Context. In dense environments, mechanisms such as ram pressure stripping (RPS) and gravitational interactions can induce the formation of similar morphological features in galaxies that are only distinguishable through a detailed study of the stellar properties. While RPS affects recently formed stars through the displacement of the gas disk from which they are formed, gravitational interactions perturb stars in a similar way. Aims. We present the first observational test of the size-shape difference (SSD) measure. This novel approach, which was originally designed and validated for simulated galaxies, quantifies morphological differences between young and intermediate-age stellar populations to distinguish RPS from gravitationally interacting galaxies. Methods. We analyzed 67 galaxies from the GASP survey using spatially resolved star formation history derived from the SINOPSIS spectral fitting code. In our fiducial model, we compared stellar populations in two age bins ( t < 20 Myr and 20 Myr ≤ t < 570 Myr) to calculate SSD values. The sample includes confirmed cases of RPS with different stripping intensities, as well as undisturbed and gravitationally interacting galaxies. Results. We find that the extreme cases of RPS show SSD values ∼3.5× higher than undisturbed and gravitationally interacting galaxies ($ 56^{+24}_{-15} $ as compared to $ 16^{+6}_{-2} $ and $ 16^{+6}_{-3} $, respectively), which confirms simulation predictions. This enhancement reflects RPS-induced asymmetries: the youngest stars are either compressed along the leading edge or displaced into extended tails of cold gas from which they are formed (or both), while older populations remain undisturbed. In contrast, gravitational interactions perturb all stars uniformly, producing lower SSD values. Conclusions. Size-shape difference robustly distinguishes strong RPS cases, even when different age bins are used. This holds even without correcting for disk inclination, or when single-band imaging are used to trace stellar distributions. This makes SSD a promising tool to select RPS candidates for spectroscopic follow-up in upcoming large-scale surveys.

Enabling mixed-precision in spectral element codes

We introduce (M_/M_⊙) ∼ 9 due to the flux-limited nature of Euclid spectroscopic samples, where spectra below the detection threshold lack reliable redshift measurements, preventing effective stacking. The star formation rate–stellar mass relation of the parent sample is recovered reliably only in the deep survey for log_ a versatile spectral stacking pipeline developed for the Euclid mission's NISP spectroscopic surveys, aimed at extracting faint emission lines and spectral features from large galaxy samples in the Wide and Deep Surveys. Designed for computational efficiency and flexible configuration, supports the processing of extensive datasets critical to Euclid's non-cosmological science goals. We validated the pipeline using simulated spectra processed to match Euclid's expected final data quality. Stacking enables robust recovery of key emission lines, including and ∋i, below individual detection limits. However, the measurement of galaxy properties such as star formation rate, dust attenuation, and gas-phase metallicity are biased at stellar mass below log_ 10 10 (M_/M_⊙) ≳ 10, whereas the metallicity–mass relation is recovered more accurately over a wider mass range. These limitations are caused by the increased fraction of redshift measurement errors at lower masses and fluxes. We examined the impact of residual redshift contaminants that arises from mis-identified emission lines and noise spikes, on stacked spectra. Even after stringent quality selections, low-level contamination ($<6%$) has minimal impact on line fluxes due to the systematically weaker emission of contaminants. A percentile-based analysis of stacked spectra provides a sensitive diagnostic for detecting contamination via coherent spurious features at characteristic wavelengths. While our simulations include most instrumental effects, real Euclid data will require a further refinement of contamination mitigation strategies.

Star clusters are valuable indicators of galaxy evolution, offering insights into the buildup of stellar populations across cosmic time. Understanding the intrinsic star cluster populations of dwarf galaxies is particularly important given these systems' role in the hierarchical growth of larger systems. We use data from Euclid's Early Release Observation programme to study star clusters in two star-forming dwarf irregular galaxies in the Local Group, NGC,6822 and IC,10 M_⋆∼ (1--4),times10^8 M_⊙ . With Euclid, star clusters are resolved into individual stars across the main bodies and haloes of both galaxies. Through visual inspection of the data, alongside size measurements and properties derived from the spectral energy distribution fitting code . Through synthetic cluster injection, we conclude our sample is ∼50% complete to M łesssim 10^3 images, we uncover 30 new star cluster candidates in NGC,6822 and 16 in IC,10, ranging from compact to diffuse extended clusters. We compile and re-evaluate previously identified literature candidates, resulting in final combined catalogues of 52 (NGC,6822) and 71 (IC,10) cluster candidates with confidence-based classifications. We present homogeneous photometry in and ̋E, and in archival UBVRI BAGPIPES M _⊙ for ages łesssim100, and to M łesssim 2 _⊙ for ages of ∼10, = 12.4 ± 0.11, ). Using well-defined criteria, we identify 11 candidate GCs in NGC,6822 and nine in IC,10. Both galaxies have high specific frequencies (S_̊m N) for their luminosities but remain consistent with the known GC scaling relationships in the low-luminosity regime. M We find that IC,10 has more young clusters than NGC,6822, and its young clusters extend to higher masses, consistent with its starburst nature. We find several old massive (gtrsim10^5,M_⊙) clusters in both dwarfs, including an exceptional cluster in NGC,6822's outskirts with a mass of 1.3 10^6,M_⊙, nearly twice as massive as any other old cluster in either galaxy. In NGC,6822, we also identify a previously undetected, old, and extended cluster (R_ h pc

Abstract We present an analysis of twenty tidal disruption event (TDE) host galaxies observed with the MUSE integral-field spectrograph on ESO VLT. We investigate the presence of extended emission line regions (EELRs) and study stellar populations mostly at sub-kpc scale around the host nuclei. EELRs are detected in 5/20 hosts, including two unreported systems. All EELRs are found at z < 0.045, suggesting a distance bias and faint EELRs may be missed at higher redshift. EELRs only appear in post-merger systems and all such hosts at z < 0.045 show them. Thus, we conclude that TDEs and galaxy mergers have a strong relation, and >45% of post-merger hosts in the sample exhibit EELRs. Furthermore, we constrained the distributions of stellar masses near the central black holes (BHs), using the spectral synthesis code Starlight and BPASS stellar evolution models. The youngest nuclear populations have typical ages of ∼1 Gyr and stellar masses below 2.5M⊙. The populations that can produce observable TDEs around non-rotating BHs are dominated by subsolar-mass stars. 3/4 TDEs requiring larger stellar masses exhibit multi-peaked light curves, possibly implying relation to repeated partial disruptions of high-mass stars. The found distributions are in tension with the masses of the stars derived using light curve models. Mass segregation of the disrupted stars can enhance the rate of TDEs from supersolar-mass stars but our study implies that low-mass TDEs should still be abundant and even dominate the distribution, unless there is a mechanism that prohibits low-mass TDEs or their detection.

ABSTRACT We present a detailed investigation into the abundance and morphology of high-redshift quenched galaxies at $3 < z < 7$ using James Webb Space Telescope data in the NEP, CEERS, and JADES fields. Within these fields, we identify 90 candidate passive galaxies using specific star formation rates modelled with the BAGPIPES spectral energy distribution fitting code, which is more effective at identifying recently quenched systems than the classical UVJ method, which specializes in quenched objects $>$1 Gyr. With this sample of galaxies, we find number densities broadly consistent with other works and a rapidly evolving passive fraction of high-mass galaxies ($\log _{10}{(M_{\star }/{\rm M}_{\odot })} >$ 9.5) in the range $3 < z < 5$. We find that the fraction of galaxies with low star formation rates and mass 9.5 $ < \log _{10}{(M_{\star }/{\rm M}_{\odot })} <$ 10.5 decreases from $\sim$25 per cent at $3 < z < 4$ to $\sim$2 per cent at $5 < z < 7$. Our passive sample of galaxies is shown to exhibit more compact light profiles compared to star-forming counterparts and some exhibit traces of active galactic nucleus activity through detections in either the X-ray or radio. At the highest redshifts ($z > 6.5$) passive selections start to include examples of ‘little red dots’, which complicates any conclusions until their nature is better understood.

We develop hybrid RANS–LES strategies within the spectral element code Nek5000 based on the k − τ SST turbulence model. We chose airfoil sections with chord-based Reynolds number on the order of 10 5 − 10 6 , in both attached and stalled conditions, as our target problem to comprehensively test the solver accuracy and performance. Verification and validation of the k − τ SST model are performed for two reference cases: for the zero-pressure gradient boundary layer developing on a flat plate and for mild adverse-pressure gradient boundary layers developing on suction side of NACA0012. The k − τ SST model shows good grid convergence characteristics, at par or better in comparison to existing reference results. The results also show good corroboration with existing experimental and numerical datasets for low incoming flow angles. A small discrepancy appears at higher angle in comparison with the experiments, which is in line with our expectations from an RANS formulation. Building on this foundation, we construct a hybrid RANS–LES framework based on the Delayed Detached-Eddy Simulation (DDES) approach. DDES captures both the attached and separated flow dynamics well when compared with available numerical datasets. We demonstrate that for the hybrid approach a high-order spectral element discretization converges faster (i.e. with less resolution) and captures the flow dynamics more accurately than representative low-order approaches. We also revise some of the guidelines on sample size requirements for statistics convergence for massively separated flow within the current numerical framework. Finally, we analyse some of the observed discrepancies of our unconfined DDES at higher angles with the experiments by evaluating the ‘blocking’ effect of wind tunnel walls. We carry out additional simulations for confined domains and assess the observed differences as a function of Reynolds number.

Large spectroscopic surveys aim to consistently compute stellar parameters of very diverse stars, while minimizing systematic errors. We explore the use of stellar clusters as benchmarks to verify the precision of spectroscopic parameters in the fourth data release (DR4) of the GALAH survey. We examine 58 open and globular clusters and associations to validate measurements of temperature, gravity, chemical abundances, and stellar ages. We focus on identifying systematic errors and understanding trends between stellar parameters, particularly temperature and chemical abundances. We identify trends by stacking measurements of chemical abundances against effective temperature and modelling them with splines. We also re-fit spectra in three clusters with the Spectroscopy Made Easy and Korg packages to reproduce the trends in DR4 and to search for their origin by varying temperature and gravity priors, linelists, and the spectral continuum. Trends are consistent between clusters of different ages and metallicities, can reach amplitudes of ~0.5 dex, and differ for dwarfs and giants. We use the derived trends to correct the DR4 abundances of 24 and 31 chemical elements for dwarfs and giants, respectively, and publish a detrended catalogue. While the origin of the trends could not be pinpointed, we found that: (i) photometric priors affect derived abundances, (ii) temperature, metallicity, and continuum levels are degenerate in spectral fitting, and it is hard to break the degeneracy even by using independent measurements, (iii) the completeness of the linelist used in spectral synthesis is essential for cool stars, and (iv) different spectral fitting codes produce significantly different iron abundances for stars of all temperatures. We conclude that clusters can be used to characterise the systematic errors of parameters produced in large surveys, but further research is needed to explain the origin of the trends.

Abstract To investigate spectra of kilonovae in the nonlocal thermal equilibrium phase (t ≳ 1 week), we perform atomic calculations for dielectronic recombination (DR) rates for the light r-process elements Se (Z = 34), Rb (Z = 37), Sr (Z = 38), Y (Z = 39), and Zr (Z = 40) using the HULLAC code. For the different elements, our results for the DR rate coefficients for recombining from the ionization states of II to I, III to II, and IV to III vary between 2 × 10−12–5 × 10−11 cm3 s−1, 10−13–5 × 10−11 cm3 s−1, and 2 × 10−15–10−11 cm3 s−1, respectively, at a temperature of T = 10,000 K. Using this new atomic data (DR), we study the impact on kilonova model spectra at phases of t = 10 days and t = 25 days after the merger using the spectral synthesis code SUMO. Compared to models using the previous treatment of recombination as a constant rate, the new models show significant changes in ionization and temperature, and, correspondingly, in emergent spectra. With the new rates, we find that Zr (Z = 40) plays a yet more dominant role in kilonova spectra for light r-process compositions. Furthermore, we show that previously predicted mid-infrared (e.g., [Se III] 4.55 μm) and optical (e.g., Rb I 7802, 7949 Å) lines weaken in the new model. Instead, [Se I] 5.03 μm emerges as a signature. These results demonstrate the importance of considering the detailed microphysics for modelling and interpreting the late-time kilonova spectra.

Abstract We present the first high-resolution XRISM spectrum of the neutron star low-mass X-ray binary GX 340+0, revealing unprecedented detail in its emission and absorption features. The spectrum reveals a rich and complex Fe xxv Heα line profile and a P Cygni profile from Ca xx. We use the state-of-the-art spectral synthesis code Cloudy to model the emission and absorption features in detail. Our analysis reveals multi-ionization and multivelocity structures, where the combination of broad (∼800 km s−1) and narrow (∼360 km s−1) line components, along with rest-frame and blueshifted emission and absorption lines, accounts for the observed line profile complexity. We identify a modest ∼2735 km s−1 accretion disk wind exhibiting both absorption and emission features. We also detect a relativistic reflection feature in the spectrum, which we model using relxillNS, specifically designed to characterize X-ray reprocessing in accretion disks around neutron stars. Furthermore, we examine the detailed physics of the Fe xxv Heα complex, focusing on the forbidden-to-resonance line ratio under the influence of continuum pumping and optical depth effects.

Abstract We present a comparative test of four widely used full spectral fitting codes, with the aim of answering the question: How robust is the retrieval of the stellar initial mass function (IMF) and other stellar properties of galaxies? We used Absorption Line Fitter (ALF), Python Stellar Absorption Feature Fitting (PyStaff), Starlight, and Penalized PiXel-Fitting (pPXF) to fit a set of optical+near-IR spectroscopic data from the Magellan telescope of the two brightest galaxies in the Fornax cluster, NGC 1399 and NGC 1404. By fitting the same data set with the same models, we can compare the radial trends (out to ∼1 R e ) of IMF slope, age, metallicity, and 19 elemental abundances when allowed with the four codes. To further test the robustness of our analysis, we carried out parallel simulations by creating inputs with different star formation history (SFH) complexity. The results from simulations show that codes such as ALF and PyStaff, which both assume a simple stellar population (SSP), return greater precision and accuracy only when the underlying population is a pure SSP; however, in cases where the SFH is more complex, these codes return erroneous results. Although codes like Starlight and pPXF, which retrieve the best-fit SFH without prior assumptions, tend to produce results with greater scatter and bias, they are generally more reliable in identifying secondary components. Our analysis on the two targets shows that ALF and PyStaff, which assume an SSP, give results pointing to a single old age, a decreasing metallicity with radius, and a flat super-Salpeter IMF. In contrast, Starlight and pPXF suggest the presence of a secondary component with different metallicity and IMF characteristics.

Context. Active galactic nuclei (AGN) stand as extreme X-ray emitters where disk-corona interplay shapes their spectral energy distribution. The soft X-ray excess, a unique feature of AGN in the 0.5 − 2.0 keV, encodes critical information on the “warm corona” structure bridging the disk and hot corona. However, the systematic evolution of this feature with fundamental accretion parameters in large AGN samples – particularly those studied through the spectral stacking technique – remains observationally unconstrained. Aims. The eROSITA All-Sky Survey (eRASS:5) provides an unprecedented sample to statistically map AGN spectral properties. We present a multiwavelength investigation of how the average AGN X-ray spectra evolve with accretion parameters (αox, LUV, λEdd, MBH), and we explore the disk-corona connection by further combining stacked UV data. Methods. We have developed Xstack, a novel X-ray spectral stacking code that consistently stacks rest-frame pulse invariant (PI) spectra and associated responses using optimized response weighting to preserve spectral shapes. With Xstack, we stacked 17 929 AGNs (“spec-z” sample, total exposure ∼23 Ms) with similar X-ray loudness, αox, and UV luminosity, LUV, and 4159 AGNs (“BH-mass” sample, ∼3 Ms) with similar Eddington ratios, λEdd, and black hole masses, MBH. We analyzed the resulting stacked X-ray spectra with a phenomenological model for both samples. We further fit the stacked optical-UV X-ray SED with the physical AGNSED model on a 3 × 3 MBH – λEdd grid. Results. We observed that the soft excess strength rises strongly with increasing αox and λEdd binning (by a factor of five), while the hard X-ray spectral shape remains largely unchanged, consistent with the interpretation that soft excess is primarily driven by the warm corona rather than reflection. The trends are weaker with LUV binning and reversed for MBH binning. The analysis of the optical-UV X-ray SEDs with AGNSED revealed that the warm corona radius (in units of Rg) generally increases with λEdd and decreases with MBH, or equivalently the disk-to-warm-corona transition consistently occurs near ∼1 × 104 K. The hot corona contracts with λEdd, and the radius remains independent of MBH, aligning with disk evaporation predictions. Conclusions. The soft excess is likely warm-corona dominated, with the disk-to-warm-corona transition potentially linked to hydrogen ionization instability at ∼1 × 104 K, which is consistent with previous work utilizing eFEDS-HSC stacked data. Our work highlights the power of spectral stacking for revealing the AGN disk-corona connection.

Context. Dust grains are fundamental components of the interstellar medium (ISM), playing a crucial role in star formation as catalysts for chemical reactions and planetary building blocks. Extinction curves can serve as a tool for characterizing dust properties, however mid-infrared (MIR) extinction remains less constrained in protostellar environments. Gas-phase line ratios from embedded protostellar jets offer a spatially resolved method for measuring the extinction from protostellar envelopes, complementing traditional background starlight techniques. Aims. We aim to derive MIR extinction curves along the lines of sight toward a protostellar jet embedded within an envelope and to assess whether they differ from those inferred from dense molecular clouds. Methods. We analyzed JWST NIRSpec IFU and MIRI MRS observations, focusing on four locations along the blue-shifted TMC1A jet. After extracting observed [Fe II] line intensities, we modeled the intrinsic line ratios using the Cloudy spectral synthesis code across a range of electron densities and temperatures. By comparing observed near-IR (NIR) and MIR line ratios to intrinsic ratios predicted with Cloudy, we were able to infer the relative extinction between the NIR and MIR wavelengths. Results. The electron densities (ne) derived from NIR [Fe II] lines range from ~5 × 104 to ~5 × 103 cm−3 along the jet axis at scales ≲350 AU, serving as reference points for comparing the relative NIR and MIR extinction. The derived MIR extinction results display a higher reddening than empirical dark cloud curves at the corresponding ne values and temperatures (from a few 103 to ~104 K) adopted from shock models. While both the electron density and temperature influence the NIR-to-MIR [Fe II] line ratios, the ratios are more strongly dependent on ne over the adopted range. If the MIR emission originates from gas that is less dense and cooler than the NIR-emitting region, the inferred extinction curves remain consistent with background star-derived values. Conclusions. This study introduces a new line-based method for deriving spatially resolved MIR extinction curves towards embedded protostellar sources exhibiting a bright [Fe II] jet. These results suggest that protostellar envelopes may contain dust with a modified grain size distribution, such as an increased fraction of larger grains (potentially due to grain growth) if the MIR and NIR lines originate from similar regions along the same sight lines. Alternatively, if the grain size distribution has not changed (i.e., there is no grain growth), the MIR lines may trace cooler, less dense gas than the NIR lines along the same sight lines. This method provides a novel approach for studying dust properties in star-forming regions that could be extended to other protostellar systems to refine extinction models in embedded environments.

Abstract The cosmic star formation history (CSFH) and cosmic active galactic nuclei (AGN) luminosity history (CAGNH) are self consistently measured at z = 5.5–13.5. This is achieved by analyzing galaxies detected by the James Webb Space Telescope from ≈ 400 arcmin 2 fields from the Prime Extragalactic Areas of Reionization and Lensing Science, Cosmic Evolution Early Release Science, Next Generation Deep Extragalactic Exploratory Public, JWST Advanced Deep Extragalactic Survey, and Public Release IMaging for Extragalactic Research surveys. In particular, the combination of spectral energy distribution fitting codes, EAZY and ProSpect, is employed to estimate the photometric redshifts and astrophysical quantities of 3751 distant galaxies, from which we compute the stellar mass, star formation rate, and AGN luminosity distribution functions in four redshift bins. Integrating the distribution functions, we find that the CSFH rises by ≈1 dex over z = 13.5–5.5, and the CAGNH rises by ≈1 dex over z = 10.5–5.5. We connect our results of the CSFH and CAGNH at z = 13.5–5.5 to that from z = 5–0 to determine the summary of ≳13 Gyr of star formation and AGN activity, from the very onset of galaxy formation to the present day.

Abstract We introduce a new 1D stellar spectral synthesis Python code called stardis. stardis is a modular, open-source radiative transfer code that is capable of spectral synthesis from near-UV to IR for FGK stars. We describe the structure, inputs, features, underlying physics, and assumptions of stardis, as well as the radiative transfer scheme implemented. To validate our code, we show spectral comparisons between stardis and korg with the same input atmospheric structure models, and we also compare qualitatively to phoenix for solar models. We find that stardis generally agrees with korg for solar models on the few-percent level or better, though the codes can diverge in the UV, with more extreme differences in cooler stars. stardis can be found at https://github.com/tardis-sn/stardis, and documentation can be found at https://tardis-sn.github.io/stardis/.

A potential spectral code for hallucinatory color perception

The r-process production in the early Universe has been well constrained by extensive studies of metal-poor stars. However, the r-process enrichment in the metal-rich regime remains poorly understood. In this study, we examine the abundance ratios of Th and Eu, which represent the actinides and lanthanides, respectively, for a sample of metal-rich disk stars. Our sample covers 89 giant stars in the Kepler field with metallicities −0.7 ≤ [Fe/H] ≤ 0.4 and ages ranging from a few hundred million years to approximately 14 Gyr. Age information for this sample is available from stellar seismology, which is essential for studying the radioactive element Th. We derived Th and Eu abundances through χ2 fitting of high-resolution archival spectra (R ≈ 80 000) obtained with the High Dispersion Spectrograph at the Subaru Telescope. We created synthetic spectra for individual stars using a 1D local thermodynamic equilibrium spectral synthesis code, Turbospectrum, adopting MARCS model atmospheres. Our study establishes the use of a less extensively studied Th II line at 5989 Â, carefully taking into account the blends of other spectral lines to derive the Th abundance. We successfully determine the Eu abundance for 89 stars in our sample and the Th abundance for 81 stars. For the remaining eight stars, we estimate the upper limits of the Th abundance. After correcting the Th abundance for decay, we find no correlation between [Th/Eu] and [Fe/H], which indicates that actinide production with respect to lanthanide production does not depend on metallicity. On the other hand, we find a positive correlation of [Th/Eu] with age, with a slope of 0.10 ± 0.04. This may hint at the possibility that the dominant r-process sources are different between the early and late Universe.

Abstract The critical need to study the magnetic field in the solar corona is highlighted by recent observational facilities, such as the Daniel K. Inouye Solar Telescope and Aditya-L1. A powerful tool for probing the magnetism of the solar corona is forward modeling of the intensity and polarization of coronal emission lines in three-dimensional (3D) magnetohydrodynamic models. Here we present P-CORONA, a new spectral synthesis code designed to calculate the intensity and polarization of coronal lines in 3D models of the solar corona, taking into account the symmetry breaking induced by magnetic and velocity fields. P-CORONA allows the calculation of the on-disk and off-limb intensity and polarization of forbidden and permitted coronal lines, thus facilitating a wide range of investigations. Applying the quantum theory of atom–photon interactions, P-CORONA accounts for the spectral line polarization caused by anisotropic radiation pumping and the Hanle and Zeeman effects, making it a valuable tool for investigating coronal magnetic fields. This paper details the code’s theoretical formulation, implementation, and illustrative results of calculations in different 3D coronal models (MURaM and Predictive Science Inc.), including the impact of the Zeeman effect from the transverse magnetic field component on selected coronal forbidden lines. P-CORONA is now accessible to the research community on GitLab and Zenodo, providing a resource to facilitate research aimed at advancing our understanding of coronal magnetism and dynamics.

Abstract Annular substructures serve as ideal venues for planetesimal formation. In this series, we investigate the linear stage of dust growth within rings. The first paper in this series examines the global streaming instability, while this study focuses on the dusty Rossby wave instability (DRWI). To this end, we perform a linear analysis of the two-fluid equations on a background pressure bump, representing annular substructures. The spectral code Dedalus is used to solve the linear eigenvalue problem. We identify two distinct DRWI modes: Type I, which originates from dust-modified gas RWI, and Type II, which results from dust-gas coupling. Type I and Type II modes never coexist for a given azimuthal wavenumber k y , but transition between each other as k y varies. Type I modes are driven by the advection of background vorticity, and Type II modes possess two waves: Rossby waves, driven by advection, and thin waves, driven by dust-gas drag. Finally, we assess the relevance of DRWI in Atacama Large Millimeter/submillimeter Array (ALMA) rings using DSHARP sources. Our findings suggest that Type I modes could explain the absence of azimuthal asymmetries in many ALMA disks, whereas Type II modes are entirely absent in all eight observed rings, implying that unresolved narrow rings or alternative mechanisms may play a role in dust growth within annular substructures.

Abstract Metal-poor M subdwarfs are among the oldest stellar populations and carry valuable information about the chemical enrichment history of the Milky Way. The measurements of chemical abundances of these stars therefore provide essential insights into the nucleosynthesis in the early stages of the Galaxy’s formation. We present detailed spectroscopic analysis of a nearby metal-poor M subdwarf, LHS 174, from its high-resolution optical spectrum, and apply our previously developed spectral fitting code, AutoSpecFit, to measure the abundances of five elements: [O/H] = −0.519±0.081, [Ca/H] = −0.753 ± 0.177, [Ti/H] = −0.711 ± 0.144, [V/H] = −1.026 ± 0.077, and [Fe/H] = −1.170 ± 0.135. We compare the abundances of O, Ti, and Fe derived from this work and those from previous studies, and demonstrate the observed data are clearly better matched with the synthetic model generated based on our abundances than those from the other analyses. The accuracy of inferred stellar abundances strongly depends on the accuracy of physical parameters, which motivates us to develop a reliable technique to more accurately determine the parameters of low-mass M dwarfs and infer abundances with smaller uncertainties.