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Physics Astrophysics

astro-ph Watch Astrophysics

Wednesday 12 August

Solar and Stellar Astrophysics

Astronomical Cardiology II: A Search For Heartbeat Stars Using APOGEE and TESS

Jowen Callahan, D. M. Rowan, C. S. Kochanek et al. (+1 more)

Stellar binaries in short-period, highly eccentric systems with significant tidal deformations near pericenter, also known as heartbeat stars, are a laboratory for studying dynamical tides and oscillations in stars. We identify 50 heartbeat stars using TESS light curves of stars identified as binaries using SDSS APOGEE. We fit their phase-folded TESS light curves with an analytic model to measure their orbital periods, eccentricities, inclinations, and arguments of periastron. We measure the mass function of targets with enough APOGEE radial velocity observations to obtain a constraint on the secondary mass. We confirm our previous results that the non-giant heartbeat stars have started to evolve off the main sequence and that the fraction of (near) main sequence binaries that are heartbeat stars rises rapidly with effective temperature.
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All authors Jowen Callahan, D. M. Rowan, C. S. Kochanek, M. M. Fausnaugh

Astrophysics of Galaxies

Trace the Self-Gravitating Gas Using CO Isotopologues

Linjing Feng, Jingwen Wu, Sihan Jiao et al. (+12 more)

Recent studies have shown that the star formation rate (SFR) correlates tightly and linearly with the mass of gravitationally bound gas, which can be delineated from the power-law tail of the column-density probability distribution function ($N$-PDF) derived from dust emission observations. This relationship holds across four orders of magnitude within the Milky Way–spanning low-mass to high-mass star-forming regions and encompassing the extreme environment of the Central Molecular Zone. Building on this framework, we present a new approach for estimating the mass of gravitationally bound gas in molecular clouds using multi-line CO isotopologue observations. Our sample includes 16 molecular clouds with robust detections in $^{12}$CO, $^{13}$CO, and C$^{18}$O $J$ = 1-0, spanning both massive inner Galaxy clouds and nearby star-forming regions. We find that the $N$-PDFs derived from combined CO isotopologue data recover the characteristic log-normal plus power-law profiles seen in dust-based studies. The mass and spatial distribution of the self-gravitating structures estimated from both dust-based and CO-based methods agree well throughout the sample. This indicates that the CO isotopologue combination can robustly trace the self-gravitating component via the $N$-PDF method and provides a reliable, scalable, and velocity-resolved alternative to dust emission for identifying the star-forming gas in molecular clouds.
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All authors Linjing Feng, Jingwen Wu, Sihan Jiao, Zhi-Yu Zhang, Junzhi Wang, Chao-Wei Tsai, Di Li, Hauyu Baobab Liu, Yan Sun, Neal J. Evans II, Yuxin Lin, Hao Ruan, Fangyuan Deng, Yuanzhen Xiong, Ruofei Zhang

Astrophysics of Galaxies

FLAGS II: Constraining Galaxy Formation Models with Dimensionality Reduction of Direct Observables

Jack C. Turner, Stephen M. Wilkins, William J. Roper et al. (+1 more)

Comparisons between observations of galaxies and theoretical predictions are regularly performed using physical properties, which are inferred by the often slow and biased process of SED fitting. Forward modelling facilitates a reliable alternative, whereby models are evaluated using direct observables alone. However, these datasets become high-dimensional when collating observations from multiple telescopes, leading to sparse sampling, memory intensity and visualisation difficulties. We show that 2D embeddings of JWST and HST photometric fluxes, constructed using the non-linear dimensionality reduction algorithm UMAP, preserve sufficient information to differentiate between five models. Using a simple $\chi^{2}$-like metric, we show that JAGUAR reproduces the population of bright galaxies $(m_{\mathrm{AB}}<26)$ in GOODS-S six times as well as SC-SAM and twelve times as well as SAGE. By adjusting the hyperparameters, we quantify how well each model replicates the distribution of SED shapes. The template SED approach of SPRITZ and the lack of photoionisation in SAGE cause significant discrepancies, highlighting the importance of comprehensive forward modelling. The embedded position of each galaxy can be identified $>100$ times faster than inferring its properties with Bayesian SED fitting, making this approach an ideal alternative for deriving statistical model constraints from large surveys such as LSST and Euclid, and performing simulation-based inference with CAMELS.
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All authors Jack C. Turner, Stephen M. Wilkins, William J. Roper, Aswin P. Vijayan

Instrumentation and Methods for Astrophysics

Don't Cut Corners: How Training Outside the Prior Makes Simulation-Based Inference More Robust

Chaipat Tirapongprasert and Matthew Ho

Large astrophysical simulation campaigns often generate training data by sampling parameters across a Uniform prior box. Due to the proposal's sharp edge, neural posterior estimators struggle to learn accurate approximations near the boundaries. We propose Tailed-Uniform, a family of hybrid proposal distributions for sampling training simulations for robust simulation-based inference. By padding the original hard-truncated training box with decaying tails, Tailed-Uniform-trained networks yield more accurate posteriors near and beyond the edges. We demonstrate these improvements on a family of tail shapes, including a widened Uniform box as a control. Our results suggest that additional simulations near the prior boundary better constrain the networks as it approaches the edge of the training box, even for Uniform assumed priors. We show these advantages on a toy problem and cosmological parameter inference from the matter power spectrum. These benefits increase in high dimensions, where boundaries dominate parameter space volume.
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Cosmology and Nongalactic Astrophysics · Cross-listed from gr-qc

Thermal false vacuum decay near black holes is aspherical

D. S. Gorbunov, D. G. Levkov and V. E. Maslov

We study decay of a scalar field false vacuum near a (3+1)-dimensional Schwarzschild black hole equilibrated at Hawking temperature with the environment. Our scalar field model has negative quartic self-coupling and thereby resembles Higgs sector of the Standard Model in the large-field limit. We demonstrate that if the black hole is not too small, the false vacuum in this model decays aspherically with regard to the black hole center: via formation of expanding true vacuum bubbles emerging on the outer side of the event horizon. More specifically, we identify three regimes of the decay. For the largest and coldest black holes, the main mechanism is quantum tunneling described by an infinitesimally thin bounce sitting at some point of the horizon. In the intermediate-mass regime, the vacuum is destroyed by thermal fluctuations creating aspherical critical bubbles in the horizon vicinity. Finally, near the smallest black holes thermal fluctuations still guide the decay but the dominant critical bubble is spherically symmetric and covers the entire horizon.
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Astrophysics of Galaxies

Why is GN-z11 Bright, Compact, and Nitrogen Enhanced? Insights from UV Absorption and Emission Diagnostics

Minami Nakane and Masami Ouchi

We investigate the UV spectrum of GN-z11, a luminous, compact galaxy with strong nitrogen lines, at $z=10.60$, using deep JWST/NIRSpec high-resolution IFU and medium-resolution MSA spectra assembled from the JADES, SPURS, and GO programs. After optimized reduction and extraction of the IFU data including an evaluation of statistical and systematic uncertainties, we obtain mutually consistent spectra from the high- and medium-resolution observations. After carefully accounting for the data quality limitations, we identify prominent P-Cygni profiles in NV$\lambda\lambda1238,1243$, SiIV$\lambda\lambda1394,1403$, and CIV$\lambda\lambda1548,1550$, together with broad NIV]$\lambda\lambda1483,1486$ emission (FWHM $\sim1600$ km s$^{-1}$). The P-Cygni profiles resemble those of massive stars such as O-type stars and luminous blue variables (LBVs), while the broad NIV] emission resembles that of nitrogen-sequence Wolf-Rayet (WN) stars. We fit stellar and active galactic nuclei (AGN) UV spectral models and find that the stellar models are strongly preferred over the AGN models ($\Delta$WAIC $=-25$), with the preference driven primarily by the NV P-Cygni profile. These results indicate that the luminous, compact UV continuum of GN-z11 is dominated by massive stars. We derive electron densities from CIII]$\lambda\lambda1907,1909$, NIII]$\lambda\lambda1747-1754$, and NIV], with the nitrogen diagnostics extending well beyond the CIII]-based limit and reaching densities of $\gtrsim10^{6.5}$ cm$^{-3}$ for NIV], indicating physically distinct carbon- and nitrogen-emitting nebular components. These findings suggest that the apparent nitrogen enhancement inferred for GN-z11 as a whole may arise when strong narrow nitrogen emission originates from dense gas locally enriched in nitrogen by WN stellar winds and photoionized by nearby massive stars within the same star-forming region.
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High Energy Astrophysical Phenomena

Interacting Supernovae: a Radio and X-ray Strategy to Constrain the Structure of the Circumstellar Medium

Shunke Ai, Irene Tamborra and Leonardo Dinoi

The interaction of supernova (SN) ejecta with the dense circumstellar medium (CSM) converts shock kinetic energy into radiation across multiple wavebands. We investigate the dependence of the X-ray and radio emission on the CSM geometry, considering spherical, hourglass, and disk shapes for the CSM. We find that the spectral and light-curve properties, both in X-ray and radio, significantly differ for spherical and non-spherical CSM structures. For a non-spherical CSM, the radio light curve flattens out near the peak frequency, due to efficient free-free absorption by the unshocked CSM. Moreover, the early rise of the radio light curve is shallower when the CSM density along the observer line of sight is larger than that in other directions. If the CSM density is lower along the observer line of sight, the radio light curve flattens near its peak, and the reverse-shock component is negligible in X-rays. Building on these features, we provide a method to constrain the CSM structure based on the rising part the radio light curve in the proximity of its peak; we show that the decay part of the radio light curve, after its peak, carries insight on whether the CSM density profile is wind-like or not. We further adopt the X-ray signal to corroborate the information extracted from radio. We test our strategy on SN 1993j and SN 2023ixf. For both SNe, we find that an asymmetric CSM is in excellent agreement with radio and X-ray observations and provides a viable alternative to non-wind scenarios suggested in the literature. Our findings highlight the crucial insight provided by radio and X-ray signals into the mass-loss history of the SN progenitor.
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Astrophysics of Galaxies

Recycled Gas Dominates the Metal-rich Fuel of Supermassive Black Holes

Dongyun Kwak, Ena Choi, Hannah Jhee et al. (+5 more)

Understanding the origin and chemical properties of gas accreted by supermassive black holes (SMBHs) is essential for linking black hole growth to galaxy evolution. Using a suite of 30 high-resolution cosmological zoom-in simulations, we investigate the chemical properties of gas accreted onto SMBHs in massive galaxies with stellar masses of $10^{10.9-11.9}\,\rm M_\odot$ and black hole masses of $10^{8.5-9.7}\,\rm M_\odot$ at $z=0$. By tracing the full cosmological histories of individual gas particles, we identify their origins and enrichment pathways. The accreted gas is classified into four categories: “early” gas accreted during the early assembly phase of the main halo, “external” gas originating from other galaxies or subhalos, “recycled” gas enriched through stellar evolution processes within the primary galaxy, including asymptotic giant branch (AGB) winds and supernova ejecta, and “smooth” gas accreted from the intergalactic medium. We find that recycled gas dominates the accretion budget and is already metal rich at early epochs. Gas from other origins typically undergoes gradual chemical enrichment within the galactic environment prior to black hole accretion. The mean abundance ratios show only weak redshift evolution and are broadly compatible with the high metallicities inferred for quasar broad-line regions. Our results suggest that metal-rich gas supply to SMBHs arises naturally from cosmological galaxy evolution and stellar recycling.
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All authors Dongyun Kwak, Ena Choi, Hannah Jhee, Rachel S. Somerville, Thorsten Naab, Michaela Hirschmann, Jaejin Shin, Jong-Hak Woo

Astrophysics of Galaxies

The Ĝ Infrared Search for Extraterrestrial Civilizations with Large Energy Supplies. V. When Galaxies Glow with Industry

Olivia Curtis, Aidan J. Rowland, Jason T. Wright et al. (+3 more)

We present the most robust stellar population synthesis (SPS)-based search for galaxy-spanning technological waste heat to date, applied to 129 nearby galaxies spanning a wide range of spectral energy distribution (SED) types, including ultraluminous IR galaxies and MIR-luminous active galactic nuclei (AGN). We incorporate the AGENT Dyson sphere formalism into the Flexible Stellar Population Synthesis code at the stellar population level, so nebular and dust emission respond self-consistently to Dyson sphere reprocessing. With Prospector, we perform a suite of 1,419 injection recovery tests across a range of covering fractions, $\alpha$, where we successfully recover the injected covering fractions (best-fit slope $m = 0.92$) and detect them through Bayesian model selection down to $\alpha \sim 4$–$5\%$ in quiescent galaxies. None of our 129 galaxies prefer a Dyson sphere component, and we place the first per-galaxy 95% upper limits on warm ($T_{\rm BB} \gtrsim 100$K) swarms, reaching a median $\alpha < 0.3\%$ across quiescent hosts without a dominant AGN. Our injection-calibrated detection rates convert these zero detections into a population bound of $<2.6\%$ of galaxies hosting $\alpha = 25\%$ swarms ($95\%$ confidence). Because survey colors cannot separate waste heat from starbursts and AGN, we develop a scaffold for future searches, running from inexpensive archival screens such as the Balmer decrement and the stellar-to-dynamical-mass offset a swarm leaves behind, through resolved fitting with nuclear excision, to PRIMA FIR photometry that makes targeted JWST imaging decisive. We find that the outskirts of quiescent galaxies are the best hunting grounds for future technosignature searches.
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All authors Olivia Curtis, Aidan J. Rowland, Jason T. Wright, Caryl Gronwall, Jakob M. Helton, Joel Leja

Earth and Planetary Astrophysics

Climates of Gl 514 b

Héctor E. Delgado Díaz, Rory Barnes, Russell Deitrick et al. (+2 more)

The continuous discovery of exoplanets, each with distinctive stellar and planetary properties, along with the development of higher resolution ground and space telescopes has positioned climate evolution as a fundamental component of the study of habitability. In particular, the planet Gl 514 b, located within the habitable zone of an M0.5 dwarf star 7.62 pc from Earth, is a candidate for direct observations with future ground and space-based telescopes and therefore worthy of climate modeling. One notable aspect of this planet is its eccentricity of $e = 0.45^{+0.15}_{-0.14}$, which could affect the seasonal climate by inducing large swings in instellation over the course of an orbit. Hence, we simulate a plausible range of climates on this planet to assess the likelihood that its surface is habitable as well as estimate the surface ice coverage, which could affect the photometric signal. To perform these simulations, we use an energy balance model to explore the parameter space permitted by the observations and the allowed ranges of the obliquity, eccentricity, atmospheric CO$_2$, precession angle, land fraction, and land distribution. We find the planet is most likely to be in either a snowball or ice free state, but about 1.27% of our simulations contain polar ice caps or an ice belt. A partial pressure of CO$_2$ in the range of 7.25-9.5 bar permits the planet's surface to be habitable. These results constrain the orbital, rotational, and physical conditions required for surface habitability of Gl 514 b and will help guide future direct-imaging surveys of this and similar planets.
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All authors Héctor E. Delgado Díaz, Rory Barnes, Russell Deitrick, Mario Damasso, Nathaniel Brown

Astrophysics of Galaxies

From Cluster Cores to the Low-Density Field: Strong Environmental Quenching of Galaxy Star Formation at Low Redshift

Mohamed H. Abdullah, A. E. Abdelaziz, Gillian Wilson et al. (+3 more)

We investigate how galaxy star formation activity depends on environment using a sample of 81,647 SDSS galaxies selected over $0.03\leq z\leq0.075$ and $9.7\leq\log_{10}(M_\star/h^{-2}M_\odot)\leq11.0$, including 18,426 members from 572 clusters in the GalWCat19 catalog. We characterize environment in two complementary ways: (1) nearest-neighbor density for the full sample, and (2) clustercentric radius and host halo mass for GalWCat19. The sSFR distribution remains bimodal across all environments, with distinct quenched and star-forming components. As local density increases, the quenched component becomes more prominent, while the characteristic sSFR of the star-forming component decreases by approximately $0.29$–$0.35$ dex from the lowest- to highest-density classes. Within clusters, the quenched fraction decreases with increasing projected clustercentric radius, while the star-forming peak shifts by approximately $0.42$ dex toward lower sSFR from the outskirts to the inner cluster region. This extends the picture from previous studies, in which environmental trends are primarily associated with changes in the quenched fraction, by showing that galaxies remaining in the star-forming population also exhibit systematically suppressed sSFR in denser environments. The dependence on host halo mass is weaker and is most apparent among lower-stellar-mass galaxies in the inner cluster regions. By measuring the environmental quenching efficiency at fixed stellar mass, we find excess quenching in cluster environments beyond that expected from stellar-mass quenching alone. These results show that environment is associated not only with an increased probability of quenching, but also with suppressed star formation among galaxies that remain star forming, with local density and clustercentric radius showing the strongest associations.
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All authors Mohamed H. Abdullah, A. E. Abdelaziz, Gillian Wilson, Ahmed M. Abdelbar, M. M. Beheary, Y. H. M. Hendy

Astrophysics of Galaxies

CHANG-ES XL: Magnetic Field Structures in the Disk and Halo of NGC 891

N. Pourjafari, J. M. Stil, R.-J. Dettmar et al. (+11 more)

We present new Karl G. Jansky Very Large Array S-band (2-4 GHz) observations of the edge-on spiral galaxy NGC 891, complemented by C-band data, to investigate the structure of its radio continuum halo. Using rotation measure synthesis we detected an extended polarized halo, with most spatially extended polarized emission confined to Faraday depths within +/- 150 rad m-2. We identified a localized region in the north-east side of the galaxy that shows an enhancement in polarized intensity (not in percentage polarization). By combining the radio data with H-alpha and diffuse X-ray maps, we discuss a possible origin for this structure: a superbubble powered by clustered supernovae. Across the disk and halo, the percentage polarization decreases toward the midplane but shows a mild wavelength dependence, despite the edge-on orientation of NGC 891. This behavior implies that the depolarization cannot be dominated by small-scale Faraday rotation within the disk. Instead, it is possible that most of the observed polarized emission arises on the Earth-facing side of the galaxy. Our peak rotation measure (RM) map shows a smooth transition along the major axis, consistent with a large scale axisymmetric magnetic field. Using H-alpha and UV data, we analyzed the distribution of H II regions and found that they are parts of different spiral arms. We also identified a faint, isolated H II region at a galactocentric radius of 16.9 kpc, with both H-alpha and far-UV counterparts, indicating star formation outside the thin disk.
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All authors N. Pourjafari, J. M. Stil, R.-J. Dettmar, P. Kamphuis, R. Beck, J. English, V. Heesen, J. Irwin, J.-T. Li, L.-Y. Lu, S. Ranasinghe, M. Stein, Q. D. Wang, T. Wiegert

Solar and Stellar Astrophysics

Hemispheric Asymmetry of Solar Active Regions Arises from a Nested Population

Aimee A. Norton

We investigate the longitude–time distribution of NOAA active regions (ARs) during Solar Cycles 22–24 and find statistically significant North–South asymmetry in AR emergence. Using an activity-nest identification algorithm, we show that this asymmetry is concentrated in the subset of ARs that participate in nests. Nest-member ARs exhibit substantially larger hemispheric asymmetry than either the full AR population or the non-nest population, and the asymmetry is largely removed when nest-member ARs are excluded. Monte Carlo tests with randomized longitudes and temporal perturbations show that the observed nesting and asymmetry exceed random expectations, implying that $\sim$6–18% of ARs participate in a non-random, hemispherically asymmetric nesting component. This asymmetry is associated with temporally offset bursts of activity and distinct longitudinal clustering between the hemispheres, leading to reduced cross-equatorial coherence in the longitude–time distribution of solar ARs. Intervals of enhanced nesting activity and hemispheric asymmetry broadly coincide with enhanced hemispheric quasi-biennial variability and temporal evolution of the large-scale solar magnetic field, suggesting a possible connection between intermediate-timescale dynamo variability and the hemispheric organization of solar activity.
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Astrophysics of Galaxies

The Delay Time Distribution of Quasi-Periodic Eruptions

Margaret Shepherd, K. Decker French, Jason T. Hinkle et al. (+4 more)

Quasi-periodic eruptions (QPEs) are quasi-periodic X-ray bursts observed in the nucleus of a galaxy. Multiple pieces of observational evidence link QPEs to tidal disruption events (TDEs), which occur when stars are disrupted after approaching a supermassive black hole too closely. Post-starburst galaxies are overrepresented among the host galaxies of both TDEs and QPEs, though the mechanism causing this overrepresentation is unknown. While their physical origin is unclear, the delay time distribution (DTD) of QPEs, or rate of QPEs as a function of time since a burst of star formation, can constrain what mechanisms influence the QPE rate and possible QPE formation channels. We compile a catalog of 10 QPE host galaxies with optical spectra, model the stellar populations with Bagpipes, and retrieve the age of the most recent burst of star formation to construct the DTD of QPEs. We find that the QPE rate increases with post-burst age to reach a peak at ~1 Gyr relative to a control sample, similar to the observational TDE DTD, though we cannot rule out a flat distribution of burst ages relative to a control sample. However, the fraction of QPE host galaxies with high (>1%) burst mass fractions is larger than the fraction of galaxies with high burst mass fractions in either a sample of TDE host galaxies or a sample of control galaxies. If the preferred QPE formation channel requires extreme mass ratio inspirals (EMRIs), then such EMRIs may be more readily produced by large, ~1-Gyr-old bursts of star formation.
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All authors Margaret Shepherd, K. Decker French, Jason T. Hinkle, Ferdinand, Samaresh Mondal, Yashasvi Moon, Margaret E. Verrico

Astrophysics of Galaxies

A systematic comparison of green valley selection criteria across multiparameter spaces using a homogeneous ultraviolet-optical dataset

Pius Privatus and Umananda Dev Goswami

We present a systematic comparison of commonly adopted green valley (GV) selection criteria by examining their distributions across multiple observational and physical parameter spaces. Using a homogeneous ultraviolet-optical dataset constructed from the Galaxy Evolution Explorer (GALEX) and the Sloan Digital Sky Survey (SDSS), we construct GV samples based on rest-frame $u-r$ and NUV$-r$ colours, specific star formation rate, and the $D_n(4000)$ spectral index. These samples are analysed in colour–stellar mass, colour–magnitude, and star formation rate–stellar mass diagrams. We find that the different selection criteria identify statistically distinct subsets of GV galaxies occupying different regions of parameter space. Ultraviolet-based selections are compact in NUV$-r$ colour space but shift toward optically red galaxies and lower star formation activity in the star formation rate–stellar mass plane. The $u-r$-selected sample is more tightly confined in optical colour space but is biased toward higher star formation rates, whereas the $D_n(4000)$-based selection yields the most heterogeneous population. In contrast, the sSFR-selected GV sample exhibits the most consistent behaviour across all parameter spaces. Despite these differences, all selection methods span a similar stellar mass range, indicating that the observed variations arise primarily from differences in star formation activity rather than stellar mass. The relatively small overlap between the different selection criteria demonstrates that GV identification is strongly diagnostic-dependent and that the commonly adopted one-dimensional definitions are not interchangeable. These results highlight the importance of combining complementary diagnostics to obtain a more complete and physically meaningful picture of transitional galaxy populations.
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Astrophysics of Galaxies

Evidence for the First Globular Cluster Stellar Stream beyond the Milky Way

Julie Kiel Holm, Sarah Pearson, Jacob Nibauer et al. (+5 more)

The dark matter content of ultra-diffuse galaxies is the subject of considerable debate. Stellar streams, which form when a host galaxy tidally strips stars from an orbiting stellar system, provide a powerful technique to constrain the dark matter content of external galaxies. The stripped stars form long, thin leading and trailing tidal arms that persist for billions of years. Stellar streams from globular clusters are particularly sensitive probes of dark matter halos and substructure. Globular cluster streams are expected to exist in a variety of host galaxy types, but so far, they have only been observed in the Milky Way. We present evidence for the first extragalactic globular cluster stellar stream, identified in deep Hubble Space Telescope imaging of the ultra-diffuse galaxy, UGC9050-Dw1. The stream's morphology, colour, and apparent association with a compact source support the globular cluster progenitor interpretation observationally, and we reproduce the observed surface brightness with simulated globular cluster stellar populations. We use generative stream modelling, which fits dynamical models directly to the stream morphology, to constrain the mass of the progenitor and present the first stream-based halo constraint for an ultra-diffuse galaxy. The stream models point to a globular cluster origin and suggest a massive dark matter host halo. By extending the reach of globular cluster stream analysis to external galaxies, this work opens a new chapter in dark matter science.
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All authors Julie Kiel Holm, Sarah Pearson, Jacob Nibauer, David J. Sand, Adrian M. Price-Whelan, Tjitske Starkenburg, David Hendel, Catherine Fielder

High Energy Astrophysical Phenomena

High-energy neutrino signatures of embedded GRB jets in AGN disks: a dynamic jet-propagation framework

Wei-Cheng Long and Yun-Wei Yu

Relativistic jets embedded in active galactic nucleus (AGN) accretion disks are promising high-energy neutrino sources, but their emission is often estimated from a single representative jet state. We develop a time-dependent framework that follows jet-head propagation, evolving reverse-shock conditions, and particle cooling until the jet chokes or breaks out, and apply it to the SG and TQM disk models. For the representative choked cases, neutrino emission is dominated by the high-dissipation phase near jet stalling, allowing a stalling-state approximation to reproduce the trajectory-integrated, detector-weighted event yield within approximately $14\%$. In breakout cases, however, rapid jet-head acceleration across steep disk-density gradients suppresses reverse-shock dissipation and can cause single-state estimates to overpredict the fluence, even after accounting for the available energy budget. Full trajectory integration also reshapes the high-energy spectral tail and produces distinct detectability patterns across SMBH mass and disk radius for the two disk models. Some lower-density outer-disk cases develop harder tails extending into the 10–100 PeV range, motivating future ultra-high-energy neutrino searches. Resolving jet propagation dynamics is therefore indispensable for evaluating embedded transients across AGN disk environments and avoiding systematic biases in multi-messenger modeling.
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Instrumentation and Methods for Astrophysics

LIGO Detector Characterization in the Second and Third Parts of the Fourth Observing Run

J. Glanzer, A. F. Helmling-Cornell, A. Calafat et al. (+244 more)

LIGO detector characterization efforts enabled the confident detection of gravitational waves from hundreds of compact binary coalescences during the fourth observing run. Reliable production of high quality detector data and rapid noise mitigation efforts allow the extraction of the most in-depth knowledge of gravitational wave sources and their progenitors. In this paper we describe LIGO detector characterization activities during the second and third parts of O4-O4b and O4c. We summarize changes in detector configuration and performance at the LIGO Hanford and LIGO Livingston Observatories between the end of the first part of O4a and the end of O4c, including upgrades made during the commissioning break preceding O4b and during repairs performed in O4c. We describe instrumental investigations carried out at both sites designed to understand and subsequently mitigate the effect on detector sensitivity of transient glitches, narrowband spectral lines, and vibration-driven noise, among other data quality concerns. We then review the tools and procedures used to validate gravitational wave candidates and the data quality products thus supplied to searches for gravitational waves from compact binary coalescences and unmodeled transients, continuous gravitational waves, and the stochastic gravitational wave background. The efforts of the detector characterization group are essential for maintaining and improving the sensitivity and reliability of the LIGO detectors especially as observing runs lengthen and more events are detected. We conclude with prospects for LIGO detector characterization activities in future observing runs.
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All authors J. Glanzer, A. F. Helmling-Cornell, A. Calafat, S. R. Callos, E. Capote, A. Effler, T. A. Ferreira, E. Goetz, A. M. Knee, J. R. Mérou, D. Malakar, B. Mannix, D. Nandi, K. Pham, R. M. S. Schofield, P. Sharma, Z. Yarbrough, N. Arnaud, B. K. Berger, K. Burtnyk, C. M. Compton, G. Connolly, D. Davis, F. Di Renzo, G. Grant, J. C. Martins, G. Mo, A. Neunzert, L. K. Nuttall, J. Oberling, J. R. Olson, S. Soni, M. Trevor, R. Abbott, I. Abouelfettouh, R. X. Adhikari, A. Ahuja, S. Álvarez-López, A. Ananyeva, S. Appert, S. K. Apple, K. Arai, J. Areeda, N. Aritomi, S. M. Aston, M. Ball, S. W. Ballmer, D. Barker, L. Barsotti, J. Betzwieser, Z. S. Bhalla, D. Bhattacharjee, G. Billingsley, S. Biscans, C. D. Blair, N. Bode, E. Bonilla, V. Bossilkov, A. Branch, A. F. Brooks, D. D. Brown, R. Bruntz, J. Bryant, C. Cahillane, H. Cao, C. Chatterjee, N. Christensen, F. Clara, J. Collins, R. Cottingham, D. C. Coyne, R. Crouch, J. Csizmazia, A. Cumming, L. P. Dartez, N. Demos, E. Dohmen, K. L. Dooley, J. C. Driggers, S. E. Dwyer, A. Ejlli, T. Etzel, M. Evans, J. Feicht, R. Frey, W. Frischhertz, P. Fritschel, V. V. Frolov, M. Fuentes-Garcia, P. Fulda, M. Fyffe, D. Ganapathy, B. Gateley, T. Gayer, J. A. Giaime, K. D. Giardina, R. Goetz, G. Gonzalez, A. W. Goodwin-Jones, S. Gras, C. Gray, D. Griffith, H. Grote, T. Guidry, J. Gurs, E. D. Hall, J. Hanks, J. Hanson, M. C. Heintze, N. A. Holland, N.-T. Howard, D. Hoyland, H. Y. Huang, B. Hughey, Y. Inoue, A. L. James, A. Jamies, K. Jani, R. Jaume, A. Jennings, W. Jia, D. H. Jones, H. B. Kabagoz, S. Kandhasamy, S. Karat, S. Karki, M. Kasprzack, K. Kawabe, N. Kijbunchoo, P. J. King, J. S. Kissel, K. Komori, A. Kontos, R. Kumar, K. Kuns, M. Landry, B. Lantz, M. Laxen, K. Lee, M. Lesovsky, F. Llamas Villarreal, E. Lofquist-Fabris, M. Lormand, B. R. Lott, H. A. Loughlin, R. Macas, M. MacInnis, C. N. Makarem, G. L. Mansell, R. M. Martin, K. Mason, F. Matichard, N. Mavalvala, N. Maxwell, G. McCarrol, R. McCarthy, D. E. McClelland, S. McCormick, J. McIver, R. McNeil, T. McRae, F. Mera, E. L. Merilh, F. Meylahn, R. Mittleman, S. Mohan S, D. Moraru, G. Moreno, A. Mullavey, M. Nakano, T. J. N. Nelson, S. A. Nichols, J. Notte, T. O'Hanlon, R. Oram, C. Osthelder, D. J. Ottaway, H. Overmier, W. Parker, O. Patane, A. Pele, S. Perry, H. Pham, M. Pirello, J. Pullin, V. Quetschke, K. E. Ramirez, K. Ransom, J. Reyes, J. W. Richardson, K. Riles, M. Robinson, J. G. Rollins, C. L. Romel, J. H. Romie, M. P. Ross, B. I. Rotimi, K. Ryan, T. Sadecki, A. Sanchez, E. J. Sanchez, L. E. Sanchez, R. L. Savage, D. Schaetzl, M. G. Schiworski, R. Schnabel, E. Schwartz, D. Sellers, T. Shaffer, R. W. Short, D. Sigg, B. J. J. Slagmolen, J. R. Smith, C. Soike, V. Srivastava, T. Starkman, L. Sun, D. B. Tanner, J. Tasson, M. Thomas, P. Thomas, K. A. Thorne, E. M. Todd, M. R. Todd, C. I. Torrie, G. Traylor, A. S. Ubhi, R. P. Udall, G. Vajente, J. Vanosky, A. Vecchio, P. J. Veitch, A. M. Vibhute, E. R. G. von Reis, J. Warner, B. Weaver, R. Weiss, C. Whittle, P. Wilcox, B. Willke, C. C. Wipf, J. L. Wright, V. A. Xu, H. Yamamoto, L. Zhang, Z. Zhang, M. E. Zucker

Solar and Stellar Astrophysics

Nascent Embedded-protostar Survey in Taurus (NEST) I: Protostellar Multiplicity

Aislinn C. Plante, John J. Tobin, Patrick D. Sheehan et al. (+5 more)

We present new ALMA 0.9 mm and VLA 9 mm observations in the Taurus Molecular Cloud (TMC) of 25 protostellar systems, containing 40 protostars, observed at 0.3" (~20 au) resolution. Within separations of 18-10,000 au, the ALMA/VLA-observed Taurus sample has a multiplicity fraction (MF), defined as the fraction of systems with at least one companion, of 0.50 +/- 0.07, and a companion fraction (CF), defined as the average number of companions per system, of 0.58 +/- 0.20. To build a more complete census of protostellar multiplicity in this region, we supplement the observed sample with 24 protostars (12 protostellar systems and 5 additional companions associated with systems we observed) previously identified through archival infrared or ALMA observations. Together, these 64 individual protostars (37 systems) define our Taurus+ sample, for which we measure higher values of 0.53 +/- 0.06 and 0.72 +/- 0.19 for the MF and CF, respectively. These multiplicity statistics in the TMC are notably higher than those reported in the more clustered star-forming regions of Orion and Perseus at the ~3-4 sigma level, suggesting that Taurus may preserve a larger fraction of primordial multiples. The separation distributions in our samples show populations of both close and wide multiples, but a deficit at intermediate separations of 200-300 au. This pattern may suggest two distinct formation pathways: close binaries (<200 au) arising primarily from disk fragmentation, and wide multiples (>1000 au) from core fragmentation.
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All authors Aislinn C. Plante, John J. Tobin, Patrick D. Sheehan, Noshin Yesmin, Nicholas P. Ballering, Tyler L. Bourke, Josh Eisner, Zhi-Yun Li

Cosmology and Nongalactic Astrophysics · Cross-listed from gr-qc

Robustness of the primordial power spectrum in hybrid loop quantum cosmology to approximations near the bounce

Kristina Giesel, Almudena Guillén, Guillermo A. Mena Marugán et al. (+1 more)

We prove the robustness of the analytic approximation used in (hybrid) loop quantum cosmology to compute the primordial power spectrum of the cosmological perturbations for a recently proposed vacuum state (the non-oscillatory state with asymptotic Hamiltonian diagonalization). To investigate this, we study different approximations to the effective mass of these perturbations near the bounce, showing that the Pöschl-Teller potential employed in previous works leads to indistinguishable power spectra compared to other estimations of the mass, provided that they successfully capture the characteristic scale of the bounce, which translates into a scale of power suppression.
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All authors Kristina Giesel, Almudena Guillén, Guillermo A. Mena Marugán, Leonardo Ricci

High Energy Astrophysical Phenomena

Impact of Neutrino Flavour Conversion on the Diffuse Neutrino Background from Neutrino-dominated Accretion Flows

Yun-Feng Wei and Tong Liu

Neutrino-dominated accretion flows (NDAFs) are believed to form during the fallback accretion phase of some core-collapse supernovae (CCSNe). Such systems produce copious neutrino emission, whose cumulative contribution over cosmic history forms the diffuse NDAF neutrino background (DNNB). As neutrinos propagate from the source to Earth, flavour conversion can significantly modify the observed neutrino spectra and consequently the detectability of the DNNB. In this work, based on fallback CCSN simulations, we investigate the effects of progenitor mass, metallicity, and initial explosion energy on neutrino emission from NDAFs. We calculate the heavy-lepton neutrino ($\nu_x$) spectra from NDAFs and incorporate them into DNNB predictions. We find that the unoscillated $\nu_x$ spectra are more than an order of magnitude lower than those of electron antineutrinos $\bar{\nu}_e$. Using the latest neutrino oscillation parameters reported by the Jiangmen Underground Neutrino Observatory (JUNO), we evaluate the impact of flavour conversion on the DNNB and derive the corresponding spectra for both the normal and inverted mass orderings. We further estimate the expected event numbers in JUNO and Hyper-Kamiokande. We find that the predicted DNNB signal is strongly dependent on the neutrino mass ordering. While the DNNB may be detectable in the normal ordering with next-generation neutrino detectors, the signal is significantly suppressed in the inverted ordering, making detection considerably more challenging.
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Astrophysics of Galaxies

The Shape of the Vertical Action Distribution Locates the Scatterers that Heat the Galactic Disc

Yuan-Sen Ting and Hans-Walter Rix

The Milky Way's stellar disc is thicker than the cold gas layer from which its stars form. What scatters stars onto orbits with greater vertical motion remains unresolved. Scatterers could fill the disc volume, as bending waves or dark substructure would, or could be confined to the midplane, as giant molecular clouds are. Scattering from a midplane layer occurs only during the fast plane-crossing phase and becomes less effective as that speed increases, whereas a volume-filling perturbation remains effective near the slow turning points. We derive the distribution of vertical action this leaves behind, for any height distribution of scatterers. The geometry turns out to enter only through the logarithmic slope of the diffusivity in action, $D\propto J_z^{b}$, and solving the Fokker-Planck equation gives $p(J_z)\propto\exp[-(J_z/J_0)^{2-b}]$. Scatterers that fill the volume give $b=1$ and an exponential, a thin layer at the midplane gives $b=1/2$ and a sharper cutoff: the shape of $p(J_z)$ records where the scatterers sit, the growth of its scale how strongly they scatter. We fit this model to 7589 low-$\alpha$ red clump stars of Ting & Rix (2019) between 5 and 10 kpc and 2 and 8 Gyr old, leaving the heating history free. This yields $b=0.51^{+0.06}_{-0.07}$, consistent with the thin-layer prediction but not the volume-filling one. Comparing the 2-4 Gyr heating amplitude with the present molecular surface density gives an effective scatterer mass of $2.7\times10^{6}\,M_\odot$. Older stars have experienced more of the Galaxy's gas-richer past; correcting for that history brings all four age bins to $(1.9-2.8)\times10^{6}\,M_\odot$, inside the range cloud catalogues and mass functions give. The Milky Way's disc is heated near the plane, by an evolving population of objects of giant-molecular-cloud mass.
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Instrumentation and Methods for Astrophysics

Voltage-to-temperature calibration of the High Altitude THz Solar telescope acquisition system

Gedeane G.S. Kenshima, Daniel R. Sousa, Tiago Giorgetti et al. (+2 more)

The THz range has been under-explored for solar astronomy, mainly due to technological limitations. Only recently, a few new telescopes, such as the High Altitude Terahertz Solar (HATS) photometer, have been monitoring the solar activity in this range of the spectrum. This paper presents the experimental characterization and voltage-to-temperature calibration of the HATS acquisition system. HATS uses a Golay cell for capturing the incoming radiation, modulated by a 20 Hz fork chopper. The amplitude of the signal is then obtained at predetermined time intervals by applying a windowing function and an FFT to the signal. To characterize this acquisition system, a blackbody calibrator, with temperatures varying from 100 to 500 C (373.15 K to 648.15 K), was used as a THz source, and two signal recovery methodologies were compared: sinusoidal curve fitting and FFT combined with six windowing functions (rectangular, Hamming, Hann, Barlett, Blackman, and Flat Top). Our quantitative results demonstrate high linearity in the system's response over the input source's temperature range, with the Hamming window achieving the highest precision, yielding a Root Mean Square Error (RMSE) of 15.48 and a calibration temperature-to-voltage factor of 10.32 +- 0.13 mV/K. In contrast, the Bartlett window presented the highest error (RMSE 16.02). The choice of windowing function had only a minor effect on the calibration factors, which ranged from 10.32 to 10.43 mV/K, all within the experimental uncertainties. Beyond solar photometry, the signal modulation and windowing concepts established here are highly applicable to other fields requiring high-sensitivity thermal detection, such as industrial pyrometry for high-temperature manufacturing, environmental monitoring of atmospheric water vapor, and the development of medical imaging systems based on Terahertz radiation for non-invasive tissue analysis.
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All authors Gedeane G.S. Kenshima, Daniel R. Sousa, Tiago Giorgetti, Paulo J. A. Simões, C. Guillermo Giménez de Castro

Astrophysics of Galaxies

The effect of galaxy interactions on star formation rates in the COLIBRE simulations

Quinten W. E. van Zegveld, Evgenii Chaikin, Joop Schaye et al. (+8 more)

Observations and theory indicate that galaxy interactions enhance star formation rates (SFRs). However, the degree of enhancement and its dependence on the properties of the interacting galaxies vary across different studies. In this work, we use the COLIBRE simulations of galaxy formation to investigate the effect of interactions on the SFRs of star-forming galaxies at redshift $z\approx0$. The COLIBRE simulations capture the multiphase nature of the interstellar medium and have volumes up to $200^3$ and $400^3$ cMpc$^3$ at m6 (gas and dark-matter particle mass $\sim10^6~\mathrm{M_\odot}$) and m7 ($\sim10^7~\mathrm{M_\odot}$) resolutions, respectively. After constructing samples of interacting galaxies (with mass ratios $>0.1$) and isolated controls, matched in stellar mass, large- and small-scale environment, and redshift, we show that the average specific SFR (sSFR) of interacting galaxies is enhanced by up to a factor of $\approx2$ for separations of $\approx10$ kpc. The enhancement decreases with pair separation but remains significant out to $\approx200$ kpc. The enhancement increases with increasing numerical resolution, is more pronounced in the central regions of galaxies, and decreases with increasing stellar mass at fixed separation. Mergers with higher mass ratios induce stronger sSFR enhancement. We compare our results with observational data from the SDSS, finding good agreement in the dependence of the mean sSFR enhancement on separation, but underpredicting its normalisation by a factor of $\approx2$. Finally, we show that the pre-merger sSFR enhancement of resolved interactions accounts for $\approx2$ per cent of the $z\approx0$ cosmic SFR density.
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All authors Quinten W. E. van Zegveld, Evgenii Chaikin, Joop Schaye, David R. Patton, Sara L. Ellison, Alejandro Benítez-Llambay, Filip Huško, Robert J. McGibbon, Sylvia Ploeckinger, Alexander J. Richings, Matthieu Schaller

Cosmology and Nongalactic Astrophysics

CIBER $\times$ galaxy cross-correlations reveal a bright, low-redshift NIR background

Richard M. Feder, Grigory Heaton, James J. Bock et al. (+7 more)

We perform the first tomographic analysis of near-IR extragalactic background light (EBL) anisotropies, cross-correlating CIBER 1.1 and 1.8 $\mu$m imager data with photometric galaxy catalogs from DESI Legacy Survey DR8 and Hyper-Suprime-Cam Ultra-Deep Survey. We measure significantly higher cross-power than expectations from an integrated galaxy light (IGL) model on scales $\ell < 2000$, concentrated at low redshift ($z\lesssim 0.6$). Cluster member galaxies and associated structure account for 15-20% of the large-angle cross-power, indicating that group- and galaxy-scale halos contribute the bulk of the signal. Through a parametric halo model decomposition, we detect two-halo and one-halo clustering in cross-power at high significance, with amplitudes that decline smoothly across $z=0{-}1$. The inferred one-halo cross-power is of similar amplitude between DESI-LS and the deeper HSC catalog, implying a scenario in which low-redshift EBL fluctuations are amplified by contributions from lower-mass halos with satellites and/or diffuse intra-halo light (IHL). Converting our two-halo fits into estimates of $b_I \times dI/dz$, we find that standard IGL predictions underestimate our measurements, even when assuming an intensity bias as high as 3, similar to that of large SZ clusters, suggesting that a higher $dI/dz$ is required to reconcile observed discrepancies. Lastly, we find that correlated large-scale structure (LSS) at $z<1$ accounts for a substantial fraction of the CIBER auto-power reported in earlier work. These results identify low-redshift LSS as a significant and previously unappreciated contributor to near-IR EBL fluctuation measurements, setting the stage for cross-correlation science with CIBER-2, SPHEREx and a variety of LSS tracers.
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All authors Richard M. Feder, Grigory Heaton, James J. Bock, Yun-Ting Cheng, Yi-Kuan Chiang, Phillip M. Korngut, Shuji Matsuura, Jordan Mirocha, Kohji Tsumura, Michael Zemcov

Instrumentation and Methods for Astrophysics

Updates to WFC3/UVIS Encircled Energy Values in Select Filters

Anne O'Connor, Jennifer Mack and Varun Bajaj

We present updated encircled energy (EE) curves for a subset of UVIS filters. These are derived from a reanalysis of the drizzled Point Spread Function (PSF) data underlying the current EE calibration together with new measurements from deep observations of the PSF wings. Improved centroiding and analysis techniques applied to the drizzled PSFs produce more accurate EE values at small radii ($r \le 10$ pixels), bringing the results into closer agreement with a large archival PSF study (Huynh et al. 2025). At large radii, we leverage deep observations of the PSF wings in six filters and compare the fraction of light between 2" and 6" with predictions from an optical model of the PSF (Hartig 2009). For filters with pivot wavelengths $ \gtrsim{4000} \mathrm{\mathring{A}}$, the model agrees with the empirical data, but over-estimates the EE for UV filters by $\sim0.5$% at 2". The revised EE solutions affect the UVIS zeropoints, which are derived from aperture photometry in a 0.4" (10 pixel) radius and corrected to 6" using EE tables (Calamida et al. 2022). Overall, the impact is small; the EE at 0.4" is larger by $ \gtrsim{0.5}$ % (0.005 mag) for several filters (F218W, F225W, F275W, F775W, F814W, F845M), especially for UVIS2. In contrast, the EE value is generally smaller at 0.4" for long-pass filters (F200LP, F350LP, F850LP), with F850LP differing by $\sim2 $ % (0.02 mag). Updated EE tables will be delivered together with a revised set of UVIS inverse sensitivity tables and zeropoints later in 2026. In the interim, we provide EE tables for commonly used filters in Appendix A.
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High Energy Astrophysical Phenomena · Cross-listed from nucl-th

Transport properties in binary neutron star mergers: Effect of magnetic field

Pranjal Tambe and Debarati Chatterjee

In extreme environments such as binary neutron star mergers, temperatures as high as $50$ MeV and magnetic fields up to $10^{17}$ G, reach a regime where neutrino transport governs the macroscopic thermodynamic and chemical evolution. Existing merger simulations rely on zero magnetic field neutrino emissivity and opacity, potentially missing critical transport physics in highly magnetized neutron star cores. We present an exact framework for computing charged current Urca emissivity and neutrino opacity at finite temperature and magnetic field. We employ the Nucleon Width Approximation framework to account for the collisional broadening effects dominant in the high-density core. Our calculations demonstrate that extreme magnetic fields significantly enhance charged current neutrino opacity, effectively reducing the mean free path for thermal neutrinos.
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Cosmology and Nongalactic Astrophysics

MeerKAT Reveals Evidence of a Radio Megahalo at GHz Frequency

Swarna Chatterjee and Kenda Knowles

Radio megahalos are recently discovered large-scale diffuse synchrotron sources identified through LOFAR observations. We present MeerKAT L-band observations of the massive galaxy cluster RXC~J0528.9$-$3927, that reveals faint emission surrounding its central radio halo. At 1.28 GHz, the known $\sim1.14$ Mpc halo is embedded within previously unreported low-surface-brightness emission extending to $\sim2$ Mpc. The surface-brightness profile of the emission shows a distinct flattening beyond $\sim0.55R_{500}$, suggesting that the outer emission forms an additional component. These properties make the cluster a candidate megahalo system and potentially the first detected at GHz frequencies, although deeper multi-frequency observations are required for confirmation.
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Instrumentation and Methods for Astrophysics

Automation and Modernisation of Legacy BiSON Solar Observatories with the BiSON:NG Platform

S. J. Hale, E.Murray, W. J. Chaplin et al. (+4 more)

The Birmingham Solar Oscillations Network (BiSON) provides long-term, high-precision Sun-as-a-star radial-velocity observations for helioseismology. While most BiSON sites operate autonomously, two observatories at Observatorio del Teide, Tenerife, and at Mount Wilson Observatory, USA, have historically required daily on-site operation. We present the automation of these sites using the BiSON:NG next-generation observing platform, incorporating compact fibre-fed instrumentation and a modular, microservice-based control and data acquisition architecture. At both locations, new automated optical feeds and a common software framework have been deployed, enabling autonomous operation of the observing subsystems, including guiding, data acquisition, and instrument control, despite markedly different physical and operational constraints. The upgrades demonstrate that modern automation can be successfully integrated within existing and historic observatory infrastructure. Adoption of the BiSON:NG architecture reduces operational overhead, mitigates risks associated with hardware and software obsolescence, and supports sustainable operation of the network over the multi-decade timescales required for helioseismic studies. The flexibility of the architecture also provides a pathway for future deployment of additional small-footprint observatories.
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All authors S. J. Hale, E.Murray, W. J. Chaplin, Y. P. Elsworth, R. Howe, P. L. Pallé, E. J. Rhodes Jr

Astrophysics of Galaxies

Search for a Globular Cluster whose Passage through the Galactic Disk could Trigger the Radcliffe Wave

V. V. Bobylev and A. T. Bajkova

Using a catalog of 152 globular clusters (GCs), their orbits were constructed to determine their intersections with the Galaxy's plane of symmetry. Young open star clusters (OSCs) were selected from the selection zone characteristic of the Radcliffe wave. The Hunt and Reffert catalog served as the source of data on these OSCs. A grouping of 17 OSCs with an average age of 32.7 million years was found. It is compact in coordinate, velocity, and age space. This grouping is shown to be a good candidate for the hypothesis that the Radcliffe wave is generated by the passage of an impactor through the Galaxy's plane of symmetry, with the impactor being the GC NGC~4372. The last time it crossed the galactic plane was 55.5 million years ago, and 22.2 million years later, a burst of star formation occurred at this location, forming a whole group of open-clustered stars, and possibly the Radcliffe wave as a whole.
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