arXiv subjects

M. Lee

Publications and source records attributed to M. Lee.

At least 19 recordsLinked to original sources

arXiv2026

Extended [CII] gas emission in and around a massive quiescent galaxy at z=7.3

We report the discovery of [CII] 158 micron emission in and around the most distant known massive quiescent galaxy RUBIES-UDS-QG-z7 at z = 7.27. Observed with ALMA in band 6, the [CII] line independently confirms the spectroscopic redshift from JWST/NIRSpec spectra at low and medium resolution. The emission extends over an effective radius R_eff,[CII] = 8 +/- 3 kpc, well beyond the compact stellar body traced by JWST/NIRCam (R_eff = 209 (+33/-24) pc), with a significant fraction of approximately 70% of the flux arising from a circumgalactic halo. No dust continuum is detected at rest-frame ~160 micron, setting an upper limit on the infrared luminosity of L_IR < 1.4 x 10^11 Lsun, overall consistent with expectations from rest-frame UV to near-infrared SED modeling under energy balance. Converting the galaxy-scale [CII] emission into cold gas mass, we find log(M_mol/Msun) = 9.53 (+0.32/-0.31) and log(M_HI/Msun) = 9.46-10.34, depending on the assumed calibration and metallicity. Despite being approximately 10x more gas-poor than typical star-forming galaxies at fixed redshift, stellar mass, and [CII] to gas mass conversion, RUBIES-UDS-QG-z7 retains a substantial cold gas reservoir with fractions f_gas >~ 20% and long depletion timescales across most assumptions. The extended [CII] halo carries approximately twice as much gas as the galaxy alone and shows a blueshifted velocity offset consistent with the tentative gas outflow detected in MgII absorption in previous work, suggesting a past episode of AGN-driven gas expulsion possibly linked to the suppression of star formation. The presence of a large gas reservoir in and around a massive quiescent galaxy just 700 Myr after the Big Bang implies that whatever mechanism is suppressing star formation must be remarkably effective at maintaining a low star formation efficiency on ~100 Myr timescales, even in the presence of abundant fuel.

astro-ph.GA↗

arXiv2026

The Murchison Widefield Array Phase III upgrade: Sensitivity Doubled, Number of Baselines Quadrupled, Flexibility Enhanced, and EoR Observations Optimised

We describe the latest iteration of upgrades (designated Phase III) to the Murchison Widefield Array (MWA), in the fourth paper in a series that covers the evolution of the telescope from design concept to initial operational facility, and through two major upgrades. As part of the Phase III upgrade of the MWA, we report the completion of work to design, build, and deploy a new fleet of digital receivers that further optimise the MWA for Epoch of Reionisation observations. These receivers complement existing receivers, such that the MWA now supports the full correlation of all 256 antenna tiles currently in the array. This step releases the MWA from the prior constraint of having to correlate only 128 of the 256 tiles at any given time, which means that the maximum instantaneous sensitivity of the MWA is doubled and the maximum number of interferometric baselines is approximately quadrupled. The upgrade is fundamentally enabled by the new MWAX correlator and various other improvements to the MWA sub-systems. In this paper we describe the new digital receivers and the other improvements that result in the Phase III system. A range of operational benefits arise from the upgrade and scientific flexibility is increased. We also comment on the transition from the MWA to the SKA-Low facility near the end of the decade, including a description of some unique science opportunities utilising joint MWA/SKA-Low data during the Science Verification phase of the SKA-Low Array Assembly 2 (AA2) period.

astro-ph.IM↗

arXiv2025

Search for low-mass electron-recoil dark matter using a single-charge sensitive SuperCDMS-HVeV Detector

We present constraints on low-mass dark matter electron scattering and absorption interactions using a SuperCDMS high-voltage eV-resolution (HVeV) detector. Data were taken underground in the NEXUS facility located at Fermilab with an overburden of 225 meters of water equivalent. The experiment benefits from the minimizing of luminescence from the printed circuit boards in the detector holder used in all previous HVeV studies. A blind analysis of $6.1\,\mathrm{g\cdot days}$ of exposure produces exclusion limits for dark matter-electron scattering cross sections for masses as low as $1\,\mathrm{MeV}/c^2$, as well as on the photon-dark photon mixing parameter and the coupling constant between axionlike particles and electrons for particles with masses $>1.2\,\mathrm{eV}/c^2$ probed via absorption processes.

hep-ex↗

arXiv2025

Multi-channel, multi-template event reconstruction for SuperCDMS data using machine learning

SuperCDMS SNOLAB uses kilogram-scale germanium and silicon detectors to search for dark matter. Each detector has Transition Edge Sensors (TESs) patterned on the top and bottom faces of a large crystal substrate, with the TESs electrically grouped into six phonon readout channels per face. Noise correlations are expected among a detector's readout channels, in part because the channels and their readout electronics are located in close proximity to one another. Moreover, owing to the large size of the detectors, energy deposits can produce vastly different phonon propagation patterns depending on their location in the substrate, resulting in a strong position dependence in the readout-channel pulse shapes. Both of these effects can degrade the energy resolution and consequently diminish the dark matter search sensitivity of the experiment if not accounted for properly. We present a new algorithm for pulse reconstruction, mathematically formulated to take into account correlated noise and pulse shape variations. This new algorithm fits N readout channels with a superposition of M pulse templates simultaneously - hence termed the N$\times$M filter. We describe a method to derive the pulse templates using principal component analysis (PCA) and to extract energy and position information using a gradient boosted decision tree (GBDT). We show that these new N$\times$M and GBDT analysis tools can reduce the impact from correlated noise sources while improving the reconstructed energy resolution for simulated mono-energetic events by more than a factor of three and for the 71Ge K-shell electron-capture peak recoils measured in a previous version of SuperCDMS called CDMSlite to $<$ 50 eV from the previously published value of $\sim$100 eV. These results lay the groundwork for position reconstruction in SuperCDMS with the N$\times$M outputs.

physics.ins-det↗

arXiv2025

Low-Energy Calibration of SuperCDMS HVeV Cryogenic Silicon Calorimeters Using Compton Steps

Cryogenic calorimeters for low-mass dark matter searches have achieved sub-eV energy resolutions, driving advances in both low-energy calibration techniques and our understanding of detector physics. The energy deposition spectrum of gamma rays scattering off target materials exhibits step-like features, known as Compton steps, near the binding energies of atomic electrons. We demonstrate a successful use of Compton steps for sub-keV calibration of cryogenic silicon calorimeters, utilizing four SuperCDMS High-Voltage eV-resolution (HVeV) detectors operated with 0 V bias across the crystal. This new calibration at 0 V is compared with the established high-voltage calibration using optical photons. The comparison indicates that the detector response at 0 V is about 30% weaker than expected, highlighting challenges in detector response modeling for low-mass dark matter searches.

physics.ins-det↗

arXiv2025

Revealing electron-electron interactions in graphene at room temperature with the quantum twisting microscope

The Quantum Twisting Microscope (QTM) is a groundbreaking instrument that enables energy- and momentum-resolved measurements of quantum phases via tunneling spectroscopy across twistable van der Waals heterostructures. In this work, we significantly enhance the QTMs resolution and extend its measurement capabilities to higher energies and twist angles by incorporating hexagonal boron nitride (hBN) as a tunneling dielectric. This advancement unveils previously inaccessible signatures of the dispersion in the tunneling between two monolayer graphene (MLG) sheets, features consistent with a logarithmic correction to the linear Dirac dispersion arising from electron-electron (e-e) interactions with a fine-structure constant of alpha = 0.32. Remarkably, we find that this effect, for the first time, can be resolved even at room temperature, where these corrections are extremely faint. Our results underscore the exceptional resolution of the QTM, which, through interferometric interlayer tunneling, can amplify even subtle modifications to the electronic band structure of two-dimensional materials. Our findings reveal that strong e-e interactions persist even in symmetric, nonordered graphene states and emphasize the QTMs unique ability to probe spectral functions and their excitations of strongly correlated ground states across a broad range of twisted and untwisted systems.

cond-mat.mes-hall↗

arXiv2025

DeepDive: A deep dive into the physics of the first massive quiescent galaxies in the Universe

We present the DeepDive program, in which we obtained deep JWST/NIRSpec G235M/F170LP spectra for ten primary massive ($\log{(M_\star/M_\odot)}=10.8-11.5$) quiescent galaxies at $z\sim3-4$. A novel reduction procedure was used to extend the nominal wavelength coverage of G235M beyond H$\alpha$ and [NII] at $z\sim 4$, revealing weak, narrow H$\alpha$ lines indicative of low star formation rates. Two out of ten primary targets have broad H$\alpha$ lines, indicating the presence of active galactic nuclei. We also conducted an archival search of quiescent galaxies observed with NIRSpec gratings in the DAWN JWST Archive, providing a statistical context for interpreting the DeepDive targets. This archival search provided a spectroscopic sample of 126 quiescent galaxies spanning $1<z<5$, selected by high Dn4000, UVJ color, or low specific star formation rate, and covering more than an order of magnitude in stellar mass. This sample allowed us to revisit the sample from the different selections, finding $\sim90\%$ overlap between these criteria. The total sample of 136 quiescent galaxies from this study shows that those at $z\sim3-5$, including the DeepDive targets, typically exhibit weaker breaks and bluer colors than their lower-redshift counterparts, indicating generally younger stellar populations. Stacked spectra of sources grouped by the Dn4000 index reveal faint iron and magnesium absorption line features in the stellar continuum even for the low Dn4000 subsample at high redshift ($z\sim3$). In addition, higher Dn4000 subsamples show fainter nebular emission lines. These results demonstrate that medium-resolution NIRSpec spectroscopy is essential for robustly characterizing the diversity and evolution of early quiescent galaxies. The large sample constructed in this paper will allow a statistical census of the properties of quiescent galaxies at high redshift to be obtained.

astro-ph.GA↗

arXiv2025

Intelligent Product 3.0: Decentralised AI Agents and Web3 Intelligence Standards

Twenty-five years ago, the specification of the Intelligent Product was established, envisaging real-time connectivity that not only enables products to gather accurate data about themselves but also allows them to assess and influence their own destiny. Early work by the Auto-ID project focused on creating a single, open-standard repository for storing and retrieving product information, laying a foundation for scalable connectivity. A decade later, the approach was revisited in light of low-cost RFID systems that promised a low-cost link between physical goods and networked information environments. Since then, advances in blockchain, Web3, and artificial intelligence have introduced unprecedented levels of resilience, consensus, and autonomy. By leveraging decentralised identity, blockchain-based product information and history, and intelligent AI-to-AI collaboration, this paper examines these developments and outlines a new specification for the Intelligent Product 3.0, illustrating how decentralised and AI-driven capabilities facilitate seamless interaction between physical AI and everyday products.

cs.NI↗

arXiv2025

ALMA Band 3 Selection of Ultra-high Redshift Dropouts: The final challenge to {\Lambda}CDM

The Lyman-break technique has been used to successfully identify high-redshift candidates in broad-band photometric data in the rest-frame optical and NIR using the dropout technique. We pioneer the application of this technique to new wavelength regimes, and search for dropouts in combined ALMA and JWST data. We find a candidate that is undetected in NIRCam imaging including and blueward of the F444W filter, but clearly identified in ALMA band 3. Assuming this is a Lyman-break candidate, we measure a redshift in the range $40 < z < 21\,380$. This is the highest redshift galaxy candidate discovered to date, and is in significant tension with current and future predictions from cosmological simulations, with implications for galaxy evolution in the (very) early Universe.

astro-ph.GA↗

arXiv2025

A merging pair of massive quiescent galaxies at $z=3.44$ in the Cosmic Vine

We report the spectroscopic confirmation of a merging pair of massive quiescent galaxies at $z=3.44$. Using JWST observations, we confirm that the two galaxies lie at a projected separation of 4.5 kpc with a velocity offset of $\sim 680\, {\rm km\, s^{-1}}\ (\delta_z \sim 0.01)$. The pair resides in the core of a known rich overdensity of galaxies, dubbed the "Cosmic Vine". For both pair members, modeling of the Spectral Energy Distributions and faint rest-frame optical emission lines indicate high stellar masses ($\log{(M_\star/M_\odot)}\sim10.9$) and suppressed star formation ($\log{\rm (sSFR/yr^{-1})}<-10$), more than an order of magnitude below the level of the star formation main sequence at this redshift. We then explore the Illustris-TNG simulation and the GAEA and SHARK semi-analytical models to examine whether they produce a pair of massive quiescent galaxies akin to that of the Cosmic Vine. While all models produce close pairs of massive quiescent galaxies at $2 90\%$ of simulated pairs in the models that we analyzed merge by $z=0$, our findings suggest that our observed pair will likely coalesce into a single massive galaxy. The merger, occurring in the dense core of a large-scale structure, might represent a critical event in the formation of a brightest cluster galaxy and the morphological transformation of high-redshift disky quiescent galaxies into early-type ellipticals.

astro-ph.GA↗

arXiv2025

Gas outflows in two recently quenched galaxies at z = 4 and 7

Outflows are a key element in the baryon cycle of galaxies, and their properties provide a fundamental test for our models of how star formation quenches in galaxies. Here we report the detection of outflowing gas in two recently quenched, massive ($M_\star\sim10^{10.2}M_\odot$) galaxies at z=4.106 (NS_274) and z=7.276 (RUBIES-UDS-QG-z7) observed with JWST/NIRSpec. The outflows are traced by blue-shifted MgII absorption lines, and in the case of the z=4.1 system, also by FeII and NaI features. The spectra of the two sources are similar to those of local post-starburst galaxies, showing deep Balmer features and minimal star formation on 10 Myr timescales as traced by the lack of bright emission lines, also suggesting the absence of a strong and radiatively efficient AGN. The galaxies' SFHs are consistent with an abrupt quenching of star formation, which continued at rates of $\sim15\,M_\odot$/yr averaged over 100 Myr timescales. Dedicated millimeter observations of NS_274 constrain its dust obscured SFR to $<12\,M_\odot$/yr. Under simple geometrical assumptions, we derive mass loading factors $\lesssim1$ and $>10$ for the z=4.1 and z=7.3 systems, respectively, and similarly different energies carried by the outflows. Supernova feedback can account for the mass and energy of the outflow in NS_274. However, the low mass loading factor and average gas velocity suggest that the observed outflow is likely not the primary factor behind its quenching. SF-related processes seem to be insufficient to explain the extreme mass outflow rate of RUBIES-UDS-QG-z7, which would require an additional ejective mechanism such as an undetected AGN. Finally, the average outflow velocities per unit $M_\star$, SFR, or its surface area are consistent with those of lower-redshift post-starburst galaxies, suggesting that outflows in rapidly quenched galaxies might occur similarly across cosmic time. [Abridged]

astro-ph.GA↗

arXiv2025

Possible quantum spin liquid state of CeTa$_7$O$_{19}$

CeTa$_7$O$_{19}$ is a recently found two-dimensional triangular lattice antiferromagnet without showing magnetic order. We grew high-quality CeTa$_7$O$_{19}$ single crystals and studied the low-temperature magnetic susceptibility, specific heat and thermal conductivity. The dc magnetic susceptibility and magnetization reveal its nature of effective spin-1/2, easy axis anisotropy, and antiferromagnetic spin coupling. The ultralow-temperature ac susceptibility and specific heat data indicate the absence of any phase transition down to 20 mK. The ultralow-temperature thermal conductivity ($\kappa$) at zero magnetic field exhibits a non-zero residual term $\kappa_0/T =$ 0.0056 W/K$^2$m. Although the magnetic field dependence of $\kappa$ is rather weak, the 14 T thermal conductivity shows an essential zero residual term. All these results point to a possible ground state of quantum spin liquid.

cond-mat.str-el↗

arXiv2025

A large-scale ring galaxy at z = 2.2 revealed by JWST/NIRCam: kinematic observations and analytical modelling

A unique galaxy at z = 2.2, zC406690, has a striking clumpy large-scale ring structure that persists from rest UV to near-infrared, yet has an ordered rotation and lies on the star-formation main sequence. We combine new JWST/NIRCam and ALMA band 4 observations, together with previous VLT/SINFONI integral field spectroscopy and HST imaging to re-examine its nature. The high-resolution H$\alpha$ kinematics are best fitted if the mass is distributed within a ring with total mass $M_{\rm{ring}} = 2 \times 10^{10} M_\odot$ and radius $R_{ring}$ = 4.6 kpc, together with a central undetected mass component (e.g., a "bulge") with a dynamical mass of $M_{bulge} = 8 \times 10^{10} M_\odot$. We also consider a purely flux emitting ring superposed over a faint exponential disk, or a highly "cuspy" dark matter halo, both disfavored against a massive ring model. The low-resolution CO(4-3) line and 142GHz continuum emission imply a total molecular and dust gas masses of $M_{mol,gas} = 7.1 \times 10^{10}M_\odot$ and $M_{dust} = 3 \times 10^8 M_\odot$ over the entire galaxy, giving a dust-to-mass ratio of 0.7%. We estimate that roughly half the gas and dust mass lie inside the ring, and that $\sim 10\%$ of the total dust is in a foreground screen that attenuates the stellar light of the bulge in the rest-UV to near-infrared. Sensitive high-resolution ALMA observations will be essential to confirm this scenario and study the gas and dust distribution.

astro-ph.GA↗

arXiv2024

Light Dark Matter Constraints from SuperCDMS HVeV Detectors Operated Underground with an Anticoincidence Event Selection

This article presents constraints on dark-matter-electron interactions obtained from the first underground data-taking campaign with multiple SuperCDMS HVeV detectors operated in the same housing. An exposure of 7.63 g-days is used to set upper limits on the dark-matter-electron scattering cross section for dark matter masses between 0.5 and 1000 MeV/$c^2$, as well as upper limits on dark photon kinetic mixing and axion-like particle axioelectric coupling for masses between 1.2 and 23.3 eV/$c^2$. Compared to an earlier HVeV search, sensitivity was improved as a result of an increased overburden of 225 meters of water equivalent, an anticoincidence event selection, and better pile-up rejection. In the case of dark-matter-electron scattering via a heavy mediator, an improvement by up to a factor of 25 in cross-section sensitivity was achieved.

hep-ex↗

arXiv2024

High-yield fabrication of bubble-free magic-angle twisted bilayer graphene devices with high twist-angle homogeneity

Magic-angle twisted bilayer graphene (MATBG) stands as one of the most versatile materials in condensed-matter physics due to its hosting of a wide variety of exotic phases while also offering convenient tunability. However, the fabrication of MATBG is still manual, and remains to be a challenging and inefficient process, with devices being highly dependent on specific fabrication methods, that often result in inconsistency and variability. In this work, we present an optimized protocol for the fabrication of MATBG samples, for which we use deterministic graphene anchoring to stabilize the twist-angle, and a careful bubble removal techniques to ensure a high twist-angle homogeneity. We use low-temperature transport experiments to extract the average twist-angle between pairs of leads. We find that up to 38 percent of the so fabricated devices show micrometer square sized regions with a twist-angle in the range 1.1 plus/minus 0.1 degrees, and a twist-angle variation of only 0.02 degrees, where in some instances such regions were up to 36 micrometer square large. We are certain that the discussed protocols can be directly transferred to non-graphene materials, and will be useful for the growing field of moire materials.

cond-mat.mes-hall↗

arXiv2024

COSMOS-Web: The Role of Galaxy Interactions and Disk Instabilities in Producing Starbursts at z<4

We study of the role of galaxy-galaxy interactions and disk instabilities in producing starburst activity in galaxies out to z = 4. For this, we use a sample of 387 galaxies with robust total star formation rate measurements from Herschel, gas masses from ALMA, stellar masses and redshifts from multi-band photometry, and JWST/NIRCam rest-frame optical imaging. Using mass-controlled samples, we find an increased fraction of interacting galaxies in the starburst regime at all redshifts out to z = 4. This increase correlates with star formation efficiency (SFE), but not with gas fraction. However, the correlation is weak (and only significant out to z = 2), which could be explained by the short duration of SFE increase during interaction. In addition, we find that isolated disk galaxies make up a significant fraction of the starburst population. The fraction of such galaxies with star-forming clumps ("clumpy disks") is significantly increased compared to the main-sequence disk population. Furthermore, this fraction directly correlates with SFE. This is direct observational evidence for a long-term increase of SFE maintained due to disk instabilities, contributing to the majority of starburst galaxies in our sample and hence to substantial mass growth in these systems. This result could also be of importance for explaining the growth of the most massive galaxies at z > 6.

astro-ph.GA↗

arXiv2024

Primordial Rotating Disk Composed of $\geq$15 Dense Star-Forming Clumps at Cosmic Dawn

Early galaxy formation, initiated by the dark matter and gas assembly, evolves through frequent mergers and feedback processes into dynamically hot, chaotic structures. In contrast, dynamically cold, smooth rotating disks have been observed in massive evolved galaxies merely 1.4 billion years after the Big Bang, suggesting rapid morphological and dynamical evolution in the early Universe. Probing this evolution mechanism necessitates studies of young galaxies, yet efforts have been hindered by observational limitations in both sensitivity and spatial resolution. Here we report high-resolution observations of a strongly lensed and quintuply imaged, low-luminosity, young galaxy at $z=6.072$ (dubbed the Cosmic Grapes), 930 million years after the Big Bang. Magnified by gravitational lensing, the galaxy is resolved into at least 15 individual star-forming clumps with effective radii of $r_{\rm e}\simeq$ 10--60 parsec (pc), which dominate $\simeq$ 70\% of the galaxy's total flux. The cool gas emission unveils a smooth, underlying rotating disk characterized by a high rotational-to-random motion ratio and a gravitationally unstable state (Toomre $Q \simeq$ 0.2--0.3), with high surface gas densities comparable to local dusty starbursts with $\simeq10^{3-5}$ $M_{\odot}$/pc$^{2}$. These gas properties suggest that the numerous star-forming clumps are formed through disk instabilities with weak feedback effects. The clumpiness of the Cosmic Grapes significantly exceeds that of galaxies at later epochs and the predictions from current simulations for early galaxies. Our findings shed new light on internal galaxy substructures and their relation to the underlying dynamics and feedback mechanisms at play during their early formation phases, potentially explaining the high abundance of bright galaxies observed in the early Universe and the dark matter core-cusp problem.

astro-ph.GA↗

arXiv2024

The cold interstellar medium of a normal sub-$L^\star$ galaxy at the end of reionization

We present the results of a ~60-hr observational campaign with ALMA targeting a spectroscopically confirmed and lensed sub-$L^\star$ galaxy at z=6.07, identified during the ALMA Lensing Cluster Survey (ALCS). We sample the dust continuum emission from rest frame 90 to 370 $\mu$m at six different frequencies and set constraining upper limits on the molecular gas line emission and content via CO(7-6) and [CI](2-1) for two lensed images with $\mu\gtrsim20$. Complementing these sub-mm observations with deep optical and near-IR photometry and spectroscopy with JWST, we find this galaxy to form stars at a rate of SFR~7 Msun/yr, ~50-70% of which is obscured by dust. This is consistent with what is expected for a $M_\star$~7.5$\times10^{8}$ Msun object by extrapolating the $M_\star$-obscured SFR fraction relation at z<2.5 and with observations at 5<z<7. The dust temperature of ~50K is similar to that of more massive galaxies at similar redshifts, although with large uncertainties and with possible negative gradients. We measure a dust mass of $M_{\rm dust}$~1.5$\times10^6$ Msun and, by combining [CI], [CII], and a dynamical estimate, a gas mass of ~2$\times10^9$ Msun. Their ratio is in good agreement with the predictions from models in the literature. The $M_{\rm dust}$/$M_\star$ fraction of ~0.002 and the young stellar age are consistent with dust production via supernovae. Also, models predict a number density of galaxies with $M_{\rm dust}\sim10^{6}$ Msun at z=6 in agreement with our estimate from the parent ALCS survey. The combination of lensing and multiwavelength observations allow us to probe luminosity regimes up to two orders of magnitude lower than what has been explored so far for field galaxies at similar redshifts. Our results serve as a benchmark for future observations of faint sub-$L^\star$ galaxy population that might have driven the reionization of the Universe. [Abridged]

astro-ph.GA↗