stellar mass. Our results, combined with previous studies on disk evolution, confirm that protoplanetary disks evolve faster and/or earlier around high-mass (>2 M⊙) stars. We also find a roughly constant level of evolved disks throughout the whole age and stellar mass spectra. Conclusions. We conclude that protoplanetary disk evolution depends on stellar mass. Such a dependence could have important implications for gas giant planet formation and migration, and could contribute to explaining the apparent paucity of hot Jupiters around high-mass stars.
Our understanding of protoplanetary disks is rapidly departing from the classical view of a smooth, axisymmetric disk. This is in part thanks to the high angular resolution that (sub)millimeter ...observations can provide. Here, we present the combined results of Atacama Large Millimeter/submillimeter Array (ALMA) (0.9 mm) and Very Large Array (VLA) (7 mm) dust continuum observations toward the protoplanetary disk around the solar analog GM Aur. Both images clearly resolve the ∼35 au inner cavity. The ALMA observations also reveal a fainter disk that extends up to ∼250 au. We model our observations using two approaches: an analytical fit to the observed deprojected visibilities, and a physical disk model that fits the spectral energy distribution as well as the VLA and ALMA observations. Despite not being evident in the deconvolved images, the VLA and ALMA visibilities can only be fitted with two bright rings of radii ∼40 and ∼80 au. Our physical model indicates that this morphology is the result of an accumulation or trapping of large dust grains, probably due to the presence of two pressure bumps in the disk. Even though alternative mechanisms cannot be discarded, the multiple rings suggest that forming planets may have cleared at least two gaps in the disk. Finally, our analysis suggests that the inner cavity might display different sizes at 0.9 and 7 mm. This discrepancy could be caused by the presence of free-free emission close to the star at 7 mm, or by a more compact accumulation of the large dust grains at the edge of the cavity.
We study the evolution of circumstellar disks in 22 young nearby associations over the entire mass spectrum using photometry covering from the optical to the mid-infrared. We compiled a catalog of ...2340 spectroscopically-confirmed members of these nearby associations. We analyzed their spectral energy distributions and searched for excess related to the presence of protoplanetary disks. The dataset has been analyzed in a homogeneous and consistent way, allowing for meaningful inter-comparison of results obtained for individual regions. The increase in timescale of excess decay at longer wavelength is compatible with inside-out disk clearing scenarios. The increased timescale of decay and larger dispersion in the distribution of disk fractions at 22-24 mu m suggest that the inner and outer zones evolve differently, the latter potentially following a variety of evolutionary paths. The drop of primordial disks and the coincident rise of evolved disks at 10 Myr are compatible with planet formation theories suggesting that the disappearance of the gas is immediately followed by the dynamical stirring of the disk.
Abstract
We present spectral energy distribution (SED) modeling of 338 disks around T Tauri stars from 11 star-forming regions, ranging from ∼0.5 to 10 Myr old. The disk masses we infer from our SED ...models are typically greater than those reported from (sub)millimeter surveys by a factor of 1.5–5, with the discrepancy being generally higher for the more massive disks. Masses derived from (sub)millimeter fluxes rely on the assumption that the disks are optically thin at all millimeter wavelengths, which may cause the disk masses to be underestimated since the observed flux is not sensitive to the whole mass in the disk; SED models do not make this assumption and thus yield higher masses. Disks with more absorbing material should be optically thicker at a given wavelength, which could lead to a larger discrepancy for disks around massive stars when the disk temperature is scaled by the stellar luminosity. We also compare the disk masses and degree of dust settling across the different star-forming regions and find that disks in younger regions are more massive than disks in older regions, but with a similar degree of dust settling. Together, these results offer potential partial solutions to the “missing” mass problem: disks around T Tauri stars may indeed have enough material to form planetary systems, though previous studies have underestimated the mass by assuming the disks to be optically thin; these planetary systems may also form earlier than previously theorized since significant dust evolution (i.e., settling) is already apparent in young disks.
Abstract
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 other tracers of disk evolution and the millimeter spectral indices. A simple disk model is used to fit these sources, and we derive posterior distributions for the optical depth at 1.3 mm and 10 au, the disk temperature at this same radius, and the dust opacity spectral index
β
. We find the fluxes at 70
μ
m to correlate strongly with disk temperatures at 10 au, as derived from these simple models. We find tentative evidence for spectral indices in Chamaeleon I being steeper than those of disks in Taurus/Ophiuchus, although more millimeter observations are needed to confirm this trend and identify its possible origin. Additionally, we determine the median spectral energy distribution of each region and find them to be similar across the entire wavelength range studied, possibly due to the large scatter in disk properties and morphologies.
Abstract While high-resolution Atacama Large Millimeter/submillimeter Array (ALMA) observations reveal a wealth of substructure in protoplanetary disks, they remain incapable of resolving the types ...of small-scale dust structures predicted, for example, by numerical simulations of the streaming instability. In this article, we propose a method to find evidence for unresolved, optically thick dusty rings in protoplanetary disks. We demonstrate that, in presence of unresolved rings, the brightness of an inclined disk exhibits a distinctive emission peak at the minor axis. Furthermore, the azimuthal brightness depends on both the geometry of the rings and the dust optical properties; we can therefore use the azimuthal brightness variations to both detect unresolved rings and probe their properties. By analyzing the azimuthal brightness in the test case of ringlike substructures formed by streaming instability, we show that the resulting peak is likely detectable by ALMA for typical disk parameters. Moreover, we present an analytic model that not only qualitatively but also quantitatively reproduces the peak found in the simulations, validating its applicability to infer the presence of unresolved rings in observations and characterize their optical properties and shape. This will contribute to the identification of disk regions where streaming instability (and thus planet formation) is occurring.
Abstract
Gas-rich circumstellar disks are the cradles of planet formation. As such, their evolution will strongly influence the resulting planet population. In the ESO DESTINYS large program, we ...study these disks within the first 10 Myr of their development with near-infrared scattered-light imaging. Here we present VLT/SPHERE polarimetric observations of the nearby class II system SU Aur in which we resolve the disk down to scales of ∼7 au. In addition to the new SPHERE observations, we utilize VLT/NACO, HST/STIS, and ALMA archival data. The new SPHERE data show the disk around SU Aur and extended dust structures in unprecedented detail. We resolve several dust tails connected to the Keplerian disk. By comparison with ALMA data, we show that these dust tails represent material falling onto the disk. The disk itself shows an intricate spiral structure and a shadow lane, cast by an inner, misaligned disk component. Our observations suggest that SU Aur is undergoing late infall of material, which can explain the observed disk structures. SU Aur is the clearest observational example of this mechanism at work and demonstrates that late accretion events can still occur in the class II phase, thereby significantly affecting the evolution of circumstellar disks. Constraining the frequency of such events with additional observations will help determine whether this process is responsible for the spin–orbit misalignment in evolved exoplanet systems.
Abstract
We have selected 337 intermediate- and high-mass young stellar objects (YSOs; 1.5–20
M
⊙
) well-characterized with spectroscopy. By means of the clustering algorithm HDBSCAN, we study their ...clustering and association properties in the Gaia DR3 catalog as a function of stellar mass. We find that the lower-mass YSOs (1.5–4
M
⊙
) have clustering rates of 55%–60% in Gaia astrometric space, a percentage similar to that found in the T Tauri regime. However, intermediate-mass YSOs in the range 4–10
M
⊙
show a decreasing clustering rate with stellar mass, down to 27%. We find tentative evidence suggesting that massive YSOs (>10
M
⊙
) often (yet not always) appear clustered. We put forward the idea that most massive YSOs form via a mechanism that demands many low-mass stars around them. However, intermediate-mass YSOs form in a classical core-collapse T Tauri way, yet they do not appear often in the clusters around massive YSOs. We also find that intermediate- and high-mass YSOs become less clustered with decreasing disk emission and accretion rate. This points toward an evolution with time. For those sources that appear clustered, no major correlation is found between their stellar properties and the cluster sizes, number of cluster members, cluster densities, or distance to cluster centers. In doing this analysis, we report the identification of 55 new clusters. We tabulated all of the derived cluster parameters for the considered intermediate- and high-mass YSOs.
Abstract
ASASSN-21qj is a distant Sun-like star that recently began an episode of deep dimming events after no prior recorded variability. Here we examine archival and newly obtained optical and ...near-infrared data of this star. The deep aperiodic dimming and absence of previous infrared excess are reminiscent of KIC 8462852 (“Boyajian’s Star”). The observed occultations are consistent with a circumstellar cloud of submicron-sized dust grains composed of amorphous pyroxene, with a minimum mass of 1.50 ± 0.04 × 10
−9
M
⊕
derived from the deepest occultations, and a minimum grain size of
0.29
−
0.18
+
0.01
μ
m
assuming a power-law size distribution. We further identify the first evidence of near-infrared excess in this system from NEOWISE 3.4 and 4.6
μ
m observations. The excess emission implies a total circumstellar dust mass of around 10
−6
M
⊕
, comparable to the extreme, variable disks associated with terrestrial planet formation around young stars. The quasiperiodic recurrence of deep dips and the inferred dust temperature (ranging from 1800 to 700 K across the span of observations) independently point to an orbital distance of ≃0.2 au for the dust, supporting the occulting material and excess emission being causally linked. The origin of this extended, opaque cloud is surmised to be the breakup of one or more exocometary bodies.
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