Protoplanetary disk lifetimes vs stellar mass and possible implications for giant planet populations

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. 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 1 428 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$_{\odot}$ 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. 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$_{\odot}$) stars. We also find a roughly constant level of evolved disks throughout the whole age and stellar mass spectra. 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.Comment: Accepted for publication in A&A. 13 pages, 8 figures, 5 table

Long-lived protoplanetary disks in multiple systems: the VLA view of HD 98800

The conditions and evolution of protoplanetary disks in multiple systems can be considerably different from those around single stars, which may have important consequences for planet formation. We present Very Large Array (VLA) 8.8 mm (34 GHz) and 5 cm (6 GHz) observations of the quadruple system HD 98800, which consists of two spectroscopic binary systems (Aa-Ab, Ba-Bb). The Ba-Bb pair is surrounded by a circumbinary disk, usually assumed to be a debris disk given its $\sim$10 Myr age and lack of near infrared excess. The VLA 8.8 mm observations resolve the disk size (5-5.5 au) and its inner cavity ($\approx$3 au) for the first time, making it one of the smallest disks known. Its small size, large fractional luminosity, and millimeter spectral index consistent with blackbody emission support the idea that HD 98800 B is a massive, optically thick ring which may still retain significant amounts of gas. The disk detection at 5 cm is compatible with free-free emission from photoionized material. The diskless HD 98800 A component is also detected, showing partial polarization at 5 cm compatible with non-thermal chromospheric activity. We propose that tidal torques from Ba-Bb and A-B have stopped the viscous evolution of the inner and outer disk radii, and the disk is evolving via mass loss through photoevaporative winds. This scenario can explain the properties and longevity of HD 98800 B as well as the lack of a disk around HD 98800 A, suggesting that planet formation could have more time to proceed in multiple systems than around single stars in certain system configurations.Comment: 14 pages, 4 figures, 3 tables; Submitted to ApJ May 14 2018; Accepted to ApJ August 3 2018. This version fixes a mistake in the reported position angle. The order of the figures has been changed to match that of the references in the tex

Herschel/PACS photometry of transiting-planet host stars with candidate warm debris disks

Dust in debris disks is produced by colliding or evaporating planetesimals, remnants of the planet formation process. Warm dust disks, known by their emission at < 24 micron, are rare (4% of FGK main sequence stars) and especially interesting because they trace material in the region likely to host terrestrial planets, where the dust has a very short dynamical lifetime. Statistical analyses of the source counts of excesses as found with the mid-IR Wide Field Infrared Survey Explorer (WISE) suggest that warm-dust candidates found for the Kepler transiting-planet host-star candidates can be explained by extragalactic or galactic background emission aligned by chance with the target stars. These statistical analyses do not exclude the possibility that a given WISE excess could be due to a transient dust population associated with the target. Here we report Herschel/PACS 100 and 160 micron follow-up observations of a sample of Kepler and non-Kepler transiting-planet candidates' host stars, with candidate WISE warm debris disks, aimed at detecting a possible cold debris disk in any of them. No clear detections were found in any one of the objects at either wavelength. Our upper limits confirm that most objects in the sample do not have a massive debris disk like that in beta Pic. We also show that the planet-hosting star WASP-33 does not have a debris disk comparable to the one around eta Crv. Although the data cannot be used to rule out rare warm disks around the Kepler planet-hosting candidates, the lack of detections and the characteristics of neighboring emission found at far-IR wavelengths support an earlier result suggesting that most of the WISE-selected IR excesses around Kepler candidate host stars are likely due to either chance alignment with background IR-bright galaxies and/or to interstellar emission.Comment: 8 pages, 3 figures, accepted for publication at Astronomy & Astrophysics on 4 August 201

Evolución de discos protoplanetarios en regiones de formaci ón estelar cercanas

Tesis doctoral inédita leída en la Universidad Autónoma de Madrid, Facultad de Ciencias, Departamento de Física Teórica. Fecha de lectura: 24-07-2015The main aim of this work is to better understand the evolution of protoplanetary disks around young stars in the solar neighborhood. It comprises three rst authored published papers, a fourth paper about to be submitted, and additional research as participation in six other refereed papers, which I coauthored during the period of this thesis. To asses disk evolution homogeneously, we compile a large sample of more than 2 300 members of 22 young (<100 Myr) nearby (<500 pc) star-forming regions and associations. All these objects have spectroscopic con rmation of membership to their host young association and measurements of their spectral types, which is complemented with photometry from up to 35 di erent lters covering from near ultraviolet to mid-infrared wavelengths. After considering possible biases, we consistently estimate the fraction of disks as a function of age. We obtain a characteristic disk lifetime of 3 Myr, in agreement with previous studies. We also nd that disk dispersal occurs in 1 Myr and tentative evidence of this process acting from inside out, suggesting that photoevaporation plays an important role in disk evolution. The unprecedented size of this sample provides the most robust con rmation up to date of a dependence of disk evolution with stellar mass, with T Tauri stars maintaining their disks for longer periods than Herbig Ae/Be stars. This result may have an important in uence on planet formation and exoplanetary populations. It may also represent the rst direct link achieved between a statistical property of protoplanetary disks and a statistical property of the exoplanetary systems at later phases, and constitutes one of the big new results from this thesis. We also explore the population of young disks in the Chamaeleon star-forming complex with Herschel data, in particular focusing on transitional disks in Chamaeleon I. We nd that the six transitional targets in the sample detected with Herschel have 70 m excesses higher than 75% of the Class II objects in the region. Further modeling of these disks reveals that Herschel SPIRE photometry can be used to e ciently constrain the mass of dust in these sources, one of the most relevant parameters for planet formation. The modeling also shows evidence for anomalous outer regions of transitional objects when compared to full protoplanetary disks

Infrared study of transitional disks in Ophiuchus with Herschel

Context. Observations of nearby star-forming regions with the Herschel Space Observatory complement our view of the protoplanetary disks in Ophiuchus with information about the outer disks. Aims. The main goal of this project is to provide new far-infrared fluxes for the known disks in the core region of Ophiuchus and to identify potential transitional disks using data from Herschel. Methods. We obtained PACS and SPIRE photometry of previously spectroscopically confirmed young stellar objects (YSO) in the region and analysed their spectral energy distributions. Results. From an initial sample of 261 objects with spectral types in Ophiuchus, we detect 49 disks in at least one Herschel band. We provide new far-infrared fluxes for these objects. One of them is clearly a new transitional disk candidate. Conclusions. The data from Herschel Space Observatory provides fluxes that complement previous infrared data and that we use to identify a new transitional disk candidate.Comment: 21 pages, with 5 figures. Accepted in Astronomy & Astrophysic

A coplanar circumbinary protoplanetary disk in the TWA 3 triple M dwarf system

Funding: This project has received funding from the European Union’s Horizon 2020 research and innovation program under the Marie Skłodowska-Curie grant agreement No 210021. E.C. acknowledges NASA grants 80NSSC19K0506 and NNX15AD95G/NEXSS.We present sensitive ALMA observations of TWA 3, a nearby, young (∼10 Myr) hierarchical system composed of three pre-main-sequence M3–M4.5 stars. For the first time, we detected 12CO and 13CO J = 2–1 emissions from the circumbinary protoplanetary disk around TWA 3A. We jointly fit the protoplanetary disk velocity field, stellar astrometric positions, and stellar radial velocities to infer the architecture of the system. The Aa and Ab stars (0.29 ± 0.01 M⊙ and 0.24 ± 0.01 M⊙, respectively) comprising the tight (P = 35 days) eccentric (e = 0.63 ± 0.01) spectroscopic binary are coplanar with their circumbinary disk (misalignment <6° with 68% confidence), similar to other short-period binary systems. From models of the spectral energy distribution, we found the inner radius of the circumbinary disk (rinner = 0.50–0.75 au) to be consistent with theoretical predictions of dynamical truncation rcav/ainner ≈ 3. The outer orbit of the tertiary star B (0.40 ± 0.28 M⊙, a ∼ 65 ± 18 au, e = 0.3 ± 0.2) is not as well constrained as the inner orbit; however, orbits coplanar with the A system are still preferred (misalignment < 20°). To better understand the influence of the B orbit on the TWA 3A circumbinary disk, we performed SPH simulations of the system and found that the outer edge of the gas disk (router = 8.5 ± 0.2 au) is most consistent with truncation from a coplanar, circular, or moderately eccentric orbit, supporting the preference from the joint orbital fit.Publisher PDFPeer reviewe

A coplanar circumbinary protoplanetary disk in the TWA 3 triple M dwarf system

We present sensitive ALMA observations of TWA 3, a nearby, young ($\sim$10 Myr) hierarchical system composed of three pre-main sequence M3--M4.5 stars. For the first time, we detected ${}^{12}$CO and ${}^{13}$CO $J$=2-1 emission from the circumbinary protoplanetary disk around TWA 3A. We jointly fit the protoplanetary disk velocity field, stellar astrometric positions, and stellar radial velocities to infer the architecture of the system. The Aa and Ab stars ($0.29\pm0.01\,M_\odot$ and $0.24\pm0.01\,M_\odot$, respectively) comprising the tight ($P=35$ days) eccentric ($e=0.63\pm0.01$) spectroscopic binary are coplanar with their circumbinary disk (misalignment $< 6^{\circ}$ with 68% confidence), similar to other short-period binary systems. From models of the spectral energy distribution, we found the inner radius of the circumbinary disk ($r_\mathrm{inner} = 0.50 - 0.75$ au) to be consistent with theoretical predictions of dynamical truncation $r_\mathrm{cav}/a_\mathrm{inner} \approx 3$. The outer orbit of the tertiary star B ($0.40\pm0.28\,M_\odot$, $a\sim65 \pm 18$ au, $e=0.3\pm0.2$) is not as well constrained as the inner orbit, however, orbits coplanar with the A system are still preferred (misalignment $< 20^{\circ}$). To better understand the influence of the B orbit on the TWA 3A circumbinary disk, we performed SPH simulations of the system and found that the outer edge of the gas disk ($r_\mathrm{outer}=8.5\pm0.2$ au) is most consistent with truncation from a coplanar, circular or moderately eccentric orbit, supporting the preference from the joint orbital fit.Comment: 19 pages, 9 figures, accepted to Ap

Clustering properties of intermediate and high-mass Young Stellar Objects

We have selected 337 intermediate and high-mass YSOs ($1.5$ to $20$ M$_{\odot}$) well-characterised with spectroscopy. By means of the clustering algorithm HDBSCAN, we study their clustering and association properties in the Gaia DR3 catalogue as a function of stellar mass. We find that the lower mass YSOs ($1.5-4$ M$_{\odot}$) have clustering rates of $55-60\%$ in Gaia astrometric space, a percentage similar to the one found in the T Tauri regime. However, intermediate-mass YSOs in the range $4-10$ M$_{\odot}$ show a decreasing clustering rate with stellar mass, down to $27\%$. We find tentative evidence suggesting that massive YSOs ($>10$ M$_{\odot}$) often appear $-$yet not always$-$ 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 towards 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 centres. In doing this analysis, we report the identification of 55 new clusters. We present tabulated all the derived cluster parameters for the considered intermediate and high-mass YSOs.Comment: Accepted for publication in The Astronomical Journal on August 18th, 2023. Table 1 and the new clusters can be provided upon reques