arXiv subjects

Sirio Belli

Publications and source records attributed to Sirio Belli.

At least 37 records · Page 2Linked to original sources

arXiv2025

Stripped and Enriched: The Role of Ram-Pressure in Shaping Chemical Enrichment of Galaxies at Intermediate Redshift

The chemical evolution of galaxies is shaped by their star formation histories and the exchange of gas with their environments. Metallicity provides key insights into these processes, reflecting the interplay between star formation and gas flows. A fundamental aspect of this evolution is the mass-metallicity relation, which captures the strong correlation between a galaxy stellar mass ($M_\star$) and its gas-phase oxygen abundance. In this study, we use MUSE observations to analyze star-forming disc galaxies in 12 clusters within the redshift range $0.3 < z < 0.5$. Galaxies were classified into three groups: ram-pressure stripping (RPS), control cluster, and control field. For the first time, we investigate the impact of RPS on gas-phase metallicities across a wide mass range of galaxies at intermediate redshift, comparing RPS galaxies to counterparts in both cluster and field environments. By analyzing the integrated flux within galactic disks, our results reveal that, on average, RPS induces a metallicity enhancement of 0.2 dex over non-stripped galaxies. Contrary to the prevailing view that cluster membership alone drives metallicity enrichment, we find that control cluster galaxies exhibit metallicities comparable to field galaxies at a given $M_\star$, with only RPS galaxies displaying significantly higher metal content, highlighting the unique role of RPS in shaping the chemical properties of galaxies. These differences become more pronounced at lower $M_\star$, indicating that environmental influences play a more critical role in shaping the chemical evolution of lower-mass galaxies. Our findings suggest that both enhanced star formation rates and suppressed gas inflows -- consequences of ram pressure stripping -- drive the elevated metallicity observed in RPS galaxies.

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arXiv2025

A "Black Hole Star" Reveals the Remarkable Gas-Enshrouded Hearts of the Little Red Dots

The physical processes that led to the formation of billion solar mass black holes within the first 700 million years of cosmic time remain a puzzle. Several theoretical scenarios have been proposed to seed and rapidly grow black holes, but direct observations of these mechanisms remain elusive. Here we present a source 660 million years after the Big Bang that displays singular properties: among the largest Hydrogen Balmer breaks reported at any redshift, broad multi-peaked H$β$ emission, and Balmer line absorption in multiple transitions. We model this source as a "black hole star" (BH*) where the Balmer break and absorption features are a result of extremely dense, turbulent gas forming a dust-free "atmosphere" around a supermassive black hole. This source may provide evidence of an early black hole embedded in dense gas -- a theoretical configuration proposed to rapidly grow black holes via super-Eddington accretion. Radiation from the BH* appears to dominate almost all observed light, leaving limited room for contribution from its host galaxy. We demonstrate that the recently discovered "Little Red Dots" (LRDs) with perplexing spectral energy distributions can be explained as BH*s embedded in relatively brighter host galaxies. This source provides evidence that black hole masses in the LRDs may be over-estimated by orders of magnitude -- the BH* is effectively dust-free contrary to the steep dust corrections applied while modeling LRDs, and the physics that gives rise to the complex line shapes and luminosities may deviate from assumptions underlying standard scaling relations.

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arXiv2025

AGN Feedback in Quiescent Galaxies at Cosmic Noon Traced by Ionized Gas Emission

We analyze ionized gas emission lines in deep rest-frame optical spectra of 16 quiescent galaxies at redshift $1.7<z<3.5$ observed with JWST/NIRSpec by the Blue Jay survey. Robust detection of emission lines in $75\%$ of the sample indicates the presence of ongoing ionizing sources in this passive population. The H$α$ line luminosities confirm that the population is quiescent, with star formation rates that are at least ten times lower than the main sequence of star formation. The quiescent sample is clearly separate from the star-forming population in line diagnostic diagrams, and occupies a region usually populated by active galactic nuclei (AGN). Analysis of the observed line ratios, equivalent widths, and velocity dispersions leads us to conclude that in most cases the gas is ionized by AGN activity, despite the lack of X-ray detections. A subset of the sample also hosts ionized and/or neutral outflows. Our results show, for the first time using a representative sample, that low luminosity AGN are extremely common among quiescent galaxies at high redshift. These low luminosity AGN may play a key role in quenching star formation and in maintaining massive galaxies quiescent from Cosmic Noon to $z\sim0$.

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arXiv2024

Rapid Quenching of Galaxies at Cosmic Noon

The existence of massive quiescent galaxies at high redshift seems to require rapid quenching, but it is unclear whether all quiescent galaxies have gone through this phase and what physical mechanisms are involved. To study rapid quenching, we use rest-frame colors to select 12 young quiescent galaxies at $z \sim 1.5$. From spectral energy distribution fitting, we find that they all experienced intense starbursts prior to rapid quenching. We confirm this with deep Magellan/FIRE spectroscopic observations for a subset of seven galaxies. Broad emission lines are detected for two galaxies and are most likely caused by AGN activity. The other five galaxies do not show any emission features, suggesting that gas has already been removed or depleted. Most of the rapidly quenched galaxies are more compact than normal quiescent galaxies, providing evidence for a central starburst in the recent past. We estimate an average transition time of $300\,\rm Myr$ for the rapid quenching phase. Approximately $4\%$ of quiescent galaxies at $z=1.5$ have gone through rapid quenching; this fraction increases to $23\%$ at $z=2.2$. We identify analogs in the TNG100 simulation and find that rapid quenching for these galaxies is driven by AGN, and for half of the cases, gas-rich major mergers seem to trigger the starburst. We conclude that these massive quiescent galaxies are not just rapidly quenched but also rapidly formed through a major starburst. We speculate that mergers drive gas inflow towards the central regions and grow supermassive black holes, leading to rapid quenching by AGN feedback.

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arXiv2024

Widespread rapid quenching at cosmic noon revealed by JWST deep spectroscopy

Massive quiescent galaxies in the young universe are expected to be quenched rapidly, but it is unclear whether they all experience starbursts before quenching and what physical mechanism drives rapid quenching. We study 14 massive quiescent galaxies ($\log(M_\star/M_\odot) > 10$) at $z\sim2$ selected from a representative sample of the Blue Jay survey. We reconstruct their star formation histories by fitting spectral energy distribution models to the JWST/NIRSpec $R\sim1000$ spectra. We find that massive quiescent galaxies can be split into three categories with roughly equal numbers of galaxies according to their SFHs: 1) Relatively old galaxies quenched at early epochs; 2) Galaxies that are rapidly and recently quenched after a flat or bursty formation history (depending on the assumed prior); 3) Galaxies that are rapidly and recently quenched after a major starburst. Most recently quenched galaxies show neutral gas outflows, probed by blueshifted $\rm Na\,I\,D$ absorption, and ionized gas emission, with line ratios consistent with active galactic nucleus (AGN) diagnostics. This suggests that AGN activity drives multi-phase gas outflows, leading to rapid quenching. By tracing back the SFHs of the entire sample, we predict the number density of massive quiescent galaxies at $z=4-6$: $n=(1.5-6.0)\times10^{-5}\,\rm Mpc^{-3}$. The two old massive quiescent galaxies in our sample appear to have extremely early formation and quenching ($z\gtrsim6$), possibly descendants of early post-starbursts at $z>3$. These galaxies still show neutral gas reservoirs and weak H$α$ emission, perhaps because the ejective AGN feedback that caused rapid quenching has weakened over time.

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arXiv2024

Star Formation Shut Down by Multiphase Gas Outflow in a Galaxy at a Redshift of 2.45

Large-scale outflows driven by supermassive black holes are thought to play a fundamental role in suppressing star formation in massive galaxies. However, direct observational evidence for this hypothesis is still lacking, particularly in the young universe where star formation quenching is remarkably rapid, thus requiring effective removal of gas as opposed to slow gas heating. While outflows of ionized gas are commonly detected in massive distant galaxies, the amount of ejected mass is too small to be able to suppress star formation. Gas ejection is expected to be more efficient in the neutral and molecular phases, but at high redshift these have only been observed in starbursts and quasars. Here we report JWST spectroscopy of a massive galaxy experiencing rapid quenching at redshift z=2.445. We detect a weak outflow of ionized gas and a powerful outflow of neutral gas, with a mass outflow rate that is sufficient to quench the star formation. Neither X-ray or radio activity are detected; however, the presence of a supermassive black hole is suggested by the properties of the ionized gas emission lines. We thus conclude that supermassive black holes are able to rapidly suppress star formation in massive galaxies by efficiently ejecting neutral gas.

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arXiv2024

Cue: A Fast and Flexible Photoionization Emulator for Modeling Nebular Emission Powered By Almost Any Ionizing Source

The complex physics governing nebular emission in galaxies, particularly in the early universe, often defy simple low-dimensional models. This has proven to be a significant barrier in understanding the (often diverse) ionizing sources powering this emission. We present Cue, a highly flexible tool for interpreting nebular emission across a wide range of abundances and ionizing conditions of galaxies at different redshifts. Unlike typical nebular models used to interpret extragalactic nebular emission, our model does not require a specific ionizing spectrum as a source, instead approximating the ionizing spectrum with a 4-part piece-wise power-law. We train a neural net emulator based on the CLOUDY photoionization modeling code and make self-consistent nebular continuum and line emission predictions. Along with the flexible ionizing spectra, we allow freedom in [O/H], [N/O], [C/O], gas density, and total ionizing photon budget. This flexibility allows us to either marginalize over or directly measure the incident ionizing radiation, thereby directly interrogating the source of the ionizing photons in distant galaxies via their nebular emission. Our emulator demonstrates a high accuracy, with $\sim$1% uncertainty in predicting the nebular continuum and $\sim$5% uncertainty in the emission lines. Mock tests suggest Cue is well-calibrated and produces useful constraints on the ionizing spectra when $S/N (\mathrm{H}_α) \gtrsim 10$, and furthermore capable of distinguishing between the ionizing spectra predicted by single and binary stellar models. The compute efficiency of neural networks facilitates future applications of Cue for rapid modeling of the nebular emission in large samples and Monte Carlo sampling techniques.

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arXiv2024

JWST Reveals Widespread AGN-Driven Neutral Gas Outflows in Massive z ~ 2 Galaxies

We use deep JWST/NIRSpec R~1000 slit spectra of 113 galaxies at 1.7 < z < 3.5, selected from the mass-complete Blue Jay survey, to investigate the prevalence and typical properties of neutral gas outflows at cosmic noon. We detect excess Na I D absorption (beyond the stellar contribution) in 46% of massive galaxies ($\log$ M$_*$/M$_\odot >$ 10), with similar incidence rates in star-forming and quenching systems. Half of the absorption profiles are blueshifted by at least 100 km/s, providing unambiguous evidence for neutral gas outflows. Galaxies with strong Na I D absorption are distinguished by enhanced emission line ratios consistent with AGN ionization. We conservatively measure mass outflow rates of 3 - 100 $M_\odot$ yr$^{-1}$; comparable to or exceeding ionized gas outflow rates measured for galaxies at similar stellar mass and redshift. The outflows from the quenching systems (log(sSFR)[yr$^{-1}$] $\lesssim$ -10) have mass loading factors of 4 - 360, and the energy and momentum outflow rates exceed the expected injection rates from supernova explosions, suggesting that these galaxies could possibly be caught in a rapid blowout phase powered by the AGN. Our findings suggest that AGN-driven ejection of cold gas may be a dominant mechanism for fast quenching of star formation at z~2.

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arXiv2023

Observational Signatures of AGN Feedback in the Morphology and the Ionization States of Milky Way-like Galaxies

We make an in-depth analysis of different AGN jet models' signatures, inducing quiescence in galaxies with a halo mass of $10^{12} M_\odot$. Three jet models, including cosmic ray-dominant, hot thermal, and precessing kinetic jets, are studied at two energy flux levels each, compared to a jet-free, stellar feedback-only simulation. We examine the distribution of Mg II, O VI, and O VIII ions, alongside gas temperature and density profiles. Low-energy ions, like Mg II, concentrate in the ISM, while higher energy ions, e.g., O VIII, prevail at the AGN jet cocoon's edge. High-energy flux jets display an isotropic ion distribution with lower overall density. High-energy thermal or cosmic ray jets pressurize at smaller radii, significantly suppressing core density. The cosmic ray jet provides extra pressure support, extending cool and warm gas distribution. A break in the ion-to-mass ratio slope in O VI and O VIII is demonstrated in the ISM-to-CGM transition (between 10-30 kpc), growing smoothly towards the CGM at greater distances.

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arXiv2023

Detection of Accretion Shelves Out to the Virial Radius of a Low-Mass Galaxy with JWST

We report the serendipitous discovery of an extended stellar halo surrounding the low-mass galaxy Ark 227 ($M_\ast=5\times10^9 M_\odot$; d=35 Mpc) in deep JWST NIRCam imaging from the Blue Jay Survey. The F200W-F444W color provides robust star-galaxy separation, enabling the identification of stars at very low density. By combining resolved stars at large galactocentric distances with diffuse emission from NIRCam and Dragonfly imaging at smaller distances, we trace the surface brightness and color profiles of this galaxy over the entire extent of its predicted dark matter halo, from 0.1-100 kpc. Controlled N-body simulations have predicted that minor mergers create "accretion shelves" in the surface brightness profile at large radius. We observe such a feature in Ark 227 at 10-20 kpc, which, according to models, could be caused by a merger with total mass ratio 1:10. The metallicity declines over this radial range, further supporting the minor merger scenario. There is tentative evidence of a second shelf at $μ_V\approx 35$ mag arcsec$^{-2}$ extending from 50-100 kpc, along with a corresponding drop in metallicity. The stellar mass in this outermost envelope is $\approx10^7M_\odot$. These results suggest that Ark 227 experienced multiple mergers with a spectrum of lower-mass galaxies -- a scenario that is broadly consistent with the hierarchical growth of structure in a cold dark matter-dominated universe. Finally, we identify an ultra-faint dwarf associated with Ark 227 with $M_\ast\approx10^5 M_\odot$ and $μ_{V,e}=28.1$ mag arcsec$^{-2}$, demonstrating that JWST is capable of detecting very low-mass dwarfs to distances of at least ~30 Mpc.

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arXiv2023

The Stellar Chemical Abundances of Simulated Massive Galaxies at $z = 2$

We analyze the stellar abundances of massive galaxies ($\log M_\ast/M_\odot>10.5$) at $z=2$ in the IllustrisTNG simulation with the goal of guiding the interpretation of current and future observations, particularly from the James Webb Space Telescope. We find that the effective size, $R_e$, of galaxies strongly affects the abundance measurements: both [Mg/H] and [Fe/H] are anti-correlated with $R_e$, while the relative abundance [Mg/Fe] slightly increases with $R_e$. The $α$ enhancement as tracked by [Mg/Fe] traces the formation timescale of a galaxy weakly, and mostly depends on $R_e$. Aperture effects are important: measuring the stellar abundances within 1~kpc instead of within $R_e$ can make a large difference. These results are all due to a nearly universal, steeply declining stellar abundance profile that does not scale with galaxy size -- small galaxies appear metal-rich because their stars live in the inner part of the profile where abundances are high. The slope of this profile is mostly set by the gas-phase abundance profile and not substantially modified by stellar age gradients. The gas-phase abundance profile, in turn, is determined by the strong radial dependence of the gas fraction and star formation efficiency. We develop a simple model to describe the chemical enrichment, in which each radial bin of a galaxy is treated as an independent closed-box system. This model reproduces the gas-phase abundance profile of simulated galaxies, but not the detailed distribution of their stellar abundances, for which gas and/or metal transport are likely needed.

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arXiv2023

Detecting and Characterizing Young Quasars. III. The Impact of Gravitational Lensing Magnification

We test the impact of gravitational lensing on the lifetime estimates of seven high-redshift quasars at redshift $z\gtrsim6$. The targeted quasars are identified by their small observed proximity zone sizes, which indicate extremely short quasar lifetimes $(t_Q\lesssim10^5 \text{ yrs})$. However, these estimates of quasar lifetimes rely on the assumption that the observed luminosities of the quasars are intrinsic and not magnified by gravitational lensing, which would bias the lifetime estimates towards younger ages. In order to test possible effects of gravitational lensing, we obtain high-resolution images of the seven quasars with the {\em Hubble Space Telescope (HST)} and look for signs of strong lensing. We do not find any evidence of strong lensing, i.e., all quasars are well-described by point sources, and no foreground lensing galaxy is detected. We estimate that the strong lensing probabilities for these quasars are extremely small $(\sim1.4\times10^{-5})$, and show that weak lensing changes the estimated quasar lifetimes by only $\lesssim0.2$ dex. We thus confirm that the short lifetimes of these quasars are intrinsic. The existence of young quasars indicates a high obscured fraction, radiatively inefficient accretion, and/or flickering light curves for high-redshift quasars. We further discuss the impact of lensing magnification on measurements of black hole masses and Eddington ratios of quasars.

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arXiv2022

Schrodinger's Galaxy Candidate: Puzzlingly Luminous at $z\approx17$, or Dusty/Quenched at $z\approx5$?

$JWST$'s first glimpse of the $z>10$ Universe has yielded a surprising abundance of luminous galaxy candidates. Here we present the most extreme of these systems: CEERS-1749. Based on $0.6-5μ$m photometry, this strikingly luminous ($\approx$26 mag) galaxy appears to lie at $z\approx17$. This would make it an $M_{\rm{UV}}\approx-22$, $M_{\rm{\star}}\approx5\times10^{9}M_{\rm{\odot}}$ system that formed a mere $\sim220$ Myrs after the Big Bang. The implied number density of this galaxy and its analogues challenges virtually every early galaxy evolution model that assumes $Λ$CDM cosmology. However, there is strong environmental evidence supporting a secondary redshift solution of $z\approx5$: all three of the galaxy's nearest neighbors at $<2.5$" have photometric redshifts of $z\approx5$. Further, we show that CEERS-1749 may lie in a $z\approx5$ protocluster that is $\gtrsim5\times$ overdense compared to the field. Intense line emission at $z\approx5$ from a quiescent galaxy harboring ionized gas, or from a dusty starburst, may provide satisfactory explanations for CEERS-1749's photometry. The emission lines at $z\approx5$ conspire to boost the $>2μ$m photometry, producing an apparent blue slope as well as a strong break in the SED. Such a perfectly disguised contaminant is possible only in a narrow redshift window ($Δz\lesssim0.1$), implying that the permitted volume for such interlopers may not be a major concern for $z>10$ searches, particularly when medium-bands are deployed. If CEERS-1749 is confirmed to lie at $z\approx5$, it will be the highest-redshift quiescent galaxy, or one of the lowest mass dusty galaxies of the early Universe detected to-date. Both redshift solutions of this intriguing galaxy hold the potential to challenge existing models of early galaxy evolution, making spectroscopic follow-up of this source critical.

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arXiv2022

Constraining the cosmic-ray ionization rate and their spectrum with NIR spectroscopy of dense clouds -- A test-bed for JWST

Low-energy cosmic-rays (CRs) control the thermo-chemical state and the coupling between gas and magnetic fields in dense molecular clouds, the sites of star-formation. However, current estimates of the low-energy CR spectrum ($E \lesssim 1$ GeV) and the associated CR ionization rate are highly uncertain. We apply, for the first time, a new method for constraining the CR ionization rate and the CR spectral shape using H$_2$ rovibrational lines from cold molecular clouds. Using the MMIRS instrument on the MMT, we obtained deep near-infrared (NIR) spectra in six positions within four dense cores, G150, G157, G163, G198, with column densities $N_{\rm H_2} \approx 10^{22}$ cm$^{-2}$. We derive 3$σ$ upper limits on the H$_2$ $(1-0)$S(0) line (2.22 $μ$m) brightness in the range $I = 5.9 \times 10^{-8}$ to $1.2 \times 10^{-7}$ erg cm$^{-2}$ s$^{-1}$ sr$^{-1}$ for the different targets. Using both an analytic model and a numerical model of CR propagation, we convert these into upper limits on the CR ionization rate in the clouds' interior, $ζ= 1.5$ to $3.6 \times 10^{-16}$ s$^{-1}$, and lower limits on the low-energy spectral slope of interstellar CR protons, $α= -0.97$ to $-0.79$. We show that while MMT was unable to detect the H$_2$ lines due to high atmospheric noise, JWST/NIRSpec will be able to efficiently detect the CR-excited H$_2$ lines, making it the ideal method for constraining the otherwise elusive low-energy CRs, shedding light on the sources and propagation modes of CRs.

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arXiv2021

Reproducing the UVJ Color Distribution of Star-forming Galaxies at 0.5 < z < 2.5 with a Geometric Model of Dust Attenuation

We analyze the distribution of rest-frame U-V and V-J colors for star-forming galaxies at 0.5 < z < 2.5. Using stellar population synthesis, stochastic star formation histories, and a simple prescription for the dust attenuation that accounts for the shape and inclination of galaxies, we construct a model for the distribution of galaxy colors. With only two free parameters, this model is able to reproduce the observed galaxy colors as a function of redshift and stellar mass remarkably well. Our analysis suggests that the wide range of dust attenuation values measured for star-forming galaxies at a given redshift and stellar mass is almost entirely due to the effect of inclination; if all galaxies were observed edge-on, they would show very similar dust attenuation. This result has important implications for the interpretation of dust attenuation measurements, the treatment of UV and IR luminosity, and the comparison between numerical simulations and observations.

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arXiv2021

Quenching, Mergers and Age Profiles for z=2 Galaxies in IllustrisTNG

Using the IllustrisTNG cosmological galaxy formation simulations, we analyze the physical properties of young quiescent galaxies at z=2 with stellar masses above 10^10.5 solar masses. This key population provides an unaltered probe into the evolution of galaxies from star-forming to quiescent and has been recently targeted by several observational studies. Young quiescent galaxies in the simulations do not appear unusually compact, in tension with observations, but they show unique age gradients that are qualitatively consistent with the observed color gradients. In particular, more than half of the simulated young quiescent galaxies show positive age profiles due to recent intense central starbursts, which are triggered by significant mergers. Yet, there is a sizable population of recently quenched galaxies without significant mergers and with flat age profiles. Our results suggest that mergers play a fundamental role in structural transformation, but are not the only available pathway to quench a z=2 galaxy.

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arXiv2021

The Diverse Molecular Gas Content of Massive Galaxies Undergoing Quenching at z~1

We present a detailed study of the molecular gas content and stellar population properties of three massive galaxies at 1 < z < 1.3 that are in different stages of quenching. The galaxies were selected to have a quiescent optical/near-infrared spectral energy distribution and a relatively bright emission at 24 micron, and show remarkably diverse properties. CO emission from each of the three galaxies is detected in deep NOEMA observations, allowing us to derive molecular gas fractions Mgas/Mstar of 13-23%. We also reconstruct the star formation histories by fitting models to the observed photometry and optical spectroscopy, finding evidence for recent rejuvenation in one object, slow quenching in another, and rapid quenching in the third system. To better constrain the quenching mechanism we explore the depletion times for our sample and other similar samples at z~0.7 from the literature. We find that the depletion times are highly dependent on the method adopted to measure the star formation rate: using the UV+IR luminosity we obtain depletion times about 6 times shorter than those derived using dust-corrected [OII] emission. When adopting the star formation rates from spectral fitting, which are arguably more robust, we find that recently quenched galaxies and star-forming galaxies have similar depletion times, while older quiescent systems have longer depletion times. These results offer new, important constraints for physical models of galaxy quenching.

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arXiv2020

Structural evolution in massive galaxies at z~2

We present 0.2arcsec-resolution Atacama Large Millimeter/submillimeter Array observations at 870 $μ$m in a stellar mass-selected sample of 85 massive ($M_\mathrm{star}>10^{11}~M_\odot$) star-forming galaxies (SFGs) at z=1.9-2.6 in the 3D-HST/CANDELS fields of UDS and GOODS-S. We measure the effective radius of the rest-frame far-infrared (FIR) emission for 62 massive SFGs. They are distributed over wide ranges of FIR size from $R_\mathrm{e,FIR}=$0.4 kpc to $R_\mathrm{e,FIR}=$6 kpc. The effective radius of the FIR emission is smaller by a factor of 2.3$^{+1.9}_{-1.0}$ than the effective radius of the optical emission and by a factor of 1.9$^{+1.9}_{-1.0}$ smaller than the half-mass radius. Even with taking into account potential extended components, the FIR size would change by ~10%. By combining the spatial distributions of the FIR and optical emission, we investigate how galaxies change the effective radius of the optical emission and the stellar mass within a radius of 1 kpc, $M_\mathrm{1kpc}$. The compact starburst puts most of massive SFGs on the mass--size relation for quiescent galaxies (QGs) at z~2 within 300 Myr if the current star formation activity and its spatial distribution are maintained. We also find that within 300 Myr, ~38% of massive SFGs can reach the central mass of $M_\mathrm{1kpc}=10^{10.5}~M_\odot$, which is around the boundary between massive SFGs and QGs. These results suggest an outside-in transformation scenario in which a dense core is formed at the center of a more extended disk, likely via dissipative in-disk inflows. Synchronized observations at ALMA 870 $μ$m and JWST 3-4 $μ$m will explicitly verify this scenario.

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