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First constraints on the local ionization topology in front of two quasars at z ∼ 7.5
No full textThus far, Lyman-α damping wings towards quasars have been used to probe the global ionization state of the foreground intergalactic medium (IGM). A new parametrization has demonstrated that the damping wing signature also carries local information about the distribution of neutral hydrogen (H I) in front of the quasar before it started shining. Leveraging a recently introduced Bayesian JAX-based Hamiltonian Monte Carlo inference framework, we derive constraints on the Lorentzian-weighted H I column density NDW H I , the quasar’s distance rpatch to the first neutral patch, and its lifetime tQ based on James Webb Space
Telescope (JWST) Near Infrared Spectrograph (NIRSpec) spectra of the two z ∼ 7.5 quasars J1007+2115 and J1342+0928. After folding in model-dependent topology information, we find that J1007+2115 (and J1342+0928) is most likely to reside in a (xH1)= 0.32+0.22 −0.20 (0.58+0.23 −0.23) neutral IGM while shining for a remarkably short lifetime of log10 tQ/yr = 4.14+0.74 −0.18 (an intermediate lifetime of 5.64+0.25 −0.43) along a sightline with log10 NDW
H I /cm−2 = 19.70+0.35 −0.86 (20.24+0.25 −0.22) and rpatch = 28.9+54.0 −14.4 cMpc
(10.9+5.6−5.9 cMpc). In light of the potential presence of local absorbers in the foreground of J1342+0928 as has been recently suggested, we also demonstrate how the Lorentzian-weighted column density NDW H I provides a natural means for quantifying their contribution to the observed damping wing signal
Odd-Ramsey numbers of complete bipartite graphs
No full textIn his study of graph codes, Alon introduced the concept of the odd-Ramsey number of a family of graphs H in Kn, defined as the minimum number of colours needed to colour the edges of K so that every copy of a graph H E H intersects some colour class in an odd number of edges. In this paper, we focus on complete bipartite graphs. First, we completely resolve the problem when H is the family of all spanning complete bipartite graphs on n vertices. We then focus on its subfamilies, that is, {Kt,n-t : t E T} for a fixed set of integers T c [[n/2]]. We prove that the odd-Ramsey problem is equivalent to determining the maximum dimension of a linear binary code avoiding codewords of given weights, and leverage known results from coding theory to deduce asymptotically tight bounds in our setting. We conclude with bounds for the odd-Ramsey numbers of fixed (that is, non-spanning) complete bipartite subgraphs
Research Data for 'Causes and consequences of sex-chromosome turnovers in Diptera'
No full textSex-chromosome systems are highly variable across animals, but how they transition from one to another is not well understood. Diptera have undergone multiple sex-chromosome turnovers and expansions while maintaining their general chromosomal content, which makes them an ideal clade to study such transitions. We analysed more than 100 dipteran whole-genome assemblies and identified 4 new lineages that underwent sex-chromosome turnover (in addition to the 5 previously reported). We find the majority of turnovers happened in the group Schizophora, which tend to have fewer genes on the F element (the chromosome homologous to the ancestral insect X chromosome) than lower dipterans, a factor previously hypothesized to facilitate turnover. Most derived X chromosomes have higher GC content than autosomes, consistent with a high prevalence of male-achiasmy in Diptera. In addition, an excess of gene movement out of the X is detected for most of these new X chromosomes, and many of these moved genes have high testis expression in Drosophila, suggesting that out-of-X gene movement contributes to the long-term demasculinization of X chromosomes
Glacier-atmosphere interactions and feedbacks in high-mountain regions - A review
No full textMountain glaciers are among the natural systems most vulnerable to climate change. However, their interactions with the atmosphere are complex and not fully understood. These interactions can trigger rapid adjustments and climate feedbacks that either amplify or attenuate atmospheric signals, influencing both glacier response and large-scale atmospheric circulation. Observing this functional coupling in nature is challenging because the key processes occur over a wide range of spatial and temporal scales. However, recent advances in observational techniques and modeling have provided new insights into these interactions. In this review, we summarize the current state of knowledge on glacier-atmosphere interactions in high-mountain regions at different scales, and highlight recent advances in observational and numerical modeling. We also highlight important knowledge gaps and outline future research directions to improve the prediction of glacier change in a warming world