Laboratoire d’Astrophysique de Marseille (LAM) UMR7326 Université d'Aix-Marseille & Centre National de la Recherche Scientifique

38, rue Frédéric Joliot-Curie - 13388 Marseille cedex 13 – France Tél. : +33 (0)4 95 04 41 00 – Fax : +33 (0)4 91 62 11 90 - http://lam.oamp.fr

Marseille, le 05 janvier 2015

Objet : Lettre de recommandation pour Luca Ricci en vue d’une candidature sur un poste de Chargé de Recherche en Section 17 du CNRS

Luca Ricci est un jeune chercheur extrêmement talentueux qui s’intéresse à l’origine et à l’évolution des disques de débris et des disques protoplanétaires, qu’il étudie à l’aide d’observations dans le domaine millimétrique. Luca Ricci collabore avec l'équipe « système solaire et formation planétaire » du LAM depuis bientôt deux ans. Il y a effectué un séjour de trois semaines en 2014 qui a permis de renforcer ses liens avec l'équipe et de lancer de nouvelles pistes de collaborations futures. Les travaux en commun avec des membres de l'équipe se sont traduits à ce jour par l'écriture d’un article en commun dans la revue Astrophysical Journal (Vernazza et al. 2014) ainsi qu’une proposition de temps de télescope acceptée au VLT (Ricci, Vernazza, Vigan, et al. – observations prévues en 2015). Luca Ricci complétera les compétences actuelles de l'équipe, lui permettant d’aborder la problématique de la formation planétaire dans sa globalité en utilisant des moyens d'observations récemment mis en service (ALMA) ou qui le seront (EELT, JWST). Sa venue au LAM permettra d’étudier les ceintures d’astéroïdes et de Kuiper localisés autour d’autres étoiles, à travers la caractérisation des disques de débris mais aussi de faire le lien entre l’observation des disques et les simulations numériques gaz/particules. Ces questions de première importance dans les processus de formation planétaire permettront de faire le lien entre l'étude des petits corps du système solaire et celle des planètes extra-solaires, deux thématiques majeures du LAM. Les discussions scientifiques que nous avons eues avec Luca Ricci témoignent de sa très grande maturité scientifique, d’une grande ouverture d’esprit et d'un esprit visionnaire et ambitieux qui bénéficieraient aussi bien à l'équipe qu'à la communauté scientifique française. Luca Ricci est un observateur hors pair, qui totalise déjà plus de 1000 heures d’observations en PI, principalement dans des observatoires millimétriques. Il a obtenu du temps PI sur ALMA en cycle 0 alors qu’il était encore étudiant en thèse, puis lors des cycles suivants. Cela illustre sa capacité à faire passer ses idées dans un environnement ultra compétitif. Ce sont ces qualités qui lui ont permis d'obtenir successivement deux des plus prestigieux « fellowships » aux Etats-Unis (CARMA à Caltech et SMA à Harvard). Luca Ricci figure parmi les jeunes chercheurs les plus talentueux dans le domaine de la caractérisation des conditions de formation des systèmes planétaires. Il ne fait aucun doute que ce brillant jeune chercheur a toutes les qualités requises pour être recruté au CNRS. Nous ne pouvons que recommander très fortement sa candidature à un poste CR2. Nous vous prions d'agréer l'expression de notre plus haute considération.

Laboratoire d’Astrophysique de Marseille (LAM) UMR7326 Université d'Aix-Marseille & Centre National de la Recherche Scientifique

38, rue Frédéric Joliot-Curie - 13388 Marseille cedex 13 – France Tél. : +33 (0)4 95 04 41 00 – Fax : +33 (0)4 91 62 11 90 - http://lam.oamp.fr

Pierre Barge Audrey Delsanti Astronome Maître de Conférences Laboratoire d’Astrophysique de Marseille Laboratoire d’Astrophysique de Marseille Aix-Marseille Université Aix-Marseille Université Olivier Groussin Laurent Jorda Astronome Adjoint Astronome Adjoint Laboratoire d’Astrophysique de Marseille Laboratoire d’Astrophysique de Marseille Aix-Marseille Université Aix-Marseille Université Olivier Mousis Pierre Vernazza Professeur des Universités Chargé de Recherche CNRS Laboratoire d’Astrophysique de Marseille Laboratoire d’Astrophysique de Marseille Aix-Marseille Université Aix-Marseille Université Institut Universitaire de France

RESEARCH REPORT BY LUCA RICCI

Candidate for the Laboratoire d’Astrophysique de Marseille

1 – OBSERVATIONAL AND TECHNICAL EXPERIENCE

The observational technique I am most familiar with is sub-millimeter/radio interferometry.

Since the first year of my Graduate School I have started to learn the main concepts of radioastronomy instrumentation, computation, and theory. My level of expertise on interferometryhas deepened during my CARMA Fellowship at Caltech first and then my SMA Fellowship atthe Harvard-Smithsonian Center for Astrophysics (current position). CARMA, the CombinedArray for Research in Millimeter-wave Astronomy, and the SMA, the Submillimeter Array, areinterferometric arrays operating at sub-millimeter and millimeter wavelengths. As part of myduties I went to observe at the CARMA site for 15 weeks and I currently observe remotely withthe SMA one day every month.

This experience is being particular useful for two main reasons. The first is to get a practicalfeeling of what are the factors which can affect the results of the observations. This is particu-larly compelling for interferometers, which are very sophisticated systems where several differentcomponents can produce unwanted effects on the data. The second reason why I consider myobserving experience particularly interesting is that it allows me to understand all the main ob-servational steps required to run an astronomical observatory: the scheduling of the observingprojects, the quality assessment of the acquired data, and all the regular procedures needed tomaintain an interferometer. I have also served as a Time Allocation Committee member for theCARMA telescope for three consecutive observing semesters.

Since the beginning of my Graduate School in 2008, I have been the PI of over 40 successfulobservational proposals. The telescopes I used for my research range from sub-mm/radio interfer-ometers (ALMA, CARMA, ATCA, VLA, eMerlin) and single-dishes (APEX), to optical/infraredtelescopes both from the ground (VLT/X-Shooter and Sphere) and from space (HST). For nearlyall these projects I reduced and analyzed the data myself, and this allowed me to gain experiencewith several software packages used to process and reduce astronomical data for facilities operatingat different regions of the electromagnetic spectrum.

As my research experience is mostly focused on deriving observational constraints to the evolu-tionary models of solids in protoplanetary and debris disks, I am familiar with the techniques usedto model interferometric data and Spectral Energy Distributions of these systems. These includeradiative transfer models, Mie codes to derive the dust opacities for a given mixture of chemi-cal elements in the dust grain, and statistical models of solids evolution in gas-rich disks, whichaccount for coagulation, fragmentation and different transport mechanisms of the solid particles.

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2 – RESEARCH EXPERIENCE

My research has been focused on the topics of star and planet formation. Below I provide asummary of the main results obtained so far.

2.1 – The first steps toward planet formation in protoplanetary disks

Circumstellar disks around young stars are the common birth places of planetary systems. In orderto build up planets, the size of solid particles has to grow by more than 12 orders of magnitudesfrom sub-micron dust grains found in the interstellar medium. The first stages of this processof grain growth are characterized by the dynamical interaction between gas and dust, leading tocollisions between the solid particles and finally coagulation (Beckwith et al. 2000).

These processes can be best studied at millimeter/radio wavelengths where the disk is (mostly)optically thin and the emission from the dust in the disk midplane can be observed. Grain growthto centimeter-sized particles can be inferred from measuring the slope of the spectral energydistribution (SED) at these long wavelengths. The dust opacity at mm wavelengths can beexpressed as κν ∝ νβ and the SED becomes Fν ∝ νβ+2 in the optically thin and Rayleigh-Jeansregimes (Beckwith & Sargent 1991). In the diffuse interstellar medium, dust grains are smallerthan 1 µm and βISM ∼ 1.5−2 (Weingartner & Draine 2001). If larger mm-sized grains are presentin the disk, the dust emission is shallower and this reflects in a low value of β compared with βISM.

Since 2008, I have been carrying out a large interferometric survey of about 100 young disksin three separate Star Forming Regions (SFRs) in the Solar Neighborhood spanning a range ofenvironments from isolated star formation (Taurus; Ricci et al. 2010a, 2012a) to moderatelyclustered (Ophiuchus; Ricci et al. 2010b) and highly clustered (Orion Nebula Cluster; Ricci et al.2011). This work showed that the solid growth to mm-sized pebbles is a very fast process, whichappears to occur very early in the evolution of the disk, at ages < 1 Myr (Fig. 1).

Figure 1: Dust opacity spectral index β versusage for disks in different regions and evolution-ary stages (from Ricci et al. 2010b). Red andblue points show disks in the Taurus and Ophi-uchus star forming regions, respectively (Ricci etal. 2010a, b). Their values of β < βISM indi-cate that mm-sized grains have already grown atthis stage and are efficiently retained in the disk.Green and black points show younger sources.The gold arrows show the predictions of modelsof dust evolution in disks, in the cases of clas-sical theory of radial drift of dust grains (upperarrow), and of dust traps slowing down the driftof solids (lower arrow; Pinilla, Ricci et al. 2012).

These observational results have been used to test the physical models of the early evolutionof solids in proto-planetary disks (Birnstiel, Ricci et al. 2010). The presence of these grains is in

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contrast with the phenomenon of fast radial drift toward the central star expected for mm-sizedpebbles in the disk outer regions (probed by mm/radio observations), and due to the aerodynam-ical interaction between dust particles and gas in the disk (Weidenschilling 1977). To explain thedata, mechanisms halting or slowing down the radial drift of solid particles are required (Figure1, Pinilla, Ricci et al. 2012). Interestingly, this problem is directly related to the well known“meter-size barrier” in the inner disk which is hampering our understanding of the formation ofkm-sized planetesimals and therefore of the whole process of planet formation. Several physicalmechanisms have been proposed to overcome this problem, all of which involve the presence of“traps” in the disk which would halt the inward migration of solids and concentrate them in denseregions where growth to large bodies can proceed (Chiang & Youdin 2010).

Recent ALMA and CARMA observations by van der Marel et al. (2013) and Isella, Ricci et al.(2013), respectively, have discovered inhomogeneities in the local distribution of mm-sized solidsin two young disks with an inner cavity likely carved by a massive planet. This is consistent withthe scenario of particle traps in disk systems where a massive planet can catalyze the formationof additional planets and/or a massive debris disk similar to our Kuiper Belt, at larger radii thanwould otherwise be possible. Future observations will be needed to determine whether traps arepresent in disks where there is no evidence for preexisting planets; so, they will shed light on thephysics of planetesimal formation.

2.2 – Disks around young brown dwarfs

The sensitivity limitations of sub-millimeter telescopes in the pre-ALMA era also hampered theinvestigation of disks around brown dwarfs, which are significantly fainter than disks aroundyoung stars (e.g. Scholz et al. 2006). This situation has already started to change with ALMAin Early Science, as shown by a project I am currently leading to characterize dust properties,physical structure and molecular gas emission in disks around young brown dwarfs. This projecthas provided the first direct constraints to the physical structure of brown dwarf disks, the firstdetection of cold molecular gas, and the first evidence for grain growth to sizes of at least 1 mmin these systems (Fig. 2; Ricci et al. 2012b, 2013, 2014a). In the next months I will also obtainALMA data to look for dust and gas around the planetary-mass companion of a nearby youngBrown Dwarf and inform models of satellite formation.

Disks around young brown dwarfs have lower masses than disks around young stars, and thesesystems allow us to probe the early stages of planet formation in low density environments. Ourresults show that the growth of solids to at least ∼ 1 mm in size is a very efficient process, and dustevolution models for disks around brown dwarfs need the presence of dust trapping by pressurebumps to reproduce the observational data (Pinilla, Ricci et al. 2013).

These observations open the doors to studies of key properties of brown dwarfs: the comparisonof the properties of disks around brown dwarfs and stars will further investigate the question ofwhether the bulk of the brown dwarf population is formed like stars or whether brown dwarfformation involves dynamical interaction, as would be suggested if most brown dwarfs disks havemuch less mass and are significantly smaller than disks around young stars. Also, molecular gasemission can be used to trace the disk rotation curve and infer dynamic mass estimate for a sampleof brown dwarfs to calibrate the evolutionary track models of these sub-stellar objects.

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Figure 2: NBC press release on my discovery of mm-sized pebbles in the outer regions of a brown dwarfdisk using ALMA data.

2.3 – The physics of collisions in extra-solar planetesimal beltsand the interaction with planetary systems

Observations of debris disks made of cold dust around main-sequence stars can provide crucialinformation to the process of planet formation. The dust grains observed in these systems arisefrom the material left over from the formation of planets, being continuously replenished bycollisions of larger bodies, such as comets and asteroids (see e.g. Wyatt 2008). Whereas optical-to-infrared observations of disks trace small ∼ µm grains which are easily pushed away by radiationpressure from the stellar photons, mm-grains traced by observations in the sub-millimeter areinsensitive to radiation pressure and trace the location of the large bodies.

Observations of debris disks in the sub-mm are crucial also to test the physics of the stirringand collision of asteroids/comets. Because of their extremely faint emission, these large bodiescannot be directly observed. However, information on their physical and dynamical properties canbe extracted from the size distribution of the emitting smaller dust grains. Observations in themillimeter have the potential to determine the size distribution of ≈ 1-10 mm-sized dust grainsand can test the collisional models of asteroids/comets in debris disks.

The stirring of planetesimals to initiate collisions may be due to the gravity of Pluto-sizedobjects forming within the debris disks (Kenyon & Bromley 2004), or triggered by dynamicalinteractions with fully formed planets (Mustill & Wyatt 2009). In either case, the reference modelfor dust production is the steady state collisional cascade model of Dohnanyi (1969), which resultsin a power-law grain size distribution (n(a) ∝ a−q) with an exponent q = 3.51. Recent, moresophisticated numerical simulations for the dynamics and material physics of the colliding bodiespredict steeper power laws, i.e. q ≈ 3.8− 4 (Pan & Schlichting 2012). It is also possible that thecollisional cascade picture is entirely incorrect and debris disks are actually more like planetary

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Figure 3: Left) ATCA image at 7 mm and SED at mm-wavelengths of the Fomalhaut debris disk.From the spectral slope, Ricci et al. (2012c) estimated the slope of the grain size distribution and testedthe collisional models of planetesimal belts. Right) ALMA map at 0.87 mm of the debris disk aroundthe HD 107146 Solar-like star. The map shows a broad belt of dust from ∼ 30 to 150 AU from the star.The decrease in surface brightness at intermediate radii is consistent with the presence of a super-Earthplanet with an orbital radius of ∼ 80 AU which has carved a gap in the disk (Ricci et al. 2014b).

rings, where relative velocities are small and collisions are gentle, and the resulting size distributionis shallower, q = 3.0 (e.g. Saturn rings, Zebker et al. 1985).

Ricci et al. (2012c) measured the millimeter spectral index of the Fomalhaut debris disk andshowed how this parameter encodes information on the q-value for mm-sized dust in debris disks(Fig. 3, left). We derived q = 3.48 ± 0.14 for the case of Fomalhaut, a value in line with thestandard Dohnanyi (1969) model, but only marginally consistent with the modern models thatconsider size-dependent velocities and tensile strengths for the dust producing bodies.

I am currently collecting new VLA and ATCA mm-wave data for a dozen of debris disks. Bycombining these data with literature data in the sub-mm, I will start to investigate the distributionof q-values in debris disks. Understanding whether the q-slope of the grain size distribution isuniversal in debris disks or if instead varies with the properties of the central star and/or of thedisk will provide important observational constraints to the collisional models in debris disks.

Recently, I have been leading an ALMA project to study the structure of the debris disk aroundthe young, ∼ 100 Myr old, solar analog HD 107146. The ALMA map reveals a broad belt of dust,extending from about 30 to 150 AU from the star, and an intriguing decrease in surface brightnessat intermediate radii (Fig. 3, right). The decrease in surface brightness suggests the presence oftwo separated asteroid/comet belts. The size and location of the separation between these twobelts suggest the presence of a super-Earth planet which is sculpting a gap in the disk (Ricci etal. 2014b). This is similar to the case of our Solar System in which giant planets shape withtheir gravity the architecture of the Kuiper belt. Although future ALMA observations with betterangular resolution and sensitivity are needed to definitely confirm this structure, these resultsdemonstrate the potential of ALMA to indirectly probe terrestrial planets at wide separationsfrom the host star.

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2.4 – The HST and ALMA Program on the Orion Nebula Cluster

Since 2007 I have been part of the Hubble Space Telescope (HST) Treasury Project on the OrionNebula Cluster (ONC), the longest project ever dedicated with HST to the topic of star formation(Robberto et al. 2013). These observations have been used to characterize properties such asmass, age, variability of more than 3000 young stars with unprecedented accuracy.

Scientific highlights from this project include the characterization of over 200 young disksobserved as externally ionized disks (the famous Orion “proplyds”; Ricci et al. 2008; Fig. 4), areexamination of the star formation history in this benchmark region (Reggiani, Ricci et al. 2011),the discovery of the first binary system made of very young brown dwarfs which are still accretingand enshrouded in a circumbinary disk (Robberto, Ricci et al. 2008).

These disks are being targeted by an ongoing ALMA project which I am part of, to investigatethe effects of the high-energy radiation produced by massive stars on the structure and evolutionof young disks. The first results show a clear correlation between the sub-mm flux density, pro-portional to the dust mass in the disk, and the projected separation to the most massive star inthe cluster (Mann et al. 2014). This result demonstrates the strong effects on disk evolution ofexternal photo-evaporation by the high energy photons from a massive star, and has profoundimplications for planet formation in high-density stellar clusters.

Figure 4: HST image of the Orion Nebula Cluster from the Treasury Program (credits: NASA/ESA, M.Robberto, HST Treasury Program on the Orion Nebula Cluster team). The six overlaid smaller imagesshow the zoom in of young circumstellar disks (credits: NASA/ESA and Luca Ricci).

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RESEARCH PROJECT

3 – The Formation and Early Evolution

of Planetary Systems

Circumstellar disks surrounding young stars are commonly considered as the cradles for planets(Figure 5). These fascinating astrophysical systems play a key role in the formation of planetsbecause it is from the solids contained in them that rocky planets can be assembled. The atmo-sphere of gas giant planets is made of gas from the disk that has been gravitationally capturedfrom massive rocky cores. Disks are crucial also for determining the architecture of planetary sys-tems as the gravitational interaction between planets and the disk can greatly modify the planetorbital parameters.

Figure 5: Image composition for five Orion proplyds observed under the HST Treasury Program on theOrion Nebula Cluster (Ricci et al. 2008). Credit: http://www.spacetelescope.org/news/heic0917

Press Release, NASA/ESA and L. Ricci.

Despite all the success of exoplanets detections and all the theoretical work in the field, littleis known about fundamental processes involved in the assembly of planetary systems and in theplanet-disk interaction acting in real disks. As we step into the era of a massive upgrade intechnical capability, thanks to the construction of the Atacama Large Millimeter/submillimeterArray (ALMA), the Square Kilometre Array (SKA) in the future, and the upgrade of the Plateaude Bure Interferometer (PdBI and later on NOEMA) and Very Large Array (VLA), we can nowinvestigate for the first time the structure of disks down to scales of a few Astronomical Units.Combining observations at optical/infrared is required to investigate solids with different sizes andin different locations of the disks, as well as to detect newly born planets which are still embeddedin their natal disk. The “Solar System and planetary formation” research team at LAM has a greatexpertise in optical/infrared observations of these systems. My expertise at longer wavelengthswill be fundamental to provide critical tests to the models of planet formation as detailed in thenext sections.

Also, a strong interaction between observations and simulations is needed to model physicalstructures which are predicted by theory to trigger local concentrations of solids and thereforeplay a key role in the formation of asteroids and planets. A close collaboration with Pierre Bargeat LAM whose expertise focuses on the modeling of these processes will be crucial. This will allowto study with unprecedented detail the key processes involved in the formation andearly evolution of planetary systems.

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Figure 6: Spectral Energy Distributions of diskmodels obtained by varying the dust mass in thedisk as labelled. The figure shows how infraredobservations are not sensitive to emission fromthe bulk of dust in the disk and can not mea-sure its mass. Sub-millimeter emission is opti-cally thin and observations at these wavelengthscan measure the dust mass in the disk.

3.1 – The evolution of disks around young stars and brown dwarfsand their potential to form planets

Planets form in the disks of gas and dust that orbit young stars and brown dwarfs. Understand-ing how the mass of disks evolves with time is crucial to set the timescale for theassembly of planets and inform the theoretical models of planet formation. Observa-tions in the infrared have shown that dust in the innermost regions of the disk (< 1 AU) dissipateson a timescale of few Myr (Hernandez et al. 2008). However, infrared observations do not probethe disk outer regions where the bulk of the disk mass resides (Fig. 6), and they are not sensitiveto gas in the disk, which is thought to be orders of magnitude more abundant than dust in mass.The key diagnostics of the outer disk properties are sub-millimeter observations in the dust con-tinuum and molecular gas spectral lines. Only large sub-mm surveys of disks in regionswith different ages and surrounding stars and brown dwarfs of different masses canallow us to answer the following questions, which are key for our understanding ofplanet formation and disk evolution:

• How do the dust and gas mass of disks evolve with time?

• What is the relation between disk mass and stellar mass and how does this relation behaveacross the hydrogen burning limit?

• How do the properties of disks at different ages compare with the masses and architecturesof exo-planetary systems which are formed out of those disks?

So far, extensive sub-mm surveys of disks in nearby Star Forming Regions (SFRs) have beenstrongly hampered by the limitations in sensitivity of telescopes at these wavelengths. Only inone region, i.e. the ∼ 1 Myr old Taurus SFR, more than ∼ 30% of the disks have been observedand detected in the sub-mm (Andrews et al. 2013). This situation has just started to improvedramatically with ALMA, whose unprecedented sensitivity allows for deep sub-mm surveys of alldisks in a single region in just a few hours of observing time. In collaboration with J. Carpenterat Caltech we are currently analyzing ALMA data for disks in the ∼ 5 Myr old Upper Sco region,and other ALMA data for a sample of 5− 20 Myr old disks are expected by the end of 2015 (first

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results in Carpenter, Ricci et al. 2014). At the same time I am carrying out a large survey ofdisks with the CARMA millimeter interferometer to measure the mass of all the disks known inthe younger Taurus and Ophiuchus SFRs.

The unprecedented sensitivity of ALMA allows to carry out surveys of disks also around youngbrown dwarfs, which are significantly fainter than disks around young stars as also shown by thefirst results of my ALMA project on brown dwarf disks (Sect. 2.2; Ricci et al. 2013). By 2015I will obtain new ALMA observations for a sample of young brown dwarfs disks in Ophiuchus.These new observations will start to probe the initial mass function of disks around very youngbrown dwarfs, and infer their potential to form rocky planets as well as more massive gas giantplanets at an age of ∼ 1 Myr.

In the future I plan to continue to use ALMA to carry out extensive sub-mm surveys ofdisks in regions with different ages surrounding stars and brown dwarfs with different masses.With the large samples of disks that will be targeted by ALMA I will investigate trendsbetween disk and stellar/sub-stellar properties which are crucial for our understanding of themechanisms driving the evolution of young disks. This investigation will go in parallel with theever growing sample of detected exoplanets, and statistical comparisons between the propertiesof disks and of exoplanets around stars and brown dwarfs with different masses will be key forour understanding of planet formation.

3.2 – The formation of planets in young gas-rich disksand the physics of planet migration

Whereas the detection of exoplanets has now become routine, the formation of planetarysystems and the physical processes which set their final architecture remain to beunderstood. What is clear is that giant Jupiter-like planets are formed in gas-rich primordialdisks, whereas rocky Earth-like planets can be finally assembled at a later stage, also called “debris-disk” stage, when disks have dissipated their gas and a belt of asteroid- or comet-like bodies isleft in the system. It is also clear that the interaction between the planet and either the gas inthe primordial disk stage or the asteroid/comet belt in the debris disk stage can greatly modifythe planetary orbits. However, several important questions still need to find an answer:

• Under which physical conditions and in which types of disks do planets form?

• How do planets interact with their natal disk? How does this interaction affect the mecha-nism of planet migration?

• How is the mass transported from the disk onto the forming planets?

Whereas several theoretical ideas have been proposed in the past to describe these phenomena,high angular resolution observations of young gas-rich disks where these processes are“caught in the act” are needed to determine their main properties in real systems.

Another reason why observations of young gas-rich disks are particularly compelling is that,while the direct detection of a forming planet still embedded in its parental disk is very difficult

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Figure 7: Left and center panels) Simulated 0.85 mm ALMA continuum observations of a formingplanetary system around a solar type star at the distance of 130 pc. The system contains three planetsof 0.3, 1, and 5 MJupiter orbiting at 10, 15 and 25 AU, respectively. The red circle on the right panelshows the ALMA beam. Right) ALMA image of the HL Tau disk showing the presence of multiple ringsand gaps (https://public.nrao.edu/news/pressreleases/planet-formation-alma).

at any wavelength with current technology, indirect evidence for forming planets can beobtained by looking at the spatial distribution of matter in the disk. Planets interactwith the disk creating azimuthal asymmetries such as spiral arms or radial gaps. Theirproperties depend on the mass and orbit of the planet, thus leaving fingerprints onthe distribution of gas and dust in the disk.

The new mm/radio facilities, such as the improved PdBI and more importantly ALMA, havejust started to probe the distribution of matter in disks at unprecedented spatial resolutions andsensitivities. In fact, evidence for azimuthal asymmetries has already been obtained in some disksby ALMA in Early Science (Casassus et al. 2013, van der Marel et al. 2013). When ALMA willhave reached its maximum sensitivity and angular resolution in a few years, we will be able toinvestigate sub-structures on scales down to few AU in the disk, which are expected as a result ofthe gravitational interaction between the disk and one or more (proto-)planets.

This is demonstrated in figure 7 which shows ALMA simulated observations (center panel) of aforming planetary system in a young gas-rich disk obtained using the FARGO hydrodynamic code(left), as well as very recent ALMA observations of a real disk with very high angular resolution(right). The ALMA simulated observations reveal the presence of radial gaps and spiral arms in thedust emission, as well as the circum-planetary disk around the most massive planet. Observationslike the one presented here for the dust, combined with optically thin gas tracers, will determinekey properties such as density and morphology of the spiral arms and of the circum-planetarydisk, and the density contrast between the region inside and outside the gap. These are all crucialquantities for models of mass transfer from the disk onto the planet as well as of the phenomenonof planet radial migration, invoked to explain the existence of hot Jupiters, and given as an effectof the spiral arms that ALMA can probe directly. Recent ALMA observations of the HL Tauyoung disk show multiple concentric rings separated by well defined gaps (Fig. 7, right). Thesestructures suggest that planet formation is already well underway within the first Myr of age of

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the disk.

I am currently leading a VLA project and collaborating with colleagues at Caltech to char-acterize asymmetries in young disks with millimeter observations at high angular resolution andrelate them to the properties of the planet (mass and orbital radius). To this aim I will obtain newALMA data in 2015 of primordial gas-rich disks which show hints of the presence of sub-stellarcompanions from observations in the near-IR. I started recently a collaboration with Pierre Bargeat LAM to investigate the motion of solids in disks with asymmetries in gas, which is crucial forthe interpretation of the observations.

In the future I plan to continue to use sub-mm and radio interferometers to observe disks athigh angular resolution. While detailed characterization of few disks will be performed in thefirst years of ALMA, high-res observations of a large sample of disks with different properties,required to understand under which conditions the key mechanisms related to planet forma-tion can occur, will require longer times and go on till the 2020 decade and beyond. Theseobservations will identify young disks with clear signatures of embedded protoplanets. Theywill be natural candidates for follow up observations to directly detect forming planets withhigh-res observations in the optical and infrared using the new 30m ground based telescopes(EELT, TMT) as well as JWST, that will become available in those years.

3.3 – The interaction between planetary systems and Kuiper belts

telescopes have identified hundreds of main-sequence stars where the observed fluxes at infraredwavelengths are brighter than the stellar photosphere (see review by Wyatt 2008). This “excess”infrared emission is attributed to dust that is produced when planets gravitationally stir a popu-lation of kilometer-sized planetesimals (asteroids and comets), which subsequently collide and areground down to micron-sized “debris” particles. Contrary to the younger primordial disks, debrisdisks contain no, or very little, gas.

Mapping the structure of debris disks is crucial since the spatial distribution ofdust and larger bodies is a powerful diagnostic of the evolution of planetary sys-tems (Ozernoy et al. 2000, Kuchner et al. 2003). Planets interact gravitationally to sculpt thedisk by (i) scattering solids out of the disk, (ii) secular (long-term) planetary perturbations, and(iii) capturing dust and larger bodies in mean motion resonances as particles drift inwards fromPoynting-Robertson drag or as planets migrate outwards.

A proof of the importance of the planet-disk interaction in shaping the architecture of planetarysystems is given by our own Solar System, where current theory invokes scattering at early agesof a large population of planetesimals by the giant planets to explain a variety of Solar Systemfeatures, including the the architecture of the inner Solar System, the compositional distributionof asteroids as well as the small mass of Mars compared to Earth (Walsh et al. 2011). The SolarSystem allows to study in great detail the outcome of these mechanisms. At the same time, thisrepresents just one of the several possible outcomes, and the investigation of the astrophysicalsystems where these mechanisms are currently taking place is the best way to furtherinvestigate the gravitational interplay between Kuiper belts and planetary systemsand put the case of our Solar System in context. Investigating the location and

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distribution of solids in disks with massive planetesimals belts around relatively youngmain-sequence stars is therefore crucial to study the dynamic history of planetarysystems beyond our Solar System.

High-angular resolution imaging at sub-millimeter wavelengths is the only tool to accuratelydetermine the location of planetesimal belts in debris disks. While optical/infrared observationsprobe small µm-sized grains which are strongly affected by radiation pressure from the stellarphotons, sub-mm observations are sensitive to larger mm-sized grains dominated by collisions andgravitational interactions and remain co-located with the planetesimals (Wyatt 2006).

To date, resolved millimeter wavelength images are available for a dozen of debris disks. In somecases, the images show clumpy rings of material that may be consistent with dust grains trappedin resonance but because of the low signal-to-noise ratio of these structures no unambiguous casehas been identified so far (e.g. Holland et al. 1998, Pietu et al. 2011, Hughes et al. 2011).

With its unprecedented sensitivity, ALMA has already started to change the field. I amleading an ALMA project to investigate the spatial distribution of dust in the debris disk aroundHD 107146, a nearby solar analog with an age of 100 − 200 Myr. The ALMA map shows tworings at distances of about 45 and 100 AU from the central star. This suggests dynamical clearingof a gap by one (unseen) planet located between the two rings, similarly to the role of the outerplanets in our Solar System in shaping the morphology of the asteroid and Kuiper belts. A planetwith a mass of just a few Earth masses would be responsible for gravitationally sculpting that disk(Ricci et al. 2014b). This shows the potential of ALMA to indirectly probe terrestrial planets atwide separations from the host star, possibly revealing a population of exo-planets which cannotbe detected by any other method. Together with Arthur Vigan and other researchers at LAM Irecently obtained telescope time to look for Jupiter sized planets at few AUs from the star withthe new SPHERE camera on the VLT.

Future observations with ALMA will better constrain the structure of these rings and relatethem to the properties (mass and orbit) of the planet sculpting them. Figure 8 presents simulatedALMA observations of a debris disk model created in collaboration with the Marc Kuchner’s groupat the NASA Goddard Space Flight Center. The model was generated using the SMACK code(Nesvold et al. 2013) and reproduces a debris disk with characteristics similar to HD 107146. Aplanet like Jupiter was placed in the debris disk at an orbital radius of 80 AU. The planet interactswith the planetesimals in the disk and mm-sized grains are produced by the collision of these largebodies and remain co-located with the planetesimal belts where they form.

This simulation nicely illustrates the potential of ALMA to directly probe the dynamical inter-action between a planet and one or more planetesimal belts. ALMA observations can determinethe actual width of gaps cleared by planets in debris disks. This will constrain the mass of planetsembedded in disks, as the gap width is proportional to the mass of the planet to the 1/3 power(Gladman 1993). Therefore, ALMA will measure gap widths in debris disks, discover planetssurrounded by massive planetesimal belts, as well as measure their mass and orbital radius.

This simulation also shows how ALMA can reveal the presence of azimuthal asymmetries inthe dust emission in the case of an embedded planet with a mass of 1 MJup. These are dueto the collisions of planetesimals trapped in resonance along the orbit of the planet, i.e. trojanplanetesimals. The location, density, contrast, and number of asymmetries will constrain the

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Figure 8: Left) Synthetic map of a debris disk model with a Jupiter mass planet (shown as ayellow dot) perturbing the disk. The structure of the debris disk resembles the main properties ofthe HD 107146 disk. Right) ALMA simulated observations at 0.87 mm of the same model. Themap clearly recovers the two-ring structure of the models as well as dust trapped in resonancealong the planet orbit, as shown by the red arrow.

mass, orbit, and migration rate of the planet (Kuchner et al. 2003).

The characterization of extra solar asteroid and Kuiper belts will allow us to shed light on thephysical mechanisms which drove to the present architecture of our Kuiper belt. At the same time,the detailed knowledge of solids in the Solar System, which is a key area of expertise of the “SolarSystem and planetary formation” research team at LAM, can provide important information tounderstand the origin of dust in extra solar systems. With P. Vernazza, we have collected all thedebris disks with infrared spectra which show spectral lines in dust emission. With the aim ofinvestigating the origin of the dust in these systems, we are now comparing those lines with knownspectral features of meteorites and asteroids from our Solar System.

In the future I plan to use ALMA to constrain the structure of planetesimal belts beyondour Solar System. Similarly to the case of younger gas-rich disks, the combination of ALMAand the new ground-based 30m telescopes in the optical and infrared together with JWSTwill allow us to fully characterize planetary systems and their interplay with massive Kuiperbelt-like systems. This investigation will be crucial for our understanding of the processescontrolling the early evolution and final architecture of planetary systems such as our own.

References: Andrews et al. 2013 ApJ 771 129 ? Beckwith et al. 2000 PPIV 533 ? Beckwith & Sargent 1991ApJ 381 250 ? Birnstiel et al. 2010 A&A 516L 14 ? Casassus et al. 2013 Nature 493 191 ? Chiang & Youdin 2010AREPS 38 493 ? Dohnanyi 1969 JGR 74 2531 ? Hernandez et al. 2008 ApJ 686 1195 ? Holland et al. 1998 Nature392 788 ? Hughes et al. 2011 ApJ 740 38 ? Isella et al. 2013 ApJ 775 30 ? Kenyon & Bromley 2004 AJ 128 1916 ?Kuchner & Holman 2003 ApJ 588 1110 ? Mustill & Wyatt 2009 MNRAS 399 1403 ? Nesvold et al. 2013 ApJ 777144 ? Ozernoy et al. 2000 ApJ 537 L147 ? Pan & Schlichting 2012 ApJ 747 113 ? Pietu et al. 2011 A&A 531L 2? Pinilla et al. 2012 A&A 538 114 ? Pinilla et al. 2013 A&A 554 95 ? Reggiani et al. 2011 A&A 534 83 ? Ricciet al. 2008 AJ 136 2136 ? Ricci et al. 2010a A&A 512 15 ? Ricci et al. 2010b A&A 521 66 ? Ricci et al. 2011A&A 525 81 ? Ricci et al. 2012a A&A 540 6 ? Ricci et al. 2012b A&A 761L 20 ? Ricci et al. 2012c A&A 539L6 ? Ricci et al. 2013 ApJ 764L 27 ? Robberto et al. 2008 ApJ 687L 83 ? Robberto et al. 2013 ApJS 207 10 ?Scholz et al. 2006 ApJ 645 1498 ? van der Marel et al. 2013 Science 340 1199 ? Walsh et al. 2011 Nature 475 206? Weidenschilling 1977 MNRAS 180 57 ? Weingartner & Draine 2001 ApJ 548 296 ? Wyatt 2006 ApJ 639 1153 ?Wyatt 2008 ARA&A 46 339 ? Zebker et al. 1985 Icarus 64 531

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4 – Adequacy of my research project with the Laboratoire

d’Astrophysique de Marseille (LAM)

The main objective of the research team “Solar system and planetary formation” at the Laboratoire d’Astrophysiquede Marseille (LAM) is to constrain the formation and evolution of planetary systems. At LAM, this is achieved bystudying:

• The dynamical evolution of gas-rich protoplanetary disks via numerical simulations – P. Barge.

• The physico-chemical properties of solar system bodies, mainly small bodies but also planets like Mercury,via ground- and spaced-based observatories (visible and infrared) and in-situ space missions (Rosetta, Bepi-Colombo, Juice) – A. Delsanti, O. Groussin, L. Jorda, O. Mousis and P. Vernazza.

At LAM, the exploration via observations of the initial steps of planetary formation and evolution (disk phases;steps a) and b) in Fig. 10) is the only piece currently missing for the team in order to observationally constrainthe entire formation sequence. My research project, which focuses on the early stages of planetaryformation, will perfectly complement the current expertise at LAM, thus providing a completecoverage of the entire planetary formation sequence (Fig. 9).

Figure 9: Simplified view of the formation sequence of planetary systems like the Solar System. Here Ihighlight the current observational expertise at LAM and how my contribution will complement it, thusproviding a complete coverage of the entire planetary formation sequence.

Last summer I spent 3 weeks at LAM and started fruitful collaborations with a number of researchers. I startedto collaborate with Pierre Barge, whose research focuses on numerical simulations to model the formation, stabilityand evolution of gaseous structures in primordial disks and their impact on the planetary formation mechanisms.We are now running dynamical simulations of solids in disks with asymmetries in gas which will be crucial for theALMA observations that I will obtain in 2015 and that will allow us to study the properties of gas in disks withunprecedented detail. A strong interaction between observations and simulations is needed to modelgaseous structures, e.g. dead-zones, hydrodynamical Rossby-wave instabilities, condensation fronts (like the“snow-line”), which are predicted by theory to trigger local concentrations of solids and thereforeplay a key role in the formation of asteroids and planets.

The collaboration with P. Barge is useful also for the whole team, since my project makes the link betweenthe hydrodynamical simulations of the early stages and the observations of the later stages of the evolution of

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planetary systems. Together with Arthur Vigan, Pierre Vernazza and P. Barge we have recently obtained telescopetime with the new SPHERE camera on the VLT to look for Jupiter sized planet in a debris disk that I recentlyobserved with ALMA. This is only the first of a series of observations that our group plans to design to investigatethe connection between debris disks and planetary systems.

Importantly, I will not only complement the existing competences via the observation of protoplanetary disksand exoplanets but also benefit from the interaction with the team to open a new field of exploration and broaden theresearch field of the team. Indeed, a fundamental science question that is of interest to the team is the explorationof small bodies in extra solar systems, namely the discovery and characterization of extra solar Asteroid and Kuiperbelts. With P. Vernazza, we have collected all the debris disks with infrared spectra which show spectral lines indust emission. With the aim of investigating the origin of the dust in these systems, we are now comparing thoselines with known spectral features of meteorites and asteroids from our Solar System.

Finally, I will bring my strong expertise in sub-millimeter and radio observations to complementthe observing skills of the team in the visible and infrared domains. Specifically, my expertise will beextremely beneficial for the observation of outer solar system small bodies (comets and trans-Neptunian objects)with ALMA (see Fig. 10).

Figure 10: Observational expertise of the team at LAM as well as mine.

15

Luca Ricci

Center for Astrophysics - Harvard60 Garden St, MS 78

02138 Cambridge, MA, USA

Phone: (+1) 626-200-9079

Email: lucaricci83@gmail.comCitizenship: ItalianDate of Birth: 17th December 1983

Research Interests

Star and Planet Formation, Origin and Evolution of Protoplanetary Disks and Debris Disks, Exoplanets,Sub-millimeter and Radio Interferometry.

Professional Experience

• SMA Fellow, Harvard - Smithsonian Center for Astrophysics, USA, since November 2014.

• CARMA Fellow, California Institute of Technology, USA, 2011–2014.

• International Max Planck Research School (IMPRS) Graduate Student, ESO, Germany, 2008–2011.

• Summer Intern with Dr. Massimo Robberto, STScI, USA, 2008.

• Summer Intern with Dr. Massimo Robberto, STScI, USA, 2007.

Education

• Ph.D. Astronomy, European Southern Observatory and Ludwig-Maximilians MunichUniversity, Germany (Advisor: Leonardo Testi), September 2011.

• M.A. Astrophysics, Milan University, Italy, 2008.

• B.S. Physics, Milan University, Italy, 2006.

Honors & Awards

• SMA Postdoctoral Fellowship, Harvard - Smithsonian Astrophysical Observatory, 2014–present.

• CARMA Postdoctoral Fellowship, Caltech, 2011–2014.

• Graduate Research Fellowship, International Max Planck Research School, ESO, 2008–2011.

• Undergraduate Fellowship, Institute for the Rights to the University Studies, Milan University, 2003–2007.

Luca Ricci 2

Skills

Observing Experience

Awarded more than 1000 hours of observing time as PI for the following astronomical facilities:

• Atacama Large Millimeter Array (ALMA)

• Atacama Pathfinder EXperiment (APEX)

• Australian Telescope Compact Array (ATCA)

• Combined Array for Research in Millimeter Astronomy (CARMA)

• Electronic Multi-Element Remotely Linked Interferometer Network (e-MERLIN)

• Submillimeter Array (SMA)

• Very Large Array (VLA)

• Very Large Telescope (VLT)

Programming/Software

• IDL, Fortran, C, CASA, MIRIAD.

Outreach & Media Activities

• Swarms of Pluto-Size Objects Kick-Up Dust around Adolescent Sun-Like Star, NRAO Press Release(https://public.nrao.edu/news/pressreleases/swarm-pluto-alma), Dec 2014.

• Death Stars in Orion Blast Planets before They Even Form, NRAO Press Release(https://public.nrao.edu/news/pressreleases/death-stars-in-orion), Mar 2014.

• Even Brown Dwarfs May Grow Rocky Planets, Joint ESO (http://www.eso.org/public/news/eso1248/)and NRAO (http://www.nrao.edu/pr/2012/browndisks/) Press Release, Nov 2012.

• Born in beauty: proplyds in the Orion Nebula, Hubble European Space Agency Press Release(http://www.spacetelescope.org/news/heic0917/), Dec 2009.

• Writing of scientific articles for the Italian online newspaper “Il Sussidiario.net”, Jan 2010–present.

• Collaboration with Euresis (“Association for the promotion and development of culture and scientific work”)for the preparation of the scientific exhibition “Why so many lights? The Milky way on Science, Historyand Art”, 2006.

• Presentation to the public of several Euresis scientific exhibitions throughout Italy, 2005–2008.

Luca Ricci 3

Teaching & Student Mentoring

• Paolo Cazzoletti, Milan University, M. A. Thesis Research Project, 2014–present.

• Naoki Eto, Caltech, Undergraduate Research collaboration, 2014.

• Betsy Fu, Caltech, Summer Undergraduate Research Fellow, 2013.

• Anna Miotello, Milan University/European Southern Observatory, M. A. Thesis Research Project,2012–2013.

• Planning and teaching of lessons on Math and Physics for Undergraduate students, Milan University,Italy, 2003–2006.

• Tutoring at the Study Help Center “Portofranco” for High School students, Milan, Italy, 2002–2008.

Selected Contributed Talks

11. Revolution in Astronomy with ALMA Conference, Tokyo, Japan, 2014.

10. Characterizing Planetary Systems Across the HR Diagram Conference, Cambridge, UK, 2014.

9. Brown Dwarf: come of age Conference, Fuerteventura, Spain, 2013.

8. Transformational Science with ALMA: From Dust to Rocks to Planets: Formation and Evolution of PlanetarySystems, Big Island, Hawaii, 2013.

7. The First Year of ALMA Science Conference, Puerto Varas, Chile, 2012.

6. Planet Formation and Evolution 2012, Munich, Germany, 2012.

5. The Origins of Stars and their Planetary Systems, Hamilton, Canada, 2012.

4. 7th Planet Formation & Evolution Workshop, Goettingen, Germany, 2011.

3. Putting our Solar system in context: origin, dynamical and physical evolution of multiple planet systems,Obergurgl, Austria, 2010.

2. The origin and fate of the Sun: evolution of Solar-mass stars observed with high angular resolution, Garchingbei München, Germany, 2010.

1. From circumstellar disks to planetary systems, Garching bei München, Germany, 2009.

Additional Talks

13. Astronomy Colloquium (invited), NRC - HIA, Victoria, Canada, 2014.

12. Astronomy Colloquium (invited), University of British Columbia, Canada, 2014.

11. Star and Planet Formation Seminar (invited), Laboratory of Astrophysics, Marseille, France, 2014.

10. CfA Talk (invited), Harvard, 2013.

9. Observer’s Lunch Talk (invited), Steward Observatory, Arizona, 2012.

8. iPLEX Lunch Talk (invited), UCLA, 2012.

Luca Ricci 4

7. ESO Lunch Talk (invited), ESO, 2012.

6. IPAC Lunch Talk (invited), Spitzer Science Center, 2010.

5. Star and Planet Formation Seminar (invited), Caltech, 2010.

4. Radio and Geoastronomy Lunch Talk (invited), CfA - Harvard, 2010.

3. ESO Science Day, ESO, 2010.

2. ESO Journal Club, ESO, 2009.

1. ESO Science Day, ESO, 2009.

Professional Service

• Referee for Scientific Journals:

- The Astrophysical Journal, 2012–present,

- Astronomy & Astrophysics, 2013–present.

• Next Generation Very Large Array (NGVLA) Cradles of Life working group member, 2014 –present.

• Cerro Chajnantor Atacama Telescope (CCAT) ISM/Star Formation working group member, 2012

– present.

• Time Allocation Committee member, CARMA Telescope, 2012 – 2013.

• Scientific Organizing Committee member and Session Chair, CARMA Symposium, Chicago, IL,July 2013.

• Caltech Tea Talks organizer, 2013 – 2014.

• Caltech Summer Research Program reviewer, 2014.

Referees

• Anneila I. Sargent (Ira S. Bowen Professor of Astronomy, Vice President for Student Affairs, Caltech),email: afs@astro.caltech.edu.

• Leonardo Testi (ALMA European Project Scientist, ESO), email: ltesti@eso.org.

• John M. Carpenter (Owens Valley Radio Observatory Executive Director, Caltech),email: jmc@astro.caltech.edu.

Luca Ricci 5

Publication List (11 first author, 5 second author, 37 total)

37. L. Ricci, J. M. Carpenter, B. Fu, A. M. Hughes, S. Corder, & A. Isella ALMA observations of the debrisdisk around the young Solar Analog HD 107146, ApJ, in press, arXiv:1410.8265, 2014.

36. J. P. Williams, R. K. Mann, J. Di Francesco, S. M. Andrews, A. M. Hughes, L. Ricci, J. Bally, D.Johnstone, & B. Matthews ALMA observations of a misaligned binary protoplanetary disk system in Orion,ApJ, in press, arXiv:1410.3570, 2014.

35. I. Pascucci, L. Ricci, U. Gorti, D. Hollenbach, N. P. Hendler, K. J. Brooks, & Y. Contreras Low EUVluminosities impinging on protoplanetary disks, ApJ 795, 1, 2014.

34. S. Facchini, L. Ricci, & G. Lodato Probing planets in transition discs’ cavities via warped discs, MNRAS442, 3700, 2014.

33. L. Ricci, L. Testi, A. Natta, A. Scholz, I. de Gregorio-Monsalvo, & A. Isella Brown dwarf disks withALMA, ApJ 791, 20, 2014.

32. S. M. Andrews, C. Chandler, A. Isella, T. Birnstiel, K. Rosenfeld, D. Wilner, L. Perez, L. Ricci, et al.Resolved multifrequency radio observations of GG Tau, ApJ 787, 148, 2014.

31. A. Isella, C. Chandler, J. Carpenter, L. Perez, L. Ricci Constraints on the LkCa 15b Circumplanetary diskmass from VLA observations at 7 mm, ApJ 788, 129, 2014.

30. J. Carpenter, L. Ricci, & A. Isella Submillimeter constraints on the evolution of circumstellar disks, ApJ787, 42, 2014.

29. C. Manara, L. Testi, A. Natta, L. Ricci, M. Benisty, G. Rosotti, & B. Ercolano On the gas content oftransitional disks: a VLT/X-Shooter study of accretion and winds, A&A, in press, 2014.

28. A. Miotello, L. Testi, G. Lodato, L. Ricci, K. Brooks, G. Rosotti, A. Maury, & A. Natta Grain growth inthe envelopes and disks of Class I protostars, A&A 567, 32, 2014.

27. P. Vernazza, B. Zanda, R. Binzel, T. Hiroi, F. DeMeo, M. Birlan, R. Hewins, L. Ricci, P. Barge, & M.Lockhart Multiple and fast: the accretion of planetesimals, ApJ, in press, 2014.

26. L. Testi, T. Birnstiel, L. Ricci, S. Andrews, J. Blum, J. Carpenter, C. Dominik, A. Isella, A. Natta, J. P.Williams, & D. J. Wilner, refereed review chapter accepted for publication in Protostars and PlanetsVI, University of Arizona Press (2014), eds. H. Beuther, R. Klessen, C. Dullemond, Th. Henning.

25. P. Pinilla, M. Benisty, T. Birnstiel, L. Ricci, A. Natta, C. P. Dullemond, A. Isella, T. Henning, & L. TestiMillimetre spectral indices of transition disks and their relation to the cavity radius, A&A 564, 51, 2014.

24. J. Menu, R. van Boekel, Th. Henning, C. J. Chandler, H. Linz, M. Benisty, S. Lacour, M. Min, C.Waelkens, S. M. Andrews, N. Calvet, J. M. Carpenter, S. A. Corder, A. T. Deller, J. S. Greaves, R. J.Harris, A. Isella, W. Kwon, J. Lazio, F. Menard, L. G. Mundy, L. M. Perez, L. Ricci, et al. TWHya:multi-wavelength interferometry of a transition disk, A&A 564, 93, 2014.

23. R. K. Mann, J. Di Francesco, D. Johnstone, S. M. Andrews, J. P. Williams, J. Bally, L. Ricci, M. Hughes,& B. Matthews ALMA observations of the Orion Proplyds, ApJ 784, 82, 2014.

22. A. Isella, L. Perez, J. Carpenter, L. Ricci, S. Andrews, & K. Rosenfeld An azimuthal asymmetry in theLkHα 330 disk, ApJ 775, 30, 2013.

21. C. Manara, G. Beccari, N. Da Rio, G. De Marchi, A. Natta, L. Ricci, M. Robberto, & L. Testi Accuratedetermination of accretion and photospheric parameters in Young Stellar Objects: the case of two candidate olddisks in the Orion Nebula Cluster, A&A 558, 114, 2013.

Luca Ricci 6

20. L. Ricci, A. Isella, J. M. Carpenter, & L. Testi, CARMA Interferometric Observations of 2MASS J044427+2512:The First Spatially Resolved Observations of Thermal Emission of a Brown Dwarf Disk, ApJ Letters 764, 27,2013.

19. F. Trotta, L. Testi, A. Natta, A. Isella, & L. Ricci, Constraints on the radial distribution of the dust propertiesin the CQ Tau protoplanetary disk, A&A in press, 2013.

18. P. Pinilla, T. Birnstiel, M. Benisty, L. Ricci, A. Natta, C. P. Dullemond, C. Dominik, & L. Testi, Dustevolution in Brown Dwarf disks, A&A 554, 95, 2013.

17. Spezzi, L., Cox, N. L. J., Prusti, T., Merin, B., Ribas, A., Alves de Oliveira, C., Winston, E., Kospal, A.,Royer, P., Vavrek, R., Andre, Ph., Pilbratt, G. L., Testi, L., Bressert, E., Ricci, L., Menshchikov, A., &Konyves, V. The Herschel Gould Belt Survey in Chamaeleon II. Properties of cold dust in disks around youngstellar objects, A&A 555, 71, 2013.

16. M. Robberto, D. R. Soderblom, E. Bergeron, V. Kozhurina-Platais, R. B. Makidon, P. R. McCullough,M. McMaster, N. Panagia, I. N. Reid, Z. Levay, L. Frattare, N. Da Rio, M. Andersen, C. R. O’Dell, K.G. Stassun, M. Simon, E. D. Feigelson, J. R. Stauffer, M. Meyer, M. Reggiani, J. Krist, C. F. Manara,M. Romaniello, L. A. Hillenbrand, L. Ricci, F. Palla, J. R. Najita, T. T. Ananna, G. Scandariato, & K.Smith, The Hubble Space Telescope Treasury Program on the Orion Nebula Cluster, ApJS 207, 10, 2013.

15. L. Ricci, L. Testi, A. Natta, A. Scholz, & I. de Gregorio-Monsalvo, ALMA Observations of ρ-Oph 102:Grain Growth and Molecular Gas in the Disk around a Young Brown Dwarf, ApJ Letters 761, 20, 2012.

14. L. Perez, J. M. Carpenter, C. J. Chandler, A. Isella, S. M. Andrews, L. Ricci, et al., Constraints on theRadial Variation of Grain Growth in the AS 209 Circumstellar Disk, ApJ Letters 760, 17, 2012.

13. A. Miotello, M. Robberto, M. Potenza, & L. Ricci, Evidence of Photoevaporation and Spatial Variation ofGrain Sizes in the Orion 114-426 Protoplanetary Disk, ApJ 757, 78, 2012.

12. L. Ricci, L. Testi, S. T. Maddison, & D. J. Wilner, Fomalhaut debris disk emission at 7 millimeters: con-straints on the collisional models of planetesimals, A&A 539, 6, 2012.

11. P. Pinilla, T. Birnstiel, L. Ricci, C. P. Dullemond, A. L. Uribe, L. Testi, & A. Natta, Trapping dustparticles in the outer regions of protoplanetary disks, A&A 538, 114, 2012.

10. L. Ricci, L. Testi, F. Trotta, A. Natta, A. Isella, & D. J. Wilner, The effect of local optically thick regions inthe long-wave emission of young circumstellar disks, A&A 540, 6, 2012.

9. M. Robberto, L. Spina, D. Apai, I. Pascucci, N. Da Rio, L. Ricci, C. Goddi, L. Testi, F. Palla, & F.Bacciotti, An HST Imaging Survey of Low-Mass Stars in the Chamaeleon I Star Forming region, AJ 144, 83,2012.

8. L. Ricci, L. Testi, J. Williams, R. K. Mann, & T. Birnstiel, The mm-colors of a young binary disk system inthe Orion Nebula Cluster, ApJ Letters 739, 8, 2011.

7. M. Reggiani, M. Robberto, D. R. Soderblom, M. R. Meyer, N. Da Rio, & L. Ricci, On age in the OrionNebula Cluster, A&A 534, 83, 2011.

6. L. Ricci, R. K. Mann, L. Testi, J. P. Williams, A. Isella, M. Robberto, A. Natta, & K. J. Brooks, The(sub-)millimeter SED of protoplanetary disks in the outskirts of the Orion Nebula Cluster, A&A 525, 81,2011.

5. L. Ricci, L. Testi, A. Natta, & K. J. Brooks, Dust grain growth in rho-Ophiuchi protoplanetary disks, A&A521, 66, 2010.

Luca Ricci 7

4. T. Birnstiel, L. Ricci, F. Trotta, C. P. Dullemond, A. Natta, L. Testi, C. Dominik, T. Henning, C. W.Ormel, & A. Zsom, Testing the theory of grain growth and fragmentation by millimeter observations ofprotoplanetary disks, A&A Letters 516, 14, 2010.

3. L. Ricci, L. Testi, A. Natta, R. Neri, S. Cabrit, & G. J. Herczeg, Dust properties of protoplanetary disks inthe Taurus-Auriga star forming region from millimeter wavelengths, A&A 512, 15, 2010.

2. M. Robberto, L. Ricci, N. Da Rio, & D. R. Soderblom, Evidence for a photoevaporated circumbinary diskin Orion, ApJ Letters 687, 83, 2008.

1. L. Ricci, M. Robberto, & D. R. Soderblom, The Hubble Space Telescope/Advanced Camera for SurveysAtlas of protoplanetary disks in the Great Orion Nebula, AJ 136, 2136, 2008.