The Anatomy of an Unusual Edge-on Protoplanetary Disk. II. Gas temperature and a warm outer region

We present high-resolution $^{12}$CO and $^{13}$CO 2-1 ALMA observations, as well as optical and near-infrared spectroscopy, of the highly-inclined protoplanetary disk around SSTC2D J163131.2-242627. The spectral type we derive for the source is consistent with a $\rm 1.2 \, M_{\odot}$ star inferred from the ALMA observations. Despite its massive circumstellar disk, we find little to no evidence for ongoing accretion on the star. The CO maps reveal a disk that is unusually compact along the vertical direction, consistent with its appearance in scattered light images. The gas disk extends about twice as far away as both the submillimeter continuum and the optical scattered light. CO is detected from two surface layers separated by a midplane region in which CO emission is suppressed, as expected from freeze-out in the cold midplane. We apply a modified version of the Topographically Reconstructed Distribution method presented by Dutrey et al. 2017 to derive the temperature structure of the disk. We find a temperature in the CO-emitting layers and the midplane of $\sim$33 K and $\sim$20 K at $\rm R<200$ au, respectively. Outside of $\rm R>200$ au, the disk's midplane temperature increases to $\sim$30 K, with a nearly vertically isothermal profile. The transition in CO temperature coincides with a dramatic reduction in the sub-micron and sub-millimeter emission from the disk. We interpret this as interstellar UV radiation providing an additional source of heating to the outer part of the disk.Comment: 27 pages, 18 figures, 1 tabl

Evolution of protoplanetary disks from their taxonomy in scattered light: spirals, rings, cavities, and shadows

The variety of observed protoplanetary disks in polarimetric light motivates a taxonomical study to constrain their evolution and establish the current framework of this type of observations. We classified 58 disks with available polarimetric observations into six major categories (Ring, Spiral, Giant, Rim, Faint, and Small disks) based on their appearance in scattered light. We re-calculated the stellar and disk properties from the newly available GAIA DR2 and related these properties with the disk categories. More than a half of our sample shows disk sub-structures. For the remaining sources, the absence of detected features is due to their faintness, to their small size, or to the disk geometry. Faint disks are typically found around young stars and typically host no cavity. There is a possible dichotomy in the near-IR excess of sources with spiral-disks (high) and ring-disks (low). Like spirals, shadows are associated with a high near-IR excess. If we account for the pre-main sequence evolutionary timescale of stars with different mass, spiral arms are likely associated to old disks. We also found a loose, shallow declining trend for the disk dust mass with time. Protoplanetary disks may form sub-structures like rings very early in their evolution but their detectability in scattered light is limited to relatively old sources (more than 5 Myr) where the recurrently detected disk cavities allow to illuminate the outer disk. The shallow decrease of disk mass with time might be due to a selection effect, where disks observed thus far in scattered light are typically massive, bright transition disks with longer lifetime than most disks. Our study points toward spirals and shadows being generated by planets of fraction-to-few Jupiter masses that leave their (observed) imprint on both the inner disk near the star and the outer disk cavity.This work has been supported by the project PRININAF 2016 The Cradle of Life - GENESIS-SKA (General Conditions in Early Planetary Systems for the rise of life with SKA). A.G. acknowledges the support by INAF/Frontiera through the "Progetti Premiali" funding scheme of the Italian Ministry of Education, University, and Research. We acknowledge funding from ANR of France under contract number ANR-16-CE31-0013 (Planet Forming disks). P.P. acknowledges support by NASA through Hubble Fellowship grant HST-HF2-51380.001-A awarded by the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., for NASA, under contract NAS 5-26555

Demographics of Protoplanetary Disks: A Simulated Population of Edge-on Systems

The structure of protoplanetary disks plays an essential role in planet formation. Disks that are highly inclined, or ''edge-on'', are of particular interest since their geometry provides a unique opportunity to study the disk's vertical structure and radial extent. Candidate edge-on protoplanetary disks are typically identified via their unique spectral energy distribution and subsequently confirmed through high-resolution imaging. However, this selection process is likely biased toward the largest, most massive disks, and the resulting sample may not accurately represent the underlying disk population. To investigate this, we generated a grid of protoplanetary disk models using radiative transfer simulations and determined which sets of disk parameters produce edge-on systems that could be recovered by aforementioned detection techniques--i.e., identified by their spectral energy distribution and confirmed through follow-up imaging with HST. In doing so, we adopt a quantitative working definition of "edge-on disks" that is observation-driven and agnostic about the disk inclination or other properties. Folding in empirical disk demographics, we predict an occurrence rate of 6.2% for edge-on disks and quantify biases towards highly inclined, massive disks. We also find that edge-on disks are under-represented in samples of Spitzer-studied young stellar objects, particularly for disks with M $\lesssim$ 0.5 $M_\odot$. Overall, our analysis suggests that several dozen edge-on disks remain undiscovered in nearby star-forming regions, and provides a universal selection process to identify edge-on disks for consistent, population-level demographic studies.Comment: 20 pages, 6 figure

Constraining the physical processes of protoplanetary disk evolution

Une grande diversité est actuellement observée au sein des exoplanètes découvertes. L'étude des disques protoplanétaires permet d'en apprendre plus sur la formation des planètes. En particulier, les disques se dissipent en quelques millions d'années, ce qui implique que les planètes géantes doivent se former très rapidement à partir des petits grains de taille micrométrique présents initialement. Cette thèse vise à ajouter des contraintes observationnelles à plusieurs mécanismes qui contrôlent l'évolution des disques protoplanétaires, et donc la formation des planètes. En particulier, j'ai travaillé sur une étude statistique de la distribution de la masse de poussière dans des disques situés dans la région de formation stellaire Chamaeleon II, sur la présence de cavités dans les disques de transition et sur des contraintes observationnelles de quelques mécanismes d'évolution des poussières tels que la dérive radiale et la sédimentation verticale des grains. J'ai utilisé principalement des observations millimétriques ALMA que j'ai comparées avec d'autres traceurs comme par exemple des images aux longueurs d'onde du visible ou de l'infrarouge. À plusieurs reprises, j'ai modélisé ces observations par transfert radiatif pour contraindre la structure de ces disques protoplanétaires.Au cours de cette thèse, j'ai obtenu d'importantes contraintes observationnelles sur la structure verticale des disques protoplanétaires, notamment en étudiant un échantillon de 12 disques très inclinés. Aux longueurs d'onde du millimètre, les disques les plus inclinés de cette étude, où l'étendue verticale est directement visible, apparaissent extrêmement mince dans la direction verticale, significativement plus mince que les observations en lumière diffusée (grains plus petits). Ceci indique que la sédimentation verticale des poussières est extrêmement efficace dans ces disques, ce qui est favorable à la croissance rapide des grains dans le plan médian du disque. Par ailleurs, en étudiant la région Chamaeleon II, j'ai montré que la distribution de masse des disques diminue statistiquement avec le temps. Ce résultat est en accord avec les prédictions de l'évolution visqueuse des disques. Enfin, l'étude d'un échantillon de 22 disques de transition a permis de montrer que la plupart des cavités de ces disques pourraient être causées par des planètes interagissant avec le disque. Ces résultats suggèrent donc que des planètes se sont peut-être déjà formées dans ces disques, ce qui implique que leur temps de formation est extrêmement court. Le mécanisme de sédimentation verticale des grains est un bon candidat permettant d'accélérer la formation des planètes. En effet, comme décrit précédemment, j'ai montré que l'étendue verticale des grains millimétrique est très faible, ce qui implique que ces grains sont très concentrés dans le plan médian. Une forte densité de poussière étant favorable à une croissance accélérée des grains de poussière, ce mécanisme pourrait être favorable à la formation de planètes très tôt dans l'évolution des disques.The diversity observed in the exoplanet population likely originates in the variety of physical structures of protoplanetary disks, their progenitors. Considering the timescales for disk dissipation, it is clear that giant planets must form fast, within a few million years. In the standard core accretion model, this implies that micron sized particles have to grow within this short timescale to larger sizes. This PhD thesis is dedicated to adding observational constraints on several aspects of protoplanetary disk evolution in order to understand better the processes of planet formation. In particular, I worked on a statistical study of the dust mass distribution in protoplanetary disks located in the Chamaeleon II star-forming region, on the presence of dust depleted cavities in transition disks and on observational constraints on dust evolution mechanisms such as radial drift and vertical settling. I used mostly ALMA millimeter observations, which I combined with complementary disk tracers such as optical/infrared scattered light images. On several occasions, I modeled these observations with radiative transfer to constrain the structure of these protoplanetary disks.During this thesis, I have obtained important constraints on the vertical structure of protoplanetary disks, notably by studying a sample of 12 highly inclined disks. I find that the most inclined systems of this survey, where the vertical extent is best seen, are extremely thin at millimeter wavelengths, all the more when compared to their vertical extent seen with scattered light observations (probing smaller grains). This indicates that vertical settling is extremely efficient in these disks, which is favorable for fast grain growth in the disk midplane. Additionally, my study of the Chamaeleon~II star-forming region showed that the distribution of the disk dust mass statistically decreases with time. This is consistent with predictions from viscous evolution. Finally, with the study of a sample of 22 transition disks, I showed that their cavities can mostly be explained by the presence of planets. These results suggest that planets might already have formed in these disks, implying that the timescale available for planet formation is short. A possible mechanism allowing to boost planet formation is vertical settling. Indeed, as detailed previously, my studies showed that the vertical extent of protoplanetary disks is small at millimeter wavelengths, which implies that millimeter sized grains (and larger) are concentrated in a vertically thin midplane where the dust density is increased. Depending on when this vertical settling takes place, this mechanism is a good candidate for enhancing grain growth efficiency. Combined to other processes, vertical settling might allow to form planets in the earliest stages of disk evolution

Caractérisation des processus d'évolution des disques protoplanétaires

The diversity observed in the exoplanet population likely originates in the variety of physical structures of protoplanetary disks, their progenitors. Considering the timescales for disk dissipation, it is clear that giant planets must form fast, within a few million years. In the standard core accretion model, this implies that micron sized particles have to grow within this short timescale to larger sizes. This PhD thesis is dedicated to adding observational constraints on several aspects of protoplanetary disk evolution in order to understand better the processes of planet formation. In particular, I worked on a statistical study of the dust mass distribution in protoplanetary disks located in the Chamaeleon II star-forming region, on the presence of dust depleted cavities in transition disks and on observational constraints on dust evolution mechanisms such as radial drift and vertical settling. I used mostly ALMA millimeter observations, which I combined with complementary disk tracers such as optical/infrared scattered light images. On several occasions, I modeled these observations with radiative transfer to constrain the structure of these protoplanetary disks.During this thesis, I have obtained important constraints on the vertical structure of protoplanetary disks, notably by studying a sample of 12 highly inclined disks. I find that the most inclined systems of this survey, where the vertical extent is best seen, are extremely thin at millimeter wavelengths, all the more when compared to their vertical extent seen with scattered light observations (probing smaller grains). This indicates that vertical settling is extremely efficient in these disks, which is favorable for fast grain growth in the disk midplane. Additionally, my study of the Chamaeleon~II star-forming region showed that the distribution of the disk dust mass statistically decreases with time. This is consistent with predictions from viscous evolution. Finally, with the study of a sample of 22 transition disks, I showed that their cavities can mostly be explained by the presence of planets. These results suggest that planets might already have formed in these disks, implying that the timescale available for planet formation is short. A possible mechanism allowing to boost planet formation is vertical settling. Indeed, as detailed previously, my studies showed that the vertical extent of protoplanetary disks is small at millimeter wavelengths, which implies that millimeter sized grains (and larger) are concentrated in a vertically thin midplane where the dust density is increased. Depending on when this vertical settling takes place, this mechanism is a good candidate for enhancing grain growth efficiency. Combined to other processes, vertical settling might allow to form planets in the earliest stages of disk evolution.Une grande diversité est actuellement observée au sein des exoplanètes découvertes. L'étude des disques protoplanétaires permet d'en apprendre plus sur la formation des planètes. En particulier, les disques se dissipent en quelques millions d'années, ce qui implique que les planètes géantes doivent se former très rapidement à partir des petits grains de taille micrométrique présents initialement. Cette thèse vise à ajouter des contraintes observationnelles à plusieurs mécanismes qui contrôlent l'évolution des disques protoplanétaires, et donc la formation des planètes. En particulier, j'ai travaillé sur une étude statistique de la distribution de la masse de poussière dans des disques situés dans la région de formation stellaire Chamaeleon II, sur la présence de cavités dans les disques de transition et sur des contraintes observationnelles de quelques mécanismes d'évolution des poussières tels que la dérive radiale et la sédimentation verticale des grains. J'ai utilisé principalement des observations millimétriques ALMA que j'ai comparées avec d'autres traceurs comme par exemple des images aux longueurs d'onde du visible ou de l'infrarouge. À plusieurs reprises, j'ai modélisé ces observations par transfert radiatif pour contraindre la structure de ces disques protoplanétaires.Au cours de cette thèse, j'ai obtenu d'importantes contraintes observationnelles sur la structure verticale des disques protoplanétaires, notamment en étudiant un échantillon de 12 disques très inclinés. Aux longueurs d'onde du millimètre, les disques les plus inclinés de cette étude, où l'étendue verticale est directement visible, apparaissent extrêmement mince dans la direction verticale, significativement plus mince que les observations en lumière diffusée (grains plus petits). Ceci indique que la sédimentation verticale des poussières est extrêmement efficace dans ces disques, ce qui est favorable à la croissance rapide des grains dans le plan médian du disque. Par ailleurs, en étudiant la région Chamaeleon II, j'ai montré que la distribution de masse des disques diminue statistiquement avec le temps. Ce résultat est en accord avec les prédictions de l'évolution visqueuse des disques. Enfin, l'étude d'un échantillon de 22 disques de transition a permis de montrer que la plupart des cavités de ces disques pourraient être causées par des planètes interagissant avec le disque. Ces résultats suggèrent donc que des planètes se sont peut-être déjà formées dans ces disques, ce qui implique que leur temps de formation est extrêmement court. Le mécanisme de sédimentation verticale des grains est un bon candidat permettant d'accélérer la formation des planètes. En effet, comme décrit précédemment, j'ai montré que l'étendue verticale des grains millimétrique est très faible, ce qui implique que ces grains sont très concentrés dans le plan médian. Une forte densité de poussière étant favorable à une croissance accélérée des grains de poussière, ce mécanisme pourrait être favorable à la formation de planètes très tôt dans l'évolution des disques

Sépultures et ensembles funéraires du second âge du Fer en Île-de France et en région Centre

Environnement, sociétés et archéologie , ISSN 1624-9844; 14 et Annales littéraires de l'Université de Besançon , ISSN 0523-0535 ; 883International audienc

Sépultures et ensembles funéraires du Second Âge du fer en Île de France et en Région Centre

International audienc

Spectro-Photo-Interferometry of Stellar Pulsation (SPIPS)

We present our implementation of the parallax of pulsation method which integrates all observables and physical modelling of the photosphere to get the best statistical precision and controlled biases. This method has been validated on well known stars and used to estimate observationally the projection factor of the HST-FGS sample. Our future developments include application to the Gaia Cepheids and modelling of the spectrum

Spectro-Photo-Interferometry of Stellar Pulsation (SPIPS)

We present our implementation of the parallax of pulsation method which integrates all observables and physical modelling of the photosphere to get the best statistical precision and controlled biases. This method has been validated on well known stars and used to estimate observationally the projection factor of the HST-FGS sample. Our future developments include application to the Gaia Cepheids and modelling of the spectrum