Peer Revenue Fully funded

Papers

Fresh from arXiv, typeset properly. Highlighted words trade on the market.

Physics Astrophysics

astro-ph Watch Astrophysics

Tuesday 14 April

Earth and Planetary Astrophysics

Are Thalassa and Despina in Resonance Lock with Neptune's Oscillations?

Matija Ćuk, Harrison F. Agrusa, Marina Brozović et al. (+1 more)

The two innermost moons of Neptune, Naiad and Thalassa, are currently in a 73:69 mean-motion resonance. This resonance relies on the large inclination of Naiad, and we estimate that Naiad requires multiple Gyr to reach its $4.7^{\circ}$ inclination through this resonance. However, we find through direct numerical simulations that the current Naiad-Thalassa resonance is unstable on Myr timescales due to perturbations from the neighboring moon Despina. As this instability is a product of convergent tidal evolution predicted by equilibrium tidal theory, we propose that the innermost moons of Neptune may migrate through resonant-lock tides. If both Despina and Thalassa are locked to two resonant oscillations modes within Neptune, the frequencies of which evolve approximately in parallel, Naiad-Thalassa resonance can be stable for much longer. We find that Lindblad resonances with low-order $l=m=1$, $n=1$ g-modes at Neptune may be suitable candidates for driving the resonant-lock evolution of Thalassa and Despina, and possibly even Galatea.
Read the full abstract

All authors Matija Ćuk, Harrison F. Agrusa, Marina Brozović, Matthew M. Hedman

High Energy Astrophysical Phenomena

Radiation hydrodynamic simulations for the origin of quasi-periodic oscillations for accretion onto supermassive black holes

Yiyang Lin, Erlin Qiao, Jifeng Liu et al. (+2 more)

Quasi-periodic oscillation (QPO) has been detected in several accreting supermassive black hole (SMBH) systems, including active galactic nuclei (AGNs) and tidal disruption events (TDEs). However, despite that several models have been proposed, the physical origin of QPO is still unclear. In this paper, we performed radiation hydrodynamic simulations of accretion flow by injecting mass at a fixed radius, i.e. 10 Schwarzschild radius with different mass accretion rates, and setting the black hole (BH) mass to $10^7M_{\odot}$. We find that there are QPO signals by analyzing the mass inflow rates as a function of time from the simulations for different radii. The QPO frequencies from our simulations are well consistent with the radial epicyclic frequencies from analytic calculations for radius greater than a critical radius 3.8 Schwarzschild radius. This critical radius corresponds to the maximum epicyclic frequency, i.e. $\nu_{\rm r,max}$, in the radial direction. We proposed that $\nu_{\rm r,max}$ can be a good proxy for the observed QPO $\nu_{\rm QPO}$. Furthermore, assuming that our simulation results can be scaled to different BH masses $M_{\rm BH}$, we find that the theoretical relation of $\nu_{\rm r,max}$ as a function of $M_{\rm BH}$ can well match $\nu_{\rm QPO}$ as a function of $M_{\rm BH}$ for a sample of AGN and TDE. Finally, we discuss the effects of the BH mass, general relativity (GR), and other possible factors including the size of the mass injecting radius, viscosity and magnetic field on the simulation results.
Read the full abstract

All authors Yiyang Lin, Erlin Qiao, Jifeng Liu, Meng Guo, Zikun Lin

Astrophysics of Galaxies

Galactic Rain: Cool Gas Inflows in Red Geyser Galaxies and Their Connection to AGN Activity and Interactions

Arian Moghni, Namrata Roy, Timothy M. Heckman et al. (+3 more)

Red geysers are a population of massive (log[M/M$_\odot$]~10.5), quiescent galaxies that exhibit large-scale but weak, bi-symmetric ionized gas outflows, interpreted as signatures of ongoing, low-level active galactic nucleus (AGN) feedback. We investigate the kinematics and prevalence of cool (T~100-1000K), neutral gas traced by Na I D absorption, and its connection to galaxy environment and AGN activity. Using 140 red geyser galaxies from the Sloan Digital Sky Survey-IV Mapping Nearby Galaxies at Apache Point Observatory (MaNGA), we measure spatially resolved velocities and dispersions via double-Gaussian fits to the Na I D doublet. We find that ~70% of the cool gas is inflowing, with a median velocity of ~47 km/s (~10% of the expected free-fall speed), and also exhibits kinematically ordered motions with ${\sigma}_{NaD}$/${\sigma_*}$~0.4. Additionally, the Na I D absorption is more prevalent in red geysers than in a matched control sample, showing a higher detection fraction (63% vs 40%) and reservoir areas ~1.6 times larger. Acceleration (~1 Myr) and accretion (~20 Myr) timescales indicate that the absorbing clouds are likely young and short-lived. Another intriguing result is that radio-detected red geysers (30% of the sample) show inflowing gas reservoirs ~7 times larger than in non-radio systems. Similarly, galaxies subject to environmental effects host inflowing gas reservoirs ~2.7 times larger than isolated red geysers. We take this as evidence that galaxy interactions play a key role in replenishing the cool gas reservoirs of red geysers, fueling central AGN activity, sustaining radio emission, and regulating long-term quiescence. These findings reveal that quiescent systems are governed by cycles of inflow, feedback, and regulation.
Read the full abstract

All authors Arian Moghni, Namrata Roy, Timothy M. Heckman, Kevin Bundy, Kyle B. Westfall, Kate H. R. Rubin

High Energy Astrophysical Phenomena

The NuSTAR view of Ultra-Compact X-ray Binaries

A. Borghese, M. Armas Padilla and T. Muñoz-Darias

Ultra-compact X-ray binaries (UCXBs) are a subclass of low-mass X-ray binaries (LMXBs) characterised by tight orbits and hydrogen-poor donor stars. We present a spectral and timing study in the hard X-ray band of 11 of the 20 confirmed UCXBs, based on 37 archival NuSTAR observations. Using both X-ray colours and fractional root mean square values, we show that our sample spans the hard, soft, and intermediate X-ray states. Subsequently, we perform an X-ray spectral analysis using, when data allow it, the three-component model - an approach increasingly adopted for neutron star LMXBs. This work represents the largest LMXB sample analysed to date with this methodology. We focus on the properties of the X-ray continuum and report typical values for each X-ray state. Overall, UCXBs exhibit similar spectral properties to their longer-period counterparts, suggesting no major differences in the innermost regions of X-ray binaries, regardless of disc size or chemical composition. A possible exception is found in the soft-state sample, which shows Comptonisation fractions higher than those typically observed in regular LMXBs, although the statistics remain limited. Finally, we discuss the case of the slow X-ray pulsar 4U 1626-67, where we report the discovery of a very cold hard state with an electron temperature of ~6 keV - comparable to those usually observed in soft states of neutron-star LMXBs.
Read the full abstract

Cosmology and Nongalactic Astrophysics · Cross-listed from hep-ph

Searching for axions with quantum interferometry

Tanmay Kumar Poddar and Michael Spannowsky

Quantum phase measurements offer a complementary route to axion searches. We show that axion-photon interactions can imprint both Aharonov-Bohm (AB) and Berry phases in experimentally motivated quantum setups. For a coherently oscillating axion dark matter background, the induced effective current generates a time dependent magnetic flux in an rf-SQUID, leading to a measurable voltage signal through the Josephson phase. For representative benchmarks, this AB phase search reaches the minimum axion-photon coupling $g_{a\gamma\gamma}^{\mathrm{min}}\sim 7.8\times10^{-14}~\mathrm{GeV}^{-1}$ at axion mass $m_a\sim 10^{-10}~\mathrm{eV}$, with projected sensitivity that can improve on existing limits in that parameter space by roughly one to two orders of magnitude. We also identify a geometric phase observable in a Mach-Zehnder interferometer with an adiabatically rotating magnetic field, providing a proof-of-principle phase-based probe of meV-scale axions even when they do not constitute the dark matter, although sensitivity on the coupling remains weaker than current bounds with conservative tabletop benchmarks. Extending the analysis to a three level photon-axion quasiparticle (AQP)-axion system, with the AQP realized in a topological magnetic insulator, we find a potentially measurable THz Berry phase dominated by the AQP sector, furnishing a nontrivial validation of the formalism in a richer coupled system. These setups establish quantum phase observables as a useful new framework for axion searches, with immediate phenomenological promise in superconducting circuits and longer term potential in quantum enhanced interferometry.
Read the full abstract

Astrophysics of Galaxies

4MOST ChANGES: Catalog of high-redshift quasar candidates (4.5 < $z$ < 7) selected with SED fitting

T. Mkrtchyan, C. Mazzucchelli, R. J. Assef et al. (+12 more)

The identification of high-redshift quasars ($z > 4.5$) is critical for studying the early Universe, supermassive black hole growth, and cosmic reionization. Most known high-redshift quasars are located in the northern hemisphere, leaving the southern sky largely unexplored. As part of the 4-meter Multi-Object Spectroscopic Telescope (4MOST) and Chilean AGN/Galaxy Extragalactic Survey (ChANGES) S1604 survey, we aim to create a large catalog of high-redshift quasar candidates in the southern hemisphere using multiwavelength photometry and Spectral Energy Distribution (SED) fitting, with the goal of spectroscopic follow-up with 4MOST. We construct a multi-band photometric catalog by combining optical data from DELVE DR2 and DECaLS DR10, near-infrared data from VHS DR5 with an additional field of VIKING, mid-infrared data from AllWISE, and optical astrometry from Gaia DR3. After applying morphological and color-based cuts, we perform SED fitting using quasar and brown dwarf templates. Statistical outputs, including $\chi^2$, BIC, and F-test are used to rank and select candidates. Our final catalog contains 6104 high-redshift quasar candidates within $4.5 < z < 7$, with detections in 7 or more photometric bands satisfying our SED-based selection criteria (BIC > 0 and F-test > 10). Spectroscopic validation using NTT/EFOSC2 and Palomar/NGPS confirmed 3 high-redshift quasars at $z > 5$ out of 6 observed candidates.
Read the full abstract

All authors T. Mkrtchyan, C. Mazzucchelli, R. J. Assef, M. J. Temple, A. Rojas-Lilayú, F. E. Bauer, V. Toptun, J. A. Acevedo Barroso, S. Belladitta, E. P. Farina, L. N. Martínez-Ramírez, G. Papini, S. Satheesh-Sheeba, D. Stern, A. Upadhyayula

Solar and Stellar Astrophysics

Chromospheric dynamics and turbulence regulate the solar FIP effect

Andy S.H. To, J. Martin Laming, Jeffrey Reep et al. (+1 more)

Elemental abundance variations in the solar corona, commonly characterised by First Ionisation Potential (FIP) bias, provide crucial diagnostics of chromospheric processes. The ponderomotive force model, which attributes fractionation to Alfvén wave propagation, has successfully reproduced the observed fractionation patterns in various solar features. However, existing theoretical implementations rely on a static quiet Sun chromosphere, leaving the influence of chromospheric dynamics largely unexplored. We address this limitation by combining hydrodynamic simulations from HYDRAD with ponderomotive force calculations through FIPpy, a new open-source code. Comparing predictions between an initial VAL-C chromosphere and a heated chromosphere following impulsive nanoflare-like events, we show that the ponderomotive force model remains consistent under dynamic chromospheric conditions, while stronger changes in fractionation behaviour arise from variations in acoustic flux and turbulence. Most significantly, when acoustic wave flux drops below $\sim5\times10^6$ erg cm$^{-2}$ s$^{-1}$, mass-dependent thermal velocities dominate the fractionation process, producing counterintuitive patterns where Fe exceeds Ca in FIP bias, while high-FIP Ar shows fractionation. We demonstrate that any source of chromospheric turbulence will act to suppress fractionation. For flares, our results predict that the increased turbulence will suppress FIP bias, potentially explaining the observed abundance variations during flares. These findings suggest that coronal abundances and composition encode a sensitive balance between dominant mechanisms, determined by the ratio of ponderomotive acceleration to turbulent velocity.
Read the full abstract

All authors Andy S.H. To, J. Martin Laming, Jeffrey Reep, Adam J. Finley

Astrophysics of Galaxies

Targeted search for eccentric supermassive binary black holes in OJ 287 and nearby galaxy clusters with PPTA DR3

Shi-Yi Zhao, Xingjiang Zhu, Jacob Cardinal Tremblay et al. (+19 more)

We perform Bayesian targeted searches for continuous gravitational waves from eccentric supermassive binary black holes (SMBBHs) using the Parkes Pulsar Timing Array third data release (PPTA DR3). Six electromagnetically motivated sky directions are analyzed, including the blazar OJ~287 and five nearby galaxy clusters (Virgo, Fornax, Norma, Hercules, and Coma). No significant signals are found. For OJ 287, by explicitly incorporating orbital eccentricity (up to $e_0 = 0.8$) to robustly capture signal power spread across multiple harmonics, we constrain the total binary mass to $M_{\rm tot} < 5.25 \times 10^{10} M_{\odot}$ (95% credible level). We also place upper limits on the chirp mass of potential SMBBHs residing in galaxy clusters. By combining these limits with independent black hole mass estimates, we place novel constraints on the allowed binary mass ratios for potential hosts such as M87 and NGC~4889. Specifically, our results exclude binaries with mass ratios $q \gtrsim 10^{-2}$ at around 10 nHz for these massive systems, effectively ruling out equal-mass black hole mergers in the sampled parameter space. These findings demonstrate the growing power of pulsar timing arrays to probe SMBBH populations.
Read the full abstract

All authors Shi-Yi Zhao, Xingjiang Zhu, Jacob Cardinal Tremblay, Yiqin Chen, Małgorzata Curyło, Shi Dai, Valentina Di Marco, Pratyasha Gitika, George Hobbs, Simon C.-C. Ho, Xiao-Song Hu, Agastya Kapur, Wenhua Ling, Richard N. Manchester, Saurav Mishra, Daniel J. Reardon, Christopher J. Russell, Ryan M. Shannon, Sharon Mary Tomson, Jingbo Wang, Shuangqiang Wang, Andrew Zic

Astrophysics of Galaxies

Euclid: Quick Data Release (Q1) – Dual AGN in low-mass galaxies

M. Mezcua, B. Laloux, M. Scialpi et al. (+164 more)

Dual active galactic nuclei (AGNs) are expected in hierarchical galaxy evolution models, in which low-mass galaxies merge to build more massive ones. While observational evidence for dual AGNs is growing in massive galaxies, no clear detection has yet been found in the low-mass regime. We used photometry and spectroscopy from the first \Euclid Quick Data Release, combined with a collection of multi-wavelength data from the Dark Energy Spectroscopic Instrument (DESI), the LOw-Frequency ARray (LOFAR) high band antenna, and counterparts in X-ray and mid-infrared catalogues to identify dual AGNs at redshift $z \lesssim 1$. Focusing on low-mass galaxies with stellar masses below 10$^{10}$ M$_{\odot}$, we find nine dual AGN candidates with projected separations ranging from $\sim$20 to 51 kpc. We also find 49 dual AGN candidates in more massive galaxies. We derive a dual AGN fraction of 0.1% for the low-mass galaxies and estimate that these systems likely trace a population of progenitor black hole pairs that may evolve into bound binaries and eventually coalesce, emitting gravitational waves in the LISA band. These results constitute the first sample of spectroscopically confirmed dual AGN candidates in low-mass galaxies and have important implications for models in which supermassive black holes grow from lower-mass black holes located in low-mass galaxies, as well as for predictions of gravitational waves from low-mass binary black holes.
Read the full abstract

All authors M. Mezcua, B. Laloux, M. Scialpi, M. Siudek, A. Eróstegui, F. Ricci, T. Matamoro Zatarain, S. Visser, H. J. A. Rottgering, C. M. Gutierrez, A. Feltre, L. Bisigello, C. Saulder, L. Ulivi, J. H. Knapen, H. Domínguez Sánchez, G. Zamorani, K. Rubinur, J. Calhau, L. Spinoglio, F. Shankar, D. Stern, R. Pucha, A. Viitanen, B. Altieri, S. Andreon, N. Auricchio, M. Baldi, S. Bardelli, P. Battaglia, A. Biviano, M. Brescia, S. Camera, G. Cañas-Herrera, V. Capobianco, C. Carbone, J. Carretero, M. Castellano, G. Castignani, S. Cavuoti, K. C. Chambers, A. Cimatti, C. Colodro-Conde, G. Congedo, C. J. Conselice, L. Conversi, Y. Copin, F. Courbin, H. M. Courtois, M. Cropper, H. Degaudenzi, G. De Lucia, C. Dolding, H. Dole, F. Dubath, X. Dupac, M. Farina, R. Farinelli, F. Faustini, S. Ferriol, M. Frailis, E. Franceschi, M. Fumana, S. Galeotta, K. George, B. Gillis, C. Giocoli, J. Gracia-Carpio, A. Grazian, F. Grupp, S. V. H. Haugan, J. Hoar, H. Hoekstra, W. Holmes, I. M. Hook, F. Hormuth, A. Hornstrup, K. Jahnke, M. Jhabvala, S. Kermiche, B. Kubik, M. Kümmel, M. Kunz, H. Kurki-Suonio, A. M. C. Le Brun, S. Ligori, P. B. Lilje, V. Lindholm, I. Lloro, G. Mainetti, D. Maino, E. Maiorano, O. Mansutti, O. Marggraf, M. Martinelli, N. Martinet, F. Marulli, R. J. Massey, E. Medinaceli, S. Mei, Y. Mellier, M. Meneghetti, E. Merlin, G. Meylan, A. Mora, M. Moresco, L. Moscardini, C. Neissner, R. C. Nichol, S.-M. Niemi, C. Padilla, S. Paltani, F. Pasian, K. Pedersen, W. J. Percival, V. Pettorino, S. Pires, G. Polenta, M. Poncet, L. A. Popa, L. Pozzetti, F. Raison, A. Renzi, J. Rhodes, G. Riccio, E. Romelli, M. Roncarelli, E. Rossetti, B. Rusholme, R. Saglia, Z. Sakr, D. Sapone, B. Sartoris, M. Sauvage, M. Schirmer, P. Schneider, A. Secroun, G. Seidel, S. Serrano, E. Sihvola, P. Simon, C. Sirignano, G. Sirri, L. Stanco, J. Steinwagner, P. Tallada-Crespí, A. N. Taylor, I. Tereno, N. Tessore, S. Toft, R. Toledo-Moreo, F. Torradeflot, I. Tutusaus, L. Valenziano, J. Valiviita, T. Vassallo, Y. Wang, J. Weller, A. Zacchei, F. M. Zerbi, I. A. Zinchenko, E. Zucca, J. García-Bellido, M. Huertas-Company, J. Macias-Perez, J. Martín-Fleitas, V. Scottez

Earth and Planetary Astrophysics

The Identification of CS2 and Evidence for Carbon-Sulfur Chemical Coupling in a Warm Giant Exoplanet Atmosphere

Anastasia Triantafillides, Thomas G. Beatty, Matthew C. Nixon et al. (+14 more)

Transmission spectroscopy with the James Webb Space Telescope (JWST) is revealing growing chemical complexity in giant exoplanet atmospheres. Of particular interest is sulfur, which had essentially no observational constraints before JWST. Recent work has shown that a planet's atmospheric sulfur content traces its refractory budget and is therefore a sensitive indicator of formation pathways. But despite the growing library of JWST data, the sulfur inventory of giant exoplanets remains poorly constrained: sulfur-bearing species are governed by disequilibrium chemistry and by kinetic networks that are still being revised. Here we present a transmission spectrum of the warm giant planet WASP-80 b obtained with JWST/NIRCam and MIRI over 2.4 $\mu$m–10$\mu$m in three transits. We uniquely identify CS$_2$ in our transmission spectrum using the combination of the two absorption features in NIRCam and MIRI at a significance of $\ln (B)=17.89$ ($\sigma = 6.3$). Our grid-based retrievals yield $\mathrm{[M/H] = \:} 0.54^{+0.17}_{-0.12}$ and $\mathrm{C/O =\:}0.43^{+0.12}_{-0.08}$ which result in $\log(\mathrm{X_{CS_2}})$ abundances of $\sim-4.5$. The latest carbon-sulfur kinetics networks produce substantially greater amounts of CS$_2$ than past works, enabling good fits ($\chi^2/\mathrm{N_{data}}\sim1.2$) to the data without invoking extreme abundance patterns. These results identify CS$_2$ as an observable tracer of sulfur disequilibrium chemistry and provide observational support for theoretically predicted carbon-sulfur chemical coupling in giant exoplanet atmospheres.
Read the full abstract

All authors Anastasia Triantafillides, Thomas G. Beatty, Matthew C. Nixon, Taylor J. Bell, Everett Schlawin, Luis Welbanks, Thomas P. Greene, Melinda Soares-Furtado, Jonathan J. Fortney, Michael R. Line, Nishil Mehta, Sagnick Mukherjee, Matthew M. Murphy, Kazumasa Ohno, Vivien Parmentier, Yoav Rotman, Lindsey S. Wiser

Solar and Stellar Astrophysics

Solar photospheric spectrum microvariability III. Radial velocities and line profiles in magnetic active-region granulation

Dainis Dravins, Hans-Günter Ludwig, Matthias Steffen et al. (+2 more)

Finding low-mass planets around solar-type stars requires to understand the physical variability of the host star, which greatly exceeds the planet-induced radial-velocity modulation. Different solar photospheric absorption lines have slightly disparate responses to stellar activity, which should permit to disentangle wavelength shifts induced by exoplanets from those originating in stellar atmospheres. Changing area coverage of magnetic active-region granulation (faculae and plage) causes radial-velocity fluctuations of the disk-integrated solar spectrum, whose precise modeling requires active-region spectral line profiles. Hydrodynamic 3D modeling of granulation in magnetic fields extends previous non-magnetic studies, revealing different line profiles and altered convective velocity shifts. Different types of lines in the visual and near infrared are examined in synthetic hyper-high resolution spectra (R~900,000), comparing non-magnetic areas with those with strongly magnetic (240 mT = 2400 G) granulation. Magnetic fields inhibit convective motions, decrease the energy flow, produce more symmetric lines, and remove the common blueshift with its familiar C-shape bisectors. Unexpectedly, magnetic granulation displays convective redshifts. Their origin is traced to contributions from small areas, where hot and bright down-moving elements are created through shocks and adiabatic compression when rising gas is forced over into magnetically channeled downflows. Understanding line formation in also stellar active regions is needed to simulate full-disk spectra toward exoEarth detections. Detailed shapes of spectral lines carry significant information, suggesting that hyper-high spectral resolution may ultimately be required
Read the full abstract

All authors Dainis Dravins, Hans-Günter Ludwig, Matthias Steffen, Carlos Allende Prieto, Lars Koesterke

Astrophysics of Galaxies

Investigating the Circumgalactic Medium through Mg II absorption coincidence

Paryag Sharma, Raghunathan Srianand, Hum Chand et al. (+1 more)

We present a statistical measurement of the transverse coherence of Mg II $\lambda\lambda2796,2803$ absorption using a large sample of 9204 absorber-centric quasar sightline pairs from the Sloan Digital Sky Survey. We quantify the probability that an Mg II absorber detected along one sightline is also present along a nearby sightline, and measure how this coincidence probability varies with projected separation from $\sim$50 kpc to $\sim$1 Mpc. The resulting coincidence curve exhibits a clear two-regime structure: the coincidence probability rises steeply to $\sim$5-8% at separations below $\sim$100 kpc, but declines rapidly beyond this scale and settles into a low plateau of $\sim$1–2% out to $\sim$1 Mpc. A simple geometrical single-halo model reproduces the enhanced probability at $\lesssim$100 kpc, while the large-scale plateau is well explained by the expected contribution from galaxy clustering, confirmed using both photometric galaxy counts and the two-point correlation function. A complementary stacking analysis reveals a significant excess in Mg II equivalent width in paired sightlines lacking individual detections, implying a coherence scale of $\sim$100-200 kpc for the cool, metal-enriched CGM. Together, these results identify the transition from a halo-dominated coherence regime at small separations to a clustering-dominated regime at large scales, bridging the gap between small-scale lensing constraints and megaparsec-scale absorber clustering studies.
Read the full abstract

All authors Paryag Sharma, Raghunathan Srianand, Hum Chand, Labanya Kumar Guha

Astrophysics of Galaxies

Resolving circumgalactic gas flows around a z$\approx$3.6 quasar using MUSE and ALMA

M. Galbiati, A. Pensabene, S. Cantalupo et al. (+10 more)

The formation and evolution of galaxies is regulated by the exchange of gas with the surrounding large-scale structures on circum- and intergalactic scales. Yet, little is known about the complex processes shaping the cycle of baryons in and out of galaxies. In this work, we present a multiline study of the gas surrounding a $z\approx3.66$ quasar known to host one of the brightest Ly$\alpha$ nebulae at high redshift, MUSE Quasar Nebula 04 (MQN04). By combining a high-resolution MUSE detection of non-resonant HeII emission with a precise measurement of the redshift of the quasar host via the ALMA CO(4-3) line, we study the kinematics of the cool ionized gas down to $\approx1\rm\,kpc$ from the quasar. The MUSE observations reveal complex clumpy structures as well as diffuse emission extended over $\approx100\,{\rm kpc}$ and blueshifted by $\approx 0-800\,{\rm km\,s^{-1}}$ relative to the quasar systemic redshift, suggesting that the circumgalactic medium is highly asymmetric. The analysis of the HeII/Ly$\alpha$ line ratio, and the presence of a low-column density ($\approx10^{14.6}~\rm cm^{-2}$) HI absorber along the quasar sightline suggests that MQN04 resides in a highly ionized medium. This is also supported by the gas kinematics, which, except in the most central region, shows consistent velocity shifts across the different tracers, indicative of relatively weak radiative transfer effects. Based on its morphology and kinematics, we conclude that the extended HeII emission may arise from merger-driven tidal stripping or inflows of gas illuminated by the quasar radiation. On comoving megaparsec scales, we discover a large concentration ($\delta\approx41$) of star-forming galaxies lying within $|\Delta v_{\rm QSO}| \leq1000\rm\,km\,s^{-1}$ from the quasar. MQN04 is therefore one of the most overdense environments discovered at this epoch.
Read the full abstract

All authors M. Galbiati, A. Pensabene, S. Cantalupo, A. Travascio, G. Pezzulli, R. Decarli, R. Dutta, S. Muzahid, J. Schaye, T. Lazeyras, N. Ledos, G. Quadri, W. Wang

Astrophysics of Galaxies

A Dynamical Test for Cooling-Induced Entrainment in a Runaway Supermassive Black Hole Tail

Ish Kaul and S. Peng Oh

Radiative turbulent mixing layers are widely invoked to explain the survival, growth, and entrainment of cold gas in hot astrophysical flows, but quantitative dynamical tests have remained scarce. RBH-1, the first confirmed runaway supermassive black hole, offers a rare opportunity to test this framework: JWST observations show a 62 kpc tail of cold H$\alpha$ and [O III]-emitting gas behind a source moving at ~950 km/s through the hot circumgalactic medium, with a coherent velocity gradient of ~200 km/s along the tail. Using 3D hydrodynamical simulations together with turbulent mixing-layer theory, we model the coherent downstream tail. We find that the observed downstream deceleration is well reproduced by accretion-induced drag from radiative mixing layers, and that without radiative cooling no coherent cold tail forms. We also derive a direct connection between the tail deceleration and the cooling luminosity, yielding predictions for future measurements of the cooling luminosity profile. RBH-1 therefore provides a rare quantitative dynamical stress test of radiative mixing-layer physics in an astrophysical system.
Read the full abstract

Astrophysics of Galaxies

From Clumps to Sheets: Geometry Controls the Temperature PDF of Multi-Phase Gas

Zirui Chen and S. Peng Oh

Temperature probability distribution functions (PDFs) are a compact description of the thermal structure of multi-phase turbulent gas, and are directly linked to observables such as emission/absorption line ratios and phase mass fractions. In the circumgalactic medium (CGM) literature, temperature PDFs are often interpreted using planar turbulent radiative mixing layers, for which analytic models successfully reproduce the simulated temperature structure. These PDFs are assumed to be universal. By contrast, studies of the multiphase interstellar medium (ISM) typically use turbulent-box simulations, which produce broad PDFs but lack a clear theoretical interpretation. Using 3D hydrodynamic simulations under both ISM and CGM conditions, we compare planar mixing layers with turbulent-box simulations under identical microphysical conditions. Despite identical cooling and turbulent driving, the resulting temperature PDFs differ substantially. The missing ingredient is geometry. We demonstrate that the temperature PDF can be decomposed into the product of the area of temperature isosurfaces and the thickness of the corresponding temperature layers. The thickness is controlled primarily by microphysics, such as radiative cooling and thermal conduction, and is well captured by existing mixing-layer models. The isosurface area, however, is set by morphology. In mixing layers it remains sheet-like, whereas in turbulent media cold gas forms clumps whose interfaces expand with temperature and eventually percolate into connected sheets. This geometric transition produces broad PDFs with large intermediate-temperature mass fractions. These results have implications for long-standing puzzles such as thermally unstable gas in the ISM, the large OVI reservoir in the CGM, and X-ray-H$\alpha$ correlations in jellyfish tails.
Read the full abstract

Astrophysics of Galaxies

Persephone's Torch: A 15th Magnitude Quadruply-Lensed Quasar From the Couch Discovered with SPHEREx and the LBT

Frederick B. Davies, Eduardo Bañados, Sarah E. I. Bosman et al. (+4 more)

Here we report the spectroscopic and geometric confirmation of an extremely bright ($i=14.77$) and compact (Einstein radius of $\sim0.45''$) quadruply-lensed quasar at $z=2.22$, J1330$-$0905, which we dub Persephone's Torch. The system had been previously selected as a candidate lensed quasar based on large-area survey data; here we confirm its quasar nature and redshift using public spectrophotometry from the SPHEREx mission, a.k.a. "from the couch". Adaptive optics imaging with LBT/LUCI resolves four images in a "circular kite" configuration. The system is the brightest gravitationally-lensed quasar system ever found. While an elliptical power-law mass distribution plus external shear accurately reproduces the locations of the images and lensing galaxy, and predicts a total magnification of $\sim56$, the brightnesses of the lensed images present highly anomalous flux ratios. Together with short time delays between images ($\leq 2$ days), this makes Persephone's Torch a promising candidate for future microlensing studies. Our discovery highlights the potential of SPHEREx full-sky infrared spectrophotometry to uncover extraordinarily bright objects that have otherwise been overlooked.
Read the full abstract

All authors Frederick B. Davies, Eduardo Bañados, Sarah E. I. Bosman, Arpita Ganguly, Silvia Belladitta, Jennifer Power, Jon Rees

Instrumentation and Methods for Astrophysics

Secular Brightness Trends of Starlink and OneWeb Satellites

Anthony Mallama

Magnitudes recorded from 2021 through 2026 for Starlink VisorSats reveal brightening of 0.6 magnitudes, while those of OneWeb show dimming of 0.4. Both trends are significant at 3 sigma. This study is based on 1.6 million magnitudes recorded by the MMT9 robotic observatory.

Earth and Planetary Astrophysics

The Material Point Method (MPM) for simulating hypervelocity impact on asteroids

Xiaoran Yan, Patrick Michel, Ruichen Ni et al. (+2 more)

Shock-physics numerical codes are essential tools for describing the short but extreme fragmentation stage of the hypervelocity impact process on asteroids. However, accurately representing complex interior structures, surfaces, and contact mechanics in these events remains a significant challenge for traditional hydrocodes. This study introduces and validates an innovative yet underutilized technique, i.e., the Material Point Method (MPM), to simulate hyper-velocity impacts on asteroids. This approach offers new perspectives and solutions for capturing complex interfaces and handling the contact and boundary conditions in asteroid impact simulations. Our MPM implementation incorporates critical improvements to material models, including a pressure-dependent C^1 continuous yield criterion with quantifiable plastic strain, and a resolution-independent Grady-Kipp fragmentation model, to capture the complex physics of geological materials under extreme conditions. The framework is rigorously validated against laboratory impact experiments and benchmarked with smoothed particle hydrodynamics (SPH) simulations, confirming its robustness and precision. Crucially, when applied to asteroid-scale collisions, our model successfully reproduces the formation of large, coherent fragments analogous to (433) Eros. This work establishes MPM as a validated and powerful extension to the planetary scientist's toolkit, enabling the expansion of the parameter space and the treatment of complex contact and boundary conditions, which will enable more realistic simulations of asteroid evolution, family formation, and planetary defense scenarios.
Read the full abstract

All authors Xiaoran Yan, Patrick Michel, Ruichen Ni, Yifei Jiao, Junfeng Li

Astrophysics of Galaxies

Obscured at the Core: Evidence for Nuclear Dust in Reddened Type-1 AGN

Miguel A. Montalvo Hernandez, Andy D. Goulding and Jenny E. Greene

Reddened Type-1 quasars offer a unique window into the structure and evolution of active galactic nuclei (AGN), yet their physical origin and the source of their reddening remain uncertain. Optical surveys often miss these dust-obscured objects, resulting in an incomplete view of the quasar population. In this work, we construct a sample of 6,600 Type-1 quasars at redshifts $0.5 \leq z \leq 1.2$ by combining deep optical imaging from HSC with mid-infrared photometry from WISE, enabling a more complete selection that is not biased against reddened objects. We perform detailed SED modeling using the CIGALE code, enhanced by synthetic photometry derived from SDSS spectra to better constrain the optical continuum. We classify quasars into blue and reddened Type-1 populations based on their continuum slopes and compare their SEDs and emission line properties. As expected from this definition, reddened Type-1 AGN show higher dust extinction, with a median $A_V = 0.60^{+0.32}_{-0.19}$ mag, compared to $A_V = 0.06^{+0.10}_{-0.03}$ mag for blue objects. But they also exhibit smaller torus half-opening angles, with a median of $25.7^{+10.1}_{-8.7}$ deg, compared to $33.3^{+11.1}_{-5.9}$ deg for blue objects. While such extinction could arise on either galaxy or nuclear scales, the systematically stronger narrow-line equivalent widths and weaker Balmer broad lines in reddened Type-1s indicate that the obscuration acts on nuclear scales, likely from dust concentrated near the polar axis. We discuss the possibility that these structural differences may be linked to a sub-pc outflow, that carries dusty gas into the polar region and evacuates the torus region.
Read the full abstract

Earth and Planetary Astrophysics

Reassessing planetary composition: Evidence of rock-dominated envelopes in Uranus and Neptune

Vanesa Ramirez, Yamila Miguel and Saburo Howard

Although Uranus and Neptune are commonly classified as ice giants, their exact compositions remain poorly constrained. Recent studies of outer Solar System bodies challenge the traditional view that these planets are primarily ice-dominated, suggesting that refractory material plays a more significant role. Determining the proportions of ice and rock within Uranus and Neptune is essential for understanding their formation and the evolutionary history of the Solar System. In this work we computed interior structure models for both planets and explored, within a Bayesian framework, the range of compositions that satisfy the available observational constraints. We quantified the resulting ice and rock fractions and analyzed their impact on the inferred internal structure. Our results suggest that the envelopes of both Uranus and Neptune are systematically enriched in refractory material, with median rock fractions of approximately 60% within the heavy-element component, similar to Pluto, Kuiper belt objects, and comets. In contrast, the deep interiors of the two planets exhibit distinct compositions: Neptune is best fit by relatively rock-rich mantles (median rock fraction of ~ 55%), whereas Uranus is inferred to have more ice-rich mantles (median rock fraction of ~ 41%), consistent with a more strongly stratified structure. These results point to compositional differences between Uranus and Neptune that may reflect divergent formation and evolutionary pathways.
Read the full abstract

Cosmology and Nongalactic Astrophysics

Probing scalar-tensor-induced gravitational waves in the nHz band: NANOGrav and SKA

William Iania and Angelo Ricciardone

Scalar-induced gravitational waves (SIGWs) have recently attracted considerable interest, both as a possible explanation for the nanohertz signal reported by the Pulsar Timing Array (PTA) collaboration and for their connection with primordial black hole (PBH) physics. In addition to SIGWs, scalar-tensor-induced gravitational waves (STGWs) have emerged as a promising cosmological source of the stochastic gravitational wave background (SGWB). In this paper, we compute the STGWs generated during a generic matter-dominated (MD) era, as well as during an early matter-dominated (eMD) epoch followed by a sudden transition to the standard radiation-dominated (RD) stage, working in the Poisson gauge. We find that, in a purely MD age, the corresponding energy density rapidly dilutes, whereas in the presence of an eMD phase it remains non-vanishing due to the short duration of the eMD period. We then investigate whether the STGW signal could provide a dominant contribution to the NANOGrav 15-year dataset and we forecast the prospects for its detection with future observations by the Square Kilometre Array (SKA). In particular, we consider STGWs generated during both eMD and RD eras, including their linear-order contributions. We further inject the scalar-induced contribution, both as an additional component and as the only signal, and compare the spectra against the same datasets. Our results show that, although the SIGWs still appear to provide the dominant contribution and the posteriors are tightly constrained by the requirement of avoiding PBH overproduction, the GWs induced by scalar-tensor mixing constitute a viable target for future, more sensitive nano-Hz detectors of the SGWB.
Read the full abstract

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

Cosmologically viable non-polynomial quasi-topological gravity: explicit models, $\Lambda$CDM limit and observational constraints

Emmanuel N. Saridakis

We investigate the cosmological implications of non-polynomial quasi-topological gravity (NPQTG), a novel class of modified gravitational theories in which the background dynamics is encoded in a single function of the Hubble parameter. This framework provides a minimal and theoretically consistent extension of general relativity, incorporating higher-curvature effects while preserving second-order field equations and avoiding higher-derivative instabilities. We first establish the general conditions for cosmological viability and construct explicit realizations, including polynomial, quartic, power-law and non-polynomial models, demonstrating how different functional forms lead to distinct expansion histories. Focusing on the quartic and power-law cases, we show that the resulting cosmological evolution reproduces the standard thermal history of the Universe and gives rise to an effective dark-energy sector of geometric origin, with dynamical equation-of-state behavior that can lie in the quintessence or phantom regime. We then confront the models with observational data from Type Ia Supernovae, Cosmic Chronometers, and Baryon Acoustic Oscillations, using a Bayesian MCMC analysis. We find that both models provide an excellent fit to the data, remaining fully compatible with current constraints and statistically competitive with $\Lambda$CDM. Our results demonstrate that NPQTG offers a simple and efficient framework for describing late-time cosmic acceleration with dynamical dark energy, while maintaining theoretical consistency and observational viability.
Read the full abstract

Astrophysics of Galaxies

How I Wonder What You Are – JWST's Little Red Dots do not TWINKLE

Zhaoran Liu, Rohan P. Naidu, Amy Secunda et al. (+20 more)

Little Red Dots (LRDs) are a population of compact, red sources that have emerged as one of the most puzzling findings of JWST. Variability provides a direct probe of their central engines. Here we present the first joint spectroscopic and photometric time-domain study of LRDs undertaken with the JWST TWINKLE slitless spectroscopy program. Surveying the FRESCO GOODS-North legacy field, TWINKLE monitors a complete, H$\alpha$-flux-limited sample of 18 LRDs at z = 3.9-6.8, achieving a rest-frame baseline of $\sim$140-220 days. We detect no variability in photometry, H$\alpha$ line flux, or line shape across the sample. If LRDs resembled AGN in reverberation mapping samples – the foundation for black hole mass calibrations and luminosity scaling relations – we would expect >10 sources to show measurable fluctuations. Observing none implies a 5.9$\sigma$ deficit. The non-detections hold across all broad H$\alpha$ emitters within TWINKLE's field of view – the 18 V-shaped LRDs as well as 9 non-LRDs. Comparison with simulated light curves disfavors sub-Eddington accretion and is instead consistent with super-Eddington accretion, other mechanisms that suppress variability, or perhaps no AGN whatsoever. If LRDs do harbor black holes, calibrations derived from sub-Eddington systems may not apply, thereby explaining JWST's apparently "overmassive" black holes. These observations provide unique constraints on the physics of one of the most enigmatic populations discovered by JWST.
Read the full abstract

All authors Zhaoran Liu, Rohan P. Naidu, Amy Secunda, Jenny E. Greene, Jorryt Matthee, John Chisholm, Anna de Graaff, Luke Robbins, Jacqueline Antwi-Danso, Gabriel Brammer, Wendy Q. Sun, Anna-Christina Eilers, Seiji Fujimoto, Lukas J. Furtak, Erin Kara, Vasily Kokorev, Danilo Marchesini, Pascal A. Oesch, Justin D. R. Pierel, Xuejian Shen, Robert A. Simcoe, Alberto Torralba, Mark Vogelsberger

High Energy Astrophysical Phenomena

High-energy Processes in the Bubbles of Wolf-Rayet Stars: The case of WR 102

L. Espinosa and M. V. del Valle

Supersonic winds from massive stars carry great amounts of kinetic power and modify the surrounding interstellar medium. Through this interaction a stellar bubble is formed. Theoretical studies and recent observations suggest that the winds of massive stars could be sources of Galactic cosmic rays. The first detection of synchrotron emission from the bubble of a single star was reported, indicating the presence of relativistic electrons. Studying the non-thermal emission from a single massive star can help to better understand the acceleration of particles taking place in massive star clusters. WR 102 is the perfect case of study. In this work, we present the first high-energy model for the bubble of WR 102: G2.4+1.4. We aim at fitting the radio data and predicting gamma-ray emission. We assume that both electrons and protons are accelerated at the wind shock. We applied a classical model for the stellar bubble and adopted a one-zone model for estimating the radiation produced by the relativistic particles near the acceleration region. Additionally, we computed the expected emission from the protons that diffuse to the outer regions of the bubble. Also, we estimated the leptonic and hadronic contributions expected from cosmic rays. We fitted the observations considering that 3% of the wind kinetic power goes into relativistic electrons, and a magnetic field of 250 $\mu$G. The dominant component at high energies is produced by locally accelerated protons reaching the shell. Protons might reach PeV energies in the wind bubble, but the predicted gamma-ray flux is too low to be detectable.
Read the full abstract

Cosmology and Nongalactic Astrophysics

Do equation of state parametrizations of dark energy faithfully capture the dynamics of the late universe?

Özgür Akarsu, Maria Caruana, Konstantinos F. Dialektopoulos et al. (+3 more)

We investigate how strongly late-time inferences about DE dynamics depend on the functional prior used to represent the expansion history. Using identical late-time combinations of CC, DESI BAO measurements, the Pantheon+ SN1a sample, and the H0DN prior, we compare a node-based reconstruction of the reduced Hubble function $E(z)$ with a representative family of smooth low-dimensional DE EoS parametrizations, including CPL. Over the redshift range constrained by the data, both approaches yield consistent $H(z)$, and, in the absence of H0DN, compatible values of $H_0$. However, a clear method dependence emerges at intermediate redshift ($z\sim1.7$): the reconstruction favors stronger deceleration, $q_{\rm Rec}(1.7)\simeq0.56-0.61$, whereas the smooth parametrizations cluster at $q(1.7)\simeq0.32-0.40$, implying a persistent $\sim2-3\sigma$ discrepancy across dataset combinations and parametrizations. For the EoS-based parametrizations, whose effective DE densities remain positive by construction, the preferred $w_{\rm DE}(1.7)<-1$ values correspond to NECB-violating (phantom-like) behaviour, but this is a less robust discriminator as $w_{\rm DE}$ becomes ill-conditioned as $\rho_{\rm DE}\to0$. In the effective-fluid mapping, the reconstruction accommodates the same late-time kinematical preference through a rapid descent of $\rho_{\rm DE}(z)$ toward very small values and a sign change, whereas the EoS-based parametrizations absorb it through smoother, and in several cases NECB-violating, evolution over $z\sim1-2$. Although the reconstruction improves the best-fit likelihood, especially with H0DN, Bayesian evidence continues to favor the simpler parametric descriptions. Our results isolate $z\sim1.5-2$ as the key window in which EoS-based DE parametrizations can compress localized kinematic structure and associated features of DE that are still permitted by current late-time data.
Read the full abstract

All authors Özgür Akarsu, Maria Caruana, Konstantinos F. Dialektopoulos, Luis A. Escamilla, Emre O. Kahya, Jackson Levi Said

Cosmology and Nongalactic Astrophysics

Revisiting the angular size-redshift cosmological test with milliarcsecond radio structures in active galactic nuclei

Mina Ghodsi Yengejeh, Tatiana A. Koryukova, Leonid I. Gurvits et al. (+5 more)

VLBI measurements of the sizes of compact extragalactic radio sources, jetted active galactic nuclei, provide data for probing the angular size–redshift relation, offering a complementary test to other distance–redshift methods. We analyse a significantly expanded dataset to reassess the angular size–redshift relation and its potential for constraining cosmological model parameters, focusing on the matter density parameter $\Omega_{\mathrm{m}}$ in a flat $\Lambda$ Cold Dark Matter Universe. This is the first major update of the compact-source angular size test in the past quarter of a century, using a dataset an order of magnitude larger than in previous studies. MCMC analysis on real data and on multiple mock catalogues to evaluate parameter constraints in the presence of observational scatter. In addition, we conducted a test with 100 randomized catalogues created by shuffling redshifts while preserving other observables. We also explored how astrophysical parameters depend on fixed cosmological models with different $\Omega_{\mathrm{m}}$ values. The randomization test showed that the posterior distributions from randomized data do not overlap with those from real observations, confirming that the measured angular size–redshift relation is physically meaningful. The astrophysical model parameter that describes the redshift dependence of the source angular size exhibits degeneracy with $\Omega_{\mathrm{m}}$. Simulated mock catalogues indicate that the method is able to constrain $\Omega_{\mathrm{m}}$ if the data scatter is below $\sim20\%$. Scaling estimates suggest that high-quality data of samples of several thousands to $\sim 100\,000$ sources, a standardisation calibration approach, and/or refining sample selection criteria are needed to fully exploit the potential of the angular size–redshift test with this type of objects (abridged).
Read the full abstract

All authors Mina Ghodsi Yengejeh, Tatiana A. Koryukova, Leonid I. Gurvits, Sándor Frey, Alexander B. Pushkarev, Alexander V. Plavin, Kenneth I. Kellermann, András Kovács

Cosmology and Nongalactic Astrophysics · Cross-listed from hep-th

Infrared Spectral Gap in a Gluonic Dark Sector and the Galactic Acceleration Scale

Gilles Cohen-Tannoudji, Jean-Pierre Gazeau, Hamed Pejhan et al. (+1 more)

We further develop a trace-anomaly-motivated gluonic scenario in which cold dark matter (CDM) is modeled as a long-lived color-singlet Bose-Einstein condensate seeded at the QCD confinement transition. Specifically, guided by the near-universality of the galactic acceleration scale $g^{}_\dagger \simeq (1\text{--}2)\times10^{-10}\,\mathrm{m\,s^{-2}}$ inferred from the RAR, we hypothesize that this relic gluonic condensate organizes, at galactic distances, into a spectrally rigid lowest-weight structure characterized by a protected infrared gap. Within an effective representation-theoretic framework, Lorentz covariance together with positive-energy lowest-weight unitarity naturally favors the AdS algebra $\mathfrak{so}(2,3)$ as the minimal algebraic structure supporting such a discrete tower of states. The resulting condensate produces, by construction, a cored halo profile with finite total mass $M_h$. Normalizing this profile by the observed approximate universality of the central DM surface density, $\Sigma_0\simeq141\,M_\odot\,\mathrm{pc}^{-2}$, yields a universal characteristic acceleration $g^{}_\star ={G\, M_h}/{r_{\rm c}^2} \simeq \pi^2 G\,\Sigma_0 \simeq 1.9\times10^{-10}\,\mathrm{m\,s^{-2}}$, independent of the particular halo scale; since $\Sigma_0$ fixes the final expression, the dependence on the collective correlation length $r_{\rm c}$ drops out. Notably, its predicted value lies well within the empirical range of the acceleration scale inferred from the RAR. We also provide an illustrative comparison with representative rotation curves from the SPARC database, indicating phenomenological compatibility of the finite-mass profile with realistic baryonic decompositions. This comparison is not a precision fit to the full SPARC sample, and the agreement with the RAR scale should not be interpreted as a first-principles derivation of the RAR itself.
Read the full abstract

All authors Gilles Cohen-Tannoudji, Jean-Pierre Gazeau, Hamed Pejhan, Jean-Pierre Treuil

2604.12910 · 14 Apr · 17 pages, 8 figures - Substantially revised version. Title, abstract, introduction, and discussion rewritten; finite-mass halo sector clarified; connection to the central dark-matter surface-density scale and the RAR acceleration scale made explicit; new section added with representative SPARC rotation-curve comparisons; claims about the RAR and AdS interpretation softened and clarified

Abstract PDF $GALAC ×3$HALO ×2$ALGB ×1

Solar and Stellar Astrophysics

The $R$-Process Alliance: Actinide Abundances, Variation, and Evolution in Metal-Poor Stars

Shivani P. Shah, Rana Ezzeddine, Erika M. Holmbeck et al. (+11 more)

The actinides, including thorium (Th), are the heaviest observable elements synthesized in the universe, holding clues to the extremes of the astrophysical and nuclear conditions of $r$-process sites. We present Th abundances based on high-resolution spectroscopy for 47 metal-poor stars, the largest homogeneously analyzed sample to date. The chemical evolution of Th exhibits a decrease in dispersion in [Th/H] and [Th/Fe] from $\sim$0.6 dex at the lowest metallicities to $\sim$0.2 dex at higher metallicities. We also find that Th and the lanthanides Eu and Dy are co-produced remarkably well, with average [Th/Eu]$\sim0.0$ across $-3.0 \lesssim$ [Fe/H] $\lesssim -1.5$, as well as across stars with $0.0\lesssim$ [Eu/Fe] $\lesssim2.5$. Even so, the absolute range of $\log\epsilon$(Th/Eu) is 1.02 dex, with an observed standard deviation of $\pm0.20$ dex and an intrinsic standard deviation of $\pm0.11$ dex at the lowest metallicities. We infer that $68\%$ of $r$-process events have $\log\epsilon$(Th/Eu) yields that only vary within a factor of $\pm1.3$ or $\pm30\%$, while $5\%$ of $r$-process events have $\log\epsilon$(Th/Eu) yields that vary by factors $>3.3$ approaching $\sim$10. This serves as a strong constraint for the nuclear and astrophysical models of $r$-process sites, and suggests that achieving an $r$-process site that is both prompt and produces a robust $\log\epsilon$(Th/Eu) ratio is a challenge for current models.
Read the full abstract

All authors Shivani P. Shah, Rana Ezzeddine, Erika M. Holmbeck, Alexander P. Ji, Vinicius M. Placco, Ian U. Roederer, Mohammad K. Mardini, Sam A. Usman, Avrajit Bandyopadhyay, Timothy C. Beers, Anna Frebel, Terese T. Hansen, Charli M. Sakari, Chris Sneden

Solar and Stellar Astrophysics

Hot blue progenitors of stellar-mass black holes

Avishai Gilkis, Eva Laplace, Maria R. Drout et al. (+3 more)

While the connection between massive stars and supernova explosions is well established observationally, the link between massive stars and black hole formation remains elusive. Some massive stars may collapse directly to black holes without a successful supernova, and may therefore be observed as disappearing stars. We investigate the expected photometric properties of such black hole progenitors by combining detailed single and binary stellar evolution models with physically motivated prescriptions linking pre-collapse core structure to explosion or direct collapse outcome, together with stellar atmosphere calculations, producing synthetic photometry across standard ultraviolet to near-infrared filters. Weighting by an initial mass function and empirical binary distributions, we predict both the observable distribution of progenitor brightness and colour and the rate of direct-collapse events, which we estimate to be about 0.4 per century for a galaxy forming stars at 1 Msun/yr. We find that black hole progenitors are predominantly hot and blue at the pre-collapse stage, with many in Wolf-Rayet phases and luminous in the ultraviolet, while only a minority are red supergiants. Consequently, searches that focus primarily on red supergiants are likely to miss a substantial fraction of direct-collapse events. Monitoring campaigns that include ultraviolet-sensitive observations of nearby star-forming galaxies therefore provide a promising route to detecting disappearing massive stars, offering a direct observational probe of black hole formation. Our results provide predictions to interpret such surveys and constrain the channels that lead to black hole formation.
Read the full abstract

All authors Avishai Gilkis, Eva Laplace, Maria R. Drout, Charles D. Kilpatrick, Anna J. G. O'Grady, Christopher A. Tout

Astrophysics of Galaxies

JWST observations of photodissociation regions. IV. Carbonaceous emission band sub-components in NGC 7023 have distinct spatial distributions

D. Van De Putte, K. D. Gordon, K. Misselt et al. (+10 more)

We analyze JWST spectroscopy of the northwest filament of NGC7023, where the relatively soft radiation field results in a photodissociation region with an extended atomic hydrogen region, and strongly pronounced variations of the carbonaceous emission band profiles. We focus on the 16.4 and 17.4 um bands and their relation to the main bands at 3.3, 3.4, 5.2, 5.7, 6.2, 7.7, 8.6, 11.3, and 12.7 um, and aim to identify which bands and sub-features originate from co-spatial emission carriers. We apply a PAHFIT spectral decomposition to measure the emission bands and their individual sub-components, and produce maps that spatially resolve the main dissociation front (DF1). Nearly all emission maps peak at DF1, while the relative intensity in the atomic hydrogen region (ATM) varies strongly. We classify the features into spatial distribution types based on the intensity ratio in ATM relative to DF1. Most bands are of type I (low ATM/DF1; 3.3, 3.4, 5.2, 5.7, 11.3 um) or II (medium ATM/DF1; 16.2, 7.7, 8.6, 12.7, 16.4 um), while only few are of type III (high ATM/DF1; 11.0, 17.4 um). A breakdown of the 5.7, 7.7, 11.3 and 12.7 um bands into blue and red sub-components reveals that contributions on the blue side are of type III, while those on the red side are of type I or II. These strongly differing spatial distributions reveal that at least two different populations contribute to the 16-18 um range, and that these populations are also connected to the profiles of the 5.7, 7.7, 11.3, and 12.7 um bands. The maps further indicate a continued evolution of these profiles toward the central cavity of NGC7023, where fullerene emission (C60) was previously detected. We speculate that the population of emission carriers could be in an intermediate photochemical evolution stage that precedes fullerene formation.
Read the full abstract

All authors D. Van De Putte, K. D. Gordon, K. Misselt, A. N. Witt, A. Abergel, A. Noriega-Crespo, P. Guillard, M. Zannese, M. Elyajouri, B. Trahin, P. Dell'ova, M. Baes, P. Klaassen