arXiv subjects

Mingyu Li

Publications and source records attributed to Mingyu Li.

At least 73 records · Page 4Linked to original sources

arXiv2025

A Metal-Free Galaxy at $z = 3.19$? Evidence of Late Population III Star Formation at Cosmic Noon

Star formation from metal-free gas, the hallmark of the first generation of Population III stars, was long assumed to occur only in the very early Universe. We report the discovery of MPG-CR3 (Metal-Pristine Galaxy COSMOS Redshift 3; hereafter CR3), an extremely metal-poor galaxy at redshift $z= 3.193\pm0.016$. From JWST, VLT, and Subaru observations, CR3 exhibits exceptionally strong Ly$α$, H$α$, and He I $λ$10830 emission. We measure rest-frame equivalent widths of EW$_0$(Ly$α$) $=822\pm101$ Angstrom and EW$_0$(H$α$) $=2814\pm327$ Angstrom, among the highest seen in star-forming systems. No metal lines, e.g. [O III] $λ\lambda4959,5007$, C IV $λ\lambda1548,1550$, have statistically significant detections, placing a 2-$σ$ upper limit on the gas-phase metallicity of 12+log(O/H) < 6.52 ($Z < 7\times10^{-3}\ Z_\odot$) with strong-line calibration established by JWST, making it the most metal-poor galaxy known at cosmic noon. Considering systematic uncertainties of $\gtrsim 0.3$ dex in the calibrations, the most conservative 2-$σ$ upper limit is set to 12+log(O/H) < 6.95. The observed Ly$α$/H$α$ flux ratio is $13.9\pm2.5$, indicating negligible dust attenuation. Spectral energy distribution modeling with Pop III stellar templates indicates a very young ($\sim2$ Myr), low-mass ($M_* \approx 6.1\times 10^5 M_\odot$) stellar population. Further, the photometric redshifts reveal that CR3 could reside in a slightly underdense environment ($δ\approx -0.12$). CR3 provides evidence that first-generation star formation could persist well after the epoch of reionization, challenging the conventional view that pristine star formation ended by $z\gtrsim6$.

astro-ph.GA↗

arXiv2025

Discovery of a Little Red Dot candidate at $z\gtrsim10$ in COSMOS-Web based on MIRI-NIRCam selection

JWST has revealed a new high-redshift population called little red dots (LRDs). Since LRDs may be in the early phase of black hole growth, identifying them in the early universe is crucial for understanding the formation of the first supermassive black holes. However, no robust LRD candidates have been identified at $z>10$, because commonly-used NIRCam photometry covers wavelengths up to $\sim5\,{\rm μm}$ and is insufficient to capture the characteristic V-shaped spectral energy distributions (SEDs) of LRDs. In this study, we present the first search for $z\gtrsim10$ LRD candidates using both NIRCam and MIRI imaging from COSMOS-Web, which provides the largest joint NIRCam-MIRI coverage to date ($0.20\,{\rm deg^2}$). Taking advantage of MIRI/F770W to remove contaminants, we identify one robust candidate, CW-LRD-z10 at $z_{\rm phot}=10.5^{+0.7}_{-0.6}$ with $M_{\rm UV}=-19.9^{+0.1}_{-0.2}\,{\rm mag}$. CW-LRD-z10 exhibits a compact morphology, a distinct V-shaped SED, and a non-detection in F115W, all consistent with being an LRD at $z\sim10$. Based on this discovery, we place the first constraint on the number density of LRDs at $z\sim10$ with $M_{\rm UV}\sim-20$ of $1.2^{+2.7}_{-1.0}\times10^{-6}\,{\rm Mpc^{-3}\,mag^{-1}}$, suggesting that the fraction of LRDs among the overall galaxy population increases with redshift, reaching $\sim3\%$ at $z\sim10$. Although deep spectroscopy is necessary to confirm the redshift and the nature of CW-LRD-z10, our results imply that LRDs may be a common population at $z>10$, playing a key role in the first supermassive black hole formation.

astro-ph.GA↗

arXiv2025

Communications to Circulations: Real-Time 3D Wind Field Prediction Using 5G GNSS Signals and Deep Learning

Accurate atmospheric wind field information is crucial for various applications, including weather forecasting, aviation safety, and disaster risk reduction. However, obtaining high spatiotemporal resolution wind data remains challenging due to limitations in traditional in-situ observations and remote sensing techniques, as well as the computational expense and biases of numerical weather prediction (NWP) models. This paper introduces G-WindCast, a novel deep learning framework that leverages signal strength variations from 5G Global Navigation Satellite System (GNSS) signals to forecast three-dimensional (3D) atmospheric wind fields. The framework utilizes Forward Neural Networks (FNN) and Transformer networks to capture complex, nonlinear, and spatiotemporal relationships between GNSS-derived features and wind dynamics. Our preliminary results demonstrate promising accuracy in real-time wind forecasts (up to 30 minutes lead time). The model exhibits robustness across forecast horizons and different pressure levels, and its predictions for wind fields show superior agreement with ground-based radar wind profiler compared to concurrent European Centre for Medium-Range Weather Forecasts (ECMWF) Reanalysis v5 (ERA5). Furthermore, we show that the system can maintain excellent performance for localized forecasting even with a significantly reduced number of GNSS stations (e.g., around 100), highlighting its cost-effectiveness and scalability. This interdisciplinary approach underscores the transformative potential of exploiting non-traditional data sources and deep learning for advanced environmental monitoring and real-time atmospheric applications.

cs.LG↗

arXiv2025

ProteinAE: Protein Diffusion Autoencoders for Structure Encoding

Developing effective representations of protein structures is essential for advancing protein science, particularly for protein generative modeling. Current approaches often grapple with the complexities of the SE(3) manifold, rely on discrete tokenization, or the need for multiple training objectives, all of which can hinder the model optimization and generalization. We introduce ProteinAE, a novel and streamlined protein diffusion autoencoder designed to overcome these challenges by directly mapping protein backbone coordinates from E(3) into a continuous, compact latent space. ProteinAE employs a non-equivariant Diffusion Transformer with a bottleneck design for efficient compression and is trained end-to-end with a single flow matching objective, substantially simplifying the optimization pipeline. We demonstrate that ProteinAE achieves state-of-the-art reconstruction quality, outperforming existing autoencoders. The resulting latent space serves as a powerful foundation for a latent diffusion model that bypasses the need for explicit equivariance. This enables efficient, high-quality structure generation that is competitive with leading structure-based approaches and significantly outperforms prior latent-based methods. Code is available at https://github.com/OnlyLoveKFC/ProteinAE_v1.

cs.LG↗

arXiv2025

Insights on Metal Enrichment and Environmental Effect at $z\approx5-7$ with JWST ASPIRE/EIGER and Chemical Evolution Model

We present the mass-metallicity relation (MZR) for a parent sample of 604 galaxies at $z=5.34-6.94$ with \OIII\ doublets detected, using the deep JWST/NIRCam wide field slitless spectroscopic (WFSS) observations in 26 quasar fields. The sample incorporates the full observations of 25 quasar fields from the JWST Cycle 1 GO program ASPIRE and the quasar SDSS J0100+2802 from the JWST EIGER program. We identify 204 galaxies residing in overdense structures using the friends-of-friends (FoF) algorithm. We estimate the electron temperature of $2.0^{+0.3}_{-0.4}\times10^4$ K from the Hg and OIII4363 lines in the stacked spectrum, indicating a metal-poor sample with median gas phase metallicity 12+$\log(\mathrm{O/H})=7.65^{+0.26}_{-0.15}$. With the most up-to-date strong line calibration based on NIRSpec observations, we find that the MZR shows a metal enhancement of $\sim0.2$ dex at the high mass end in overdense environments. However, compared to the local Fundamental Metallicity Relation (FMR), our galaxy sample at $z>5$ shows a metal deficiency of $\sim0.2$ dex relative to FMR predictions. We explain the observed trend of FMR with a simple analytical model, favoring dilution from intense gas accretion over outflow to explain the metallicity properties at $z > 5$. Those high-redshift galaxies are likely in a rapid gas accretion phase, during which their metal and gas contents are in a non-equilibrium state. According to model predictions, the protocluster members are closer to the gas equilibrium state than field galaxies and thus have higher metallicity and are closer to the local FMR. Our results suggest that the accelerated star formation during protocluster assembly likely plays a key role in shaping the observed MZR and FMR, indicating a potentially earlier onset of metal enrichment in overdense environments at $z\approx5-7$.

astro-ph.GA↗

arXiv2025

A 13-Billion-Year View of Galaxy Growth: Metallicity Gradient Evolution from the Local Universe to $z=9$ with JWST and Archival Surveys

The galaxy gas-phase metallicity gradients have been extensively studied over the past four decades, both in the local and high-redshift universe, as they trace the baryon cycle and growth of galaxies. With the unprecedented spatial resolution and sensitivity of JWST, it is now possible to measure metallicity and its radial gradients out to redshifts as high as $z = 9$. Here, we present a sample of 455 spectroscopically confirmed galaxies from redshifts $1.7 \lesssim z \lesssim 9$ that are spatially resolved on sub-kiloparsec (kpc) scales by deep JWST NIRCam or NIRISS Wide Field Slitless Spectroscopy (WFSS). Synthesizing these new JWST observations with legacy observations from the literature, we observe that at redshift $z > 5$, galaxy centers are more metal-rich, exhibiting negative metallicity gradients of $\sim-0.4$ dex kpc$^{-1}$. These gradients flatten over time, reaching near-zero around $z \approx 2$, coinciding with the peak of the cosmic star formation rate. Beyond this point, the gradients become negative again at lower redshifts approaching $z=0$. This evolution likely reflects transitions in galaxy formation modes: an inside-out growth phase dominated by intense central star formation with inefficient feedback and limited gas mixing during ``cosmic dawn", enhanced gas mixing due to feedback-driven wind and gas accretion at ``cosmic noon", and a later phase of slow evolution and reduced feedback toward the present day. These physical processes, including gas accretion and feedback, not only regulate star and galaxy formation on a cosmic scale but also shape the evolutionary pathways of individual galaxies over cosmic time.

astro-ph.GA↗

arXiv2025

Discovery of a Pair of Galaxies with Both Hosting X-ray Binary Candidates at $z=2.544$

Among high-redshift galaxies, aside from active galactic nuclei (AGNs), X-ray binaries (XRBs) can be significant sources of X-ray emission. XRBs play a crucial role in galaxy evolution, reflecting the stellar populations of galaxies and regulating star formation through feedback, thereby shaping galaxy structure. In this study, we report a spectroscopically confirmed X-ray emitting galaxy pair (UDF3 and UDF3-2) at $z = 2.544$. By combining multi-wavelength observations from JWST/NIRSpec MSA spectra, JWST/NIRCam and MIRI imaging, Chandra, HST, VLT, ALMA, and VLA, we analyze the ionized emission lines, which are primarily driven by H II region-like processes. Additionally, we find that the mid-infrared radiation can be fully attributed to dust emission from galaxy themselves. Our results indicate that the X-ray emission from these two galaxies is dominated by high-mass XRBs, with luminosities of $L_X= (1.43\pm0.40) \times 10^{42} \, \text{erg} \, \text{s}^{-1}$ for UDF3, and $(0.40\pm0.12) \times 10^{42} \, \text{erg} \, \text{s}^{-1}$ for UDF3-2. Furthermore, we measure the star formation rate (SFR) of $529_{-88}^{+64}$ $M_\odot$ yr$^{-1}$ for UDF3, placing it $\approx$ 0.5 dex below the $L_X$/SFR-$z$ relation. This offset reflects the redshift-dependent enhancement of $L_X$/SFR-$z$ relation, which is influenced by metallicity and serves as a key observable for XRB evolution. In contrast, UDF3-2, with the SFR of $34_{-6}^{+6}$ $M_\odot$ yr$^{-1}$, aligns well with the $L_X$/SFR-$z$ relation. This galaxy pair represents the highest-redshift non-AGN-dominated galaxies with individual X-ray detections reported to date. This finding suggests that the contribution of XRBs to galaxy X-ray emission at high redshift may be underestimated.

astro-ph.GA↗

arXiv2025

Characterization of mini-CryoCube detectors from the Ricochet experiment commissioning at the Institut Laue-Langevin

The Ricochet experiment aims to measure the coherent elastic neutrino-nucleus scattering process from antineutrinos emitted by a research nuclear reactor operated by the Institut Laue-Langevin (Grenoble, France). This article presents a description of the Ricochet experimental installation and the detector performance achieved during its commissioning with a mini-CryoCube module consisting of three 42-gram germanium cryogenic calorimeters. The baseline resolutions and background levels are reported both during reactor-on and reactor-off periods, and as noise mitigation techniques were improved. A baseline resolution of 40 eV electron equivalent was achieved for the ionization channel after setup improvements, and the phonon channel resolutions ranged from 50 to 80 eV of total phonon energy. In the energy region from 2 to 7 keV, a nuclear recoil rate of 15(2) events/(kg day keV) is measured during the reactor-off period selecting events in coincidence with muon veto signals. This rate is in agreement with the cosmogenic neutron rate calculated from GEANT4 simulations. After the rejection of events in coincidence with signals in the muon veto detectors, a combined 90% C.L. limit on the nuclear recoil background of < 9 events/(kg day keV) is obtained in that energy region during the reactor-on period, which is compatible with our GEANT4 model calculation corresponding to a total rate of 5 events/(kg day keV). The sensitivity of this analysis was however found to be limited by a surface event contamination which is currently being addressed by the Ricochet Collaboration with upgraded detectors.

hep-ex↗

arXiv2025

Testing the AGN unified model with simulated emission lines from the circumgalactic medium (CGM)

The CGM around unobscured AGN has received much attention in recent years. Comparatively, nebulae associated with obscured AGN are less studied. Here, we simulate the Ly$α$, H$α$, and HeII nebulae around the two types of AGN at $z=2-3$ with ten massive systems from the FIRE simulations based on the unified model to show their differences and to test if they can be used to constrain the AGN model. We post-process the data with the CLOUDY and the Ly$α$ radiative transfer code, RASCAS. Overall, we find that the Ly$α$ nebulae around the unobscured AGN (type-I nebulae) and obscured AGN (type-II nebulae) do not exhibit significant differences in the luminosity, area, and HeII/Ly$α$ when the simulated cutout is set to the halo virial radius. Whereas, the type-II nebulae exhibit less symmetric morphologies, flatter surface brightness profiles, and larger emission line widths (at $R\geq 10$ kpc) than those of the type-I nebulae. These nebulae properties exhibit complicated correlations with the AGN, indicating that nebulae observations can be applied to constrain the AGN engine. However, independent observations on nebulae in the mentioned emissions are insufficient to test the unified model as a priori in observations is not possible to know the direction and opening angle of the ionization cone. We prompt that the joint observations of Ly$α$ nebulae and radio jets can help to reveal the ionization cone to probe the unified model. Our calculations suggest that this method requires $\geq 75$ type-II Ly$α$ nebulae with current instruments to reach a confidence level of $\geq 95\%$.

astro-ph.GA↗

arXiv2025

A Survey of Context Engineering for Large Language Models

The performance of Large Language Models (LLMs) is fundamentally determined by the contextual information provided during inference. This survey introduces Context Engineering, a formal discipline that transcends simple prompt design to encompass the systematic optimization of information payloads for LLMs. We present a comprehensive taxonomy decomposing Context Engineering into its foundational components and the sophisticated implementations that integrate them into intelligent systems. We first examine the foundational components: context retrieval and generation, context processing and context management. We then explore how these components are architecturally integrated to create sophisticated system implementations: retrieval-augmented generation (RAG), memory systems and tool-integrated reasoning, and multi-agent systems. Through this systematic analysis of over 1400 research papers, our survey not only establishes a technical roadmap for the field but also reveals a critical research gap: a fundamental asymmetry exists between model capabilities. While current models, augmented by advanced context engineering, demonstrate remarkable proficiency in understanding complex contexts, they exhibit pronounced limitations in generating equally sophisticated, long-form outputs. Addressing this gap is a defining priority for future research. Ultimately, this survey provides a unified framework for both researchers and engineers advancing context-aware AI.

cs.CL↗

arXiv2025

Zero-Shot Cyclic Peptide Design via Composable Geometric Constraints

Cyclic peptides, characterized by geometric constraints absent in linear peptides, offer enhanced biochemical properties, presenting new opportunities to address unmet medical needs. However, designing target-specific cyclic peptides remains underexplored due to limited training data. To bridge the gap, we propose CP-Composer, a novel generative framework that enables zero-shot cyclic peptide generation via composable geometric constraints. Our approach decomposes complex cyclization patterns into unit constraints, which are incorporated into a diffusion model through geometric conditioning on nodes and edges. During training, the model learns from unit constraints and their random combinations in linear peptides, while at inference, novel constraint combinations required for cyclization are imposed as input. Experiments show that our model, despite trained with linear peptides, is capable of generating diverse target-binding cyclic peptides, reaching success rates from 38% to 84% on different cyclization strategies.

cs.LG↗

arXiv2025

The Identification of Two JWST/NIRCam-Dark Starburst Galaxies at $z=6.6$ with ALMA

We analyze two dusty star-forming galaxies at $z=6.6$. These galaxies are selected from the ASPIRE survey, a JWST Cycle-1 medium and ALMA Cycle-9 large program targeting 25 quasars and their environments at $z\simeq6.5 - 6.8$. These galaxies are identified as companions to UV-luminous quasars and robustly detected in ALMA continuum and [C II] emission, yet they are extraordinarily faint at the NIRCam wavelengths (down to $>28.0$ AB mag in the F356W band). They are more obscured than galaxies like Arp220, and thus we refer to them as "NIRCam-dark" starburst galaxies (star formation rate $\simeq 80 - 250\,\mathrm{M}_{\odot}\,\mathrm{yr}^{-1}$). Such galaxies are typically missed by (sub)-millimeter blank-field surveys. From the star-formation history (SFH), we show that the NIRCam-dark galaxies are viable progenitors of massive quiescent galaxies at $z\gtrsim4$ and descendants of UV-luminous galaxies at $z>10$. Although it is hard to constrain their number density from a quasar survey, we conclude that NIRCam-dark galaxies can be as abundant as $n\sim10^{-5.5}$ Mpc$^{-3}$ assuming a light halo occupation model. If true, this would equal to $\sim$30% of the number densities of both the quiescent galaxies at $z\gtrsim4$ and UV-luminous galaxies at $z>10$. We further predict that analogs at $z\sim8$ should exist according to the SFH of early massive quiescent galaxies. However, they may fall below the current detection limits of wide JWST and ALMA surveys, thus remaining "JWST-dark". To fully trace the evolution of massive galaxies and dust-obscured cosmic star formation at $z\gtrsim8$, wide-field JWST/NIRCam imaging and slitless spectroscopic surveys of early protoclusters are essential.

astro-ph.GA↗

arXiv2025

Designing Cyclic Peptides via Harmonic SDE with Atom-Bond Modeling

Cyclic peptides offer inherent advantages in pharmaceuticals. For example, cyclic peptides are more resistant to enzymatic hydrolysis compared to linear peptides and usually exhibit excellent stability and affinity. Although deep generative models have achieved great success in linear peptide design, several challenges prevent the development of computational methods for designing diverse types of cyclic peptides. These challenges include the scarcity of 3D structural data on target proteins and associated cyclic peptide ligands, the geometric constraints that cyclization imposes, and the involvement of non-canonical amino acids in cyclization. To address the above challenges, we introduce CpSDE, which consists of two key components: AtomSDE, a generative structure prediction model based on harmonic SDE, and ResRouter, a residue type predictor. Utilizing a routed sampling algorithm that alternates between these two models to iteratively update sequences and structures, CpSDE facilitates the generation of cyclic peptides. By employing explicit all-atom and bond modeling, CpSDE overcomes existing data limitations and is proficient in designing a wide variety of cyclic peptides. Our experimental results demonstrate that the cyclic peptides designed by our method exhibit reliable stability and affinity.

cs.LG↗

arXiv2025

Lyman-Break Galaxies in the Mpc-Scale Environments Around Three $z\sim7.5$ Quasars With JWST Imaging

We study the Mpc-scale environments of the three highest redshift luminous quasars at $z\geq 7.5$ (J031343.84-180636.40, J134208.11+092838.61, and J100758.27+211529.21) to understand their connection to large-scale structure. Cosmological simulations show that these early supermassive black holes (SMBHs) are expected to form in the most massive dark matter halos. Therefore, it is expected that they are anchors of galaxy overdensities if luminous matter traces the underlying dark matter structure of the Universe. Using JWST NIRCam (F090W/F115W/F250M/F360M/F430M) imaging, we observe the large-scale structure out to $\sim13$ comoving Mpc around these quasars. We select F090W-dropout Lyman Break galaxies (LBGs) and F430M-excess [OIII] emitters in the three fields. We find 18, 21, and 6 LBG candidates in the fields of J0313, J1342, and J1007, respectively, resulting in a wide range of overdensities ($1+δ\sim 19,\,24,$ and $7$). The photometric redshifts indicate serendipitous foreground and background overdensities in the J0313 field. The joint angular autocorrelation of the combined LBG sample shows significant clustering on $<1.8$ comoving Mpc scales, demonstrating that the selected galaxies are likely associated with the large-scale structure surrounding the quasars. This first systematic study of $z\sim 7.5$ quasars shows a diverse set of quasar environments at the onset of their formation, providing empirical data to help constrain theoretical predictions of early structure formation.

astro-ph.GA↗

arXiv2025

Deciphering the unique dynamic activation pathway in a G protein-coupled receptor enables unveiling biased signaling and identifying cryptic allosteric sites in conformational intermediates

Neurotensin receptor 1 (NTSR1), a member of the Class A G protein-coupled receptor superfamily, plays an important role in modulating dopaminergic neuronal activity and eliciting opioid-independent analgesia. Recent studies suggest that promoting \{beta}-arrestin-biased signaling in NTSR1 may diminish drugs of abuse, such as psychostimulants, thereby offering a potential avenue for treating human addiction-related disorders. In this study, we utilized a novel computational and experimental approach that combined nudged elastic band-based molecular dynamics simulations, Markov state models, temporal communication network analysis, site-directed mutagenesis, and conformational biosensors, to explore the intricate mechanisms underlying NTSR1 activation and biased signaling. Our study reveals a dynamic stepwise transition mechanism and activated transmission network associated with NTSR1 activation. It also yields valuable insights into the complex interplay between the unique polar network, non-conserved ion locks, and aromatic clusters in NTSR1 signaling. Moreover, we identified a cryptic allosteric site located in the intracellular region of the receptor that exists in an intermediate state within the activation pathway. Collectively, these findings contribute to a more profound understanding of NTSR1 activation and biased signaling at the atomic level, thereby providing a potential strategy for the development of NTSR1 allosteric modulators in the realm of G protein-coupled receptor biology, biophysics, and medicine.

q-bio.BM↗

arXiv2025

PathSeqSAM: Sequential Modeling for Pathology Image Segmentation with SAM2

Current methods for pathology image segmentation typically treat 2D slices independently, ignoring valuable cross-slice information. We present PathSeqSAM, a novel approach that treats 2D pathology slices as sequential video frames using SAM2's memory mechanisms. Our method introduces a distance-aware attention mechanism that accounts for variable physical distances between slices and employs LoRA for domain adaptation. Evaluated on the KPI Challenge 2024 dataset for glomeruli segmentation, PathSeqSAM demonstrates improved segmentation quality, particularly in challenging cases that benefit from cross-slice context. We have publicly released our code at https://github.com/JackyyyWang/PathSeqSAM.

eess.IV↗

arXiv2025

Cosmic Himalayas: The Highest Quasar Density Peak Identified in a 10,000 deg$^2$ Sky with Spatial Discrepancies between Galaxies, Quasars, and IGM HI

We report the identification of a quasar overdensity in the BOSSJ0210 field, dubbed Cosmic Himalayas, consisting of 11 quasars at $z=2.16-2.20$, the densest overdensity of quasars ($17σ$) in the $\sim$10,000 deg$^2$ of the Sloan Digital Sky Survey. We present the spatial distributions of galaxies and quasars and an HI absorption map of the intergalactic medium (IGM). On the map of 465 galaxies selected from the MAMMOTH-Subaru survey, we find two galaxy density peaks that do not fall on the quasar overdensity but instead exist at the northwest and southeast sides, approximately 25 $h^{-1}$ comoving-Mpc apart from the quasar overdensity. With a spatial resolution of 15 $h^{-1}$ comoving Mpc in projection, we produce a three-dimensional HI tomography map by the IGM Ly$α$ forest in the spectra of 23 SDSS/eBOSS quasars behind the quasar overdensity. Surprisingly, the quasar overdensity coincides with neither an absorption peak nor a transmission peak of IGM HI but lies near the border separating opaque and transparent volumes, with the more luminous quasars located in an environment with lesser IGM HI. Hence remarkably, the overdensity region traced by the 11 quasars, albeit all in coherently active states, has no clear coincidence with peaks of galaxies or HI absorption densities. Current physical scenarios with mixtures of HI overdensities and quasar photoionization cannot fully interpret the emergence of Cosmic Himalayas, suggesting this peculiar structure is an excellent laboratory to unveil the interplay between galaxies, quasars, and the IGM.

astro-ph.GA↗

arXiv2025

Medium-band Astrophysics with the Grism of NIRCam In Frontier fields (MAGNIF): Spectroscopic Census of H$α$ Luminosity Functions and Cosmic Star Formation at $z\sim 4.5$ and 6.3

We measure H$α$ luminosity functions (LFs) at redshifts $z \sim 4.5$ and 6.3 using the JWST MAGNIF (Medium-band Astrophysics with the Grism of NIRCam In Frontier fields) survey. MAGNIF obtained NIRCam grism spectra with the F360M and F480M filters in four Frontier Fields. We identify 248 H$α$ emitters based on the grism spectra and photometric redshifts from combined HST and JWST imaging data. The numbers of the H$α$ emitters show a large field-to-field variation, highlighting the necessity of multiple fields to mitigate cosmic variance. We calculate both observed and dust-corrected H$α$ LFs in the two redshift bins. Thanks to the gravitational lensing, the measured H$α$ LFs span three orders of magnitude in luminosity, and the faint-end luminosity reaches $L_{\mathrm{H}α} \sim 10^{40.3} \mathrm{erg} \mathrm{s}^{-1}$ at $z \sim 4.5$ and $10^{41.5} \mathrm{erg} \mathrm{s}^{-1}$ at $z \sim 6.3$, corresponding to star-formation rates (SFRs) of $\sim$ 0.1 and 1.7 $\mathrm{M}_\odot \mathrm{yr}^{-1}$. We conclude no or weak redshift evolution of the faint-end slope of H$α$ LF across $z\simeq0.4-6.3$, and the comparison with the faint-end slopes of UV LF indicates stochastic star formation history among low-mass H$α$ emitters. The derived cosmic SFR densities are $0.058^{+0.008}_{-0.006}\ \ M_\odot\ \mathrm{yr}^{-1}\ \mathrm{Mpc}^{-3}$ at $z \sim 4.5$ and $0.025^{+0.009}_{-0.007}\ \ M_\odot\ \mathrm{yr}^{-1}\ \mathrm{Mpc}^{-3}$ at $z \sim 6.3$. These are approximately 2.2 times higher than previous estimates based on dust-corrected UV LFs, but consistent with recent measurements from infrared surveys. We discuss uncertainties in the H$α$ LF measurements, including those propagate from the lens models, cosmic variance, and AGN contribution.

astro-ph.GA↗