Cosmology and Nongalactic Astrophysics · Cross-listed from gr-qc
Black Holes as Frequency-Dependent Filters of Stochastic Gravitational Waves
Sefi Katznelson, Aidan Minger and Stefano Profumo
Black holes ring when perturbed, whereas their response to a stationary gravitational-wave background is a real-frequency scattering problem, not a source of additional quasi-normal-mode lines. We make this standard distinction quantitative by treating a black hole as a frequency-, angle-, and polarization-dependent filter. For an isotropic stationary background around Schwarzschild holes, elastic scattering produces no net monopole signal, so horizon absorption is the only population-level spectral distortion. We calculate this transfer function for Schwarzschild holes in detail, identify its absorptive and phase-delay signatures, and connect the stationary response to the causal ringdown excited by a finite wave packet. We then promote the single-hole result to an angular and polarization transport kernel for a cosmological population. The resulting optical depth is negligible for realistic black-hole populations, including asteroid-mass primordial black holes comprising all dark matter. We then extend the analysis to Kerr holes, for which superradiance allows genuine amplification in selected co-rotating modes, but isotropic incidence and random
spin orientations strongly dilute the diffuse signal. Observable effects are therefore more likely in rare, nearby, aligned, rapidly spinning, or transiently illuminated systems than through cumulative cosmological propagation.
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High Energy Astrophysical Phenomena · Cross-listed from hep-ph
New bounds on light scalars from the tip of the red giant branch
Natnael Debru, Audrey Fung, Saniya Heeba et al. (+3 more)
Light, weakly coupled particles can be copiously produced in the hot and dense interior of
stars, and the resulting energy loss can leave observable imprints on entire stellar populations. For instance, additional energy loss from red giant cores delays helium ignition and brightens the tip of the red giant branch (TRGB). We revisit the TRGB bounds on light scalars coupled to electrons, of which the
Higgs portal is the prototypical example. In the degenerate cores of red giants, scalar emission is dominated by resonant conversion of longitudinal plasmons, which we compute using finite-temperature field theory. Rather than rescaling
neutrino emission rates at fixed
benchmark core conditions, we implement this emissivity in the MESA stellar
evolution code and self-consistently simulate the
evolution of red giants, including the backreaction of the scalar energy loss on the stellar structure. Comparing our predictions with the observed bolometric TRGB magnitudes of 27 Milky Way globular clusters, we exclude scalar-electron couplings $\alpha_{\phi ee} = g_e^2/4\pi > 1.6 \times 10^{-34}$ at 95% confidence for sub-keV masses, improving on previous bounds by nearly two orders of magnitude. In the context of the
Higgs portal, this corresponds to an exclusion on values of the mixing angle $\sin\theta > 2.2\times 10^{-11}$, providing the tightest bound for scalar masses in the $\sim 1\,\mathrm{eV} - 10\,\mathrm{keV}$ range.
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All authors Natnael Debru, Audrey Fung, Saniya Heeba, Hugo Schérer, Katelin Schutz, Aaron C. Vincent
Earth and Planetary Astrophysics
Exoplanet Atmosphere Spectral Sensitivity Analysis with PICASO: Jacobians, Linear-Gaussian Approximations, and Information Content
Natasha E. Batalha and Nicholas F. Wogan
Designing observatory and instrument architectures for complex missions like the Habitable Worlds Observatory (HWO) requires a rapid and rigorous mathematical framework to evaluate trade-offs across bandpass, spectral resolution, and signal-to-noise regimes. While full
Bayesian atmospheric
retrievals are the gold standard for atmospheric inference, they are too computationally expensive to explore this full parameter space. Here, we present a sensitivity analysis and
retrieval diagnostic toolkit within the open-source code PICASO. The core addition to the code base is a flexible solution for computing finite-difference Jacobian
matrices, which provides a local linearization of the forward model. These Jacobian
matrices characterize the sensitivity of the spectrum (either reflected, thermal, or transmission) to perturbations in any atmospheric state parameter, such as molecular abundances. Given the Jacobian for a certain reference atmosphere, our toolkit provides a suite of analytic diagnostic quantities under Gaussian assumptions for the prior, likelihood, and posterior. These include Fisher-
matrix-based estimates of 1$\sigma$ constraint intervals of atmospheric parameters, averaging kernels, singular-value-decomposition diagnostics for parameter degeneracies, and an information-content metric. We validate the results of our toolkit by comparing them to that of a full
Bayesian retrieval of an Earth-like
planet with an HWO-like facility. We show that our metrics can provide rapid understanding of model parameter sensitivity and that local linear-Gaussian approximations can diagnose dominant degeneracies seen in
retrievals as well as provide first order estimates of posterior probability distributions. Ultimately, this provides the community with a complementary toolkit for optimizing instrument design and conducting spectral sensitivity diagnostics.
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Astrophysics of Galaxies
Balmer Absorption Series and Broad Metal Lines in Two Luminous Little Red Dots
Bingjie Wang, Jenny E. Greene, Hanpu Liu et al. (+21 more)
Balmer absorption is common among little red dots (LRDs), but absorbers at or redward of systemic are rare, occurring in only $\sim10-15$% of H$\alpha$ absorbers. In this paper, we study two such exceptional cases with deep JWST/NIRSpec spectroscopy: 15 hr of high-resolution (G395H) observations of RUBIES-EGS-49140 (z=6.68), resolving the absorption in all four transitions from H$\alpha$ through H$\delta$, and medium-resolution spectroscopy (10 hr of G235M, 2 hr of G395M) of UNCOVER-A2744-45924 (z=4.46; 1.7x magnification). Both sources are among the optically reddest and most luminous LRDs known, and both show deep, near-systemic Balmer absorption troughs. We find two systematic trends along the Balmer series: the absorption centroids become more redshifted toward higher-order transitions, while the absorbed equivalent widths decline only weakly with increasing order, far less than expected from the atomic optical-depth ratios for a single attenuating screen. Ca\,{\sc{ii}}\,K is detected in absorption in both sources, whose offset follows the H$\alpha$ trough rather than the more redshifted higher-order Balmer lines. We further report the detection of a broad base in [Ne\,{\sc{iii}}]\,$\lambda$3870, along with broad [O\,{\sc{iii}}]\,$\lambda$4364, [O\,{\sc{iii}}]\,$\lambda5008$, and He\,{\sc{i}}\,$\lambda5877,\lambda7067$, while He\,{\sc{ii}}\,$\lambda$4687 remains undetected or weak. Standard AGN photoionization models cannot reproduce the observed line ratios, whereas AGNs with high gas densities provide a consistent explanation, as also indicated by the anomalously high He\,{\sc{i}}\,$\lambda7067/\lambda5877$ ratio. A possible explanation for the relative strengths of the Balmer absorption lines could be a dense, optically thick medium whose re-emission modifies their apparent absorption strengths, while the velocity progression may arise from stratification in the absorbing gas.
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All authors Bingjie Wang, Jenny E. Greene, Hanpu Liu, Nicholas Kaaz, Gabriel B. Brammer, Raphael E. Hviding, Ivo Labbé, Joel Leja, Jorryt Matthee, Rohan P. Naidu, Alberto Torralba, Josephine F.W. Baggen, Nikko J. Cleri, Seiji Fujimoto, Lukas J. Furtak, Anna de Graaff, Michaela Hirschmann, Vasily Kokorev, Erini Lambrides, Ian McConachie, Erica J. Nelson, Adèle Plat, Weichen Wang, Adi Zitrin
Earth and Planetary Astrophysics
Post-perihelion Photometric and Spectroscopic Monitoring of the Interstellar Comet 3I/ATLAS
Goldy Ahuja, Shashikiran Ganesh, K. Aravind et al. (+12 more)
The third interstellar object, comet 3I/ATLAS, was observed using various Indian
telescopes during its post-perihelion
evolution. We carried out imaging and spectroscopic observations of the comet at multiple epochs using the 0.5-m, 1.2-m, and 2.5-m
telescopes of the Physical Research Laboratory and the 2-m Himalayan Chandra
Telescope (HCT) operated by the Indian Institute of Astrophysics. Additionally, time-series photometry was obtained on 7 epochs using the 0.132-m refractor of Cepheid Observatory. The spectroscopic observations of 3I/ATLAS reveal signatures of molecular emission from CN, C$_2$, and C$_3$, as commonly observed in the emission spectra of solar system comets. The production rates and rate ratios indicate that the composition of the 3I/ATLAS transitioned from carbon-depleted (pre-perihelion) to carbon-typical (post-perihelion). The change in carbon composition could be due to exposure of fresh material from subsurface layers near perihelion. We also performed photometric observations to determine broadband colours and the
spin period. The measured colours are $B-V=$ 1.03 $\pm$ 0.13 mag, $V-R=$ 0.59 $\pm$ 0.11 mag, $R-I=$ 0.08 $\pm$ 0.04 mag, $g-r=$ 0.52 $\pm$ 0.09 mag, and $r-i=$ 0.13 $\pm$ 0.08 mag. The colours are redder than the Long-Period Comets of the solar system and the Sun in $B-V$ and $V-R$, but near solar in $R-I$. The measured colours remain nearly constant throughout the observing period and are consistent with the reported pre-perihelion values. The colours and the reflectivity gradient match the photometric colours of the `ultrared-material rich' objects in the solar system. The nuclear radius derived from non-gravitational force lies between 0.45 and 0.65 km.
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All authors Goldy Ahuja, Shashikiran Ganesh, K. Aravind, Emmanuel Jehin, Bhavya Ailawadhi, Vikrant K. Agnihotri, B. Arvind, Pallavi Saraf, Alka Singh, Deekshya R. Sarkar, Sunil Chandra, Prithish Halder, Devendra Sahu, T. Sivarani, Anil Bhardwaj
Cosmology and Nongalactic Astrophysics
Hunting Thermal Relics in the DESI DR1 Ly$\alpha$ Forest
Emanuelly Silva, Artur Ladeira, Rafael C. Nunes et al. (+1 more)
We investigate constraints on additional relativistic species and thermal sterile
neutrinos using the DESI DR1 one-dimensional Lyman-$\alpha$ forest power spectrum, combined with Planck 2018 CMB and DESI DR2 BAO measurements. We consider both the $\Lambda$CDM+$N_{\rm eff}$ extension and a thermal with a different-temperature sterile-
neutrino (DTS) scenario, in which the sterile relic can be colder than the standard
neutrino background. We first validate the DESI two-parameter $P_{\rm 1D}$ compression for the DTS model, finding that the residual cosmological dependence not captured by the compressed parameters remains below 0.15%. No significant evidence for additional radiation or a sterile component is found. For $\Lambda$CDM+$N_{\rm eff}$, we obtain $N_{\rm eff}<3.41$ at 95% credibility from CMB+DESI-BAO+DESI-$P_{\rm 1D}$. In the DTS scenario, the full CMB+DESI-BAO+DESI-$P_{\rm 1D}$ combination yields the stringent bound $m_s^{\rm eff}<0.061\,{\rm eV}$, highlighting the complementarity of BAO and Lyman-$\alpha$ information in constraining the massive sterile abundance. We further interpret the allowed $\Delta N_{\rm eff}$ in terms of thermal light relics, deriving lower limits on their decoupling temperatures that reach the QCD epoch.
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All authors Emanuelly Silva, Artur Ladeira, Rafael C. Nunes, Eleonora Di Valentino
High Energy Astrophysical Phenomena
Resolving the Galactic Center Region's Gamma-Ray Emission and Searching for its Neutrino Counterpart with HAWC and IceCube
S. Yun-Carcamo, R. Babu, for the HAWC et al. (+1 more)
The Galactic Center (GC) is a
prime candidate for petaelectronvolt
cosmic-ray acceleration, with gamma-ray emission observed by the High Altitude Water Cherenkov (HAWC) Observatory extending beyond 100 TeV. We present an analysis of the GC using ~2860 days of HAWC data, with increased exposure and improved sensitivity relative to previous results. The best-fit gamma-ray emission model includes a point source (HAWC J1745-2857) and a Galactic diffuse emission component. Assuming a hadronic origin, we construct the corresponding
neutrino signal template and search for it in 12 years of IceCube
muon-track data. No significant
neutrino excess is found, and we report the first upper limit on the high-energy
neutrino flux associated with the multi-component spatial model of the GC derived from HAWC data. The limit is approximately 12 times the nominal
neutrino flux predicted from the HAWC gamma-ray model under a hadronic interpretation, and therefore it does not yet test the optically thin hadronic scenario.
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All authors S. Yun-Carcamo, R. Babu, for the HAWC, IceCube collaborations
High Energy Astrophysical Phenomena
The chirping of Lense-Thirring precession in tidal disruption event accretion flows
Andrew Mummery and Eliot Quataert
Tidal disruption event X-ray light curves do not appear to show clear signs of periodic modulation. This is naively somewhat surprising since the
stars that are disrupted originate at large scales in the
galaxy where they cannot know about the orientation of the black hole
spin axis. This should lead to the formation of a misaligned disk that precesses due to Lense-Thirring torques, modulating X-ray emission from the inner disk regions. We argue that in fact the properties which are required for solid-body precession, namely a thick $(H/R\sim {\mathcal O}(1))$ disk, naturally lead to rapid precession period change, with a per-period increase of $\Delta T_{\rm prec}/T_{\rm prec} \sim {\mathcal O}(1-10)$, as the disk spreads to larger radii to conserve angular momentum. In other words the precession of thick TDE disks is aggressively chirped, washing out any possibility of observing multiple cycles other than for fine tuned regions of parameter space. The global disk
alignment timescale is equally strongly chirped by the exact same mechanism, meaning that TDE disks will not in general align with the black hole
spin axis during a super-Eddington phase, and should generically show global quasi-steady warp profiles at the beginning of any thin disk phase. These results have important implications for interpreting timing features associated with TDE disks, including models for quasi-periodic X-ray eruption timing phenomenology, and the observational properties of TDE disks in the initial transition to the thin disk phase.
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Instrumentation and Methods for Astrophysics
Initial modeling and testbed feasibility studies of WaveDriver: a laser guide star AO system for HWO
Dominic F. Sanchez, Benjamin L. Gerard, Peter Waswa et al. (+16 more)
The Habitable Worlds Observatory (HWO) will require $>100\times$ greater wavefront stability than achieved by JWST, pushing conventional
telescope architectures to picometer-level performance limits. WaveDriver is a mission concept that relaxes these constraints by employing an external
laser guide
star (LGS) spacecraft flying in formation with HWO to enable wavefront sensing and control. Early results from the High Contrast Testbed demonstrate feasibility of required stability using coronagraphs, multiple deformable mirrors, and a suite of wavefront sensors. We report mission design analyses, initial testbed stability metrics, compare sensor performance, and present an optical model that quantifies LGS brightness, conjugation errors, and field errors arising from finite beacon separation.
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All authors Dominic F. Sanchez, Benjamin L. Gerard, Peter Waswa, Alex Geringer-Smith, Aditya Sengupta, Alexx Perloff, Michael Messerly, William Moore, Matthew Cook, Paul Pax, Cesar Laguna, Mathew DeMartino, Kevin Bundy, Rebecca Jensen-Clem, Aaron Lemmer, S. Mark Ammons, Megan Eckart, Lisa Poyneer, Eric Strang
Solar and Stellar Astrophysics · Cross-listed from physics.plasm-ph
Proton Heating Rates in the Inner Heliosphere: Helios Observations
Alaa Fayad, Anna Tenerani and Chadi Salem
Solar wind
protons exhibit a temperature anisotropy that deviates from the double-adiabatic prediction, suggesting an additional energy source. To investigate solar wind heating mechanisms, we analyze Helios 1 and 2 data and characterize the radial
evolution of the adiabatic invariants and anisotropic heating rates of fast wind
protons, considering both the bulk population and its core and beam components separately. Unlike previous studies, we account for
proton heat fluxes and deviations from the Parker spiral caused by large-amplitude fluctuations, which causes significant differences in the parallel heating rates compared to earlier results. Although earlier work has questioned the reliability of power laws to estimate heating rates and proposed as a more robust approach the investigation of the radial
evolution of adiabatic invariants, we show that the two approaches yield consistent results when applied to the same
dataset. Our analysis shows that all
proton populations considered require net perpendicular heating, consistent with earlier studies. In contrast, the parallel energy
evolution differs between populations. Core
protons require parallel heating, whereas beam
protons undergo parallel cooling although the total
proton population undergoes a net parallel cooling. This behavior is consistent with the combined action of
turbulence and core-beam kinetic instabilities, which together can drive preferential perpendicular heating while simultaneously produce parallel cooling in the fast solar wind. Core
proton parallel heating could instead be a signature of Alfvén wave decay.
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Astrophysics of Galaxies
The Deep Learning Halo Definer: A Multimodal Framework for Halo Mass and Gas Fraction Inference on Galaxy Groups and Clusters
Caleb Ogle, Kalvyn N. Poncelet Adams, Benjamin D. Oppenheimer et al. (+5 more)
Accurately inferring dark matter
halo properties like the total
halo mass (M_{
halo}) and gas fractions (f_{gas}) remains particularly challenging at group scales, where low member counts, shallow potential wells, and AGN feedback-driven baryon expulsion introduce significant observational scatter. As large-scale surveys begin to provide unprecedented multi-wavelength data, there is a pressing need for methods that can jointly leverage diverse observables to overcome these uncertainties. We introduce the Deep Learning
Halo Definer (DLHD), a
multimodal deep learning framework that simultaneously processes
galaxy catalogues and X-ray imaging through the combination of a Deep Sets and a Convolutional Neural Network (CNN) to improve M_{
halo} and f_{gas} estimation for
galaxy groups and clusters. Using mock
datasets derived from the IllustrisTNG300 hydrodynamic simulation, we demonstrate that the DLHD outperforms each of its component networks individually, achieving RMSE improvements in M_{
halo} of 1.9x over Deep Sets and 1.3x over the CNN alone. For the gas fraction enclosed within R_{200c}, DLHD reduces RMSE by 2.0x relative to Deep Sets and 1.1x relative to the CNN alone, with consistent improvements across other apertures. These results highlight a novel ability to leverage multi-band information inaccessible to single-modality methods, positioning DLHD as a promising tool for next-generation survey analyses.
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All authors Caleb Ogle, Kalvyn N. Poncelet Adams, Benjamin D. Oppenheimer, Naomi Gluck, Matthew Ho, Daisuke Nagai, Joseph N. Burchett, Mohammadreza Ayromlou
Cosmology and Nongalactic Astrophysics
Axio-Dilaton Dark Energy: A Dynamical Systems and Bayesian Inference Analysis
Mario Ramos-Hamud, Gabriela García-Arroyo, Fernando Quevedo et al. (+1 more)
We initiate a systematic cosmological investigation of an axio-dilaton system governed by a curved field-space metric as generically motivated by supergravity and string compactifications. The scalar sector consists of a light scalar dilaton field evolving along an asymptotically exponential potential and a pseudoscalar field spanning an essentially flat direction, kinetically coupled through an exponential field-space metric. Deviations from the asymptotic regime are incorporated by introducing a generalised Albrecht-Skordis potential containing a
polynomial factor. Utilising a dynamical systems approach alongside numerical
evolution and
Bayesian inference, we constrain the model using Type Ia
Supernovae (SNe Ia), Baryon Acoustic Oscillations (BAO) and Planck 2018 distance-prior data. We identify a parameter degeneracy indicating that steeper potentials demand stronger field-space kinetic couplings to sustain late-time
cosmic acceleration. Finally, a joint likelihood analysis reveals that while the model successfully accounts for dark energy dynamics, it is only slightly statistically favoured over $\Lambda$CDM by current observations.
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All authors Mario Ramos-Hamud, Gabriela García-Arroyo, Fernando Quevedo, J. Alberto Vázquez
Solar and Stellar Astrophysics
Chromospheric sensitivity of stellar spectral lines: an unsupervised machine learning classification
Juan I. Peralta and Mariela C. Vieytes
Stellar
magnetic activity alters thousands of spectral lines, limiting high-precision radial-velocity measurements, abundance analyses, and planetary characterization. We present a preliminary classification of 6403 atomic lines in synthetic visible spectra from a sequence of NLTE semi-empirical dG2 atmospheric models with increasing chromospheric heating. Principal-component analysis shows that the dominant component traces overall response amplitude, while the second distinguishes early from late responders. DBSCAN applied in the full nine-dimensional response space identifies a dense stable core and an activity- sensitive non-core group comprising about 11% of the lines. The stable core provides candidate lines for activity-insensitive measurements, while sensitive lines provide candidate activity diagnostics. Sensitive transitions tend to have low lower-level energies, although the populations overlap, making lower-level energy a statistical discriminator rather than a line-by-line predictor. A spectral sensitivity map shows that small average variations can hide nonlinear or compensating responses, demonstrating the value of the complete line-response trajectory for classification.
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Solar and Stellar Astrophysics
An Open Cluster Origin for Most Solar-Type Binaries in the Solar Neighborhood and Implications for Primordial Planet Stability
Anna C. Childs and Aaron M. Geller
We present the first Gaia-calibrated estimate of the contribution of dynamically processed open clusters (OCs) to the nearby solar-type field binary population and investigate the implications for primordial
planet stability. We combine Gaia DR3 observations, empirical models of cluster formation and dissolution, and direct N-body simulations to constrain the fraction of field FGK-type binaries within 1 kpc that originated in OCs over the past 5 Gyr. We find that at least ~53% of solar-type field binaries formed in OCs with initial masses > 200 M_Sun, where dynamical processing becomes significant. We quantify the effects of stellar encounters and binary orbital
evolution on the stability of both circumbinary and circumstellar
planets by deriving empirical prescriptions for circumbinary
planet destabilization as a function of binary separation and for the fractional reduction of stable circumstellar coplanar phase space. These results provide a framework for evaluating how OC dynamical
evolution may influence the stability of
planets in binary systems and therefore contribute to observed
exoplanet demographics.
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Solar and Stellar Astrophysics
Inflated Supermassive Stars as Little Red Dots and Progenitors of Supermassive Black Holes
Wenbin Lu
JWST has uncovered an abundant population of compact, red sources at high
redshifts, termed little red dots (LRDs). We study whether they could be explained by thermally relaxed, hydrogen-burning, metal-enriched supermassive
stars (SMSs). We construct 1D models in hydrostatic and thermal
equilibrium, including a radiation-pressure-dominated, CNO-burning core and an outer envelope with
metallicity-dependent opacity, non-adiabatic convection, and an effective treatment of super-Eddington surface layers. The luminosity is close to the Thomson-scattering Eddington limit. The Fe-opacity bump drives the formation of a strongly inflated, low-mass envelope, while hydrogen recombination terminates the envelope at a bound photosphere. For M=$10^4$ to $10^6$ Msun and metal mass fractions $Z=10^{-4}$ to $10^{-2}$, we find that the most metal-rich models (Z ~ $10^{-2}$) develop highly inflated envelopes and reach Teff ~ 7000 K. We suggest that such enriched SMSs could instead be assembled through runaway stellar collisions in compact
star clusters. The GR instability sets a maximum mass that depends on the core rotation rate. The nonrotating and rotating models have maximum masses $3\times10^5$ to $3\times 10^6$ Msun, and maximum luminosity of the order $10^{44}$ erg/s, comparable to the observed bright-end cutoff of the LRD luminosity function. Core hydrogen depletion can drive initially stable SMSs across the instability threshold after a lifetime of order 1 Myr. If each LRD leaves a black hole retaining most of its mass, the observed LRD abundance implies a present-day remnant density of order $10^{-2}\rm cMpc^{-3}$, consistent with the local abundance of supermassive black holes. Cool SMSs naturally produce weak X-ray and weak high-ionization lines. Non-LTE effects may significantly modify the Balmer features and the continuum opacity, and may lower Teff below our LTE value.
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Solar and Stellar Astrophysics
The Last Gasps of a Dying Star: ALMA Observations of the Pre-Planetary Nebula IRAS 06530-0213
Raghvendra Sahai, Wouter Vlemmings, Guillermo Quintana-Lacaci et al. (+16 more)
We present high angular-resolution ($\sim 0.{''}1 - 0.{''}5$) ALMA observations of millimeter-wave line and continuum emission (at $\sim0.44$ and $0.88$ mm) in the pre-planetary nebula IRAS 06530–0213 (IRAS 06530). These data show the presence of an extended circular ring – first evidence of the last thermal-pulse preceding the post-AGB phase in a carbon
star – and a central bipolar nebula (CBN) and
torus. The mass-loss rate of IRAS 06530's AGB progenitor decreased immediately after the thermal pulse, then rose again just before the post-AGB phase as evidenced by the presence of filamentary arc structures around the CBN. The arc stuctures are likely part of a 3-D Archimidean spiral structure generally attributed to the presence of a binary companion. But we do not find a compact continuum source at the location of IRAS 06530's central
star, such as that associated with the compact dusty disks typically found in disk-prominent post-AGB objects known to have binary companions. The expansion ages derived for the
torus and CBN imply that IRAS 06530's progenitor transitioned to a post-AGB
star $\lesssim700$ yr ago. The molecular mass of the ejecta in IRAS 06530 is dominated by the filamentary arc region with a mass $M_{H_2}=(0.12-0.25) M_{\odot}$. Compared with solar values, the
torus of IRAS 06530 appears to be significantly (modestly) enriched in $^{13}$C and $^{17}$O ($^{15}$N) as well – a pattern of rare-isotope enrichment inconsistent with standard nucleosynthesis models. From the luminosity of IRAS 06530 and the age of its detached shell, while it was still on the AGB, we infer that the mass of IRAS 06530's progenitor was $(1.6-3.4) M_{\odot}$.
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All authors Raghvendra Sahai, Wouter Vlemmings, Guillermo Quintana-Lacaci, Hyosun Kim, Javier Alcolea, Bruce Balick, Eric G. Blackman, Arancha Castro-Carrizo, Orsola de Marco, Joel H. Kastner, Eric Lagadec, Chin-Fei Lee, Miguel Santander-García, Carmen Sánchez Contreras, Toshiya Ueta, Albert A. Zijlstra, Valentin Bujarrabal, Laurence Sabin, Daniel Tafoya
Astrophysics of Galaxies
CECILIA: Using Flexible Photoionization Models to Accurately Measure Abundances without Auroral Lines
Nathalie A. Korhonen Cuestas, Allison L. Strom, Yijia Li et al. (+6 more)
JWST has facilitated the detection of faint, auroral emission lines needed to directly measure the electron temperature and elemental abundances in high-
redshift galaxies. However, such measurements still require substantial observational investment, potentially making self-consistent, population-level studies of direct-method
metallicity scaling relations across multiple epochs of
Cosmic time prohibitively expensive. Photoionization modeling could allow us to measure
metallicity using more routinely-observed emission lines across larger
galaxy samples with shallower spectra. We use $z\sim 2$
galaxies from the CECILIA survey and local
galaxies and H II regions from the LBT $Y_P$ Project to compare abundance measurements made via the $T_e$ method to abundances estimated using the novel photoionization modeling code, Cue. Based on the results, we explore the viability of, biases introduced by, and the best practices for measuring gas-phase
metallicity with photoionization modeling. We show that Cue can be used to accurately measure O/H while remaining agnostic to the ionizing spectrum and that accurate recovery of O/H can be achieved with relatively bright oxygen and sulfur lines, demonstrating that Cue could be used to measure
metallicity in large samples that lack the depth necessary for direct measurements of O/H. However, using sulfur emission lines can also severely bias the results of photoionization modeling in high-
redshift galaxies, where non-Solar abundance patterns are common. We make recommendations regarding the use of photoionization models to measure
metallicity in local and high-
redshift samples and future developments to photoionization modeling methods.
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All authors Nathalie A. Korhonen Cuestas, Allison L. Strom, Yijia Li, Noah S. J. Rogers, Caroline von Raesfeld, Gwen C. Rudie, Ryan F. Trainor, Menelaos Raptis, Zhuyun Zhuang
High Energy Astrophysical Phenomena
Importance of the Resonant Cosmic-Ray Streaming Instability Upstream of Collisionless Shocks
Bricker Ostler, Benedikt Schroer and Damiano Caprioli
Cosmic rays (CRs) escaping collisionless shocks form a dilute, relativistic population whose current amplifies the upstream
magnetic field, a process widely attributed to the non-resonant (Bell) instability. Solving the dispersion relation for both cold and finite-spread CR distributions, we show that for the maximum-energy escaping population, the resonant mode can outgrow the non-resonant mode. At slower shocks, this dominance persists for broader CR distributions, and sufficient pitch-angle broadening can even stabilize the non-resonant mode while leaving the resonant mode unstable. Relativistic hybrid particle-in-
cell simulations confirm the cold-beam linear theory predictions and, in the nonlinear regime, saturate at $\delta B/B_0 \sim 1$ with significant pitch-angle redistribution. Neglecting the resonant instability thus underestimates
magnetic field growth at the very scale needed to confine the highest-energy escaping CRs.
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Earth and Planetary Astrophysics
Tectonics on early Earth driven by Earth's changing shape during tidal recession of the Moon
Simon J. Lock
Few fragments of Earth's earliest crust have survived, and so this formative period of our
planet's history is shrouded in mystery. To leverage the limited data available, it is important to understand all the processes that could have shaped our young
planet. Here, I explore a previously neglected aspect of early-Earth dynamics: rotation. Earth after the Moon-forming impact was rapidly rotating with its rotation rate slowing significantly during the first tens of millions of years after the impact as the Moon tidally receded. Using planetary structure and tidal
evolution calculations, I show that the initially distorted structure of Earth would likely have led to significant latitudinal variations in primary crustal thickness. Further, the subsequent changes in Earth's shape in response to its slowing rotation rate could have driven extensive tectonic activity and modulated the response of the crust to other forces. There was extension of the crust in polar regions and convergence in the equatorial regions at rates potentially comparable to those forming the Himalayas today in high-angular momentum scenarios. Depending on the rheology of the earliest crust, such motions could have led to burial of hydrated and weathered surface material, extensive volcanism, and degassing of Earth's interior. Phase changes due to increases in internal pressure could have led to delamination of parts of the crust, producing early mantle heterogeneities. Hydrated secondary melting of the crust and the production of evolved magmas could explain the emergence of a diversity of rock types within tens of millions of years of Earth's formation.
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Solar and Stellar Astrophysics
The "Other" Centuries-Long Record of Solar Magnetic Activity Cycles: Lessons From the Stars
Jason T. Wright, Travis S. Metcalfe, Kristof Petrovay et al. (+1 more)
Studies of space
climate and solar
magnetic activity and studies of stellar dynamos and
magnetic cycles are separated by discipline and by the quality of the data we have to work with: the Sun gives us detailed knowledge of a single
star, while the
stars give us comparatively sparse data across a range of (sometimes poorly known) masses and ages. This review, a collaboration among scientists with expertise in stellar astronomy, space
climate, and solar physics, seeks to provide a guide to what the Sun's and
stars'
magnetic activity records can tell us about how stellar dynamos operate on decadal, millennial, and stellar-evolutionary timescales. It reviews the historical Solar sunspot record, terrestrial cosmogenic isotope records, and decades-long chromospheric activity measurements of dozens of sun-like
stars across a range of masses, ages, and
metallicities near the solar value. Particular emphasis is placed on the Maunder minimum, and the hunt for similar events in the stellar record, especially the recently discovered grand minimum event ongoing in the
star HD 166620. These records show that solar-like dynamos are a common feature of Sun-like
stars, and
magnetic grand minimum events akin to the Maunder minimum might be very rare, with only one identified in 3,000
star-years of
magnetic activity records. Together, solar and stellar dynamo studies are bringing a still-fuzzy picture into focus in which stellar
magnetic activity weakens as
stars spin down over billions of years towards a critical Rossby number near the solar value, at which point stellar cycles begin to be frustrated. These periods of frustration manifest as
magnetic grand minima, and increase in frequency until they become permanent and
stars enter a period of very low and constant
magnetic activity.
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All authors Jason T. Wright, Travis S. Metcalfe, Kristof Petrovay, Hisashi Hayakawa
Cosmology and Nongalactic Astrophysics
Stress-testing the spatially flat Universe: nonparametric spatial curvature determination from DESI DR2
Hannah C. Turner, Suhail Dhawan, Sunny Vagnozzi et al. (+2 more)
We present a nonparametric determination of spatial
curvature using only late-time geometrical probes. Under a Gaussian Process smoothness prior, we jointly constrain the dimensionless expansion history and $\Omega_K$, combining three Type Ia
Supernovae (SNeIa) samples with either DESI DR2 line-of-sight baryon acoustic oscillations (BAO) or
cosmic chronometers (CC) data. From our baseline SNeIa+BAO analyses we find $\Omega_K=0.219^{+0.110}_{-0.111}$, $\Omega_K=0.330^{+0.098}_{-0.150}$ and $\Omega_K=0.260^{+0.124}_{-0.127}$ for the PantheonPlus, DES Dovekie and Union3 SNeIa samples respectively. These nonparametric results mildly favour an open Universe, supporting recent hints in this direction, and improve on the sensitivity of a previous application of the method by up to a factor of $\sim 2.5$. We find consistent constraints combining SNeIa and CC, whereas restricting SNeIa data to the
redshift range covered by BAO somewhat weakens the constraints and shifts the PantheonPlus central value to $\Omega_K<0$. Our results depend only on late-time relative distances and expansion rates, making them insensitive to the absolute distance scale calibration, while relying neither on
Cosmic Microwave Background data nor on a parametric dark energy model.
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All authors Hannah C. Turner, Suhail Dhawan, Sunny Vagnozzi, Alice Townsend, Peter Massey
Cosmology and Nongalactic Astrophysics
Model-Independent Measurement of Baryon Gas Fractions through Galaxy-Galaxy Lensing and the Kinematic Sunyaev-Zel'dovich Effect
R. Henry Liu, Uroš Seljak, Simone Ferraro et al. (+52 more)
Baryon feedback is a leading source of systematic uncertainty for cosmology from weak
lensing, but measurements of the gas distribution around
galaxies have largely relied on parametric profile models or simulation-calibrated frameworks. We present model independent measurements of the radial gas fraction profile around
galaxies, combining
galaxy-
galaxy lensing and kinematic Sunyaev-Zel'dovich (kSZ) effect. We introduce a method that applies the same radial $\Delta\Sigma$ aperture filter to both the
galaxy-
galaxy lensing shear field and the velocity-weighted kSZ temperature maps; their ratio directly yields $\Delta\Sigma$ filtered gas fraction $f_{\rm gas}(R)$, the ratio of ionized gas to total matter as a function of projected radius. We apply this approach to DESI DR2 Bright
Galaxy Survey (BGS, $\bar{z} \approx 0.26$) and Luminous Red
Galaxy (LRG, $0.4 < z < 1.1$) samples, using ACT DR6 component-separated CMB maps for kSZ, and the HSC Year 3 shear catalog for weak
lensing. After correcting for ACT beam suppression using a simulation-calibrated compensation factor, we detect baryon depletion relative to the
cosmic mean baryon fraction at SNR = 17.2 (BGS) and SNR = 13.8 (LRG bin 1). Comparison with six hydrodynamical simulations from the Illustris, IllustrisTNG, SIMBA, and FLAMINGO suites shows that the fiducial FLAMINGO run most closely tracks the observed radial gas distribution in both samples, with Illustris-1 and TNG300-1 bracketing the data from below and above at small radii. We find a mild discrepancy between the kSZ measurements in the South and North Galactic Caps in one LRG
redshift bin, which may indicate residual systematics. We show that the ratio is robust to splits by stellar mass and to the removal of close pairs. These results establish $\Delta\Sigma$ filtering of kSZ versus weak
lensing signal as a model-independent probe of the baryon distribution around
galaxies.
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All authors R. Henry Liu, Uroš Seljak, Simone Ferraro, Boryana Hadzhiyska, Frank J. Qu, Bernardita Ried Guachalla, Emmanuel Schaan, Jessica Nicole Aguilar, Steven Ahlen, Anton Baleato Lizancos, Florian Beutler, Davide Bianchi, David Brooks, Aurelio Carnero Rosell, Francisco Javier Castander, Todd Claybaugh, Andrei Cuceu, Axel de la Macorra, Jaime E. Forero-Romero, Enrique Gaztañaga, Satya Gontcho A Gontcho, Gaston Gutierrez, Klaus Honscheid, Dragan Huterer, Mustapha Ishak, Stephanie Juneau, Tanveer Karim, David Kirkby, Anthony Kremin, Ofer Lahav, Martin Landriau, Laurent Le Guillou, Martine Lokken, Marc Manera, Aaron Meisner, Ramon Miquel, John Moustakas, Seshadri Nadathur, Jeffrey A. Newman, Hernan Enrique Noriega, Will Percival, Ignasi Pérez-Ràfols, Francisco Prada, Corentin Ravoux, Graziano Rossi, Lado Samushia, Eusebio Sanchez, Christoph Saulder, David Schlegel, Michael Schubnell, Hee-Jong Seo, Małgorzata Siudek, Gregory Tarlé, Benjamin Alan Weaver, Rongpu Zhou
Astrophysics of Galaxies
The ALMA View of High-Redshift Galaxy Formation
Renske Smit and Rebecca A.A. Bowler
The advent of routine operations with the Atacama Large Millimeter/submillimeter Array (ALMA) in the last decade has led to a revolution in the direct study of the interstellar medium (ISM) in `normal' high-
redshift galaxies in the rest-frame far-infrared (FIR). This review summarizes the observational literature on z>6.5 sources observed with ALMA and NOEMA (NOrthern Extended Millimeter Array). The main findings are as follows: Cool gas consistently scales with
star-formation in a wide range of
galaxy environments, similar to local relations, suggesting fundamental processes of
star-formation stay relatively constant over 13 billion years of
cosmic time. Significant metal enrichment is present in
galaxies just 300-400 million years after the Big Bang. There is a trend to higher obscured fraction of
star formation with stellar mass and SFR already in place at z~7, with measurements of the
cosmic SFR density showing that >10 percent of the SFR density is obscured at this epoch. The estimated dust masses compared to the stellar mass suggest that rapid dust enrichment occurs, likely from
supernova with little dust destruction and/or rapid growth in the ISM, which is in agreement with maximal predictions from models. In individual sources cold disks are already in existence, with their gas disks being more extended and smooth than their observed stellar counterparts.
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High Energy Astrophysical Phenomena · Cross-listed from nucl-th
Evidence for a Continuous Hadron–Quark Transition in Cold Dense Matter
Yong-Jia Huang and Bikai Gao
Statistical evidence for a continuous
hadron-
quark transition is found in this work. Confronting microscopic descriptions connecting the Parity Doublet Model and the Nambu–Jona-Lasinio model with observationally constrained non-parametric equations of state,
Bayesian model comparison decisively favors a boundary-free crossover over the conventional first-order Maxwell construction ($\Delta\ln\mathcal{Z} \sim +7.20$) and fixed-boundary crossover ($\Delta\ln\mathcal{Z} \sim +5.16 $). The preferred crossover decouples the intermediate stiffening from the intrinsic stiffness of each phase, allowing both sectors to exhibit physical self-consistency. The chiral-invariant nucleon mass is large, $M_0 = 834^{+28}_{-92}\text{ MeV}$, as expected for a substantial baryon mass surviving chiral restoration. While the
quark sector accommodates a small pairing gap $\Delta_{\rm CFL} = 88^{+83}_{-59}\text{ MeV}$ consistent with perturbative QCD limits, avoiding the excessively large gaps $\Delta_{\rm CFL} \gtrsim 200\text{ MeV}$ required by the other constructions. These results demonstrate that a realistic unified description represents a continuous transition deviating substantially from isolated effective models of
hadrons and
quarks. Exploring genuine phase boundaries is therefore necessary through the emergence of spinodal instabilities within unified frameworks.
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Astrophysics of Galaxies
LoTSS of dual AGN: enhanced detectability and prospects for a systematic search
Q. D'Amato, F. Mannucci, E. De Rubeis et al. (+25 more)
Context: Dual active galactic
nuclei (DAGN) - systems of two accreting supermassive black holes at kpc-scale separations - trace
galaxy mergers and are the progenitors of gravitational-wave sources targeted by
pulsar timing arrays and the upcoming
Laser Interferometer Space
Antenna. However, their
radio properties remain poorly constrained, particularly at high
redshift. Aims: We demonstrate the detectability of high-
redshift DAGN at 144 MHz through sub-arcsec imaging of the LOFAR Two-metre Sky Survey (LoTSS) and characterize their low-frequency
radio properties. Methods: We cross-matched 92 spectroscopically confirmed DAGN (z > 0.3, projected separation r_p < 30 kpc) with the LoTSS DR2 catalog and reprocessed international LOFAR
telescope (ILT) data for three systems (0.59 < z < 2.39), achieving ~0.3 arcsec resolution at 144 MHz. Multi-frequency analysis and brightness-temperature diagnostics were used to investigate the
radio emission. Results: We obtained high-quality ILT images for all three systems. In one source at z = 1.49, both AGN are detected at >5 sigma, making it one of the highest-
redshift and faintest
radio-detected DAGN. Brightness temperatures confirm AGN-powered emission even in sub-mJy sources. In the other two systems only one AGN is detected; for one, the new data constrain the low-frequency spectrum of a compact steep-spectrum source, indicating that its morphology is driven by jet-ISM interaction rather than the companion
galaxy. For the 92 objects sample, the LoTSS detection rate is ~24%, significantly higher than for matched single AGN (~9-10%), suggesting an enhanced detectability of DAGN in the LoTSS. Conclusions: Low-frequency sub-arcsec
radio observations provide an efficient, dust-unbiased method to detect and characterize DAGN. This pilot study establishes a
benchmark for the forthcoming all-sky ~0.3 arcsec iLoTSS survey and future SKA observations.
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All authors Q. D'Amato, F. Mannucci, E. De Rubeis, I. Prandoni, A. De Rosa, M. Scialpi, M. Kunert-Bajraszewska, A. Janiuk, A. Krauze, L. Battistini, E. Bertola, C. Bracci, A. Chakraborty, M. Ceci, C. Cicone, G. Cresci, A. Marconi, C. Marconcini, E. Nardini, M. Parvatikar, A. Peca, K. Rubinur, P. Severgnini, C. Spingola, L. Ulivi, G. Venturi, C. Vignali, M. V. Zanchettin
Cosmology and Nongalactic Astrophysics · Cross-listed from hep-ph
Non-Perturbative Modulus Decay and Multi-Component Dark Matter
Gordon Kane, Leia Price, Luis Rufino et al. (+2 more)
Non-thermal cosmological histories rest on the assumption that scalars displaced during inflation undergo coherent oscillations, dominate the energy density of the universe before Big Bang Nucleosynthesis, and decay perturbatively through gravitationally suppressed interactions. In addition, usually a single dark matter component is assumed. This early matter-dominated era is the basis for the usual predictions of non-thermal WIMP production,
axion dark matter,
entropy generation, and dark radiation. This paper examines whether this picture is dynamically robust against non-perturbative decay of the modulus condensate. In this work, we study non-perturbative particle production from oscillating moduli using the effective field theory appropriate to $G_2$ compactifications. We find that non-perturbative production of Wino-like
fermions is strongly suppressed in the relevant parameter regime. In contrast, a modulus-dependent
axion kinetic term admits narrow instability bands with growth rates that can exceed the Hubble rate. A linear Floquet analysis alone, however, cannot determine whether these bands significantly deplete the modulus condensate, since
cosmic expansion, backreaction, rescattering, and higher-order operators in the effective theory can become important. As a result, the conventional modulus-dominated cosmology remains robust against Wino and gauge-field preheating, while the
axion channel provides a potentially important modification that requires nonlinear study. If sufficiently efficient,
axion production can alter the division of dark matter between Winos and
axions and enhance the dark-radiation abundance.
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All authors Gordon Kane, Leia Price, Luis Rufino, Scott Watson, Fred Adams
Solar and Stellar Astrophysics
Super-Chandrasekhar white dwarfs by the evolution of magnetized main-sequence stars: New mass-limits from STARS simulation
Zenia Zuraiq, Banibrata Mukhopadhyay, Achal Kumar et al. (+4 more)
We explore the time
evolution of the magnetized main-sequence
stars (MSs) to magnetized non-rotating white dwarfs (WDs) with a series of models, capturing modified Hertzsprung-Russell diagram. We use the Cambridge Stellar
evolution code,
STARS, with modifications by introducing
magnetic effects and cooling. We investigate the possible existence of stable, magnetized, massive, super-Chandrasekhar, approximately spherical WDs, away from Chandrasekhar's mass-radius curve. These we refer to as B-WDs. They are inferred from the observations of peculiar over-luminous type Ia
supernovae, e.g. SN2003fg. We show that the classical effects of
magnetic fields significantly impact MSs and their time
evolution to WDs. Moreover, the
magnetic field could be decisive in explaining the unusually large radius observed in some sub-Chandrasekhar WDs, e.g. SDSS J123204.19+522548.2, along with the finite temperature effect. We further investigate the stability of magnetized WDs, both below and above the Chandrasekhar limit and confirm the possibility of super-Chandrasekhar B-WDs with new mass limits that depend on the
magnetic field geometry, mass
accretion from a companion and cooling rates. Therefore, while the "Chandrasekhar limit" may be sacrosanct, its value severely depends on the underlying physics, here the
magnetic field.
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All authors Zenia Zuraiq, Banibrata Mukhopadhyay, Achal Kumar, Arnab Sarkar, Alexander J. Hackett, Projjwal Banerjee, Christopher A. Tout
Astrophysics of Galaxies
Low-power jet-ISM coupling and disk-plane perturbations in the edge-on Seyfert galaxy NGC 4388
M. Ceci, G. Venturi, C. Marconcini et al. (+26 more)
Active galactic
nuclei (AGN) may regulate
galaxy evolution through radiatively driven winds and collimated jets, but their relative impact and coupling to the interstellar medium (ISM) remain uncertain. We investigate the ionized gas in the nearby ($D\sim$ 17 Mpc) Seyfert 2
galaxy NGC 4388, hosting a
galaxy-scale ($\sim$1.6 kpc), low-power ($\sim1.4~\times~10^{42}~erg~s^{-1}$) bipolar
radio jet projected roughly perpendicular to its edge-on disk. We analyze optical integral-field spectroscopic observations from the Wide Field Mode with adaptive optics of VLT/MUSE, complemented by VLA
radio data tracing the jet. We map ionized-gas emission, kinematics, excitation, and dust attenuation. We reconstruct the de-projected 3D outflow geometry and velocity field using the MOKA3D kinematic model, and estimate its mass and energetics. The ionized gas shows a rotating disk and a kpc-scale biconical outflow. We measure a total ionized outflow mass of $\sim10^6~M_\odot$, a mass outflow rate of $\sim0.2~M_\odot$~yr$^{-1}$, and a kinetic power of $\sim3\times10^{40}~erg~s^{-1}$, which gives a coupling efficiency of $\sim1\%$ relative to both the jet kinetic and the radiation-driven nuclear wind power, indicating that either mechanism could drive the outflow. We detect an extended ($\sim$2 kpc) enhancement of the gas velocity dispersion along the
galaxy disk plane, oriented perpendicular to the outflow and jet axes. These regions show optical line ratios consistent with shock excitation. The spatial correspondence with ALMA CO(2-1) emission is marginal, while enhanced stellar velocity dispersion prevents an exclusive jet interpretation. We report the first observational evidence that even a low-power
radio jet oriented nearly perpendicular to the
galaxy disk can efficiently couple with the ISM, suggesting that jet-induced perturbations are an important AGN feedback channel regardless of jet orientation.
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All authors M. Ceci, G. Venturi, C. Marconcini, M. V. Zanchettin, G. Cresci, M. Tartėnas, K. Zubovas, E. Treister, E. Amenta, E. Bertola, F. Belfiore, C. Bracci, E. Cataldi, Q. D'Amato, A. Feltre, M. Ginolfi, I. Lamperti, F. Mannucci, A. Marconi, A. Marasco, M. Meenakshi, M. Mingozzi, B. Moreschini, D. Mukherjee, E. Nardini, M. Perna, F. Ricci, M. Scialpi, L. Ulivi
Astrophysics of Galaxies
Galaxy-SMBH co-evolution in 2,435 DESI disk galaxies and merger-free BH growth in bulgeless disks
Sophie M. Jewell, Rebecca J. Smethurst, Chris J. Lintott et al. (+8 more)
We analyse black hole scaling relations for disk-dominated
galaxies, and present evidence for secularly driven
galaxy-black hole co-
evolution. We do this observationally by looking at “bulgeless”
galaxies, where the lack of a stellar bulge suggests a quiet merger history. We first compose a sample of 2,435 disk-dominated
galaxies hosting optical broad line active galactic
nuclei (AGN) from DESI data, and find a $M_{\mathrm{BH}}$–$M_{*}$ scaling relation of $\log(M_{\mathrm{BH}})= - 3.7^{+0.3}_{-0.3} + 1.00^{+0.03}_{-0.03} \log(M_*)$. From these, we identify 546 bulgeless
galaxies hosting AGN, a factor of $\gtrsim 5$ larger than pre-existing samples, and find they follow the same $M_{\mathrm{BH}}$–$M_{*}$ relation as the general disk
galaxy sample. Comparing the bulgeless
galaxies to those with some bulge component, we find good agreement in the $M_{\mathrm{BH}}$–$M_{*}$ relation (within $3 \sigma$), but disagreement in the $M_{\mathrm{BH}}$–$M_{*, \mathrm{bulge}}$ relation (at $>7 \sigma$). This is the opposite of what is expected from merger-driven co-
evolution, suggesting secular growth is significant in establishing observed $M_{\mathrm{BH}}$–$M_{*}$ scaling relations. Furthermore, in a control sample of early-type
galaxies we find tentative evidence of increased AGN luminosity compared to the bulgeless sample, but no statistical difference in black hole mass. This suggests the assumed merger-dominated evolutionary history of early-type
galaxies does not lead to significantly increased long-term BH growth. These results support numerous recent observational and theoretical studies which suggest secular processes fuel significant supermassive black hole growth and
galaxy-black hole co-
evolution.
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All authors Sophie M. Jewell, Rebecca J. Smethurst, Chris J. Lintott, Brooke D. Simmons, Ricarda S. Beckmann, Izzy L. Garland, Tobias Géron, Benne W. Holwerda, Karen L. Masters, Ragadeepika Pucha, Ashley Spindler
Astrophysics of Galaxies
Direct imaging of sub-parsec binary SMBHs in the central galaxy of the NGC 5044 group
Francesco Ubertosi, Gerrit Schellenberger, Ewan O'Sullivan et al. (+7 more)
Binary active galactic
nuclei (AGN) consist of two supermassive black holes (SMBHs) hosted in a single
galaxy that are simultaneously accreting gas. These systems are key to understanding hierarchical
galaxy evolution and represent
prime targets for low-frequency gravitational wave (GW) experiments. However, binary AGN remain extremely rare: only a handful are confirmed at separations of a few hundred parsecs, and just one pc-scale binary - in an elliptical
galaxy at the center of a
galaxy cluster - has been securely and visually identified. Direct imaging of sub-parsec binary AGN, the final stage before the GW regime, has so far been missing. Here we report on Very Long Baseline Array (VLBA) observations of NGC 5044, the central
galaxy of the X-ray brightest
galaxy group. This
galaxy is known to exhibit pc-scale
radio jets nearly orthogonal to two older AGN outbursts. The 4.9, 8.4, 15.2, and 23.6 GHz VLBA images reveal two compact, flat-spectrum, and variable
radio cores separated by just 0.38 parsec at the heart of the
galaxy, forming the tightest directly imaged binary AGN known by an order of magnitude. This discovery suggests that the older outbursts may have been powered by jets from the secondary core, without invoking any reorientation of the primary jet axis. More broadly, comparison with other systems points to massive, cluster-central elliptical
galaxies being promising targets to search for binary SMBHs.
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All authors Francesco Ubertosi, Gerrit Schellenberger, Ewan O'Sullivan, Laurence P. David, William Forman, Simona Giacintucci, Christine Jones, Kamlesh Rajpurohit, Tiziana Venturi, Jan Vrtilek