Nitrogen Abundances Research Articles

Full spectroscopic model and trihybrid experimental-perturbative-variational line list for NH

ABSTRACT Imidogen (NH) is a reactive molecule whose presence in astrochemical environments is of interest due to its role in the formation of nitrogen-containing molecules and as a potential probe of nitrogen abundance. Spectroscopic NH monitoring is useful for Earth-based combustion and photolysis processes of ammonia and other nitrogen-containing species. NH is also relevant to ultracold molecular physics and plasma studies. To enable these diverse applications, high-quality molecular spectroscopic data are required. Here, a new line list with significant advantages over existing data is presented. Most notably, this line list models isotopologue spectroscopy and forbidden transitions (important for NH visible absorption), alongside some overall improvements to accuracy and completeness. This approach takes advantage of existing experimental data (from a previous MARVEL compilation) and perturbative line lists together with new MRCI ab initio electronic data. These are used to produce a novel variational spectroscopic model and trihybrid line list for the main 14N1H isotopologue, as well as isotopologue-extrapolated hybrid line lists for the 14N2H, 15N1H, and 15N2H isotopologues. The new 14N1H ExoMol-style trihybrid line list, kNigHt, comprises 4076 energy levels (1078 experimental) and 327 014 transitions up to 47 500 cm−1 (211 nm) between five low-lying electronic states (X 3Σ−, a 1Δ, b 1Σ+, A 3Π, and c 1Π). For most anticipated applications aside from far-infrared studies, this line list will be of sufficient quality; any improvements should focus on the b 1Σ+ energies, and the a 1Δ – A 3Π and b 1Σ+ – A 3Π spin–orbit couplings.

Assessing the role of non-native species and artificial water bodies on the trophic and functional niche of Mediterranean freshwater fish communities

Habitat alterations and the introduction of non-native species have many ecological impacts, including the loss of biodiversity and a deterioration of ecosystem functioning. The effects of these combined stressors on the community trophic web and functional niche are, however, not completely clear. Here, we investigated how artificial ecosystems (i.e. reservoirs) and non-native species may influence the trophic and functional niche space of freshwater fish communities. To do so, we used carbon and nitrogen stable isotope and abundance data to compute a set of isotopic, trait, and functional metrics for 13 fish communities sampled from 12 distinct ecosystems in Türkiye. We show that in reservoirs, fish were more similar in their trophic niche compared to lakes, where the trophic niche was more variable, due to higher habitat complexity. However, there were no differences in the trait and functional metrics between the two ecosystem types, suggesting a higher prey diversity than assumed in reservoirs. We also found that the number of non-native species did not affect the trophic niche space, nor the trait or functional space occupied by the fish community. This indicates that non-native species tended to overlap their trophic niche with native species, while occupying empty functional niches in the recipient community functional space. Similarly, the proportion of non-native species did not affect any trophic, trait, or functional metric, suggesting that changes in community composition were not reflected in changes in the community niche space. Moreover, we found that trait richness, but not functional richness, was positively related to the isotopic niche width and diversity, indicating that a wider occupied trait niche space corresponded with a wider occupied trophic niche and lesser interspecific similarity. Our findings underscore the complexity of ecological relationships within freshwater ecosystems and highlight the need for comprehensive management strategies to mitigate the impacts of human activities and biological invasions.

Characteristics of Epiphytic Bacterial Community on Submerged Macrophytes in Water Environment Supplemented with Reclaimed Water

Biofilms attached to submerged macrophytes play an important role in improving the water quality of the water environment supplemented with reclaimed water. In order to explore the effects of reclaimed water quality and submerged macrophyte species on the characteristics of an epiphytic bacterial community, different types of submerged macrophytes were selected as research objects in this study. 16S rRNA high-throughput sequencing technology was used on the epiphytic bacteria and the surrounding environmental samples to analyze the bacterial community structure and functional genes. The results showed that approximately 20%-35% of the nitrogen and phosphorus nutrients were absorbed and utilized in the water environment supplemented with reclaimed water. However, the COD, turbidity, and chroma of the downstream water were significantly increased. The bacterial community of the biofilms attached to submerged macrophytes was significantly different from that in the surrounding environment (soil, sediment, and water body) and in the activated sludge that was treated by reclaimed water. In terms of bacterial community diversity, the richness and diversity were significantly lower than those of soil and sediment but higher than those of plankton bacteria in water. In terms of bacterial community composition, dominant genera and corresponding abundances were also different from those of other samples. The main dominant bacterial genera were Sphingomonas, Aeromonas, Pseudomonas, and Acinetobacter, accounting for 7%-40%, respectively. Both macrophyte species and the quality of reclaimed water (BOD5, TN, NH4+-N, and TP) could affect the bacterial community. However, the effect of water quality of the bacterial community was greater than that of macrophytes species. Additionally, the quality of reclaimed water also affected the abundance of functional genes in the bacterial community, and the relative abundance of nitrogen and phosphorus cycling functional genes was higher in areas with higher nitrogen and phosphorus concentrations.

The origin and evolution of Earth's nitrogen.

Nitrogen is a vital element for life on Earth. Its cycling between the surface (atmosphere+crust) and the mantle has a profound influence on the atmosphere and climate. However, our understanding of the origin and evolution of Earth's nitrogen is still incomplete. This review presents an overview of the current understanding of Earth's nitrogen budget and the isotope composition of different reservoirs, laboratory constraints on deep nitrogen geochemistry, and our understanding of the origin of Earth's nitrogen and the deep nitrogen cycle through plate subduction and volcanism. The Earth may have acquired its nitrogen heterogeneously during the main accretion phase, initially from reduced, enstatite-chondrite-like impactors, and subsequently from increasingly oxidized impactors and minimal CI-chondrite-like materials. Like Earth's surface, the mantle and core are also significant nitrogen reservoirs. The nitrogen abundance and isotope composition of these three reservoirs may have been fundamentally established during the main accretion phase and have been insignificantly modified afterwards by the deep nitrogen cycle, although there is a net nitrogen ingassing into Earth's mantle in modern subduction zones. However, it is estimated that the early atmosphere of Earth may have contained ∼1.4 times the present-day atmospheric nitrogen (PAN), with ∼0.4 PAN being sequestered into the crust via biotic nitrogen fixation. In order to gain a better understanding of the origin and evolution of Earth's nitrogen, directions for future research are suggested.

Chemical abundances of LINER galaxies – nitrogen abundance estimations

ABSTRACT In this work, we investigated the nitrogen and oxygen abundances in a sample of galaxies with Low Ionization Nuclear Emission Regions (LINERs) in their nucleus. Optical spectroscopic data (3600 – 10 000 Å) of 40 LINERs from the Mapping Nearby Galaxies (MaNGAs) survey were considered. Only objects classified as retired galaxies, that is, whose main ionization sources are post-Asymptotic Giant Branch (pAGB) stars, were selected. The abundance estimates were obtained through detailed photoionization models built with the cloudy code to reproduce a set of observational emission line intensities ratios of the sample. Our results show that LINERs have oxygen and nitrogen abundances in the ranges of $\rm 8.0 \: \lesssim \: 12+\log (O/H) \: \lesssim \: 9.0$ (mean value 8.74 ± 0.27) and $\rm 7.6 \: \lesssim \: 12+\log (N/H) \: \lesssim \: 8.5$ (mean value 8.05 ± 0.25), respectively. About 70 per cent of the sample have oversolar O/H and N/H abundances. Our abundance estimates are in consonance with those for Seyfert 2 nuclei and H ii regions with the highest metallicity, indicating that these distinct object classes show similar enrichment of the interstellar medium (ISM). The LINERs in our sample are located in the higher N/O region of the N/O versus O/H diagram, showing an unexpected negative correlation between these two parameters. These results suggest that these LINERs mainly exhibit a secondary nitrogen production and could be acting some other mechanisms that deviate them from the usual theoretical secondary nitrogen production curve and the H ii regions observations. However, we did not find any evidence in our data able to support the literature suggested mechanisms. Alternatively, our results show that LINERs do not present any correlation between the N/O abundances and the stellar masses of the hosting galaxies.

X-Shooting ULLYSES: Massive stars at low metallicity. V. Effect of metallicity on surface abundances of O stars

Massive stars rotate faster, on average, than lower mass stars. Stellar rotation triggers hydrodynamical instabilities which transport angular momentum and chemical species from the core to the surface. Models of high-mass stars that include these processes predict that chemical mixing is stronger at lower metallicity. We aim to test this prediction by comparing the surface abundances of massive stars at different metallicities. We performed a spectroscopic analysis of single O stars in the Magellanic Clouds (MCs) based on the ULLYSES and XshootU surveys. We determined the fundamental parameters and helium, carbon, nitrogen, and oxygen surface abundances of 17 LMC and 17 SMC non-supergiant O6-9.5 stars. We complemented these determinations by literature results for additional MCs and also Galactic stars to increase the sample size and metallicity coverage. We investigated the differences in the surface chemical enrichment at different metallicities and compared them with predictions of three sets of evolutionary models. Surface abundances are consistent with CNO-cycle nucleosynthesis. The maximum surface nitrogen enrichment is stronger in MC stars than in Galactic stars. Nitrogen enrichment is also observed in stars with higher surface gravities in the SMC than in the Galaxy. This trend is predicted by models that incorporate chemical transport caused by stellar rotation. The distributions of projected rotational velocities in our samples are likely biased towards slow rotators. A metallicity dependence of surface abundances is demonstrated. The analysis of larger samples with an unbiased distribution of projected rotational velocities is required to better constrain the treatment of chemical mixing and angular momentum transport in massive single and binary stars.

Chemical abundances and deviations from the solar S/O ratio in the gas-phase interstellar medium of galaxies based on infrared emission lines

Context. The infrared (IR) range is extremely useful in the context of chemical abundance studies of the gas-phase interstellar medium (ISM) due to the large variety of ionic species traced in this regime, the negligible effects from dust attenuation or temperature stratification, and the amount of data that has been and will be released in the coming years. Aims. Taking advantage of available IR emission lines, we analysed the chemical content of the gas-phase ISM in a sample of 131 star-forming galaxies (SFGs) and 73 active galactic nuclei (AGNs). In particular, we derived the chemical content via their total oxygen abundance in combination with nitrogen and sulphur abundances, and with the ionisation parameter. Methods. We used a new version of the code HII-CHI-MISTRY-IR v3.1, which allowed us to estimate log(N/O), 12+log(O/H), log(U) and, for the first time, 12+log(S/H) from IR emission lines, which can be applied to both SFGs and AGNs. We tested whether the estimates from this new version, which only considers sulphur lines for the derivation of sulphur abundances, are compatible with previous studies. Results. While most of the SFGs and AGNs show solar log(N/O) abundances, we find a large spread in the log(S/O) relative abundances. Specifically, we find extremely low log(S/O) values (1/10 solar) in some SFGs and AGNs with solar-like oxygen abundances. This result warns against the use of optical and IR sulphur emission lines to estimate oxygen abundances when no prior estimation of log(S/O) is provided.

Assessing the feasibility of laser induced breakdown spectroscopy for detecting nitrogen in martian surface sediments

Despite the detection of fixed nitrogen in meteorites and directly on Mars' surface, the abundance and distribution of nitrogen sequestered in the martian crust remains unknown. Given that nitrogen is a bioessential element that is required for the synthesis of amino acids, nucleic acids, and other organic molecules vital for life, this gap in knowledge is one of the most important challenges in constraining martian habitability. Laser-induced breakdown spectroscopy (LIBS) has the capability to detect N in natural rock samples and is available as a stand-off survey instrument on multiple currently active Mars rovers, creating an immediate opportunity to map the stratigraphic distribution of N within diverse depositional settings. However, little has been published regarding the detection of N with LIBS.To lay a foundation for N detection on Mars using LIBS, we synthesized a comprehensive suite of samples with variable amounts of nitrogen (as nitrate or ammonium) in either a Mars regolith simulant or a clay matrix. We present baseline spectra of N emission in Mars-relevant matrices and identify spectral interferences. Our results indicate that 17 diagnostic N emission lines are reliably detectable from mineral-bound N against a basaltic background, but only four lines exhibit sufficient sensitivity to be detected across a range of N concentrations and within all tested matrices. To elucidate optimized strategies for quantification, we present an iterative series of PLS models. We find that prediction accuracy is improved by restricting the compositional range of the training set, normalizing the data, subtracting baseline continuum emission, and simultaneously modeling the emission behaviour of multiple diagnostic N lines at once. We observe that the prediction uncertainty increases (worsens) from 8.4% to 29.9% if models are used to predict N in samples with a dissimilar matrix than those used during training, suggesting poor generalizability outside the training range. Consequently, future work should focus on developing a larger, more diverse training set that encompasses the range of N concentrations and phases expected to be encountered on Mars, which may be used to train generalizable models. Overall, this work demonstrates that LIBS is a promising tool for determining the abundance of N sequestered in martian surface materials and lays a foundation for future development.

Effects of combined microplastic and cadmium pollution on sorghum growth, Cd accumulation, and rhizosphere microbial functions

The interaction between microplastics (MPs) and cadmium (Cd) poses a threat to agricultural soil environments, and their effects on plant growth and rhizosphere microbial community functions are not yet clear. In this study, energy sorghum was used as a test plant to investigate the effects of two types of MPs, polystyrene (PS) and polyethylene (PE), at different particle sizes (13 μm, 550 μm) and concentrations (0.1%, 1% w/w), and Cd, as well as their interactions, on the growth of sorghum in a soil-cultivation pot experiment. The results showed that the combined effects of MP and Cd pollution on the dry weight and Cd accumulation rate in sorghum varied depending on the type, concentration, and particle size of the MPs, with an overall trend of increasing stress from combined pollution with increasing Cd content and accumulation. High-throughput sequencing analysis revealed that combined MP and Cd pollution increased bacterial diversity, and the most significant increase was observed in the abundance-based coverage estimator (ACE), Shannon, and Sobs indices in the 13 μm 1% PS+Cd treatment group. Metagenomic analysis based on the Kyoto Encyclopedia of Genes and Genomes (KEGG) metabolic pathways revealed that 19 groups of metabolic pathways, including microbial metabolism and methane metabolism, differed significantly under combined MP and Cd pollution. Hierarchical clustering results indicated that Cd treatment and combined MP and Cd treatment affected the abundances of sorghum rhizosphere soil nitrogen (N) and phosphorus (P) cycling genes and that the type of MP present was an important factor affecting N and P cycling genes. The results of this study provide a basis for exploring the toxic effects of combined MP and Cd pollution and for conducting soil environmental risk assessments.

Dual‐Shelled Hollow Leafy Carbon Support with Atomically Dispersed (N,S)‐Bridged Hydroxy‐Coordinated Asymmetric Fe Sites for Oxygen Reduction

AbstractSingle‐atom catalysts (SACs) are widely studied in various chemical transformations due to their high catalytic activity and atom utilization. However, modulating the catalytic performance of catalysts by adjusting the microenvironment remains a great challenge. In this paper, a novel master‐double guest vulcanization‐assisted strategy is reported for synthesizing Fe single‐atom catalysts on N,S codoped porous hollow leaf carbon (FeSA/N,S‐PHLC) with highly exposed FeN3SOH sites. Fe(mIm) (guest I) is loaded on the surface of ZIF‐L (host) and then trithiocyanuric acid (TCA, guest II) is bonded with Fe(mIm), and the resulting ZIF‐L@Fe(mIm)@TCA precursors can be converted to FeSA/N,S‐PHLC with controllable structures. In addition, XPS analysis yield an increase in pyridine N content in FeSA/N,S‐PHLC compared to FeSA/N‐PHLC. It can be demonstrated by theoretical calculations that the N,S‐coordinated axially hydroxy‐coordinated asymmetric Fe centers synergistically with the abundance of pyridinic nitrogen facilitate the adsorption and desorption of oxygen intermediates, and the 3d orbitals of the Fe active centers can be optimized. The prepared FeSA/N,S‐PHLC catalyst has a half‐wave potential (E1/2) of 0.91 V under alkaline conditions, and E1/2 = 0.75 V under acidic conditions. It shows excellent cycle stability (882 h) and power density (217 mW cm−2) in the assembly of zinc–air battery (ZABs) devices.

Microbial diversity and keystone species drive soil nutrient cycling and multifunctionality following mangrove restoration

Vegetation restoration exerts transformative effects on nutrient cycling, microbial communities, and ecosystem functions. While extensive research has been conducted on the significance of mangroves and their restoration efforts, the effectiveness of mangrove restoration in enhancing soil multifunctionality in degraded coastal wetlands remains unclear. Herein, we carried out a field experiment to explore the impacts of mangrove restoration and its chronosequence on soil microbial communities, keystone species, and soil multifunctionality, using unrestored aquaculture ponds as controls. The results revealed that mangrove restoration enhanced soil multifunctionality, with these positive effects progressively amplifying over the restoration chronosequence. Furthermore, mangrove restoration led to a substantial increase in microbial diversity and a reshaping of microbial community composition, increasing the relative abundance of dominant phyla such as Nitrospirae, Deferribacteres, and Fusobacteria. Soil multifunctionality exhibited positive correlations with microbial diversity, suggesting a link between variations in microbial diversity and soil multifunctionality. Metagenomic screening demonstrated that mangrove restoration resulted in a simultaneous increase in the abundance of nitrogen (N) related genes, such as N fixation (nirD/H/K), nitrification (pmoA-amoA/B/C), and denitrification (nirK, norB/C, narG/H, napA/B), as well as phosphorus (P)-related genes, including organic P mineralization (phnX/W, phoA/D/G, phnJ/N/P), inorganic P solubilization (gcd, ppx-gppA), and transporters (phnC/D/E, pstA/B/C/S)). The relationship between the abundance of keystone species (such as phnC/D/E) and restoration-induced changes in soil multifunctionality indicates that mangrove restoration enhances soil multifunctionality through an increase in the abundance of keystone species associated with N and P cycles. Additionally, it was observed that changes in microbial community and multifunctionality were largely associated with shifts in soil salinity. These findings demonstrate that mangrove restoration positively influences soil multifunctionality and shapes nutrient dynamics, microbial communities, and overall ecosystem resilience. As global efforts continue to focus on ecosystem restoration, understanding the complexity of mangrove-soil interactions is critical for effective nutrient management and mangrove conservation.

Explaining the high nitrogen abundances observed in high-z galaxies via population III stars of a few thousand solar masses

The chemical enrichment of the early Universe is a crucial element in the formation and evolution of galaxies, and Population III (Pop III) stars must play a vital role in this process. In this study, we examine metal enrichment from massive stars in the early Universe’s embryonic galaxies. Using radiation hydrodynamic simulations and stellar evolution modelling, we calculated the expected metal yield from these stars. Specifically, we applied accretion rates from a previous radiation-hydrodynamic simulation to inform our stellar evolution modelling, executed with the Geneva code, across 11 selected datasets, with final stellar masses between 500 and 9000 M⊙. Our results demonstrate that the first generation of Pop III stars within a mass range of 2000−9000 M⊙ result in N/O, C/O and O/H ratios compatible with the values observed in very high-z galaxies GN-z11 and CEERS 1019. The ejecta of these Pop III stars are predominantly composed of 4He, 1H, and 14N. Our Pop III chemical enrichment model of the halo can accurately reproduce the observed N/O and C/O ratios, and, by incorporating a hundred times more zero-metallicity interstellar material with the stellar ejecta, it accurately attains the observed O/H ratio. Thus, a sub-population of extremely massive Pop III stars, with masses surpassing approximately 2000 M⊙, effectively reproduces the CNO elemental abundances observed in high-z JWST galaxies to date. We closely reproduced the observed Ne/O ratio in CEERS 1019 employing a model with several thousand solar masses and non-zero metallicity, and we projected a 12C/13C ratio of 7, substantially lower than the solar ratio of around 90. The significant nitrogen enrichment predicted by Pop III stars with a few thousand solar masses not only reinforces the argument for a heavy seed formation pathway for massive black holes at redshifts as high as z = 10.6 but it also accentuates the need for deeper investigations into their complex nature and pivotal role in the early Universe.

He-rich Hot Subdwarf Stars Observed in Gaia DR3 and LAMOST DR7: Carbon and Nitrogen Abundances and Kinematics

We conducted an analysis of the abundances of He, C, and N in 210 He-rich hot subdwarfs observed within both the Gaia Data Release 3 (DR3) and LAMOST DR7 data sets. This analysis involved fitting the LAMOST spectra with Tlusty/Synspec non-LTE synthetic spectra. By examining the Galactic spatial positions, velocity vectors, and orbital parameters of these stars, we determined their Galactic population memberships utilizing LAMOST radial velocities and Gaia DR3 parallaxes along with proper motions. Our investigation revealed two positive correlations of C and one positive correlation of N with respect to the He abundance. We found a clear C abundance dichotomy where approximately 82% of the stars show N enrichment above the solar value. Moreover, we observed a bimodal distribution of C abundances, prominently evident in both the Galactic thin and thick disks but absent in the halo population. Furthermore, we found that the scenario of the merger channel of double helium white dwarfs is inadequate to explain the formation of C-deficient He-rich hot subdwarfs.

Probing the optical and molecular properties of sedimentary dissolved organic matter in the laminated diatom mats from the southern Mariana Trench

Laminated diatom mats (LDMs) deposition, formed by the aggregation of giant diatoms (e.g., Ethmodiscus rex), are recognized as a crucial driver of the global carbon and silicon cycles due to their substantial contribution to the flux of organic carbon and biogenic silica. The biogenic silica-rich sediment is one of the typical sediment types in the deep-sea setting of the tropical Pacific Ocean. Here, we analyzed the concentrations of pore-water dissolved organic carbon (DOC) and phosphate (PO43−), the optical properties, and molecular compositions of dissolved organic matter (DOM) in the two LDMs cores and one non-LDMs core retrieved from the southern Mariana Trench. Our results showed that the LDMs sediments with higher total organic carbon (TOC) contents have lower concentrations of DOC and chromophoric dissolved organic matter (CDOM), compared to the non-LDMs core. Meanwhile, the LDMs samples exhibited lower relative intensity of fluorescent proteins-like, molecular lability boundary (MLBL%) and higher values for humification index (HIX) and aromaticity modification (AImod) compared to the non-LDM core, indicating a higher level of stability and recalcitrance of DOM likely resulting from microbial degradation of relatively labile DOM compounds. Furthermore, the LDMs samples were characterized by a high abundance of CHO-containing DOM components and a low abundance of nitrogen- and sulfur-containing components, potentially linked to microbial degradation of hydrocarbon compounds that were enriched in the LDMs sediments. Additionally, the unique formulas in the LDMs samples demonstrated higher degree of recalcitrance suggested by higher aromaticity and fraction of CRAM, which may be attributed to microbial transformation of DOM. These findings add to our limited knowledge of the optical properties and molecular composition of DOM in the deep-sea opal-rich sediments, and have implications for understanding DOM cycling in the deep oceans.

Rapid Chemical Enrichment by Intermittent Star Formation in GN-z11

We interpret the peculiar supersolar nitrogen abundance recently reported by the James Webb Space Telescope observations for GN-z11 (z = 10.6) using our state-of-the-art chemical evolution models. The observed CNO ratios can be successfully reproduced—independently of the adopted initial mass function, nucleosynthesis yields, and presence of supermassive (>1000M ⊙) stars—if the galaxy has undergone an intermittent star formation history with a quiescent phase lasting ∼100 Myr, separating two strong starbursts. Immediately after the second burst, Wolf–Rayet stars (up to 120M ⊙) become the dominant enrichment source, also temporarily (<1 Myr) enhancing particular elements (N, F, Na, and Al) and isotopes (13C and 18O). Alternative explanations involving (i) single burst models, also including very massive stars and/or pair-instability supernovae, or (ii) pre-enrichment scenarios fail to match the data. Feedback-regulated, intermittent star formation might be common in early systems. Elemental abundances can be used to test this hypothesis and to get new insights on nuclear and stellar astrophysics.

Two sequences of spiral galaxies with different shapes of the metallicity gradients

We considered two sequences of spiral galaxies with different shapes of the radial gas-phase oxygen abundance distributions from the galaxies in the survey Mapping Nearby Galaxies at Apache Point Observatory (MaNGA): (1) Galaxies in which the gradient is well approximated by a single linear relation across the whole disc, that is, galaxies with an S (slope) gradients, (2) galaxies in which the metallicity in the inner region of the disc is at a nearly constant level and the gradient is negative at larger radii, that is, galaxies with level-slope (LS) gradients. We also selected galaxies with a nearly uniform oxygen abundance across the whole galaxy, that is, galaxies with level (L) gradients (or O/H uniform galaxies) with a high oxygen abundance that can be the final evolutionary stage of the two galaxy sequences described above. The radial nitrogen abundance distributions in galaxies with LS oxygen abundance distributions also show breaks at radii smaller than the O/H distribution breaks. The observed behaviour of the oxygen and nitrogen abundances with radius in these galaxies can be explained by the time delay between the nitrogen and oxygen enrichment together with the variation in the star formation history along the radius. These galaxies clearly show the effect of the inside-out disc evolution model, which predicts that the galactic centre evolves more rapidly than the regions at greater galactocentric distances. We find that the shape of the radial abundance distribution in a galaxy is not related to its macroscopic characteristics (rotation velocity, stellar mass, isophotal radius, and star formation rate) and is independent of its present-day environment. The correlations between the gradient slopes and macroscopic characteristics of galaxies are weak in the sense that the scatter of the points in each diagram is large. The galaxies with different abundance distributions (S, LS, or L) in our sample are located within the main sequence of the star-forming galaxies in the diagram of star formation rate–stellar mass. We also examined the properties of the Milky Way in the context of the considered galaxy samples.

A Comparative Study between M30 and M92: M92 is a Merger Remnant with a Large Helium Enhancement

We perform a comparative study of the ex situ second-parameter pair globular clusters (GCs) M30 and M92, having similar metallicities but different horizontal branch morphologies. We obtain similar mean primordial carbon abundances for both clusters. However, M92 shows a large dispersion in carbon due to a more extended C–N anticorrelation, while M30 exhibits a higher primordial nitrogen abundance, suggesting that they have different chemical enrichment histories. Our new results confirm our previous result that M92 is a metal-complex GC showing a bimodal metallicity distribution. We also find that the metal-rich group of stars in M92 shows a helium enhancement as large as ΔY ∼ 0.05 from the red giant branch bump V magnitudes, which can also be supported by (i) a lack of bright red giant branch stars, (ii) synthetic evolutionary horizontal branch population models and (iii) the more extended spatial distribution due to different degree of the diffusion process from their lower masses. We reinterpret the [Eu/Fe] measurements by others, finding that the two metallicity groups of stars in M92 have significantly different [Eu/Fe] abundances with small scatters. This strongly suggests that they formed independently out of well-mixed interstellar media in different environments. We suggest that M92 is a more complex system than a normal GC, most likely a merger remnant of two GCs or an even more complex system. In the Appendix, we address the problems with the recently developed color–temperature relations and the usage of broadband photometry in the populational taggings.

Spectroscopic Distance, Mass, and Age Estimations for APOGEE DR17

We derive distances and masses of stars from the Sloan Digital Sky Survey (SDSS) Apache Point Observatory Galactic Evolution Experiment Data Release 17 using simple neural networks. Training data for distances comes from Gaia EDR3, supplemented by literature distances for star clusters. For masses, the network is trained using asteroseismic masses for evolved stars and isochrone masses for main-sequence stars. The models are trained on effective temperature, surface gravity, metallicity, and carbon and nitrogen abundances. We found that our distance predictions have median fractional errors that range from ≈20% at low log g and ≈10% at higher log g with a standard deviation of ≈11%. The mass predictions have a standard deviation of ±12%. Using the masses, we derive ages for evolved stars based on the correspondence between mass and age for giant stars given by isochrones. The results are compiled into a Value Added Catalog called DistMass that contains distances and masses for 733,901 independent spectra, plus ages for 396,548 evolved stars.

A small and vigorous black hole in the early Universe

Several theories have been proposed to describe the formation of black hole seeds in the early Universe and to explain the emergence of very massive black holes observed in the first thousand million years after the Big Bang1–3. Models consider different seeding and accretion scenarios4–7, which require the detection and characterization of black holes in the first few hundred million years after the Big Bang to be validated. Here we present an extensive analysis of the JWST-NIRSpec spectrum of GN-z11, an exceptionally luminous galaxy at z = 10.6, revealing the detection of the [Neiv]λ2423 and CII*λ1335 transitions (typical of active galactic nuclei), as well as semi-forbidden nebular lines tracing gas densities higher than 109 cm−3, typical of the broad line region of active galactic nuclei. These spectral features indicate that GN-z11 hosts an accreting black hole. The spectrum also reveals a deep and blueshifted CIVλ1549 absorption trough, tracing an outflow with velocity 800−1,000 km s−1, probably driven by the active galactic nucleus. Assuming local virial relations, we derive a black hole mass of log(MBH/M⊙)=6.2±0.3\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\log ({M}_{{\\rm{BH}}}/{M}_{\\odot })=6.2\\pm 0.3$$\\end{document}, accreting at about five times the Eddington rate. These properties are consistent with both heavy seeds scenarios and scenarios considering intermediate and light seeds experiencing episodic super-Eddington phases. Our finding explains the high luminosity of GN-z11 and can also provide an explanation for its exceptionally high nitrogen abundance.

Estimating the heritability of nitrogen and carbon isotopes in the tail hair of beef cattle

BackgroundThe natural abundance of nitrogen (δ15N) and carbon (δ13C) isotopes in animal tissues are used to estimate an animal’s efficiency in nitrogen utilization, and their feed conversion efficiency, especially in tropical grazing systems with prolonged protein restriction. It is postulated that selection for improving these two characteristics (δ15N and δ13C) would assist the optimisation of the adaptation in ever-changing environments, particularly in response to climate change. The aim of this study was to determine the heritability of δ15N and δ13C in the tail hair of tropically adapted beef cattle to validate their inclusion in genetic breeding programs.MethodsIn total, 492 steers from two breeds, Brahman (n = 268) and Droughtmaster (n = 224) were used in this study. These steers were managed in two mixed breed contemporary groups across two years (year of weaning): steers weaned in 2019 (n = 250) and 2020 (n = 242). Samples of tail switch hair representing hair segments grown during the dry season were collected and analysed for δ15N and δ13C with isotope-ratio mass spectrometry. Heritability and variance components were estimated in a univariate multibreed (and single breed) animal model in WOMBAT and ASReml using three generations of full pedigree.ResultsThe estimated heritability of both traits was significantly different from 0, i.e. 0.43 ± 0.14 and 0.41 ± 0.15 for δ15N and δ13C, respectively. These traits had favourable moderate to high genetic and phenotypic correlations (− 0.78 ± 0.16 and − 0.40 ± 0.04, respectively). The study also provides informative single-breed results in spite of the limited sample size, with estimated heritability values of 0.37 ± 0.19 and 0.19 ± 0.17 for δ15N and δ13C in Brahman, and 0.36 ± 0.21 and 0.46 ± 0.22 for δ15N and δ13C in Droughtmaster, respectively.ConclusionsThe findings of this study show, for the first time, that the natural abundances of both nitrogen and carbon isotopes in the tail hair in cattle may be moderately heritable. With further research and validation, tail hair isotopes can become a practical tool for the large-scale selection of more efficient cattle.