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Inferring redshift and galaxy properties via a multi-task neural net with probabilistic outputs:an application to simulated MOONS spectra
No full textThe era of large-scale astronomical surveys demands innovative approaches for rapid and accurate analysis of extensive spectral data, and a promising direction in which to address this challenge is offered by machine learning. Here, we introduce a new pipeline, M-TOPnet (Multi-Task network Outputting Probabilities), which employs a convolutional neural network with residual learning to simultaneously derive redshift and other key physical properties of galaxies from their spectra. Our tool efficiently encodes spectral information into a latent space, employing distinct downstream branches for each physical quantity, thereby benefiting from multi-task learning. Notably, our method handles the redshift output as a probability distribution, allowing for a more refined and robust estimation of this critical parameter. We demonstrate preliminary results using simulated data from the MOONS instrument, which will soon be operating at the ESO/VLT. We highlight the effectiveness of our tool in accurately predicting the redshift, stellar mass, and star formation rate of galaxies at z ≳ 1 − 3, even for faint sources (mH ∼ 24) for which traditional methods often struggle. Through analysis of the output probability distributions, we demonstrate that our pipeline enables robust quality screening of the results, achieving accuracy rates of up to 99% in redshift determination (defined as predictions within |Δz|< 0.01 relative to the true redshift) with 8 h exposure spectra, while automatically identifying potentially problematic cases. Our pipeline thus emerges as a powerful solution for the upcoming challenges in observational astronomy, combining precision, interpretability, and efficiency, all aspects that are crucial for analysing the massive datasets expected from next-generation instruments
A Tribute to Mary Eliza Haweis (1848-1898)
No full textA brief tribute to the Victorian writer Mary Eliza Haweis who was an early editor and translator of Chaucer's poetry, a novelist, a writer about fashion and decoration, and an activist for women's emancipation
Exploring the importance of stochasticity to hybrid equilibria in a discrete signaling game
No full textCommunication via evolved signals is ubiquitous (both within and between species) in the natural world. However, how honest we should expect signals to be remains an open question. Hybrid equilibria are a form of equilibria predicted by discrete signaling games in which signalers are sometimes dishonest and signals do not completely reliably convey information on signaler quality. While these equilibria have been theoretically demonstrated in several signaling games, their dynamics in a stochastic simulation of evolutionary trajectories (that include representation of the inherent noise expected in evolution in the natural world) have not previously been studied. In this paper, we present an agent-based simulation of a discrete signaling game which exhibits hybrid equilibria. We find that while hybrid equilibria are evolutionarily attractive where they exist, populations exhibit variable and often drastic oscillating behavior around the predicted equilibrium values. We discuss how these dynamics might offer valuable opportunity for detecting hybrid equilibria in natural populations
Facile, reversible hydrogen activation by low-coordinate magnesium oxide complexes
No full textNew 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
Competing demands on adult children:how do they shape their provision of informal care?
No full textPopulation ageing is increasing the demand for informal care, heightening the importance of adult children as potential carers to their older parents. Adult children, however, may be subject to competing demands for informal care provision when individual characteristics, such as gender and employment status, combine with household level characteristics, such as the presence of young children or vulnerable family members. Previous research often considers these competing demands as separate factors which can influence the provision of informal care, rather than in combination. Therefore, this study exploits data from Wave 13 (2021–2023) of the UK Household Longitudinal Study and applies multicategorical multilevel analysis of individual heterogeneity and discriminatory accuracy (MAIHDA) to assess the additive and interactive role of competing demands in influencing the provision of informal care. The results indicate that the provision of informal care is driven by the additive influence of the competing demands. Moreover, they also reveal the layering of certain social characteristics, which cumulate, rather than intersect, to create a social profile with a notably higher predicted probability of providing informal care
Radii, masses, and transit-timing variations of the three-planet system orbiting the naked-eye star TOI-396
No full textContext. TOI-396 is an F6 V bright naked-eye star (V ≈ 6.4) orbited by three small (Rp ≈ 2 R⊕) transiting planets discovered thanks to space-based photometry from two TESS sectors. The orbital periods of the two innermost planets, namely TOI-396 b and c, are close to the 5:3 commensurability (Pb ~ 3.6 d and Pc ~ 6.0 d), suggesting that the planets might be trapped in a mean motion resonance (MMR).Aims. To measure the masses of the three planets, refine their radii, and investigate whether planets b and c are in MMR, we carried out HARPS radial velocity (RV) observations of TOI-396 and retrieved archival high-precision transit photometry from four TESS sectors.Methods. We extracted the RVs via a skew-normal fit onto the HARPS cross-correlation functions and performed a Markov chain Monte Carlo joint analysis of the Doppler measurements and transit photometry, while employing the breakpoint method to remove stellar activity from the RV time series. We also performed a transit timing variation (TTV) dynamical analysis of the system and simulated the temporal evolution of the TTV amplitudes of the three planets following an N-body numerical integration.Results. Our analysis confirms that the three planets have similar sizes (Rb = 2.004−0.047+0.045 R⊕ ; Rc = 1.979−0.051+0.054 R⊕; Rd = 2.001−0.064+0.063 R⊕) and is thus in agreement with previous findings. However, our measurements are ~ 1.4 times more precise thanks to the use of two additional TESS sectors. For the first time, we have determined the RV masses for TOI-396 b and d, finding them to be Mb = 3.55−0.96+0.94 M⊕ and Md = 7.1 ± 1.6 M⊕, which implies bulk densities of ρb = 2.44−0.68+0.69 g cm−3 and ρd = 4.9−1.1+1.2 g cm−3, respectively. Our results suggest a quite unusual system architecture, with the outermost planet being the densest. Based on a frequency analysis of the HARPS activity indicators and TESS light curves, we find the rotation period of the star to be Prot,⋆ = 6.7 ± 1.3 d, in agreement with the value predicted from log R′HK-based empirical relations. The Doppler reflex motion induced by TOI-396 c remains undetected in our RV time series, likely due to the proximity of the planet’s orbital period to the star’s rotation period. We also discovered that TOI-396 b and c display significant TTVs. While the TTV dynamical analysis returns a formally precise mass for TOI-396 c of Mc,dyn = 2.24−0.67+0.13 M⊕, the result might not be accurate, owing to the poor sampling of the TTV phase. We also conclude that TOI-396 b and c are close to but out of the 5:3 MMR.Conclusions. A TTV dynamical analysis of additional transit photometry evenly covering the TTV phase and super-period is likely the most effective approach for precisely and accurately determining the mass of TOI-396 c. Our numerical simulation suggests TTV semi-amplitudes of up to five hours over a temporal baseline of ~ 5.2 years, which should be duly taken into account when scheduling future observations of TOI-396
Paul Sandby and reproductive printmaking
No full textExplores Sandby's work as "a printmaker using printmaking and reproductive prints as a medium through which to distribute his works to a wider audience ... set into a wider discussion of contemporary attitudes towards reproductive printmaking.