Astrophysics of Galaxies
Jaden S. Sidhu, Sanaea C. Rose and Frederic A. Rasio
Nuclear star clusters (NSCs) surrounding supermassive black holes (SMBHs) are among the densest
stellar environments in the universe. In these environments, collisions can shape the
stellar mass function and produce exotic
stellar populations. In this work, we investigate how
stellar collisions couple with
stellar evolution in the inner parsec of an NSC. We simulate the
evolution of a sample of $1000$ $1$ $M_\odot$
stars embedded in a uniform cluster of dynamically relaxed 0.5 $M_\odot$
stars. Using
COSMIC to evolve
stellar properties in time , we track the mass, radius, and evolutionary state of the
stars as they collide in the cluster. Our results show that most
stars within $0.1$~pc of the SMBH experience a collision while on the main-sequence. However, outside of this distance,
stars collide during the red
giant phase, when the
stellar radius increases dramatically. We find that the most common type of collision – main-sequence or red
giant – over the lifetime of the cluster depends on the steepness of the
stellar cusp, which determines the spatial distribution of the
stars in the cluster. These results show that
stellar evolution plays a fundamental role in shaping the collisional history of
stars in
nuclear star clusters. Lastly, we consider whether the closest known
stars to the Milky Way's SMBH have experienced a collision. We estimate that several of the S-
stars have a high probability of experiencing a collision over their main-sequence lifetime, perhaps with implications for their observed youth and properties.
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Cosmology and Nongalactic Astrophysics
Insights for Early Dark Energy with Big Bang Nucleosynthesis
Christopher Cook and Joel Meyers
Big Bang Nucleosynthesis (BBN), as one of the earliest processes in the universe accessible to direct observation, offers a powerful and independent probe of the
cosmic expansion history. With recent advances in both theory and observation, including efficient and flexible BBN codes, percent-level measurements of
primordial deuterium and helium-4 abundances, refined measurements of
nuclear reaction rates, and precise determinations of the
baryon density from the
cosmic microwave background, particularly keen insights can be gained from BBN. In this work, we leverage these developments to place model-independent constraints on deviations from the Standard Model expansion history during BBN. Using the latest abundance data, we apply principal component analysis to identify the most constrained and physically meaningful modes of expansion history variation. This approach allows us to impose the most general constraints on early dark energy during the epoch of BBN. We further examine whether general modifications to the expansion rate could alleviate the long-standing lithium problem. Our results demonstrate that BBN, sharpened by modern data and statistical techniques, remains an indispensable probe of dark energy and new physics in the early universe.
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Instrumentation and Methods for Astrophysics
Classifying High-Energy Celestial Objects with Machine Learning Methods
Alexis Mathis, Daniel Yu, Nolan Faught et al. (+1 more)
Machine learning is a field that has been growing in importance since the early 2010s due to the increasing accuracy of classification models and hardware advances that have enabled faster training on large
datasets. In the field of astronomy, tree-based models and simple neural networks have recently garnered
attention as a means of classifying celestial objects based on photometric data. We apply common tree-based models to assess performance of these models for discriminating objects with similar photometric signals,
pulsars and black holes. We also train a RNN on a downsampled and normalized version of the raw signal data to examine its potential as a model capable of object discrimination and classification in real-time.
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All authors Alexis Mathis, Daniel Yu, Nolan Faught, Tyrian Hobbs.
Solar and Stellar Astrophysics
The magnetic origin of the outer boundaries of sunspots
Markus Schmassmann, Nazaret Bello González, Jan Jurčák et al. (+1 more)
Context. Sunspot boundaries are commonly outlined by contours of the continuum intensity. However, their
magnetic nature has not yet been fully characterised. Aims. We investigate the properties of the outer boundary of a long-lived sunspot to identify the
magnetic property that defines it. Methods. We analysed the
magnetic properties of AR NOAA11591 spot during its two passages across the
solar disc, using SDO/HMI continuum intensity and
magnetic field, and determined their contours to outline the outer boundary. Results. During the 1st disc passage, in which the sunspot is in its stable phase, the intensity contours at 0.9 of the mean quiet Sun intensity and isocontours of the
magnetic field strength of 625G provide an almost perfect match between the two contours. With these thresholds, the time-averaged area of mismatch is minimised, yielding an average distance between the contours of 0.58 pixel, corresponding to less than 0.26 arcsec. During the 2nd disc passage, the spot shows clear signs of decay, and we find that the 0.9 intensity and 625G
magnetic isocontours detach from each other, coupled to the disappearance of penumbra. In this super-equipartition area, granulation still operates. Conclusions. Based on a comparison with simulation data from our previous work, and in agreement with findings of other authors, we conclude that the outer boundary of stable sunspots is defined by an invariant
magnetic field: the equipartition field. From the discrepancy between intensity and
magnetic contours during the decaying phase of the sunspot, we surmise that alongside the well-established (magneto-)convective regimes of the photosphere - granular, penumbral, and umbral - a super-equipartition granular regime can be identified. In this regime, bright, but smaller granules occur where the
magnetic field exceeds equipartition but remains sub-critical for convection suppression.
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All authors Markus Schmassmann, Nazaret Bello González, Jan Jurčák, Rolf Schlichenmaier
Instrumentation and Methods for Astrophysics
Asteroid Occultations with VERITAS: Observations and Considerations
Joshua Bartkoske, Anne Duerr and Dave Kieda
Occultations, the covering up of one celestial body by another celestial body, have been used in astronomy for millennia to learn about the sun and moon. Since 2018, VERITAS has implemented a program to detect predicted asteroid occultations, where an asteroid covers up a
star. VERITAS has attempted to observe over 100 occultations to date and successfully observed 20 occultations. With these occultations, VERITAS can directly measure the smallest angular diameters of any instrument or technique in the optical for
stars between magnitude 9 and 13. Each angular diameter is measured by fitting the diffraction pattern observed by the central VERITAS pixel at the start and end of an occultation. Once a planned FADC upgrade is complete, VERITAS will begin a program to search for serendipitous occultations within its full field of view (3 deg). Serendipitous occultations of sub-km trans-Neptunian objects (TNOs) have the potential to constrain models of
solar system formation. This work details how VERITAS predicts and observes occultations as well as the overall status of the asteroid occultation program and future steps for observing occultations of both asteroids and TNOs.
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Instrumentation and Methods for Astrophysics
libyt: an In Situ Interface Connecting Simulations with yt, Python, and Jupyter Workflows
Shin-Rong Tsai, Hsi-Yu Schive and Matthew J. Turk
In the exascale computing era, handling and analyzing massive
datasets have become extremely challenging. In situ analysis, which processes data during simulation runtime and bypasses costly intermediate disk input and output steps, offers a promising solution. We present libyt (https://github.com/yt-project/libyt), an open-source C library that enables astrophysical simulations to analyze and visualize data in parallel computation with yt or other Python packages. libyt can invoke Python routines automatically or provide interactive entry points via a Python
prompt or a Jupyter Notebook. It requires minimal intervention in researchers' workflow, allowing users to reuse job submission scripts and Python routines. We describe libyt's architecture for parallel computing in high-performance computing environments, including its bidirectional connection between simulation codes and Python, and its integration into the Jupyter ecosystem. We detail its methods for reading patch-based adaptive mesh refinement (AMR) simulations and handling in-
memory data with minimal overhead, and procedures for yielding data when requested by Python. We describe how libyt maps simulation data to yt frontends, allowing post-processing scripts to be converted into in situ analysis with just two lines of change. We document libyt's API and demonstrate its integration into two astrophysical simulation codes, GAMER and Enzo, using examples including core-collapse
supernovae, isolated
dwarf galaxies, fuzzy dark matter, the Sod shock tube test, Kelvin-Helmholtz instability, and the AGORA
galaxy simulation. Finally, we discuss libyt's performance, limitations related to data redistribution, extensibility, architecture, and comparisons with traditional post-processing approaches.
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High Energy Astrophysical Phenomena
Constraints on the intergalactic magnetic field from Fermi-LAT observations of GRB 221009A
Lea Burmeister, Paolo Da Vela, Francesco Longo et al. (+5 more)
A cosmological origin of the
magnetic fields in large scale structures of the Universe would require a non-negligible
magnetic field in
cosmic voids, which, however, remains undetected. Gamma-ray emission from gamma-ray bursts (GRBs) offers the opportunity to indirectly probe such an intergalactic
magnetic field (IGMF), as gamma rays interact with
cosmic radiation fields, producing electron-positron pairs, and initiate an electromagnetic cascade. The deflection of the pairs in the IGMF results in a time-delayed signal at GeV energies. Using observations with the
Fermi Large Area
Telescope of the GRB 221009A, we are able to derive the most stringent constraints to date from the non-observation of the cascade and rule out
magnetic fields B < 2.5 x 10^{-17} G at 95% confidence level for a coherence length larger than 1 Mpc. Our results are comparable to limits obtained from blazar observations but do not suffer from assumptions on the duty cycle of the gamma-ray source or whether inverse-Compton scattering losses dominate over the development of
plasma instabilities.
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All authors Lea Burmeister, Paolo Da Vela, Francesco Longo, Guillem Marti-Devesa, Manuel Meyer, Francesco Saturni, Antonio Stamerra, Peter Veres
Solar and Stellar Astrophysics
First Detection of an Ultracool Dwarf at 340 MHz: VLITE Observations of EI Cancri AB
Michele L. Silverstein, Tracy E. Clarke, Wendy M. Peters et al. (+3 more)
Magnetically driven phenomena such as flaring events and aurorae lead ultracool
dwarfs to emit at
radio frequencies. Despite decades of scrutiny, a comprehensive physical understanding of their
radio emission at different frequencies remains elusive, spurring on additional study of these complex objects. The VLA Low-band Ionosphere and Transient Experiment (VLITE) is a commensal instrument operating at 340 MHz on the Very Large Array. A key advantage of 340 MHz observations is their sensitivity to circumstellar disks and
planets at understudied distances from the
stellar disk, intermediate between GHz and low MHz sensitivities. Hard-to-find coronal mass ejections are also predicted to be detectable at 340 MHz. However, this frequency regime is relatively unprobed in ultracool
dwarf studies, with few searches and no published detections to date. Here we highlight our investigation of the nearby M7-M7 binary, EI Cancri. EI Cancri AB is magnetically active, yet has an uncharacteristically long 83-day candidate rotation period within the system. With the VLITE detection of the EI Cancri system, we present the first ever detection of ultracool
dwarf emission at 340 MHz.
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All authors Michele L. Silverstein, Tracy E. Clarke, Wendy M. Peters, Emil Polisensky, Jackie Villadsen, Jordan M. Stone
Solar and Stellar Astrophysics
The Crab Nebula Revisited Using HST/WFC3
William P. Blair, Ravi Sankrit, Dan Milisavljevic et al. (+5 more)
It has been over 24 years since the iconic Crab Nebula has been visited by the high spatial resolution eye of the Hubble Space
Telescope. The expanding nebula is dynamic on these timescales, with many of the outer filaments of the nebula known to show proper motions of 0.3” or more per year. Over time, it has become increasingly difficult to compare the fine scale structure of the nebula with recent data at other wavelengths. We have re-observed the Crab in an HST Cycle 31 program using the WFC3 camera and filters similar to those previously used to make the existing mosaic that dates from 1999-2000 and was obtained with the WFPC2 camera. Two central fields were observed with the F487N filter, providing an uncontaminated hydrogen band for comparison. We also observed two primarily continuum band filters (F547M and F763M), allowing us to study the optical synchrotron nebula component of the Crab's emission. We compare these new data to the first epoch of WFPC2 data as well as to more contemporaneous NIR/MIR imagery from JWST. Finally, we highlight two previously unrecognized groupings of filaments with similar emission characteristics that are nearly diametrically opposed from the
pulsar but whose origin remains uncertain.
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All authors William P. Blair, Ravi Sankrit, Dan Milisavljevic, Tea Temim, J. Martin Laming, Patrick Slane, Ziwei Ding, Thomas Martin
Astrophysics of Galaxies
Connection Between Dwarf Galaxies and Globular Clusters: Insights from the Perseus Cluster Using Subaru Imaging and Keck Spectroscopy
Yimeng Tang, Aaron J. Romanowsky, Song Huang et al. (+11 more)
We present a systematic study of 189
dwarf galaxies and their globular cluster (GC) systems in the Perseus cluster, based on deep Subaru Hyper Suprime-Cam imaging and Keck spectroscopy, supplemented by literature data. This constitutes the largest sample of
dwarfs in a single
galaxy cluster to date with simultaneous deep imaging, spectroscopic coverage, and GC measurements, while uniquely spanning a broad and continuous range of
galaxy properties. We find an anti-correlation between GC specific mass and
galaxy stellar mass for
dwarfs in Perseus similar to observations in other clusters. At fixed
stellar mass,
dwarfs with lower surface brightness or larger effective radius tend to be more GC-rich – suggesting either high GC formation efficiency in an earlier compact-
galaxy phase, or less efficient GC disruption. The correlation between GC richness and axis ratio in Perseus is weaker than in other environments. We find some connection between GC richness and infall time, but not with the clear correlations found in Virgo, Coma, and cosmological simulations. More complete observations are needed to test for cluster-to-cluster variations in
galaxy and GC evolutionary histories. This work demonstrates the potential of new wide-field imaging and spectroscopy surveys for understanding GCs and
dwarf galaxies, and highlights the need for further work in theoretical modeling.
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All authors Yimeng Tang, Aaron J. Romanowsky, Song Huang, Nobuhiro Okabe, Jean P. Brodie, Kevin A. Bundy, Maria Luisa Buzzo, Timothy Carleton, Anna Ferré-Mateu, Duncan A. Forbes, Jonah S. Gannon, Steven R. Janssens, Arsen Levitskiy, Alexi M. Musick
Earth and Planetary Astrophysics
An Open Benchmark of One Million High-Fidelity Cislunar Trajectories
Travis Yeager, Denvir Higgins, Peter Mcgill et al. (+4 more)
Cislunar space spans from geosynchronous altitudes to beyond the Moon and will underpin future exploration, science, and security operations. We describe and release an open
dataset of one million numerically propagated cislunar trajectories generated with the open-source Space Situational Awareness Python package (SSAPy). The model includes high-degree Earth/Moon
gravity,
solar gravity, and Earth/Sun radiation pressure; other planetary gravities are omitted by design for computational efficiency. Initial conditions uniformly sample commonly used osculating-element ranges, and each trajectory is propagated for up to six years under a single, fixed start epoch. The
dataset is intended as a reusable
benchmark for method development (e.g., space domain awareness,
navigation, and machine learning pipelines), a reference library for statistical studies of orbit families, and a starting point for community-driven extensions (e.g., alternative epochs). We report empirically observed stability trends (e.g., a band near 5 GEO and persistence of some co-orbital classes including L4/L5 librators) as
dataset descriptors rather than new dynamical results. The chief contribution is the scale, fidelity, organization (CSV/HDF5 with full state time series and metadata), and open availability, which together lower the barrier to comparative and data-driven studies in the cislunar regime.
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All authors Travis Yeager, Denvir Higgins, Peter Mcgill, Kerianne Pruett, Alexx Perloff, Tara Grice, Michael Schneider
Astrophysics of Galaxies
Effects of Varied Cosmic Ray Feedback from AGN on Massive Galaxy Properties
Charvi Goyal, Sam B. Ponnada, Philip F. Hopkins et al. (+3 more)
Active
galactic nuclei (AGN) provide energetic feedback necessary to `turn off'
star formation in high-mass
galaxies (M$_{\rm halo} \geq $ 10$^{12.5}$ M$_{\odot}$, $10.4 \leq \log(\frac{M_*}{M_\odot}) \leq 11$) as observed.
Cosmic rays (CRs) have been proposed as a promising channel of AGN feedback, but the nature of CR feedback from AGN remains uncertain. We analyze a set of high-resolution simulations of massive
galaxies from the Feedback in Realistic Environments (FIRE-3) project including multi-channel AGN feedback, explicitly evolving kinetic/mechanical, radiative, and spectrally-resolved CRs from the central black hole. Specifically, we explore different CR feedback and transport assumptions, calibrated to Milky Way local ISM constraints, and compare them to observed
galaxy scaling relations. We find that all parameterizations explored self-regulate within agreement with observed
galaxy scaling relations, demonstrating that CR injection efficiencies varied by $\sim$1.5 dex and locally-variable transport produce quenched
galaxies with reasonable bulk properties; however, they feature orders-of-magnitude variant circumgalactic medium (CGM) gas properties. Our results indicate that multi-wavelength synthetic observations probing these varied
halo properties from larger simulated samples in conjunction with observational comparisons may place novel constraints on how AGN physically quench
star formation in massive
galaxies.
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All authors Charvi Goyal, Sam B. Ponnada, Philip F. Hopkins, Sarah Wellons, Jose A. Benavides, Kung-Yi Su
Astrophysics of Galaxies
Milky Way Globular Clusters: Nurseries for Dynamically-Formed Binary Black Holes
Federico Angeloni, Konstantinos Kritos, Raffaella Schneider et al. (+4 more)
We present a novel self-consistent theoretical framework to characterize the formation,
evolution, and merger sites of dynamically-formed black hole binaries, with a focus on explaining the most massive events observed by the LIGO-Virgo-KAGRA Collaboration. Our approach couples the
galaxy formation model GAMESH with cluster population synthesis codes to trace the
cosmic evolution of globular clusters simultaneously with mergers of massive black holes. Our reference model, which includes prescriptions for both cluster formation and disruption depending on properties of specific
galaxies, accurately reproduces the observed age-mass distribution of the Milky Way globular clusters. We find that approximately 30% of the globular clusters observed in our
galaxy's
halo may have originated from satellite
galaxies of the Milky Way. We confirm that hierarchical black hole mergers provide a significant contribution to the formation of black holes in and above the pair-instability mass gap. However, quantifying their contribution is challenging, as different population synthesis codes yield divergent results in terms of black hole mass function and merger rates. Furthermore, we characterize the host
galaxies where massive black holes form in terms of their dark matter,
stellar mass, and
metallicity. Ultimately, we demonstrate that the merger and birth rate densities of binary black holes increase with
redshift till z = 5. This
cosmic evolution is a crucial signature with significant implications for future detectors like the LISA, the Einstein
Telescope and
Cosmic Explorer, which will be capable to probe the high-
redshift Universe.
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All authors Federico Angeloni, Konstantinos Kritos, Raffaella Schneider, Emanuele Berti, Luca Graziani, Stefano Torniamenti, Michela Mapelli
High Energy Astrophysical Phenomena
Globular Clusters GMRT Pulsar Search (GCGPS) II: Discovery of five MSPs in M69 and M70
Jyotirmoy Das, Jayanta Roy, Paulo C. C. Freire et al. (+6 more)
This paper reports recent discoveries from the Globular Clusters GMRT
Pulsar Search (GCGPS) survey, which aims to uncover
pulsars in the globular clusters (GCs) of the Milky Way using the upgraded
Giant Metrewave
Radio Telescope (uGMRT). Utilising the Band-4 (550$-$750 MHz) and Band-3 (300$-$500 MHz) receivers, the survey targets GCs accessible to uGMRT ($-53^\circ\,<\,\delta\,<\,-17^\circ$), excluding the declination range that can be covered by the Five-hundred-meter Aperture Spherical
radio Telescope (FAST). The survey focuses on GCs that have not previously been searched with comparable sensitivity in these
radio frequencies. In this paper, we present the discovery of the five MSPs in two GCs, $-$ NGC~6637 (M69) and NGC~6681 (M70), each hosting MSPs identified here for the first time. Observations of M69 led to the discovery of two MSPs: J1831$-$3220A (M69A) and J1831$-$3220B (M69B), both of which we localize with arcsecond precision using interferometric imaging. Observations of M70 resulted in three new MSPs: J1843$-$3217A (M70A), J1843$-$3217B (M70B), and J1843$-$3217C (M70C). Although direct imaging did not yield precise localizations for these MSPs, we provide initial estimates based on uGMRT beam forming and imaging analysis. Additionally, we present preliminary imaging results for other observed GCs, and in cases of non-detections, we report upper limits on pulsed emission based on the rms noise levels in the image plane.
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All authors Jyotirmoy Das, Jayanta Roy, Paulo C. C. Freire, Scott M Ransom, Bhaswati Bhattacharyya, Karel Adámek, Wes Armour, Sanjay Kudale, Mekhala V. Muley
Astrophysics of Galaxies
Balmer Transition Signatures from Gas-Enshrouded, Dust-Poor Active Galactic Nuclei
Zu Yan, Kohei Inayoshi, Kejian Chen et al. (+1 more)
Little red dots (LRDs), a population of active
galactic nuclei (AGNs) recently discovered by JWST, show distinctive Balmer-transition features, including prominent Balmer absorption, pronounced Balmer breaks, and large equivalent widths of broad $\mathrm{H}\alpha$ emission, all of which indicate the presence of dense gas surrounding their central black holes. A further key property of LRDs is their large Balmer decrements with broad $\mathrm{H}\alpha/\mathrm{H}\beta$ line-flux ratios far exceeding the Case B recombination value. These ratios of $\mathrm{H}\alpha/\mathrm{H}\beta>3$ have often been interpreted as evidence for heavy
dust extinction ($A_V\gtrsim 3$ mag), however such
dust would inevitably produce strong near-to-mid infrared re-emission that is hardly seen in JWST/MIRI observations. To investigate the physical origin of these observed Balmer features, we perform radiation transfer calculations through
dust-free, dense gas. We show that the observed large Balmer decrements ($\mathrm{H}\alpha/\mathrm{H}\beta$ and $\mathrm{H}\alpha/\mathrm{H}\gamma$) naturally arise from Balmer resonance scattering without invoking
dust. At sufficiently high densities ($n_\mathrm{H} \gtrsim 10^{{8}-{10}}~\mathrm{cm^{-3}}$), the elevated multiple Balmer-line ratios converge to values that closely mimic
dust reddening, explaining why LRD spectra resemble obscured AGNs. Furthermore, when the Balmer break and broad Balmer lines originate in the same dense gas, their strengths are physically linked, allowing us to constrain the density structure and infer a low broad-line region gas mass of $\sim O(10~M_\odot)$. Such a small gas reservoir would be enriched by even a single
supernova, implying that LRDs with observed low-
metallicity signatures likely experienced minimal
star formation in their
nuclei.
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All authors Zu Yan, Kohei Inayoshi, Kejian Chen, Jingsong Guo
Astrophysics of Galaxies
Dynamical constraints on the S2 (S0-2) star possible companions
Rodrigo P. Silva, Alexandre C. M. Correia, Tjarda C. N. Boekholt et al. (+1 more)
The center of the
Galaxy harbors a supermassive black hole, Sgr\,A*, which is surrounded by a massive
star cluster known as the S-cluster. The most extensively studied
star in this cluster is the B-type main-sequence S2
star (also known as S0-2). These types of
stars are commonly found in binary systems in the
Galactic field, but observations do not seem to detect a companion to S2. This absence may be attributed to observational biases or to a dynamically hostile environment caused by phenomena such as
tidal disruption or mergers. Using a $N$-body code with first-order post-Newtonian corrections, we investigate whether S2 can host a
stellar or planetary companion. We perform $10^{5}$ simulations adopting uniform distributions for the orbital elements of the companion. Our results show that companions may exist for orbital periods shorter than 100~days, eccentricities below 0.8, and across the full range of mutual inclinations. The number of surviving companions increases with shorter orbital periods, lower eccentricities, and nearly coplanar orbits. We also find that the disruption mechanisms include mergers driven by Lidov-Kozai cycles and breakups that occur when the companion surpasses the Hill radius of its orbit. Finally, we find that the presence of a companion would alter S2's astrometric signal by no more than $ 5\,\mu{\rm as}$. Current radial-velocity detection limits constrain viable
stellar binary configurations to approximately 4.4% of the simulated cases. Including astrometric limits reduces to 4.3%. Imposing an additional constraint that any companion must have a mass $\lesssim 2\,M_{\odot}$ (otherwise it would be visible) narrows the fraction of undetectable
stellar binaries to just 3.0%.
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All authors Rodrigo P. Silva, Alexandre C. M. Correia, Tjarda C. N. Boekholt, Paulo J. V. Garcia
Solar and Stellar Astrophysics
Seeking Spectroscopic Binaries with Data-Driven Models
Isabel Angelo, Erik Petigura and Megan Bedell
Data-driven
stellar classification has a long and important history in astronomy, dating as far back as Annie Jump Cannon's "by eye" classifications of
stars into spectral types still used today. In recent years, data-driven spectroscopy has proven to be an effective means of deriving
stellar properties for large samples of
stars, sidestepping issues with computational efficiency, incomplete line lists, and radiative transfer calculations associated with physical
stellar models. A logical application of these
algorithms is the detection of unresolved
stellar binaries, which requires accurate spectroscopic models to resolve flux contributions from a fainter secondary
star in the spectrum. Here we use The Cannon to train a data-driven model on spectra from the Keck High Resolution Echelle Spectrometer. We show that our model is competitive with existing data-driven models in its ability to predict
stellar properties Teff,
stellar radius, [Fe/H], vsin(i), and instrumental PSF, particularly when we apply a novel wavelet-based processing step to spectra before training. We find that even with accurate estimates of
star properties, our model's ability to detect unresolved binaries is limited by its approx. 3% accuracy in per-pixel flux predictions, illuminating possible limitations of data-driven model applications.
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Astrophysics of Galaxies
MIRACLE III. JWST/MIRI expose the hidden role of the AGN outflow in NGC 1068
C. Marconcini, A. Marconi, M. Ceci et al. (+27 more)
We present new JWST IFS observations of the active
galaxy NGC 1068, combining Mid-IR and optical IFS data from MIRI and MUSE to characterize the multi-phase circumnuclear gas properties and its interaction with the AGN
outflow and
radio jet. MIRI data trace the multiphase gas emission up to 400 pc from the
nucleus at 20–60 pc resolution, unveiling a clumpy ionized structure around the
radio hot-spots and a rotating warm molecular disc. Innovative Mid-IR diagnostic diagrams highlight the role of the AGN as the main excitation source for the ionized gas in the entire MIRI field of view, consistent with optical diagnostics, and supporting the AGN-driven wind scenario. Density sensitive [NeV] and [ArV] Mid-IR transitions reveal high-density clumps (n_e > 10**4 cm**-3) along the edges of the jet and
outflow, tracing gas compression by the expanding wind. We combined multi-cloud kinematic (MOKA) and photo-ionization (HOMERUN) modeling to characterize the ionized
outflow properties and found that [OIV] traces an
outflow 300 km/s faster than that inferred from [OIII], showing that the two lines originate from distinct gas components. This kinematic dichotomy is confirmed by the photoionization analysis, which requires a
dust-poor component dominating the optical lines and a
dust-rich component responsible for the Mid-IR emission. The Mid-IR-revealed dusty component carries a significantly larger ionized-gas mass than what can be inferred from optical lines alone, showing that most of the outflowing mass is hidden from classical optical diagnostics. Our modelling point to a two-stage acceleration scenario, with velocities up to ~2000 km/s, consistent with an energy-driven wind. Our findings indicates that the
outflow entrains up to a few 10**6
solar masses of ionized gas and couples efficiently with the surrounding ISM, injecting
turbulence and impacting the host-
galaxy environment.
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All authors C. Marconcini, A. Marconi, M. Ceci, A. Feltre, M. Tartenas, K. Zubovas, I. Lamperti, G. Cresci, L. Ulivi, F. Mannucci, E. Bertola, C. Bracci, E. Cataldi, Q. D'Amato, J.A. Fernandez-Ontiveros, J. Fritz, E. Hatziminaoglou, I. E. Lopez, M. Ginolfi, C. Gruppioni, M. Mingozzi, B. Moreschini, G. Sabatini, F. Salvestrini, M. Scialpi, G. Tozzi, A. Vidal-Garcia, C. Vignali, G. Venturi, M.V. Zanchettin
Cosmology and Nongalactic Astrophysics
KiDS-Legacy: Constraining dark energy, neutrino mass, and curvature
Robert Reischke, Benjamin Stölzner, Benjamin Joachimi et al. (+25 more)
We constrained minimally extended cosmological models with the
cosmic shear analysis of the final data release from the Kilo-Degree Survey (KiDS-Legacy) in combination with external probes. Due to the consistency of the KiDS-Legacy analysis with the
cosmic microwave background (CMB), we could combine these
datasets reliably for the first time. Additionally, we used CMB
lensing,
galaxy redshift-space distortions, and
baryon acoustic oscillations. We assessed, in turn, the effects of spatial
curvature, varying
neutrino masses, and an evolving dark energy component on cosmological constraints from KiDS-Legacy alone and from KiDS-Legacy combined with external probes. We find KiDS-Legacy to be consistent with the fiducial flat $\Lambda$-cold dark matter ($\Lambda$CDM) analysis with $c^2 \sum m_\nu\leq 1.5\,$eV, $w_0 = -1.0\pm 0.7$, and $w_a = -1.3^{+1.9}_{-2.0}$ while $\Omega_K = 0.08^{+0.16}_{-0.17}$ (1$\sigma$ bounds) with an almost equal goodness of fit. The $w_0w_a$CDM model is not a significant improvement over $\Lambda$CDM when
cosmic shear and CMB
lensing are combined, yielding a Bayes factor $B = 0.07$. If all probes are combined, however, $B$ increases to 2.73, corresponding to a $2.6\sigma$ suspiciousness tension. The constraint on $S_8 = \sigma_8\sqrt{\Omega_\mathrm{m}/0.3}$ is robust to opening up the parameter space for
cosmic shear. Adding all external
datasets to KiDS-Legacy, we find $S_8 = 0.816 \pm 0.006$ in $\Lambda$CDM and $S_8 = 0.837 \pm 0.008$ in $w_0 w_a$CDM for all probes combined.
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All authors Robert Reischke, Benjamin Stölzner, Benjamin Joachimi, Angus H. Wright, Marika Asgari, Maciej Bilicki, Nora Elisa Chisari, Andrej Dvornik, Christos Georgiou, Benjamin Giblin, Joachim Harnois-Déraps, Catherine Heymans, Hendrik Hildebrandt, Henk Hoekstra, Shahab Joudaki, Konrad Kuijken, Shun-Sheng Li, Laila Linke, Arthur Loureiro, Constance Mahony, Lauro Moscardini, Lucas Porth, Mario Radovich, Tilman Tröster, Maximilian von Wietersheim-Kramsta, Ziang Yan, Mijin Yoon, Yun-Hao Zhang
Cosmology and Nongalactic Astrophysics
KiDS-Legacy: Constraints on Horndeski gravity from weak lensing combined with galaxy clustering and cosmic microwave background anisotropies
Benjamin Stölzner, Robert Reischke, Matteo Grasso et al. (+25 more)
We present constraints on modified
gravity from a
cosmic shear analysis of the final data release of the Kilo-Degree Survey (KiDS-Legacy) in combination with DESI measurements of
baryon acoustic oscillations, eBOSS observations of
redshift space distortions, and
cosmic microwave background anisotropies from Planck. We study the Horndeski class of modified
gravity models in an effective field theory framework employing a parameterisation that satisfies stability conditions by construction and, for the first time, present a cosmological analysis in this inherently stable parameter basis.
Cosmic shear constrains the Horndeski parameter space significantly, matching or surpassing the CMB contribution. Adopting the de-mixed kinetic term of the scalar field perturbation, $D_{\rm kin}$, and the deviation of the Planck mass from its fiducial value, $\Delta M_*^2\equiv M_*^2-1$, as model parameters, we constrain their present values to be $\Delta \hat{M}_*^2=0.32^{+0.07}_{-0.21}$ and $\hat{D}_{\rm kin} = 3.74^{+0.69}_{-1.92}$, which deviate from general relativity at $1.5\sigma$ and $1.9\sigma$, respectively. We derive constraints on the structure growth parameter $S_8=0.813^{+0.008}_{-0.011}$, which is compatible with the $\Lambda$CDM constraint at $0.54\sigma$. We obtain the deviation of the effective Newtonian coupling from the GR value as $\Delta \mu_{\infty,{\rm eff}}=0.066\pm0.023$, corresponding to a $2.9\sigma$ significance. Although modified
gravity provides a slightly better fit to the data, a model comparison shows only a weak preference for modified
gravity at the $1.4\sigma$ level. When adopting a dynamical dark energy model of the background cosmology, the inferred modified
gravity parameter constraints are stable with respect to a $\Lambda$CDM background, while a mild preference at $1.57\sigma$ for dynamical dark energy remains.
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All authors Benjamin Stölzner, Robert Reischke, Matteo Grasso, Matteo Cataneo, Benjamin Joachimi, Arthur Loureiro, Alessio Spurio Mancini, Angus H. Wright, Marika Asgari, Maciej Bilicki, Andrej Dvornik, Christos Georgiou, Benjamin Giblin, Catherine Heymans, Hendrik Hildebrandt, Shahab Joudaki, Konrad Kuijken, Shun-Sheng Li, Laila Linke, Constance Mahony, Lauro Moscardini, Lucas Porth, Mario Radovich, Tilman Tröster, Maximilian von Wietersheim-Kramsta, Ziang Yan, Mijin Yoon, Yun-Hao Zhang
Astrophysics of Galaxies
Intermediate Mass Black Hole Binary Evolution in Nuclear Star Clusters: the effect of the stellar mass black hole population
Fazeel Mahmood Khan, Peter Berczik, Margarita Sobolenko et al. (+4 more)
In this study, we investigate the dynamics of Intermediate-Mass Black Hole (IMBH) binaries within
Nuclear Star Clusters (NSCs) that contain a population of
stellar-mass black holes (BHs). We examine how these
stellar and BH populations influence the dynamics of the IMBH binary and, in turn, how the evolving IMBH binary affects the surrounding
stellar and BH populations. We conduct high-resolution $N$-body simulations of NSCs constructed based on observational parameters from two local
dwarf galaxies: NGC205 and NGC404. For the first time, we achieve a
star particle mass resolution of $1\rm\;M_{\odot}$ and a BH mass resolution of $10\rm\;M_{\odot}$. This level of resolution is crucial for accurately modeling the collisional dynamics of these dense systems. Including
stellar-mass BHs within the
stellar population significantly influences the IMBH binary dynamics, nearly doubling the sinking rate and halving the merger time. During the initial phase of the inspiral, the IMBH binary disrupts both the
stellar and BH cusps. However, the BH cusp quickly regains its steep slope due to its shorter relaxation time and continues to dominate the
evolution of the IMBH binary, despite being much less massive compared to the
stellar component. We uncover an interesting mechanism in which BHs first efficiently extract energy from the IMBH binary and then transfer this energy to the surrounding
stars, allowing the BHs to spiral back toward the center of the system and restart the process. Our results imply that, although
stellar mass BHs are a minor component of a
stellar population, they can significantly facilitate IMBH growth within NSCs via mergers. We also notice that these dense systems can potentially boost Intermediate Mass Ratio Inspirals (IMRIs) predominantly on radial orbits.
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All authors Fazeel Mahmood Khan, Peter Berczik, Margarita Sobolenko, Andreas Just, Rainer Spurzem, Kelly Holley-Bockelmann, Andrea Valerio Macciò
Astrophysics of Galaxies
The abundance of thin dwarf galaxies: a challenge for cosmological simulations
José A. Benavides, Laura V. Sales, Julio F. Navarro et al. (+4 more)
We study the prevalence of thin
galaxies as a function of
stellar mass in the range $10^7 < M_{\star} / \rm{M_\odot} < 10^{11}$ using data from the GAMA, DESI, ALFALFA, and Nearby
Galaxy catalogs. We use the distribution of projected axis ratios, $q$, to infer the abundance of intrinsically flat
galaxies needed to reproduce the observed abundance of highly elongated systems in projection. We find that as many as $40\%$ of
galaxies in the mass range $10^9<M_{\star}/\rm{M_\odot}<10^{10}$ are intrinsically flatter than $1$:$5$ (i.e., $c/a<0.2$), a fraction that rises to $\sim 80\%$ for $c/a<0.3$. Although the incidence of thin
galaxies decreases towards lower and higher $M_{\star}$, they are still quite common in
dwarfs: $\sim 30\%$ and $\sim 65\%$ of $\sim 10^8 ~ \rm{M_\odot}$
galaxies are inferred to be intrinsically flatter than $c/a=0.2$ and $0.3$, respectively. A comparison of these results with several state-of-the-art cosmological hydrodynamical simulations (TNG50, FIREbox, Romulus25) reveals a distinctive lack of thin simulated
dwarfs. In particular, there are no $M_{\star} < 10^9 ~ \rm{M_{\odot}}$ simulated
galaxies flatter than $c/a=0.2$, in clear contrast with observational samples. This discrepancy likely reflects limitations in resolution and in the treatment of baryonic physics, suggesting that our understanding of the mechanisms regulating the formation of disk
galaxies less massive than the Milky Way is still quite incomplete. Our results present a clear challenge to current numerical models of
dwarf galaxy formation, which future models should attempt to meet.
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All authors José A. Benavides, Laura V. Sales, Julio F. Navarro, Simon D. M. White, Carlos S. Frenk, Kyle A. Oman, Shaun Cole
Astrophysics of Galaxies
Dynamical disequilibrium in dwarf galaxies: rethinking gas dynamics, rotation curves, and dark matter inference
Diego Dado, Kyle A. Oman, Katherine E. Harborne et al. (+9 more)
We quantify departures from hydrodynamical and centrifugal
equilibrium in the gas discs of low-mass ($10^{10.75}<M_\mathrm{200c}/\mathrm{M}_\odot<10^{11}$)
galaxies from the COLIBRE cosmological hydrodynamical simulations. We evaluate the full Eulerian acceleration balance in the midplane and show that disequilibrium is widespread:
equilibrium-based circular velocity estimates typically have errors of $\geq 10$ per cent ($\approx 75$ per cent of midplane gas by mass). Disequilibrium is strongest and the largest associated errors occur in the inner few kiloparsecs that are crucial for constraining the dark matter density profile. Correcting the circular velocity to account for pressure and convective terms does not reliably improve its recovery in strongly perturbed systems where time-dependent forces dominate the residual acceleration budget.
Stellar feedback, self-gravitating gas clumps and AGN energy injection account for most strong local perturbations, and large-scale gravitational asymmetries act as a scaffold for disequilibrium. We classify gas discs into coherent, perturbed, and slow/erratic rotators and show that this classification correlates with
galaxy properties like mass, morphology and tracers of recent feedback. A majority of
galaxies in our sample would be unsuitable for standard rotation curve analysis. Much of the observed diversity in the shapes of
dwarf galaxy rotation curves may stem from non-
equilibrium gas motions rather than diversity in mass profiles - resolving the discrepancy is then first and foremost a problem in gas dynamics.
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All authors Diego Dado, Kyle A. Oman, Katherine E. Harborne, Francesca Fragkoudi, Joop Schaye, Matthieu Schaller, Alejandro Benítez-Llambay, Evgenii Chaikin, Carlos S. Frenk, Filip Huško, Sylvia Ploeckinger, Alexander J. Richings
High Energy Astrophysical Phenomena
Impact of in situ nuclear networks and atomic opacities on neutron star merger ejecta dynamics, nucleosynthesis, and kilonovae
Fabio Magistrelli, Sebastiano Bernuzzi, Albino Perego et al. (+2 more)
Modeling binary
neutron star merger (BNSM) ejecta
evolution requires simulations involving hydrodynamics,
nuclear reactions, and radiative processes. The impact of
nuclear burning and atomic opacity is poorly understood and often treated with simplified prescriptions. We systematically investigate different treatments of
nuclear heating, thermalization, and opacities in radiation-hydrodynamics simulations of BNSM ejecta and kilonova light curves. Ejecta from long-term numerical-relativity simulations are evolved to ~30 days using a 2D ray-by-ray approach. We compare simplified heating-rates, thermalization prescriptions, and gray opacities with in-situ
nuclear networks (NN) that track energy deposition, and include a composition-dependent thermalization scheme and frequency-dependent, atomic-physics-based opacities. Coupling NN and hydrodynamics affects nucleosynthesis and kilonova emission. Assuming homologous expansion alters the abundance
evolution and produces a narrower second $r$-process peak and a third peak shifted to higher mass numbers.
Nuclear heating back-reaction delays and reddens the early emission. A constant thermalization underestimates the early luminosity and overestimates the late emission. Analytical opacities yield dimmer and redder kilonovae at early times ($t\lesssim$ hour) and a prolonged emission at $t\gtrsim5$ days. Resolving the first hundreds of milliseconds of hydrodynamics is essential for robust nucleosynthesis calculations, and composition-dependent thermalization and frequency-dependent, atomic opacities are needed to accurately capture the ejecta temperature and kilonova brightness and color
evolution. Analytic
nuclear-power fits with simplified thermalization and opacities can reproduce the density and temperature
evolution of the ejecta. [Abridged].
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All authors Fabio Magistrelli, Sebastiano Bernuzzi, Albino Perego, Maximilian Jacobi, Christopher J. Fontes
Astrophysics of Galaxies
Chemical composition and enrichment of the Centaurus cluster core seen by XRISM/Resolve
F. Mernier, K. Fukushima, A. Simionescu et al. (+16 more)
Hot, X-ray emitting atmospheres pervading
galaxy clusters are rich in metals, which have been synthesised and released by asymptotic
giant branch (AGB)
stars, core-collapse
supernovae (SNcc) and Type Ia
supernovae (SNIa) over
cosmic history. This makes the intracluster medium (ICM) an ideal astrophysical system to constrain its chemical composition, hence ultimately understand metal production and enrichment on megaparsec scales. In this work, we take advantage of the unprecedented ~5 eV resolution offered by XRISM/Resolve to measure the chemical composition of the core of the bright, nearby, and metal-rich Centaurus cluster (287 ks) with unprecedented accuracy. We use these measurements to provide constraints on the
stellar populations having enriched the cluster core. We derived the Fe abundance and its relative Si/Fe, S/Fe, Ar/Fe, Ca/Fe, Cr/Fe, Mn/Fe, and Ni/Fe ratios. We completed this high-resolution view with N/Fe, O/Fe, Ne/Fe, and Mg/Fe ratios obtained with XMM-Newton/RGS archival data. Similarly to the core of Perseus, we find that nine out of our 11 measured abundance ratios are formally consistent with the chemical composition of our
Solar System. However, the (super-
solar) N/Fe and (half-
solar) Mg/Fe ratios significantly differ from Perseus and/or other systems, thus provide tension with the picture of a fully
solar composition ubiquitous to all systems. In addition, possible uncertainties in O/Fe and Ne/Fe with atomic codes highlight the need for studying more systems at high spectral resolution to assess (or rule out) the universality of the ICM composition in clusters' cool cores. Combinations of (AGB+)SNcc+SNIa yield models can reproduce our observed X/Fe ratios in all cases. However, whether two distinct populations of SNIa are needed depends on the weight of our RGS measurements. We also briefly discuss the possibility of a multi-
metallicity gas phase in this respect.
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All authors F. Mernier, K. Fukushima, A. Simionescu, M. Kondo, A. Majumder, T. Plšek, N. Werner, Y. Fujita, K. Sato, K. Matsushita, M. Loewenstein, R. Mushotzky, J.-P. Breuer, R. Fujimoto, Y. Fukazawa, I. Hatsukade, K. Nakazawa, M. Urata, N. Yamasaki
High Energy Astrophysical Phenomena · Cross-listed from hep-ph
Constraints on light QCD and CP-violating axions from the death line of rotation-powered pulsars
Samuel J. Witte, Andrea Caputo, Stefan Stelzl et al. (+3 more)
Dense
nuclear matter can modify the effective potential of
axions, displacing them from their
vacuum minimum, and sourcing large external field gradients (“
axion hair"). In the case of
neutron stars,
axion hair directly modifies the electrodynamic processes operating on the open field-line region, strongly enhancing or suppressing the acceleration experienced by ambient charges. As a result, the point in the
neutron star lifetime at which pair-cascades cease – known as
pulsar “death" – can be dramatically altered, allowing for much older
pulsars to emit observable
radio emission. We study the pair discharge process in the presence of
axion hair using semi-analytic techniques and particle-in-
cell simulations, and use these results alongside
pulsar demographics to derive new constraints on light QCD
axions with non-negligible
axion-
photon coupling and CP-violating
axion-nucleon interactions. We also illustrate how nearly orthogonal rotators, where emission is observed from both poles (such as in the case of PSR J1906+0746), provides a complementary probe of
axion hair.
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All authors Samuel J. Witte, Andrea Caputo, Stefan Stelzl, Alexander Chernoglazov, Alexander A. Philippov, Surjeet Rajendran
Astrophysics of Galaxies
An Active Galaxy Cluster Merger at Cosmic Noon Revealed by JWST Weak Lensing and Multiwavelength Probes
Zachary P. Scofield, Kyle Finner, Hyungjin Joo et al. (+8 more)
The
galaxy cluster XLSSC~122 is a rare system at $z = 1.98$, hosting surprisingly evolved member
galaxies when the Universe was only one-third of its present age. Leveraging deep JWST/NIRCam imaging, we perform a weak-
lensing analysis and reconstruct the cluster's mass distribution, finding a mass peak that coincides with both the X-ray peak and the position of the brightest cluster
galaxy. We obtain a mass estimate of $M_{200\rm c}=1.6 \pm 0.3\times 10^{14}~M_{\odot}$ and a concentration of $c_{200 \rm c}=6.3 \pm 0.3$ implied by the preferred concentration–mass relation, in agreement with recent strong-
lensing estimates. The high concentration in particular motivates tests against empirical and simulation-derived concentration–mass relations. Placing our weak-
lensing mass map in the context of Chandra X-ray data, MeerKAT
radio imaging, ALMA+ACA/ACT Sunyaev-Zel'dovich (SZ) mapping, and new JWST intracluster light measurements, we identify consistent NE–SW elongation across
datasets and a pronounced offset along the same axis between the SZ and mass/X-ray peaks, pointing to significant merger activity. XLSSC~122 thus serves as a JWST pilot study for high-$z$
lensing, demonstrating the
telescope's unique ability to map cluster mass distributions at $z\sim 2$ and motivating a uniform sample of analogous systems with joint
lensing, X-ray, SZ, and
radio data to probe cluster assembly at
cosmic noon.
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All authors Zachary P. Scofield, Kyle Finner, Hyungjin Joo, M. James Jee, Wonki Lee, Sangjun Cha, Jinhyub Kim, Yu-Heng Lin, Ranga-Ram Chary, Andreas Faisst, Bomee Lee
Cosmology and Nongalactic Astrophysics
Geometry of non-Gaussianity in transient non-attractor inflation
Mohammad Hossein Namjoo and Bahar Nikbakht
Inflationary models predicting abundant
primordial black holes (PBHs) and large amplitude of scalar-induced gravitational waves (SIGWs) often rely on amplified fluctuations over limited scales, typically driven by phase transitions, particle production, or departures from slow-roll
evolution. While the power spectrum of these models has been extensively studied, higher-order correlations are much less understood. Motivated by the complex physics involved and the fact that PBH and SIGW formation are both sensitive to non-linearities, we present a detailed study of the bispectrum as the leading non-linear effect in these scenarios. We refer to the scale- and shape-dependence of the bispectrum collectively as its geometry; and define a scale-dependent shape correlator to disentangle the two dependencies. Generally, we find that for the scales most affected by phase transitions and particle production (including the power spectrum peak), the bispectrum is strongest near the equilateral configuration, while non-attractor phases tend to produce correlations near the squeezed configuration. We further propose a simplified bispectrum
estimator, resembling local-type non-Gaussianity but with scale-dependent amplitude, that captures the main features of the full bispectrum. As an implication of our results, we show that incorporating the bispectrum significantly broadens the range of scales with a substantial probability of large smoothed density contrasts compared to linear analysis. This suggests that non-linearities can alter not only PBH abundance and SIGW amplitude but also their mass and frequency spectra. In particular, and in contrast with the usual assumption, our results hint that the second-highest peak of the power spectrum may produce more PBHs than the highest peak.
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Instrumentation and Methods for Astrophysics
Stellar physics at sub-nanoradian angular resolution
P. Batista, J. Biteau, C. Carlile et al. (+36 more)
Many
stars – if they could be imaged with enough angular resolution – would exhibit features expected from theory but not possible to extract from spectra. We may group these by increasing complexity as follows. First, smooth variations in brightness across the surface, resembling
solar limb darkening but much more prominent and involving more processes in
stars with fast
spin or external tides. Next, there are periodic features: not only oscillations, but also convective
cells and starspots, which appear to transit across a
star as its
spins, and
exoplanets that really do transit across the
star. Then, there are transients like
flares. Current optical interferometers provide synthetic apertures of a few hundred metres and angular resolutions down to about nanoradian ($\simeq 0.2\,$milliarcsecond), enough to resolve some of the above features on the nearest upper main-sequence
stars,
giants and supergiants. Ongoing projects aims to km-scale synthetic apertures, enough to measure the radius of the nearest white
dwarf. In this White Paper we briefly discuss what could be observed with synthetic apertures over $\sim20\,$km – resolving detail on white
dwarfs at the level currently possible on supergiants.
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All authors P. Batista, J. Biteau, C. Carlile, J. Cortina, D. Della Volpe, D. Dravins, M. Fiori, S. Funk, W. Guerin, T. Hassan, C. Ingenhütt, I. Jiménez Martínez, R. Kaiser, G. Koziol, O. Lai, Q. Luce, E. Lyard, R. Mirzoyan, A. W. M. Mitchell, A. Nomerotski, N. Produit, A. Raiola, P. Saha, T. Schweizer, V. Sliusar, A. Spolon, L. Stanic, R. Walter, L. Zampieri, J. von Zanthier, A. Zmija, J. Aufdenberg, C. F. Bender, J. J. Hermes, D. Kieda, M. Lisa, A. Mueninghoff, K. N. Rai, K. van Tilburg
Cosmology and Nongalactic Astrophysics
Evidence of galaxy cluster rotation and intrahalo gas motions in the cosmic microwave background
Samuel Goldstein and J. Colin Hill
We report the first robust evidence for the rotational kinematic Sunyaev-Zel'dovich (rkSZ) effect: the dipolar signal produced by the Thomson scattering of
cosmic microwave background (CMB)
photons off intracluster gas in dynamically active systems (including rotations and mergers). By combining CMB intensity and polarization measurements from the Planck satellite with spectroscopic member-
galaxy redshifts from the Sloan Digital Sky Survey in a sample of 25 X-ray cross-matched, low-
redshift ($0.02< z< 0.09)$, massive ($10^{13.9}\lesssim M_{\rm 500c}/M_\odot \lesssim 10^{14.6}$)
galaxy clusters, we detect a dipolar rkSZ signature aligned with the estimated angular momentum of each cluster, ruling out a chance fluctuation at 99.98% confidence (3.6$\sigma$). The significance of this measurement is enhanced by several new methodological improvements for isolating the rkSZ signal from primary CMB fluctuations and noise. The amplitude and shape of the signal are qualitatively consistent with predictions from state-of-the-art hydrodynamical simulations. These results establish a new tool with which to probe the dynamical state of
galaxy clusters using CMB data.
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