We have investigated the flow pattern that arises past (proto)planets embedded in the nebula disk during its formation. We consider the regime where the planet mass is large enough to gravitationally perturb the gas (≳0.01 Earth masses), but not too large to open a gap or accrete unlimited amounts of gas from the disk. We consider both inviscid and viscid flows and aim to understand the flow pattern on the scales of the Bondi radius. Having described the flow pattern of the gas, we integrate trajectories of small, solid particles. In agreement with previous findings, we show that the ensuing accretion rates can be high—although, due to radial drift motions, pebble accretion is not necessarily an efficient mechanism.

Herbig Ae/Be objects, like their lower mass counterparts T Tauri stars, are seen to form a stable circumstellar disk which is initially gas-rich and could ultimately form a planetary system. We present Herschel SPIRE 460–1540 GHz spectra of five targets out of a sample of 13 young disk sources, showing line detections mainly due to warm CO gas.

In current theory of planet formation, streaming instability is one of the most promising mechanisms to overcome the meter-barrier in the course of core accretion. Almost all previous works, however, were focused on a local region of protoplanetary disks with a limited size of about 0.2 gas scale heights. Only one radial filamentary particle concentration was seen in these studies. To address this, we conduct the largest-scale simulations of this kind to date, up to 0.8 gas scale heights both horizontally and vertically. We demonstrate that streaming instability remains robust on large scale and multiple radial particle concentrations exist in large enough boxes. This result may be important in characterising the feeding zone of planetesimal formation.

I attempt to summarize our knowledge of planet formation in evolving protoplanetary discs. I first review the physics of disc evolution and dispersal. For most of the disc lifetime evolution is driven by accretion and photoevaporation, and I discuss how the interplay between these processes shapes protoplanetary discs. I also discuss the observations that we use to test these models, and the major uncertainties that remain. I will then move on to consider planet formation and migration in evolving discs, and discuss how observations of both discs and planets can be used to inform our understanding of protoplanetary disc evolution.

Recent high-resolution observations show that protoplanetary disks have various kinds of structural properties or inhomogeneities. These are the consequence of a mixture of a number of physical and chemical processes taking place in the disks. Here, we discuss the results of our comprehensive investigations on how disk inhomogeneities affect planetary migration. We demonstrate that disk inhomogeneities give rise to planet traps - specific sites in protoplanetary disks at which rapid type I migration is halted. We show that up to three types of traps (heat transitions, ice lines and dead zones) can exist in a single disk, and that they move differently as the disk accretion rate decreases with time. We also demonstrate that the position of planet traps strongly depends on stellar masses and disk accretion rates. This indicates that host stars establish preferred (initial) scales of their planetary systems. Finally, we discuss the possible observational signatures of disk inhomogeneities.

This contribution summarises the first characterisation of the 12 μm warm dust (“exo-Zodi”) luminosity function around Sun-like stars, focussing on the dustiest systems that can be identified by the WISE mission (Kennedy & Wyatt 2013). We use the sample of main-sequence stars observed by Hipparcos within 150pc as an unbiased sample, and report the detection of six new warm dust candidates. The ages of five of these new sources are unknown, meaning that they may be sites of terrestrial planet formation or rare analogues of other old warm dust systems. We show that the dustiest old (> Gyr) systems such as BD+20 307 are 1 in 10,000 occurrences. Bright warm dust is much more common around young (<120 Myr) systems, with a ~1% occurrence rate. We show that a two component in situ model where all stars have initially massive warm disks and in which warm debris is also generated at some random time along the stars' main-sequence lifetime, perhaps due to a collision, can explain the observations. However, if all stars only have initially massive warm disks these would not be visible at Gyr ages, and random collisions on the main-sequence are too infrequent to explain the high disk occurrence rate for young stars. That is, neither component can explain the observations on their own. Despite these conclusions, we cannot rule out an alternative dynamical model in which comets are scattered in from outer regions because the distribution of systems with the appropriate dynamics is unknown. Our in situ model predicts that the fraction of stars with exo-Zodi bright enough to cause problems for future exo-Earth imaging attempts is at least roughly 10%, and is higher for populations of stars younger than a few Gyr. This prediction of roughly 10% also applies to old stars because bright systems like BD+20 307 imply a population of fainter systems that were once bright, but are now decaying through fainter levels. Our prediction should be strongly tested by the Large Binocular Telescope Interferometer, which will provide valuable constraints and input for more detailed evolution models. A detection fraction lower than our prediction could indicate that the hot dust in systems like BD+20 307 has a cometary origin due to the quirks of the planetary dynamics. Population models of comet delivery need to be developed to help distinguish between different possible origins of warm dust.

As part of a deep multi-year non-redundant aperture mask infrared imaging campaign observing transition disks, we present multi-epoch monitoring of the resolved emission seen within the disk gap of LkCa 15. Orbital motion of both the central source and extended lobes as presented in Kraus and Ireland (2012) is clearly detected at the level of ~4 degrees/year (deprojected), in both K and L'-bands. Based on these data as well as single-epoch H and M bands epochs, we present two models for the central source - thermal emission as a planetary accretion signature and scattering. The thermal emission model is preferred.

High contrast imaging observations with the Hubble Space Telescope show that the nearby star Fomalhaut is surrounded by a dusty debris belt and a candidate planet, Fomalhaut b, located just inside the edge of the belt. Fomalhaut b has unexpected characteristics, such as a relatively blue spectrum, leading to the hypothesis that the detected object is a low-mass planet hosting a giant planetary dust ring or cloud seen in reflected light. Here we present new HST/STIS observations made in 2010 and 2012 that authenticate the existence of Fomalhaut b. Our MCMC analysis of four epochs of astrometry spread over eight years indicate that the orbit has a~170 AU and e~0.85. Fomalhaut b's orbit is apsidally aligned with the main belt, and periapse is located approximately ~30 AU south of the star. We also show the existence of a ~50 AU wide azimuthal dust depletion in the dust belt. These new findings provide a revised picture of Fomalhaut as a dynamically complex system, where the orbit of Fomalhaut b and the belt structure signify the presence of additional massive planets orbiting the star.

We report the detection of multi-armed spirals in the environment of HD 100546 using NICI at Gemini South in the Ks band. These data feature a better angular resolution and higher contrast than previous HST images, which allows to resolve the former known spiral into a multiple pattern. An analytic model with a gravitational perturber is used to fit the spiral pattern. We derived limit of detections which set constraints on the discovered forming planet.

We focused on analysing the role played by protoplanetary disks in the evolution of angular momentum during star formation. If all the angular momentum contained within collapsing pre-stellar cores was conserved during their formation, proto-stars would reach rotation rates exceeding their break-up velocities before they reached the main sequence (Bodenheimer 1995). In order to avoid this occuring, methods by which proto-stars can lose angular momentum must exist. Angular momentum can be transferred from star to disk via stellar magnetic field lines through a process called magnetic braking (Camenzind 1990; Königl 1991). Alternatively, the stellar angular momentum can be lost from the star-disk system entirely via stellar- or disk-winds (e.g. Pelletier & Pudritz 1992; Matt & Pudritz 2005).

The proportion of lost stellar angular momentum retained within the protoplanetary disk is important to studies of planetary system formation. If the bulk motion within the disk remains Keplerian, any increase of angular momentum in the disk causes an outward migration of disk material and an expansion of the disk. Therefore, an increase in disk angular momentum may cause a reduction in the disk surface density, often used to indicate the disk's ability to form planets.

We made use of multi-wavelength data available in the literature to directly calculate the stellar and disk angular momenta for two nearby regions of star formation. Namely, these were the densely populated and highly irradiated Orion Nebula Cluster (ONC) and the comparitively sparse Taurus-Auriga region. Due to the limited size of the ONC dataset, we produced an average surface density profile for the region. We modelled the stars as solid body rotators due to their fully convective nature (Krishnamurthi et al. 1997) and assumed the disks are flat and undergo Keplerian rotation about the same rotation axis as the star.

We observed the older disks within each of the two star forming regions to be preferentially larger and less massive, consistent with viscous accretion theories and disk dispersal. However, when drawing comparisons between the two regions, the ONC sample appeared to have less massive disks than the Taurus-Auriga sample, even though the population of Taurus-Auriga is older. This may suggest an influence of the birth cloud environment on protoplanetary disk evolution.

Finally, the older stars within the ONC were observed to harbour disks that contained more angular momentum than their younger counterparts whereas, in the Taurus-Auriga sample, the amount of angular momentum contained in the older and younger samples was consistent. We suggest that the missing disk angular momentum in the older Taurus-Auriga disks may be contained within yet-undetected planets.

We present some highlights of two ongoing investigations that deal with the dynamics of planetary systems. Firstly, until recently, observed eccentric patterns in debris disks were found in young systems. However recent observations of Gyr-old eccentric debris disks leads to question the survival timescale of this type of asymmetry. One such disk was recently observed in the far-IR by the Herschel Space Observatory around ζ2 Reticuli. Secondly, as a binary companion orbits a circumprimary disk, it creates regions where planet formation is strongly handicapped. However, some planets were detected in this zone in tight binary systems (γ Cep, HD 196885). We aim to determine whether a binary companion can affect migration such that planets are brought in these regions and focus in particular on the planetesimal-driven migration mechanism.

The presence of a cavity in a protoplanetary disk revealed by dust continuum emissions is sometimes postulated as a signpost of an embedded gas giant planet. More peculiarly, dust emissions exterior to the cavity are often observed to be asymmetric. We explore the possibility of the asymmetry as a result of the asymmetric distribution of dust in an eccentric protoplanetary disk under the secular gravitational perturbation of an embedded massive gas giant planet. We find that the surface density of the dust well coupled to the disk gas is enhanced around the apocenter of the disk. In addition, the azimuthal distributions of particles of various sizes can deviate significantly due to different coupling to the gas. Overall, the asymmetric structure exhibits a phase correlation between the gas velocity field and dust density distribution. A Doppler map for an eccentric disk is also presented based on Cycle 1 ALMA observations. Our study potentially provides a reality check as to whether an asymmetric disk gap detected at sub-mm and cm wavelengths is a signpost of a massive gas giant planet.

We study the photometric variability of a pre-main sequence star (K6, 0.9M⊙) CHXR 20. We test several scenarios for the variability including variable accretion, variable extinction, cool and hot spots on the stellar surface and the presence of a potential companion.

Gap formation by giant planets in self-gravitating disks may lead to a gravitational edge instability (GEI). We demonstrate this GEI with global 3D and 2D self-gravitating disk-planet simulations using the ZEUS, PLUTO and FARGO hydrodynamic codes. High resolution 2D simulations show that an unstable outer gap edge can lead to outward migration. Our results have important implications for theories of giant planet formation in massive disks.

We present preliminary results of a detailed study of the accretion, stellar, and wind properties of transitional disks (TDs) carried out with the X-Shooter spectrograph. Combining new and archival spectra, we collected a sample of more than 20 TDs from different nearby star-forming regions. Our sample includes objects with both small (<5-15 AU) and large (>20–30 AU) known inner hole size from the literature (either from mm-observations or IR SED fitting). We check their stellar parameters (Teff, L*, AV, M*) and derive their accretion properties (Lacc, Ṁacc) in a self-consistent way, which makes use of the wide wavelength coverage of X-Shooter, and study their wind properties by mean of different forbidden emission lines analysis.

The discovery of a likely companion of the Herbig Ae/Be star HD 142527 motivates the study of the effect that it produces on the SED. The main change on the system configuration is the formation of a gap in the disk in which the companion is embedded, following the orbit of the secondary star. This results in the formation of a wall (at the outer gap edge), which is illuminated by stellar radiation. We present a model for the SED, taking into account all the components of the system: the two stars, the disk with two gaps (one produced by the stellar companion and the other by potential planets), three walls (two associated with the gaps and the other with dust sublimation), optically thin material in the gaps and in a halo. The size of the modeled spherical halo is smaller than found in a previous study.

With the combination of Herschel PACS (far-IR), submillimeter (submm) and millimeter (mm) ground-based observations, we are leading an investigation of all members with spectral types M4 and onwards in the Taurus star-forming region. This complete census spans the stellar to substellar boundary (M6.25), and the wavelength range covers the transition from optically thick to optically thin emission. From our Hershel PACS observations of ~135 sources, we obtain a detection rate of ~40% at 70 μm and a detection rate of ~20% at 160 μm, and provide the first far-IR measurements for the majority of these members. With our complementary submm and mm observations, best fit SED models from the radiative transfer code MCFOST will be used to infer disk properties such as scale height, mass, outer radius and maximum dust grain size. These comprehensive population statistics of disks are critical for testing star/brown dwarf and planet formation models around these later type members of Taurus.

Understanding how a disk surrounding a young star evolves and disperses is crucial in order to understand the subsequent planet formation. In this proceeding, we summarize the results reported by Rigliaco et al. (2013) on the origin of the [OI] low-velocity component as a possible disk dispersal indicator.

Chondrite meteorites are the building blocks of the solar nebula, out of which our Solar System formed. They are a mixture of silicate and oxide objects (chondrules and refractory inclusions) that experienced very high temperatures, set in a matrix that remained cold. Their prevalence suggests that they formed through a very general process, closely related to stellar and planet formation. However the nature and properties of the responsible mechanism have remained unclear. The evidence for a hot solar nebula provided by this material seems at odds with astrophysical observations of forming stars. These indicate that the typical temperatures of protostellar disks are too low to melt and vapourise silicate minerals at the radial distances sampled by chondrule-bearing meteorites. Here, we show that processing of precursors in a protostellar outflow at radial distances of about 1 – 3 AU can heat them to their melting points and explain their basic properties, while retaining association with the colder matrix.

We present preliminary astrometric results aimed at understanding the lifetime of circumstellar disks and potential for planet formation. We have obtained parallaxes to stars in the TW Hydrae, Upper Scorpius, and Chamaeleon I stellar associations. These enable new estimates for the ages of the stars. We are also performing the Carnegie Astrometric Planet Search of nearby low mass stars for gas giant planets on wide orbits. We have our first candidate around a mature brown dwarf.