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Galaxy evolution in the post-merger regime. II - post-merger quenching peaks within 500 Myr of coalescence
Get PDFMechanisms for quenching star formation in galaxies remain hotly debated, with galaxy mergers an oft-proposed pathway. In Ellison et al. (2022) we tested this scenario by quantifying the fraction of recently and rapidly quenched post-starbursts (PSBs) in a sample of post-merger galaxies identified in the Ultraviolet Near Infrared Optical Northern Survey (UNIONS). Compared with a control sample of non-interacting galaxies, Ellison et al. (2022) found PSBs to be a factor of 30-60 more common in the post-mergers, demonstrating that mergers can lead to quenching. However, the exact timing of this post-merger quenching was unconstrained. Thanks to our recent development of the Multi-Mode Merger Identifier (mummi) neural network ensemble (Ferreira et al. 2024a,b), we are now able to predict the time since coalescence (TPM) for the UNIONS post-merger galaxies up to TPM = 1.8Gyr, allowing us to further dissect the merger sequence and measure more precisely when quenching occurs. Based on a sample of 5927 z < 0.3 post-mergers identified in UNIONS, we find that the post-coalescence population evolves from one dominated by star-forming (and starbursting) galaxies at 0 < TPM < 0.16 Gyr, through to a population that is dominated by quenched galaxies by TPM ∼1.5 Gyr. By combining the post-mergers with a sample of 15,831 spectroscopic galaxy pairs with projected separations rp < 100 kpc we are able to trace the evolution of quenching during the full merger sequence. We find a PSB excess throughout the post-merger regime, but with a clear peak at 0.16 < TPM < 0.48 Gyr. In this post-merger time range PSBs are more common than in control galaxies by factors of 30-100 (depending on PSB selection method), an excess that drops sharply at longer times since merger. We also quantify the fraction of PSBs that are mergers and find that the majority (75 per cent) of classically selected E+A are identified as either pairs or post-mergers, with a lower merger fraction (60 per cent) amongst PCA selected PSBs. The merger fraction of PSB galaxies also correlates strongly with stellar mass. Taken together, our results demonstrate that 1) galaxy-galaxy interactions can lead to rapid post-merger quenching within 0.5 Gyr of coalescence, 2) the majority of (but not all) PSBs at low z are linked to mergers and 3) quenching pathways are diverse, with different PSB selection techniques likely identifying galaxies quenched by different physical processes with an additional dependence on stellar mass.Peer reviewe
Hints of a close outer companion to the ultra-hot Jupiter TOI-2109 b?
Get PDFFunding: ACC acknowledges support from STFC consolidated grant number ST/V000861/1, and UKSA grant number ST/X002217/1. CHe acknowledges support from the European Union H2020-MSCA-ITN-2019 under Grant Agreement no. 860470 (CHAMELEON). PM acknowledges support from STFC research grant number ST/R000638/1. NCSa acknowledges funding by the European Union (ERC, FIERCE, 101052347). NAW acknowledges UKSA grant ST/R004838/1.Context. Hot Jupiters (HJs) with close-by planetary companions are rare, with only a handful of them having been discovered so far. This could be due to their suggested dynamical histories, which lead to the possible ejection of other planets. TOI-2109 b is special in this regard because it is the HJ with the closest relative separation from its host star, being separated by less than 2.3 stellar radii. Unexpectedly, transit timing measurements from recently obtained CHEOPS observations show low-amplitude transit-timing variations (TTVs). Aims. We aim to search for signs of orbital decay and to characterise the apparent TTVs in an attempt to gain information about a possible companion. Methods. We fitted the newly obtained CHEOPS light curves using TLCM and extracted the resulting mid-transit timings. Successively, we used these measurements in combination with TESS and archival photometric data and radial velocity (RV) data to estimate the rate of tidal orbital decay of TOI-2109 b, and also to characterise the TTVs using the N-body code TRADES and the photo-dynamical approach of PyTTV. Results. We find tentative evidence at 3σ for orbital decay in the TOI-2109 system when we correct the mid-transit timings using the best-fitting sinusoidal model of the TTVs. We do not detect additional transits in the available photometric data, but find evidence supporting the authenticity of the apparent TTVs, indicating a close-by, outer companion with Pc > 1.125 d. Due to the fast rotation of the star, the new planetary candidate cannot be detected in the available RV measurements, and its parameters can only be loosely constrained by our joint TTV and RV modelling. Conclusions. TOI-2109 could join a small group of rare HJ systems that host close-by planetary companions, only one of which (WASP-47 b) has an outer companion. More high-precision photometric measurements are necessary to confirm the existence of this planetary companion.Peer reviewe
Influence of intrinsic spin ordering in La0.6Sr0.4Co0.8Fe0.2O3−δ and Ba0.6Sr0.4Co0.8Fe0.2O3−δ towards electrocatalysis of oxygen redox reaction in solid oxide cell
No full textFunding: J. M. acknowledges Director CSIR-CGCRI for kind support. CSIR-H2T Mission program is acknowledged for financial and technical support.The redox reaction of oxygen (OER & ORR) forms the rate determining step of important processes like cellular respiration and water splitting. Being a spin relaxed process governed by quantum spin exchange interaction, QSEI (the ground triplet state in O2 is associated with singlet oxygen in H2O/OH−), its kinetics is sluggish and requires inclusion of selective catalyst. Functionality and sustainability of solid oxide cell involving fuel cell (FC) and electrolyzer cell (EC) are also controlled by ORR (oxygen redox reaction) and OER (oxygen evolution reaction). We suggest that, presence of inherent spin polarization within La0.6Sr0.4Co0.8Fe0.2O3−δ (LSCF6482) (15.86 emu g−1) and Ba0.6Sr0.4Co0.8Fe0.2O3−δ (BSCF6482) (3.64 emu g−1) accounts for the excellent selective electrocatalysis towards ORR and OER. QSEI forms the atomic level basis for OER/ORR which is directly proportional to spin ordering (non-zero magnetization) of the active electrocatalyst. LSCF6482 exhibits (21.5 kJ mol−[email protected] V for ORR compared to 61 kJ mol−[email protected] V for OER) improved ORR kinetics whereas BSCF6482 (18.79 kJ mol−[email protected] V for OER compared to 32.19 kJ mol−1 for ORR@−0.8 V) is best suited for OER under the present stoichiometry. The findings establish the presence of inherent spin polarization of catalyst to be an effective descriptor for OER and ORR kinetics in solid oxide cell (SOC).Peer reviewe
In situ zooplankton density estimates at a foraging site in the Canadian Arctic are below minimum prey thresholds for adult bowhead whales (Balaena mysticetus)
Get PDFFunding: The authors would like to thank the Department of Fisheries and Oceans Canada, the Ocean Frontier Institute, the Northern Student Travel Program, and ArcticNet for funding this project, and the University of St Andrews School of Biology/AD Links Foundation for funding H.M.’s PhD studies.Bowhead whales (Balaena mysticetus) are an iconic Arctic species with a critical ecological role as a top predator. Bowheads can reach up to 80 tonnes and 20 m, yet feed on zooplankton four orders of magnitude smaller. Arctic zooplankton community composition and distribution are changing, which may have direct impacts on bowhead foraging. Data on the threshold prey density for successful bowhead feeding are needed to predict these impacts. However, zooplankton densities are patchy temporally and spatially, influenced by oceanographic conditions that alter the location of energetically profitable patches. We assessed spatio-temporal patterns in zooplankton abundance and distribution using a multi-frequency echosounder following a systematic and opportunistic survey near feeding whales in Iqalujjuaq Fjord, Cumberland Sound, Nunavut (65.66°N, 65.20°W) during August 2023. Zooplankton net samples were used to validate the acoustic data. There was a strong link between copepod distribution and environmental variables (e.g. water depth and tidal cycle) (generalized additive models, P 0.44 g C m−3).Peer reviewe
Facile, reversible hydrogen activation by low-coordinate magnesium oxide complexes
Get PDFFunding: The authors thank the EaSI-CAT Centre for Doctoral Training (S.T.), the EPSRC doctoral training grant (EP/N509759/1, S.B.) and the University of St Andrews for support. The authors gratefully acknowledge computational support via the EaStCHEM Research Computing Facility.New approaches to achieve facile and reversible dihydrogen activation are of importance for synthesis, catalysis, and hydrogen storage. Here we show that low-coordinate magnesium oxide complexes [{(RDipnacnac)Mg}2(μ-O)] 1 , with RDipnacnac = HC(RCNDip)2, Dip = 2,6-iPr2C6H3, R = Me ( 1a ), Et ( 1b ), iPr ( 1c ), readily react with dihydrogen under mild conditions to afford mixed hydride-hydroxide complexes [{(RDipnacnac)Mg}2(μ-H)(μ-OH)] 4 . Dehydrogenation of complexes 4 is strongly dependent on remote ligand substitution and can be achieved by simple vacuum-degassing of 4c (R = iPr) to regain 1c . Donor addition to complexes 4 also releases hydrogen and affords donor adducts of magnesium oxide complexes. Computational studies suggest that the hydrogen activation mechanism involves nucleophilic attack of an oxide lone pair at a weakly-bound H2···Mg complex in an SN2-like manner that induces a heterolytic dihydrogen cleavage to yield an MgOH and an MgH unit. Alternative synthetic routes into complex 4b from a magnesium hydride complex have been investigated and the ability of complexes 1 or 4 to act as catalysts for the hydrogenation of 1,1-diphenylethene (DPE) has been tested.Peer reviewe
The genome sequence of Molossus alvarezi González-Ruiz, Ramírez-Pulido and Arroyo-Cabrales, 2011 (Chiroptera, Molossidae)
Get PDFFunding: SCV was supported by a UKRI Future Leaders Fellowship, (MR/T021985/1), an ERC Consolidator Grant (101001702; BATSPEAK), and a Max Planck Research Group awarded by the Max Planck Society). MRI was supported by a Peter Buck Postdoctoral Fellowship from the Smithsonian National Museum of Natural History. ECT is a Wellcome collaborator and the Irish Research Council Laureate Award IRCLA/2017/58 and Science Foundation Ireland Future Frontiers 19/FFP/6790. Fieldwork by NBS was supported by the Taxonomic Mammalogy Fund of the American Museum of Natural History.We present a genome assembly from an individual female Molossus alvarezi (Chordata; Mammalia; Chiroptera; Molossidae). The genome sequence is 2.490 Gb in span. The majority of the assembly is scaffolded into 24 chromosomal pseudomolecules, with the X sex chromosomes assembled.Peer reviewe
Kinetic and thermodynamic characterization of human 4-oxo-L-proline reductase catalysis
Get PDFFunding: This work was supported by a Cunningham Trust Ph.D. Award (Grant PhD-CT-21-04) to R.G.d.S., which supports a Ph.D. studentship to E.P.The enzyme 4-oxo-l-proline reductase (BDH2) has recently been identified in humans. BDH2, previously thought to be a cytosolic (R)-3-hydroxybutyrate dehydrogenase, actually catalyzes the NADH-dependent reduction of 4-oxo-L-proline to cis-4-hydroxy-L-proline, a compound with known anticancer activity. Here we provide an initial mechanistic characterization of the BDH2-catalyzed reaction. Haldane relationships show the reaction equilibrium strongly favors the formation of cis-4-hydroxy-L-proline. Stereospecific deuteration of NADH C4 coupled with mass spectrometry analysis of the reaction established that the pro-S hydrogen is transferred. NADH is co-purified with the enzyme, and a binding kinetics competition assays with NAD+ defined dissociation rate constants for NADH of 0.13 s–1 at 5 °C and 7.2 s–1 at 25 °C. Isothermal titration calorimetry at 25 °C defined equilibrium dissociation constants of 0.48 and 29 μM for the BDH2:NADH and BDH2:NAD+ complexes, respectively. Differential scanning fluorimetry showed BDH2 is highly thermostabilized by NADH and NAD+. The kcat/KM pH–rate profile indicates that a group with a pKa of 7.3 and possibly another with a pKa of 8.7 must be deprotonated and protonated, respectively, for maximum binding of 4-oxo-L-proline and/or catalysis, while the kcat profile is largely insensitive to pH in the pH range used. The single-turnover rate constant is only 2-fold higher than kcat. This agrees with a pre-steady-state burst of substrate consumption, suggesting that a step after chemistry, possibly product release, contributes to limit kcat. A modest solvent viscosity effect on kcat indicates that this step is only partially diffusional. Taken together, these data suggest chemistry does not limit the reaction rate but may contribute to it.Peer reviewe
Fractal percolation on statistically self-affine carpets
Get PDFWe consider a random self-affine carpet F based on an n x m subdivision of rectangles and a probability 0<p<1. Starting by dividing [0,1]2 into an n x m grid of rectangles and selecting these independently with probability p, we then divide the selected rectangles into n x m subrectangles which are again selected with probability p; we continue in this way to obtain a statistically self-affine set F. We are particularly interested in topological properties of F. We show that the critical value of p above which there is a positive probability that F connects the left and right edges of [0,1]2 is the same as the critical value for F to connect the top and bottom edges of [0,1]2. Once this is established we derive various topological properties of F analogous to those known for self-similar carpets.Peer reviewe
The genome sequence of the greater two-lined sac-winged bat Saccopteryx bilineata, Temminck, 1838 (Emballonuridae, Emballonurinae)
Get PDFFunding: SCV was supported by a UKRI Future Leaders Fellowship, (MR/T021985/1), an ERC Consolidator Grant (101001702; BATSPEAK), and a Max Planck Research Group awarded by the Max Planck Society. ECT is a Wellcome collaborator and the Irish Research Council Laureate Award IRCLA/2017/58 and Science Foundation Ireland Future Frontiers 19/FFP/6790. Fieldwork by BKL was supported by Environmental Services & Support in Suriname.We present a genome assembly from an individual male Saccopteryx bilineata (Chordata; Mammalia; Chiroptera; Emballonuridae). The genome sequence is 2.62Gb in span. The majority of the assembly is scaffolded into 13 chromosomal pseudomolecules, with the X sex chromosome assembled.Peer reviewe
Interprofessional collaborative practice in health and social care for people living with multimorbidity : a scoping review protocol
Get PDFFunding: JLKM is a fellow on the Multimorbidity Doctoral Training Programme for Health Professionals, which is supported by the Wellcome Trust [223499/Z/21/Z].Background Multimorbidity, the co-existence of two or more conditions within an individual at any one time, is globally increasing and forecasted to rise. This poses a significant challenge for current models of healthcare delivery, which are now ill-equipped to meet the future population health needs. Interprofessional collaborative practice is a specific way professionals work closely together and with patients and their families to improve patient outcomes. Evidence suggests it can improve outcomes for people living with a single condition. What remains unknown is if interprofessional collaborative practice has been used to improve the outcomes of people living with multimorbidity, and if so, to what extent? Methods A scoping review is proposed to identify prior peer-reviewed research and grey literature related to interprofessional collaborative practice for multimorbidity in health and social care settings. A search strategy will identify primary, peer-reviewed research and grey literature. An initial limited search will be conducted to identify relevant existing systematic reviews. Their methods will be examined and their search terms scrutinised. A second comprehensive search will be used to interrogate four databases, looking back 10 years, seeking articles published in English, French, Spanish or Portuguese. Hand searching will be performed on all included full-text articles for any articles missing from the two steps above. Critical data will be extracted by adapting existing data abstraction forms based on the needs of the research objectives. These forms will be piloted before use. The results will be analysed descriptively. If appropriate, qualitative content analysis may be undertaken. Where sufficient numbers of homogeneous interventions exist, meta-analysis techniques will be applied. Results will be presented in tabular, graphic, and diagrammatic information displays. Discussion This scoping review will provide an overview of the current evidence base of interprofessional collaborative practice used internationally for people living with multimorbidity in health and social care settings. These findings will provide valuable information to improve health and social care practice as well as change systems and policy to meet the population need of multimorbidity.Peer reviewe
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