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Manuel Aravena

Publications and source records attributed to Manuel Aravena.

At least 19 recordsLinked to original sources
arXiv2026

A Census of the 200 Most Massive Galaxies Spectroscopically Observed with JWST at zspec $\sim$3-15

Massive galaxies provide strong tests of galaxy formation models, yet a comprehensive spectroscopic view of their properties and demographics in the early Universe has remained elusive. Here we present a JWST spectroscopic census of the 200 most massive galaxies at zspec~3-15, selected using an evolving stellar-mass threshold motivated by the halo mass function and anchored at log(Mstar)>10 at z~5. These galaxies represent the top 3% most massive systems among all publicly available prism observations. We derive their physical properties through joint SED fitting of spectroscopy and photometry, and construct a clean massive galaxy sample after removing LRDs and broad-line AGN contaminants. We find that the massive galaxy population evolves strongly with redshift: normal SFGs (Av<1 mag) dominate at z>~6, while dusty SFGs (Av>1 mag) and QGs become more common toward lower redshift. Dust attenuation decreases systematically toward higher redshift. We identify 29 massive QGs, including a population of recently quenched systems whose star formation declined rapidly within the past ~100 Myr. We further show that both the traditional UVJ and recently proposed (ugi)s selections suffer substantial inconsistency with the most massive galaxies at z>3, motivating a revised (ugi)s criterion calibrated using our spectroscopic sample. The inferred formation histories suggest at least two pathways toward quiescence: a dust-enriched pathway linking normal SFGs, dusty SFGs, and QGs, and a more direct pathway connecting normal SFGs and QGs. Massive normal SFGs appear to grow through both relatively gradual and rapid assembly modes. Together, these results suggest that rapid stellar-mass assembly, dust enrichment, and quenching were already shaping the evolutionary pathways of the most massive galaxies within the first billion years after the Big Bang.

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arXiv2026

The ALPINE-CRISTAL-JWST Survey: The Tully-Fisher Relation at $z = 4-6$

The Tully-Fisher relation provides a fundamental link between galaxy mass and their kinematics. Although its evolution is relatively well constrained up to cosmic noon, observational probes at higher redshifts remain scarce. In this work, we investigate the stellar and baryonic Tully-Fisher relations (TFRs) at $z=4-6$ by analyzing JWST/NIRSpec IFU observations of 18 main-sequence star-forming galaxies belonging to the ALPINE-CRISTAL-JWST survey. We apply a morpho-kinematic disk classification scheme, finding five disk-like galaxies and a survey disk fraction of $0.28\pm0.11$. These disk galaxies span stellar masses of $10^{9.5-10.5}\,M_\odot$, intrinsic rotational velocities of $91-127\,{\rm km\,s^{-1}}$, and intrinsic velocity dispersions of $66-129\,{\rm km\,s^{-1}}$. For both versions of the TFR, we find that the ALPINE-CRISTAL-JWST disks lie below the local relations and are likely offset from those reported at cosmic noon ($z\approx2.3$). By fixing the TFR slope to the $z=0$ value, we measure zero-point offsets for the stellar-mass TFR of $-0.96\pm0.18$ dex and $-0.50\pm0.18$ dex relative to the local Universe and cosmic noon, respectively. For the baryonic TFR, we find zero-point offsets of $-0.57\pm0.20$ dex and $-0.30\pm0.20$ dex with respect to the local Universe and cosmic noon relations. Our measurements are consistent with the redshift evolution of the zero-points of both TFRs being driven by the evolution of dark matter halo properties with cosmic time, modulated by a reduced contribution of dark matter to the dynamical mass on the galaxy scale.

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arXiv2026

EMBER: A Little Red Dot Candidate at $z_{\rm spec}=10.36$ in the Seed Black Hole Era

Little red dots (LRDs) are a newly discovered population that may trace rapidly growing black holes (BHs) and provide a link between seed BHs and luminous active galactic nuclei (AGNs). However, no LRD had previously been spectroscopically confirmed at $z>10$, leaving this earliest phase observationally unexplored. Using JWST/NIRSpec spectroscopy from the EMBER program, we measure a spectroscopic redshift of $z_{\rm spec}=10.361^{+0.003}_{-0.002}$ for \target, the highest-redshift LRD candidate known to date. The redshift is constrained by a prominent Ly$α$ break and multiple tentative emission lines, including C\,{\sc iv}\,$λ\lambda1549,1551$ and [O\,{\sc iii}]\,$\lambda4363$ detected at $S/N=3.9$ and $3.6$, respectively. Its extreme NIRCam-MIRI color of $m_{\rm F444W}-m_{\rm F770W}=1.82\pm0.1$, characteristic V-shaped continuum with a turnover near the Balmer limit, and continuum slopes of $β_{\rm UV}=-2.26^{+0.11}_{-0.11}$ and $β_{\rm opt}=1.17^{+0.74}_{-0.70}$ all support its LRD nature. A possible iron complex at $λ_{\rm rest}\sim0.24$--$0.25\,{\rm μm}$ and a possibly high $\log\left([{\rm O\,III]\,\lambda4363/\rm Hγ}\right)=0.17^{+0.24}_{-0.22}$ further support an AGN-like interpretation, as seen in previously known LRDs. Tentative detection of Ly$α$ emission may indicate enhanced Ly$α$ transmission at $z\sim10$. Our findings extend the observational frontier of BH growth into the seed-BH formation era, and upcoming MIRI spectroscopy will further establish the physical nature of the source.

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arXiv2026

The ALMA REBELS Survey: The [C II] Luminosity Function of UV-Selected Galaxies at $z\sim7$

Luminosity functions (LF) are some of the most basic quantities providing insights into galaxy evolution across cosmic time and enabling a direct comparison between observations and simulations. Here, we present the first [CII]158$μ$m LF at $z\sim7$ from a sizeable UV-selected ALMA sample. Our analysis makes use of 27 galaxies with significant [CII] emission line detections in the epoch of reionization from the REBELS (Reionization Era Bright Emission Line Survey) ALMA Large Program and its pilot programs. We used these line detections and similar from ALPINE to calibrate UV luminosity-$L_{\mathrm{[CII]}}$ and stellar mass-$L_{\mathrm{[CII]}}$ relations at $z\sim7$. Given the challenge in precisely defining a selection volume for the REBELS sample itself, we rely on published UV LF and stellar mass function (SMF) determinations at $z\sim7$ and three complementary approaches to derive the [CII] LF. The UV LF-based method provides a lower limit on the [CII] LF, due to its missing the most dust-obscured systems. Our SMF-based estimate yields a Schechter function with a characteristic luminosity of $L^*_{\mathrm{[CII]}}=10^{9.11^{+0.11}_{-0.27}} L_\odot$ and a steep faint-end slope. From $z\sim7$ to $z\sim5$, our inferred [CII] LF shows an evolution of +0.3 dex in normalisation and +0.1 dex in $L^*_{\mathrm{[CII]}}$. Our results indicate a general underprediction from models of the abundance of [CII] emitters at high-redshift and thus potentially the number densities of massive yet UV-faint systems implied by our SMF-based method. Additionally, they suggest that 63% of the star formation rate density occurs in massive [CII]-bright systems and that $\sim$60-90% of [CII] emitters at $z\sim7$ may be missed by bright UV selections. This highlights the importance of surveys focusing on especially massive, UV-faint sources at $z>6$.

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arXiv2026

The dawn of the first galaxies

Understanding how the first galaxies assembled their stellar mass at cosmic dawn is a central frontier of modern astrophysics. JWST has now revealed an unexpected population of ultraviolet-bright galaxies at z>10, whose intense emission points towards a rapid stellar mass growth that challenges current models of early galaxy assembly. Yet, the cold gas fueling this growth remains hidden: current ALMA sensitivity restricts routine detection to only the brightest ionized-gas tracers such as [OIII] 88$μ$m, while [CII] 158$μ$m, a key coolant and gas-mass proxy of the neutral interstellar medium (ISM), is undetected beyond $z\sim8$. This leaves fundamental questions unanswered: how quickly primeval galaxies gathered cold gas and turned it into stars; what physical conditions (density, temperature, radiation field) characterized their ISM; how fast metals and dust built up; and how feedback regulated early gas assembly. Only a transformational sub-millimeter facility like ALMA2040 can address these questions, enabling systematic surveys of [CII] in the first galaxies and providing a representative census of gas fractions and depletion times. A simulated galaxy at $z=11.3$ shows that ALMA2040 not only will detect, but also spatially resolve its merging cold-gas structure in [CII] on $\sim$200 pc scales in 5 hours (below 100 pc in 10 hours). ALMA2040 will also spectrally resolve multiple lines simultaneously, akin to integral-field spectroscopy, providing the key diagnostics needed to break density-metallicity-radiation-field degeneracies and map the multi-phase ISM of z>10 galaxies. The combination of dramatically increased line sensitivity and wide instantaneous bandwidth will push the search for the first galaxies out to the earliest cosmic times, with [OIII] detectable up to $z\sim20$. ALMA2040 will thus be transformative for understanding how the first galaxies assembled at cosmic dawn.

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arXiv2026

Resolving the Assembly of Disk Galaxies from the Epoch of Reionisation to Cosmic Noon

Most of the mass and angular momentum of today's disk galaxies assembled at $z>1$. Yet, it remains unclear how these galaxies acquired their gas, how their baryons and dark matter coevolved, and how feedback and radial gas transport shaped their disks. Addressing these gaps requires resolved observations of cold gas, which carries most of the mass and angular momentum involved in galaxy assembly. By resolving CO and [C II] at kpc scales, ALMA revealed a surprising population of rotation-dominated disks, even at $z>2$, exhibiting kinematic signatures consistent with spiral arms, bars, and tidal tails. Yet, these studies are limited to massive ($M_\star>10^{10.5}$ M$_\odot$) and highly star-forming (SFRs$\gtrsim 100$ M$_\odot$yr$^{-1}$) galaxies, the progenitors of today's most massive elliptical and disk galaxies. To understand how most present-day spirals (like the Milky Way) assembled, it is crucial to resolve their low-mass progenitors, which dominate the star-forming galaxy population by number at $z>1$. Achieving this goal demands a tenfold increase in line sensitivity and hence a next-generation sub-/millimetre facility: ALMA2040. This leap in sensitivity will enable routine resolved studies of hundreds of $M_\star>10^9$ M$_\odot$ galaxies, including those on and below the main sequence of star-forming galaxies, providing representative, statistical galaxy samples with sub-kpc constraints on the cold gas kinematics and morphology. By uniquely providing resolved CO, [C I], and [C II] observations across $z=1-6$, ALMA2040 will trace a much larger fraction of the cold-gas reservoir than is accessible today, extending resolved studies from rare massive and/or lensed systems to representative galaxy populations. In this way, ALMA2040 will transform our understanding of how galaxy disks formed and evolved.

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arXiv2026

Dust at cosmic dawn: unveiling the onset of dust and obscured star formation at $z\gtrsim8$

Although less than 1 percent of the baryonic mass budget of a galaxy, cosmic dust profoundly alters the multi-wavelength appearance of galaxies across cosmic time. The (sub)millimeter wavelength regime is uniquely capable of weighing these dust reservoirs, and revealing the total extent of galaxy evolution that remains hidden behind them. With current facilities, however, doing so at $z > 8$ is largely out of reach. ALMA2040, a next-generation (sub)millimeter interferometer, is set to change this. Through an order-of-magnitude increase in sensitivity compared to ALMA, ALMA2040 is a transformational facility that will be able to routinely detect dust emission from galaxies at $z > 8$ and, through simultaneous multi-band characterization, accurately measure their dust masses, temperatures, and infrared luminosities. Combined with ancillary metallicity measurements -- including from the far-infrared lines detected by ALMA2040 itself -- this will establish the relative roles of supernovae and grain growth in building up dust in the earliest galaxies. Simultaneously, ALMA2040 will measure the fraction of star formation that is obscured by dust at cosmic dawn, and thereby the extent to which rest-UV and optical surveys miss early galaxy build-up. Without a 10$\times$ upgrade to ALMA -- comparable to the leap from the VLT to the ELT -- we will not be able to capitalize on the momentous advances enabled by JWST, and will remain blind to the cold and obscured component of galaxy formation in the $z > 8$ Universe.

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arXiv2026

Probing cold gas and dust in quiescent galaxies across cosmic time

The discovery of massive quiescent galaxies at high redshift by JWST has revealed that star formation can cease rapidly in the early Universe, yet the physical mechanisms responsible for quenching remain unknown. A key missing element is the systematic measurement in statistically representative quiescent samples of the cold gas and dust content, which are crucial for distinguishing quenching mechanisms and evolutionary pathways. Such observations are currently not feasible because state-of-the-art sub-millimeter facilities (e.g., ALMA) cannot routinely detect the faint molecular gas and dust reservoirs of quiescent galaxies, nor pinpoint outflowing molecular gas. A next-generation facility (ALMA2040) capable of providing transformative access to the cold interstellar medium of quiescent galaxies across redshift is therefore essential. In particular, it will allow the community to probe the molecular gas content of quiescent galaxies at cosmic noon and beyond by targeting the CO, [CI], and [CII] emission lines, as well as unveiling the physical conditions of the cold interstellar medium by constraining the CO spectral line energy distribution. It will also reveal the dust content of the passive population, a crucial ingredient to constrain the different quenching mechanisms. Finally, it will enable probing the molecular gas kinematics and identify molecular outflows driven by supermassive black holes. When combined with the rich legacy of JWST, ELT, and SKAO surveys, ALMA2040 will deliver a comprehensive, multi-phase view of feedback and quenching, allowing us to establish when, how, and why galaxies shut down their star formation across cosmic time.

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arXiv2026

ALMA2040: The High-Redshift Circumgalactic Medium. Imaging the fueling and feedback of galaxies in the early universe

Galaxies do not form in isolation, but rather as part of a wider interconnected web mediated at their interface by an extended gaseous atmosphere - the Circum-Galactic Medium (CGM). This dynamic and multiphase region is fed and shaped by gas inflows and mergers from the intergalactic medium and by feedback-driven outflows and radiation from the central galaxy. The CGM is imprinted by the past, present and future evolution of its central galaxy and environment. The cool atomic and molecular phases are of particular interest as they dominate the mass budget of outflows and provide a reservoir of direct star forming fuel for the galaxy to accrete. In the early universe where accretion rates, mergers, and feedback processes peak, the cycle of gas through the CGM is most vigorous. Sub-mm observations have detected cold gas in extended halos and gas flows around high redshift galaxies but are thus far limited to the most massive, extreme or gravitationally lensed sources, using just a handful of the strongest emission and absorption lines. A significant increase ($5-10\times$) in spectral line sensitivity compared with the current ALMA is needed to push physical scales, densities and properties to a new regime. We present three key scientific cases for an ALMA2040 telescope: (i) direct imaging of extended [CII]-traced CGM halos around Milky-Way-progenitor galaxies at $z=4$-8; (ii) resolved detection of cold, clumpy outflows on $\sim$100 pc scales tied to individual star-forming clumps; and (iii) multi-species/-transition emission and absorption diagnostics that jointly constrain the density, chemistry, and radiation fields permeating the cool CGM and its multiphase gas flows.

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arXiv2026

ALMA2040: Mapping the Spatially Resolved Dust and Star Formation Physics Driving High-z Galaxy Assembly

Interstellar dust reprocesses approximately half of the starlight emitted across cosmic history. However, dust temperature, which is essential to convert continuum flux into dust mass, molecular gas mass, and obscured star-formation rates, remains largely unconstrained on sub-galactic scales at high redshift. While single-band ALMA imaging has characterized continuum sizes for hundreds of z>1 galaxies, single-frequency measurements cannot separate the dust mass column from the local dust heating. To date, spatially resolved (<0.5-arcsec) multi-band dust temperatures exist in the literature for only ~10 extreme systems (quasars, hyperluminous starbursts, or strongly lensed galaxies) at z>1, with ongoing programs within a few years adding at most a few dozen submillimeter or UV-bright galaxies. This still leaves typical main-sequence disks largely unexplored across cosmic history. With an anticipated ~30 times improvement in continuum sensitivity (compared to the current ALMA), simultaneous multi-band receivers, and (sub-)kpc angular resolution, ALMA2040 will transform resolved dust thermometry into a systematic survey science. Here, we present the scientific rationale and technical requirements, highlighting a future statistically meaningful survey with > 100 representative main-sequence galaxies across cosmic epochs. Realistic visibility simulations demonstrate that ALMA2040 measures radial temperature gradients with ~0.5-4 K precision (L_IR~10^{12} L_sun in 2 h on-source at z~2). These measurements will break the degeneracy between intrinsic compactness and temperature gradients, deliver the first extinction-free, temperature-calibrated resolved star-formation relations, and uniquely trace radiative feedback and disk maturation from cosmic noon to cosmic dawn.

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arXiv2026

Has JWST Seen Everything? Hunting for "NIRCam-dark" Dusty Star-Forming Galaxies at $z \simeq 6 - 9$ with ALMA2040

JWST/NIRCam has recovered the stellar counterparts of many ALMA-detected, formerly HST-dark galaxies, yet ALMA has started identifying dusty star-forming galaxies (DSFGs) at $z>6$ that remain extremely faint or undetected even with NIRCam. These "NIRCam-dark" DSFGs may trace a missing rapid-growth phase connecting UV-luminous galaxies at $z>10$ to massive quiescent galaxies at $z\gtrsim4$. So far, the small, heterogeneously selected NIRCam-dark sample is insufficient to determine their abundance or role in the evolution of massive galaxies. We show that a blind 1.3-mm continuum survey with ALMA2040 can provide the first high-significance census of this elusive NIRCam-dark DSFG population across $z\simeq 6 - 9$. We conduct sensitivity and survey-speed calculations requiring a $10σ$ detection of a NIRCam-dark DSFG with a dust-obscured star-formation rate of $60\,M_\odot\,{\rm yr}^{-1}$ at $z = 8$. At a like-for-like 7.5-GHz normalization, ALMA2040 will reach the required 1.3-mm RMS of $21\,μ$Jy beam$^{-1}$ about 90 times faster than current ALMA. With 100 hr on-source, ALMA2040 can cover an area of $\sim0.5$ deg$^2$ and detect $\langle N \rangle\sim16$ NIRCam-dark DSFGs over $7.5 10$ and the rapid emergence of massive quiescent systems at $z\gtrsim 4$.

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arXiv2026

ALMA2040: Understanding the Early Assembly of Galaxies - The Formation of Star-Forming Clumps and their Role in Shaping Galaxy Evolution

Astrophysics seeks to explain how galaxies form and evolve through the interplay of stars, gas, and dust. Giant molecular clouds (GMCs), the main reservoirs and sites of star formation, link the cold interstellar medium to the birth of stars and stellar structures. Their properties reflect galactic disk conditions, and their evolution is shaped by stellar feedback and host-galaxy dynamics. Studying GMCs across cosmic time is therefore key to understanding how gas turns into stars and drives galaxy evolution. Hubble Space Telescope and James Webb Space Telescope observations reveal compact star-forming clumps in galaxies from Cosmic Noon to the Epoch of Reionization ($z\approx6$), but their link to the molecular gas reservoir is still unclear. We do not yet know how GMC properties vary with redshift and environment, how molecular gas, dust, and young stars are arranged, or whether clumps form in unstable disks or disturbed systems. Addressing these questions requires spatially resolved observations of the cold interstellar medium at the scales probed by optical/near-infrared facilities. ALMA2040, a transformational next-generation sub-mm facility, will provide the sensitivity and angular resolution needed to detect individual GMCs in representative lensed and unlensed galaxies at $z>1$. CO and [CII], complemented by dust continuum and molecular-gas kinematics, will measure the molecular gas reservoir, its physical conditions, and its dynamical state. Together with JWST and the ELT, ALMA2040 will connect cold gas, dust, and stellar structures across cosmic time. ALMA2040 will revolutionize our understanding of (i) the properties and evolution of GMCs and their connection to star-forming clumps, (ii) the spatial interplay between molecular gas, dust, and young stars, and (iii) the dynamics, survival, and formation of GMCs and stellar clumps.

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arXiv2026

What fuels the growth of stars and black holes in galaxies through cosmic time? The physics and chemistry of the interstellar medium in distant galaxies

The interplay between the baryonic matter in galaxies (gas, dust, stars) has a fundamental role in our understanding of galaxy formation and evolution through cosmic time. The (sub)mm regime provides a unique window to measure the physical conditions and chemistry in the cold and dusty gas reservoirs that fuel the formation of new stars and the growth of massive black holes in distant galaxies. Large sub(mm) interferometers have made a revolutionary impact mapping the cold gas and dust in galaxies beyond the local universe. However, significant progress is hampered by limited spectral-line sensitivity. After more than a decade of surveys, molecular gas (traced by 12CO) has been measured only in a few tens of typical, massive main-sequence star-forming galaxies at z>1, while access to fainter gas-tracing species has been limited to only the very brightest galaxies. Thereby it restricts access to the detailed conditions in the cold gas clouds in typical galaxies in the distant universe. A revolutionary, flagship sub-mm interferometer with a massive increase in instantaneous spectral line sensitivity and broad spectral grasp (ALMA2040) fills this gap by enabling rich, multi-transition, multi-species and multi-isotopologue studies of the atomic and molecular interstellar medium for thousands of typical galaxies across galaxy populations and redshift. This will unveil how the ISM evolves across the galaxy population for statistical samples in different redshift bins, detailed studies of the physical conditions and chemistry in the multi-phase interstellar medium of typical galaxies, and how the cold ISM regulates and responds to star- and black-hole formation, providing a tremendous leap forward in the study of galaxy assembly over cosmic time.

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arXiv2026

Unveiling the Baryon Cycle Through Cosmic Time

Galaxy evolution is governed by the baryon cycle: gas accreted from the cosmic web and circumgalactic medium condenses into molecular gas, forms stars, and is redistributed by stellar and AGN feedback. Tracing the molecular phase is therefore essential to understanding how galaxies acquire, consume, and eject their baryons. Yet current molecular-gas surveys remain limited by sensitivity, area, cosmic variance, and spectral bandwidth. ALMA2040 would combine a $\sim10\times$ sensitivity improvement with $\gtrsim512$ GHz simultaneous frequency coverage, delivering $\sim100\times$ faster mapping at fixed depth and a further $\gtrsim25\times$ gain in instantaneous bandwidth. Together, these advances would increase spectroscopic survey speed by orders of magnitude, enabling tiered ``wedding-cake'' strategies: an ultra-deep $\sim4$-5 arcmin$^2$ field probing faint and high-redshift reservoirs, a $\sim$0.25 deg$^2$ survey reaching molecular-line sensitivities comparable to current ultra-deep fields over a much larger cosmological volume, and thousands of independent pointings minimizing cosmic variance. Broad spectral coverage would simultaneously detect multiple CO transitions, [CI], H$_2$O, feedback tracers, far-IR fine-structure lines, and dust continuum, constraining molecular gas, ISM conditions, obscured star formation, and gas flows within the same observations. Every targeted observation would also become a molecular deep field, extending these measurements to serendipitous galaxies. Together with future HI, optical, and near-IR surveys, ALMA2040 would enable a population-resolved view of the baryon cycle across cosmic time and stringent tests of galaxy formation models.

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arXiv2026

COSMOS-3D: Diverse Environments and Hot-dust Signatures among Dusty Star-forming Galaxies at $z$ = 4.9-7.2

Dusty star-forming galaxies (DSFGs) are expected to trace early massive-halo assembly, but the connection between dust-obscured star formation, morphology, hot dust, and environment remains unclear at $z$>4. We combine JWST/NIRCam F444W grism spectroscopy from COSMOS-3D with MIRI F1000W/F2100W imaging and a mixed ALMA-selected and ALMA-followed dusty-galaxy sample from CRISTAL, CHAMPS, REBELS, and A3COSMOS to study 18 DSFGs or DSFG candidates at z=4.9-7.2. We compare their environments with the parent spectroscopically confirmed emission-line sample and the COSMOS-Web photo-z galaxy sample using separate and combined overdensity estimators. The parent narrow-line H$α$ sample has a median observed, dust-uncorrected ${\rm SFR}_{\rm Hα}=11.7 M_\odot~{\rm yr^{-1}}$. Within R=0.5 pMpc, DSFGs have a median $δ_{\rm spec+phot}=0.92^{+0.06}_{-0.16}$, compared with $0.80^{+0.05}_{-0.04}$ for HAEs, with a stronger contrast on smaller scales. The strongest compact overdensities are associated with merger/interacting morphology: merging DSFGs reach $δ_{\rm spec+phot}=4.70^{+1.61}_{-1.51}$ within R=0.5 pMpc. In contrast, MIRI-bright DSFGs do not show an enhanced number of nearby visible H$α$-emitting companions, and their F2100W fluxes are difficult to explain with the 3.3 $μ$m PAH feature alone, suggesting an additional hot-dust component. These results are consistent with a possible phase-dependent picture in which the compact line-emitter core, merger-driven dusty phase, and MIRI-bright hot-dust phase need not be spatially or temporally identical during early structure growth.

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arXiv2026

CHAMPS: The COSMOS High-Redshift ALMA-MIRI Population Survey - A New Census of the Dusty Early Universe

Understanding how dust forms and evolves over cosmic time is a key open problem in extragalactic astrophysics. Galaxies in the early Universe were once thought to be mostly dust-poor, but recent discoveries of heavily dust-obscured galaxies near the Epoch of Reionization challenge models of early dust production and raise new questions about the true cosmic star formation rate density. In this paper, we present the COSMOS High-Redshift ALMA-MIRI Population Survey (CHAMPS), which sheds light on the dusty early universe at z>4. CHAMPS is a new 144h ALMA 1.2mm (band 6) large program mapping the combined JWST/NIRCam+MIRI footprint in the COSMOS field. It covers 0.2deg2 with a synthesized beam size of 1.1" and a sensitivity of 0.14mJy/beam. It is complemented, alongside JWST, by ancillary X-ray, UV, optical, sub-mm, and radio data. CHAMPS, optimized as a blind survey, detects above 5$σ$ approximately 385 individual dusty high-redshift sub-mm sources, 68 dusty AGN, and a dozen dusty galaxies at z>6. The galaxies are largely not detected in JWST/F150W, making them prototypical near-IR dark galaxies. We showcase three of the highest-redshift most dusty and massive candidate galaxies detected in CHAMPS with redshifts up to z=7.5. CHAMPS also enables stacks of thousands of galaxies grouped in bins of various physical parameters. Its sub-mm coverage of dust-attenuated JWST-identified galaxies provides robust constraints on dust masses and obscured star formation rates to study early dust formation and evolution. In addition, CHAMPS enables a blind search for luminous CO line emitters at z=0.4-2.7 and [CII]158$μ$m emitters at z=6.7.

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arXiv2026

CHAMPS: Data Reduction and Detection of ~3300 Dusty Galaxies at 1.2 mm

We present the reduction and source catalogs for the \textit{COSMOS High-$z$ ALMA-MIRI Population Survey} (CHAMPS), the largest Atacama Large (Sub)Millimeter Array (ALMA) blank field survey to date at 0.2\,deg$^2$. With observing frequency centered at $250\, $GHz ($1.2\,$mm) and bandwidth of 7.5 GHz, CHAMPS covers the JWST/NIRCam+MIRI footprint in the COSMOS field, taking advantage of the rich, multiwavelength ancillary datasets in COSMOS ranging from X-ray to radio. The majority of the CHAMPS survey (90$\%$) has depths at or below 200 $μ$Jy beam$^{-1}$ and with an average RMS of 146 $μ$Jy beam$^{-1}$. The reduced CHAMPS mosaic has a beam size of $θ_{\rm res} = 1.1'' \times 1.1''$. CHAMPS identifies sources via two detection methods, a blind search for high-SNR sources, and a prior-based search involving MIRI detections to identify faint sources. The blind search yields a total of 595 sources down to an SNR $\ge4.5σ$ while the prior catalog yields a total of 3162 source down to an SNR $\ge3σ$, leading to a full sample of 3355 unique objects detected across both catalogs. We identify a unique population of 385 SNR $\ge5σ$ sources across the two catalogs; after excluding 9 likely spurious edge detections we define a robust science sample of 376 sources above $\ge5σ$. These sources have a median redshift of $\langle z_{1.2 \text{ mm}}\rangle = 2.54^{+0.89}_{-1.69}$ based on optical/near-IR/mid-IR photometric redshifts and high-quality spectroscopic redshifts, and hold a median stellar mass of $\langle\log (\rm M_\star/M_\odot)\rangle = 10.79^{+0.42}_{-3.08}$. We have further identified 68/376 ($\sim18\%$) sources as candidate AGN through X-ray, UV-optical, infrared and radio selection techniques.

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arXiv2026

PAHSPECS: JWST/MIRI Spectroscopy of PAHs at Cosmic Noon

The physical conditions of the interstellar medium (ISM) are thought to differ greatly at high redshifts compared to local galaxies. Polycyclic aromatic hydrocarbons (PAHs) are key ISM constituents, mediating the heating and cooling of gas in photo-dissociation regions. However, PAHs are unexplored in main-sequence (MS) galaxies at z~1-2 (cosmic noon), limiting our view of the ISM's thermal and chemical balance. We present the PAH Spectroscopic Survey (PAHSPECS) JWST program, the first MIRI/MRS survey of the 3.3, 6.2, 7.7, 8.6 and 11.3$μ$m PAH features in MS galaxies at z~1. The five targets come from the deep ALMA CO and continuum flux-limited sample in the HUDF. We detect the 6.2, 7.7 and 11.3$μ$m PAHs in all galaxies, and the 3.3$μ$m feature in only two. Spectral energy distribution (SED) fitting to broad-band mid-IR photometry recovers the 6.2 and 7.7$μ$m PAH luminosities derived from spectral decomposition of the MRS spectra to within ~25% accuracy. However, the 3.3 and 11.3$μ$m features are overestimated by ~50% (up to 3-5x). Spatially resolved maps of ASPECS-6, the most extended source, show variations of the 7.7$μ$m PAH contribution to the MIRI F1500W flux, suggesting that while photometry can infer PAH luminosity accurately, IFU spectroscopy is necessary to study variations in PAH ratios and characterize galaxy dust properties. The PAH fraction of the total dust mass from photometric SED modeling roughly agrees with the $L_{\rm PAH}/L_{\rm IR}$ ratio measured from spectroscopy, but the correlation is not as tight as models predict. On average, PAHSPECS galaxies show an excess in 6.2$μ$m equivalent width relative to nearby dusty luminous systems, but lower 3.3$μ$m equivalent widths than local systems, similar to higher-mass starbursts at z~1-3. This points to differential changes in the size distributions of neutral and ionized PAHs in cosmic noon galaxies.

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