Coffee and tea will be available in the Forum Street from 08:30.

Information and updates on the meeting programme and social events.

In this talk I review recent progress in theoretical studies of formation and evolution of stars and disks in collapsing molecular cloud cores. I start from classical problems in the early phase of star and disk formation (i.e. until early Class 1 phase), such as the angular momentum problem, the magnetic flux problem, the magnetic braking catastrophe, the fragmentation crisis, driving of outflows, and so on. In particular, while the angular momentum problem and the magnetic braking catastrophe are now reconciled qualitatively, but they still remain as qualitative problems. Then I move to the later phase of star formation and discuss outstanding topics such as the luminosity problem, episodic accretion, and regulation mechanisms of star formation efficiency in the small scale in different mass regimes, among other things. Also, if time permits, I briefly review recent efforts on theoretical modeling and synthetic observations that enable us to directly compare theories and observations especially using ALMA. At the end I would like to summarize the remaining (and new) problems, (near) future directions, and (quite personal) perspectives.

While the physical processes regulating the formation and evolution of star-forming cores are believed to largely determine the properties of the resulting young stars, their study has been mostly limited to shallow- and low-resolution observations. The advent of Herschel and large (sub-)millimeter interferometers (ALMA, NOEMA) recently allowed to over-come these limitations, and carry out detailed and/or statistical studies of the cores physical structure and chemical composition, to finally unravel the complex interplay of processes at work to form stars from these cores. I will review recent observational results, showing how the combination of high angular resolution and unprecedented sensitivity allow to finely characterize critical properties such as the angular momentum content, infall rates, pristine disk properties and multiplicity fraction of the youngest star-forming cores.

One of the main scientific goals of the Herschel Gould Belt survey (http://gouldbelt-herschel.cea.fr) is to elucidate the physical mechanisms responsible for the formation and evolution of prestellar cores in molecular clouds. Based on Herschel/SPIRE-PACS photometric data, we have recently identified a large sample of such cores in the Aquila (Könyves et al. 2015) and Orion B (Könyves et al., in prep.) molecular clouds.

Our Herschel observations also provide an unprecedented census of filaments in the nearby clouds and suggest an intimate connection between these filaments and the formation process of prestellar cores. We will compare and contrast some properties of the dense cores in the Aquila and Orion B complexes, such as their distributions in the filamentary background, masses, lifetimes, and formation thresholds.

In summary, our Herschel findings support a filamentary paradigm for the early stages of star formation, where the cores result primarily from the gravitational fragmentation of marginally supercritical filaments (cf. André et al. 2014, PPVI).

The Herschel Space Observatory has provided extensive datasets of unprecedented quality and coverage. The Archive covers regions in a wide range of physical and star-forming conditions across the Galaxy. Here we introduce the latests results from an ongoing large-scale project focused on investigating the processes driving star formation in the most extreme conditions. Compact sources and filamentary structures have been identified and extracted from Herschel maps targeting the most active and densest regions of the Galactic Plane, comprising vigorous, high-mass star and cluster formation. Each structure was characterised according to its physical and environmental properties, ongoing star formation and evolutionary state. The star-forming conditions of these fields have been compared with those derived from the most diffuse, high-galactic latitude fields with none or weak star forming events. Our extensive study provides new evidence in favour of the critical role of external and environmental factors in the overall star formation process, and how these factors contribute to explaining the radically different star formation events in our Galaxy, from isolated low-mass star formation to massive clusters. This evidence will be summarised and discussed in context with theoretical models of cloud evolution.

Magnetic fields are considered one of the key physical agents that regulate star formation, but their actual role in the formation and evolution of dense cores remains an open question. Polarized dust continuum emission is particularly well-suited to probe the magnetic field structure in the dense, cold interstellar medium. Such observations also provide tight constraints on the efficiency of dust alignment along magnetic field lines, which are needed to properly infer the magnetic field properties from observations. With the Planck all-sky survey of dust submillimetre emission in intensity and polarization, we can investigate intermediate spatial scales in the hierarchy of star formation, between global molecular cloud measurements and studies of individual prestellar cores. Planck further enables a statistical analysis of the polarization properties of clumps. We have recently built the first all-sky catalogue of Galactic Cold Clumps (PGCC, Planck collaboration XXVIII 2015), a fraction of which we have studied in detail with our Herschel Key Programme ‘Galactic Cold Cores’. The sources cover a broad range in physical properties and correspond to different evolutionary stages in the star formation process, from quiescent starless clumps and nearby cores to young protostellar objects. I will present new results from our analysis of the polarized 353GHz Planck data for the PGCC sources. In particular, we have studied the variation of the polarization fraction and angle, and the relative orientation between the B-field and the clump elongations. We have also analysed the magnetic field morphology and compared it to structures (filaments, striations) traced at higher resolution with Herschel in the environment of PGCC sources, searching for evolutionary signatures. Finally, I will present a comparison of our results with predictions from MHD simulations that include radiative transfer and the dust radiative torque alignment mechanism.

Radiative heating by recently-formed (or forming) stars potentially provides a regulatory mechanism for star formation, reducing fragmentation and increasing protostellar masses. I will report on work carried out by the JCMT Gould Belt survey team on the contribution that SCUBA-2 data makes to measuring dust temperatures, on its own and in combination with Herschel measurements.

Planck observations have found relatively uniform values for the dust emissivity index of beta ~ 1.8 for diffuse cloud material. Nevertheless, stars form within smaller-scale, denser environments where the dust grains are expected to grow in size, form icy mantles, and subsequently have distinct dust emissivities compared to the diffuse cloud. To explore this expected dust grain evolution, we combined Herschel observations with long-wavelength 2 mm data across a ~ 2 pc long, continuous section of OMC 2/3 at 15000 AU (0.08 pc) resolution. We determine beta and reconstruct simultaneously the filtered-out large-scale emission at 2 mm in this analysis. We find that beta ~ 1.7-1.8 provides the best fit across most of OMC 2/3 with only one protostellar core showing significantly lower values of beta (~1.4). The consistency in beta between the cloud-scale Planck data and our core-scale analysis for OMC 2/3 supports the common assumption of fixed beta indices used ubiquitously in the conversion of (sub)millimeter emission to mass in dense star forming regions. If this consistency is demonstrated in other clouds, then significant changes to dust grain properties may only be apparent on smaller (sub core) scales.

Aligned dust grains within a magnetic field can induce polarization of thermal infrared radiation via emission, absorption or both. The position angle of polarization is directly related to the magnetic field projected on to the plane-of-the-sky. We will present new sub-arcsecond polarimetric imaging observations of embedded Young Stellar Objects made with the CanariCam mid-IR camera/spectrometer on the 10.4 m Gran Telescopio Canarias. By obtaining images across the 10 micron silicate band we can separate emissive and absorptive components of polarization and thus obtain two magnetic field directions, i.e. those within ‘warm’ and ‘cold’ regions of the target. For sources which are also extended we can then obtain a 3-d picture of the magnetic field.

Discs and outflows are observational features of star formation. While discs and outflows formation is becoming increasingly constrained thanks to radiation magnetohydrodynamics models and observations in the context of low-mass star formation, it is not the case for massive star formation. I will present results of massive magnetized dense core collapse simulations including radiative feedback and ambipolar diffusion. We use the adaptive-mesh-refinement code RAMSES (Teyssier 2002) which includes resistive MHD (Fromang et al. 2006, Masson et al. 2012) and radiative transfer (Commerçon et al. 2011, 2014). I will show how magnetic fields and radiative feedback work together to launch outflows. I will study the formation and properties (early evolution and fragmentation) of the disc around the massive protostars, comforting the standard accretion-discs scenario in the context of magnetised core collapse. Last I will also highlight the limits of ideal MHD with respect to magnetic flux redistribution and outflow formation.

Keplerian disks around young stars play essential roles in star and planet formation. Even though disks around T Tauri stars have been studied well in the last two decades, the disk formation process prior to T Tauri phase is still not well understood. This is because observations of disks around embedded protostars have been limited. Such a situation, however, has been undergoing a dramatic transformation in the ALMA are.

To understand the disk formation around protostars in detail, we have been observationally studying 8 protostars (6 Class 0 and 2 Class I) with ALMA in mainly C18O (J=2-1) line and 1.3 mm continuum emissions at sub-arcsec resolutions. All the sources show velocity gradients in C18O and detailed analyses using PV diagrams revealed that 4 of them show Keplerian rotation, which is clearly distinguished from rotation of the envelopes. Class 0 protostars tend to have less detectable disks, with lower specific angular momenta. It would be, therefore, suggested that our series of ALMA observations witness disk formation and growth during the protostellar evolution although the results are not statistically significant yet. Dynamical stellar masses estimated from the identified Keplerian rotation are compared with infall motions in their envelopes, finding that some of the infall velocities are significantly slower than the free-fall velocities yielded by their dynamical stellar masses.

The continuum visibility of L1527 IRS, which has an edge-on disk, is fitted by modified disk models without any annulus averaging. This analysis is particularly important for non-axisymmetric structures, such as a disk. The best model suggests that the density of dust is discontinuously enhanced at the boundary between the disk and the envelope. Additionally, the scale height of the disk can be explained by hydrostatic equilibrium. These results clearly demonstrate that ALMA observations can not only search for but also characterize in detail disks around protostars.

Expanding on Lewis, et al (2015) and (2016, submitted), which considered only an ideal MHD simulations of the collapse of molecular cloud cores without turbulence, we now use radiation magnetohydrodynamical calculations to explore how the physics of turbulence, magnetism and radiation influence the formation of protostars. We find that the gravitational collapse proceeds in a very different manner in cores with transonic turbulence compared to those with subsonic turbulence across a variety of field geometries and structures. Transonic (i.e. ~ Mach 1) cores are highly disrupted by the turbulent motion which also suppresses the formation of bipolar jets from the first hydrostatic core. Cores with subsonic turbulence still contain a jet, albeit without the symmetry previously seen in non-turbulent calculations and, depending on the magnetic field strength, form pseudo-discs. The inclusion of radiative transfer into the calculations promotes the formation of large discs, compared to the very small and dense discs produced by the MHD only calculations.

Stars form within large turbulent molecular clouds from density fluctuations which become gravitationally unstable. Numerical simulations of star formation are becoming ever more sophisticated, incorporating new physical processes in increasingly realistic setups. These models are being compared to the latest observations through state-of-the-art synthetic renderings that can identify the different chemical species present in the protostellar systems. The chemical evolution of the interstellar and protostellar matter is a very active field of research, with more and more chemical databases and reaction solvers becoming available online to the community.

We investigate the effect of the Hall current term on the formation of the circumstellar disk using three-dimensional simulations. In our simulations, all non-ideal effects, as well as the radiation transfer, are considered. We found that the size of the disk is significantly affected by a simple difference in the inherent properties of the prestellar core, namely whether the rotation vector and the magnetic field are parallel or anti-parallel. In the former case, only a very small disk (\lt 1 {AU}) is formed. On the other hand, in the latter case, a massive and large (\gt 20 {AU}) disk is formed in the early phase of protostar formation. Since the parallel and anti-parallel properties do not readily change, we expect that the parallel and anti-parallel properties are also important in the subsequent disk evolution and the difference between the two cases is maintained or enhanced. This result suggests that the disk size distribution of the Class 0 young stellar objects is bimodal. Thus, the disk evolution can be categorized into two cases and we may call the parallel and anti-parallel systems Ortho-disk and Para-disk, respectively. We also show that counter-rotating envelopes against the disk rotation appear with a size of ≳ 200 {AU}. We predict that the counter-rotating envelope will be found in the future observations.

Using an ensemble SPH simulations, we follow the evolution of prestellar cores as they collapse and fragment into protostars. The initial conditions for these simulations are constructed to match the observed properties of the cores in Ophiuchus. The protostars that form match the statistics of observed young protostars (IMF and multiplicity statistics, including triples, quadruples, quintuples and sextuples) but only if (i) radiative feedback from protostars is episodic, and (ii) the turbulent velocity field has a significant solenoidal component. A majority of protostars are attended by significant discs, but in multiple systems these discs are often poorly aligned with one another and/or the binary orbit, reflecting the stochastic nature of the accretion flows that feed material into the centre of a core. We also present synthetic spectra and images of multiple systems embedded in protostellar cores. These are calculated using a new Smoothed Particle Monte Carlo Radiative Transfer algorithm.

As the nearest gas-rich galaxies, the Large and Small Magellanic Clouds (LMC and SMC) offer the exciting opportunity to bridge the gap between star formation processes on large galaxy-wide scales and on the small scales of individual Young Stellar Objects (YSOs). These metal-deficient galaxies also provide an invaluable window into the star formation process at low metallicity, a region in the parameter space that remains relatively unexplored. I present the results of spectroscopic observations obtained with PACS and SPIRE/FTS onboard the Herschel Space Observatory. The sample of massive SMC and LMC YSOs is well characterised at near- and mid-IR wavelengths, and includes both deeply embedded sources and compact HII regions. The strengths of key gas-phase cooling species ([OI], [CII], H2O, CO, OH) are measured as probes of the physical conditions of the gas surrounding the YSOs. This analysis directly probes the potential metallicity effect, since it quantifies the relative luminosities of the species that promote envelope cooling and thus constrain the cooling budget of the YSO envelopes. The results indicate that while [OI], [CII] and CO are easily and widely detected, H2O and OH may be weak or absent in most YSOs. When compared with massive Galactic YSOs, the Magellanic YSOs clearly exhibit higher photoelectric efficiency (measured by the ratio of line emission to total IR flux), while showing similar [OI]/[CII] ratios; in terms of standard PDR models this suggests a lower G_0/n ratio. The CO ladder is used to constrain the density and temperature of the emitting gas. The spatial extension and morphology of the main emission lines is used to explore the interplay and feedback of the massive YSOs with their environments. I will place such results in context by comparing SMC, LMC and Galactic samples, in order to constrain potential metallicity effects on the star formation process.

How do the composition and kinematics of massive star forming environments affect the properties of the high-mass protostars that are forming in them? How is the degree of fragmentation and mass on disk-like scales related to the larger reservoir of dust and gas that they reside in? Are the 10^-4 Msol/yr and higher mass accretion rates and/or flattened envelope structures required by many current theories to form the most massive stars seen in real systems? Does feedback have more of an impact on large or small scales and what is the size (and shape) of the mass reservoir systems forming massive stars? These are all key questions to developing a full, comprehensive and prescriptive theory of how the most massive stars form. What is more, answering them requires multi-scale observations of both the continuum and molecular lines. I will present early results from the CORE NOEMA large program, which is designed to answer such questions by combining observations with multiple PdBI configurations and the IRAM 30m of 20 high-mass star forming regions with L> 10^4 Lsol. As such we have one of the largest datasets to date of high mass star forming regions with sensitivity to emission on spatial scales from ~0.4 pc to <1000 AU, ideal for tackling these fundamental questions.

There will be a BBQ for all delegates out on the terrace of Holland Hall. Your conference bag includes a token that you can exchange for a free drink from the cash bar.

Coffee and tea will be available in the Forum Street from 08:30.

09:00 Sam Geen (CEA Saclay): Feedback in Molecular Clouds

09:15 Jan Orkisz (IRAM/LERMA): Turbulence versus star formation efficiency in Orion B

09:30 Gwen Williams (University of Cardiff): What can filament dynamics tell us about core formation?

09:45 Joseph Booker (University of Toledo): HST Scattered Light Imaging of Orion Protostars: Do Outflows Halt Infall?

10:00 Bilal Ladjelate (CEA Saclay): Star-formation in the Ophiuchus Molecular Cloud: Similarities and diversity

10:15 Coffee break

10:45 Josefa Grossschedl (University of Vienna): Resolved maps of Star Formation Rate and Efficiency in Orion A

11:00 Steve Mairs (University of Victoria): How Do Protostars Assemble Mass? A Sub-Millimetre (JCMT) Variability Survey of Deeply Embedded Protostars

11:15 Dominika Boneberg (University of Cambridge): The midplane conditions of protoplanetary discs

11:30 Julia Roquette (Universidade Federal de Minas Gerais): Near-Infrared variability of disk-bearing stars in Cygnus OB2

A splinter session dedicated to the ages and timescales of young stars. Further information concerning this session, including topics to be discussed and details regarding the submission of contributions, can be found on the session webpage.

09:00 John Monnier: Introduction to Planet Formation Imager Project

09:15 Stefan Kraus: The Science Vision for PFI

09:40 Mike Ireland: A Baseline Design and Technical Roadmap for the PFI

10:05 Catherine Espaillat: Detecting and characterising protoplanets with PFI

10:50 Johan Olofsson: Late stages of planetary system formation investigated with PFI

11:25 Sebastian Hoenig: Extragalactic science with PFI

This session will be devoted to advances in numerical simulation of star formation and protostellar discs. There will be talks on both numerical methods as well as results of simulations.

09:00 Daniel Seifried (University of Cologne)
09:15 Munan Gong (Princeton University)
09:30 Rachel Spowage (Cardiff University)
09:45 Rajika Kuruwita (ANU)
10:00 Claire Esau (University of Sheffield)

10:00-10:30 Coffee

10:30 Duncan Forgan (University of St. Andrews)
10:50 Discussion ‘Where next for computation?’

Rationale: Star formation theories predict temperatures and densities for clouds, filaments and cores. Neither temperature nor density is a direct observable. This session aims to bring together researchers interested in extracting these physical properties from observations (e.g. continuum surveys or molecular lines) to discuss useful datasets and methodology (e.g. Bayesian model fitting, radiative transfer models).

9:00-10:30 short talks, each finishing with a summary slide showing the main result(s) and a ‘wish list’ - what the speaker would like to be able to do with his/her method/data/region but doesn’t know how to achieve. Questions at this point will be limited to clarifications.

09:00 Jenny Hatchell (University of Exeter): Introduction

09:10 Yao-Lun Yang (University of Texas): Modeling the Structure of a Class 0 Protostar, BHR71, with 3-D Dust Radiative Transfer Simulations

09:25 Fernando Olguin Choupay (University of Leeds): The physical properties of the prototypical MYSO GL 2591

09:40 Jared Keown (University of Victoria): The Green Bank Ammonia Survey

09:55 Jorge Abreu-Vicente (MPIA Heidelberg): Fourier-space combination of Planck and Herschel images

10:10 Nadia Murillo (Leiden University): The role of temperature and gas heating in multiple stellar system formation”

10:30 Coffee break

11:00-12:00 2-minute presentations of ’wish lists’ from relevant main session talks (Joe Mottram, Katherine Johnstone, Emily Drabek, Jan Forbrich, & Jenny Hatchell), followed by open discussion based on the issues raised.

Packed lunches can be collected from Holland Hall from 12:00. Please note that since they will no longer be refridgerated the sandwiches should be eaten within two hours of collection.

Please make sure you are wearing suitable clothing, including sturdy shoes for the Dartmoor and Jurassic Coast walks and a waterproof jacket if needed. The ground at Pebblebed Vineyard may also be wet and uneven.

Transport and associated arrangements have been made according to the number of delegates registered for the tours. We therefore ask you to please remain with your chosen event and not attempt to join another tour.

Coffee and tea will be available in the Forum Street from 08:30.

Information and updates on the programme and social events.

Over the last few decades our understanding of the properties of young stars and clusters has changed dramatically thanks to many wide-field observations and surveys across the electromagnetic spectrum. Infrared, X-ray and emission-line surveys have greatly increased our census of known pre-main-sequence stars, allowing us to study their distribution and clustering, measure the initial mass function and multiplicity in different environments, and study the ages and star formation histories of different regions. The rise in time domain surveys has also improved our view of episodic accretion and variability in pre-main-sequence stars, while high-resolution imaging has allowed us to study jets and outflows from such objects that exert feedback on their surroundings. In this talk I will review the current observational picture of the properties of young stars and clusters, with a particular focus on how wide-field surveys have contributed to our understanding of this critical phase of stellar lives.

Star formation is governed by the complex interplay of various physical forces, including turbulence, gravity and magnetic fields. In addition, neighboring stars greatly influence each other and their natal cloud by injecting energy into their surroundings (“feedback”). This interaction creates strong coupling between physical processes acting over a broad range of scales. Numerical simulations play an essential role in investigating the complex, nonlinear physics of star cluster formation. In this talk, I will summarize the current state-of-the-art in numerical simulations. I will discuss how numerical results have shaped our understanding of star formation and how different processes impact fundamental quantities like the stellar initial mass function, stellar multiplicity and star formation efficiency.

One of the largest uncertainties in star formation is the initial density and velocity structure of young (1 - 10 Myr) star-forming regions, clusters and associations. Quantifying the initial or maximum density of a region is crucial; a dense region will disrupt the orbits or destroy planetary systems and stellar binaries, and photoevaporate or truncate protoplanetary discs through interactions with massive and low-mass stars. However, the present-day density does not strongly constrain the initial density due to two-body relaxation, which causes a region to rapidly expand and lowers the density by several orders of magnitude within a few Myr. In this talk, I will show that a range of structural diagnostics can constrain both the initial density, and the initial virial ratio of a star-forming region. I will finish by demonstrating the further constraints that Gaia and associated ground-based surveys (e.g. GES) will place on this problem in the near future.

I will present new results for pre-Main sequence and early brown dwarf evolutionary models accounting for the effect of early accretion history. First, I will present self-consistent numerical simulations fully coupling numerical hydrodynamics models of collapsing prestellar cores and evolutionary models of the central protostar or proto-brown dwarf. I will in particular analyse the main impact of consistent accretion history on Li depletion and present a new result regarding the effect of accretion on Li depletion. I will also present the first attempt to describe the multi-dimensional structure of accreting young stars based on fully compressible time implicit multi-dimensional hydrodynamics simulations. I will discuss the relevance of assumptions and treatments of accretion used in 1D stellar evolution codes.

Pre-main sequence (PMS) stars are surrounded by disks throughout the first few Myr following their birth. The star-disk interaction is governed by the magnetospheric accretion process. In this talk, we present the results of an extensive u-band accretion survey of the 3 Myr-old open cluster NGC 2264. Performed at CFHT/MegaCam as a part of the CSI 2264 international campaign, the survey provided simultaneous UV+optical photometric monitoring over two full weeks for about 750 young cluster members (of which about 45% have disks). We use the diagnostics of the UV excess, measured over the reference flux level defined by non-accreting members, to investigate accretion properties over the stellar mass range 0.1-1.5 Mo, and infer evidence for a huge variety of accretion regimes within the cluster. While a definite correlation is observed between the average accretion rate M_acc and stellar mass, a significant spread in M_acc values is detected at any given stellar mass. Little contribution to this spread arises from M_acc variability, monitored here over week timescales. We explore and discuss the origin of this large intrinsic spread, which may be associated with a multiplicity of accretion mechanisms: unstable accretion regimes, characterized by short-lived, stochastic accretion bursts, are found to be dominant at the largest M_acc; conversely, stable, funnel-flow accretion regimes, with a steady behavior over many rotational cycles, are found at more moderate accretion rates. In addition, we find a connection between accretion properties and spatial distribution of cluster members: strong accretors are assembled close to the active star forming sites within the cloud, whereas milder accretors and disk-free objects distribute more evenly across the region, possibly as a result of dynamical evolution from their birth sites. This suggests that an intrinsic age/evolutionary spread across the cluster may also contribute to the observed spread in M_acc at any given mass.

In the last few years, large spectropolarimetric surveys have found low magnetic field detection rates in Herbig Ae/Be stars. It has also been recently noted that magnetic field structure and strength dramatically change with increasing stellar mass. These results are very suggestive that the mechanisms for accretion and outflow in Herbig Ae/Be star+disk systems may differ from the magnetospheric accretion paradigm as envisaged for T Tauri star+disk systems. We present the results of our high resolution optical spectroscopic campaign of ~60 Herbig AeBe stars. Our survey includes multi-epoch observations; the timescales sampled range from high cadence (~minutes) to observations taken over several years, probing a wide range of kinematic processes. We find that the strength of variability increases with the cadence of the observations, and over all timescales sampled, the strongest variability occurs within the blueshifted absorption components of the Balmer series lines. We see no inverse P-Cygni profiles, traditionally indicative of ongoing accretion. We discuss the implications of these results in context of recent spectropolarimetric surveys for our understanding of how accretion is occurring in these objects, as well as ongoing radiative transfer modeling.

The evolution of protoplanetary disks in young stellar clusters is regulated by the interplay of various physical processes, such as accretion and winds, and by the interactions with other stars in the cluster. Accretion and winds are best studied spectroscopically. Instruments like the VLT/X-Shooter spectrograph allow us to observe simultaneously the signatures of the accretion process, such as the UV-excess and the emission lines, together with lines tracing winds and outflows, such as helium lines and forbidden lines. At the same time, such spectra allow us to robustly derive the physical parameters of the central objects, such as their temperature and their mass. These processes relate to the disk mass and size, which can nowadays be studied with ALMA. Finally, the coming Gaia data releases will open the field to new studies of dynamical evolution of stars in young clusters by means of kinematical modelling. I will report on the stellar, accretion, and wind properties derived with X-Shooter of the complete samples of low-mass stars in the Lupus and Chamaeleon star forming regions, and discuss the dependence of stellar and accretion parameters with the disk properties obtained with ALMA surveys in these regions. I will also show how we can use Gaia data to study young clusters and the effect of interactions on the evolution of disks.

We present the recent discovery of a substantial population of optically hidden eruptive variable protostars in VISTA Variables in the Via Lactea survey (VVV). VVV was the first panoramic time domain survey of the Milky Way in the near infrared. It ran from 2010-2015, observing a 560 sq deg area of the Galactic bulge and plane between 50 and 70 times in the Ks filter. A wide variety of high amplitude infrared variables were detected (DeltaKs > 1 mag) but YSOs represent about half of the population. The YSOs have a variety of light curve types but a substantial proportion can be described as photometric outbursts. Most of these “eruptive” variables appear to be bona fide examples of episodic accretion, similar to the FUor and EXor phenomena. However, their outburst durations and spectroscopic properties are a mix of the FUor and EXor types; those established types are much rarer in the sample. We provisionally refer to these mixed sources as MNors, after the illuminating source of McNeil’s Nebula, V1647 Ori. Eruptive variability is at least an order of magnitude more common amongst class I YSOs than in class II YSOs: we will present a first estimate of the incidence in class I YSOs. Finally I describe the planned “VVVX” extension of VVV to the rest of the southern plane, which is currently at the second and final stage of the ESO public survey selection process.

I will present the results of four radiation hydrodynamical calculations of star cluster formation that span metallicities ranging from 1/100 to 3 times the solar value. The calculations treat both the thermodynamical evolution of the low-density interstellar medium (including hydrogen and carbon chemistry), and radiation transport which dominates temperatures near protostars. I will discuss the statistical properties of the stars and brown dwarfs that are produced, including how the mass function, multiplicity, and properties of multiple systems depend on the metallicity of the progenitor cloud.

Low mass stars from in a diverse range of environments, from isolated dark clouds to dense clusters in close proximity to massive stars. How the low mass star formation process differs between these environments is not well understood. We do know that within this range of environments, the densities of young low mass stars varies by orders of magnitude, yet the initial mass function remains relatively invariant. Comparative studies of protostars in these environments are needed to assess how variation in gas density, turbulence and kinetic temperature affect the fragmentation, collapse and accretion of gas and the formation of stars and disks. I will overivew a survey of protostars in the Orion A & B molecular clouds with the Spitzer, Herschel, Hubble and Apex telescopes, spanning 1.6 to 870 um, as well as follow-up observations in the near-IR and sub-millimeter. The goals of these observations are to characterize multiplicity, infall, accretion, outflow, and disk formation in the diverse environments found in the Orion clouds. These observations find a decrease in the spacing of protostars with increasing gas density, an increase of protostellar luminosity with increasing gas density, and an increase in the number of companions with increasing stellar density. I will discuss how these observations are leading to a better understanding of the physical factors, both external and internal, that control the rate and efficiency at which low mass stars form and ultimately determine their multiplicity and masses.

The sensitivity upgrades of both the NRAO Very Large Array (VLA) and the NRAO Very Long Baseline Array (VLBA) have begun to provide us with a much improved perspective on stellar centimeter radio emission, particularly concerning young stellar objects (YSOs) and ultracool dwarfs. I will mainly present a deep VLA and VLBA radio survey of the Orion Nebula Cluster (ONC), where we have found 556 compact radio sources, a sevenfold increase over previous studies, and intricate detail on the radio emission of proplyds. We can now better disentangle thermal and nonthermal radio emission by assessing spectral indices, polarization, variability, and brightness temperatures (VLBA). With simultaneous radio-X-ray time domain information (Chandra) and VLBA precision astrometry, this project is providing unpredented constraints on the magnetospheric activity of YSOs across a wide mass range, new insights into the impact of the massive Trapezium stars on their environment, and new astrometric constraints on the ONC itself. Additionally, I will present new VLBA results in ultracool dwarf astrometry. More generally, and beyond providing a new perspective on stellar cm radio emission and physics, this presentation will highlight how VLBI astrometry will allow us to extend the Gaia sample of YSOs and ultracool dwarfs by including embedded objects, distant obscured sources in the Galactic plane, and faint ultracool dwarfs, while providing important opportunities for astrometric cross-calibration with Gaia.

Multiplicity is common in field stars and protostars. While fragmentation is considered to be the mechanism of formation, the question of when and how this occurs is still open. Previous studies towards pre-main sequence binaries found pairs of non-coeval (different ages) components, with frequencies of 15 to 33%. Is this non-coevality present from the moment of formation or product of dynamical evolution? We address this question by determining the relative evolutionary stages of the components in young embedded multiple protostellar systems. Spectral energy distributions (SEDs) for known multiple protostellar systems in the Perseus star forming region are constructed from literature data and Herschel PACS photometric maps. Inclination effects and the surrounding envelope and outflows are considered in order to decouple source geometry from evolution. This together with the shape and properties derived from the SED are used to accurately determine each system’s coevality. Synthetic SEDs are used to study the frequency of apparent non-coevality due to geometry. Effects of unresolved multiple protostellar systems on SED shapes are also investigated. We find 33% of multiple protostellar systems in our sample to be non-coeval, with higher order multiples showing a tendency to be non-coeval. Random pairing of synthetic SEDs suggest an apparent non-coevality frequency of 17%, however our sample does not show signs of strong geometric effects, hence the observed non-coevality is real. The implications that the non-coevality frequency found in our work has on formation mechanisms and evolution are examined.

We present new spectroscopy and Hubble Space Telescope imaging of protostellar jets driven by intermediate-mass stars in the Carina Nebula. New, near-IR [Fe II] observations of these jets reveal dense gas that is self-shielded from Lyman continuum photons from nearby O-type stars, but is excited by non-ionizing FUV photons that penetrate the ionization front within the jet. Each jet contains a substantial mass of dense, neutral gas that is not seen in Halpha emission from these jets. In some cases, [Fe II] emission traces the jet inside its natal dust pillar, connecting the larger Halpha outflow to the embedded IR source that drives it. New proper motion measurements reveal tangential velocities similar to those typically measured in lower-luminosity sources (100-200 km/s). Combining high jet densities and fast outflow speeds leads to mass-loss rate estimates an order of magnitude higher than those derived from the Halpha emission measure alone. Higher jet mass-loss rates require higher accretion rates, implying that these jets are driven by intermediate-mass (~2-8 Msun) protostars. For some sources, mid-IR luminosities of the driving sources are clearly consistent with intermediate-mass protostars others remain deeply embedded and require long-wavelength, high-resolution images confirm their luminosity. These outflows are all highly collimated, with opening angles of only a few degrees. With this new view of collimated jets from intermediate-mass protostars, we argue that these jets reflect essentially the same outflow phenomenon seen in low-mass protostars, but that the collimated atomic jet core and the material it sweeps up is irradiated and rendered observable. Thus, the jets in Carina offer strong additional evidence that stars up to ~8 Msun form by the same accretion mechanisms as low-mass stars.

We are studying the recent low-mass star formation in the Tarantula Nebula using the Hubble Tarantula Treasury Project observations. Looking for stars with prominent Halpha excess emission (> 4 sigma, equivalent width > 10A), we have identified more than 20,000 pre-main sequence (PMS) stars over an area of ~180 x 180 pc^2. We are able to detect and study not only the youngest PMS objects, but also those approaching the main sequence, with ages older than ~10 Myr. This is so far the largest sample of individually resolved young low-mass stars.

We find that the distribution of PMS stars is considerably more diffuse than that of massive stars: while many young PMS stars are often close to massive objects, a similarly high number of both young and older PMS objects are clumped in regions with very few or no high-mass stars around. This implies that the conditions for the formation of low-mass stars are more lenient than those required by high-mass stars, and it might even suggest that the relevant processes are quite different. This could have important implications for the concept of initial mass function.

In the central regions, around the R136 cluster, we have already completed the analysis of the physical properties of both younger and older PMS stars. We confirm our previous findings on the dependence of the mass accretion rate on the mass and age of the stars. We show that, in similar conditions of mass and age, in the Tarantula Nebula the mass accretion rates are systematically higher than in the Milky Way, yet still lower than those we measured in active star forming regions in the Small Magellanic Cloud. These findings appear to indicate that the metallicity of the environment may play a significant role in the mass accretion process.

I will discuss numerical simulations which offer a simple, universal, and robust explanation of the star cluster (initial) mass function - gravitational focusing - with implications for the upper mass end of the stellar IMF.

The origin of the stellar initial mass function (IMF) is one of the most debated issues in astrophysics. Two major features of the IMF are 1) a fairly robust power-law slope at the high-mass end known since Salpeter (1955), and 2) a broad peak below 1 Mo corresponding to a characteristic stellar mass scale. In recent years, the dominant theoretical model proposed to account for these features has been the “gravo-turbulent fragmentation” picture, whereby the properties of interstellar turbulence lead to the Salpeter power law and gravity sets the characteristic mass scale (Jeans mass). I will discuss modifications to this picture based on Herschel observations of nearby molecular clouds. The Herschel results point to the key role of the quasi-universal filamentary structure pervading the cold interstellar medium and support a scenario in which star formation occurs in two main steps: First, large-scale compression of interstellar material in supersonic MHD flows generates a cobweb of ~ 0.1 pc-wide filaments in the ISM; second, the densest filaments fragment into prestellar cores above the line mass threshold for gravitational instability. In this observationally-driven scenario, the dense cores making up the peak of the prestellar core mass function (CMF) - likely responsible for the characteristic IMF mass scale - result from gravitational fragmentation of filaments near the critical mass per unit length. The power-law tail of the CMF/IMF arises from the characteristic power spectrum of initial density fluctuations measured along the Herschel filaments (Roy et al. 2015) and from the power-law distribution of masses per unit length observed for supercritical filaments.

The Conference Dinner will take place in the Great Hall, starting with a drinks reception at 19:00. There will then be a three course dinner and at 21:30 we will be entertained by the 13-piece Soul Traders band. A cash bar will be available.

Coffee and tea will be available in the Forum Street from 08:30.

Information and updates on the programme and social events.

We know that most stars were once surrounded by protoplanetary disks. How these young disks evolve into planetary systems is a fundamental question in astronomy and observations of young pre-main sequence stars may provide insights. In this talk, I will review the key constraints on theoretical models provided by observations of the dust and gas in protoplanetary disks. I will discuss disk demographics and evolution as well as disk structure, particularly those disks that contain holes or gaps which many researchers have posited are the footprints of planets. Recent MIR and sub-mm imaging work will be discussed as well as remaining questions in the field of protoplanetary disks.

In this talk I will review our understanding of protoplanetary discs. These discs are of considerable interest, as they are both the primary means of driving protostellar accretion, and also the sites of planet formation. I will briefly discuss disc formation and structure, and then look in detail at the various physical processes - angular momentum transport in the disc, and mass and angular momentum loss in winds - which drive disc evolution. This is a rapidly evolving field, so I will attempt to highlight key recent developments, as well as giving a critical assessment of where the field currently stands. I will conclude by discussing future directions for our study of disc evolution, and the key questions we wish to answer in the coming years.

We have undertaken time-series multi-colour photometry of the Orion Nebula Cluster over seven nights, with simultaneous multi-fibre spectroscopy. This allows us to construct “movies” of how the positions of stars in colour-magnitude space change with time, and use the spectroscopy to analyse the physical mechanisms driving those changes. Whilst many stars remain largely static in position, some classical T Tauri stars show remarkable peregrinations around the colour-magnitude space. Some changes are clearly due to changes in dust obscuration, though there is evidence for grain growth in the extincting material. The degree of variability is clearly correlated with position in colour-magnitude space with the more variable stars lying below the majority of the pre-main-sequence. As these are the classical T Tauri stars this leads to the remarkable conclusion that in a colour magnitude diagram the heavily accreting stars classical T Tauri stars appear to be older than the disc-less weak-lined T Tauri stars. The simultaneous spectroscopy allows us to show that this is purely an effect of the accretion luminosity.

We present radiation transfer models of rotating young stellar objects (YSOs) with hotspots in their atmospheres, inner disk warps and other 3-D effects in the nearby circumstellar environment. Our models are based on the geometry expected from the magneto-accretion theory, where material moving inward in the disk flows along magnetic field lines to the star and creates stellar hotspots upon impact. Due to rotation of the star and magnetosphere, the disk is variably illuminated. We compare our model light curves to data from the Spitzer YSOVAR project to determine if these processes can explain the variability observed at optical and mid-infrared wavelengths in young stars. We focus on those variables exhibiting dipper behavior that may be periodic, quasi-periodic, or aperiodic. We find that the stellar hotspot size and temperature affects the optical and near- infrared light curves, while the shape and vertical extent of the inner disk warp affects the mid-IR light curve variations. Clumpy disk distributions with non-uniform fractal density structure produce more stochastic light curves. We conclude that the magneto-accretion theory is consistent with certain aspects of the multi-wavelength photometric variability exhibited by low-mass YSOs. More detailed modeling of individual sources can be used to better determine the stellar hotspot and inner disk geometries of particular sources.

Protostar or protoplanetary disks are the link between the collapse of prestellar star-forming clumps at large scales, and the formation of planet embryos at small scales. Understanding the magnetic, thermal and stability properties of these disks, as well as the key problem of angular momentum transport during the core collapse, are thus mandatory to have a reliable description of protostellar/protoplanetary disks. In this talk, I will present calculations of disk formation that include the most complete relevant physics: non-ideal MHD, turbulence, non-equilibrium chemistry. The output of these calculations, disk properties and outflow signatures, will be compared with recent observations, allowing us to better understand the genesis and the nature of disks.

The timescales and relevant parameters for protoplanetary disk evolution are crucial to fully understand planet formation, but a consistent view of this phenomenon has remained elusive given its complexity and limited sample sizes. In this contribution, I will present the most complete study of disk evolution up to date, performed with a sample of more than 2300 YSOs in 22 nearby (<500 pc) star-forming regions and associations. The unprecedented size of the sample and homogeneous treatments applied allowed us not only to derive the most precise measurement of the characteristic disk lifetime so far but also to statistically confirm an important dependence of disk lifetimes with stellar mass. Such a dependence could even lead to differences in the architectures of planetary systems around low-mass and high-mass stars. Finally, I will describe our current efforts on expanding these results with a more detailed subsample and advanced SED modeling techniques.

The total gas mass of a protoplanetary disk is a fundamental, but poorly determined, quantity. A new technique (Bergin et al. 2013) has been demonstrated to assess directly the bulk molecular gas reservoir of molecular hydrogen using the HD J=1-0 line at 112 microns. In this work we present a small survey of T Tauri disk observations of the HD line. Line emission is detected in two cases at >3 sigma significance. Using detailed disk structure models, including the effect of UV gas heating, we determine the amount of gas required to fit the HD line and the amount of dust required to fit the observed disk spectral energy distributions. For both disks, the amount of gas required is more than the MMSN value, and the gas/dust ratio is at least a factor of two lower than that of the ISM. We discuss the implication of this result for these disks’ carbon chemistry and the disk mass probability distribution.

During their formation phase stars gain most of their mass in violent episodic accretion events, such as observed in FU Orionis stars. In this talk I will report on VLTI interferometric observations that allows us study the disk structure around these objects on sub-AU scales.

I will present our ALMA line and continuum observations at 1.2mm with ~0.3” resolution that uncover a Keplerian-like disc around the forming O-type star AFGL 4176. The first-moment maps, pixel-to-pixel line modelling, and position-velocity diagrams of the CH3CN J = 13–12 K-line emission all show a velocity gradient along the major axis of the source, coupled with an increase in velocity at small radii, consistent with Keplerian-like rotation. I will also present APEX 12CO observations that show a large-scale outflow from AFGL4176 perpendicular to the major axis of mm1, supporting the disc interpretation. Finally, we have conducted radiative transfer modelling of the ALMA data, showing that a Keplerian disc surrounding an O7 star, with a disc mass and radius of 12 Msun and 2000 AU reproduces the line and continuum data, further supporting our conclusion that our observations have uncovered a Keplerian-like disc around an O-type star. This work is published in Johnston et al. (2015).

Transition discs are protoplanetary discs that show evidence for dust trapping in their outer regions. Recent high angular resolution mm imaging of these discs has indicated that dust particles, as well being trapped radially, are also concentrated in non-axisymmetric features, and it has been suggested that the dust particles are trapped in a large scale vortex. Since the dust particles that naturally accumulate in transition disc dust traps have Stokes numbers close to unity, there is naturally a large reservoir of pebbles in transition disc dust traps. I will argue that the transition disc dust traps are prime sites for rapid pebble accretion onto low-mass planetary embryos. At the planetary accretion rates expected in nominal transition discs, the accretion luminosity is sufficiently high to heat the surrounding disc to radii well outside the planet’s Hill sphere. This makes the disc locally baroclinic and can lead to vortex formation. I will present this new scenario for vortex formation in transition discs and discuss the long term consequences, while arguing it is perhaps more natural than those scenarios discussed so far.

Transitional and so-called pre-transitional disks consist of an optically thin inner disk and an optically thick outer disk. In some disks, there is evidence for much more complex disk evolution than simply a cleared inner hole. For example, in the case of Oph IRS 48, there is a dust trap in the outer disk and evidence for multiple cavity sizes. We present high angular resolution observations of several disks with the Keck II telescope at infrared wavelengths, primarily 3.7 microns, using adaptive optics and precision calibration techniques including aperture mask interferometry. For Oph IRS 48 and HD 169142, we model the disks using RadMC-3D and show that an azimuthally symmetric disk can model most but not all of the observed structure. In the case of HD 169142, a point-assymetry has been interpreted as direct luminosity from a planet. We discuss alternative explanations from disk emission, showing why interpretation of high angular resolution observations of luminous disk-bearing stars with single telescopes will always be difficult to interpret. A much more ambitious instrument program such as the Planet Formation Imager will be needed to comprehensively disentnagle complex disk evolution from planet formation.

We have identified a new type of dynamical dust–gas instability in protoplanetary discs that produces global toroidal vortices, due to the process of dust settling. We have investigated the evolution of a dusty protoplanetary disc with two different dust species (1 mm and 50 cm dust grains), under the presence of the instability. We show how toroidal vortices, triggered by the interaction of mm grains with the gas, stop the radial migration of metre-sized dust, potentially offering a natural and efficient solution to the dust migration problem.

I will discuss the prospects for observing how super-Earths and giant planetary cores shape the proto-planetary disc. While previous theoretical work has shown how they affect the dust surface density much more than the gas one, no proper study has been conducted of what is the minimum planetary mass that produces observable signatures. I address this problem by running multi-fluid gas and dust simulations and generating simulated observations. I’ll highlight in particular how there exists a minimum planet mass that is able to produce a pressure maximum outside its orbit and therefore a dust trap. Planet masses lower than the threshold can still affect the dust surface density, by creating traffic jams in the dust radial velocity; the minimum planet mass detectable is roughly 10-15 Earth masses, but is a strong function of the disc temperature. Finally, I will discuss how it is possible to have an estimate of the mass of the planet from the observations, which involves measuring either the gap width in scattered light observations or the pressure maximum location in sub-mm images.

Grain growth represents an initial step toward planet formation since it involves the coagulation of approximately micron-sized dust residing in protoplanetary discs around young stars. We have conducted H-band (1.6 um) linear polarimetric observations and 0.88 mm continuum interferometric observations toward a transitional disc around the intermediate-mass pre-main sequence star LkHa 330. The observations show a pair of asymmetric spiral arms in the disc. We discuss the origin of the spiral arms and suggest that a massive unseen planet is the most plausible explanation based on recent global hydro simulations. The possibility of grain growth causing the asymmetric structure of the spiral arms was investigated through the opacity index (beta) by plotting the observed SED slope between 0.88 mm from our SMA observation and 1.3 mm from literature. The results imply that grains are indistinguishable from ISM-like dust in the east side (beta ~ 2.0), but much smaller in the west side (beta ~ 0.7), indicating differential grain growth or dust trapping in the spiral arms. Combining the results of near-infrared and submillimetre observations, we find that the spiral arm is geometrically thick, and that grains grow to millimeter size near the disc mid-plane. Future observations at centimeter wavelengths and differential polarization imaging in other bands (Y to K) with extreme AO imagers are required to understand how large dust grains form and to further explore the dust distribution in the disc.

The discovery of transition disks around young stars has provided the opportunity to study planet formation in situ when giant planet formation and growth are most vigorous. Using the Gemini Planet Imager (GPI) in differential polarimetry mode, we have begun a survey to characterize a statistically-significant sample of young disks at each major stage of planet formation, from the youngest “full disk” stage and through pre-transition and transition disk stages. GPI is ideal for this survey due to its unprecedented sensitivity to scattered light emitted between 20-150 AU from the star, a region of the protoplanetary disk where giant planet formation is known to occur. I will report initial observational results and radiative transfer modeling of a few well-known systems. We explore how to combine ALMA and GPI imaging to measure radial variations in the disk’s grain size distribution, outer disk gas pressure scale heights, and chemical snowlines.

The conference summary talk.

Wine and soft drinks plus snacks will be available to conference delegates prior to Mark McCaughrean’s public lecture.

In this talk Professor Mark McCaughrean, Senior Science Advisor at the European Space Agency, will present some key recent results from ongoing missions.

Mark returns to Exeter after a fantastic sell-out talk earlier in the year to deliver a public talk as part of an international astrophysics conference.

The European Space Agency operates and is partner in a fleet of spacecraft studying the Sun, exploring Earth’s magnetic field, orbiting Mars, Saturn, and Comet 67P/Churymov-Gerasimenko, and collecting photons from across the electromagnetic spectrum, from corners of the Universe near and far.

Mark will talk about missions including the Milky Way surveyor Gaia and the gravitational wave technology testbed LISA Pathfinder. He’ll also give a look forward to two big solar system events: Rosetta will end its mission with a controlled impact on the surface of Comet 67P in September, and ExoMars 2016 puts its entry, descent, and landing module onto the Red Planet in October.