Cosmology and Nongalactic Astrophysics
Cosmological back-reaction of baryons on dark matter in the CAMELS simulations
Matthew Gebhardt, Daniel Anglés-Alcázar, Shy Genel et al. (+13 more)
Baryonic processes such as radiative cooling and feedback from massive
stars and active
galactic nuclei (AGN) directly redistribute
baryons in the Universe but also indirectly redistribute dark matter due to changes in the gravitational potential. In this work, we investigate this "back-reaction" of
baryons on dark matter using thousands of cosmological hydrodynamic simulations from the Cosmology and Astrophysics with MachinE Learning Simulations (CAMELS) project, including parameter variations in the SIMBA, IllustrisTNG, ASTRID, and Swift-EAGLE
galaxy formation models. Matching
haloes to corresponding N-body (dark matter-only) simulations, we find that virial masses decrease owing to the ejection of
baryons by feedback. Relative to N-body simulations,
halo profiles show an increased dark matter density in the center (due to radiative cooling) and a decrease in density farther out (due to feedback), with both effects being strongest in SIMBA (> 450% increase at r < 0.01 Rvir). The clustering of dark matter strongly responds to changes in baryonic physics, with dark matter power spectra in some simulations from each model showing as much as 20% suppression or increase in power at k ~ 10 h/Mpc relative to N-body simulations. We find that the dark matter back-reaction depends intrinsically on cosmology (Omega_m and sigma_8) at fixed baryonic physics, and varies strongly with the details of the feedback implementation. These results emphasize the need for marginalizing over uncertainties in baryonic physics to extract cosmological information from weak
lensing surveys as well as their potential to constrain feedback models in
galaxy evolution.
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All authors Matthew Gebhardt, Daniel Anglés-Alcázar, Shy Genel, Daisuke Nagai, Boon Kiat Oh, Isabel Medlock, Jonathan Mercedes-Feliz, Sagan Sutherland, Max E. Lee, Xavier Sims, Christopher C. Lovell, David N. Spergel, Romeel Davé, Matthieu Schaller, Joop Schaye, Francisco Villaescusa-Navarro
Astrophysics of Galaxies
GA-NIFS: high prevalence of dusty and metal-enriched outflows in massive and luminous star-forming galaxies at $z\sim3-9$
B. Rodríguez Del Pino, S. Arribas, M. Perna et al. (+16 more)
We present a search for and characterization of ionized
outflows in 15
star-forming systems at $z\sim3-9$ with no evidence of Active
Galactic Nuclei (AGN), observed with JWST/NIRSpec IFU as part of the GA-NIFS program. The targets often show satellites and complex substructure, from which we isolate 40
galaxies/regions. The sample probes the high-mass end of the
galaxy population, with most sources having log$_{10}$~(M$_\star$/M$_\odot$)=$9.5-11$, extending previous studies on high-z
star formation driven
outflows that mainly focused on lower-mass
galaxies. Using the [OIII]5007 and H$\alpha$ emission lines, we identify broad kinematic components consistent with
galactic outflows in 14
galaxies/regions. We find that the outflowing gas is more
dust attenuated (by $A_{\rm V}$$\sim0.59$ mag on average) and metal-enriched (0.13 dex) than the interstellar medium (ISM) of the host
galaxies, but its velocities are insufficient to escape the
galaxies and reach the circumgalactic medium, suggesting that
outflows mainly redistribute
dust and metals around their hosts. The
outflows identified in this study display velocity dispersions within $\sigma_{\rm out}=130-340$~km~s$^{-1}$ and
outflow velocities $v_{\rm out}=170-600$~km~s$^{-1}$, and, when combined with less luminous and less massive
star-forming
galaxies from previous works, reveal a statistically significant correlation between $v_{\rm out}$ and
star formation rate (SFR). The typically low mass-loading factors ($\eta=\dot{M}_{\rm out}/SFR$$\leq1$, in 9 out of 14 the
outflows) indicate that these
outflows do not strongly suppress
star formation. Overall, our results suggest that ejective feedback via ionized
outflows is inefficient in massive, luminous
star-forming
galaxies within the first 2 Gyr of the Universe.
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All authors B. Rodríguez Del Pino, S. Arribas, M. Perna, I. Lamperti, A. Bunker, S. Carniani, S. Charlot, F. D'Eugenio, R. Maiolino, H. Übler, E. Bertola, T. Böker, G. Cresci, G. C. Jones, C. Marconcini, E. Parlanti, J. Scholtz, G. Venturi, S. Zamora
High Energy Astrophysical Phenomena
Masers and Broad-Line Mapping Favor Magnetically-Dominated AGN Accretion Disks
Philip F. Hopkins, Dalya Baron and Joanna M. Piotrowska
We present a novel and powerful constraint on the physics of supermassive black hole (BH)
accretion disks. We show that in the outer disk (radii $R \gtrsim 0.01\,$pc or $\gtrsim 1000\,R_{G}$), models supported by thermal or radiation pressure predict disk masses which are much larger than the BH mass and increase with radius - i.e. rapidly-rising, extremely non-Keplerian rotation curves. More generally, we show that any observational upper limit to the deviation from Keplerian potentials at these radii directly constrains the physical form of the pressure in disks. We then show that existing maser and broad line region (BLR) kinematic observations immediately rule out the classic thermal-pressure-dominated Shakura Sunyaev-like $\alpha$-disk model, and indeed rule out any thermal or radiation (or
cosmic-ray) pressure-dominated disk, as the required temperatures and luminosities of the gas at large radii would exceed those observed by orders of magnitude. We show that models where the pressure comes entirely from
turbulence (without thermal, radiation, or
magnetic sources) could in principle be viable but would require turbulent Toomre $Q \gtrsim 100$, far larger than predicted by self gravitating/gravito-turbulent models. However, recently proposed models of
magnetic pressure-dominated disks agree with all of the observational constraints. These magnetically-dominated models also appear to agree better with constraints on maser
magnetic fields, compared to the other possibilities. Observations appear to strongly favor the hypothesis that the outer regions of BH
accretion disks are in the 'hyper-magnetized' state.
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Solar and Stellar Astrophysics
Formation of massive multiple-star systems: early migration and mergers
Sunmyon Chon and Alejandro Vigna-Gómez
Massive
stars are often found in multiple systems, yet how binary-
star systems with very close separations ($\lesssim$ au) assemble remains unresolved. We investigate the formation and inward migration of massive-
star binaries in
Solar-
metallicity environments using the
star-cluster formation simulation of Chon et al. (2024), which forms a $1200\,M_\odot$
stellar cluster and resolves binaries down to 1 au separation. Our results indicate that
stars more massive than $2\,M_{\odot}$ predominantly assemble in binary or triple configurations, in agreement with observations, with member
stars forming nearly coevally. In most of these systems, the inner binary hardens by one to three orders of magnitude and reaches a steady-state within the first $0.1\,$Myr. Notably, all binaries whose final separations are below 10 au are hardened with the aid of circumbinary discs, highlighting disc-driven migration as a key to produce tight massive binaries. We further find that binaries form with random inclinations relative to the initial rotation axis of the cloud, and that mutual inclinations in triple systems follow an isotropic distribution, implying that
stochastic interactions driven by
turbulence and few-body dynamics are crucial during assembly and migration. Finally,
stars with $M>2\,M_{\odot}$ often undergo repeated merger events during cluster
evolution, yielding extreme mass ratios ($q<0.1$). Some of these products may evolve into compact-object binaries containing a black hole or
neutron star, including X-ray binaries and systems detectable by
Gaia.
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Astrophysics of Galaxies
Characterizing turbulence in galaxy clusters: Defining turbulent energies and assessing multi-scale versus fixed-scale filters
Lorenzo Maria Perrone, Thomas Berlok, Ewald Puchwein et al. (+1 more)
Disentangling
turbulence and bulk motions in the intracluster medium (ICM) of
galaxy clusters is inherently ambiguous, as the
plasma is continuously stirred by different processes on disparate scales. This poses a serious problem in the interpretation of both observations and numerical simulations. In this paper, we use filtering operators in real space to separate bulk motion from
turbulence at different scales. We show how filters can be used to define consistent kinetic and
magnetic energies for the bulk and turbulent component. We apply our GPU-accelerated filtering pipeline to a simulation of a major
galaxy cluster merger, which is part of the PICO-Clusters suite of zoom-in cosmological simulations of massive clusters using the moving mesh code Arepo and the IllustrisTNG
galaxy formation model. We find that during the merger the turbulent pressure fraction on physical scales of $\lesssim$50 kpc reaches a maximum of 5%, before decreasing to 2% after $\sim$1.3 Gyr from the core passage. These low values are consistent with recent observations of clusters with XRISM, and suggest that unless a cluster was recently perturbed by a major merger,
turbulence levels are low. We then reexamine the popular multi-scale iterative filter method. In our tests, we find that its use can introduce artifacts, and that it does not reliably disentangle fluctuations living on widely separated length scales. Rather, we believe it is more fruitful to use fixed-scale filters and turbulent energies to compare between simulations and observations. This work significantly improves our understanding of
turbulence generation by major mergers in
galaxy clusters, which can be probed by XRISM and next-generation X-ray
telescopes, allowing us to connect high-resolution cosmological simulations to observations.
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All authors Lorenzo Maria Perrone, Thomas Berlok, Ewald Puchwein, Christoph Pfrommer
Instrumentation and Methods for Astrophysics
Transiting exoplanets as the immediate future for population-level atmospheric science
Joanna K. Barstow, Hannah R. Wakeford, Sarah L. Casewell et al. (+1 more)
The transit method, during which a
planet's presence is inferred by measuring the reduction in flux as it passes in front of its parent
star, is a highly successful
exoplanet detection and characterization technique. During transit, the small fraction of starlight that passes through a
planet's atmosphere emerges with the fingerprints of atmospheric gases, aerosols and structure. During eclipse, the relatively small contribution of light from the
planet itself may be observed as the
planet is occulted by the
star. For
planets in near-edge-on, short-period orbits, observing the system throughout an entire orbit allows the varying flux from the
planet to be extracted as the illuminated `dayside' rotates in and out of view. With spectroscopic observations, we can characterize not only the overall composition of the atmosphere, but also glean insights into atmospheric structure and dynamics. With over 6,000 transiting
planets now discovered, such observations are currently our only window into a consistent sample of planetary atmospheres large enough to attempt a population-level study, a critical next step for our understanding of atmospheric science. The vast
exoplanet population provides a laboratory for atmospheric physics, including chemistry, dynamics, cloud processes and
evolution; extending these results to a larger number of targets will allow us to explore the effects of
equilibrium temperature,
gravity, mass and parent
star type on atmospheric properties, as well as map observable trends to formation scenarios. These findings are critical for addressing STFC's Science
Vision Challenge B: how do
stars and planetary systems develop and how do they support the existence of life?. Here we outline how the UK must fit within this strategic context, suggest approaches and development for the future, and outline the unique capabilities and leadership of scientists across the UK.
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All authors Joanna K. Barstow, Hannah R. Wakeford, Sarah L. Casewell, Vatsal Panwar
Instrumentation and Methods for Astrophysics
Exoplanet characterization with NASA's Habitable Worlds Observatory
Joanna K. Barstow, Beth Biller, Mei Ting Mak et al. (+3 more)
Exoplanet atmosphere characterization has seen revolutionary advances over the last few years, providing us with unique insights into atmospheric chemistry, dynamics and
planet formation mechanisms. However, true
solar system analog
planets remain inaccessible. A major goal for
exoplanet science over the coming decades is to observe, and characterize, temperate rocky
planets and cool gas
giants in orbit around
solar-type
stars, with the prospect of detecting signs of habitability or even life. Characterization and categorization of these
planets relies on direct spectroscopic observations capable of identifying molecular species in their atmospheres; however, these observations represent a substantial engineering challenge due to the extreme contrast between a temperate, Earth-sized
exoplanet and its parent
star. NASA's next flagship mission, the Habitable Worlds Observatory (HWO) - planned for launch in the mid-2040s - will boast a coronagraphic instrument capable of reaching the needed 10$^{-10}$ contrast, on an ultrastable platform enabling long integration times to achieve the required signal to noise. HWO will cover near-ultraviolet to the near-infrared wavelengths, enabling detections of key biosignature molecules and habitability indicators such as ocean glint and a vegetation `red edge'. Via early involvement in this groundbreaking observatory, including a potential UK instrument contribution, the UK
exoplanet community now has an important opportunity to influence the
telescope's design. To maintain our international competitiveness, we must be at the forefront of observational campaigns with HWO when it eventually launches, and this comes with the need for parallel development in laboratory astrophysics and computational modelling. Maximising our exploitation of this transformative NASA mission requires consistent financial support in these areas across the next two decades.
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All authors Joanna K. Barstow, Beth Biller, Mei Ting Mak, Sarah Rugheimer, Amaury Triaud, Hannah R. Wakeford
Cosmology and Nongalactic Astrophysics
Primordial black holes: constraints, potential evidence and prospects
Bernard Carr, Antonio J. Iovino, Gabriele Perna et al. (+2 more)
Primordial black holes (PBHs) may have formed in the early Universe and may account for all or part of the dark matter. In this review, we summarize the current observational constraints on PBHs across the full mass range, highlight potential evidence for their existence, and outline the prospects for future searches, particularly with gravitational-wave observatories. We also discuss different PBH formation scenarios, identify the corresponding mass functions, and present the observational constraints in each case.
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All authors Bernard Carr, Antonio J. Iovino, Gabriele Perna, Ville Vaskonen, Hardi Veermäe
Cosmology and Nongalactic Astrophysics
Weak lensing of bright standard sirens: prospects for $\sigma_8$
Ville Vaskonen
Gravitational wave events with electromagnetic counterparts provide direct measurements of the Hubble diagram. We demonstrate that incorporating weak
lensing into bright standard siren analyses allows measurements of cosmological parameters that do not influence the mean luminosity distance-
redshift relation but do impact the
cosmic structures. In particular, we examine the prospects for measuring the standard deviation of matter perturbations $\sigma_8$, in addition to the Hubble constant and the matter abundance. We find that a $10\%$ measurement of $\sigma_8$ would be feasible with ET, provided a population of $300$
neutron star binaries with electromagnetic counterparts is observed. With LISA, the measurement of $\sigma_8$ would have $30\%$ accuracy, assuming a population of $12$ massive black hole binaries with electromagnetic counterparts is observed.
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Cosmology and Nongalactic Astrophysics
Probing Cosmic Expansion and Early Universe with Einstein Telescope
Angelo Ricciardone, Mairi Sakellariadou, Archisman Ghosh et al. (+52 more)
Over the next two decades, gravitational-wave (GW) observations are expected to evolve from a discovery-driven endeavour into a precision tool for astrophysics, cosmology, and fundamental physics. Current second-generation ground-based detectors have established the existence of compact-binary mergers and enabled GW multi-messenger astronomy, but they remain limited in sensitivity,
redshift reach, frequency coverage, and duty cycle. These limitations prevent them from addressing many fundamental open questions in cosmology. By the 2040s, wide-field electromagnetic surveys will have mapped the luminous Universe with unprecedented depth and accuracy. Nevertheless, key problems including the nature of dark matter, the physical origin of
cosmic acceleration, the properties of
gravity on cosmological scales, and the physical conditions of the earliest moments after the Big Bang will remain only partially constrained by electromagnetic observations alone. Progress on these fronts requires access to physical processes and epochs that do not emit light. Gravitational waves provide a unique and complementary observational channel: they propagate over cosmological distances largely unaffected by intervening matter, probe extreme astrophysical environments, and respond directly to the geometry of spacetime. In this context, next-generation GW observatories such as the Einstein
Telescope (ET) will be transformative for European astronomy. Operating at sensitivities and frequencies beyond existing detectors, ET will observe binary black holes and
neutron stars out to previously inaccessible
redshifts, enable continuous high signal-to-noise monitoring of compact sources, and detect gravitational-wave backgrounds of astrophysical and cosmological origin. Together with space-based detectors, ET will play a central role in advancing our understanding of
cosmic evolution and fundamental physics.
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All authors Angelo Ricciardone, Mairi Sakellariadou, Archisman Ghosh, Alessandro Agapito, M. Celeste Artale, Michael Bacchi, Tessa Baker, Marco Baldi, Nicola Bartolo, Andrea Begnoni, Enis Belgacem, Marek Biesiada, Jose J. Blanco-Pillado, Tomasz Bulik, Marica Branchesi, Gianluca Calcagni, Giulia Capurri, Carmelita Carbone, Roberto Casadio, J.A.R. Cembranos, Andrea Cozzumbo, Ivan De Martino, Jose M. Diego, Emanuela Dimastrogiovanni, Guillem Domènech, Ulyana Dupletsa, Hannah Duval, Gabriele Franciolini, Andrea Giusti, Giuseppe Greco, Lavinia Heisenberg, Alexander C. Jenkins, Sumit Kumar, Gaetano Lambiase, Michele Maggiore, Michele Mancarella, Federico Marulli, Sabino Matarrese, Isabela Santiago de Matos, Michele Moresco, Riccardo Murgia, Ilia Musco, Gabriele Perna, Michele Punturo, Diego Rubiera-Garcia, Javier Rubio, Alexander Sevrin, Riccardo Sturani, Matteo Tagliazucchi, Nicola Tamanini, Alessandro Tronconi, Ville Vaskonen, Daniele Vernieri, Stoytcho Yazadjiev, Ivonne Zavala
Astrophysics of Galaxies
VENUS: Two Faint Little Red Dots Separated by $\sim70\,\mathrm{pc}$ Hidden in a Single Lensed Galaxy at $z\sim7$
Hiroto Yanagisawa, Masami Ouchi, Miriam Golubchik et al. (+47 more)
We report the identification of a pair of faint little red dots (LRDs), dubbed Red Eyes, in a strongly-lensed
galaxy at $z\sim7$ behind the PLCKG004.5-10.5 cluster, identified from the JWST Treasury program VENUS. Red Eyes are spatially resolved on the image plane with distinct colors, while the critical curve lies far north of Red Eyes, clearly requiring two different LRDs rather than a single LRD. Red Eyes is an extremely close pair of LRDs separated by $\sim70\,\mathrm{pc}$ in the source plane with a magnification of $\mu\sim20$, which consistently explains another counter-image detected to the north-west. Red Eyes is hosted in a typical
star-forming
galaxy with $M_{\mathrm{UV,int}}\sim -19$, but its own UV emission is very faint ($M_{\mathrm{UV,int}} \gtrsim -16$). Moreover, Red Eyes does not reside at the
galaxy center but lies at an offset position of approximately one effective radius $R_{\mathrm{e}}$ away from the
galaxy center. If observed without
lensing, Red Eyes would appear as a typical
star-forming
galaxy at $z\sim 7$ with $M_{\mathrm{UV}}\sim -19$, showing no apparent LRD signatures in either morphology or SED. These results suggest that multiple off-center LRDs, similar to Red Eyes, may be commonly hidden in a typical high-$z$
star-forming
galaxy. In this case, various plausible scenarios may emerge, one of which is that intermediate-mass black holes (IMBHs) with $M_\mathrm{BH}\sim10^{4\text{--}6}\,M_\odot$ may form in
star clusters on a
stellar disk and contribute to the growth of the central supermassive black hole via mergers, with some IMBHs detectable as luminous LRDs in a sufficiently active and massive phase.
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All authors Hiroto Yanagisawa, Masami Ouchi, Miriam Golubchik, Masamune Oguri, Seiji Fujimoto, Vasily Kokorev, Gabriel Brammer, Fengwu Sun, Minami Nakane, Yuichi Harikane, Hiroya Umeda, Hollis B. Akins, Hakim Atek, Franz E. Bauer, Maruša Bradač, John Chisholm, Dan Coe, Jose M. Diego, Henry C. Ferguson, Steven L. Finkelstein, Lukas J. Furtak, Kohei Inayoshi, Anton M. Koekemoer, Jorryt Matthee, Rohan P. Naidu, Yoshiaki Ono, Richard Pan, Johan Richard, Luke Robbins, Chris Willott, Adi Zitrin, Ricardo O. Amorín, Larry D. Bradley, Volker Bromm, Christopher J. Conselice, Pratika Dayal, Jeyhan S. Kartaltepe, Paulo A. A. Lopes, Ray A. Lucas, Georgios E. Magdis, Nicholas S. Martis, Casey Papovich, Daniel Schaerer, Francesco Valentino, Eros Vanzella, Joseph F. V. Allingham, Norman A. Grogin, Mauro González-Otero, Massimo Ricotti, Rogier A. Windhorst
Astrophysics of Galaxies
Simulations of collision and sloshing in the galaxy group NGC 5098/5096
Richards P. Albuquerque, Gastão B. Lima Neto, Rubens E. G. Machado et al. (+2 more)
The study of
galaxy groups is essential to understanding the evolutionary history of large-scale structures in the Universe. These dense environments have a significant impact on
galaxy evolution, influencing their gas content, morphology, and
star formation activity. In this work we analyse in detail the system NGC~5098$/$5096 composed of two
galaxy groups. We performed hydrodynamical $N$-body simulations of a
galaxy group collision aimed at reproducing the gas sloshing and surface brightness distribution observed in X-ray data. We conducted a detailed X-ray analysis and generated mock image Chandra observations from our simulations. The resulting corrected mock image surface brightness profiles show good agreement with the observed data. The relative line-of-sight velocity between NGC~5098 and NGC~5096 is $v_{\mathrm{los}} = 700$ km s$^{-1}$, with a projected separation of $d_{\mathrm{proj}} = 155$ kpc, suggesting that the collision occurs nearly in the line-of-sight. Our simulations were performed with an inclination angle of $80^\circ$ in order to reproduce the dynamical constraints. We also find a correlation between the dark matter and intragroup light distributions when comparing the residual dark matter map with the intragroup light morphology. Our best-fitting model is consistent with these observational constraints and provides a plausible dynamical scenario for the current state of the NGC~5098 group interaction with NGC 5096.
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All authors Richards P. Albuquerque, Gastão B. Lima Neto, Rubens E. G. Machado, Hugo V. Capelato, Florence Durret
High Energy Astrophysical Phenomena · Cross-listed from nucl-th
Cassandra L. Armstrong, Brendan T. Reed, Tate Plohr et al. (+4 more)
Multi-messenger observations of
neutron stars (NSs) and their mergers have placed strong constraints on the dense-matter equation of state (EOS). The EOS, in turn, depends on microscopic
nuclear interactions that are described by
nuclear Hamiltonians. These
Hamiltonians are commonly derived within
chiral effective field theory (EFT). Ideally, multi-messenger observations of NSs could be used to directly inform our understanding of EFT interactions, but such a direct inference necessitates millions of model evaluations. This is computationally prohibitive because each evaluation requires us to calculate the EOS from a
Hamiltonian by solving the
quantum many-body problem with methods such as auxiliary-field
diffusion Monte Carlo (AFDMC), which provides very accurate and precise solutions but at a significant computational cost. Additionally, we need to solve the
stellar structure equations for each EOS which further slows down each model evaluation by a few seconds. In this work, we combine emulators for AFDMC calculations of
neutron matter, built using parametric
matrix models, and for the
stellar structure equations, built using multilayer perceptron neural networks, with the PyCBC data-analysis framework to enable a direct inference of coupling constants in an EFT
Hamiltonian using multi-messenger observations of NSs. We find that astrophysical data can provide informative constraints on two-nucleon couplings despite the high densities probed in NS interiors.
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All authors Cassandra L. Armstrong, Brendan T. Reed, Tate Plohr, Henrik Rose, Soumi De, Rahul Somasundaram, Ingo Tews
High Energy Astrophysical Phenomena
Investigating Active Galactic Nuclei variability with the Cherenkov Telescope Array Observatory
G. Grolleron, J. Biteau, M. Cerruti et al. (+21 more)
Blazars, a type of active
galactic nuclei (AGN) with relativistic jets pointed at the observer, exhibit flux variability across the electromagnetic spectrum due to particle acceleration in their jets. Power spectral density (PSD) studies show breaks at specific frequencies, particularly in X-rays, linked to the
accretion regime and black hole mass. However, very-high-energy gamma-ray PSD breaks remain unexplored due to current instrument limitations. The Cherenkov
Telescope Array Observatory (CTAO), with up to ten times greater sensitivity compared to current generation instruments, will allow precise PSD reconstruction and unprecedented study of blazar
flares. These
flares reveal key insights into particle acceleration,
photon production, and jet properties. The AGN monitoring and
flare programs in CTAO's Key Science Project aim to deepen our understanding of blazar emissions.
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All authors G. Grolleron, J. Biteau, M. Cerruti, R. Grau, L. Gréaux, T. Hovatta, J.-P. Lenain, E. Lindfors, W. Max-Moerbeck, D. Miceli, A. Moralejo, K. Nilsson, E. Prandini, E. Pueschel, S. Kankkunen, J. Becerra Gonzalez, J. Finke, M. Joshi, P. Morris, M. Petropoulou, A. Sarkar, P. Romano, S. Vercellone, M. Zacharias
Earth and Planetary Astrophysics
Setting up the physical principles of resilience in a model of the Earth System
Orfeu Bertolami and Magnus Nyström
Resilience is a property of social, ecological, social-ecological and biophysical systems. It describes the capacity of a system to cope with, adapt to and innovate in response to a changing surrounding. Given the current
climate change crisis, ensuring conditions for a sustainable future for the habitability on the
planet is fundamentally dependent on Earth System (ES) resilience. It is thus particularly relevant to establish a model that captures and frames resilience of the ES, most particularly in physical terms that can be influenced by human policy\footnote{See page 4 for examples of strategies}. In this work we propose that resilience can serve as a theoretical foundation when unpacking and describing metastable states of
equilibrium and energy dissipation in any dynamic description of the variables that characterise the ES. Since the impact of the human activities can be suitably gauged by the planetary boundaries (PBs) and the
planet's temperature is the net result of the multiple PB variables, such as $\text{CO}_2$ concentration and radiative forcing, atmospheric aerosol loading, atmospheric ozone depletion, etc, then resilience features arise once conditions to avoid an ES runaway to a state where the average temperature is much higher than the current one. Our model shows that this runaway can be prevented by the presence of metastable states and dynamic friction built out of the interaction among the PB variables once suitable conditions are satisfied. In this work these conditions are specified. As humanity moves away from Holocene conditions, we argue that resilience features arising from metastable states might be crucial for the ES to follow sustainable trajectories in the Anthropocene that prevent it run into a much hotter potential
equilibrium state.
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Astrophysics of Galaxies
An Improved UV-Optical Diagnostic for Rejuvenating Galaxies in the Local Universe and Implications for Galaxy Evolution
Dylan Lazarus and Laura C. Parker
Rejuvenating
galaxies are important probes of
galaxy evolution, yet identifying them observationally is challenging as constraining recent
star formation histories requires both photometric and spectroscopic data. We present a method for identifying rejuvenating
galaxies in the local Universe using ultraviolet (UV) imaging and optical spectroscopy, building on a recent selection that identifies a system as rejuvenating if it is quenched in the near-UV (NUV; tracing $\sim\!100\,\mathrm{Myr}$ timescales) but
star-forming in H$\alpha$ (tracing $\sim\!10\,\mathrm{Myr}$ timescales). Shortly after a
star formation episode, however, the NUV is dominated by the same massive
stars that power H$\alpha$, so these indicators do not always trace distinct timescales. To address this, we derive a relation that predicts the NUV emission associated with the ionizing O-
star population traced by H$\alpha$, enabling us to isolate the NUV contribution from longer-lived
stars (primarily B/A
stars with $M\lesssim\!20\,M_\odot$). Subtracting the predicted O-
star NUV from the
dust-corrected NUV yields a more reliable rejuvenation diagnostic. Using this method, we identify $\sim\!10^{4}$ rejuvenating
galaxies in a sample of Sloan Digital Sky Survey (SDSS)
galaxies ($\sim\!4.5\%$). These
galaxies have intermediate
stellar masses and are found primarily in lower-density environments, becoming increasingly rare toward the centers of groups and clusters. Rejuvenating
galaxies also exhibit systematically lower gas-phase
metallicities, consistent with fueling by the
accretion of metal-poor gas.
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Solar and Stellar Astrophysics
Radial differential rotation leading to dipole collapse in pre-main-sequence stars
A. Guseva, L. Manchon, L. Petitdemange et al. (+1 more)
Despite progress in the observations of
stellar magnetic fields, their physical mechanisms remain poorly understood. During the pre-main sequence (PMS) phase, the inner layers of
stars contract and a radiative core gradually develops. In contrast, the convective envelope is gradually braked through
magnetic interactions with the
accretion disk and winds. With developing differential rotation inside the
star, PMS phase is thus a critical period for
magnetic properties of
stars when strong initial dipoles can get perturbed, leading to the observed diversity in the magnetism on the main sequence (MS). In this work, we study the impact of differential rotation on such fields. We perform three-dimensional anelastic convective dynamo simulations of rotating spherical shells with an imposed differential rotation (shear) between the boundaries. Density,
gravity profiles and convective zone thicknesses were set close to those predicted in PMS low-mass
stars by one-dimensional
stellar evolution code Cesam2k20. Our results show that radial differential rotation can induce dipole collapse leading to weaker, oscillatory
magnetic fields. Differential rotation seems to perturb $\alpha^2$ dynamo mechanism, responsible for dipolar
magnetic fields, by shearing poloidal field lines and by affecting turbulent
magnetic transport processes. This collapse is moderated by the relative importance of shear compared to the vigor of convective motions, with exact stability criterion depending on the field strength and the size of the radiative core. Applying DNS-based stability criterion in PMS
stellar evolution models, we qualitatively reproduce the trends observed in the
magnetic topologies of low-mass
stars when assuming an efficient internal angular momentum redistribution. This suggests that
stellar magnetic properties are intimately related to the PMS angular momentum
evolution.
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All authors A. Guseva, L. Manchon, L. Petitdemange, C. Pinçon
Earth and Planetary Astrophysics
Chih-Chun Hsu, Jason J. Wang, Jerry W. Xuan et al. (+27 more)
We present a rotational velocity (vsini) survey of 32
stellar/substellar objects and
giant planets using Keck/KPIC high-resolution spectroscopy, including 6
giant planets (2-7 M$_\mathrm{Jup}$) and 25 substellar/
stellar companions (12-88 M$_\mathrm{Jup}$). Adding companions with
spin measurements from the literature, we construct a curated
spin sample for 43
benchmark stellar/substellar companions and
giant planets and 54 free-floating brown
dwarfs and planetary mass objects. We compare their
spins, parameterized as fractional breakup velocities at 10 Myr, assuming constant angular momentum
evolution. We find the first clear evidence that
giant planets exhibit distinct
spins versus low-mass brown
dwarf companions (10 to 40 M$_\mathrm{Jup}$) at 4-4.5 $\sigma$ significance assuming inclinations aligned with their orbits, while under randomly oriented inclinations the significance is at 1.6-2.1 $\sigma$. Our findings hold when considering various assumptions about
planets, and the mass ratio below 0.8% gives a clean cut for rotation between
giant planets and brown
dwarf companions. The higher fractional breakup velocities of
planets can be interpreted as less angular momentum loss through circumplanetary disk braking during the
planet formation phase. Brown
dwarf companions exhibit evidence of slower rotation compared to isolated brown
dwarfs, while
planets and planetary mass objects show similar
spins. Finally, our analysis of specific angular momentum versus age of 221
stellar/substellar objects below 0.1 M$_{\odot}$ with
spin measurements in the literature indicates that the substellar objects of 5-40 M$_\mathrm{Jup}$ retain much higher angular momenta compared to
stellar and substellar objects of 40-100 M$_\mathrm{Jup}$ after 10 Myr, when their initial angular momenta were set.
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All authors Chih-Chun Hsu, Jason J. Wang, Jerry W. Xuan, Yapeng Zhang, Jean-Baptiste Ruffio, Dimitri Mawet, Luke Finnerty, Katelyn Horstman, Julianne Cronin, Yinzi Xin, Ben Sappey, Daniel Echeverri, Nemanja Jovanovic, Ashley D. Baker, Randy Bartos, Geoffrey A. Blake, Benjamin Calvin, Sylvain Cetre, Jacques-Robert Delorme, Greg W. Doppmann, Michael P. Fitzgerald, Quinn M. Konopacky, Joshua Liberman, Ronald A. Lopez, Evan C. Morris, Jacklyn Pezzato, Tobias Schofield, Andrew Skemer, James K. Wallace, Ji Wang
High Energy Astrophysical Phenomena
Feasibility of event-by-event primary mass discrimination using radio observables and supervised machine learning
Washington R. de Carvalho Jr. and Lech Wiktor Piotrowski
In this work, we investigate the feasibility of event-by-event primary mass discrimination using
radio observables only. Although the analysis does not require an explicit reconstruction of the shower maximum ($X_{max}$), the discrimination power still arises from the sensitivity of the
radio observables to the longitudinal development of the extensive air shower (EAS). Such
radio-based approaches could be particularly relevant for
radio-only experiments, such as GRAND. To assess this feasibility, we obtained conservative upper limits for the discrimination accuracy using a supervised machine-learning (ML)
algorithm, namely a random forest (RF). The input features used were the peak electric fields and the spectral slopes, which have complementary discrimination power, along with the
antenna distances to the shower axis. The RF was trained and tested using large event sets generated by the fast
radio emission simulation and simplified detector response implemented in the RDSim framework. We obtained discrimination accuracies between 81% and 96% over the studied zenith range, even after normalizing each shower by its own electromagnetic energy. Since the analysis includes deliberately conservative choices, such as a large 10% uncertainty on the reconstructed EM energy, these quoted values should be interpreted as conservative upper limits suitable for a feasibility assessment. Our results demonstrate that event-by-event primary mass discrimination using
radio observables is, in principle, feasible.
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High Energy Astrophysical Phenomena · Cross-listed from nucl-th
Skyrme-Hartree-Fock-Bogoliubov mass models on a 3D mesh: V. The N2LO extension of the Skyrme EDF
G. Grams, W. Ryssens, A. Sánchez-Fernández et al. (+6 more)
We present BSkG5, the latest entry in the Brussels-Skyrme-on-a-Grid (BSkG) series and the first large-scale
nuclear structure model based on next-to-next-to-leading order (N2LO) Skyrme energy density functional (EDF). By extending the traditional Skyrme EDF ansatz with central terms containing up to four gradients, we are able to combine an excellent global description of
nuclear ground state properties with a stiff equation of state for pure
neutron matter that is consistent with all astronomical observations of
neutron stars. More precisely, the new model matches the accuracy of earlier BSkG models but with two parameters less: we achieve root-mean-square deviations of 0.649 MeV for 2457 atomic masses, 0.0267 fm for 810 charge radii, and 0.43 MeV for 45 primary fission barriers of actinide
nuclei. We demonstrate that the complexities of N2LO EDFs are not insurmountable, even for demanding many-body calculations.
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All authors G. Grams, W. Ryssens, A. Sánchez-Fernández, N. N. Shchechilin, L. González-Miret Zaragoza, P. Demol, N. Chamel, S. Goriely, M. Bender
Cosmology and Nongalactic Astrophysics
The Linear Point Standard Ruler with DESI DR1 and DR2 Data
N. Uberoi, F. Nikakhtar, N. Padmanabhan et al. (+45 more)
The linear point, a purely
geometric feature in the monopole of the two-point correlation function, has been proposed as an alternative standard ruler. Compared to the peak in the correlation function, it is more robust to late-time nonlinear effects at the percent level. In light of improved simulations and high quality data, we revisit the robustness of the linear point and use it as an alternative to template-based fitting approaches typically used in BAO analyses. We present the linear point measurements on
galaxy samples from the first and second data releases (DR1 and DR2) of the DESI survey. We convert the linear point into a dimensionless parameter $\alpha_{iso,LP}$, defined as the ratio of the linear point in the fiducial cosmology and the observed value, analogous to the isotropic BAO scaling parameter $\alpha_{iso}$ used in previous BAO measurements. Using the 2nd generation of AbacusSummit mock catalogs, we find that linear point measurements are more precise when calculated in the post-reconstruction regime with 15-60% smaller uncertainties than those pre-reconstruction. We find a systematic shift in the linear point measurements compared against the isotropic BAO measurements in mocks; we attribute this to the isotropic damping parameter responsible for smearing the linear point in the nonlinear regime. We propose a sample-dependent correction that mitigates the impact of late-time nonlinear effects. While this introduces a cosmology dependence in an otherwise model-independent measurement, this is necessary given the sub-percent precision dictated by current cosmological surveys. Comparing $\alpha_{iso,LP}$ with isotropic BAO measurements made on the DESI DR1 and DR2
galaxy samples, we find excellent agreement after applying this correction, particularly post-reconstruction. We discuss future scope regarding cosmological inference with linear point measurements.
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All authors N. Uberoi, F. Nikakhtar, N. Padmanabhan, R. K. Sheth, J. Aguilar, S. Ahlen, D. Bianchi, D. Brooks, F. J. Castander, T. Claybaugh, A. Cuceu, A. de la Macorra, A. Dey, B. Dey, P. Doel, J. E. Forero-Romero, E. Gaztañaga, S. Gontcho A Gontcho, G. Gutierrez, K. Honscheid, C. Howlett, M. Ishak, R. Joyce, D. Kirkby, T. Kisner, O. Lahav, C. Lamman, M. Landriau, L. Le Guillou, M. Manera, P. Martini, A. Meisner, R. Miquel, S. Nadathur, W. J. Percival, C. Poppett, F. Prada, I. Pérez-Ràfols, G. Rossi, L. Samushia, E. Sanchez, D. Schlegel, M. Schubnell, J. Silber, D. Sprayberry, G. Tarlé, B. A. Weaver, H. Zou
Astrophysics of Galaxies
Ultra Diffuse Galaxies in clusters : the peculiar gas loss of VCC 1964
Rhys Taylor, Vojtech Partík and Robert Minchin
Context : Ultra Diffuse
Galaxies are low surface brightness systems which have been detected in HI in the field, where their line widths sometimes indicate significant dark matter deficits. They are rarely detected in HI in clusters, making their dynamical properties difficult to assess. The relation between field and cluster populations is unclear. Aims : Detecting UDGs entering a cluster could give important clues to their
evolution, both in terms of their dynamics but also as to whether they are structurally similar - i.e. if cluster UDGs are generally the same as field UDGs except with less gas and an older
stellar population. Methods : We use data from two deep Arecibo surveys, the Arecibo
Galaxy Environment Survey and the Widefield Arecibo Virgo Environment Survey, to measure the gas content of the UDG-candidate VCC 1964. Optical properties are quantified from the Sloan Digital Sky Survey and DESI Legacy Surveys. Results : We find a significant 9 kpc offset between the HI and optical components of VCC 1964, no evidence of asymmetry in the HI, and only a modest deficiency level. This suggests a wholesale displacement of the gas content. The line width is 4-5 sigma deviant from the baryonic and over 6 sigma deviant from the optical forms of the Tully-Fisher relation. The optical component is blue and smooth. Conclusions : VCC 1964 is consistent with a UDG experiencing gas displacement due to ram pressure as it enters the cluster for the first time. Intriguingly, its dynamics imply a significant dark matter deficit, however we cannot rule out that this may be due to the gas being displaced out of
equilibrium.
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Cosmology and Nongalactic Astrophysics · Cross-listed from hep-ph
Gravitational Ionization by Schwarzschild Primordial Black Holes
Alexandra P. Klipfel and David I. Kaiser
Primordial black holes (PBHs) are theorized to form from the collapse of overdensities in the very early Universe. PBHs in the asteroid-mass range $10^{17} \, {\rm g}\lesssim M \lesssim 10^{23} \, {\rm g}$ could serve as all or most of the dark matter today, but are particularly difficult to detect due to their modest rates of Hawking emission and sub-micron Schwarzschild radii. We consider whether the steep gradients of a PBH's gravitational field could generate
tidal forces strong enough to disrupt atoms and
nuclei. Such phenomena may yield new observables that could uniquely distinguish a PBH from a macroscopic object of the same mass. We first consider the gravitational ionization of ambient neutral hydrogen and evaluate prospects for detecting
photon radiation from the recombination of ionized atoms. During the present epoch, this effect would be swamped by Hawking radiation – which would itself be difficult to detect for PBHs at the upper end of the asteroid-mass window. We then consider the gravitational ionization and heating of neutral hydrogen immediately following recombination at $z\simeq1090$, and identify a broad class of PBH distributions with typical mass $5\times10^{21}\,{\rm g}\lesssim M \lesssim 10^{23}\, {\rm g}$ within which gravitational interactions would have been the dominant form of energy deposition to the medium. We also identify conditions under which
tidal forces from a transiting PBH could overcome the strong
nuclear force, either by dissociating deuterons, which would be relevant during big bang nucleosynthesis (BBN), or by inducing fission of heavy
nuclei. We find that gravitational dissociation of deuterons dominates photodissociation rates due to Hawking radiation for PBHs with masses $10^{14}\,{\rm g}\lesssim M \lesssim 10^{16}\,{\rm g}$. We additionally identify the phenomenon of gravitationally induced fission of heavy
nuclei via
tidal deformation.
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Cosmology and Nongalactic Astrophysics
Marked statistics across the cosmic web: Environmental dependent clustering in modified gravity simulations
Joaquin Armijo and Lucas Da Costa
We study environment-dependent clustering using the marked correlation function applied to Hu-Sawicki $f(R)$ modified
gravity simulations. This
gravity theory enriches the structure formation by enhancing
gravity in a scale-dependent form. By employing a multi-scale
cosmic structure finder
algorithm, we define the
cosmic environments divided in: nodes, filaments, walls and voids. We find a stronger impact of modified
gravity in nodes and filaments, which together dominate the information content by more than a factor of four relative to other environments. Combining environmental information further enhances the expected signal-to-noise ratio for CMASS- and DESI-like mock samples, particularly in configurations including filaments. Overall, marked correlation functions that incorporate environmental structure increase the information content by about a factor of two compared to standard density-based marks applied to the full
galaxy sample. These results demonstrate the importance of environmental information, especially from filaments, in improving the sensitivity of
galaxy clustering tests to deviations from GR in the $f(R)$ scenario.
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Earth and Planetary Astrophysics
On the orbital evolution of binaries with polar circumbinary disks
Cheng Chen, Philip J. Armitage and C. J. Nixon
Binaries occur in many astrophysical systems, from young protostellar binaries in
star forming regions to supermassive black hole binaries in
galaxy centers. In many cases, a circumbinary disk of gas forms around the binary with an orbit that may be misaligned to the binary plane. Misaligned disks around nearly circular binaries evolve into disks that are either aligned or counteraligned with the binary orbit. However, if the binary is sufficiently eccentric, then it can be more likely that the disk ends up in a polar-aligned configuration in which the disk angular momentum vector aligns with the binary eccentricity vector. We use Smoothed Particle Hydrodynamics simulations, evolved to an approximate steady state under mass injection, to determine the orbital
evolution of a binary with a polar-aligned disk for a range of binary-disk parameters. We find that, in all of the cases we have simulated, the binary shrinks with time. The decay rate is larger than for binaries surrounded by aligned or retrograde disks with matched disk parameters. The rate of shrinkage is largely unaltered by the size of the sink radii employed for the binary
stars, but for small enough sink radii some of the models exhibit long-lived polar circumprimary disks, which are continually fed mass from the circumbinary disk. We discuss our results in the contexts of
planet formation in young polar-aligned disks and merging supermassive black holes in
galaxy centers.
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Cosmology and Nongalactic Astrophysics · Cross-listed from hep-th
Mimetic Dark Matter from Inflation
Ali H. Chamseddine and Viatcheslav Mukhanov
We investigate the coupling of mimetic dark matter to the Gauss-Bonnet topological term in addition to the Einstein-
Hilbert action. We demonstrate that such interactions can naturally give rise to mimetic dark matter during the inflationary stage of the universe's
evolution. By choosing an appropriate coupling between the mimetic field and the Gauss-Bonnet term, we find that at the end of inflation, the correct amount of
dust-like dark matter is produced, with its energy density expressible in terms of the Hubble parameter at the end of inflation. Furthermore, depending on the form of the coupling, the post matter-radiation equality behavior of mimetic dark matter can experience slight modifications.
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Cosmology and Nongalactic Astrophysics · Cross-listed from hep-ph
Naturally small Dirac neutrino mass and $B-L$ dark matter
Ernest Ma, Partha Kumar Paul and Narendra Sahu
In the conventional gauged ${B-L}$ extension of the standard model, the $B-L$ charge of the singlet scalar $\chi$, responsible for the breaking of $U(1)_{B-L}$
symmetry, is taken to be 2 such that it can anchor type-I seesaw by giving Majorana masses to the right-handed
neutrinos, $\nu_R$. In this paper, we consider instead the cases $\chi \sim 3$ or 4 under $B-L$, so that $\nu_R$ may not acquire any Majorana mass and
neutrinos are Dirac
fermions. We then consider a vector-like
fermion $S$ with 2 units of $B-L$ charge, which becomes a good candidate for dark matter, either Dirac for $\chi \sim 3$ or Majorana for $\chi \sim 4$. In both cases, spontaneous $B-L$ breaking can induce a strong first-order phase transition, producing
stochastic gravitational waves (GW) which can be tested at GW experiments. Moreover, the presence of light $\nu_R$s gives rise to an additional contribution to the effective number of relativistic degrees of freedom, $\Delta{N}_{\rm eff}$, providing complementary constraints from current and upcoming CMB observations.
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Astrophysics of Galaxies
Evaluating star formation rates at z = 5
D. Ismail, K. Kraljic, M. Béthermin et al. (+11 more)
Inferring the
star formation rates (SFR) in high
redshift galaxies remains challenging, owing to observational limitations or uncertainties in calibration methods that link luminosities to SFRs. We utilize two state-of-the-art hydrodynamical simulations NewHorizon and NewCluster, post-processed with the radiative transfer code Skirt, to investigate the systematic uncertainties and biases in the inferred SFRs for z=5
galaxies; an epoch where
galaxies build-up their
stellar mass. We create synthetic observables for widely-used tracers: Halpha nebular line, [CII] 158 micron fine-structure line, total infrared (IR) continuum luminosity, and hybrid (IR + UV). We find that Halpha-inferred SFRs, time-averaged over 10 Myr, are sensitive to the choice of calibration and exhibit substantial scatter driven by
dust attenuation, viewing angle, and
dust-to-metal ratio. Adopting a steeper attenuation curve reduces this scatter significantly but does not fully eliminate systematic uncertainties. IR continuum-based SFRs trace intrinsic SFRs time-averaged over 100 Myr timescales when a well-sampled continuum emission between restframe 8 and 1000 micron is available and underestimate them with typical approaches when IR data are limited. Nevertheless, IR SFRs display a considerable scatter, largely due to UV
photon leakage and strong variations in the
star formation history. When UV data are available, hybrid (IR + UV) SFRs provide a more robust estimate, reducing scatter compared to IR-based SFRs while avoiding explicit attenuation corrections. Finally, we derive a [CII]-SFR relation finding a steeper relation than previous studies, however with significant scatter linked to gas density and
metallicity. Overall, IR-, hybrid-, and [CII]-based tracers remain more robust than Halpha against variations in optical depth.
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All authors D. Ismail, K. Kraljic, M. Béthermin, A. U. Kapoor, F. Renaud, C. Accard, J. Freundlich, Y. Dubois, S. Han, J.K. Jang, S. Jeon, T. Kimm, J. Rhee, S. Yi
Cosmology and Nongalactic Astrophysics · Cross-listed from cs.LG
GlueNN: gluing patchwise analytic solutions with neural networks
Doyoung Kim, Donghee Lee, Hye-Sung Lee et al. (+2 more)
In the analysis of complex physical systems, the objective often extends beyond merely computing a numerical solution to capturing the precise crossover between different regimes and extracting parameters containing meaningful information. However, standard numerical solvers and conventional deep learning approaches, such as Physics-Informed Neural Networks (PINNs), typically operate as black boxes that output solution fields without disentangling the solution into its interpretable constituent parts. In this work, we propose GlueNN, a physics-informed learning framework that decomposes the global solution into interpretable, patchwise analytic components. Rather than approximating the solution directly, GlueNN promotes the integration constants of local asymptotic expansions to learnable, scale-dependent coefficient functions. By constraining these coefficients with the differential equation, the network effectively performs regime transition, smoothly interpolating between asymptotic limits without requiring ad hoc boundary matching. We demonstrate that this coefficient-centric approach reproduces accurate global solutions in various examples and thus directly extracts physical information that is not explicitly available through standard numerical integration.
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All authors Doyoung Kim, Donghee Lee, Hye-Sung Lee, Jiheon Lee, Jaeok Yi
Astrophysics of Galaxies
Extragalactic archaeology through high-resolution integrated-light spectroscopy of globular clusters
M.A. Beasley, K. Fahrion, A. Gvozdenko et al. (+1 more)
We propose to radically expand the use of extragalactic globular clusters as tools for extragalactic archaeology. We propose a large-scale spectroscopic facility to obtain high spectral resolution (R $\sim$ 20,000) spectroscopy for a significant fraction of all globular clusters in the nearby Universe. This will facilitate the reconstruction of
galaxy assembly histories via chemical tagging, trace dark matter
haloes, and measure extragalactic distances.
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All authors M.A. Beasley, K. Fahrion, A. Gvozdenko, S. Larsen