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The MeerKAT Absorption Line Survey (MALS) data release 3: Cold atomic gas associated with the Milky Way
No full textInternational audienceAims . We present results of a blind search for Galactic H I 21-cm absorption lines toward 19 130 radio sources brighter than 1 mJy at 1.4 GHz, using 390 pointings of the MeerKAT Absorption Line Survey (MALS), each pointing centered on a source brighter than 200 mJy. The spectral resolution, the median spatial resolution, and the median 3 σ optical depth sensitivity ( τ 3 σ ) are 5.5 km s −1 , ~ 9″, and 0.381, respectively. We used the spectra of the central sources and the other off-axis radio sources within the telescope pointings to constrain the properties of H I gas in the local interstellar medium (LISM) of the Galaxy. Methods . Through an automated procedure, we detected 3640 H I absorption features over ~800 deg 2 . This represents the largest Galactic H I absorption line catalog to date. We used H I 21-cm emission line measurements from HI4PI, an all sky single-dish survey, and far-infrared maps from COBE/DIRBE and IRAS/ISSA in addition to the Gaussian decomposition of the HI4PI into cold (CNM), lukewarm (LNM), and warm (WNM) neutral medium phases for our analyses. Results . We find a strong linear correlation with a coefficient of 0.84 between the H I 21-cm emission line column densities ( N HI ) and the visual extinction ( A V ) measured toward the pointing center, along with the confinement of the absorption features to a narrow range in radial velocities (−25< v LSR [km s −1 ]<+25). This implies that the detected absorption lines form a homogeneous sample of H I clouds in the LISM. For central sight lines (median τ 3 σ =0.008), the detection rate is 82±5%. All the central MALS sight lines with H I absorption have N HI (CNM) + N HI (LNM) ≥ N HI (WNM). The H I 21-cm absorption optical depth is linearly correlated to N HI and A V , with a correlation coefficient in excess of 0.8 up to N HI ≃ 2 · 10 21 cm −2 or, equivalently, A V ≃ 1 mag. Above this threshold, A V traces the total hydrogen content, and consequently, A V and the single-dish N HI scale, differently. The slopes of N HI distributions of central sight lines with H I 21-cm absorption detections and non-detection differ at >2 σ . A similar difference is observed for H 2 detections and non-detections in damped Lyman-alpha systems at z ≳1.8, implying that turbulence-driven WNM-to-CNM conversion is the common governing factor for the presence of H I 21-cm and H 2 absorption. Through a comparison of central and off-axis absorption features, we find the optical depth variations (Δ τ ) to be higher for pointings centered on regions with a higher N HI and CNM fraction. However, no such dependence is observed for the covering fraction of the absorbing structures over 0.1–10 pc. The slope (2.327 ± 0.153) of root mean square (rms) fluctuations in optical depth variations in the quiescent gas associated with LISM is shallower than the earlier measurements in the disk. The densities (20–30 cm −3 ) inferred from |Δ τ | at the median separation (1.5 pc) of the sample are typical of the CNM values. The negligible (median ~0 km s −1 ) velocity shifts between central and off-axis absorbers are in line with the hypothesis that the CNM/LNM clouds freeze out of the extended WNM phase
Interactions of the LINE-1 encoded ORF1p with proteins and chromatin converge on a role in neuronal physiology
No full textInternational audienceRetrotransposons are emerging as novel regulators of embryonic and brain development. We recently demonstrated that the LINE-1–encoded protein ORF1p is abundantly expressed in adult mouse and human neurons, although its function remains unclear. Here, we characterize the ORF1p interactome in differentiated mouse and human neurons using mass spectrometry and identify novel partners implicated in gene regulation and neuron-specific processes. ORF1p localizes not only to neuronal nuclei, where it associates with chromatin under steady-state conditions, but also to neurites, supporting a role in neuronal physiology. To further explore its nuclear functions, we sorted human post-mortem neurons with high or low nuclear ORF1p levels and performed ORF1p knockdown in cultured human neurons, followed by chromatin accessibility assays. Both approaches revealed consistent patterns of differential chromatin accessibility dependent on ORF1p. Loss of ORF1p also led to the downregulation of long, neuron-specific genes and altered neurite morphology. Together, these findings point to a physiological role of ORF1p in post-mitotic neurons, mediated through converging interactions with proteins and chromatin
Ecological responses of planktonic foraminifera and pteropods to sapropel formation in the eastern Mediterranean Sea
No full textInternational audienceThe Mediterranean Sea, a semi-enclosed basin, has experienced periodic anoxic events that resulted in sapropels—organic-rich sediment layers formed during deep-water oxygen depletion. While the main processes driving sapropel formation are understood, the ecological and morphological responses of planktonic species to these extreme conditions remain largely unexplored. This study aims to fill this gap by examining the composition, tolerance, and ecological responses of calcareous planktonic species, with a focus on planktonic foraminifera Globigerinoides ruber morphotypes and pteropod populations across sapropel formation events. To investigate these responses, we analyzed one sediment core retrieved from the Gulf of Sirte, covering the last 130 k years with a focus on sapropels S1 and S5. Microfossil samples were investigated using a microfossil sorter (MiSo) Robot at CEREGE, which automatically images and measures microfossils from the coarse sediment fraction, unlike conventional approaches, which focus on species abundance and identification solely. This approach allowed us to determine both abundance and size of the different specimens, at the species level, through the training of a Convolutional Neural Network (CNN) which was applied to label a large dataset (160,000 images). Our results reveal significant shifts in planktonic community composition and diversity throughout the sapropels S1 and S5. Planktonic foraminifera diversity decreased during sapropels, notably with a reduction in species like Globigerinoides ruber and Globigerinoides elongatus. In contrast, pteropod abundance increased, suggesting they may be more resilient to environmental changes due to their higher motility compared to foraminifera and lower species competition during these anoxic periods. Size variations in dominant species were also observed, with distinct changes linked to environmental stressors such as lower salinity. This study provides valuable insights into the resilience and adaptability of planktonic species environmental changes, offering a more refined understanding of sapropel-related ecological impacts on marine communities
Aligning individual brains with Fused Unbalanced Gromov-Wasserstein
No full textIndividual brains vary in both anatomy and functional organization, even within a given species. Inter-individual variability is a major impediment when trying to draw generalizable conclusions from neuroimaging data collected on groups of subjects. Current co-registration procedures rely on limited data, and thus lead to very coarse inter-subject alignments. In this work, we present a novel method for inter-subject alignment based on Optimal Transport, denoted as Fused Unbalanced Gromov Wasserstein (FUGW). The method aligns cortical surfaces based on the similarity of their functional signatures in response to a variety of stimulation settings, while penalizing large deformations of individual topographic organization. We demonstrate that FUGW is well-suited for whole-brain landmark-free alignment. The unbalanced feature allows to deal with the fact that functional areas vary in size across subjects. Our results show that FUGW alignment significantly increases between-subject correlation of activity for independent functional data, and leads to more precise mapping at the group level
Inactualité de l'aliénation pour l'écologie politique
No full textInternational audienceIl y a dans la matrice de l'écologie politique contemporaine, en particulier française, une importance très grande du concept d'aliénation Une alienation qui n'est plus simplement une alienation par le travail comme chez Marx et d'une alienation qu'on peut définir comme une alienation par rapport à l'économie par rapport à une sphère spécifique de la pratique humaine qui est la sphère économique D'où une tendance de l'écologie politique à se penser comme post-économique ou au-delà des déterminations d'une société économique. Cette aliénation par rapport à l'économie suggère une relation particulière et critique de l'écologie politique aux concepts du discours économique, au concept que le discours économique met en circulation, et qui permet justement de penser cette pratique économique. ce que je voudrais tenter d'expliquer c'est sur quel genre de pensée économique et quel genre de conception de l'économie, du fonctionnement de l'économie cette utilisation du concept d'aliénation se base pour montrer ensuite que par certains côtés elle consiste à ignorer la dimension proprement économique et essayer de tracer ce qui est moins souvent fait, une autre histoire de l'écologie politique, justement plus soucieuse du fonctionnement économique
Barry Commoner : économie socio-métabolique et écologie politique
No full textInternational audienceCe texte s’inscrit dans histoire politique des tentatives écologiques de matérialiser l’économie depuis la fin des années 60. Ce qui m’intéresse ces d’identifier les prises en charge politique de la question écologique s’appuient sur des savoirs et en particulier des savoirs économiques ou des contestations du savoir économique. Autrement dit, je cherche à relier des choix épistémologique et des tendances politiques.Un aspect de ces tentatives de matérialisation des questions économiques est le rapprochement entre science économique et écologie scientifique. Dans les années 70, Des écologues étendent leurs questionnements aux problématiques économiques pour réfléchir sur la crise environnementale et en tire des conséquences politiques, notamment démographiques. Ce branchement est clé dans la constitution d’un environnementalisme américain très marqué par le malthusianisme. La biologisation des sciences sociales à laquelle contribue l’extension du domaine de l’écologie scientifique nourrit ainsi dans l’Amérique des années 1970 – une écologie politique réactionnaire . Ainsin c'’est en s’appuyant sur sa formation d’écologue que Hardin a pu écrire son article célèbre « Pourquoi il ne faut pas aider les pauvres ». Selon lui, en effet, « ceux qui soutiennent [l’] effort humanitaire bien intentionné [de lutter contre la faim dans le monde] devraient d'abord considérer certains fondamentaux de l'écologie humaine. Alan Gregg comparait la croissance et l'expansion de l'humanité à la surface de la terre à la propagation d'un cancer dans le corps humain, faisant remarquer que "les tumeurs cancéreuses réclament de la nourriture ; mais, pour autant que je sache, on ne les a jamais guéries en leur en donnant." ».La question qui m’intéresse est de savoir si cette connexion entre écologie scientifique et écologie politique réactionnaire est une connexion nécessaire. Ou s’il y a d’autres branchements possibles et comment se font-ils ? Pour étudier un contrepoint, je m’intéresse à Barry Commoner. Qui est un exemple d’articulation entre les prémices de l’économie écologique (en ce qu’il nourrit la pensée économique d’écologie et de thermodynamique) et une écologie politique socialiste. Pour le présenter en 2 mots : Biologiste mais aussi candidat à l’élection présidentielle de 1980, ses livres sont d’abord ceux d’un lanceur d’alerte et d’un scientifique engagé mais il se distingue par l’ambition théorique de son propos qui essaie de fournir un cadre unifié pour comprendre la crise multiforme que subit l’économie américaine au tournant des années 1970.Commoner réussit à tenir une analyse écoénergétique de l’économie sans verser dans le réductionnisme. Pour lui, l’environnement dans lequel prend place l’activité économique possède des véritables caractéristiques matérielles et écologiques sans pour autant que cela fasse disparaître le niveau institutionnel et social. Et il fait en se tenant sur une ligne de crête entre économie écologique (au sens de Daly et Georgescu-Roegen) et socio-économie (au sens de Kapp). C’est cette ligne de crête que je voudrais décrire en soulignant qu’elle est à la fois épistémologique et politique. Pour le dire très vite : -Il faut se tenir entre le fait de ne faire de l’économie qu’une sous-partie de l’écologie scientifique ce qui la naturaliserait excessivement et le fait de n’en faire qu’une science sociale ce qui la conduirait à négliger les dynamiques matérielles, énergétiques et écologiques à l’œuvre dans la crise environnementale. -De même pour penser une écologie politique, il faut se tenir entre la négation du politique qu’induirait une naturalisation excessive des catégories économiques et une négation de l’écologie qu’induirait une compréhension de l’économie fondée sur les seuls rapports sociaux de productio
NIKA2 Cosmological Legacy Survey. Blind detection of galaxy clusters in the COSMOS field via the Sunyaev-Zel’dovich effect
No full textInternational audienceClusters of galaxies, formed in the latest stages of structure formation, are unique cosmological probes. With the advent of large CMB surveys like those from the Planck satellite, the ACT and SPT telescopes, we now have access to a large number of galaxy clusters detected at millimeter wavelengths via the thermal Sunyaev-Zel’dovich (tSZ) effect. Nevertheless, it is interesting to complement them with high-angular-resolution (tens of arcseconds) observations to target the lowest-mass and highest-redshift clusters. This is the case of observations with the NIKA2 camera, which is installed on the IRAM 30-m telescope in Pico Veleta, Spain. We used the existing 150 GHz (2 mm) data from the NIKA2 Cosmological Legacy Survey (N2CLS) Large Program to blindly search for galaxy clusters in the well-known COSMOS field, across a 877 arcmin2 region centered on (RA, Dec)J2000 = (10h00m28.81s, +02d17m30.44s). We first developed a dedicated data reduction pipeline to construct NIKA2 maps at 2 mm. We then used a matched-filter algorithm to extract cluster candidates assuming a universal pressure profile to model the expected cluster tSZ signal. We computed the purity and completeness of the sample by applying the previous algorithm to simulated maps of the sky signal in the COSMOS field, including tSZ contribution, point sources and instrumental noise. We find a total of 16 cluster candidates at S/N > 4, from which eight have either an optical or X-ray cluster (or group of galaxies) counterpart. This is the first blind detection of clusters of galaxies at mm wavelengths at 18″ angular resolution. For candidates with available redshift estimates, we derived their mass by modeling the cluster tSZ signal with a universal pressure profile via a MCMC analysis. From this analysis, we confirm that NIKA2 and the IRAM 30-m telescope should be sensitive to low-mass clusters at intermediate and high redshift, complementing current and planned large tSZ-based cluster surveys
Quasar radiation transforms the gas in a merging companion galaxy
No full textInternational audienceQuasars, powered by gas accretion onto supermassive black holes1,2, rank among the most energetic objects in the Universe3,4. Although they are thought to be ignited by galaxy mergers5, 6, 7, 8, 9, 10–11 and affect the surrounding gas12, 13, 14–15, observational constraints on both processes remain scarce16, 17–18. Here we describe a major merging system at redshift z ≈ 2.7 and demonstrate that radiation from the quasar in one galaxy directly alters the gas properties in the other galaxy. Our findings reveal that the galaxies, with centroids separated by only a few kiloparsecs and approaching each other at a speed of approximately 550 km s‑1, are massive, are forming stars and contain a substantial molecular mass. Yet, dusty molecular gas seen in absorption against the quasar nucleus is highly excited and confined within cloudlets with densities of approximately 105 to 106 cm‑3 and sizes of less than 0.02 pc, several orders of magnitude more compact than those observed in intervening (non-quasar) environments. This is also approximately 105 times smaller than currently resolvable through molecular-line emission at high redshifts. We infer that, wherever it is exposed to the quasar radiation, the molecular gas is disrupted, leaving behind surviving dense clouds too small to give birth to new stars. Our results not only underscore the role of major galaxy mergers in triggering quasar activity but also reveal localized negative feedback as a profound alteration of the internal gas structure, which probably hampers star formation
Taxonomic revision of the SK 15 mandible based on bone and tooth structural organization
No full textInternational audienceThe hominin mandible SK 15 was discovered in April 1949 in Swartkrans Member 2, dated to ∼1.4 Ma. Albeit distorted on the right side, the left and right corpus of SK 15 are relatively low and thick, even compared to most Early to Middle Pleistocene Homo specimens. It preserves the left molar row and the right M2 and M3 that show a distalward increase in mesiodistal diameter. SK 15 was originally attributed to Telanthropus capensis but is now generally attributed to Homo erectus/Homo ergaster, even if it was previously suggested to possibly belong to Australopithecus. Similarities between SK 15 and Homo naledi mandible and tooth morphology were also claimed. To clarify the taxonomy of SK 15, we used X-ray microtomography to investigate aspects of bone and tooth structural organization. Geometric morphometric analyses of the dental arcade shape, mandible symphysis outline, and the M2 and M3 enamel-dentine junction shape were conducted. For mandibular symphysis shape, SK 15 exhibits an australopith signal, whereas for both the dental arcade and enamel-dentine junction analyses, the specimen is statistically classified as Paranthropus. Altogether, the results show that SK 15 unambiguously falls outside the variation of H. erectus/H. ergaster and that it is most compatible with the morphology of Paranthropus, albeit showing smaller dimensions and an absence of some dental morphological features (e.g., developed protostylid, distally tapering M3, short molar roots) typically found in specimens of Paranthropus aethiopicus, Paranthropus boisei, and Paranthropus robustus. In particular, SK 15 differs markedly in size and morphology from mandibular remains of P. robustus from Swartkrans Member 2. We thus tentatively attribute SK 15 to Paranthropus capensis, a more gracile species of Paranthropus than the other three currently recognized species of this genus and discuss the implications for the existence of another species of Paranthropus in southern Africa during the Early Pleistocene