arXiv subjects

Daizhong Liu

Publications and source records attributed to Daizhong Liu.

At least 19 recordsLinked to original sources

arXiv2026

ALMA Chemical Evolution (ACE) Survey: Molecular gas properties of low-mass, low-metallicity galaxies at cosmic noon

Molecular gas plays a central role in regulating star formation and galaxy evolution, yet observational constraints at cosmic noon remain biased toward massive, metal-rich systems. We present ALMA Band 3 observations of the CO J=3-2 transition in 26 unlensed star-forming galaxies from the ALMA Chemical Evolution (ACE) Large Program at z~2-2.5, probing stellar masses of $10^{9} < M_\star < 10^{10.5}\,\mathrm{M}_{\odot}$ and sub-solar metallicities (8.2 < 12 + log(O/H) < 8.6). We derived molecular gas masses using a metallicity-dependent CO-to-H$_2$ conversion factor and alongside analysed stacking measurements and a homogenized literature compilation spanning both local and high-redshift galaxies. We find that the ACE galaxies extend established molecular-gas scaling relations to an order of magnitude lower stellar masses than previously explored at cosmic noon. The molecular gas mass ($M_{\rm mol}$) correlates tightly with star formation rate (SFR), while molecular gas fractions show a strong dependence on specific star formation rate (sSFR) and offset from the star-forming main sequence. In contrast, molecular gas fractions show only weak trends with stellar mass and no significant dependence on metallicity. Molecular gas depletion times are ~1 Gyr and vary little with stellar mass or metallicity, and weakly with sSFR and offset from the star-forming main sequence. Together this further reinforces that the availability of molecular gas is the primary driver of the SFR in galaxies, with changes in star-formation efficiency playing a secondary role. Leveraging the expanded parameter space probed by the ACE and literature samples, we derive a new empirical prescription for predicting $M_{\rm mol}$ as a function of SFR and sSFR. The persistence of the observed scaling relations suggests a largely universal framework governing the molecular gas-star formation cycle across cosmic time.

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arXiv2026

Resolved Dust in $z\approx1$ Galaxies with JWST/MIRI MRS: Survey Description and First View on PAHs, Mid-IR Atomic Emission, and Warm H$_2$

Dust is a key component of galaxies that regulates their thermal balance and, consequently, star formation and the build-up of stellar mass. Polycyclic aromatic hydrocarbons (PAHs) are responsible for reprocessing radiative energy of the galaxies thus tracing dust evolution. Using JWST/MIRI MRS, we present the first resolved view of the PAHs and mid-infrared emission lines in a sample of eight $z\approx1$ galaxies. A key novelty is our ability to directly map PAH emission near the end of cosmic noon at JWST's limits. The sample is selected to be on the star-forming main-sequence with stellar masses $M_{\star}=10^{10.6-11.2}\,M_{\odot}$ and infrared luminosities $L_{\rm IR}=10^{11.5-11.9}\,L_{\odot}$. Two of them contain active galactic nuclei (AGN), and two are interacting systems. We detect and quantify primary PAH emissions from 3.3$\,\rm μm$ to 11.3$\,\rmμm$ throughout the galaxies, alongside atomic fine structure lines (Ar, Ne, and Fe), Br$α$, and H$_{2}$ rotational transitions. Through PAH ratio diagnostics and comparison to theoretical models, we qualitatively probe the physical properties of PAH molecules, i.e., size and charge. The AGN and mergers in our sample exhibit a higher fraction of neutral PAHs, possibly related to high radiation intensity and/or shocks, as suggested by increased atomic and H$_{2}$ line ratios. Leveraging the IFU data, we find that the grain sizes of the centrally located PAHs tend to be larger and less ionized than those in the outskirts of the galaxies. Finally, we compare our results to observations of PAHs in local and similar-redshift galaxies, revealing a potential evolutionary trend when controlling $L_{\rm IR}$.

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arXiv2026

Hidden in Pixels. I. Discovery of dual "little red dots" indicates excess clustering on kilo-parsec scales

``Little Red Dots'' (LRDs) are an abundant high-redshift population newly discovered by the James Webb Space Telescope (JWST) and considered to be an early growth phase of supermassive black holes (SMBHs). Using a method of pixel-by-pixel color selection and relaxing the compactness criteria, we identify four dual LRD candidates in the COSMOS-Web survey with projected separations of $0.\!\!^{\prime\prime}2$-$1.\!\!^{\prime\prime}2$. A comparison between existing LRD samples and mock data reveals that the projected separations of these dual LRD candidates are unlikely to result from chance projections of objects at different redshifts. Furthermore, two of the four systems are covered by COSMOS-3D slitless spectroscopy, and a single-line detection at the same observed wavelength for each LRD in a pair strongly supports that they are at identical redshifts. Assuming that the detected lines are H$α$ based on their high equivalent width and broad profile, the spectroscopic redshifts of $z=5.822$ and $5.464$ for the two pairs are consistent with their photometric redshifts, yielding projected separations of $1.64$ and $7.36\,{\rm kpc}$. These discoveries suggest that the angular auto-correlation function (ACF) of LRDs exhibits an excess ($\sim20$-$30$ times) on sub-arcsec (kilo-parsec) separations compared to an extrapolation of a power-law ACF of JWST-found AGNs measured over $10^{\prime\prime}$-$100^{\prime\prime}$. Our sample is likely to represent precursors of mergers between LRDs, and such mergers may be one of the mechanisms that can drive the rapid growth of SMBHs in their early evolutionary stages.

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arXiv2026

NOEMA3D: Extended CO, [C I] and dust in massive star-forming main-sequence galaxies at cosmic noon

We present a spatially resolved study of cold molecular gas and dust in ten main-sequence galaxies at z=1.1-1.6, using observations of CO(4-3), CO(3-2), [CI](1-0), and dust continuum from the NOEMA3D survey. We find widespread spatially extended molecular gas and dust, with sizes comparable to those of the stellar disk, in contrast to those of centrally dominated starburst galaxies at similar redshifts. Among the targeted molecular gas tracers, the CO line (J=3-2 or J=4-3) remains the most effective for mapping molecular gas distribution and kinematics. The spatially resolved correlations between different molecular gas tracers exhibit about twice the scatter as their galactic-integrated correlations, indicating that interstellar medium (ISM) conditions already deviate from global averages on scales of 3-6 kpc. This likely reflects the clumpy or inhomogeneous ISM in cosmic noon star-forming galaxies. Within our sample, both the molecular gas fraction and its depletion time are nearly constant across the galactic disks out to 2xRe, supporting a global linear Kennicutt-Schmidt law. These galaxies also have relatively small bulges, with bulge-to-total ratios between 6-24%, and are actively forming stars. These results provide a resolved view of how galaxies can remain on the star-forming main sequence during their secular evolution at late cosmic noon, an evolutionary stage supported by quasi-steady gas accretion and efficient gas transport via prominent spiral arms and/or bars.

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arXiv2026

The Koi Pond: A Strongly Lensed Protocluster Core hosting a Diverse Population of DSFGs

We present James Webb Space Telescope (JWST) and Atacama Large Millimeter Array (ALMA) observations of PJ0846+15, \textit{The Koi Pond}, a strongly lensed protocluster core at Cosmic Noon. This field offers a magnified view of 11 dusty star-forming galaxies (DSFGs) all at $z=2.67$ (within $ΔV=800$ km s$^{-1}$) spanning a projected extent of $>300$ kpc lensed by a $z=0.77$ foreground cluster. NIRCam and ALMA Band 6 continuum measurements map the stellar distribution and thermal dust emission respectively at a spatial resolution of $\sim$0.15$^{\prime\prime}$. This analysis reveals a diverse population of DSFGs, with evidence of both interacting and non-interacting systems exhibiting a wide range of morphological features including spiral arms, bars, bulges, clumps/stellar clusters, tidal tails/debris and displaced molecular gas reservoirs. Comparing the rest-frame J- band continuum (F444W) vs (i-J) color (F277W$-$F444W), we find a wide range of values, suggesting a $>$1-dex spread in stellar mass and a dust attenuation reddening of $ΔA_{\mathrm{V}} > 1$ mag. The DSFG members exhibit varying dust sizes relative to the stellar emission, ranging from compact dusty cores to galaxy-wide emission. Resolved color maps of individual sources showing a spread as high as F277W$-$F444W$=2$ mag suggesting complex stellar-to-dust geometry. Although gas-rich mergers are identified in the core, the most red and dust emitting members are disks exhibiting clumpy structure indicating secular growth can drive these starburst events. Such a remarkable range in properties within this sample suggest DSFGs in protocluster core environments follow diverse evolutionary pathways towards their transition into quiescent, elliptical cluster galaxies.

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arXiv2026

Dust in the Average Galaxy: Attenuation, Emission, and Opacity from $0<z<7$

We present constraints on the dust emission and attenuation properties of galaxies across 0 10^{10.5}M_\odot$. We derive empirical relationships for the effective attenuation, dust temperature, fraction of star formation that is unobscured, and dust-to-stellar mass ratio as functions of redshift and stellar mass. We separate the first order effect of star/dust geometry from dust grain properties by combining constraints on the IR SED, UV SED, and dust mass surface density. Importantly, we measure over an order of magnitude decrease in $κ_{UV}/κ_{FIR}$--the ratio of dust mass absorption coefficients in the UV at 1600Å and FIR at 500$μ$m--from z~0 to z~7. A depressed $κ_{UV}/κ_{FIR}$ is consistent with a deficit of small dust grains, possibly attributable to the intense radiation fields of high-$z$ star formation; indeed, we find a redshift-invariant inverse relationship between $κ_{UV}/κ_{FIR}$ and $Σ_{SFR}$. Most evolution in the dust-to-stellar ratio is at $z<1$, the product of mild downward evolution in the dust-to-gas ratio combined with steep evolution in the gas-to-stellar ratio. The significant evolution and dynamic range of $κ_{UV}/κ_{FIR}$ and prevailing disconnect between the UV/optical and FIR regimes emphasize that direct dust constraints are irreplaceable for the majority of star-forming galaxies at z<7, not just the most extreme star-formers.

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arXiv2026

PASSAGES: The Discovery of a Strongly Lensed Protocluster Core Candidate at Cosmic Noon

Investigating the processes by which galaxies rapidly build up their stellar mass during the peak of their star formation ($z=2-3$) is crucial to advancing our understanding of the assembly of large-scale structures. We report the discovery of one of the most gas- and dust-rich protocluster core candidates, PJ0846+15 (J0846), from the Planck All-Sky Survey to Analyze Gravitationally lensed Extreme Starbursts (PASSAGES) sample. The exceedingly high total star formation rate (SFR) uncorrected for lensing magnification ($μ$) of $μ\text{SFR} = 39900^{+23000}_{-12900} \text{ M}_\odot\text{ yr}^{-1}$ is the result of a foreground cluster lensing at least 11 dusty star-forming galaxies between $z=2.660-2.669$, where the intrinsic value is estimated to be $\text{SFR} = 5200^{+3200}_{-2000} \text{ M}_\odot\text{ yr}^{-1}$. Atacama Large Millimeter Array (ALMA) observations uncovered 18 CO(3--2) emission-line detections, some of which are multiply-imaged systems, lensed by a foreground cluster at $z=0.77$. We present the first multi-wavelength characterization of this field, constructing a lens model that predicts that these 11 galaxies ($μ\simeq 1.5-25$) are contained within a projected physical extent of $280 \times 150 \text{ kpc}$, with a velocity dispersion of $σ_{v} = 246 \pm 72 \text{ km s}^{-1}$. J0846 exhibits the rare case of a protocluster candidate whose core is strongly-lensed, offering a magnified view of the rapid stellar buildup within an overdense environment at Cosmic Noon.

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arXiv2026

Resolving stellar populations, star formation, and interstellar medium conditions with JWST in a large spiral galaxy at $z\approx2$

Cosmic noon represents the prime epoch of galaxy assembly, and a sweet spot for observations with the James Webb Telescope (JWST) and ground-based near-IR integral-field unit (IFU) spectrographs. This work analyses JWST NIRSpec Micro Shutter Array (MSA), NIRCam Wide Field Slitless Spectroscopy (WFSS) of K20-ID7, a large spiral, star-forming (SF) galaxy at z=2.2, with evidence for radial gas inflows. By exploiting the synergy with ground-based IFU ERIS observations, we conduct a comprehensive and resolved study of the interstellar medium (ISM) and stellar properties, from rest optical to near-IR, via emission-line diagnostics, resolved spectral energy distribution (SED) fitting of high-resolution imaging, and Pa$β$ line detection in NIRCam WFSS data. Our analysis reveals massive ($M_{\star}\simeq$(0.67-3.5)$\times$10$^{9}$ $M_{\odot}$) SF clumps with star formation rates (SFRs) ~3-24 $M_{\odot}$/yr, and quite low dust attenuation ($A_V\simeq$0.4), electron density ($n_{e}$<300 cm$^{-3}$), and ionisation (log(U)$\simeq -3.0$). The central bulge turns out to be modestly massive ($M_{\star}$=(7$\pm$3)$\times$10$^{9}$ M$_{\odot}$), heavily obscured ($A_V$=6.43$\pm$0.55), and likely to have formed most of its stellar mass in the past (SFR=82$\pm$42 $M_{\odot}$/yr over the last 100 Myr), yet still forming stars at a lower rate (SFR=12$\pm$8 M$_{\odot}$/yr over the last 10 Myr). We infer a metallicity 12+log(O/H)~8.54 and an apparent enhancement of the N/O abundance (log(N/O)$\simeq -1.0$) in all distinct galaxy regions, a likely consequence of dilution effects due to radial inflows of metal-poor gas. We measure a sub-solar sulfur abundance (log(S/O)$\simeq$-1.9). Finally, the radial stellar age profile reveals older stellar populations in the inner galaxy regions compared to the outskirts, pointing to an inside-out growth of K20-ID7.

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arXiv2026

Gravitationally Lensed View of DSFG-1 in PLCK G165.7+67.0: Strong Dust Emission and Spatially Resolved Stellar Population Analysis with JWST and SMA

We present a detailed stellar population analysis of the strongly lensed dusty star-forming galaxy (DSFG) PLCK G165.7+67.0 DSFG-1 at $z = 2.236$, combining JWST NIRCam imaging with new Submillimeter Array (SMA) observations. This source is multiply imaged into two lensed components: image 1a, with a moderate magnification factor of $μ\sim 5$, and image 1bc, with an extreme magnification factor of $μ\sim 40$. The new SMA observations detect significant dust continuum emission at 225GHz and 273GHz, with combined flux densities of $S_{\rm cont}=(1.19\pm0.38)$ mJy in image 1a and $S_{\rm cont}=(10.02\pm0.85)$ mJy in image 1bc, indicating active star formation at sub-kpc scale. Based on the integrated SED modeling, DSFG-1 exhibits a lensing amplification-corrected stellar mass of $M_{\star} = (1.2 \pm 0.4) \times 10^{10} M_{\odot}$, and a star-formation rate (SFR) of $(103 \pm 14) M_{\odot}\,\mathrm{yr^{-1}}$, similar to previous $Hα$-based results, placing it four times above the star-forming main sequence at this redshift. Its location on the size-mass plane and its morphological properties suggest that the system occupies a transitional phase between star-forming late-type galaxies and compact early-type systems. Together with its elevated star-formation activity, this is consistent with a rapidly evolving galaxy observed during Cosmic Noon. We further investigate the spatially resolved stellar population properties, and found significant spatial variations in stellar age and dust attenuation. These results point to a non-uniform star-formation history and highlight the complex interplay between dust geometry, stellar growth, and gravitational lensing, consistent with a merger scenario.

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arXiv2026

A steep mass transition for bar-driven ISM structuring revealed by PHANGS-JWST

Galactic bars play a critical role in the secular evolution of their hosts by reorganising the ISM. We use a sample of 57 star-forming disc galaxies observed with JWST at 3 and 7.7 $μ$m to probe how the spatial distribution of PAH emission, as a structural marker of the cold ISM, depends on stellar mass and bar presence. We find evidence for a "watershed" at a stellar mass of $10^{10}$ Msun, marking a fundamental transition in the bar-driven distribution of PAH emission. This confirms trends previously predicted by numerical simulations and observed via ionised gas or UV light. While lower-mass galaxies exhibit a disordered and clumpy distribution of PAH emission regardless of bar presence, higher-mass barred hosts display well-structured dynamical features traced by PAH emission with significant gas reservoirs (e.g., discs and rings) within the central 15% of the bar radius (Rb). Furthermore, we observe a systematic depletion of PAH emission within the [0.2-0.8] Rb range in barred systems with stellar masses above $10^{10}$ Msun. Such central discs, rings, and associated radial dips ("bar deserts") appear to be a mass-dependent phenomenon: ubiquitous in massive galaxies but mostly absent in lower-mass counterparts. In contrast to the structured features in massive hosts, the disorganised ISM in lower-mass galaxies masks commonly observed bar-driven signatures. This suggests that tracer selection and dust obscuration may significantly bias observed bar fractions. Our study underlines two regimes of secular evolution, with different impacts and observability of bar-driven processes: it reaffirms bars as primary drivers of rapid secular evolution in galaxies above $10^{10}$ Msun$, while their impact is significantly reduced or delayed below this threshold. It further underscores the need to account for these processes when modelling galaxy evolution in cosmological simulations.

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arXiv2026

COSMOS-Web: does halo mass alone shape the clustering of star-forming and quiescent galaxies?

While stellar mass correlates strongly with halo mass, it remains unclear whether halo mass alone governs galaxy star-formation activity, or whether secondary halo properties and environment also play a role. We investigate these effects beyond halo mass by measuring the auto- and cross-correlations of star-forming and quiescent galaxies in the COSMOS-Web survey from $z = 5$ to the present day. To isolate environmental contributions, we introduce a method that matches the halo mass distributions of both populations using the UniverseMachine model. We find that quiescent galaxies remain more strongly clustered than star-forming systems by at least $0.5-1$ dex at all redshifts, even after controlling for halo mass. At $z \le 2$, this excess clustering increases towards lower stellar masses, with the most clustered objects being $\log(M_\star/{\rm M}_\odot) \le 9.5$ quiescent galaxies. This points to environmental quenching significantly affecting low-mass galaxies at $z \le 2$, likely driven by ram-pressure stripping or the suppression of cold gas accretion, as these objects show disky morphologies. Cross-correlations further reveal one-halo conformity up to $z \simeq 2$: low-mass (or satellite) quiescent galaxies are more strongly clustered around massive (or central) quiescent galaxies than around star-forming centrals of the same halo mass. This signal may arise from quenching mechanisms affecting both centrals and satellites, correlated assembly histories prior to infall, or dependencies on secondary halo properties. Both environmental quenching and conformity appear to vanish between $z \simeq 5$ and $2$. Together, these results challenge the common assumption that clustering and star-formation activity depend solely on halo mass.

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arXiv2026

Ram-pressure stripping caught in action in a young cluster at $z = 2.51$

Galaxy clusters in the local Universe are dominated by massive quiescent galaxies with old ages, formed at high redshifts. Whether their quenching is driven by internal processes or environmental effects is a matter of debate that has been challenging to resolve due to the lack of observations during their peak formation epoch. Here we report clear evidence from the Atacama Large Millimeter/submillimeter Array of extended and elongated gas tails in five galaxies in a forming cluster at z = 2.51. The single-tailed gas distributions, which extend notably beyond the stellar emission probed by JWST in galaxies that are relatively isolated and lack signatures of mergers or interactions (features that are very uncommon in the field), provide evidence of ram-pressure stripping. These very distant confirmed cases of ram-pressure stripping highlight the critical role of environmental effects in gas removal at high redshifts, an often-overlooked quenching pathway.

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arXiv2026

The first detection of dense gas in a massive main-sequence galaxy at cosmic noon

Dense gas is the direct fuel for star formation, but measuring it has long been difficult at z>2, especially in typical star-forming main-sequence galaxies. In this work, we report the first detection of HNC (J = 5--4) and CN (N = 4--3) emission in a massive main-sequence galaxy, BX610, at z=2.21. The velocity integrated emission of HNC(5--4)+CN(4--3) is concentrated in the galactic centre, coincident with the region of ongoing intense star formation. Based on line decomposition, we measure a line flux ratio HNC(5--4)/CN(4--3) of $1.05\pm0.23$, similar to that of starburst galaxies at comparable redshifts but lower than that of quasar/AGN host galaxies. The comparatively fainter HNC(5--4) disfavours the presence of a strongly buried AGN in BX610, consistent with optical line diagnostics. The radiative transfer analysis favours the presence of dense gas with a density of $(2-4)\times10^{6}\,\text{cm}^{-3}$ and a kinetic temperature of 50-80 K. The derived abundance ratio between N(HNC) and N(CN) favours dense gas clouds near photodissociation regions, as commonly seen in typical starburst environments. The inferred dense-gas line luminosity closely follows the scaling relation between far-IR and dense-gas line luminosities established for local luminous infrared galaxies (LIRGs). Our observations support the view that star formation in cosmic noon galaxies is primarily controlled by the availability of dense gas, which could be enhanced in central galactic regions with efficient cold gas inflows as observed in BX610 along the inner spiral arms and a possible stellar bar.

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arXiv2026

COSMOS-Web: A Multi-wavelength Morphological Catalog of ~780,000 Galaxies

We present multi-wavelength morphological measurements for all galaxies in the COSMOS-Web survey, i.e., $\sim$780,000 galaxies contained in the COSMOS2025 catalog. We perform both parametric (e.g., single and double Sérsic modeling) and non-parametric (e.g., Gini-$M_{20}$) morphology analyses in four NIRCam bands, independently. Our parametric fits reveal a strong correlation between galaxy structure and star formation activity up to $z\sim4$, as evidenced by the dependence of the Sérsic index ($n_{\rm sérsic}$) and bulge-to-total ratio ($B/T$) on the position of the star formation rate-stellar mass plane. A tight correlation between $n_{\rm sérsic}$ and $B/T$ is observed. The evolution of $n_{\rm sérsic}$ and $B/T$ depends on stellar mass; for example, the median $n_{\rm sérsic}$ increases from $\sim1$ at $z\sim6$ to $\sim2.5$ at $z\sim2$ for massive galaxies with $M_*>10^{10.5} M_{\odot}$, while lower mass galaxies remain $n_{\rm sérsic}\sim1.2$ at all epochs. The UV $n_{\rm sérsic}$ values are systematically smaller than those in the optical, although both exhibit similar evolutionary trends. From non-parametric analyses, we demonstrate the distribution of galaxies on the Gini-$M_{20}$ and asymmetry-concentration planes, and find that morphological classifications based on non-parametric indicators are consistent with those derived from the Sérsic index. The resulting catalog provides the largest and most detailed set of JWST multi-wavelength morphological measurements to date, serving as a valuable community resource for studies of structural transformation, bulge growth, and galaxy-supermassive black hole coevolution across cosmic time.

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arXiv2026

NOEMA$^\rm{3D}$: A deep view of cold gas flows in a barred spiral galaxy at $z\sim1$

We present a deep, high-resolution CO(4-3) IRAM-NOEMA observation of a main sequence, barred, spiral galaxy at $z\approx1.12$, with an on-source integration time of $\approx37$ hours and a beam FWHM of $\approx0.\!\!^{\prime\prime}3$. We use the molecular gas data in conjunction with the available deep multi-band JWST and HST imaging, covering restframe UV to near-IR wavelengths, to quantitatively study the gas flows in the disk plane of this cosmic noon barred spiral. We find that this target is a massive ($\log(M_{\rm{baryons}}/M_\odot)\approx10.96$), baryon-dominated ($f_{\rm{dm}}(<R_e)=u^2_{\rm{circ,dm}}(R_e)/u^2_{\rm{circ}}(R_e)\sim4\%$), gas-rich ($f_{\rm{gas}}=M_{\rm{gas}}/(M_{\rm{\star}}+M_{\rm{gas}})\approx40\%$) disk, hosting a long ($a_{\rm{bar}}\approx4.2$ kpc), strong ($Q_{\rm{b}}\approx0.37$), and fast ($\mathcal{R}=R_{\rm{CR}}/a_{\rm{bar}}\approx1.05$) bar, which rotates at an angular speed of $Ω_{\rm{pattern}}\approx$ 50 km/s/kpc. This bar is driving molecular gas inflows with a net inflow rate of $\dot{M}\sim30$ $M_\odot$/yr, based on three estimates, which is of the same order as the galaxy-integrated star formation rate ($\rm{SFR}\approx36$ $M_\odot$/yr). We additionally identify evidence of a well-defined dust lane shock at the northwestern side of the bar, with gas motions parallel to this feature, in agreement with expectations for an established bar-driven flow. Our study highlights the possible role of bars as key drivers of galaxy evolution for a significant fraction of cosmic noon galaxies, offering a detailed picture of well-defined, bar-driven inflows in a high-$z$ barred spiral.

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arXiv2026

Suppression of star formation at the centre of barred AGN galaxies

We measured the Concentration (C) index of Hαand CO (J = 2-1) in 17 nearby star-forming galaxies from the PHANGS survey. We have found four barred spiral galaxies with a C(Hα)/C(CO) ratio of ~ 0.3-0.4, while the other 13 galaxies exhibit ratios of ~ 1 (range from 0.7 to 1.3). All four barred galaxies with low ratios host active galactic nuclei (AGNs), consistent with a scenario in which star formation is suppressed by mechanical and radiative feedback from the AGN. Therefore, negative feedback is effective in these four barred galaxies with a low molecular gas mass fraction (< 0.1), even when AGN activity is relatively weak. The formation of bar structures causes molecular gas to collect in the central region, leading to starburst activity. However, after the starburst, the remaining gas becomes inefficient for star formation rapidly due to AGN feedback. It can mean the quenching process occurs more rapidly in AGN-barred galaxies. Furthermore, since gas remains in the central region, AGN activity is likely to continue. These quenching processes are a unique mechanism found in barred spiral galaxies and are essential to understanding galaxy evolution.

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arXiv2026

A Spatially Resolved HI Survey of Seyfert Galaxies: the Role of AGN Feedback in Shaping Atomic Gas Reservoirs

Active galactic nucleus (AGN) feedback is a key ingredient in galaxy evolution, yet its impact on the cold atomic gas reservoir -- the neutral hydrogen (HI) phase -- remains poorly constrained. We present the most extensive spatially resolved HI 21-cm survey of Seyfert AGN hosts to date, based on observations with the Giant Metrewave Radio Telescope (GMRT). Our high-resolution HI maps of eight Seyfert galaxies reveal detailed kinematics and surface density distributions of their atomic gas disks. We find that AGN-host galaxies exhibit a slightly shallower HI mass-size relation than the canonical relation or the SIMBA simulation predictions; however, the measured slope remains consistent with the canonical value within $2σ$ uncertainties. This result suggests that AGN feedback does not significantly disrupt the global extent or large-scale structure of atomic gas reservoirs. To investigate the internal HI kinematics in greater detail, we perform a 3D kinematic forward modeling of the HI disk in UGC 4503. Our analysis reveals an elevated intrinsic velocity dispersion of $σ= 14.9^{+6.1}_{-3.8}$ km/s and a reduced level of rotational support, with $V/σ= 14.28_{-4.17}^{+4.97}$, compared to large-sample star-forming spirals. These kinematic signatures, together with localized residuals in the velocity field, indicate that AGN-driven outflows or jets may inject or indirectly affect the turbulence in the atomic gas disk, potentially regulating the cold gas reservoir. Future GMRT observations, combined with optical integral-field spectroscopy from MaNGA, will enable quantitative constraints on the role of AGN feedback in regulating star formation efficiency across a larger and more representative galaxy sample.

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arXiv2026

The ALPINE-CRISTAL-JWST Survey: Gas-phase abundance gradients of main sequence star-forming galaxies and their kinematics at $4 < z < 6$

We present gas-phase radial metallicity profiles for 20 main-sequence galaxies at $4 0.05{\rm dexkpc^{-1}}$ at $1σ$, and none have a significant negative gradient. We investigated the correlation between the metallicity gradients and the intrinsic gas velocity dispersion $σ_0$ as well as the $V_{\rm rot}/σ_0$ ratio of the disks. Combining our sample with mass-matched literature samples at $3<z<7$, we found a negative shallow correlation between $V_{\rm rot}/σ_0$ and the metallicity gradients, but no strong relationships with $σ_0$. As $V_{\rm rot}/σ_0$ increases towards later cosmic times, the observed negative trend with $V_{\rm rot}/σ_0$ is consistent with the overall cosmic evolution of metallicity gradients from high to low redshifts. This suggests that disk maturity plays a crucial role in shaping the radial metallicity gradients. [Abridged abstract]

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