20 research outputs found
In the making : the 'Power to the People' workshop track at Crafting the Future
No full textJulia Keyte - Contributing author - Section : Making, gifting and connecting (p. 384-387
Abundance and Distribution of Volatiles in Planet-Forming Disks
No full textThis thesis explores the fundamental relationship between the physical and chemical properties of protoplanetary disks and the exoplanetary systems that form within them. High-resolution submillimeter observations from Atacama Large Millimeter/submillimeter Array (ALMA) have revolutionised our ability to study these disks in unprecedented detail. By leveraging ALMA observations and sophisticated thermochemical modelling, this work constrains the composition of gas potentially accreted by nascent planets, establishing a direct link between their atmospheric composition and birth environment.
Firstly, the abundances and distribution of volatile carbon and oxygen in the HD 100546 protoplanetary disk are characterised. Analysis of ALMA observations
of emission from CS and SO is used to trace the C/O ratio of the gas, a well-established metric for tracing a planet’s formation location. Azimuthal variations in the emission from these sulfur-bearing molecules are shown to originate from an azimuthal variation in C/O ratio itself. This finding contributes a new layer of complexity to the understanding of factors influencing exoplanetary atmospheric composition.
Next, ALMA observations of sulfur-bearing species in HD 100546 are again utilised, this time to tightly constrain the total abundance of volatile sulfur at scales relevant to planetary formation. This work addresses the longstanding ‘missing sulfur problem’ in planet-forming environments, where significant depletion of gas-phase sulfur is observed. A depletion factor of ∼ 1000 for gas-phase sulfur is revealed in this system, with radial variations exceeding three orders of magnitude. These variations are linked to the location of prominent dust rings and gaps within the disk. It is further shown that the vast majority of elemental sulfur is sequestered in refractory materials, with less ≲ 5% residing in the gas and ices combined.
Finally, the volatile composition of the planet-hosting disk HD 169142 is investigated. Carbon and oxygen abundances are shown to be generally not depleted compared to other protoplanetary disk systems. Depletion of sulfur is observed at a level comparable to HD 100546. Significantly, the detection of SiS emission from this disk constitutes the major finding of this work. The detection of SiS is indicative of shocked gas near the embedded protoplanet, potentially providing crucial insights into the dynamical processes shaping the early environment of this planetary system
Azimuthal C/O Variations in a Planet-Forming Disk
No full textDALI physical-chemical disk models presented in 'Azimuthal C/O Variations in a Planet-Forming Disk' (Keyte et al. 2023).
There are two individual models included here. The 'baseline' model is used to produce outputs for the region of the disk where C/O=0.5. The 'elevated' model is used to produce outputs for the regions of the disk where C/O=1.5.
The baseline model can be run in the normal way, but the outputs themselves are already included in the folder.
The 'elevated' model will not run in the regular way. The source code has been edited so that it can take in the abundances from a previous run as the starting point for the chemistry (in the form of an out.dat style table). The outputs are already included, but should you want to rerun the model yourself, follow the steps in the readme file within the folder.
The final 'composite' model presented in the paper is created by splicing together the outputs (as described in Keyte et al. 2023). This is achieved using a custom Python script, please contact me if you would like to use this
Spatially resolving the volatile sulfur abundance in the HD 100546 protoplanetary disc
No full textVolatile elements play a crucial role in the formation of planetary systems. Their abundance and distribution in protoplanetary discs provide vital insights into the connection between formation processes and the atmospheric composition of individual planets. Sulfur, being one of the most abundant elements in planet-forming environments, is of great significance, and now observable in exoplanets with JWST. However, planetary formation models currently lack vital knowledge regarding sulfur chemistry in protoplanetary discs. Developing a deeper understanding of the major volatile sulfur carriers in discs is essential to building models that can meaningfully predict planetary atmospheric composition, and reconstruct planetary formation pathways. In this work, we combine archival observations with new data from the Atacama Large sub-Millimeter Array (ALMA) and the Atacama Pathfinder EXperiment (APEX), covering a range of sulfur-bearing species/isotopologs. We interpret this data using the DALI thermo-chemical code, for which our model is highly refined and disc-specific. We find that volatile sulfur is heavily depleted from the cosmic value by a factor of ∼1000, with a disc-averaged abundance of S/H ∼ 10−8. We show that the gas-phase sulfur abundance varies radially by ≳3 orders of magnitude, with the highest abundances inside the inner dust ring and coincident with the outer dust ring at r ∼ 150–230 au. Extracting chemical abundances from our models, we find OCS, H2CS, and CS to be the dominant molecular carriers in the gas phase. We also infer the presence of a substantial OCS ice reservoir. We relate our results to the potential atmospheric composition of planets in HD 100546, and the wider exoplanet population
Planet gap-opening feedback on disc thermal structure and composition
No full text(Exo-)planets inherit their budget of chemical elements from a protoplanetary disc. The disc temperature determines the phase of each chemical species, which sets the composition of solids and gas available for planet formation. We investigate how gap structures, which are widely seen by recent disc observations, alter the thermal and chemical structure of a disc. Planet–disc interaction is a leading hypothesis of gap formation and so such changes could present a feedback that planets have on planet-forming material. Both the planet gap-opening process and the disc thermal structure are well studied individually, but how the gap-opening process affects disc thermal structure evolution remains an open question. We develop a new modelling method by iterating hydrodynamical and radiative transfer simulations to explore the gap-opening feedback on disc thermal structure. We carry out parameter studies by considering different planet locations rp and planet masses Mp. We find that for the same rp and Mp, our iteration method predicts a wider and deeper gap than the non-iteration method. We also find that the inner disc and gap temperature from the iteration method can vary strongly from the non-iteration or disc without planets, which can further influence dust-trap conditions, iceline locations, and distribution of various ices, such as H2O, CO2, and CO on large dust grains (‘pebbles’). Through that, a gap-opening planet can complicate the canonical picture of the non-planet disc C/O ratio and influence the composition of the next generation of planetesimals and planets
‘Synge we now alle and sum’: three Fifteenth-Century collections of communal song: a study of British Library, Sloane MS 2593; Bodleian Library, MS Eng. poet. e.1; and St John’s College, Cambridge, MS S.54
No full textThe manuscripts British Library, Sloane MS 2593, Bodleian Library, MS Eng. poet. e.1, and St John’s College, Cambridge, MS S.54 are compact collections of song lyrics written during the fifteenth century, largely without notation. My thesis seeks to develop responsive ways of reading these anthologies and uses the manuscripts to illumine the creative processes that produced and circulated their songs. I integrate attention to song lyrics within the material books and exploration of wider textual networks. As many of the anthologies’ texts are in
carol form, a combination of refrain parts and stanzas, the books provide an opportunity to examine the form’s identity and significance within fifteenth-century English songwriting.
The thesis is in three parts and the first introduces critical approaches to the manuscripts and the carol, followed by an examination of the books and their contexts, especially manuscripts with which the anthologies have textual connections. The central section investigates the songs’ production and circulation by examining textual networks, how the anthologies were written, how the songs may have been performed, and the role of memory in shaping the songs and anthologies. The final part explores women’s role in the songs, the range of forms used, and the centrality of the many imagined voices and performances within the texts.
This is the first extended study focused upon these three sources, which as anthologies offer insight into ways songs were shared and organised. I investigate the role of short collections and booklets in the construction of longer
anthologies, and the possibility of an especially productive song culture within fifteenth-century East Anglia. Rather than repeating assertions familiar from
earlier studies of carols that the anthologies’ songs are either popular or clerical productions, I suggest how the anthologies engage with communal performance cultures and participate in varied song traditions, from liturgy to lullaby
Azimuthal C/O variations in a planet-forming disk
No full textThe elemental carbon-to-oxygen ratio (C/O) in the atmosphere of a giant planet is a promising diagnostic of that planet’s formation history in a protoplanetary disk. Alongside efforts in the exoplanet community to measure the C/O ratio in planetary atmospheres, observational and theoretical studies of disks are increasingly focused on understanding how the gas-phase C/O ratio varies both with radial location and between disks. This is mostly tied to the icelines of major volatile carriers such as CO and H2O. Using ALMA observations of CS and SO, we have found evidence for an entirely unexpected type of C/O variation in the protoplanetary disk around HD 100546: an azimuthal variation from a typical, oxygen-dominated ratio (C/O ≈ 0.5) to a carbon-dominated ratio (C/O ≳ 1.0). We show that the spatial distribution and peculiar line kinematics of both CS and SO molecules can be well explained by azimuthal variations in the C/O ratio. We propose a shadowing mechanism that could lead to such a chemical dichotomy. Our results imply that tracing the formation history of giant exoplanets using their atmospheric C/O ratios will need to take into account time-dependent azimuthal C/O variations in a planet’s accretion zone
Author Correction: Azimuthal C/O variations in a planet-forming disk
No full textCorrection to: Nature Astronomy https://doi.org/10.1038/s41550-023-01951-9. Published online 20 April 2023
Constraints on the Gas-phase C/O Ratio of DR Tau's Outer Disk from CS, SO, and C<sub>2</sub>H Observations
No full textInternational audienceMillimeter wavelength observations of Class II protoplanetary disks often display strong emission from hydrocarbons and high CS/SO values, providing evidence that the gas-phase C/O ratio commonly exceeds 1 in their outer regions. We present new NOEMA observations of CS 5–4, SO 76–65 and 56–45, C2H N = 3–2, HCN 3–2, HCO+ 3–2, and H13CO+ 3–2 in the DR Tau protoplanetary disk at a resolution of ∼0.″4 (80 au). Estimates for the disk-averaged CS/SO ratio range from ∼0.4 to 0.5, the lowest value reported thus far for a T Tauri disk. At a projected separation of ∼180 au northeast of the star, the SO moment maps exhibit a clump that has no counterpart in the other lines, and the CS/SO value decreases to <0.2 at its location. Thermochemical models calculated with DALI indicate that DR Tau's low CS/SO ratio and faint C2H emission can be explained by a gas-phase C/O ratio that is <1 at the disk radii traced by NOEMA. Comparisons of DR Tau's SO emission to maps of extended structures traced by 13CO suggest that late infall may contribute to driving down the gas-phase C/O ratio of its disk
The Institutional Framework for Doing Sports Business: Principles of EU Competition Policy in Sports Markets
No full textThe competition rules and policy framework of the European Union represents an important institutional restriction for doing sports business. Driven by the courts, the 2007 overhaul of the approach and methodology has increased the scope of competition policy towards sports associations and clubs. Nowadays, virtually all activities of sports associations that govern and organize a sports discipline with business elements are subject to antitrust rules. This includes genuine sporting rules that are essential for a league, championship or tourna-ment to come into existence. Of course, ‘real’ business or commercial activities like ticket selling, marketing of broadcasting rights, etc. also have to comply with competition rules. Regulatory activities of sports associations comply with European competition rules if they pursuit a legitimate objective, its restrictive effects are inherent to that objective and proportionate to it. This new approach offers important orientation for the strategy choice of sports associations, clubs and related enterprises. Since this assessment is done following a case-by-case approach, however, neither a blacklist of anticompetitive nor a whitelist of procompetitive sporting rules can be derived. Instead, conclusions can be drawn only from the existing case decisions – but, unfortunately, this leaves many aspects open. With respect to business activities, the focus of European competition policy is on centralized marketing arrangements bundling media rights. These constitute cartels and are viewed to be anticompetitive in nature. However, they may be exempted from the cartel prohibition on efficiency and consumer benefits considerations. Here, a detailed list of conditions exists that centralized marketing arrangements must comply with in order to be legal. Although this policy seems to be well-developed at first sight, a closer look at the decision practice reveals several open problems. Other areas of the buying and selling behavior of sports associations and related enterprises are considerably less well-developed and do not provide much orientation for business. The author would like to thank Arne Feddersen and the participants of the 2nd European Conference on Sports Economics (German Sports University Co-logne, 2010) for valuable comments on earlier versions of this paper.Sports business, competition policy, sporting rules, centralized marketing, sports economics
