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Linking enhanced star formation and quenching to faint tidal features in galaxies
Full text linkFunding: AJG is supported by a UK Science and Technology Facilities Council (UK STFC) studentship. AMNF is supported by UK Research and Innovation (UKRI) under the UK government’s Horizon Europe funding guarantee [grant number EP/Z534353/1] and by the UK STFC [grant number ST/Y001281/1].Galaxy mergers and interactions have long been suggested as a significant driver of galaxy evolution. However, the exact extent to which mergers enhance star formation and AGN activity has been challenging to establish observationally. In previous work, we visually classified a sample of galaxies with various types of faint tidal features in DECaLS images. In this paper, we crosscorrelate this sample with SDSS-derived data to investigate how the presence and specific nature of these features correlates with intense star formation and AGN activity. Averaged over all tidal classes, we find that our 688 tidal feature galaxies are 6.6 ± 0.9 times more likely to be in a starburst phase and 19.6 ± 5.0 times more likely to have rapidly quenched (post-starbursts) than a sample of 4073 controls matched in both stellar mass and redshift. Examining differences between tidal classes, galaxies with arm features were ∼1.3–4.0 times more likely to be starbursting than the other categories, while those with shell features were ∼2.3–5.3 times more likely to be in a quiescent state. In a similar analysis, we identify which galaxies show evidence of AGN activity (from a sample of ∼2100) and find no significant difference between those with or without tidal features. Overall, our results reinforce the notion that mergers play an important role in driving star formation and rapid quenching in galaxies, and provide some of the first empirical evidence that the strength of this effect has a dependence on the detailed nature of the interaction, as traced by the tidal feature morphology.Peer reviewe
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No full textAbstract redacted"The research presented in this thesis was funded and supported by the joint Diamond Light Source and University of St Andrews (QM-CDT) studentship STU0408"--Fundin
Abstract ping-pong systems in subgroups of Thompson’s groups
Full text linkIn this thesis we study abstract ping-pong systems of homeomorphisms which admit either linear or cyclic orders. Abstract ping-pong systems on sets of permutations were defined by Bleak, Brin, Kassabov, Moore, and Zaremsky as an adaptation of the classical ping-pong lemma; in particular, sets which admit abstract ping-pong systems need not generate free groups.
We first focus on linearly ordered finite abstract ping-pong systems within PL₊(I), the group of piecewise-linear orientation-preserving homeomorphisms of the closed unit interval. It is known that such sets generate groups which embed into Thompson’s group F. We discuss PL₊(I)-transition chains in general, and prove a collection of results sufficient to deduce that a group which admits chains with certain properties must also admit a subgroup isomorphic to Thompson’s group F. We then analyse the dynamical properties of a family of elementary amenable groups defined by Bleak, Brin, and Moore, and prove a foundational case
of a conjecture of Bleak.
Secondly, we consider an infinite family of finite abstract ping-pong systems for homeomorphisms of S¹ equipped with cyclic - but not linear - orders. These sets generate the n-ring groups, defined by Hyde, Lodha, and Rivas. The n-ring groups are known to embed into Thompson’s group T, and to have finitely generated, simple, left orderable commutator subgroups. We are interested in the question of the finite presentability of these groups. We provide an algorithm which generates a recursive presentation for each of these groups, but do not settle this question. We investigate two suggested paths to a proof and demonstrate where they fail
Bowl-shaped corannulene donor-acceptor emitter unlocks host-modulated thermally activated delayed fluorescence/room temperature phosphorescence for oxygen sensing
Full text linkFunding: C. Si and J. Wang are thankful for the financial support from the China Scholarship Council (grant nos. 201806890001 and 202006250026, respectively). The authors are also grateful for the funding from the Engineering and Physical Sciences Research Council (EPSRC) (grant nos. EP/Z535291/1, EP/W007517/1, and EP/W015137/1).While the study of planar polycyclic aromatic hydrocarbons (PAHs) is rich and their properties are well described, the exploitation of curved PAHs such as corannulene derivatives is less established. We report the first example of a corannulene derivative, a donor-substituted corannulene, PXZCor, that exhibited thermally activated delayed fluorescence (TADF). In degassed toluene, PXZCor emitted bright green TADF, with a delayed fluorescence lifetime, τd, of 67.1 μs. At room temperature, doped films of this derivative in poly(methyl methacrylate) (PMMA) exhibited delayed emission of PXZCor, primarily originating from TADF; as the temperature decreased, phosphorescence gradually became the dominant contributor to the delayed emission. In contrast, when PXZCor was doped into the more rigid host using 1,3-bis(N-carbazolyl)benzene (mCP) as the host, a significant TADF emission was observed at room temperature, and distinct phosphorescence only emerged at temperatures below 200 K. PXZCor could act as a potent O2 sensor using emission intensity and lifetime-based assays. Notably, the performance of PXZCor, in lifetime-based detection, ranked among the most effective TADF compounds reported to date for O2 detection down to concentrations as low as 0.01%. These findings highlight the potential of corannulene materials for optoelectronic applications.Peer reviewe
Field theories of strongly correlated, two-dimensional metals : phases and criticality
No full textThis thesis details quantum-field-theoretical analyses of four distinct strongly correlated metallic systems in two spatial dimensions. It begins by examining two driving mechanisms proposed in the literature for the exotic charge-density-wave phase in monolayer vanadium diselenide. The spectral-function-fitting method used to analyse the first proves quite indeterminate, leading to only speculative conclusions. The second mechanism is tested by producing mean-field phase diagrams of the system, yielding an appreciable region of phase space in which it does drive the charge-density wave. In the next chapter, the square-lattice Hubbard model with first-, second- and third-nearest-neighbour hoppings is considered. Phase diagrams are predicted using the few-patch parquet renormalization group and compared with those produced by a colleague using another method, and with those from another patch scheme in the literature. It is concluded that few-patch parquet-renormalization-group schemes are not sophisticated enough to correctly describe many features of this system, and likely other systems.
The second half of the thesis studies non-Fermi liquids. First, the non-Fermi liquid resulting from coupling finite-density fermions to a U(1) gauge field is examined. The functional renormalization group, with a soft frequency regulator for the fermions, is used, and gauge-symmetry constraints are imposed. The resulting bosonic dynamical exponent is z_A = 2, and the fermionic self-energy scales as Σ(ω,k_F) ~ √ω at small frequency. Enforcement of the symmetry constraints leaves the results largely unchanged, but does make the bosonic mass term irrelevant about criticality. In the final research chapter, the non-equilibrium modes of two-dimensional non-Fermi liquids in incipient itinerant ferromagnets are analysed. Linearized quantum Boltzmann equations are solved to find the spectra of charge- and spin-density modes. Whether collective modes are present is found to depend on both universal and non-universal information, in ways previously overlooked. Preliminary results are also given for the spectra when coupling to a classical magnetic field is reincluded
A comprehensive reanalysis of K2-18 b's JWST NIRISS+NIRSpec transmission spectrum
Full text linkFunding: S.P.S. is supported by the National Science Foundation Graduate Research Fellowship Program under grant No. DGE2139757. R.J.M. is supported by NASA through the NASA Hubble Fellowship grant HST-HF2-51513.001, awarded by the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., for NASA, under contract NAS 5-26555. S.-M.T. acknowledges support from NASA Exobiology grant No. 80NSSC20K1437 and the University of California, Riverside. M.R. acknowledges support from the Natural Sciences and Engineering Research Council of Canada (NSERC). T.J.B. acknowledges funding support from the NASA Next Generation Space Telescope Flight Investigations program (now JWST) via WBS 411672.07.04.01.02.Sub-Neptunes are the most common type of planet in our galaxy. Interior structure models suggest that the coldest sub-Neptunes could host liquid water oceans underneath their hydrogen envelopes—sometimes called “hycean” planets. JWST transmission spectra of the ∼250 K sub-Neptune K2-18 b were recently used to report detections of CH4 and CO2, alongside weaker evidence of (CH3)2S (dimethyl sulfide, or DMS). Atmospheric CO2 was interpreted as evidence for a liquid water ocean, while DMS was highlighted as a potential biomarker. However, these notable claims were derived using a single data reduction and retrieval modeling framework, which did not allow for standard robustness tests. Here, we present a comprehensive reanalysis of K2-18 b’s JWST NIRISS SOSS and NIRSpec G395H transmission spectra, including the first analysis of the second-order NIRISS SOSS data. We incorporate multiple well-tested data reduction pipelines and retrieval codes, spanning 60 different data treatments and over 250 atmospheric retrievals. We confirm the detection of CH4 (≈4σ), with a volume mixing ratio range -2.14 ≤ log10CH4 ≤ -0.53, but we find no statistically significant or reliable evidence for CO2 or DMS. Finally, we assess the retrieved atmospheric composition using photochemical-climate and interior models, demonstrating that our revised composition of K2-18 b can be explained by an oxygen-poor mini-Neptune without requiring a liquid water surface or life.Peer reviewe
Immigrant labor market dynamics in Germany by family status
No full textFunding: This paper is part of the MigrantLife project, which received funding from the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme (Grant agreement No. 834103).Background : The labor market activities of immigrants are diverse and highly gendered. Few studies have examined these disparities by legal entry pathway in a multi-state framework that accounts for multiple entries to and exits from the market. Objective : We analyze immigrants’ timing and level of participation in training and labor market activities by gender, parity, and legal entry pathway. Methods : Using data from the German Socio-Economic Panel (GSOEP), we employ competing-risks event history models, treating labor market attachment as a multi-state process. Results : Immigrants from Europe, ex-Yugoslavia, and the former Soviet Union exhibit higher levels of labor market attachment than immigrants from Turkey, Africa, and West Asia. However, we find that the presence of children is more negatively linked to women’s labor force participation for Europeans than non-Europeans. Turkish, West Asian, and African immigrant women are less likely to return to the labor market once they exit. Conclusions : The greater impact of motherhood on the labor market participation of European immigrant women than that of non-European immigrant women is due to their higher participation when childless. However, overall, non-European immigrant women show markedly lower attachment to the labor market regardless of motherhood status. Contribution : This research sheds light on how gender, origin, and entry pathway intersect with family processes, particularly among women, contributing to a deeper understanding of immigrant labor dynamics.Peer reviewe
The making of a movement (together) : how climate activists perceive Greta Thunberg's leadership
No full textDrawing on the Social Identity Theory of Leadership, this study explores how Greta Thunberg's influence emerges through group processes where her leadership is sustained among climate activists by perceptions of one of us and doing it for us. Using a qualitative survey of 108 climate activists from the United Kingdom, Turkey and Sweden, we examine how these perceptions are constructed and maintained by climate activists across different socio-political contexts. Although many activists view Thunberg as central to raising awareness and mobilising action, her leadership is seen as effective when it aligns with collective values and identity. Perceptions of her leadership are dynamic and shaped by her behaviour, rhetoric and evolving relationships with activists, media and political actors. Some participants expressed concern about her dominance in the public narrative and questioned her representativeness due to her privileged background (e.g., middle-class White European). Notably, identity prototypicality (one of us) and advancement (doing it for us) were closely linked: Activists often cited the same actions or messages as evidence of both. Findings highlight the mutual influence of leadership and movement identity. Although prototypical leaders embody the movement's identity and facilitate collective agency, leaders who inspire mobilisation and organise collective actions for activists to enact their identity are perceived as more prototypical.Peer reviewe
exoALMA. IV. Substructures, asymmetries, and the faint outer disk in continuum emission
No full textFunding: P.C. acknowledges support by the Italian Ministero dell’Istruzione, Università e Ricerca through the grant Progetti Premiali 2012-iALMA (CUP C52I13000140001) and by the ANID BASAL project FB210003. S.F. is funded by the European Union (ERC, UNVEIL, 101076613), and acknowledges financial contribution from PRIN-MUR 2022YP5ACE. J.B. acknowledges support from NASA XRP grant No. 80NSSC23K1312. M.B., D.F., J.S, and A.W. have received funding from the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation program (PROTOPLANETS, grant agreement No. 101002188). M.F. has received funding from the European Research Council (ERC) under the European Unions Horizon 2020 research and innovation program (grant agreement No. 757957). M.F. is supported by a grant-in-aid from the Japan Society for the Promotion of Science (KAKENHI: No. JP22H01274). C.H. acknowledges support from NSF AAG grant No. 2407679. J.D.I. acknowledges support from an STFC Ernest Rutherford Fellowship (ST/W004119/1) and a University Academic Fellowship from the University of Leeds. A.I. acknowledges support from the National Aeronautics and Space Administration under grant No. 80NSSC18K0828. Support for A.F.I. was provided by NASA through the NASA Hubble Fellowship grant No. HST-HF2-51532.001-A awarded by the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., for NASA, under contract NAS5-26555. G.L. has received funding from the European Research Council (ERC) under the European Union Horizon 2020 research and innovation program (Grant agreement no. 815559 (MHDiscs)). G.L. and C.L. have received funding from the European Union's Horizon 2020 research and innovation program under the Marie Sklodowska-Curie grant agreement No. 823823 (DUSTBUSTERS). C.L. acknowledges support from the UK Science and Technology Research Council (STFC) via the consolidated grant ST/W000997/1. C.P. acknowledges Australian Research Council funding via FT170100040, DP18010423, DP220103767, and DP240103290. D.P. acknowledges Australian Research Council funding via DP18010423, DP220103767, and DP240103290. G.R. acknowledges funding from the Fondazione Cariplo, grant No. 2022-1217, and the European Research Council (ERC) under the European Union’s Horizon Europe Research & Innovation Programme under grant agreement No. 101039651 (DiscEvol). F.M. received funding from the European Research Council (ERC) under the European Union’s Horizon Europe research and innovation program (grant agreement No. 101053020, project Dust2Planets). N.C. has received funding from the European Research Council (ERC) under the European Union Horizon Europe research and innovation program (grant agreement No. 101042275, project Stellar-MADE). L.T. acknowledges funding from Progetti Premiali 2012 iALMA (CUP C52I13000140001), Deutsche Forschungs-gemeinschaft (German Research Foundation) reference No. 325594231 FOR 2634/1 TE 1024/1-1, European Union’s Horizon 2020 research and innovation program under the Marie Sklodowska-Curie grant No. 823823 (DUSTBUSTERS), and the ERC via the ERC Synergy grant ECOGAL (grant No. 855130). T.C.Y. acknowledges support by Grant-in-Aid for JSPS Fellows JP23KJ1008. H.-W.Y. acknowledges support from the National Science and Technology Council (NSTC) in Taiwan through grant NSTC 113-2112-M-001-035- and from the Academia Sinica Career Development Award (AS-CDA-111-M03). G.W.F. acknowledges support from the European Research Council (ERC) under the European Union Horizon 2020 research and innovation program (grant agreement No. 815559 (MHDiscs)). G.W.F. was granted access to the HPC resources of IDRIS under the allocation A0120402231 made by GENCI. Support for B.Z. was provided by The Brinson Foundation.The exoALMA Large Program targeted a sample of 15 disks to study gas dynamics within these systems, and these observations simultaneously produced continuum data at 0.9 mm (331.6 GHz) with exceptional surface brightness sensitivity at high angular resolution. To provide a robust characterization of the observed substructures, we performed a visibility space analysis of the continuum emission from the exoALMA data, characterizing axisymmetric substructures and nonaxisymmetric residuals obtained by subtracting an axisymmetric model from the observed data. We defined a nonaxisymmetry index and found that the most asymmetric disks predominantly show an inner cavity and consistently present higher values of mass accretion rate and near-infrared excess. This suggests a connection between outer disk dust substructures and inner disk properties. The depth of the data allowed us to describe the azimuthally averaged continuum emission in the outer disk, revealing that larger disks (both in dust and gas) in our sample tend to be gradually tapered compared to the sharper outer edge of more compact sources. Additionally, the data quality revealed peculiar features in various sources, such as shadows, inner disk offsets, tentative external substructures, and a possible dust cavity wall.Peer reviewe
Constraining lens masses in moderately to highly magnified microlensing events from Gaia
No full textFunding: This project has received funding from the European Union’s Horizon Europe Research and Innovation programme ACME under grant agreement No 101131928 (2024-2028). ZTF is supported by the National Science Foundation under Grants No. AST-1440341 and AST-2034437. This work was partially funded by Kepler/K2 grant J1944/80NSSC19K0112 and HST GO-15889, and STFC grants ST/T000198/1 and ST/S006109/1. YT acknowledges the support of DFG priority program SPP 1992 "Exploring the Diversity of Extrasolar Planets" (TS 356/3-1). RAS and EB gratefully acknowledge support from the NASA XRP Program, through grant number 80NSSC19K0291. The Omega Key Project has received funding from the European Union’s Horizon 2020 research and innovation program under grant agreement No. 101004719 (OPTICON - RadioNet Pilot). This work is supported by the Polish MNiSW grant DIR/WK/2018/12. Josep Manel Carrasco work was (partially) supported by the Spanish MICIN/AEI/10.13039/501100011033 and by ”ERDF A way of making Europe” by the ”European Union” through grant PID2021-122842OB-C21, and the Institute of Cosmos Sciences University of Barcelona (ICCUB, Unidad de Excelencia ”María de Maeztu”) through grant CEX2019-000918-M and the project 2021-SGR-00679 GRC de l’Agència de Gestió d’Ajuts Universitaris i de Recerca (Generalitat de Catalunya). G.D., M.S. and M.D.J acknowledge support by the Astronomical Station Vidojevica and the Ministry of Science, Technological Development and Innovation of the Republic of Serbia (MSTDIRS) through contract no. 451-03-136/2025-03/200002 made with Astronomical Observatory (Belgrade), by the EC through project BELISSIMA (call FP7-REGPOT-2010-5, No. 256772), the observing and financial grant support from the Institute of Astronomy and Rozhen NAO BAS through the bilateral SANU-BAN joint research project "GAIA astrometry and fast variable astronomical objects", and support by the SANU project F-187. Also, this research was supported by the Science Fund of the Republic of Serbia, grant no. 6775, Urban Observatory of Belgrade - UrbObsBel. T.G. and the IST60 Telescope has been supported by the Scientific Research Projects Coordination Unit of Istanbul University (Project No.: TSG-2023-40046 and FBG-2017-23943) Turkish Republic, Directorate of Presidential Strategy and Budget project, 2016K121370. This work is partially supported by the Fundamental Fund of Thailand Science Research and Innovation (TSRI) through the National Astronomical Research Institute of Thailand (Public Organization) (FFB680072/0269). J.Z. and E.P. acknowledge funding from the Research Council of Lithuania (LMTLT, grant No. S-LL-24-1).Context . Microlensing events provide a unique way to detect and measure the masses of isolated, non-luminous objects, particularly dark stellar remnants. Under certain conditions, it is possible to measure the mass of these objects using photometry alone, specifically when a microlensing light curve displays a finite source (FS) effect. This effect generally occurs in highly magnified light curves, i.e. when the source and the lens are very well aligned. Aims . In this study, we analyse Gaia Alerts and Gaia Data Release 3 datasets, identifying four moderate-to-high-magnification microlensing events without a discernible FS effect. The absence of this effect suggests a large Einstein radius, implying substantial lens masses. Methods . In each event, we constrained the FS effect, and therefore established lower limits for the angular Einstein radius and lens mass. Additionally, we used the DarkLensCode software to obtain the mass, distance, and brightness distribution for the lens based on the Galactic model. Results . Our analysis established lower mass limits of ∼0.7 M⊙ for one lens and ∼0.3 − 0.5 M⊙ for two others. A DarkLensCode analysis supports these findings, estimating lens masses in the range of ∼0.42 − 1.70 M⊙ and dark lens probabilities exceeding 80%. These results strongly indicate that the lenses are stellar remnants, such as white dwarfs or neutron stars. Conclusions . While further investigations are required to confirm the nature of these lenses, we demonstrate a straightforward yet effective approach to identifying stellar remnant candidates.Peer reviewe
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