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The PHANGS–JWST Treasury Survey: Star Formation, Feedback, and Dust Physics at High Angular Resolution in Nearby GalaxieS
No full textThe PHANGS collaboration has been building a reference data set for the multiscale, multiphase study of star formation and the interstellar medium (ISM) in nearby galaxies. With the successful launch and commissioning of JWST, we can now obtain high-resolution infrared imaging to probe the youngest stellar populations and dust emission on the scales of star clusters and molecular clouds (∼5–50 pc). In Cycle 1, PHANGS is conducting an eight-band imaging survey from 2 to 21 μm of 19 nearby spiral galaxies. Optical integral field spectroscopy, CO(2–1) mapping, and UV-optical imaging for all 19 galaxies have been obtained through large programs with ALMA, VLT-MUSE, and Hubble. PHANGS–JWST enables a full inventory of star formation, accurate measurement of the mass and age of star clusters, identification of the youngest embedded stellar populations, and characterization of the physical state of small dust grains. When combined with Hubble catalogs of ∼10,000 star clusters, MUSE spectroscopic mapping of ∼20,000 H ii regions, and ∼12,000 ALMA-identified molecular clouds, it becomes possible to measure the timescales and efficiencies of the earliest phases of star formation and feedback, build an empirical model of the dependence of small dust grain properties on local ISM conditions, and test our understanding of how dust-reprocessed starlight traces star formation activity, all across a diversity of galactic environments. Here we describe the PHANGS–JWST Treasury survey, present the remarkable imaging obtained in the first few months of science operations, and provide context for the initial results presented in the first series of PHANGS–JWST publications
Hybridization Chain Reaction Lateral Flow Assays for Amplified Instrument-Free At-Home SARS-CoV-2 Testing
No full textThe lateral flow assay format enables rapid, instrument-free, at-home testing for SARS-CoV-2. Due to the absence of signal amplification, this simplicity comes at a cost in sensitivity. Here, we enhance sensitivity by developing an amplified lateral flow assay that incorporates isothermal, enzyme-free signal amplification based on the mechanism of hybridization chain reaction (HCR). The simplicity of the user experience is maintained using a disposable 3-channel lateral flow device to automatically deliver reagents to the test region in three successive stages without user interaction. To perform a test, the user loads the sample, closes the device, and reads the result by eye after 60 min. Detecting gamma-irradiated SARS-CoV-2 virions in a mixture of saliva and extraction buffer, the current amplified HCR lateral flow assay achieves a limit of detection of 200 copies/μL using available antibodies to target the SARS-CoV-2 nucleocapsid protein. By comparison, five commercial unamplified lateral flow assays that use proprietary antibodies exhibit limits of detection of 500 copies/μL, 1000 copies/μL, 2000 copies/μL, 2000 copies/μL, and 20,000 copies/μL. By swapping out antibody probes to target different pathogens, amplified HCR lateral flow assays offer a platform for simple, rapid, and sensitive at-home testing for infectious diseases. As an alternative to viral protein detection, we further introduce an HCR lateral flow assay for viral RNA detection
Irreversible Anion Oxidation Leads to Dynamic Charge Compensation in the Ru-Poor, Li-Rich Cathode Li₂Ru_(0.3)Mn_(0.7)O₃
No full textConventional cathodes for Li-ion batteries are layered transition-metal oxides that support Li⁺ intercalation charge-balanced by redox on the transition metals. Oxidation beyond one electron per transition metal can be achieved in Li-rich layered oxides by involving structural anions, which necessitates high voltages and complex charge compensation mechanisms convoluted by degradation reactions. We report a detailed structural and spectroscopic analysis of the multielectron material Li₂Ru_(0.3)Mn_(0.7)O₃, chosen due to its low Ru content. Ex situ and operando spectroscopic data over multiple cycles highlight the changing charge compensation mechanism. Notably, over half of the first-cycle capacity is attributed to O₂ gas evolution and reversible O redox is minimal. Instead, reduced Ru and Mn species are detected in the bulk and on the surface, which then increasingly contribute to charge compensation as more metal reduction occurs with cycling. Permanent structural changes linked to metal migration are observed with EXAFS and Raman analysis
Submesoscale Dynamics in the Upper Ocean
No full textOceanic motions with spatial scales of 200 m–20 km, called submesoscales, are ubiquitous in the upper ocean and serve as a key intermediary between larger-scale balanced dynamics and unbalanced turbulence. Here, we introduce the fluid dynamics of submesoscales and contrast them with motions at larger and smaller scales. We summarize the various ways in which submesoscales develop due to instabilities that extract potential or kinetic energy from larger-scale balanced currents; some instabilities have counterparts at larger scales, while others are distinct to the submesoscale regime. Submesoscales modify the density stratification in the upper ocean and redistribute energy between scales. These energy transfers are complex, having both up-scale and down-scale components. Submesoscale eddies and fronts also contribute to a spatially heterogeneous distribution of shear and restratification that leave an imprint on upper ocean turbulence. The impact of submesoscales on the Earth's climate remains an exciting research frontier
A low-mass companion desert among intermediate-mass visual binaries: The scaled-up counterpart to the brown dwarf desert
No full textWe present a high-contrast imaging survey of intermediate-mass (1.75–4.5 M_⊙) stars to search the most extreme stellar binaries, i.e. for the lowest mass stellar companions. Using adaptive optics at the Lick and Gemini observatories, we observed 169 stars and detected 24 candidates companions, 16 of which are newly discovered, and all but three are likely or confirmed physical companions. Despite obtaining sensitivity down to the substellar limit for 75 per cent of our sample, we do not detect any companion below 0.3 M_⊙, strongly suggesting that the distribution of stellar companions is truncated at a mass ratio of q_(min) ≳ 0.075. Combining our results with known brown dwarf companions, we identify a low-mass companion desert to intermediate-mass stars in the range 0.02 ≲ q ≲ 0.05, which quantitatively matches the known brown dwarf desert among solar-type stars. We conclude that the formation mechanism for multiple systems operates in a largely scale-invariant manner and precludes the formation of extremely uneven systems, likely because the components of a protobinary accrete most of their mass after the initial cloud fragmentation. Similarly, the mechanism to form 'planetary' (q ≲ 0.02) companions likely scales linearly with stellar mass, probably as a result of the correlation between the masses of stars and their protoplanetary discs. Finally, we predict the existence of a sizable population of brown dwarf companions to low-mass stars and of a rising population of planetary-mass objects towards ≈ 1 M_(Jup) around solar-type stars. Improvements on current instrumentation will test these predictions
Opportunities and challenges in data sharing at multi-user facilities
No full textThe amount of data generated by physics experiments is increasing year by year, and there are growing calls for the data to be open. Sharing data means that the analysis can be done by researchers who were not involved in the original experiment, and can lead to additional insights. However, the practicalities of data sharing vary widely between disciplines, which have diverse needs and face different challenges. In this Viewpoint, scientists from seven multi-user facilities discuss the status of data sharing in their communities
Identifying glitches near gravitational-wave signals from compact binary coalescences using the Q-transform
No full textWe present a computational method to identify glitches in gravitational-wave data that occur nearby gravitational-wave signals from compact binary coalescences. The Q-transform, an established tool in LIGO-Virgo-KAGRA data analysis, computes the probability of any excess in the data surrounding a signal against the assumption of a Gaussian noise background, flagging any significant glitches. Subsequently, we perform validation tests on this computational method to ensure self-consistency in colored Gaussian noise, as well as data that contains a gravitational-wave event after subtracting the signal using the best-fit template. Finally, a comparison of our glitch identification results from real events in LIGO-Virgo’s third observing run against the list of events which required glitch mitigation shows that this tool will be useful in providing precise information about data quality to improve astrophysical analyses of these events
Delay-weighted Calibration: Precision Calibration for 21 cm Cosmology with Resilience to Sky Model Error
No full textOne of the principal challenges of 21 cm cosmology experiments is overcoming calibration error. Established calibration approaches in the field require an exquisitely accurate sky model, and low-level sky model errors introduce calibration errors that corrupt the cosmological signal. We present a novel calibration approach called delay-weighted calibration, or DWCal, which enables precise calibration even in the presence of sky model error. Sky model error does not affect all power spectrum modes equally, and DWCal fits calibration solutions preferentially from error-free modes. We apply this technique to simulated data, showing that it substantially reduces calibration error in the presence of realistic levels of sky model error and can improve 21 cm power spectrum sensitivity by approximately 2 orders of magnitude
The next-to-top term in knot Floer homology
No full textLet K be a null-homologous knot in a generalized L-space Z with b₁(Z) ≤ 1. Let F be a Seifert surface of K with genus g. We show that if HFK(Z,K,[F],g) is supported in a single ℤ/2ℤ-grading, then rank HFK(Z,K,[F],g-1) ≥ rank HFK(Z,K,[F],g)
The AstroSat UV Deep Field North: The Far- and Near-ultraviolet Photometric Catalog
No full textWe present deep UV imaging observations of the Great Observatories Origins Survey Northern (GOODS-N) field with AstroSat/UVIT (AstroSat UV Deep Field north—AUDFn), using one far-UV (FUV) (F154W, 34.0 ks) and two near-UV (NUV) filters (N242W, 19.2 ks; N245M, 15.5 ks). The nature of the UV sky background was explored across the UVIT field, and a global mean and rms were estimated for each filter. We reach 3σ detection limits of m_(AB) ∼ 27.35, 27.28, and 27.02 mag for a point source in the F154W, N242W, and N245M bands respectively. The 50% completeness limits of the FUV and NUV images are m_(AB) = 26.40 and 27.05 mag respectively. We constructed point-spread functions for each band and estimated their FWHM, which were found to be almost the same: 1.″18 in F154W, 1.″11 in N242W, and 1.″24 in N245M. We used SExtractor to separately identify sources in the FUV and NUV filters and produce the UV source catalog of the entire AUDFn field. The source count slope estimated in FUV and NUV is 0.57 dex mag⁻¹ (between 19 and 25 mag) and 0.44 dex mag⁻¹ (between 18 and 25 mag), respectively. The catalog contains 6839 and 16,171 sources (brighter than the 50% completeness limit) in the FUV and NUV, respectively. Our FUV and NUV flux measurements of the identified sources complement existing multiband data in the GOODS-N field, and enable us to probe rest-frame FUV properties of galaxies at redshift z z > 0.97