arXiv subjects

Hanae Inami

Publications and source records attributed to Hanae Inami.

At least 19 recordsLinked to original sources

arXiv2026

JWST/NIRSpec Reveals Diverse Nuclear Environments in Dwarf Galaxies Hosting AGN

Dwarf galaxies, in the $\Lambda$CDM framework, are expected to dominate the galaxy number density at all redshifts. As such, studying AGN in these systems, including characterizing their local environments and emission properties, is essential in obtaining a comprehensive view of the AGN population and their influence on their host galaxy. To this end, we present JWST/NIRSpec IFU observations of four dwarf galaxies (M$_\star<$10$^{9.5}\;$M$_\odot$) with evidence of AGN activity. Utilizing the improvements in resolution and sensitivity offered by JWST, we investigate the emission features of the central kiloparsec of these dwarfs. Our findings include the detection of over 100 emission lines across our sample, including coronal lines with ionization potentials greater than 300 eV. The nuclear spectra show diverse emission features. In two galaxies, we measure strong contributions from hot dust to the infrared continuum. We also detect both PAH and coronal line emission within 100 parsecs of the nuclei in three galaxies. We estimate the hot H$_2$ gas mass to be between 1--20 M$_\odot$ within 300 pc across our sample, where both thermal and non-thermal excitation are involved. Lastly, spatial flux maps reveal varied emission structures across all observed gas phases, ranging from radial symmetry around the nucleus to elongated plumes. Kinematic maps also show each galaxy has unique velocity structures despite all being isolated, affirming the diversity of rotation curves problem, a long standing tension between simulations and observations. These results showcase the unique and varied nuclear environments that can be found in dwarf galaxies hosting AGN.

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arXiv2026

REBELS-25: multi-phase morphology and kinematics at z = 7.31

We present a spatially resolved, multi-wavelength study of the massive, star-forming galaxy REBELS-25 at a redshift of $z=7.31$. We combine new high-resolution ALMA [O III]88$\mu$m observations with resolution-matched [C II], dust continuum, and JWST/NIRSpec IFU spectroscopy, providing a $\lesssim1$ kpc view of the morphology, interstellar medium (ISM) conditions, and multi-tracer gas kinematics of one of the most mature galaxies known in the reionisation era. We find differing morphologies from the rest-frame UV to far-infrared (FIR) emission, with the UV and optical emission appearing clumpy and irregular, whereas the FIR emission is well-described by near-exponential disc profiles, with [C II] being the most extended. Comparing the resolved UV and FIR emission, we find that obscured star formation contributes $\sim55$-$98$% of the total star formation rate across the galaxy, demonstrating that dust obscuration strongly shapes the observed UV and optical morphology. Resolved ionisation-line diagnostics show no significant variation across the source at $\sim1$ kpc resolution, consistent with broadly similar ISM conditions among the identified regions. Kinematic modelling reveals that both the warm ionised gas, traced by [O III]88$\mu$m, and the colder neutral gas, traced by [C II], share the same large-scale rotating structure and are dynamically cold, with ratios of ordered-to-random motion, $V/\sigma$, of $\sim11$ and 4.5, respectively, although we find evidence for non-circular motions that are not well-described by a simple rotating disc. Overall, these results further support a picture in which REBELS-25 hosts a dusty, chemically enriched, and dynamically cold ISM already in place at $z=7.31$.

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arXiv2026

Tracing Lyman alpha escape in the CRISTAL-02 galaxy at z~5.3

We investigate the mechanisms regulating Lyman-alpha (Ly$\alpha$) escape in the star-forming galaxy CRISTAL-02 at z~5.3. The galaxy has clumpy morphology, suggestive that it may be interacting with other system(s). Two clumps (A and B, hereafter) are suggested as a site for intense star-formation or potential AGN candidates. We investigate how the local gas, dust, and feedback shape the escape of Ly$\alpha$ photons around these clumps. Using VLT/MUSE and JWST/NIRSpec IFU observations, complemented by NIRCam UV imaging, we constructed spatially matched emission-line maps. We derived flux, line-ratio, and extinction maps, together with spatially resolved Ly$\alpha$ escape fractions and ionizing photon production efficiencies. We find that Ly$\alpha$ is significantly more extended than H$\alpha$ and UV, reaching ~33 kpc and preferentially extending along the cold molecular gas outflow traced by [C II] emission. Clumps A and B show contrasting Ly$\alpha$ properties: Clump A has lower dust attenuation and enhanced Ly$\alpha$/H$\alpha$ ratios and escape fraction, whereas Clump B is brighter in H$\alpha$ and UV but has suppressed Ly-$\alpha$ despite a higher ionizing photon production efficiency. These results indicate that Ly$\alpha$ escape is strongly influenced by the local H I geometry, dust, and outflows and cannot be explained by ionizing photon production alone. The observed Ly$\alpha$ morphology and zELDA radiative transfer modeling favor an outflow-driven escape scenario, while the available data cannot uniquely distinguish between AGN and star formation-driven feedback.

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arXiv2026

Breathing Fire: Hot Dust in the Big Three Dragons at z = 7.15

We present new Atacama Large Millimeter/submillimeter Array (ALMA) Band 9 ($\lambda_\mathrm{obs} = 0.45\,\mathrm{mm}$) and 4 ($\lambda_\mathrm{obs} = 2.2\,\mathrm{mm}$) observations towards the Big Three Dragons, a pair of merging Lyman-break galaxies (LBGs) at $z=7.15$. The system was previously detected in ALMA Bands 6, 7 and 8 ($\lambda_\mathrm{obs} = 0.73 - 1.32\,\mathrm{mm}$), which, combined with our new observations, allows us to robustly constrain its dust temperature and obscured SFR. The unresolved Band 4 observations yield a $3.5\sigma$ detection, and the $0.4''$ Band 9 observations detect the Eastern and Western LBGs at $3.7$ and $3.5\sigma$, respectively. Through modified blackbody fitting, we infer a global dust temperature of $T_d = 78_{-23}^{+35}\,\mathrm{K}$ for the system, which implies a high IR luminosity of $\log(L_\mathrm{IR}/L_\odot) = 12.32_{-0.41}^{+0.43}$. This makes the Big Three Dragons one of the most IR-luminous systems known at $z>7$, with a total $\mathrm{SFR}_\mathrm{UV+IR} = 267_{-153}^{+418}\,M_\odot\,\mathrm{yr}^{-1}$ that is almost completely obscured ($f_\mathrm{obs} = 0.94_{-0.09}^{+0.04}$). Using resolved ALMA observations in Bands 6, 8 and 9, we confirm both LBGs have hot dust temperatures ($T_d \approx 67 - 84\,\mathrm{K}$) and correspondingly high obscured fractions ($f_\mathrm{obs} \approx 0.88 -0.95$). We find the Western LBG to fall $\sim1\,\mathrm{dex}$ above the canonical IRX-$\beta_\mathrm{UV}$ relation, suggesting patchy dust obscuration. The compact Eastern component, on the other hand, is consistent with a Calzetti- or SMC-like dust screen within the uncertainties. Together with the similarly hot dust temperature recently reported for the $z=8.31$ galaxy MACS0416-Y1, our results suggest a non-negligible fraction of star formation at the bright end of the UV luminosity function is highly dust-obscured, even at $z\gtrsim7$.

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arXiv2026

KCWI Discovery of a Spatially Resolved Kpc-Scale Ionized Outflow in NGC 1275

We present new Keck Cosmic Web Imager observations of the central few kiloparsecs of NGC 1275, the brightest cluster galaxy of the Perseus Cluster. These integral field spectroscopic data reveal a warm-ionized outflow traced by H$\beta$ and the [O III] doublet extending out to $\sim2.5$ kpc from the nucleus. The warm-ionized outflow has an [O III]-derived $v_{50}$ of up to $\sim570$ km/s, $w_{80}$ of up to $3780$ km/s, and H$\beta$-derived outflowing mass of $(2.7 \pm 0.3)\times 10^6$ M$_\odot$. Our H$\beta$-derived warm-ionized outflowing mass rate of 2.7$\pm$0.7 M$_\odot$ yr$^{-1}$ is comparable to the estimated cold molecular disk accretion rate of 1$-$10 M$_\odot$ yr$^{-1}$, which could be a sign of self-regulation between the pc-scale cold gas feeding the active galactic nucleus (AGN) and the warm wind accelerated out to kpc scales. In the host galaxy, we detect an enhancement in the [O III] / H$\beta$ ratio in the direction of the receding jet, which may imply jet interaction with the host interstellar medium. The outflow component also shows a clear enhancement of [O III] / H$\beta$ that positively correlates with $w_{80}$ and $v_{50}$, indicative of AGN influence and/or fast shocks. Both the outflow and host galaxy [O III] / H$\beta$ ratio decrease with increasing distance from the center, showing that the influence of the AGN is confined to the central $\sim2$ kpc. These results are the first resolved measurements of a kpc-scale ionized wind in NGC 1275 and provide a view into how both jets and winds contribute to the feedback cycles in complex cool core cluster systems.

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arXiv2026

PAHSPECS: Polycyclic aromatic hydrocarbon properties at cosmic noon with JWST/MIRI MRS

Context. Cosmic noon (z ~ 1-3) marks the peak of the cosmic star-formation rate density, when dust-obscured star formation dominated galaxy growth. Mid-infrared spectroscopy probes the interstellar medium through PAH emission, whose band ratios trace PAH charge, size, and local radiation-field conditions. Aims. We characterize the PAH properties of five z ~ 1.1 star-forming galaxies from the PAHSPECS survey and investigate how their PAH luminosities and band ratios relate to global galaxy properties. We compare them with local luminous infrared galaxies (LIRGs) to assess whether PAH emission at cosmic noon differs from that nearby. Methods. We analyze JWST/MIRI MRS observations of five ASPECS galaxies in the HUDF. Integrated spectra are extracted with wavelength-dependent apertures and modeled with CAFE, including ancillary photometry to constrain the dust emission. Stellar masses and SFRs are derived with Prospector. Results. Compared to local LIRGs, most PAHSPECS sources show higher 6.2/7.7 and lower 11.3/7.7 ratios, suggesting an ionized PAH component weighted toward smaller grains. The 3.3/11.3 ratio is less constrained, since the 3.3 micron feature is detected in only two sources. Within the sample, 11.3/7.7 increases with sSFR and star-formation surface density, while 6.2/7.7 decreases with sSFR, consistent with preferential processing of small ionized PAH carriers. ASPECS-15, the AGN-hosting source, has the lowest 6.2/7.7 ratio and highest sSFR, suggesting a reduced contribution from small PAHs, potentially due to AGN activity. The 7.7 micron luminosity follows the local L7.7-SFR relation, supporting its use as a star-formation tracer at z ~ 1. Conclusions. PAH emission at cosmic noon appears shaped by different ISM conditions than in nearby starburst galaxies, likely reflecting more intense radiation fields, while the 7.7 micron feature remains a robust SFR tracer.

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arXiv2026

PAHSPECS: Spatially Resolved PAH Spectroscopy at cosmic noon with JWST MIRI MRS

We present spatially resolved spectroscopy with JWST/MIRI MRS of a representative sample of normal star-forming galaxies at $z\sim1.1$ as part of the PAHSPECS program. To extract emission from Polycyclic Aromatic Hydrocarbon (PAH) features, we forward model the data cubes with non-parametric spatial distributions, accounting for convolution with the PSF. With this method we are able to recover accurate spatial profiles of the 3.3 $\mu$m, 6.2 $\mu$m, 7.7 $\mu$m, 11.3 $\mu$m PAHs and [ArII] (6.98 $\mu$m) emission and produce PAH ratio maps at cosmic noon. From the PAH ratio maps we find that PAHs become larger and more neutral with increasing galactocentric radius, which is the opposite of trends in local galaxies, indicating radial ISM gradients in normal star-forming galaxies are different at cosmic noon. Through spatially resolved SED fitting of HST and JWST photometry we measure the UV radiation field hardness through the intrinsic ratio of UV to optical flux and find the 3.3/11.3 PAH ratio to decrease with increasing hardness and the 11.3/7.7 to increase. This may suggest photo-destruction of small/ionized PAHs is driving the observed PAH ratio trends and may explain the overall lower 3.3/11.3 PAH at cosmic noon compared to the local universe. This work demonstrates that PAH properties hold crucial information on the resolved ISM physics of galaxies at cosmic noon.

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arXiv2026

Direct detection of cool molecular gas in a star-forming galaxy at $z=7.31$

We investigate the molecular gas content and interstellar medium (ISM) conditions of REBELS-25, a massive, star-forming galaxy at $z=7.31$. Deep VLA Q-band and ALMA Band 3 observations reveal CO(3-2) and CO(7-6) emission (both at $\sim3.5\sigma$), and provide an upper limit on [C I](2-1). From the CMB-corrected CO(3-2) flux-representing the highest-redshift detection of a low-$J$ CO transition to date-we derive a molecular gas mass of $M_{\rm mol}=(1.0\pm0.4)\times10^{11}\,(\alpha_{\rm CO}/(3\,$M$_{\odot}$(K$\,$\kms$\,$pc$^2)^{-1}))\,$M$_{\odot}$, directly confirming the presence of a very massive gas reservoir only $\simeq700\,$Myr after the Big Bang. This implies an extreme gas fraction of $f_{\rm gas}\simeq0.95$, a gas-to-dust ratio of $\delta_{\rm GDR}\simeq6\times10^2$, and a depletion timescale of $\tau_{\rm dep}\simeq1.2\,$Gyr, broadly consistent with extrapolated scaling relations for main-sequence galaxies at lower redshift. Using the radiative transfer code TUNER, we self-consistently model CO and dust continuum emission in the context of the significant CMB background, constraining ISM properties and recovering $M_{\rm mol}= (1.8^{+1.0}_{-0.9})\times10^{11}\,$M$_{\odot}$, independent of assumptions about $r_{31}$ and $\alpha_{\rm CO}$. We further discuss the use of alternative molecular gas tracers at early epochs. Combining CO and [C II] measurements, we infer an empirical [C II]-to-H$_2$ conversion factor of $\alpha_{\rm [C II]}=(60\pm25)\,$M$_{\odot}$/L$_{\odot}$, suggesting [C II] remains a viable molecular gas tracer in the Epoch of Reionization. These results demonstrate the detectability of low-$J$ CO emission even at $z>7$, paving the way for next-generation facilities, and provide critical insights into the rapid mass assembly of galaxies during the first billion years of cosmic history.

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arXiv2026

3D-Herschel: Constraining Dust Emission with Panchromatic Modeling of 3D-HST Galaxies

We present 3D-Herschel, a new publicly released 0.3-350$\mu$m photometric catalog that combines deblended Herschel far-infrared (FIR) imaging with the CANDELS/3D-HST legacy fields to probe the dust-obscured universe. Using the 17-parameter Bayesian fitting code Prospector-$\beta$, we model 41,387 galaxies spanning 0.5 $< z <$ 2.5 to measure stellar and dust properties. Comparing fits with and without FIR constraints, we find that for the 3.2$\%$ of galaxies with $>3 \sigma$ detections in $\geq2$ Herschel bands, UV-MIR-only models (0.3-24$\mu$m) recover robust stellar ages, SFRs, and stellar masses (50-70$\%$ within the median 1$\sigma$ error). Consequently, the Prospector-$\beta$ star-forming sequence is unchanged by the inclusion of FIR data (average deviation 0.1$\pm$0.07 dex between UV-MIR and UV-FIR fits at fixed stellar mass), confirming that the offset relative to UV+IR-based estimates reported by Leja et al. 2022 is robust to the lack of direct FIR constraints. However, the use of rigid log-average IR templates with fixed dust emission parameters ($\gamma$, $U_{\mathrm{min}}$, $q_{\mathrm{PAH}}$) in UV-MIR modeling yields cold dust temperatures ($\sim$7K colder than Herschel-informed fits at all redshifts) and an unevolving MIR-to-IR luminosity ratio, with $\sim$0.2 dex lower IR-to-7.7$\mu$m luminosity ratios at the low-mass end of Herschel-detected galaxies (log($M_{\star}$) $\sim$ 9.6 $M_{\odot}$). These results demonstrate that MIR-to-IR conversions depend on stellar mass, cautioning against $L_{\mathrm{IR}}$-independent templates without FIR data. For galaxies with $<10^{11} \ M_{\odot}$ at $z>1.5$, Herschel can at best provide upper limits due to source confusion; next-generation FIR telescopes will be essential for distant galaxies.

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arXiv2026

The ALPINE-CRISTAL-JWST Survey: Chemical Abundance Comparison Between the ISM and CGM of Main-Sequence Galaxies at z=4-6

Gaseous halos around galaxies play an important role in galaxy evolution. The exchange of metals from the interstellar medium (ISM) to the circumgalactic medium (CGM) are caused by the formation, feedback, and/or merging history of galaxies. We study the variation in chemical composition between the ISM ($\lesssim3\,$kpc) and CGM ($\sim5-10\,$kpc) for a sample of $M_{\star}>10^{9.5}\,M_{\odot}$ main-sequence galaxies at $4<z<6$ with both JWST and ALMA observations. Using JWST/NIRSpec integral field spectroscopy, we derive the optical line ratios from the ISM and the CGM for our sample focusing on the typical optical lines used for metallicity studies. Our comparison shows that the ISM and the CGM have similar chemical abundances. This indicates that the CGM of these typical $4<z<6$ galaxies is enriched to the level of their ISM in the early universe. Using statistical tests, we find that some of the line ratios show marginal differences between the ISM and CGM. Combined with \texttt{Cloudy} modeling, our results suggest that a difference in ionization level (higher for the ISM) is the dominant reason for the observed ratio difference of oxygen line ratios. There is also indication of a deficit in the nitrogen abundance with respect to oxygen in the CGM, which suggests a delay in redistribution of secondary nitrogen. Finally, an enhanced $F_{[\rm CII]\rm 158\mu m}/F_{\rm H\alpha}$ ratio is observed in the CGM, suggesting that feedback and/or mergers play a key role in metal mixing.

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arXiv2026

A precessing jet from an active galactic nucleus drives gas outflow from a disk galaxy

To reproduce observed galaxy properties, cosmological simulations require that massive galaxies experience feedback from active galactic nuclei, which regulates star formation within those galaxies. However, the energetics and timescales of these feedback processes are poorly constrained. We combine optical, infrared, sub-millimeter and radio observations of the active galaxy VV 340a, hosting a low-power jet launched from a supermassive black hole at its center. We find that the jet undergoes precession, with a period of (8.2 $\pm~$5.5) $\times~$10$^5$ years, and drives an outflow of gas at a rate of 19.4 $\pm~$7.9 solar masses per year. The jet shocks the gas, producing highly ionized plasma extending several kiloparsecs from the nucleus. The outflow ejects sufficient gas from the galaxy to influence its star formation rate.

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arXiv2025

A first systematic study of [OIII] 88$\mu$m at $z>8$: two luminous oxygen lines and a powerful ionized outflow in the first 600 million years

We present deep ALMA Band 7 observations of the [OIII] $88\mu$m line and underlying dust continuum emission in four UV-bright, gravitationally lensed (magnification $\mu = 1.4-3.8$), JWST-selected galaxies at $z = 8.5 - 10.3$, with observed magnitudes $-22.5 \lesssim M_\mathrm{UV} \lesssim -20.5$. [OIII] $88\mu$m is confidently detected in UNCOVER-10646 at $z=8.5080 \pm 0.0011$ ($15\sigma$) and DHZ1 at $z=9.3113 \pm 0.0006$ ($6\sigma$), with both being intrinsically luminous systems [$L_\text{[OIII]} = (1.1 - 1.6) \times 10^9\,L_\odot$] that follow the local [OIII]-SFR relation. [OIII] $88\mu$m remains undetected in the two $z>10$ targets, including in the $z=10.07$ X-ray AGN UHZ1, where we obtain a deep limit of $L_\text{[OIII]} < 6 \times 10^7\,L_\odot$. Dust emission is not detected in any individual source nor in a stack ($<3\sigma$). The high S/N [OIII] $88\mu$m detection in UNCOVER-10646 uniquely reveals an additional broad component ($\mathrm{FWHM} = 1366_{-329}^{+473}\,\mathrm{km/s}$; $\Delta\mathrm{BIC}\approx20$) indicative of an ionized outflow. We infer a high outflow rate of $\dot{M}_\mathrm{out} = 128_{-46}^{+80}\,M_\odot\,\mathrm{yr}^{-1}$, corresponding to a mass loading factor $\eta = \dot{M}_\mathrm{out}/\mathrm{SFR} = 2.9_{-1.0}^{+1.8}$ that matches or exceeds theoretical predictions and JWST-based studies of ionized outflows at high redshift. While high-resolution ALMA follow-up is required to confirm and spatially resolve the outflow, this first systematic study at $z>8$ highlights the unique diagnostic power of [OIII] $88\mu$m in characterizing galaxies in the early Universe.

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arXiv2025

Probing Infrared eXcess to Investigate Early-Universe Dust (PIXIEDust)

Despite the implied presence of dust through reddened UV emission in high-redshift galaxies, no dust emission has been detected in the (sub)millimetre regime beyond $z > 8.3$. This study combines around two hundred hours of Atacama Large Millimeter/submillimeter Array (ALMA) and Northern Extended Millimeter Array (NOEMA) observations on ten $z > 8$ galaxies, revealing no significant dust emission down to a $1 \sigma$ depth of $2.0$, $2.0$, and $1.5 \,\mu$Jy at rest-frame 158, 88 $\mu$m, and across all the data, respectively. This constrains average dust masses to be below $< 10^{5}$ M$_{\odot}$ at $3 \sigma$ and dust-to-stellar mass ratios to be below $3.7 \times{} 10^{-4}$ (assuming $T_{\rm dust} = 50$ K and $\beta_{\rm dust} = 2.0$). Binning by redshift ($8 < z < 9.5$ and $9.5 < z < 15$), UV-continuum slope ($\beta_{\rm UV} \lessgtr -2$) and stellar mass ($\log_{10} M_{\ast}/{\rm M_{\odot}} \lessgtr 9$) yields similarly stringent constraints. Combined with other studies, these results are consistent with inefficient dust build-up in the $z > 8$ Universe, likely due to inefficient supernova production, limited interstellar grain growth and/or ejection by outflows. We provide data and tools online to facilitate community-wide high-redshift dust searches.

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arXiv2025

Probing AGN Feedback in Dwarf Galaxies with Spatially Resolved NIR Coronal Lines from JWST

We present the first spatially resolved investigation of near-infrared coronal lines in dwarf galaxies hosting active galactic nuclei (AGN), using JWST/NIRSpec integral field spectroscopy. Coronal lines (CLs), which are forbidden transitions from highly ionized species with ionization potentials up to 450 eV, act as sensitive tracers of the AGN ionizing continuum and feedback processes. Across four dwarf galaxies with ionized gas outflows traced by the optical [O III] lines, we report the detection of 16 unique species of near-infrared CLs. Line ratio diagnostics indicate that photoionization from the AGN dominates the excitation of CLs. We find that the coronal line region in dwarf galaxies, traced by the various CLs, extends up to 0.5 kpc, and can constitute up to 10% of their host galaxy size. Correlations between CL luminosities and [O III] ionized gas outflow properties are consistent with a scenario in which AGN-driven outflows likely facilitate the detection of CLs and contribute to their extent. Several CLs, including [Si VI], [Si VII], and [Mg VIII], exhibit a secondary broad component with W$_{80}$ (the line width enclosing 80% of the total flux)> 300 km/s. If we interpret this spatially compact gas as part of an outflow, this would indicate that the outflowing gas includes a wide range of ionizations. The estimated energetics imply this highly ionized component is compact yet powerful enough to perturb gas in the central regions of the host dwarfs. These results indicate that AGN in low-mass galaxies may produce outflows capable of influencing their structure and evolution.

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arXiv2025

A warm ultra-luminous infrared galaxy just 600 million years after the Big Bang

We present an Atacama Large Millimeter/submillimeter Array (ALMA) Band 9 continuum detection ($3.3 \sigma$) of MACS0416_Y1 that confirms the suspected warm dust (91$^{+62}_{-35}$ K) of this Lyman-Break Galaxy (LBG) at $z = 8.3$ with $\log_{10} M_{\ast}/$M$_{\odot} = 9.0 \pm 0.1$. A modified black-body fit to the ALMA Bands 3 through 9 data of MACS0416_Y1 finds an intrinsic infrared luminosity of 1.0$^{+1.8}_{-0.6} \times{} 10^{12}\ \mathrm{L_{\odot}}$, placing this UV-selected LBG in the regime of Ultra Luminous Infrared Galaxies (ULIRGs). Its luminous but modest dust reservoir (1.4$^{+1.3}_{-0.5} \times{} 10^{6}\ \mathrm{M_{\odot}}$) is co-spatial to regions with a UV-continuum slope $\beta_{\rm UV} \approx -1.5$ as seen by James Webb Space Telescope (JWST) imaging. Although this implies some dust obscuration, the JWST photometry implies less obscured star formation than seen in the complete characterization by ALMA, implying some spatial separation of dust and stars on scales below 200 pc, i.e., smaller than those probed by JWST and ALMA. This source is an extreme example of dust-obscured star formation contributing strongly to the cosmic build-up of stellar mass, which can only be revealed through direct and comprehensive observations in the (sub)mm regime.

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arXiv2025

The ALPINE-CRISTAL-JWST Survey: Stellar and nebular dust attenuation of main-sequence galaxies at z~4-6

Characterizing dust attenuation is crucial for revealing the intrinsic physical properties of galaxies. We present an analysis of dust attenuation in 18 spectroscopically confirmed star-forming main-sequence galaxies at $z = 4.4-5.7$ observed with JWST/NIRSpec IFU and NIRCam, selected from the ALPINE and CRISTAL ALMA large programs. We fit the emission line fluxes from NIRSpec and the broad-band photometry from NIRCam with Prospector, using both spatially integrated emission and $\sim0.6$ kpc pixel-by-pixel measurements. We derive the stellar-to-nebular dust attenuation ratio ($f=E(B-V)_{\mathrm{star}}/E(B-V)_{\mathrm{neb}}$) from the SED fits and the Balmer decrement with H$\alpha$ and H$\beta$. Although individual galaxies show large scatter, the best-fit value is $f = 0.51^{+0.04}_{-0.03}$, slightly higher than that measured for local starburst galaxies. We find weak correlations of $f$ with galaxy properties, increasing with higher specific star-formation rates, younger stellar ages, and more recent star-formation. For the range of $E(B-V)_{\mathrm{star}} = 0.009-0.15$ mag for in our sample, assuming $f = 1$ (often adopted in high-redshift studies) instead of $f = 0.51$ underestimate line luminosities and ionizing photon production efficiency $\xi_\text{ion}$ by $\sim3-36\%$ and $\sim4-46\%$, respectively. We also find that the total stellar masses estimated from spatially-integrated SED fits with a delayed-$\tau$ star-formation histories are systematically smaller than the sum of pixel-by-pixel SED fits, with a median offset of $\sim 0.26$ dex, likely because the integrated fits are biased toward luminous young stellar populations.

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arXiv2025

The ALPINE-CRISTAL-JWST Survey: The Fast Metal Enrichment of Massive Galaxies at z~5

We present the stellar mass-metallicity relation (MZR) and mass-metallicity-star formation relation ("fundamental metallicity relation"; FMR) of 18 massive (log(M/Msun) = 9.5 - 11) main-sequence galaxies at z~5 from the ALPINE-CRISTAL-JWST sample. This sample complements recent studies by JWST at up to two orders of magnitude lower stellar masses. The metallicities are derived using strong optical lines, and verified by temperature-based oxygen abundance measurements for five galaxies for which faint auroral lines are detected. We find that the metal abundance evolves, on average, from 40% to 60% solar between z~5 and cosmic noon (z~2) at the massive end of the MZR, suggesting already significant metal enrichment at early times. The FMR at z=5 exhibits a 5x larger scatter (preferentially to lower metallicities) compared the local FMR relation. This scatter can be explained by a bursty star formation and the direct build-up of metals in early galaxies as well as differences in age and outflow efficiencies. Capitalizing on all available samples, we find that the observed MZR and FMR over three orders of stellar mass is generally in good agreement with results from cosmological simulation, although some underestimate the metal enrichment at low stellar masses. This may be due to too efficient metal-rich outflows. We show that the ALPINE-CRISTAL-JWST galaxies likely joined the current FMR at z~10 and will evolve into massive (log(M/Msun)~11.4) galaxies with super-solar metallicities by z=0.

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arXiv2025

The ALPINE-CRISTAL-JWST Survey: NIRSpec IFU Data Processing and Spatially-resolved Views of Chemical Enrichment in Normal Galaxies at z=4-6

We present a statistical study of spatially resolved chemical enrichment in 18 main-sequence galaxies at $z=4$--6, observed with \jwst/NIRSpec IFU as part of the ALPINE-CRISTAL-\jwst\ survey. Performing an optimized reduction and calibration procedure, including local background subtraction, light-leakage masking, stripe removal, and astrometry refinement, we achieve robust emission-line mapping on kiloparsec scales. Although line-ratio distributions vary across galaxies in our sample, we generally find mild central enhancements in [O\,\textsc{iii}]/H$\beta$, [O\,\textsc{ii}]/[O\,\textsc{iii}], [S\,\textsc{ii}]$_{6732}$/[S\,\textsc{ii}]$_{6718}$, H$\alpha$/H$\beta$, and $L_{\rm H\alpha}/L_{\rm UV}$, consistent with elevated electron density, dust obscuration, and bursty star formation accompanied by reduced metallicity and ionization parameter. These features point to inside-out growth fueled by recent inflows of pristine gas. Nevertheless, the median metallicity gradient is nearly flat over a few kpc scale, $\Delta \log({\rm O/H}) = 0.02 \pm 0.01$ dex kpc$^{-1}$, implying efficient chemical mixing through inflows, outflows, and mergers. From pixel-by-pixel stellar and emission-line characterizations, we further investigate the resolved Fundamental Metallicity Relation (rFMR). Metallicity is described by a fundamental plane with stellar mass and SFR surface densities, but with a stronger dependence on $\Sigma_{\rm SFR}$ than seen in local galaxies. Our results indicate that the regulatory processes linking star formation, gas flows, and metal enrichment were already vigorous $\sim$1 Gyr after the Big Bang, producing the nearly flat metallicity gradient and a stronger coupling between star formation and metallicity than observed in evolved systems in the local universe.

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