arXiv subjects

Shude Mao

Publications and source records attributed to Shude Mao.

At least 55 records · Page 3Linked to original sources

arXiv2025

Four Giant Planets from 2024 KMTNet Microlensing Campaign

In this work, we present analyses of four newly discovered planetary microlensing events from the 2024 KMTNet survey season: KMT-2024-BLG-0176, KMT-2024-BLG-0349, KMT-2024-BLG-1870, and KMT-2024-BLG-2087. In each case, the planetary nature was revealed through distinct types of anomalies in the lensing light curves: a positive bump near the peak for KMT-2024-BLG-0176, an asymmetric peak for KMT-2024-BLG-0349, a short-duration central dip for KMT-2024-BLG-1870, and a caustic-crossing feature for KMT-2024-BLG-2087. Detailed modeling of the light curves confirms that these anomalies are produced by planetary companions with planet-to-host mass ratios in the range of $(1.5\text{--}17.9)\times 10^{-3}$. Despite the diversity of signal morphologies, all planets detected in these events are giant planets with masses comparable to or exceeding that of Jupiter in the Solar System. Each planet orbits a host star less massive than the Sun, emphasizing the strength of microlensing in uncovering planetary systems around low-mass stellar hosts.

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arXiv2025

Revisiting the atmosphere of HAT-P-70b with CARMENES high-resolution transmission spectroscopy

Owing to hot and inflated envelopes that facilitate atmospheric studies, ultra-hot Jupiters (UHJs) have attracted much attention. Significant progress has been achieved, from enlarging the sample size to broadening the studies to encompass diverse stellar types and ages. Here, we present a transmission spectroscopy study of HAT-P-70b, an UHJ orbiting a young A-type star, through high-resolution observations with CARMENES at the 3.5m Calar Alto telescope. By using the line-by-line technique, we confirm the previous detections of Ha, Na I, and Ca II, report a new tentative detection of K I, and impose an upper limit on the He triplet absorption. Through cross-correlation analysis, we identify the Ca II and Fe I absorptions, both blue-shifted by approximately 5 km/s, indicating a day-to-night side atmospheric wind. Additionally, we find a new tentative detection of K I. We do not see any significant atmospheric molecular signal in the near-infrared data. Putting HAT-P-70b in the context of UHJs from the literature, it turns out that (1) Ha absorption is more common on gas giants orbiting stars younger than 1 Gyr, with a relative detection probability of $P_{\rm Age<1\,Gyr}({\rm Ha})/P_{\rm Age\geq1\,Gyr}({\rm Ha})\sim 3$; (2) any UHJ is likely to exhibit Fe I absorption if it has Ca II.

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arXiv2025

Metal enrichment of galaxies in a massive node of the Cosmic Web at $z \sim 3$

We present the mass-metallicity relation for star-forming galaxies in the MUSE Quasar Nebula 01 (MQN01) field, a massive cosmic web node at $z \sim 3.245$, hosting one of the largest overdensities of galaxies and AGNs found so far at $z > 3$. Through James Webb Space Telescope (JWST) Near Infrared Spectrograph (NIRSpec) spectra and images from JWST and Hubble Space Telescope (HST), we identify a sample of 9 star-forming galaxies in the MQN01 field with detection of nebular emission lines ($\rm Hβ$, [OIII], $\rm Hα$, [NII]), covering the mass range of $\rm 10^{7.5}M_\odot - 10^{10.5}M_\odot$. We present the relations of the emission-line flux ratios versus stellar mass for the sample and derive the gas-phase metallicity based on the strong line diagnostics of [OIII]$\lambda5008$/$\rm Hβ$ and [NII]$\lambda6585$/$\rm Hα$. Compared to the typical, field galaxies at similar redshifts, MQN01 galaxies show relatively higher [NII]$\lambda6585$/$\rm Hα$ and lower [OIII]$\lambda5008$/$\rm Hβ$ at the same stellar mass, which implies a higher metallicity by about $0.25\pm 0.07$ dex with respect to the field mass-metallicity relation. These differences are decreased considering the ``Fundamental Metallicity Relation'', i.e. if the galaxies' Star Formation Rates (SFR) are also taken into account. We argue that these results are consistent with a scenario in which galaxies in overdense regions assemble their stellar mass more efficiently (or, equivalently, start forming at earlier epochs) compared to field galaxies at similar redshifts.

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arXiv2025

MaNGA DynPop. VII. A Unified Bulge-Disk-Halo Model for Explaining Diversity in Circular Velocity Curves of 6000 Spiral and Early-Type Galaxies

We derive circular velocity curves (CVCs) from stellar dynamical models for $\sim6000$ nearby galaxies in the final data release of the Sloan Digital Sky Survey-IV MaNGA survey with integral-field spectroscopy, exploring connections between the inner gravitational potential (traced by CVC amplitude/shape) and galaxy properties. The maximum circular velocity ($V_{\rm circ}^{\rm max}$) and circular velocity at the half-light radius ($V_{\rm circ}(R_{\rm e}^{\rm maj})$) both scale linearly with the stellar second velocity moment $σ_{\rm e}^2\equiv\langle V^2+σ^2\rangle$ within the half-light isophote, following $V_{\rm circ}^{\rm max} \approx 1.72σ_{\rm e}$ (7$\%$ error) and $V_{\rm circ}(R_{\rm e}^{\rm maj}) \approx 1.62σ_{\rm e}$ (7$\%$ error). CVC shapes (rising, flat, declining) correlate strongly with structural and stellar population properties: declining curves dominate in massive, early-type, bulge-dominated galaxies with old, metal-rich stars and early quenching, while rising CVCs prevail in disk-dominated systems with younger stellar populations and ongoing star formation. Using a unified bulge-disk-halo model, we predict CVC shapes with minimal bias, identifying three governing parameters: bulge-to-total mass ratio ($B/T$), dark matter fraction within $R_{\rm e}$, and bulge Sersic index. The distribution of CVC shapes across the mass-size plane reflects evolutionary pathways driven by (i) in situ star formation (spurring bulge growth) and (ii) dry mergers. This establishes CVC morphology as a diagnostic for galaxy evolution, linking dynamical signatures to structural and stellar population histories.

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arXiv2025

A Comprehensive Analysis of Three Microlensing Planet Candidates with the Planet/Binary Degeneracy

We present observations and analyses of three high-magnification microlensing events: KMT-2022-BLG-0954, KMT-2024-BLG-0697, and MOA-2024-BLG-018. All three exhibit the "Planet/Binary" degeneracy, with planetary solutions corresponding to mass ratios in the range $-3.7 < \log q < -2.2$, while the binary solutions yield $\log q > -2.0$. For KMT-2022-BLG-0954, we identify a previously unrecognized degeneracy among planetary solutions, involving different mass ratios and normalized source radii. In all three cases, single-lens binary-source models are excluded. Bayesian analyses suggest that the planetary solutions correspond to gas giants orbiting M/K dwarfs beyond the snow line, while KMT-2022-BLG-0954 also admits an alternative interpretation as a super-Earth orbiting a late-type M dwarf. The binary solutions imply a diverse set of systems, including M-dwarf pairs and M-dwarf--brown-dwarf binaries. A review of known events subject to the "Planet/Binary" degeneracy shows that in most cases the degeneracy cannot be resolved through follow-up high-resolution imaging, particularly in the presence of the newly identified degeneracy.

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arXiv2025

Introduction to the Chinese Space Station Survey Telescope (CSST)

The Chinese Space Station Survey Telescope (CSST) is an upcoming Stage-IV sky survey telescope, distinguished by its large field of view (FoV), high image quality, and multi-band observation capabilities. It can simultaneously conduct precise measurements of the Universe by performing multi-color photometric imaging and slitless spectroscopic surveys. The CSST is equipped with five scientific instruments, i.e. Multi-band Imaging and Slitless Spectroscopy Survey Camera (SC), Multi-Channel Imager (MCI), Integral Field Spectrograph (IFS), Cool Planet Imaging Coronagraph (CPI-C), and THz Spectrometer (TS). Using these instruments, CSST is expected to make significant contributions and discoveries across various astronomical fields, including cosmology, galaxies and active galactic nuclei (AGN), the Milky Way and nearby galaxies, stars, exoplanets, Solar System objects, astrometry, and transients and variable sources. This review aims to provide a comprehensive overview of the CSST instruments, observational capabilities, data products, and scientific potential.

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arXiv2025

Uncover 3D Dark Matter Distribution of the Milky Way by an Empirical Triaxial Orbit-Superposition Model: Method Validation

We introduce a novel dynamical model, named empirical triaxial orbit-superposition model, for the Milky Way halo. This model relies on minimal physical assumptions that the system is stationary, meaning the distribution function in 6D phase-space does not change when the stars orbiting in the correct gravitational potential. We validate our method by applying it to mock datasets that mimic the observations of the Milky Way halo from LAMOST + Gaia with stars' 3D position and 3D velocity observed. By removing the stellar disk and substructures, correcting the selection function, we obtain a sample of smooth halo stars considered as stationary and complete. We construct a gravitational potential including a highly flexible triaxial dark matter halo with adaptable parameters. Within each specified gravitational potential, we integrate orbits of these halo stars, and build a model by superposing the orbits together taking the weights of stars derived from the selection function correction. The goodness of the models are evaluated by comparing the density distributions as well as 3D velocity distributions numerically represented in the model to that in the data. The shape and radial density distribution of the underlying dark matter halo can be constrained well simultaneously. We apply it to three mock galaxies with different intrinsic shapes of their dark matter halos and achieved accurate recovery of the 3D dark matter density distributions for all.

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arXiv2025

Recovering the pattern speeds of edge-on barred galaxies via an orbit-superposition method

We developed an orbit-superposition method for edge-on barred galaxies and evaluated its capability to recover the bar pattern speed $\rmΩ_p$. We selected three simulated galaxies (Au-18, Au-23, and Au-28) with known pattern speeds from the Auriga simulations and created MUSE-like mock data sets with edge-on views (inclination angles $θ_{\rm T}\ge85^\circ$) and various bar azimuthal angles $φ_{\rm T}$. For mock data sets with side-on bars ($φ_{\rm T}\ge50^\circ$), the model-recovered pattern speeds $\rmΩ_p$ encompass the true pattern speeds $\rmΩ_T$ within the model uncertainties ($1σ$ confidence levels, $68\%$) for 10 of 12 cases. The average model uncertainty within the $1σ$ confidence levels is equal to $10\%$. For mock data sets with end-on bars ($φ_{\rm T}\le30^\circ$), the model uncertainties of $\rmΩ_p$ depend significantly on the bar azimuthal angles $φ_{\rm T}$, with the uncertainties of cases with $φ_{\rm T}=10^\circ$ approaching $\sim30\%$. However, by imposing a stricter constraint on the bar morphology ($p_{\rm bar}\le0.50$), the average uncertainties are reduced to $14\%$ , and $\rmΩ_p$ still encompass $\rmΩ_T$ within the model uncertainties for three of four cases. For all the models that we create in this paper, the $2σ$ ($95\%$) confidence levels of the model-recovered pattern speeds $\rmΩ_p$ always cover the true values $\rmΩ_T$.

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arXiv2025

Dynamical Instability of Multi-planet Systems and Free-floating Planets

The ejection of planets by the instability of planetary systems is a potential source of free-floating planets. We numerically simulate multi-planet systems to study the evolution process, the properties of surviving systems, and the statistics of ejected planets. For systems with only super-Earth planets, we find that the time (in units of the orbital period $P_{1}$ of the innermost planet) for the system to lose the first planet by collision or ejection increases with the semimajor axis of the innermost planet. In contrast, the time (in units of $P_{1}$) for the first close encounter between two planets is identical. These two timescales also depend differently on the orbital spacing between the planets. Most systems with only super-Earths do not have planets ejected. In systems with super-Earths and a cold Jupiter, we discover that a cold Jupiter significantly increases the probability of ejection of the super-Earths by close encounters. Of 38\% of ejected super-Earths, most velocities relative to their parent stars are smaller than $6\ \mathrm{km\ s^{-1}}$. We conservatively estimate that more than 86\% of the surviving two-planet systems in the super-Earths plus cold Jupiter sample are long-term stable by using empirical criteria. Most super-Earths in the remaining two-planet systems are on highly elliptical but stable orbits and have migrated inwards compared with their initial states.

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arXiv2025

A New Brown Dwarf Orbiting an M star and An Investigation on the Eccentricity Distribution of Transiting Long-Period Brown Dwarfs

The orbital eccentricities of brown dwarfs encode valuable information of their formation and evolution history, providing insights into whether they resemble giant planets or stellar binaries. Here, we report the discovery of TOI-5575b, a long-period, massive brown dwarf orbiting a low-mass M5V star ($\rm 0.21\pm0.02\,M_\odot$) delivered by the TESS mission. The companion has a mass and radius of $\rm 72.4\pm4.1\,M_J$ and $\rm 0.84\pm0.07\,R_J$ on a 32-day moderately eccentric orbit ($e=0.187\pm0.002$), making it the third highest-mass-ratio transiting brown dwarf system known to date. Building on this discovery, we investigate the eccentricity distributions of a sample of transiting long-period ($10\leq P\lesssim 1000$ days, $\sim$0.1-1.5 AU) giant planets, brown dwarfs and low-mass stars. We find that brown dwarfs exhibit an eccentricity behavior nearly identical to that of giant planets: a preference for circular orbits with a long tail toward high eccentricities. Such a trend contrasts sharply with direct imaging findings, where cold (5-100 AU) brown dwarfs and giant planets display distinct eccentricity distributions. Our results suggest that transiting long-period brown dwarfs and giant planets probably 1) form in different routes at exterior orbits but undergo analogous dynamical evolution processes and migrate inwards; or 2) both contain two sub-groups, one with widely spread eccentricities while the other has circular orbits, that jointly sculpt the eccentricity distributions. The low-mass-star systems appear to be a distinctive population, showing a peak eccentricity at about 0.3, akin to more massive stellar binaries.

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arXiv2025

Systematic Search for FFPs in KMTNet Full-Frame Images. I. Photometry Pipeline

To exhume the buried signatures of free-floating planets (FFPs) with small angular Einstein radius $θ_{\rm E}$, we build a new full-frame difference image pipeline for the Korean Microlensing Telescope Network (KMTNet) survey based on the newly optimized pySIS package. We introduce the detailed processes of the new pipeline, including frame registration, difference image analysis, and light curve extraction. To test this pipeline, we extract 1-year light curves for 483,068 stars with $I \lesssim 17$ and conduct a model-independent search for microlensing events. The search finds 36 microlensing events, including five new events and six events discovered by other collaborations but missed by previous KMTNet searches. We find that the light curves from the new pipeline are precise enough to be sensitive to FFPs with $θ_{\rm E} \sim 1~μ$as. Using the new pipeline, a complete FFP search on the eight-year KMTNet images can be finished within six months and then yield the FFP mass function. The new pipeline can be used for a new KMTNet AlertFinder system, with significantly reduced false positives.

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arXiv2025

MOA-2022-BLG-091Lb and KMT-2024-BLG-1209Lb: Microlensing planets detected through weak caustic-crossing signals

The light curves of the microlensing events MOA-2022-BLG-091 and KMT-2024-BLG-1209 exhibit anomalies with very similar features. These anomalies appear near the peaks of the light curves, where the magnifications are moderately high, and are distinguished by weak caustic-crossing features with minimal distortion while the source remains inside the caustic. To achieve a deeper understanding of these anomalies, we conducted a comprehensive analysis of the lensing events. We carried out binary-lens modeling with a thorough exploration of the parameter space. This analysis revealed that the anomalies in both events are of planetary origin, although their exact interpretation is complicated by different types of degeneracy. In the case of MOA-2022-BLG-091, the main difficulty in the interpretation of the anomaly arises from a newly identified degeneracy related to the uncertain angle at which the source trajectory intersects the planet-host axis. For KMT-2024-BLG-1209, the interpretation is affected by the previously known inner-outer degeneracy, which leads to ambiguity between solutions in which the source passes through either the inner or outer caustic region relative to the planet host. Bayesian analysis indicates that the planets in both lens systems are giant planets with masses about 2 to 4 times that of Jupiter, orbiting early K-type main-sequence stars. Both systems are likely located in the Galactic disk at a distance of around 4 kiloparsecs. The degeneracy in KMT-2024-BLG-1209 is challenging to resolve because it stems from intrinsic similarities in the caustic structures of the degenerate solutions. In contrast, the degeneracy in MOA-2022-BLG-091, which occurs by chance rather than from inherent characteristics, is expected to be resolved by the future space based Roman RGES microlensing survey.

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arXiv2025

KMT-2022-BLG-1818Lb,c: A Cold Super-Jupiter with a Saturn Sibling

We present the discovery and analysis of the sixth microlensing two-planet system, KMT-2022-BLG-1818Lb,c, detected by a follow-up program targeting high-magnification events. Both planets are subject to the well-known ''Close/Wide'' degeneracy, although for the first planet, which has a super-Jovian mass ratio of $q_2 \simeq 5\times 10^{-3}$ in both solutions, the Close topology, with a normalized separation of $s\simeq 0.70$, is clearly preferred by $Δχ^2=26$. However, contrary to all previous two-planet microlensing systems, the mass ratio for the second planet, $q_3$, is substantially (factor of $\sim 10$) different for the Close and Wide topologies of the first planet. While this degeneracy is resolved in the present case due to high-cadence follow-up observations, the appearance of this new degeneracy indicates the need for caution in the analysis of future two-planet systems. A Bayesian analysis suggests that the host is likely a K-dwarf star in the Galactic disk. The first planet is probably a super-Jupiter on a Jupiter-like orbit, while the second planet is a Saturn-class planet on either a Mercury-like or Saturn-like orbit.

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arXiv2025

Microlensing events indicate that super-Earth exoplanets are common in Jupiter-like orbits

Exoplanets classified as super-Earths are commonly observed on short period orbits, close to their host stars, but their abundance on wider orbits is poorly constrained. Gravitational microlensing is sensitive to exoplanets on wide orbits. We observed the microlensing event OGLE-2016-BLG-0007, which indicates an exoplanet with a planet-to-star mass ratio roughly double the Earth-Sun mass-ratio, on an orbit longer than Saturn's. We combine this event with a larger sample from a microlensing survey to determine the distribution of mass ratios for planets on wide orbits. We infer there are $\sim 0.35$ super-Earth planets per star on Jupiter-like orbits. The observations are most consistent with a bimodal distribution, with separate peaks for super-Earths and gas giants. We suggest that this reflects differences in their formation processes.

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arXiv2025

Systematic KMTNet Planetary Anomaly Search. XII. Complete Sample of 2017 Subprime Field Planets

We report the analysis of four unambiguous planets and one possible planet from the subprime fields ($Γ\leq 1~{\rm hr}^{-1}$) of the 2017 Korea Microlensing Telescope Network (KMTNet) microlensing survey, to complete the KMTNet AnomalyFinder planetary sample for the 2017 subprime fields. They are KMT-2017-BLG-0849, KMT-2017-BLG-1057, OGLE-2017-BLG-0364, and KMT-2017-BLG-2331 (unambiguous), as well as KMT-2017-BLG-0958 (possible). For the four unambiguous planets, the mean planet-host mass ratios, $q$, are $(1.0, 1.2, 4.6, 13) \times 10^{-4}$, the median planetary masses are $(6.4, 24, 76, 171)~M_{\oplus}$ and the median host masses are $(0.19, 0.57, 0.49, 0.40)~M_{\odot}$ from a Bayesian analysis. We have completed the AnomalyFinder planetary sample from the first 4-year KMTNet data (2016--2019), with 112 unambiguous planets in total, which nearly tripled the microlensing planetary sample. The ``sub-Saturn desert'' ($\log q = \left[-3.6, -3.0\right]$) found in the 2018 and 2019 KMTNet samples is confirmed by the 2016 and 2017 KMTNet samples.

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arXiv2025

Systematic Reanalysis of KMTNet Microlensing Events, Paper II: Two New Planets in Giant-Source Events

In this work, we continue to apply the updated KMTNet tender-love care (TLC) photometric pipeline to historical microlensing events. We apply the pipeline to a subsample of events from the KMTNet database, which we refer to as the giant source sample. Leveraging the improved photometric data, we conduct a systematic search for anomalies within this sample. The search successfully uncovers four new planet-like anomalies and recovers two previously known planetary signals. After detailed analysis, two of the newly discovered anomalies are confirmed as clear planets: KMT-2019-BLG-0578 and KMT-2021-BLG-0736. Their planet-to-host mass ratios are $q\sim4\times10^{-3}$ and $q\sim1\times10^{-4}$, respectively. Another event, OGLE-2018-BLG-0421 (KMT-2018-BLG-0831), remains ambiguous. Both a stellar companion and a giant planet in the lens system could potentially explain the observed anomaly. The anomaly signal of the last event, MOA-2022-BLG-038 (KMT-2022-BLG-2342), is attributed to an extra source star. Within this sample, our procedure doubles the number of confirmed planets, demonstrating a significant enhancement in the survey sensitivity.

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arXiv2025

A negative stellar mass$-$gaseous metallicity gradient relation of dwarf galaxies modulated by stellar feedback

Baryonic cycling is reflected in the spatial distribution of metallicity within galaxies, yet gas-phase metallicity distribution and its connection with other properties of dwarf galaxies are largely unexplored. We present the first systematic study of radial gradients of gas-phase metallicities for a sample of 55 normal nearby star-forming dwarf galaxies (stellar mass $M_\star$ ranging from $10^7$ to $10^{9.5}\ M_\odot$), based on MUSE spectroscopic observations. We find that metallicity gradient shows a significant negative correlation (correlation coefficient $r \approx -0.56$) with $\log M_\star$, in contrast to the flat or even positive correlation observed for higher-mass galaxies. This negative correlation is accompanied by a stronger central suppression of metallicity compared to the outskirts in lower-mass galaxies. Among the other explored galaxy properties-including baryonic mass, star formation distribution, galaxy environment, regularity of the gaseous velocity field, and effective yield of metals $y_{\rm eff}$-only the velocity field regularity and $y_{\rm eff}$ show residual correlation with the metallicity gradient after controlling for $M_\star$, in the sense that galaxies with irregular velocity fields or lower $y_{\rm eff}$ tend to have less negative or more positive gradients. Particularly, a linear combination of $\log M_\star$ and $\log y_{\rm eff}$ significantly improves the correlation with metallicity gradient ($r \approx -0.68$) compared to $\log M_\star$ alone. The lack of correlation with environment disfavors gas accretion as a dominant factor. Our findings imply that metal mixing and transport processes, including but not limited to feedback-driven outflows, are more important than in-situ metal production in shaping the metallicity distribution of dwarf galaxies.

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arXiv2025

MOA-2020-BLG-135Lb: A New Neptune-class Planet for the Extended MOA-II Exoplanet Microlens Statistical Analysis

We report the light-curve analysis for the event MOA-2020-BLG-135, which leads to the discovery of a new Neptune-class planet, MOA-2020-BLG-135Lb. With a derived mass ratio of $q=1.52_{-0.31}^{+0.39} \times 10^{-4}$ and separation $s\approx1$, the planet lies exactly at the break and likely peak of the exoplanet mass-ratio function derived by the MOA collaboration (Suzuki et al. 2016). We estimate the properties of the lens system based on a Galactic model and considering two different Bayesian priors: one assuming that all stars have an equal planet-hosting probability and the other that planets are more likely to orbit more massive stars. With a uniform host mass prior, we predict that the lens system is likely to be a planet of mass $m_\mathrm{planet}=11.3_{-6.9}^{+19.2} M_\oplus$ and a host star of mass $M_\mathrm{host}=0.23_{-0.14}^{+0.39} M_\odot$, located at a distance $D_L=7.9_{-1.0}^{+1.0}\;\mathrm{kpc}$. With a prior that holds that planet occurrence scales in proportion to the host star mass, the estimated lens system properties are $m_\mathrm{planet}=25_{-15}^{+22} M_\oplus$, $M_\mathrm{host}=0.53_{-0.32}^{+0.42} M_\odot$, and $D_L=8.3_{-1.0}^{+0.9}\; \mathrm{kpc}$. This planet qualifies for inclusion in the extended MOA-II exoplanet microlens sample.

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