arXiv subjects

Takahiro Morishita

Publications and source records attributed to Takahiro Morishita.

At least 37 records · Page 2Linked to original sources

arXiv2026

The BoRG-$JWST$ Survey: Analogs at $z\sim8$ to the UV-luminous Galaxy Population at $z\gtrsim10$

The population of bright galaxies at $z\gtrsim10$ discovered by JWST, including the so-called "blue monsters", has been difficult to reconcile with standard galaxy evolution models. To shed light on this extraordinary population, we study the $z\sim8$ galaxies discovered by the BoRG-$JWST$ survey. These slightly-lower redshift analogs are comparable in UV luminosity to the blue monsters, and their lower redshift makes it much easier to access key rest frame optical diagnostics with NIRspec. We find that BoRG-$JWST$ galaxies are consistent with being dust-poor based on their blue UV slopes and Balmer decrement ratios. We find no strong evidence for dominant active galactic nuclei contribution to the UV brightness, based on line-ratio diagnostics, though some contribution cannot be excluded. We further infer the stellar mass, star formation and UV-brightness history of the BoRG-$JWST$ galaxies by fitting their rest-frame UV-optical spectra. We see evidence for stochastic episodes of star formation for all the BoRG-$JWST$ galaxies, providing a temporal boosting of UV luminosity in short timescales. The UV-bright blue monsters at $z\gtrsim10$ can be explained by the presence of stars with ages below 100 Myr.

astro-ph.GA↗

arXiv2026

TDCOSMO XXIV. First spatially resolved kinematics of the lens galaxy obtained using JWST-NIRSpec to improve time-delay cosmography

Spatially resolved stellar kinematics has become a key ingredient in time-delay cosmography to break the mass-sheet degeneracy in the mass profile and in turn provide a precise constraint on the Hubble constant and other cosmological parameters. In this paper, we present the first measurements of 2D resolved stellar kinematics for the lens galaxy in the quadruply lensed quasar system RXJ1131$-$1231 using integral field spectroscopy from JWST's Near-Infrared Spectrograph (NIRSpec), marking the first such measurement conducted with JWST. In extracting robust kinematic measurements from this first-of-its-kind dataset, we have made methodological improvements both in the data reduction and kinematic extraction. In our kinematic extraction procedure, we performed joint modeling of the lens galaxy, the quasar, and its host galaxy's contributions in the spectra to deblend the lens galaxy component and robustly constrain its stellar kinematics. Our improved methodological frameworks are released as software pipelines for future use: squirrel, for extracting stellar kinematics, and RegalJumper, for JWST-NIRSpec data reduction. We incorporated additional artifact cleaning beyond the standard JWST pipeline. We compared our measured stellar kinematics from the JWST NIRSpec with previously obtained ground-based measurements from the Keck Cosmic Web Imager integral field unit and find that the two datasets are statistically consistent at a $\sim$1.1$σ$ confidence level. Our measured kinematics will be used in a future study to improve the precision of the Hubble constant measurement.

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arXiv2026

A Nitrogen-rich AGN Powering a Large Ionizing Bubble at z=8.63

We report the detection of Ly$α$ in CANUCS-LRD-z8.6, a recently discovered AGN at z = 8.63 by Tripodi et al. (2024), in new NIRSpec/MSA G140H/F070LP observations. We detect broad Ly$α$ emission (FWHM $= 1540 \pm 260$ km/s) near the systemic velocity, which suggests a large ionizing bubble considering that the universe is almost fully neutral at the redshift. Through Ly$α$ line-shape modeling assuming a Stromgren sphere, we find a large bubble radius, $R_b = 1.5^{+0.3}_{-0.2}$ pMpc, and a moderately high Ly$α$ escape fraction, $f_{esc} = 11 \pm 3$ %. The intrinsic line width is inferred to be broad ($2200 \pm 280$ km/s), likely originating in the broad-line region. Existing data indicate that CANUCS-LRD-z8.6 is within a mild overdensity, $δ= 1.8^{+3.0}_{-0.6}$, suggesting that other galaxies in its proximity might have contributed to the formation of the bubble. The high N IV]$λ$1488 / C IV$λ$1548 and N IV]$λ$1488 / O III]$λ$1661 line ratios measured in existing NIRSpec/PRISM data indicate nitrogen enrichment in this metal-poor, low-luminosity AGN. The spectroscopic features are overall similar to other nitrogen-rich galaxies discovered in the literature, such as GN-z11 and GHZ2/GLASSz12. This suggests that CANUCS-LRD-z8.6 may represent one of the evolutionary phases of those nitrogen-rich galaxies.

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arXiv2026

Beyond UV: Rest-frame B-band and Apparent Luminosity Functions of z=5-9 Galaxies

We present new measurements of galaxy luminosity functions (LFs) from JWST/NIRCam imaging over the redshift range z=4.5-9.7, using photometric catalogs from JADES and public extragalactic fields. Our analysis includes rest-frame UV and B-band LFs, as well as apparent LFs in F090W, F115W, F200W, F356W, and F444W. We present the first constraints on the rest-frame B-band LF at z~7-8 and extend existing measurements at z~5 to M(B) = -18 mag. The B-band LFs evolve more strongly with redshift than UV LFs, though both decline more gradually than predicted by simulations at z>5. No single existing simulation reproduces all observed trends, with discrepancies likely driven by assumptions about binary evolution and stellar population synthesis models. The apparent LFs in F356W and F444W show hints of a bright-end excess at all redshifts, extending to fainter magnitudes at higher redshift. While extreme emission line galaxies may partially account for it, the excess may also indicate a population of moderately red, optically bright sources - potentially dusty star-forming galaxies or obscured AGNs. Finally, we find that rest-frame B-band luminosity correlates more tightly with stellar mass than UV, making it a powerful tracer of mass assembly and reinforcing the diagnostic value of rest-frame optical LFs in uncovering the physical processes that drive early galaxy formation.

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arXiv2026

BEACON: JWST NIRCam Pure-parallel Imaging Survey. II. Physical Properties of $z=7-14$ Galaxies

We present photometric properties of 161 galaxy candidates at $z=7-14$ selected from the second data release (DR2) of BEACON, a JWST Cycle 2 pure-parallel NIRCam imaging program. Carefully selected from 36 independent pointings (corresponding to $\sim350$\,arcmin$^2$ sky coverage), and hence with reduced cosmic variance, our galaxy candidates provide an unbiased sample for investigating galaxy properties over a wide range of environments. We measure the physical properties, including UV continuum slope ($β_{\rm UV}$), stellar mass ($M_*$), star formation rate (SFR), and sizes. Our highest redshift galaxy candidate at $z=13.71\pm0.15$ has a remarkably bright UV luminosity of $M_{\rm UV}=-21.19\pm0.08$, making it the brightest galaxy at $z>12$ if spectroscopically confirmed. With an extremely blue UV slope, compact morphology, and high star formation rate surface density ($Σ_{\rm SFR}$), this candidate may have extremely low metallicity, high ionizing photon escape fraction, or contributions from an AGN. Among our multiple independent sightlines, we identify three fields of galaxy number overdensity with $>3σ$ significance. The properties of galaxies in various environments do not exhibit significant differences, implying either that accelerated galaxy evolution in overdense regions is not yet widespread at $z>7$, or that the current constraints are limited by sample size. Our simulations indicate that increasing the sample by an order of magnitude would allow such environmental trends to be robustly confirmed or ruled out, underscoring the importance of future pure-parallel observations.

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arXiv2026

Characterizing Dust Extinction and Spatially Resolved Paschen-$α$ Emission within 97 Galaxies at $1<z<1.6$ with JWST NIRCam Slitless Spectroscopy

We present results on the Paschen-$α$ (Pa$α$) emitting galaxies observed as part of the JWST FRESCO survey in the GOODS-North and GOODS-South fields. Utilizing the JWST NIRCam wide field slitless spectroscopy (WFSS), we analyze emission line fluxes, star formation rates (SFRs), and spatially resolved flux distributions of 97 Pa$α$ emitters at $1<z<1.6$. To assess dust extinction within our sample, we combine Pa$α$ fluxes with archival H$α$ data taken with the Hubble Space Telescope (HST) WFC3 G141 grism. Our analysis reveals a significant correlation between dust extinction and galaxy stellar mass, where more massive galaxies exhibit greater dust extinction. We employ two-dimensional Pa$α$ and F444W mapping to trace the distributions of star formation and stellar mass, respectively. Our observations indicate that lower mass galaxies are almost dust free in Pa$α$ and exhibit smaller sizes both in star formation and underlying stellar continuum. In contrast, galaxies with a stellar mass greater than $10^{9.5}M_\odot$ display diverse dust extinction and star formation patterns. This variation suggests that the structures and properties of massive galaxies evolve through different phases, which involve, e.g., star formation in massive clumps, compaction, and inside-out quenching. This study demonstrates the capabilities of JWST WFSS in conducting systematic investigations of emission line galaxies and highlights the pivotal role of Pa$α$ in advancing our understanding of dust extinction and obscured star formation in the early universe.

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arXiv2026

The BoRG-$JWST$ Survey: Abundance and Mass-to-light Ratio of Luminous $z=7-9$ Galaxies from Independent Sight Lines with NIRSpec

We present new results on the rest-frame UV luminosity function (UVLF) and stellar mass-to-light (M/L) ratio of bright (M$_{\rm UV}\lesssim-20$ mag) spectroscopically-confirmed galaxies at $z=7-9$ derived from the BoRG-$JWST$ survey, a unique data set of NIRSpec prism follow up of $HST$-selected sources from random-pointing imaging. By selecting galaxies from over 200 independent sight lines, the survey minimizes cosmic variance ensuring a statistically robust sample of the bright-galaxy population during the epoch of reionization. The data is used to constrain, for the first time, the bright end of the UVLF at $z=7-9$ from spectroscopically-confirmed galaxies over eight independent fields. We find that the bright end of the UVLF is higher than found using imaging over $JWST$ legacy fields, suggesting the latter may be significantly affected by cosmic variance, and thus reducing the tension with recent findings from $JWST$ at $z>10$ and comparable to models invoking little dust attenuation and bursty star formation. Additionally, we use the galaxies' $JWST$ spectra to infer their stellar masses and M/L ratios relative to other $HST$ and $JWST$ studies. We show that the stellar mass scales almost linearly with UV luminosity (M$_* \propto L_{\rm UV}^{0.85\pm0.12}$), albeit with large ($\sim0.5$ dex) intrinsic scatter, consistent with stochastic bursts of star formation in early galaxy formation.

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arXiv2025

TDCOSMO 2025: Cosmological constraints from strong lensing time delays

We present cosmological constraints from 8 strongly lensed quasars (hereafter, the TDCOSMO-2025 sample). Building on previous work, our analysis incorporated new deflector stellar velocity dispersions measured from spectra obtained with the James Webb Space Telescope (JWST), the Keck Telescopes, and the Very Large Telescope (VLT), utilizing improved methods. We used integrated JWST stellar kinematics for 5 lenses, VLT-MUSE for 2, and resolved kinematics from Keck and JWST for RXJ1131-1231. We also considered two samples of non-time-delay lenses: 11 from the Sloan Lens ACS (SLACS) sample with Keck-KCWI resolved kinematics; and 4 from the Strong Lenses in the Legacy Survey (SL2S) sample. We improved our analysis of line-of-sight effects, the surface brightness profile of the lens galaxies, and orbital anisotropy, and corrected for projection effects in the dynamics. Our uncertainties are maximally conservative by accounting for the mass-sheet degeneracy in the deflectors' mass density profiles. The analysis was blinded to prevent experimenter bias. Our primary result is based on the TDCOSMO-2025 sample, in combination with $Ω_{\rm m}$ constraints from the Pantheon+ Type Ia supernovae (SN) dataset. In the flat $Λ$ cold dark matter (CDM), we find $H_0=71.6^{+3.9}_{-3.3}$ km s$^{-1}$ Mpc$^{-1}$. The SLACS and SL2S samples are in excellent agreement with the TDCOSMO-2025 sample, improving the precision on $H_0$ in flat $Λ$CDM to 4.6%. Using the Dark Energy Survey SN Year-5 dataset (DES-SN5YR) or DESI-DR2 baryonic acoustic oscillations (BAO) likelihoods instead of Pantheon+ yields very similar results. We also present constraints in the open $Λ$CDM, $w$CDM, $w_0w_a$CDM, and $w_ϕ$CDM cosmologies. The TDCOSMO $H_0$ inference is robust and consistent across all presented cosmological models, and our cosmological constraints in them agree with those from the BAO and SN.

astro-ph.CO↗

arXiv2025

The Dual Nature of GHZ9: Coexisting Active Galactic Nuclei and Star Formation Activity in a Remote X-ray Source at z = 10.145

We present James Webb Space Telescope (JWST)/NIRSpec PRISM spectroscopic characterization of GHZ9 at z= 10.145 $\pm$ 0.010, currently the most distant source detected by the Chandra X-ray Observatory. The spectrum reveals several UV high-ionization lines, including CII, SiIV, NIV], CIV, HeII, OIII], NIII], and CIII]. The prominent rest-frame equivalent widths (EW(CIV)$\simeq$65A, EW(OIII])$\simeq$28A, EW(CIII])$\simeq$48A) show the presence of a hard active galactic nucleus (AGN) radiation field, while line ratio diagnostics are consistent with either AGN or star formation as the dominant ionizing source. GHZ9 is nitrogen-enriched (6--9.5 (N/O)$_{\odot}$), carbon-poor (0.2--0.65 (C/O)$_{\odot}$), metal-poor (Z = 0.01--0.1 Z$_{\odot}$), and compact ($<$ 106 pc), similarly to GN-z11, GHZ2, and recently discovered N-enhanced high redshift objects. We exploited the newly available JWST/NIRSpec and NIRCam data set to perform an independent analysis of the Chandra data confirming that GHZ9 is the most likely JWST source associated with X-ray emission at 0.5-7 keV. Assuming a spectral index $Γ$ = 2.3 (1.8), we estimate a black hole (BH) mass of 1.60 $\pm$ 0.31 (0.48 $\pm$ 0.09) $\times$ 10$^8$M$_{\odot}$, which is consistent either with Eddington-accretion onto heavy ($\geq$ 10$^6$ M$_{\odot}$) BH seeds formed at z=18, or super-Eddington accretion onto a light seed of $\sim$ 10$^2-10^4$ M$_{\odot}$ at z = 25. The corresponding BH-to-stellar mass ratio M$_{BH}$/M$_{star}$= 0.33$\pm$0.22 (0.10$\pm$0.07), with a stringent limit $>$0.02, implies an accelerated growth of the BH mass with respect to the stellar mass. GHZ9 is the ideal target to constrain the early phases of AGN-galaxy coevolution with future multi-frequency observations.

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arXiv2025

Parallel Application of Slitless Spectroscopy to Analyze Galaxy Evolution (PASSAGE): Survey Overview

During the second half of Cycle 1 of the James Webb Space Telescope (JWST), we conducted the Parallel Application of Slitless Spectroscopy to Analyze Galaxy Evolution (PASSAGE) program. PASSAGE received the largest allocation of JWST observing time in Cycle 1, 591 hours of NIRISS observations to obtain direct near-IR imaging and slitless spectroscopy. About two thirds of these were ultimately executed, to observe 63 high-latitude fields in Pure Parallel mode. These have provided more than ten thousand near-infrared grism spectrograms of faint galaxies. PASSAGE brings unique advantages in studying galaxy evolution: A) Unbiased spectroscopic search, without prior photometric pre-selection. By including the most numerous galaxies, with low masses and strong emission lines, slitless spectroscopy is the indispensable complement to any pre-targeted spectroscopy; B) The combination of several dozen independent fields to overcome cosmic variance; C) Near-infrared spectral coverage, often spanning the full range from 1.0--2.3 $μ$m, with minimal wavelength gaps, to measure multiple diagnostic rest-frame optical lines, minimizing sensitivity to dust reddening; D) JWST's unprecedented spatial resolution, in some cases using two orthogonal grism orientations, to overcome contamination due to blending of overlapping spectra; E) Discovery of rare bright objects especially for detailed JWST followup. PASSAGE data are public immediately, and our team plans to deliver fully-processed high-level data products. In this PASSAGE overview, we describe the survey and data quality, and present examples of these accomplishments in several areas of current interest in the evolution of emission-line galaxy properties, particularly at low masses.

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arXiv2025

JWST Discovery of Strong Lensing from a Galaxy Cluster at Cosmic Noon: Giant Arcs and a Highly Concentrated Core of XLSSC 122

Our observations with the James Webb Space Telescope have made the remarkable discovery of strong gravitational lensing arcs from XLSSC 122 ($z=1.98$) - setting the record for the most distant galaxy cluster that exhibits strong lensing. The discovery of giant arcs enables a strong-lensing analysis and a measurement of the concentration of the dark matter halo. We perform a strong-lensing analysis of the cluster and measure the radial projected mass density profile. Our measurements reveal an exceptionally high concentration in the core of XLSSC 122. A Navarro--Frenk--White profile fit to the inner 100 kpc estimates the concentration to be $6.3\pm0.5$. The high concentration of XLSSC 122 contributes to the emerging picture that massive structure formation in the early universe may proceed more rapidly than standard models suggest. We estimate the mass within 100 kpc to be $M$($R<$100 kpc) = $6.5\pm0.7\times10^{13}$ M$_\odot$. Our mosaic images are made public at https://kylefinner.github.io/xlssc122 .

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arXiv2025

Nature of High Equivalent Width Emitters in the Epoch of Reionization Revealed by JWST Medium-band Imaging

Extreme emission line galaxies (EELGs) at high redshifts are considered key contributors to cosmic reionization at $z>6$ due to their higher ionization efficiencies. We have identified 119 H$β$ + [OIII] emitters at $z\sim7$ selected by a flux excess in the medium-band filter F410M in the public James Webb Space Telescope Cycle-1 fields. Our emitters exhibit a wide range in rest-frame H$β$ + [OIII] equivalent width (EWs), 420 $<$ EW$_{0}$/Å $<$ 6850 (with the median value of $\sim1700$ Å). Among them, 19 are EW$_{0}$ $>$ 3000 Å, which represent extreme populations even in the context of recent findings with JWST. They are characterized by (i) low stellar mass ($\sim 3\times10^{7}$ $\mathrm{M_{\odot}}$), (ii) blue colors ($β_{\rm UV}\sim -2.2$), and (iii) low dust attenuation ($A_{\mathrm{V}}\sim 0.1$ mag). We discuss the physical mechanisms responsible for the observed high rest-frame H$β$ + [OIII] EWs, including (1) photoionization by AGN, (2) stellar photoionization in the vicinity of HII regions, and (3) radiative shocks powered by outflows either from AGN or massive stars. Notably, we find 13 emitters with spatially offset H$β$ + [OIII] emission compared to the UV and stellar components. Given the absence of obvious signatures of actively accreting black holes, these emitters are likely under strong feedback-driven winds from massive stars. Lastly, we report a unique overdensity of EELGs in one of the observed fields. The discovery of such a "star-bursting" overdensity supports the idea that large ionizing bubbles formed around some EEGLs in the early Universe.

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arXiv2025

The GLASS-JWST Early Release Science Programme: The NIRISS Spectroscopic Catalogue

We present a spectroscopic redshift catalogue of sources in the Abell 2744 cluster field, derived from JWST/NIRISS observations taken as part of the GLASS-JWST Early Release Science programme. We describe the data reduction, contamination modelling and source detection, as well as the data quality assessment, redshift determination and validation. The catalogue consists of 354 secure and 134 tentative redshifts, of which 245 are new spectroscopic redshifts, spanning a range $0.1 \leq z \leq 8.2$. These include 17 galaxies at the cluster redshift, one galaxy at $z \approx 8$, and a triply-imaged galaxy at $z = 2.653 \pm 0.002$. Comparing against galaxies with existing spectroscopic redshifts $z_{\rm{spec}}$, we find a small offset of $Δz = (z_{\rm{spec}} - z_{\rm{NIRISS}} )/(1 + z_{\rm{spec}} ) = (1.3 \pm 1.6) \times 10^{-3}$. We also present a forced extraction tool (pygrife) and a visualisation tool (pygcg) to the community, to aid with the reduction and classification of grism data. This catalogue will enable future studies of the spatially-resolved properties of galaxies throughout cosmic noon, including dust attenuation and star formation. As a first application of the catalogue, we discuss the spectroscopic confirmation of multiple image systems, and the identification of multiple overdensities at $1 < z < 2.7$.

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arXiv2025

Green Flash: Residual Emissions Enshrouded in Low-mass Balmer-break Galaxies at $z\sim5$

Recent James-Webb Space Telescope (JWST) observations have discovered galaxies that are already passively evolving at $z>4$, $\sim1.5$\,Gyr after the Big Bang. Remarkably, some of these galaxies exhibit strong emission lines such as \ha\ and \oiii\ while showing a strong continuum break at $\sim3650$\,Å i.e., Balmer break, giving us a unique insight into the physical mechanisms responsible for early galaxy quenching. In this study, we investigate the nature of four such galaxies at $z=5.10$--$5.78$ identified in the Abell~2744 field, using JWST/NIRCam and NIRSpec data. Our spectral energy distribution (SED) fitting analysis reveals that these galaxies have been mostly quiescent since $\sim100$\,Myr prior to the observed time. We find a higher dust attenuation in the nebular component than in the continuum in all cases. This suggests the presence of dusty star-forming regions or obscured AGN, which could be a {\it residual} signature of past quenching. For one of the galaxies with sufficient medium-band coverage, we derive the \hb+\oiii\ emission line map, finding that the line-emitting region is located in the center and is more compact ($R_e=0.7$\,kpc) than the stellar component ($R_e=0.9$\,kpc). For this specific galaxy, we discuss a scenario where quenching proceeds in the manner of ``outside-in", a stark contrast to the inside-out quenching commonly seen in massive galaxies at later cosmic times.

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arXiv2025

Potential Nitrogen Enrichment via Direct-Collapse Wolf-Rayet Stars in a $z=4.7$ Star-Forming Galaxy

We present analyses of a nitrogen-enriched star-forming galaxy, ID60001, at $z=4.6928$ based on JWST/NIRSpec MSA spectroscopy and NIRCam photometry. From rest-frame optical emission lines we derive the nitrogen-to-oxygen (N/O) abundance ratio of ID60001 to be $\log({\rm N/O})=-0.76_{-0.03}^{+0.03}$ ($[{\rm N/O}]=0.10_{-0.03}^{+0.03}$), which is significantly elevated at the corresponding metallicity $12+\log({\rm O/H})=7.75_{-0.01}^{+0.01}$ ($Z/Z_\odot = 0.12$) compared to local counterparts. We discuss possible scenarios for elevated N/O abundance in ID60001, including pristine gas inflow, Wolf-Rayet (WR) stars, and Oxygen depletion by Type II supernova winds. Based on the moderately broadened He{\sc ii}$λ$4686 emission line, galaxy morphology, and star-formation history, we conclude that the elevated N/O abundance of ID60001 is likely originated from massive ($>25\,M_\odot$) WR stars that directly collapse into a black hole. We also stress the importance of reliable electron density measurements when deriving N/O abundance with rest-frame optical emission lines.

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arXiv2025

Accelerated Emergence of Evolved Galaxies in Early Overdensities at $z\sim5.7$

We report the identification of two galaxy overdensities at $z\sim5.7$ in the sightline of the galaxy cluster Abell 2744. These overdensities consist of 25 and 17 member galaxies, spectroscopically confirmed with JWST NIRSpec/MSA and NIRCam/WFSS. Each overdensity has a total stellar mass of $\sim2\times10^{10} M_\odot$ and a star formation rate of $\sim200 M_\odot$/yr within a central region of radius $R=2$ Mpc (physical). The sensitive PRISM spectra allow us to identify six galaxies that show weak Ha+[NII] emissions within the overdensities ($27\pm6\%$), whereas the fraction of such galaxies is found significantly lower ($6\pm2\%$) in field samples of the equivalent redshift range. These weak emission line galaxies, dubbed as wELGs, exhibit a strong continuum break at $4000$AA rest-frame, a characteristic feature of evolved stellar populations. The high observed fraction of wELGs in the two overdensities is consistent with the idea that high-density environments are an ideal site where galaxies can accelerate their evolutionary pace compared to field analogs. Our study pinpoints an early onset of environmental effects, already important within one billion years after the Big Bang, and provides a complementary perspective on the emergence of quenched, massive galaxies at lower redshifts. Potential contributions from black hole accretion feedback to the reduction of star formation activity are discussed, but the connection to the local environments remains unclear.

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arXiv2025

Deciphering Gas Dynamics and Star Formation in a z=1.1 Main Sequence Spiral Galaxy with ALMA and JWST

We present a joint analysis of high-resolution CO(2-1) and Paschen-$α$ emission lines to trace gas dynamics and spatially resolved star formation in ASPECS-LP.3mm.06, a $z=1.1$ main sequence galaxy. Utilizing data from the ALMA and JWST NIRCam Wide Field Slitless Spectroscopy (WFSS), we explore both ionized gas and molecular gas within this galaxy. With a substantial molecular gas fraction (f$_\mathrm{mol}$ = 0.44 $\pm$ 0.02), ASPECS-LP.3mm.06 remains on the star-forming main sequence and adheres to the Kennicutt-Schmidt (KS) relation, indicating typical gas-to-star conversion efficiency. Our analysis reveals extended structures across multiple wavelengths, suggesting regulated star formation within a stable disk. The spatially resolved star formation efficiency (SFE) and kinematic analysis indicate that ASPECS-LP.3mm.06 features a smooth mass assembly process across bulge and disk. Additionally, the galaxy exhibits modest dust extinction (A$_\mathrm{V}$ = 0.8), potentially linked to self-regulation during bulge formation. These findings position ASPECS-LP.3mm.06 as a prototypical galaxy, offering valuable insights into the mechanisms governing normal disk galaxy growth at z$\sim$1.

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arXiv2025

Metallicity Scatter Originating from Sub-kiloparsec Starbursting Clumps in the Core of a Protocluster at z=7.88

We present new JWST NIRSpec integral field unit (IFU) G395H/F290LP observations of a merging galaxy system at $z=7.88$, part of A2744-z7p9, the most distant protocluster to date. The IFU cube reveals [OIII] emissions in two previously known galaxies (ZD3 and ZD6) and a newly identified galaxy, ZD12, at $z_{\rm spec}=7.8762$. One of the detected \oiii-emitting regions has a detection of the auroral [OIII]4363, line, allowing us to derive a direct metallicity of $\log$(O/H)$+12=7.4\pm0.2$, while metallicities in other regions are measured using strong line calibration methods. We find large deviations within the measured metallicity ($Δ\log {\rm (O/H)}\sim1$), which suggests a fast chemical enrichment from intense star formation and merger-driven growth, as expected in early galaxies. Our analysis shows that metal-poor regions could easily be outshone by more enriched regions, posing a challenge for spectroscopic analysis based on integrated light (i.e., NIRSpec MSA) against identifying metal-free star formation in the early universe. NIRCam imaging reveals seven UV-bright clumps in ZD12, in the range of stellar mass $\log M_*/M_\odot\sim7.6$--8.9. Four of them are unresolved ($< 100$pc) and intensely star-forming ($>30 M_\odot {\rm yr^{-1} kpc^{-2}}$), likely contributing to the scatter in metallicity by producing an ideal environment for rapid chemical cycles. Lastly, we revisit the nature of the host protocluster by including new member galaxies identified here and in the literature, and obtain local overdensity factor $δ=44_{-31}^{+89}$, total halo mass $M_{\rm h} = 5.8_{-0.3}^{+0.2}\times10^{11}\,M_\odot$, and a formal velocity dispersion of $1100\pm500$ km s$^{-1}$.

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