arXiv subjects

Fuyan Bian

Publications and source records attributed to Fuyan Bian.

At least 19 recordsLinked to original sources

arXiv2026

A Wandering 35,000-Solar-Mass Black Hole Fed by a Gravitational Wake

Intermediate-mass black holes are widely considered to be the seeds of supermassive black holes, a substantial population of which is expected to remain displaced from galactic nuclei owing to hierarchical galaxy assembly and inefficient dynamical friction. While several fueling channels can sustain central black holes, those pathways are largely inaccessible to off-nuclear black holes, leaving their fuel supply uncertain. As these wandering black holes move through the interstellar medium of their host galaxies, theory predicts that they can capture gas from the dense wake produced by gravitational focusing. However, direct observational evidence for this process has remained elusive. Here we report evidence for a wandering intermediate-mass black hole of 35,000 solar mass accreting through such a gravitational wake. Its black-hole nature is supported by broad-line emission, a compact continuum counterpart, long-term optical variability, and a power-law-like spectral energy distribution. Multi-epoch spectroscopy reveals three distinct gas components: a blueshifted, low-density upstream flow; a redshifted, dense downstream wake; and optically thick absorbers well within the capture radius that drive rapid changing-look variability in the broad-line emission. This discovery establishes a previously unobserved channel for the growth of wandering intermediate-mass black holes.

astro-ph.GA↗

arXiv2026

Characterization of the MUSE NFM PSF as a function of atmospheric conditions: TipTop calibration

The Multi Unit Spectroscopic Explorer (MUSE) achieves exceptional spatial resolution in narrow-field mode (NFM) thanks to the GALACSI adaptive optics (AO) system. However, limitations in point spread function (PSF) characterization still hinder the full exploitation of its capabilities. In particular, the current exposure time calculator (ETC) lacks an accurate PSF model, preventing users from reliably predicting the signal-to-noise ratio of NFM observations during proposal preparation. To address this limitation, we analyzed a large set of archival standard-star observations to quantify how NFM PSF properties vary with observing conditions, including airmass, seeing, coherence time, wind speed, and wavelength. We then used this reference dataset to calibrate TipTop, a fast AO PSF simulation tool that will be integrated into the next release of the MUSE NFM ETC. Our results demonstrate that calibration against real on-sky data is essential for accurate PSF modeling. In particular, we find that reproducing realistic PSFs requires both an additional static aberration term and an airmass-dependent tip-tilt jitter component. The calibration performs well at wavelengths longer than 7000 A, while additional corrections are still required at shorter wavelengths, likely due to unmodeled chromatic aberrations. Once implemented in the ETC, this tool will provide condition-dependent NFM PSF predictions and more reliable signal-to-noise estimates.

astro-ph.IM↗

arXiv2026

VLT/MUSE Study of Close AGN Pairs and Host Galaxies in the Local Universe. I. Overview of the Ionized Gas

Studying AGN pairs and their host galaxies is essential for understanding the interplay between galaxy mergers and key internal processes such as supermassive black hole fueling and feedback. We cross-match between the Big Multi-AGN Catalog (The Big MAC) and the public data archive of the VLT/MUSE, and obtain 12 AGN pair candidates in the local universe ($z\lesssim0.1$) with a projected distance $r_{\rm p}\leq 20\rm\,kpc$. Using the archival VLT/MUSE data, we present a spatially resolved study of the ionized gas kinematics and ionization properties of these 12 AGN pair candidates. By decomposing the optical emission lines into two Gaussian components, we try to separate gas associated with disk rotation from non-circular motions. We further identify dominant ionization mechanisms using spatially resolved BPT diagnostics. We find that both nuclei in 4 of the 12 systems are classified as Seyfert or LINER. In addition, three nuclei are classified as star-forming or composite in the optical diagnostics, but are identified as AGNs at other wavelengths. Kinematically, regularly rotating ionized gas disks are detected in 16 of 24 nuclei. Prominent tidal features traced by ionized gas are also detected in 9 systems. Ionized gas outflows are widespread and are detected in 18 nuclei. Finally, for three nuclei (Mrk 739A, NGC 7592B, and J1544+0446A), we find evidence for fading AGN activity over the past several $10^{4}\rm\, yr$, based on optical emission-line ratios and an assumed AGN photoionization model.

astro-ph.GA↗

arXiv2026

Misaligned or chaotic? A strong break of axial symmetry in the local LRD J1025 revealed with VLT/FORS2 spectropolarimetry

Little Red Dots (LRDs) are compact active galactic nuclei (AGN) with unusual spectral energy distributions and broad Balmer emission, candidate signposts of rapid black-hole growth. We present VLT/FORS2 optical linear spectropolarimetry of the closest known LRD, SDSS J102530.29+140207.3, at z=0.1. In total light, we detect spatially extended narrow-H$\alpha$ emission, probably tracing the host galaxy. We measure a nearly grey continuum polarisation $p_{\rm cont}=1.53\pm0.04$(rand.)$\pm$0.20(syst.) per cent, while broad H$\alpha$ is less polarised, $p_{\rm H\alpha}=0.58-0.84$ per cent. We rule out polarisation by Milky Way dust and dilution by an unpolarised line. The polarised continuum with a depolarised line resembles local Seyfert-1 nuclei and favours a single dominant source over multi-source explanations. After Stokes-continuum subtraction, broad H$\alpha$ shows no blue-to-red swing, but there is a significant (48$\pm$4)$^\circ$ continuum-to-line offset in polarisation angle. This implies a break of axial symmetry inside this object, posing interesting geometrical challenges to all existing LRD models and frameworks. We discuss different possible origins of this symmetry break and possible paths to discriminate between them with future observations.

astro-ph.GA↗

arXiv2026

Photoionization of the Composite Nebula Surrounding NGC 5408 X-1: Implications for Beamed Emission

NGC 5408 X-1 is one of the best studied ultraluminous X-ray sources (ULXs) and is surrounded by a photoionized nebula. Previous optical spectroscopy established the presence of strong Balmer, [O III], and He II $\lambda4686$ emission from the nebula, but the powering engine remains uncertain. In this work, we present new integral-field observations of NGC 5408 X-1, supplemented by archival long-slit spectroscopy and Hubble Space Telescope (HST) imaging, and confirm the presence of a composite nebula, with a small He III region centered on the ULX and a large, shell-like H II region. We also confirm that the broad He II emission is point-like and most likely associated with the ULX binary system. Photoionization simulations with Cloudy show that the ULX spectral energy distribution (SED), with a total luminosity of $2.4 \times 10^{40}\ {\rm erg\ s^{-1}}$ obtained by fitting the optical/UV/X-ray data, overpredicts both the luminosity and size of the He III region. Instead, adopting the same SED shape with a reduced luminosity of $1.0 \times 10^{39}\ {\rm erg\ s^{-1}}$ together with a blackbody of temperature $30000\ {\rm K}$ and luminosity $1.3 \times 10^{39}\ {\rm erg\ s^{-1}}$ successfully reproduces both the He III and H II regions in terms of their luminosities and sizes. Such a dual-component ionizing spectrum is consistent with HST measurements of the ULX in the optical and UV, while being a factor of 24 lower than the inferred isotropic X-ray luminosity. This implies that the EUV and X-ray emission from the ULX may be mildly beamed toward our line of sight, consistent with the picture of supercritical accretion.

astro-ph.HE↗

arXiv2026

A Strong Stellar Age-Metallicity Gradient Relation in Nearby Dwarf Galaxies Driven by Stellar Migration and Environmental Quenching

Stellar metallicity gradients ($\nabla[Z/H]$) provide a fossil record of the assembly history of galaxies. We present an analysis of $\nabla[Z/H]$ for 90 nearby low-mass galaxies using VLT/MUSE IFU spectroscopy, spanning stellar masses from $10^{6.5}$ to $10^{10} M_\odot$ (median $\sim 10^{8.5} M_\odot$) and significantly extending the mass coverage of existing IFU surveys into the classical dwarf regime. Our primary finding is a robust negative correlation between $\nabla[Z/H]$ and light-weighted stellar age ($|r|\gtrsim 0.7$) measured out to $\sim$ 2$\times$ effective radius: older dwarf galaxies have steeper (more negative) gradients. This holds regardless of stellar mass, structural compactness, or large-scale environment (group/field), and is strongest in the intermediate-mass regime ($8.2\lesssim\log M_\star/M_\odot\lesssim9.0$). The slope of the age-$\nabla[Z/H]$ relation is close to that in the FIRE-2 simulations, indicating that stellar radial migration driven by feedback-induced potential fluctuations may be fundamental in dwarf evolution. But this apparent consistency is likely coincidental given the simulations' overly efficient feedback and chemical mixing. On the other hand, the H\,\textsc{i} deficiency parameter, an indicator of past environmental stripping, shows a moderate yet highly significant correlation with $\nabla[Z/H]$, second only to stellar age in strength: galaxies with higher H\,\textsc{i} deficiency tend to have more negative gradients, strongly indicating that environment-driven outside-in quenching and the ensuing gradual truncation of metal enrichment re-shape the stellar metallicity distribution. Our analysis suggests that the chemical evolution of dwarf galaxies likely arises from a synergy of feedback-driven dynamical heating and external environmental processing, though only the latter has robust observational support.

astro-ph.GA↗

arXiv2026

MAMMOTH-Grism: Gas-phase Metallicity Gradients of Star-forming Galaxies in Protocluster Environments at Cosmic Noon

Environment plays a crucial role in shaping galaxy formation, yet the impact of overdensities on the internal chemical structure of galaxies at cosmic noon is still under debate. Here, we present spatially resolved gas-phase metallicity gradients for 42 star-forming galaxies in three massive protoclusters at $z \sim 2.3$, derived fromHubble Space Telescope (HST) slitless grism spectroscopy from the MAMMOTH-Grism survey. We find that the majority (29 of 42, $\sim$69%) of these protocluster members exhibit positive (inverted) metallicity gradients, a fraction significantly higher than observed in field galaxies of similar mass and redshift. By examining correlations with global properties, we show that these positive gradients are strongly associated with galaxies that are metal-deficient relative to the field mass-metallicity relation, particularly among the massive population ($\log(M_*/M_\odot) > 9.95$). These trends suggest that galaxies in dense protocluster environments experience substantial, enhanced inflows of pristine gas toward their central regions, which dilute the central metallicity and produce the observed inverted gradients. Our results provide observational evidence that environmental effects actively regulate gas accretion and chemical redistribution during the peak epoch of cosmic star formation.

astro-ph.GA↗

arXiv2026

(LRDs)$^2$: The Low-ReDshift Little Red Dots Survey. II. DESI DR1 Sample

JWST has revealed a substantial population of "Little Red Dots" (LRDs) at $z>4$, challenging conventional AGN frameworks. However, the low-redshift regime remains largely unexplored. In the second paper of the (LRDs)$^2$ series, we present a systematic selection from DESI DR1 and identify 27 LRDs at $z=0.2-0.9$, yielding a number density lower limit of $7.5 \times 10^{-10}$ cMpc$^{-3}$. We conducted near-IR spectroscopic follow-up observations for 18 of them, revealing their full SED shapes and emission lines. These low-$z$ LRDs share the hallmark properties of their high-$z$ counterparts: compact morphology, V-shaped UV-optical continua, broad Balmer emission with extreme decrements (median H$\alpha$/H$\beta \sim 16$), frequent Balmer absorption (67%), and blackbody-like optical-to-near-IR continua. All have low metallicity, occupy the same regions in the BPT diagram as high-$z$ LRDs, and have softer ionizing spectra than typical AGNs. The consistency between low-$z$ and high-$z$ LRD properties indicates the same physical processes at work. The correlation between broad-line Balmer luminosity and $L_{5100}$ deviates from that of local type-1 AGNs, limiting the direct application of local BH mass calibrations. Ionized [O III] outflows are ubiquitous (78%). One LRD at $z=0.196$, J1717+3807, shows robust long-term variability in $i$ and WISE bands. The optical-to-NIR continua of LRDs reveal a wide range of temperatures $\sim 2000-4700$ K (peak $0.6-1.5$ $\mu$m), with a subset showing cooler and larger envelopes than those at high $z$. Low-$z$ LRDs serve not only as proximate laboratories for probing the nature of LRDs, but also trace the cosmic evolution of this population from the cosmic dawn to the present day.

astro-ph.GA↗

arXiv2026

A Post-starburst Galaxy Undergoing Ram-pressure Stripping at Redshift 3.06

Understanding how galaxies ignite and extinguish their star formation remains a cornerstone question in modern astrophysics. Recent JWST surveys have revealed an overabundance of massive quiescent galaxies in the first billion years of the Universe, challenging current models of galaxy evolution. In the nearby Universe, ram pressure stripping (RPS) is a major environmental mechanism capable of rapidly shutting down star formation, yet direct observation remains scarce at redshift $z\gtrsim1$, and its role at $z>2$ is even poorly constrained by simulations. Here, we utilize JWST and ALMA observations to present direct evidence of RPS in the post-starburst galaxy A2744-JF-z3, residing in a galaxy group at redshift 3.06, the earliest such detection to date. Spectroscopic diagnostics and spectral energy distribution modeling reveal the ongoing removal of cold gas and dust, coincident with the abrupt cessation of star formation. Contrary to hydrodynamical simulations that predict a reduced incidence of RPS at high redshift, our results instead imply that RPS can operate at $z>3$, suggesting a highly stochastic and impulsive stripping within a clumpy, filamentary intra-group and circumgalactic medium. These observations extend environmental quenching well into the epoch of galaxy assembly, highlighting RPS as a previously overlooked decisive pathway to rapid quenching in nascent groups and protoclusters in the early Universe.

astro-ph.GA↗

arXiv2026

LCEz4-M1: A Lyman Continuum Emitter Candidate at z = 4.444 in the MUSE Hubble Ultra Deep Field

High-redshift Lyman continuum emitters (LCEs) are crucial for understanding how galaxies ionize the neutral hydrogen in the epoch of reionization. However, detected LCEs at $z>4$ are quite rare. Here we report an LCE candidate at $z = 4.444$, dubbed LCEz4-M1, which is one of the highest-redshift LCE candidates currently known. The redshift is determined from the Ly$\alpha$ emission line detected in the VLT/MUSE spectrum. The Lyman continuum (LyC) signal is detected independently in the \emph{Hubble Space Telescope} (HST) F435W image and the VLT/MUSE spectrum at significances of $\simeq3.7~\sigma$ and $\simeq2.8-3.0~\sigma$, respectively. The LyC centroid is spatially consistent with the JWST/NIRCam continuum within the astrometric uncertainty. Adopting the maximum IGM transmission, we infer conservative lower-limit escape fractions of $f_{\rm esc}({\rm F435W}) = 0.82^{+0.13}_{-0.17}$ and $f_{\rm esc}({\rm MUSE}) = 0.75^{+0.18}_{-0.28}$. Using the combined JWST and MUSE data set, we characterize the physical properties and morphology of LCEz4-M1. In our fiducial JWST-only SED fit, the galaxy is compact but has a moderate current galaxy-integrated star formation surface density, $\Sigma_{\rm SFR}=0.38~M_{\odot}\,{\rm yr^{-1}\,kpc^{-2}}$, suggesting that it is not an extreme compact starburst under this fiducial interpretation. While we find no clear evidence for an ongoing major merger for LCEz4-M1, the presence of a faint companion ($\sim 0''5$) detected in the F277W band suggests a potential minor interaction. We also find that LCEz4-M1 may lie in a locally overdense region, although the environmental interpretation remains tentative. Finally, the low ${\rm SFR}_{10\,{\rm Myr}}/{\rm SFR}_{100\,{\rm Myr}}$ ratio, low Ly$\alpha$ EW, and relatively weak rest-frame optical emission lines of LCEz4-M1 may indicate a post-burst LyC-leaking phase.

astro-ph.GA↗

arXiv2026

The Carousel Lens II: Cosmological Constraints with GIGA-Lens

The nature of dark matter and dark energy are among the central questions in cosmology. Strong gravitational lenses with multiple source planes provide a geometric probe of cosmology: the ratio of deflection angles at different redshifts depends only on angular-diameter distances, constraining the matter density $\Omega_m$ and the dark energy equation of state $w$. However, constraints from this technique have historically lagged behind those from the CMB, SNe Ia, and BAO. In this work, we present new cosmological constraints from the Carousel Lens, a cluster-scale lens with more than 40 extended images from 11 spectroscopically confirmed sources. Its relaxed core and rich set of extended images behind the main halo make it particularly suitable for cosmological inference. Using the GIGA-Lens pipeline, we construct a pixel-level lens model including six HST-detected sources and four mass components. From this model, we obtain $w$CDM constraints of $\Omega_m = 0.34^{+0.16}_{-0.13}$ and $w = -1.31^{+0.35}_{-0.32}$ from the Carousel Lens alone, accounting for both statistical and systematic uncertainties. We further project that including four additional known higher-redshift sources, assuming similar fractional uncertainties, could improve the constraining power by ~80%, bringing the precision close to that of the CMB and SNe Ia. For an evolving dark energy model ($w_0w_a$CDM), the Carousel Lens alone yields constraints comparable to the CMB, providing an independent and complementary probe alongside SN Ia and BAO. While currently systematic uncertainties dominate, which we quantify through simulations, our results demonstrate that relaxed multi-source-plane cluster lenses can deliver competitive cosmological constraints. Further improvements are expected from reductions in systematics and from incorporating higher-redshift sources (known and new) with high-resolution imaging.

astro-ph.CO↗

arXiv2026

The Carousel Lens I: A Spectroscopic Survey of the Carousel Lens Field

We present a spectroscopic survey of field galaxies and lensed sources in the vicinity of the strong lensing galaxy cluster known as the Carousel lens at z=0.49. Using both Gemini/GMOS slitmask spectra and deep VLT/MUSE observations, we bring the total number of lensed sources up to 12, including three which were not previously known from imaging observations but are apparent in the MUSE data as emission-line sources. Of these sources, 10 have confident redshifts, and an additional 2 have tentative redshifts from likely Ly$\alpha$ emission (including seven new redshifts determined here adding to those presented previously in \cite{Sheu.Cikota.ea2024}). In total, we identify 42 images of these 12 sources. This lens system is remarkably symmetric and well-modeled by a simpler lens model than typical cluster lenses, and the large number of sources and their large range of redshifts make this cluster ideal for constraining cosmological parameters such as $w$ and $\Omega_m$ as well as the cluster density profile. Additionally, we present a catalog of 57 unlensed field galaxies with confident redshifts, of which 49 are associated with the cluster. We measure a cluster velocity dispersion of about 1100 km s$^{-1}$ from which we estimate a halo mass $M_{200c} \sim 1.2 \times 10^{15} M_\odot$.

astro-ph.GA↗

arXiv2025

A Deep Chandra X-ray Survey of a Luminous Quasar Sample at $z\sim$ 7

We present new Chandra observations of seven luminous quasars at $z>6.5$. Combined with archival Chandra observations of all other known quasars, they form nearly complete X-ray observations of all currently known $z\sim7$ quasars with $M_{1450}<-26.5$, except for J0313$-$1806 at $z=7.642$ and J0910$-$0414 at $z=6.636$. Together with existing ground-based NIR spectroscopy and ALMA observations, we investigate the correlations between X-ray emission (the X-ray luminosity $L_{\rm X}$ and the optical/UV-to-X-ray spectral slope $\alpha_{\rm OX}$) and various quasar properties (rest-UV luminosity $L_{\mathrm{2500\ \mathring{A}}}$, bolometric luminosity $L_{\rm bol}$, C IV blueshift, and infrared luminosity $L_{\rm IR}$). We find most $z>6.5$ quasars follow a similar $\alpha_{\rm OX}-L_{\mathrm{2500\ \mathring{A}}}$ relation as $z\sim1-6$ quasars, but also display a large scatter. We find a potential correlation between $\alpha_{\rm OX}$ and the C IV blueshift, suggesting a soft optical/UV-to-X-ray SED shape is frequently associated with fast disk winds. Furthermore, we analyze the X-ray spectrum of 11 quasars at $z>6.5$ with Chandra detection, and find the best-fit photon index $\Gamma$ is $2.41\pm0.27$, which is likely driven by high accretion rates of $z>6.5$ quasars. In addition, we find there are no significant correlations between either $L_{\rm X}$ and $L_{\rm IR}$, nor $L_{\rm bol}$ and $L_{\rm IR}$, suggesting no strong correlations between quasar luminosity and star formation luminosity for the most luminous quasars at $z>6.5$.

astro-ph.HE↗

arXiv2025

COSMOS-3D: Dense Circumnuclear Gas across Black Hole Growth Phases at z ~ 3

We report the discovery of two broad-line X-ray AGNs (cid_414 and cid_947) at z ~ 3 identified in the JWST Cycle 3 COSMOS-3D program using NIRCam F444W grism spectroscopy. Both exhibit prominent HeI+Pa$\gamma$ emission and absorption, indicative of circumnuclear dense gas that is traced in these systems. Complementary UV and optical spectroscopy in the COSMOS field provides Ly$\alpha$, Si IV, and C IV measurements. Both sources are detected in MIRI F1000W, and cid_414 is also detected in F2100W, indicating hot dust emission. The two AGNs show distinct black hole and obscuration properties. The source cid_414 displays little red dots (LRD)-like V-shape spectra energy distribution (SED) shape with a turnover near the Balmer 4000 {\AA} break, and a narrow Ly$\alpha$ line with $\log L_{\rm Ly\alpha}=42.49\pm0.01~\mathrm{erg\ s^{-1}}$, with no additional metal lines detected. In contrast, cid_947 exhibits a higher HeI absorption column density, larger X-ray--inferred $N_{\rm H}$, lower intrinsic 2--10 keV luminosity, and strong blueshifted features in He I, Si IV, and C IV absorption with velocity offsets exceeding $5000~\mathrm{km\ s^{-1}}$. Photoionization modeling implies gas densities of $\sim10^{9-10} \mathrm{cm^{-3}}$ and sizes comparable to the broad-line region, consistent with dense gas envelopes predicted for LRDs. Together with previous detections of HeI absorption in compact little red dots, these results suggest that dense circumnuclear gas is likely prevalent at high redshift and may regulate obscuration and black hole--host co-evolution across AGN types.

astro-ph.GA↗

arXiv2025

MAMMOTH-Grism: Revisiting the Mass-Metallicity Relation in Protocluster Environments at Cosmic Noon

We present one of the first measurements of the mass-metallicity relation (MZR) in multiple massive protoclusters at cosmic noon, using Hubble Space Telescope (HST) G141 slitless spectroscopy from the MAMMOTH-Grism survey. We identify 63 protocluster member galaxies across three overdense structures at $z = 2\text{-}3$ with robust detections of [OIII], H$\beta$, and [OII] emission. The sample spans gas-phase metallicities of $12 + \log(\text{O/H}) = 8.2\text{-}8.6$, dust-corrected H$\beta$-based star formation rates (SFRs) of $10$-$250\,M_\odot\,\text{yr}^{-1}$, and stellar masses of $M_\ast \sim 10^{9.4}$-$10^{10.5}\,M_\odot$, derived via spectral energy distribution fitting using deep HST and ground-based photometry. We stack spectra in five $M_\ast$ bins to obtain average metallicities and SFRs. Relative to field galaxies at similar redshifts, protocluster members show elevated SFRs at $M_\ast < 10^{10.25}\,M_\odot$ and a systematically shallower MZR: $12 + \log(\text{O/H}) = (6.96 \pm 0.13) + (0.143 \pm 0.017) \times \log(M_{\ast}/M_{\odot})$. We detect a mass-dependent environmental offset: massive protocluster galaxies are metal-poor compared to field counterparts of similar mass, whereas lower-mass systems exhibit comparable or mildly enhanced metallicities. This trend is consistent with a scenario where cold-mode accretion dilutes the interstellar medium (ISM) across the full mass range, while efficient recycling of feedback-driven outflows preferentially enriches the ISM in low-mass galaxies. Finally, we assess the dependence of metallicity offsets on local overdensity and find no significant trend, likely reflecting the survey's bias toward protocluster cores.

astro-ph.GA↗

arXiv2025

Planetary nebulae as tracers of stellar population properties: a pilot study with MUSE

Planetary nebulae (PNe) are the only single stars in galaxies outside the Local Group that can be used as kinematic tracers of the diffuse light in the extended halo. Analysing their luminosity-specific number density across galaxies of different morphologies has also shown hints that they may be used as tracers of the age and metallicity of stellar populations. A proper understanding of this relation has been hindered by the fact that simultaneously detecting PNe and accurately measuring stellar properties is extremely difficult using classical narrow-band imaging methods, which cannot detect PNe in the bright centres of galaxies. In this work, we use integral-field spectroscopy to overcome this challenge, analysing the inner regions of a sample of ten early-type galaxies from the Extended Planetary Nebulae Survey (ePN.S) for which archival MUSE data was available. With the Diffuse Emission-Line Filter (DELF) technique, we automate the detection of PNe, and perform spectral fitting on the diffuse light to infer kinematics and stellar population parameters. We compare the PN number density profile and its associated alpha-parameter with multiple properties of the host galaxies. We find that our sample follows the previously observationally constrained correlation with the metallicity of the host galaxy. We find a weak anti-correlation between the alpha-parameter and the FUV excess, highlighting the possible relation between the visibility lifetime of PNe on the spectral energy distribution of their host galaxies, with fewer PNe detected in association with stellar populations characterized by a UV excess.

astro-ph.GA↗

arXiv2025

Molecular gas content of gravitational-lensed quasars at cosmic noon

Star-forming activity in the host galaxies of high-redshift quasars is crucial to understanding the connection between supermassive black hole (SMBH) activity and galaxy evolution. While most existing studies are biased toward luminous quasars, we conduct carbon monoxide (CO) observations of 17 gravitationally lensed quasars that have four images using the IRAM 30m telescope to investigate the molecular gas content of moderate- to low-luminosity quasars. CO emissions are detected in five out of 17 quasars, corresponding to a detection rate of about 30\%. Analysis of their star formation activity reveals that these quasars live in gas-rich environments but exhibit weaker starbursts and lower star formation efficiencies compared to other luminous high-redshift quasars. In addition, the CO spectral line energy distributions of the two quasars (SDSS J0924+0219, SDSS J1330+1810) are also consistent with mild star formation instead of extreme starbursts. These results suggest that these lensed quasars reside in weaker starburst environments.

astro-ph.GA↗

arXiv2025

JWST COSMOS-3D: Spectroscopic Census and Luminosity Function of [O III] Emitters at 6.75<z<9.05 in COSMOS

We present a catalogue of spectroscopically selected [OIII]+Hb emitters at 6.75<z<9.05 and the resulting [OIII] 5008 \AA Luminosity Function (LF) in the COSMOS field. We leverage the 0.33 deg$^2$ covered by COSMOS-3D using NIRCam/WFSS F444W to perform the largest spectroscopic search for [OIII] emitters at 6.75<z<9.05. We present our catalogue of 249 [OIII] emitters and their associated completeness function. The inferred constraints on the [OIII] LF enable us to characterise the knee of the [OIII] LF, resulting in improved [OIII] LF constraints at z~7,8. Notably, we find evidence for a decline of the [OIII] luminosity density between z~7 and z~8, which could be expected if the metallicity of [OIII] emitters, as well as the cosmic star-formation rate density, is declining at these redshifts. We find that theoretical models that reproduce the z~7,8 [OIII] LF do not reproduce well the [OIII] equivalent width distribution, pointing to potential challenges in the modelling of[OIII] and other nebular lines in the early Universe. Finally, we provide the first constraints on the cosmic variance of [OIII] emitters, estimating at 15% the fractional uncertainty for the z~7,8 [OIII] LF in the 0.33 deg$^2$ field. This estimate is in good agreement with that inferred from clustering, and shows that the [OIII] LF derived from smaller extragalactic legacy fields is strongly affected by cosmic variance. Our results highlight the fundamental role that wide-area JWST slitless surveys play to map the galaxy large-scale structure down into the reionisation era, serving as a springboard for a variety of science cases.

astro-ph.GA↗