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Physics Astrophysics

astro-ph Watch Astrophysics

Friday 16 January

Astrophysics of Galaxies

Star-forming compact groups: Tracing the early evolutionary stages of compact group environments

Ortiz-Gómez S., Torres-Flores S., Monachesi A. et al. (+13 more)

In the context of pre-processing – a scenario in which galaxies quench their star formation within substructures before falling into clusters – we investigate the impact of environment on the physical and morphological properties of galaxies in Compact Groups (CGs), focusing specifically on a sample of Star-Forming Compact Groups (SFCGs). Our aim is to characterize the physical and morphological properties of galaxies in SFCGs, analogues of the Blue Infalling Group, and to understand how the environment influences their evolution. We use photometric techniques to derive stellar masses and star formation rates (SFRs). Morphological parameters are extracted from DECaLS images, obtaining parametric properties such as the Sérsic index ($n$) and effective radius ($R_{\mathrm{e}}$) using GALFITM, as well as non-parametric indices – including the Gini coefficient, $M_{20}$, and asymmetry – from the same data. These indicators allow us to classify galaxies into E/S0/Sa, Sb/Sc/Ir, and merger types. All measurements are compared to a control sample of field galaxies to assess environmental effects. We find no significant differences in $n$ and $R_{\mathrm{e}}$ between SFCG and field galaxies, in contrast to results reported for other CG samples. However, SFCG galaxies exhibit higher specific star formation rates (sSFRs) than their field counterparts. Approximately $16\%$ of SFCG galaxies show merger features and elevated asymmetry. These mergers also present enhanced SFRs compared to both other SFCG types and the field population. We propose that SFCGs represent an earlier evolutionary phase of CGs, supported by their lower velocity dispersions and moderate crossing times, in addition to the observed SFR enhancement and the absence of pronounced morphological transformation. Galaxy mergers in this phase appear to enhance, rather than suppress, star formation.
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All authors Ortiz-Gómez S., Torres-Flores S., Monachesi A., Montaguth G. P., Véliz Astudillo S., Mendes de Oliveira C., Olave-Rojas D. E., Lima-Dias C., Demarco R., Pallero D., Lopes A. R., Cortesi A., Telles E., Kanaan A., Ribeiro T., Schoenell W

Earth and Planetary Astrophysics

Central flashes during stellar occultations. Effects of diffraction, interferences, and stellar diameter

Bruno Sicardy and Luc Dettwiller

Central flashes occur during stellar occultations by solar system objects. We catalog diffraction effects on the flash with point-like stars, monochromatic waves and spherical transparent atmosphere. Diffraction involves the Huygens principle, the Sommerfeld lemma and the stationary phase method, while finite stellar diameter cases involve Clausius' theorem. For point-like stars, the central flash shape is that of the classical Poisson spot, but with larger height. For tenuous atmospheres that cannot focus the stellar rays at shadow center, the flash is amplified by the factor (R_0/r_0)^2 compared to the Poisson spot, where R0 and r0 are the object and the shadow radii, respectively. For denser atmospheres that can focus the rays at shadow center, the flash peaks at 2[(pi*R/lambda_F})^2]*phi0, where R is the central flash layer radius, lambda_F is the Fresnel scale and phi0 is the flux that would be observed at shadow center without focusing. For isothermal atmospheres with scale height H, the height is 2(R*H)(pi/lambda_F)^2. Fringes surrounding the central flash are separated by lambda_P=lambda_F^2/R, related to the separation between the primary and secondary stellar images. For a projected stellar diameter D*>lambda_P, the flash is described by complete elliptic integrals, and has full width at half maximum of 1.14D* and peak value 8H/D*. For Earth-based occultations by Pluto and Triton observed in the visible with point-like stars, diffraction causes flashes with very large heights ~10e4-10e5, spread over a very small meter-sized region in the shadow plane. In practice, the flash is usually smoothed by the stellar diameter, but still reaches high values of ~50 and ~200 during Pluto and Triton occultations, respectively. Diffraction dominates when using millimeter wavelengths or longer. Effects of departure from sphericity, atmospheric waves and stellar limb darkening are discussed.
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Cosmology and Nongalactic Astrophysics

Constraining the inflaton potential with gravitational waves from oscillons

Kaloian D. Lozanov, Misao Sasaki and Jan Tränkle

Under certain conditions, the oscillating inflaton condensate filling the Universe after inflation can fragment and form so-called oscillons. These long-lived soliton-like field configurations can dominate the Universe for several $e$-folds of expansion, leading to an early matter-dominated phase preceding the standard radiation era. In this paper we show how the rapid final decay of the oscillons leads to an enhanced production of induced gravitational waves, whose energy density can saturate the observational bound on the effective number of relativistic species. We leverage this bound to constrain the inflaton mass, cubic, and quartic self-coupling in generic models that admit oscillon formation, providing novel and complementary constraints in regions of parameter space that are inaccessible with cosmic microwave background observations alone.
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Solar and Stellar Astrophysics

Rescaling Transforms for Local Models of Spherical Flows

Elliot M. Lynch and Guillaume Laibe

Previously we developed a local model for a spherically contracting/expanding gas cloud that can be used to study turbulence and small scale instabilities in such flows. In this work we generalise the super-comoving variables used in studies of cosmological structure formation to our local spherical flow model, which make it significantly easier to derive analytical solutions and analyse the interactions of more complex flows with the background. We show that a wide class of solutions to the local spherical flow model can be obtained via a mapping from the corresponding solutions in regular Cartesian flows. The rescaling of time in the transformation results in a modification of the linear instabilities that can occur in spherical flows, causing them to have a time dependent growth rate in the physical time coordinate, and can prevent slower instabilities from operating. Finally, we show that the small scale flows in isotropic contraction/expansion can be mapped directly to Cartesian, inviscid, incompressible hydrodynamics, meaning that one expects a form of rescaled Kolmogorov-turbulence at the small scale of isotropically contracting/expanding flows.
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Astrophysics of Galaxies

Extragalactic planetary nebulae – tracers of kinematics and stellar populations out to 100 Mpc

Johanna Hartke, Magda Arnaboldi, Claudia Pulsoni et al. (+11 more)

Extragalactic planetary nebulae (xPNe) in galaxies beyond the Local Universe serve as discrete tracers for studying the element abundances and kinematics of galaxies covering a wide range of morphologies and masses at a variety of angular distances, from the centre well out into their haloes. They are direct stellar probes to identify the galaxy progenitors of haloes and the intracluster light. Even with new facilities, reaching higher angular resolution and sensitivity, xPNe are the only stellar tracers that can be directly and singularly detected and characterised out to 100 Mpc distance, making them crucial for tracing halo and intracluster light assembly. New wide-field spectroscopic instruments at 10+meter-class telescopes will allow the unprecedented characterisation of xPN populations from galaxy centres to their diffuse outskirts. Panoramic integral-field spectroscopy will enable the simultaneous study of xPN and stellar population properties, establishing their use as age- and metallicity-tracers while also improving post-AGB stellar evolution models.
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All authors Johanna Hartke, Magda Arnaboldi, Claudia Pulsoni, Souradeep Bhattacharya, Martin Bureau, Enrico Congiu, Guy Flint, Ortwin Gerhard, Martin Roth, Azlizan Soemitro, Chiara Spiniello, Lucas Valenzuela, Peter Weilbacher, Nancy Yang

Earth and Planetary Astrophysics

Aligned, Misaligned and Polar Orbits of Hot Jupiters: Measuring Spin-Orbit Angles via Doppler Tomography with HARPS-N

Z. Balkóová, J. Žák, M. Skarka et al. (+4 more)

Although the migration of hot Jupiters is not yet fully understood, measurements of the projected spin-orbit angle {\lambda} help shed light on the processes involved. Here we present Doppler tomography of three known hot Jupiters to determine their {\lambda} orientation: HAT-P-49 b, HAT-P-57A b, and XO-3A b. Our analysis explores the impact of cross-correlation processing methods on the detectability and characterization of the planet's Doppler shadow using up to three independent routines for cross-correlation functions extraction; those being: Yabi, iSpec and IRAF. After accounting for differences among the results obtained with the various routines, we report: first, the HAT-P-49 system is a case of a hot Jupiter on a polar orbit with {\lambda}=-85.3{\pm}1.7{\deg}, second, HAT-P-57A indicates practically no deviation of the planet's projected orbit from the host's equatorial plane with {\lambda}=-0.4^{+1.4}_{-1.9}{\deg}, and third, the XO-3A system with the measured value of {\lambda}=38{+3}_{-4}{\deg} lies in between an aligned and a perpendicular orientation, which is a less populated region of the spin-orbit distribution. Our findings highlight both the diversity of spin-orbit angles among close-in giant planets and the potential discrepancies in their measurement that can arise from different approaches to constructing the cross-correlation functions.
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All authors Z. Balkóová, J. Žák, M. Skarka, E. Knudstrup, P. Gajdoš, A. Bignamini, P. Kabáth

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

Light Dark Matter Search with 7.8 Tonne-Year of Ionization-Only Data in XENONnT

E. Aprile, J. Aalbers, K. Abe et al. (+174 more)

We report on a blinded search for dark matter (DM) using ionization-only (S2-only) signals in XENONnT with a total exposure of $7.83\mathrm{tonne}\times\mathrm{year}$ over 579 days in three science runs. Dedicated background suppression techniques and the first complete S2-only background model in XENONnT provide sensitivity to nuclear recoils of [0.5, 5.0] $\mathrm{keV_\mathrm{nr}}$ and electronic recoils of [0.04, 0.7] $\mathrm{keV_\mathrm{ee}}$. No significant excess over the expected background is observed, and we set 90% confidence level upper limits on spin-independent DM–nucleon and spin-dependent DM–neutron scattering for DM masses between 3 and 8 $\mathrm{GeV}/c^2$, as well as on DM–electron scattering, axion-like particles, and dark photons, improving on previous constraints. For spin-independent DM–nucleon scattering, we exclude cross sections above $6.0\times10^{-45} $cm$^2$ at a DM mass of 5 $\mathrm{GeV}/c^2$, pushing the XENONnT sensitivity closer to the region where coherent elastic neutrino-nucleus scattering ($\text{CE}\nu\text{NS}$) becomes an irreducible background.
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All authors E. Aprile, J. Aalbers, K. Abe, M. Adrover, S. Ahmed Maouloud, L. Althueser, B. Andrieu, E. Angelino, D. Antón Martin, S. R. Armbruster, F. Arneodo, L. Baudis, M. Bazyk, V. Beligotti, L. Bellagamba, R. Biondi, A. Bismark, K. Boese, R. M. Braun, G. Bruni, G. Bruno, R. Budnik, C. Cai, C. Capelli, J. M. R. Cardoso, A. P. Cimental Chávez, A. P. Colijn, J. Conrad, J. J. Cuenca-García, V. D'Andrea, L. C. Daniel Garcia, M. P. Decowski, A. Deisting, C. Di Donato, P. Di Gangi, S. Diglio, K. Eitel, S. el Morabit, R. Elleboro, A. Elykov, A. D. Ferella, C. Ferrari, H. Fischer, T. Flehmke, M. Flierman, R. Frankel, D. Fuchs, W. Fulgione, C. Fuselli, F. Gao, R. Giacomobono, F. Girard, R. Glade-Beucke, L. Grandi, J. Grigat, H. Guan, M. Guida, P. Gyorgy, R. Hammann, C. Hils, L. Hoetzsch, N. F. Hood, M. Iacovacci, Y. Itow, J. Jakob, F. Joerg, Y. Kaminaga, M. Kara, S. Kazama, P. Kharbanda, M. Kobayashi, D. Koke, K. Kooshkjalali, A. Kopec, H. Landsman, R. F. Lang, L. Levinson, A. Li, I. Li, S. Li, S. Liang, Z. Liang, Y.-T. Lin, S. Lindemann, M. Lindner, K. Liu, M. Liu, F. Lombardi, J. A. M. Lopes, G. M. Lucchetti, T. Luce, Y. Ma, C. Macolino, G. C. Madduri, J. Mahlstedt, F. Marignetti, T. Marrodán Undagoitia, K. Martens, J. Masbou, S. Mastroianni, V. Mazza, A. Melchiorre, J. Merz, M. Messina, A. Michel, K. Miuchi, A. Molinario, S. Moriyama, M. Murra, J. Müller, K. Ni, C. T. Oba Ishikawa, U. Oberlack, S. Ouahada, B. Paetsch, Y. Pan, Q. Pellegrini, R. Peres, J. Pienaar, M. Pierre, G. Plante, T. R. Pollmann, F. Pompa, A. Prajapati, L. Principe, J. Qin, D. Ramírez García, A. Ravindran, A. Razeto, R. Singh, L. Sanchez, J. M. F. dos Santos, I. Sarnoff, G. Sartorelli, J. Schreiner, P. Schulte, H. Schulze Eißing, M. Schumann, L. Scotto Lavina, M. Selvi, F. Semeria, F. N. Semler, P. Shagin, S. Shi, H. Simgen, Z. Song, A. Stevens, C. Szyszka, A. Takeda, Y. Takeuchi, P.-L. Tan, D. Thers, G. Trinchero, C. D. Tunnell, K. Valerius, S. Vecchi, S. Vetter, G. Volta, B. von Krosigk, C. Weinheimer, M. Weiss, D. Wenz, C. Wittweg, V. H. S. Wu, Y. Xing, D. Xu, Z. Xu, M. Yamashita, J. Yang, L. Yang, J. Ye, M. Yoshida, L. Yuan, G. Zavattini, Y. Zhao, M. Zhong, T. Zhu

Earth and Planetary Astrophysics

Detection of four cold Jupiters through combined analyses of radial velocity and astrometry data

Yiyun Wu, Guang-Yao Xiao, R. Paul Butler et al. (+19 more)

Cold Jupiters play a crucial role in planet formation and dynamical evolution. Since their initial discovery around 47 UMa, they have attracted significant interest, yet their formation mechanisms remain uncertain, underscoring the need to expand the known population. In this work, we combine RV data with Gaia astrometry using Hipparcos-Gaia proper-motion anomalies over a 25-year baseline. By jointly modeling both datasets with the MCMC framework, we constrain planetary masses, orbital inclinations, and three-dimensional orbital architectures. This reduces RV degeneracies and improves mass determinations. Four cold Jupiters are reported: HD 68475 b and HD 100508 b are each the first confirmed planet in their systems, with orbital periods $7832_{-323}^{+463}$ d and $5681\pm42$ d and dynamical masses of $5.16_{-0.47}^{+0.53} M_{\text{Jup}}$ and $1.2_{-0.18}^{+0.30} M_{\text{Jup}}$, respectively. In multi-planet systems, HD 48265 c has a period of $10418_{-1400}^{+2400}$ d and a mass of $3.71_{-0.43}^{+0.68} M_{\text{Jup}}$, while HD 114386 c orbits at $444.00_{-0.88}^{+0.93}$ d with a minimum mass of $0.37 \pm 0.03 M_{\text{Jup}}$. The two planets in the HD 48265 system may exhibit a significant mutual inclination, making it a target for testing the von-Zeipel-Kozai-Lidov mechanism. HD 68475 b is a promising candidate for future direct imaging with ELT/METIS. We identified a Jupiter analog with the longest known orbital period among planets with masses between 0.5 and 2 $M_{\text{Jup}}$, implying that a substantial population of cold Jupiters likely awaits discovery by Gaia. This study expands the sample of cold Jupiters with constrained orbits and dynamical masses, demonstrating the value of combining radial velocity and astrometry in exoplanet research.
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All authors Yiyun Wu, Guang-Yao Xiao, R. Paul Butler, Fabo Feng, Stephen A. Shectman, Jeffrey D. Crane, Johanna K. Teske, Sharon X. Wang, Yuri Beletsky, Jennifer A. Burt, Tansu Daylan, Matias Diaz, Diana Dragomir, Erin Flowers, Sydney Jenkins, Shubham Kanodia, Sangeetha Nandakumar, Malena Rice, Avi Shporer, Sam Yee, George Zhou, Zitao Lin

High Energy Astrophysical Phenomena

Intermittent Turbulence, Fast Flavor Conversion, and Observable Supernova Probes

Yiwei Bao and Andrea Addazi

Fast flavor conversion (FFC) in core-collapse supernovae is usually analyzed in homogeneous backgrounds or with smooth stochastic turbulence closures. We construct an exact linear benchmark in which the matter-noise memory kernel is instead generated by a finite She–Leveque log-Poisson cascade. Projecting the marginal FFC channel onto this kernel gives a causal Volterra equation whose non-Markovian memory closes into a finite local system. The resulting Laplace-space resolvent is rational, with one pole pair for each cascade level, so the dispersion relation, characteristic polynomial, and time-domain solution can be checked analytically. We then connect this benchmark to the realization-level toy model and gain-region heating proxy used in the supplementary derivation. For the updated intermittent choice $\delta\rho/\langle\rho\rangle=0.4$, $\bar\lambda/\mu=1$, and hence $\kappa_0=0.16$, the representative $N=2$, $r=2$ cascade gives $\sigma_{\rm int}^2=1.124$ and an intermittent conversion fraction $1-P_{\rm base}\simeq0.455$. The older weaker normalization $\kappa_0=0.05$ gives $1-P_{\rm base}\simeq0.324$. The corresponding Mori-like heating ratios are $Q_{\rm int}/Q_{\rm hom}=1.060$ and $1.041$, whereas the Wang/Fornax-like ratios are $0.855$ and $0.899$. Thus intermittency mainly controls the conversion fraction, while the neutrino spectral hierarchy controls the sign of the heating correction.
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Cosmology and Nongalactic Astrophysics

Cluster number counts in dark energy model with energy and momentum coupling to dark matter

Chattree Wongsangwal, Khamphee Karwan, Stharporn Sapa et al. (+1 more)

The influences on the cluster number counts from the coupling between dark energy and dark matter with momentum transfer are investigated. We find that the extrapolated linear density contrast computed from the spherical collapse model is suppressed when the strength of momentum transfer is increased. Using the Sheth-Tormen mass function, the cluster number counts are computed. The minimum mass limit in the mass integration for each redshift bin is determined by matching the predicted number counts from the $\Lambda$CDM model with the result from eROSITA surveys. We find that the number of clusters is maximal at a higher redshift bin, and the number of clusters in a maximum redshift bin is enhanced when the strength of momentum and energy transfers increases due to the reduction of extrapolated linear density contrast. Setting the parameters of the dark energy model with momentum coupling according to the observational constraints in \cite{bestfit}, the predicted number counts from the coupled dark energy is larger than the result from eROSITA surveys. The statistical analysis yields a $p$-value of 0.189 for the proposed model relative to $\Lambda$CDM. Consequently, there is no statistically significant evidence of an improved fit over the standard $\Lambda$CDM framework based on the eROSITA cluster number counts.
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All authors Chattree Wongsangwal, Khamphee Karwan, Stharporn Sapa, Teeraparb Chantavat

Instrumentation and Methods for Astrophysics

Mobile Intensity Interferometer for Stellar Observations (MI$^2$SO)

Christopher Ingenhütt, Pedro Batista, Gisela Anton et al. (+5 more)

In recent years, intensity interferometry has seen renewed interest and successful application at Imaging Atmospheric Cherenkov Telescope arrays. These measurements are usually performed during bright moon periods while the instruments' primary purpose – gamma-ray observations – cannot be fulfilled. The Mobile Intensity Interferometer for Stellar Observations was designed as a proof of concept for a purpose-built intensity interferometer. Using acrylic Fresnel lenses 1 m in diameter with 1.2 m focal length, a compact, economical and lightweight design was realised. The detector fixture allows for translation in the z-axis to adjust for measurements at different wavelengths (and therefore focal points) and easy swapping of the detector in its entirety. Both mobility and scalability in quantity of this design allow for specific targeting of projected baselines and orientations based on the target. Particularly for potential binary systems, selective coverage of a target's u-v plane is essential to probing the characteristics accurately. A first campaign demonstrated the capability of these Fresnel lens telescopes by measuring the spatial coherence curve of Arcturus ($\alpha$ Boo). In an observation time of less than 11 h, the angular diameter was measured with milliarcsecond precision, in agreement with the values in the literature.
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All authors Christopher Ingenhütt, Pedro Batista, Gisela Anton, Alison Mitchell, Naomi Vogel, Adrian Zink, Andreas Zmija, Stefan Funk

High Energy Astrophysical Phenomena · Cross-listed from gr-qc

Rapid inference of gravitational-wave signals in the time domain using a heterodyned likelihood

Neha Sharma, Aditya Vijaykumar and Prayush Kumar

Parameter estimation of gravitational wave signals is computationally intensive and typically requires millions of likelihood evaluations to construct posterior probability distributions. This computational cost increases significantly in the time domain, which requires non-diagonal covariance matrices to compute the likelihood. Consequently, parameter estimation of long-duration gravitational wave signals, such as binary neutron star mergers, becomes computationally infeasible in time domain. In this work, we detail a framework for the heterodyned likelihood that enables rapid inference in the time domain. Our method is applicable to signals with arbitrary mode content, and leverages the smoothness of the ratio of complex-valued waveform modes, approximating the ratio as a linear function within appropriately chosen time bins. This allows downsampling of the waveform modes and a reformulation of the likelihood, such that it depends only on the bin edges. We demonstrate that this likelihood recovers posteriors that are indistinguishable from those obtained using the standard likelihood in the time domain. We also observe dramatic improvement in speed - for a 128 seconds-long gravitational wave signal, our method is at least $\sim 400$ times faster than the standard time-domain analysis, reducing the wall clock time to just a few hours. We also demonstrate the reliability and unbiasedness of the likelihood using percentile-percentile tests for binary black hole and binary neutron star injections. We use the Gohberg-Semencul representation of the inverse of Toeplitz covariance matrix to accelerate matrix-vector products, which has potential applications even in non heterodyned time-domain inference.
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Cosmology and Nongalactic Astrophysics

KiDS-Legacy: WIMP dark matter constraints from the cross-correlation of weak lensing and Fermi-LAT gamma rays

Shiyang Zhang, Hendrik Hildebrandt, Ziang Yan et al. (+13 more)

Dark matter dominates the matter content of the Universe, and its properties can be constrained through large-scale structure probes such as the cross-correlation between the unresolved gamma-ray background (UGRB) and weak gravitational lensing. We analysed 15 years of Fermi-LAT data, constructing UGRB intensity maps in ten energy bins (0.5-1000 GeV), and cross-correlated them with KiDS-Legacy shear in six tomographic bins. The measurements were performed using angular power spectra estimated with the pseudo-$C_\ell$ method. No significant cross-correlation is found. Based on this non-detection, we present 95% upper bounds on the weakly interacting massive particle (WIMP) decay rate $\Gamma_{\rm dec}$ and velocity-averaged annihilation cross-section $\langle\sigma_{\rm ann} v\rangle$ as functions of mass. We compare our results with bounds from other cosmological tracers and from local probes, and found them to be complementary, particularly at low masses ($\rm GeV/TeV$). In addition, using a Euclid-like lensing survey cross-correlated with Fermi-LAT, we forecast $\sim$2 times tighter limits, highlighting the potential of forthcoming data to strengthen constraints on dark matter annihilation and decay.
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All authors Shiyang Zhang, Hendrik Hildebrandt, Ziang Yan, Tilman Tröster, Athithya Aravinthan, Marika Asgari, Deaglan J. Bartlett, Maciej Bilicki, Dominik Elsässer, Catherine Heymans, Benjamin Joachimi, Lauro Moscardini, Dennis Neumann, Anya Paopiamsap, Robert Reischke, Benjamin Stölzner

Astrophysics of Galaxies

Deep Submillimeter and Radio Observations in the SSA22 Field. III. Multiwavelength Identifications and Properties of the 850 $\mu$m-selected Submillimeter Galaxies

Xin Zeng, Yiping Ao, Zongfei Lyu et al. (+4 more)

We present a multiwavelength analysis of 850 $\mu$m-selected SMGs (deblended S$_{\rm 850}\gtrsim$ 1mJy) in the SSA22 field, where our deepest JCMT/SCUBA-2 observations reach a sensitivity of $\sigma_{850}\sim$ 0.80mJy beam$^{-1}$. Using multiple identification methods, we have identified 248 deblended SMG candidates for 192 SCUBA-2 sources. The average multiplicity of SCUBA-2 sources is $\sim$26%, with brighter sources exhibiting higher multiplicity. After applying quality cuts based on SED fitting reliability, our final sample comprises 221 SMGs associated with 186 SCUBA-2 sources. The SSA22 SMGs have a median infrared luminosity of (2.25$\pm$0.25) $\times$10$^{12}$ L$_{\odot}$, with $\sim$ 63% ($\sim$ 8%) of the sample classified as ULIRGs (HLIRGs). The median redshift of the sample is $z = 2.00 \pm 0.08$, while optically faint galaxies exhibit higher median redshift ($\sim 2.20 \pm 0.17$). The comoving volume density of SMGs increases by a factor of $\sim 6$ at $z \lesssim 4$, plateauing at $\sim$ 1.78-3.16 $\times$ 10$^{-5}$ cMpc$^{-3}$ over $z \sim$ 1-3 (including the overdensity). The significant overdensity of SMGs within large-scale structures demonstrates their reliability as tracers of cosmic structure formation at high redshift. The median stellar mass and SFR of our SMG sample are $(1.55 \pm 0.22) \times 10^{11}$ M$_\odot$ and $166 \pm 25$ M$_\odot$ yr$^{-1}$, respectively. We observe a clear “downsizing" signature: after cosmic noon ($z \lesssim 2$), massive SMGs exhaust their gas reservoirs and transition to quiescence, while lower-mass SMGs continue forming stars and dominate the cosmic SFR density. The sample has a median dust mass of (1.95 $\pm$ 0.14) $\times$ 10$^{9}$ M$_{\odot}$. The dust fraction ($ M_{\text{dust}}/M_{\text{star}}$) has a median value of (1.4 $\pm$ 0.2) $\times$ 10$^{-2}$. The median $A_V$ of SMGs is 3.09$\pm$0.07mag.
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All authors Xin Zeng, Yiping Ao, Zongfei Lyu, Daizhong Liu, Emanuele Daddi, Ken Mawatari, Hideki Umehata

High Energy Astrophysical Phenomena

Little Red Dots as Hidden Neutrino Sources

Riku Kuze, Kunihito Ioka, Kohta Murase et al. (+2 more)

Little Red Dots (LRDs) are enigmatic, compact, red galaxies at high redshift, $z\sim 4$-$7$, discovered by the James Webb Space Telescope. Broad emission lines in the absence of X-ray and radio counterparts suggest that they host accreting supermassive black holes embedded in dense gaseous envelopes. This black-hole-envelope configuration facilitates efficient photohadronic interactions and neutrino production. Remarkably, their observed source number density and luminosity are compatible with the energetics of the diffuse neutrino background. We consider that relativistic jets and outflows are launched from the black hole and propagate through low-density polar funnels within envelopes, where particle acceleration and neutrino emission occur. This leads to LRDs being effectively hidden sources. Our analytic and numerical calculations show that, in an optimistic scenario, LRDs can contribute $\sim 30\%$ of the observed diffuse background at TeV$-$sub-PeV energies, predominantly through photomeson production. At high neutrino energies, $\gtrsim 10^{5.5}~{\rm GeV}$, inverse-Compton cooling of muons modifies the resulting flavor ratio, providing a distinctive diagnostic for IceCube-Gen2 and other upcoming neutrino telescopes.
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All authors Riku Kuze, Kunihito Ioka, Kohta Murase, Shigeo S. Kimura, Kohei Inayoshi

Instrumentation and Methods for Astrophysics

The test and calibration system for the Elementary Cells of the Cherenkov Camera in the PBR Mission

Rossella Caruso

The development of detectors using Silicon Photo-Multipliers for acquisition of fast light signals coming from Cherenkov and fluorescence emissions started by particle showers in the terrestrial atmosphere is the main goal of the Italian ASI/INFN Agreement n.2021-8-HH.2-2022, named "ASI/INFN_EUSO-SPB2", in view of the next generation of telescopes in balloon-borne and space-based experiments. A survey of performances of different Silicon Photo-Multipliers available on the market has been performed to identify the best sensors for space applications, where high thermal excursions and environmental radiation must be mainly taken into account in contrast to ground-based experiments. In particular, a characterization protocol for Silicon Photo-Multiplier qualification has been specified to Hamamatsu S13161-3050AE-08 sensor ($8 \times 8$) array in the $30 \, \textrm{C}^{\circ}$ down to $-40 \, \textrm{C}^{\circ}$ temperature range. The protocol specifies measurements of break-down voltage, quenching resistance, gain, dark count rate and the probability of cross-talk. These parameters have been measured as a function of temperature at fixed over-voltage. Based on these previous measurements, a dedicated set-up is under completion for performing massive tests to validate and calibrate 32 Silicon Photo-Multipliers (Hamamatsu S13361-3050 series, 64 channels each), composing the (2048 pixels, $12^{\circ} \times 6^{\circ}$ field of view) Focal Surface of the Cherenkov Camera that will fly on the POEMMA-Balloon with Radio mission. The technical details and description of this system and the procedural steps implemented are reported, preliminary measurements on the first Elementary Cell are also shown.
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Solar and Stellar Astrophysics

Spectral evolution of hot hybrid white dwarfs: II. Photometry

Semih Filiz, Nicole Reindl, David Jones et al. (+4 more)

We present a photometric analysis of 19 DA and 13 DAO white dwarfs (WDs) with effective temperatures exceeding 60 kK, building on the spectral analysis reported in the first paper of this two-part study. By examining archival light curves for periodic signals, we identify that four of the 32 objects ($13^{+8}_{-4}$%) exhibit photometric variability. Spectral energy distribution (SED) fitting allowed us to derive radii, luminosities, and gravity masses, as well as to characterise the infrared excesses observed in six sources. A notable discovery is the identification of a 1.87 d period in the ZTF light curves of WD1342+443 and weak emission lines in the optical spectra of this star, which strongly indicate an irradiation effect system. Our SED fit indicates the presence of cool dust, which must be located farther from the star, and that any companion with a spectral type earlier than L2.0 would appear in the SED. This leads us to speculate that WD1342+443 might have an irradiated, sub-stellar companion. We also highlight that we uncovered, for the first time, a 4.23 d photometric period in the well-known, close DA+dM binary WD0232+035, based on TESS data. We find that the phase and amplitude of the light curve variations are consistent with expectations from an irradiation effect. Intriguingly, we detected an additional, mysterious period at 1.39 d, which is approximately one-third of the orbital period. Moreover, we revisited the longstanding discrepancy between Kiel and gravity masses for the hottest WDs. To address this, we explored fully metal line blanketed model atmospheres as a potential solution, contrasting them with the results from pure H and H+He models. Our results show that including metal opacities does not resolve the discrepancy - in fact, it slightly deteriorates the agreement. Finally, we reaffirm the previously observed correlation between He abundance and luminosity.
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All authors Semih Filiz, Nicole Reindl, David Jones, Paulina Sowicka, Matti Dorsch, Thomas Rauch, Klaus Werner

Solar and Stellar Astrophysics · Cross-listed from nucl-th

Fine-tunings in radiative $\alpha$-particle capture on $^{12}$C at astrophysical energies

Ulf-G. Meißner, Bernard Ch. Metsch and Helen Meyer

We investigate the fine-tuning of radiative alpha-particle capture on carbon, $\alpha(^{12}{\rm C},^{16}{\rm O})\gamma$, at astrophysical energies. Utilizing results from cluster effective field theory for this reaction, we find that the low-energy data of the astrophysical S-factor allow for only very small variations in the electromagnetic fine-structure constant $\alpha$, namely $|\delta \alpha/\alpha| \leq 0.2\,$ per mille, in both the $E1$ and the $E2$ radiative capture.
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Astrophysics of Galaxies

Deep Submillimeter and Radio Observations in the SSA22 Field. IV. Spectral Energy Distributions, Star Formation Histories, and the Infrared-Radio Correlation of the 850 $\mu$m-selected SMGs

Xin Zeng, Yiping Ao, Ken Mawatari et al. (+1 more)

We analyze the spectral energy distributions (SEDs), star formation histories (SFHs), and infrared-radio correlation (IRRC) of 221 850 $\mu$m-selected submillimeter galaxies (SMGs) in the SSA22 deep field. The median mass-weighted age is 567 Myr. Most galaxies in our sample began forming $\sim$ 1.68 Gyr after the Big Bang, entered the `SMG phase' after $\sim$ 1 Gyr of evolution – when they are predominantly observed – and largely transitioned out of the `SMG phase' to become quiescent within an additional $\sim$ 0.2 Gyr. A subset of massive galaxies shows rapid early assembly with high star formation efficiencies ($\sim$0.2-0.8). The majority of SMGs reside at the high-mass end of the star-forming main sequence, with a characteristic stellar mass of $M_{star} \sim 10^{11}$ M$_\odot$, above which galaxies are predominantly either on the main sequence or already quenched. We observe a downsizing trend: more massive galaxies tend to “mature" earlier, completing their major episodes of star formation at higher redshifts compared to lower-mass systems. Our sample contributes $\sim$ 21% (28%) to the cosmic star formation rate density (stellar mass density), including the overdensity, with its relative contribution peaking at 50-60% in the redshift range $z=2.5-3.5$. The median infrared-radio correlation parameter $q_{IR}$ is 2.37, evolving as $(1+z)^{-0.11}$, likely due to AGN contributions at high redshift and intrinsic differences between low- and high-redshift populations.
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All authors Xin Zeng, Yiping Ao, Ken Mawatari, Hideki Umehata

Cosmology and Nongalactic Astrophysics

Bayesian optimisation for Bayesian evidence (BOBE) – a fast and efficient likelihood emulator for model selection

Nathan Cohen, Jan Hamann and Ameek Malhotra

The formalism of Bayesian model selection provides a very elegant way of ranking different physical models in terms of how compatible they are with a given set of observed data. However, its practical application is often hampered by the challenge of having to compute the Bayesian evidence - a multi-dimensional integral over the product of likelihood and prior probability. This usually necessitates a large number of function calls to the likelihood, which may become prohibitive in case of "slow", costly to evaluate likelihoods. A possible solution to this problem lies in approximating the slow full likelihood by a fast emulated likelihood. In this paper, we introduce BOBE (Bayesian Optimisation for Bayesian Evidence), a method to construct a Gaussian Process Regression (GPR)-based emulator. BOBE utilises a Bayesian Optimisation algorithm designed specifically to (i) provide a realistic estimate of the emulator's uncertainty and its impact on the evidence calculation, and (ii) minimise the number of likelihood evaluations required in order to meet a given evidence accuracy goal. We apply it to a number of toy examples as well as actual cosmological likelihoods, and demonstrate that training the emulator to a sufficient accuracy takes a factor of $O(10^3)$ fewer direct likelihood evaluations than would be needed if one were to directly compute the evidence integral via nested sampling. BOBE's overhead is independent of the likelihood computation time $t_L$, making it particularly useful for "expensive" likelihoods with $t_L \gtrsim 1$~s. BOBE is written in Python, supports MPI parallelisation, takes advantage of automatic differentiation and just-in-time-compilation provided by JAX, can straightforwardly be implemented with cosmological data analysis frameworks such as Cobaya, and is available for download from https://github.com/Ameek94/BOBE.
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Cosmology and Nongalactic Astrophysics

Study of the anisotropy of cosmic expansion on ZTF type Iasupernovae simulations

C. Barjou-Delayre, P. Rosnet, C. Ravoux et al. (+29 more)

The cosmological principle assumes the isotropy of the Universe at large scales. It is a foundational assumption in the $\Lambda$CDM model, which is the current standard model of cosmology. Recent tensions give legitimacy to investigating the possibility of anisotropies in the Universe. The large sky coverage achieved by the Zwicky Transient Facility survey (ZTF) allows us to test the veracity of the cosmological principle using observations of Type Ia supernovae (SNe Ia). In this article, we develop a methodology to measure potential anisotropies in the Hubble constant $H_0$. We test our method on realistic simulations of the second data release (DR2) of ZTF SNe Ia in which we introduce a dipole. We develop an unbiased method both to introduce a dipole in the simulations and to recover it. We test a potential $H_0$ dependency of our method while varying the dipole amplitude. We analyse the impact of introducing large-scale structures in the simulations and the efficiency of using a volume-limited sample, which is an unbiased subsample of the ZTF SNe Ia sample. Finally, we build an error model applied to the recovered dipole amplitude ($\Delta H_0$) and its direction ($\alpha_0$, $\delta_0$). Our analysis allows us to recover a dipole with an error on the amplitude of $0.33\,\mathrm{km\,s^{-1}\,Mpc^{-1}}$, and uncertainties of $3.4^\circ$ and $6.1^\circ$ on the right ascension and declination, respectively, for an initial dipole amplitude of $\Delta H_0 = 3\,\mathrm{km\,s^{-1}\,Mpc^{-1}}$. The resulting dipole is independent of the chosen $H_0$ value and sky coverage. This paper paves the way for a future precise ZTF dipole investigation.
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All authors C. Barjou-Delayre, P. Rosnet, C. Ravoux, M. Aubert, M. Ginolin, R. Kebadian, M. Amenouche, J. Bautista, U. Burgaz, B. Carreres, J. Castaneda Jaimes, G. Dimitriadis, F. Feinstein, D. Fouchez, L. Galbany, C. Ganot, M. Graham, S.L. Groom, A. Goobar, J. Johansson, M.M. Kasliwal, Y-L. Kim, T.E. Müller-Bravo, B. Popovic, B. Racine, N. Regnault, N. Rehemtulla, M. Rigault, R.L. Riddle, J. Sollerman, A. Townsend, A. Trigui

Solar and Stellar Astrophysics

Unveiling Ionized Jet Morphologies: Sub-arcsecond VLA Observations of Compact Radio Sources

Tatiana M. Rodriguez, Peter Hofner, Emmanuel Momjian et al. (+3 more)

We present sub-arcsecond ($\theta\sim0.1^{\prime\prime}$) resolution VLA 1.3 cm continuum and 22.2 GHz H$_2$O maser observations toward 15 compact radio continuum sources with rising spectral index and 8 string-like radio continuum structures in the Rosero et al. (2016, 2019) survey. Three different morphologies are observed: elongated or double-peak string-like structure (6 out of 23 cases), a collection of distinct continuum peaks (4 out of 23 cases), and single compact sources (13 out of 23 cases). The majority of H$_2$O maser spots detected are within a sky-projected distance of $\sim5,000$ au from the radio continuum peaks and tend to be well aligned and distributed in an elongated structure when more than three spots are observed. We generally recover less emission than Rosero et al. (2016, 2019), which together with the fact that more than half of the jet candidates in our survey appear mostly compact, suggest core/halo shock structures even on small scales. We also detected proper motion in 10 cases and measured an average projected velocity of approximately 120 km s$^{-1}$. Radio brightness variability is detected in at least two cases, possibly due to weak accretion bursts. This work, together with our previous molecular jet study, provides further evidence that support the main source of ionization in the studied sources is shocks, yet collimation is only observed in 4 cases. We conclude that the available data supports the thermal jet classification of 7 sources, and the ionized jet interpretation is further supported in 16 sources.
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All authors Tatiana M. Rodriguez, Peter Hofner, Emmanuel Momjian, Esteban D. Araya, Ananay Sethi, Viviana Rosero

Astrophysics of Galaxies

Molecular gas and star formation in central rings across nearby galaxies

Damian R. Gleis, Sophia K. Stuber, Eva Schinnerer et al. (+20 more)

Nearby galaxies exhibit a variety of structures, including central rings, similar to the MW Central Molecular Zone (CMZ). These rings are common in barred galaxies and can be gas-rich and highly star-forming. We aim to study molecular gas content and star formation rate of central rings within nearby galaxies and link them to global galaxy properties (e.g. bar morphology). We utilize $1\,$” resolution CO(2-1) PHANGS-ALMA observations, visually identify 20 central rings and determine their properties. For $14$ rings, SFR surface density maps are available. We derive ring geometry, integrated molecular gas masses, SFRs, depletion times, and compare them to host galaxy and bar properties. Molecular gas is a good tracer for central rings: Previous studies used ionized gas and dust tracers to identify central rings in galaxies of similar morphological types as this study. In comparison, we find similar fractions of galaxies hosting central rings and similar radii distributions. The gaseous central rings have typical radii of $400_{-150}^{+250}\,$pc, molecular gas masses of $\log(M_\text{mol}/M_\odot){\sim}8.1_{-0.23}^{+0.17}$, and SFRs of $0.21_{-0.16}^{+0.15}\,M_\odot/\text{yr}$, thus contributing $5.6_{-2.1}^{+4.5}\,\%$ and $13_{-5}^{+10}\,\%$ to their host galaxies' molecular gas mass and SFR. The MW CMZ sits at the lower end of the radius, molecular gas mass, and SFR distribution, but it has a similar molecular gas mass and SFR fraction, and depletion time. Longer bars contain more massive molecular central rings, but we find no correlation between bar strength and the ring's molecular gas content. Although absolute central ring properties likely depend on host galaxy properties, the similarities between the MW CMZ and PHANGS central rings in relative parameters suggest that the processes of gas inflow and star formation are similar for central rings across nearby galaxies.
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All authors Damian R. Gleis, Sophia K. Stuber, Eva Schinnerer, Justus Neumann, Sharon E. Meidt, Miguel Querejeta, Eric Emsellem, Adam K. Leroy, Ashley T. Barnes, Frank Bigiel, Charlie Burton, Mélanie Chevance, Daniel A. Dale, Kathryn Grasha, Ralf S. Klessen, Rebecca C. Levy, Lukas Neumann, Hsi-An Pan, Marina Ruiz-García, Mattia C. Sormani, Jiayi Sun, Yu-Hsuan Teng, Thomas G. Williams

Astrophysics of Galaxies

Discovery of a gas-enshrouded broad-line AGN at z $\sim$ 7

Qianqiao Zhou, Xin Wang, Hang Zhou et al. (+9 more)

The Lyman-alpha (Ly$\alpha$) absorption profile in star-forming galaxies serves as a powerful tracer of the extended, dense neutral hydrogen in their surroundings during the Epoch of Reionization (EoR). We report a unique galaxy, A2744-z7DLA, at $z\approx 6.87$ gravitationally lensed by the foreground galaxy cluster Abell 2744, which exhibits both moderate Ly$\alpha$ emission and damped Ly$\alpha$ absorption, suggesting the presence of a dense neutral hydrogen environment. Our analysis suggests that the UV continuum turnover near Ly$\alpha$ is more likely shaped by a damped Ly$\alpha$ system rather than nebular continuum from two photon process. We analyze the physical properties of A2744-z7DLA with spectroscopic and photometric data from the JWST and the HST. The galaxy shows a compact morphology ($r_e \sim 0.3\ {\rm kpc}$) and a broadened H$\alpha$ emission line, suggesting possible AGN activity. The broad component of H$\alpha$ has a FWHM of $2721 \pm 200\ {\rm km\ s^{-1}}$, corresponding to a black hole mass of $M_{\rm BH}=2.90^{+2.35}_{-1.28}\times 10^7 M_\odot$ and a black hole-to-stellar mass ratio of $\log (M_{\rm BH}/M_{\rm stellar}) = -1.58^{+0.45}_{-0.34}$. The Balmer decrement ($\rm H\alpha/H\beta$) yields a dust attenuation of $\rm A_V \approx 1.15 \pm 0.23$, indicating that this system is less dust-rich than some "little red dots". Furthermore, we perform SED fitting using both stellar and AGN models. The results show that the UV and optical wavelengths are dominated by star-forming regions, while the AGN component contributes primarily at longer wavelengths. This work provides new insights into the interplay between star formation, neutral gas, and potential AGN activity in galaxies during the EoR.
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All authors Qianqiao Zhou, Xin Wang, Hang Zhou, Emanuele Daddi, Luis C. Ho, Shengzhe Wang, Ruancun Li, Zuyi Chen, Cheng Cheng, Xihan Ji, Yuxuan Pang, Mengting Ju

High Energy Astrophysical Phenomena

The Role of Plasma Lensing in Fast Radio Bursts

R. N. Li, Y. B. Wang, S. X. Yi et al. (+2 more)

Growing evidence indicates that some fast radio bursts (FRBs) reside in dense, magneto-ionic environments where extrinsic propagation effects can substantially reshape the observed signal. Within a 1D Gaussian plasma-lens framework, we show that small, monotonic variations in the incidence angle of the FRB wavefront naturally generate both downward and upward sub-burst frequency drifts. We further demonstrate that distinct lensed paths that probe different rotation measures (RMs), can produce orthogonal polarization-angle (PA) jumps at gigahertz frequencies. In this picture, a $\sim 90^\circ$ PA transition requires only a modest RM contrast of order a few $\times10~\rm{rad~m^{-2}}$ between the multiple images. The chromatic activity of FRB 20180916B-earlier and narrower activity windows at higher frequencies-can be explained as preferential magnification near the outer caustic. Finally, the intrinsic resolution of a plasma lens provides an upper limit on the transverse emission size: lenses located close to the source yield magnetospheric-scale constraints and offer a practical means of discriminating between inner- and outer-magnetospheric emission scenarios. These results suggest that plasma lensing could account for multiple complex observational features of FRBs and may play a non-negligible role in modulating their observable properties.
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All authors R. N. Li, Y. B. Wang, S. X. Yi, X. Zhou, F. Y. Wang

High Energy Astrophysical Phenomena

Broadband study of the Be/X-ray binary pulsar eRASSU J012422.9-724248 in the Magellanic Bridge, near the Eastern Wing of the Small Magellanic Cloud

Haonan Yang, Chandreyee Maitra, Frank Haberl et al. (+4 more)

The first four all-sky surveys with eROSITA the soft X-ray instrument on board the Spektrum-Roentgen-Gamma (SRG) satellite revealed a new X-ray source, eRASSU J012422.9-724248, in the Magellanic Bridge, near the Eastern Wing of the Small Magellanic Cloud (SMC). We performed a broadband timing and spectral analysis using the optical and X-ray data of eRASSU J012422.9-724248. Using the X-ray observations with eROSITA, Swift, NuSTAR and optical data from the optical Gravitational Lensing Experiment (OGLE) and the Las Cumbres Observatory (LCO), we confirm the nature of eRASSU J012422.9-724248 as a Be/X-ray binary (BeXRB) pulsar in the Magellanic bridge. The position is coincident with that of an early-type star (OGLE ID SMC732.10.7). We detect the spin period at 341.71 s in NuSTAR data and infer a period of 63.65 days from the 15 year monitoring with OGLE, that we interpret as the orbital period of the system. A tentative CRSF at ~12.3 keV is identified in NuSTAR spectra with ~1.8-sigma. The source appears to show a persistent X-ray luminosity and an optical magnitude transition on the long timescale. We propose eRASSU J012422.9-724248 is a new member of the class of persistent BeXRBs.
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All authors Haonan Yang, Chandreyee Maitra, Frank Haberl, David Kaltenbrunner, Lorenzo Ducci, Andrzej Udalski, Georgios Vasilopoulos

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

Gravitational perturbations of nonlocal black holes

Rocco D'Agostino and Vittorio De Falco

We derive the master equations governing axial and polar gravitational perturbations of a generic static and spherically symmetric black hole spacetime within the framework of the revised Deser–Woodard nonlocal gravity theory. We then apply our general formalism to a one-parameter family of black hole solutions recently obtained by the present authors, representing small first-order deviations from the Schwarzschild geometry. We provide well-motivated arguments that allow us to render the analysis analytically tractable. Our results provide the first complete perturbative characterization of nonlocal black holes and lay the groundwork for future investigations.
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Astrophysics of Galaxies

ALMA Polarization Study of the Magnetic Fields in Two Massive Clumps in the 20 km s$^{-1}$ Cloud of the Central Molecular Zone

Yuhua Liu, Xing Lu, Junhao Liu et al. (+14 more)

We present the Atacama Large Millimeter/submillimeter Array (ALMA) observations of linearly polarized 870 $\mu$m continuum emission at a resolution of $\sim$0.2$^{\prime\prime}$ (2000 au) toward the two massive clumps, Clump 1 and Clump 4, in the 20 km s$^{-1}$ cloud. The derived magnetic field strengths for both clumps range from $\sim$0.3 to 3.1 mG using the Angular Dispersion Function (ADF) method. The magnetic field orientations across multiple scales suggests that the magnetic field dominates at the cloud scale, whereas gravity likely governs the structures at the core (0.01$-$0.1 pc) and condensation ($\le$ 0.01 pc) scales. Furthermore, the study on the angular difference between the orientations of the local gravity gradient and the magnetic field suggests that the gravity predominantly governs the dynamics in the diffuse regions, while both gravity and star formation feedback become increasingly significant within the dense regions. The ratio of the magnetic field tension force $F_\mathrm{B}$ to the gravitational force $F_\mathrm{G}$ suggests that the magnetic field may provide some support against gravity, but it is insufficient to prevent gas from infalling toward the dense cores.
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All authors Yuhua Liu, Xing Lu, Junhao Liu, Xing Pan, Qizhou Zhang, Hauyu Baobab Liu, Meng-Zhe Yang, Shih-Ping Lai, Tao-Chung Ching, Wenyu Jiao, Yankun Zhang, Pak Shing Li, Zhiqiang Shen, Tie Liu, Adam Ginsburg, Qi-Lao Gu, Mengke Zhao

Astrophysics of Galaxies

Emission-line Diagnostics at $z\gtrsim 2$: A Probe of the Ionizing Spectrum and $\alpha$ Enhancement Beyond Cosmic Noon

Leonardo Clarke, Natalie Lam, Alice E. Shapley et al. (+5 more)

We analyze several key rest-optical emission-line ratios in a sample of 828 galaxies as well as composite spectra from JADES DR3 in the range $1.4 < z < 7$. These emission-line ratios include: [O III]$\lambda5008$/H$\beta$, [N II]$\lambda 6585$/H$\alpha$, [S II]$\lambda\lambda 6718,6733$/H$\alpha$, [O I]$\lambda 6302$/H$\alpha$, O32, R23, Ne3O2, and RO2Ne3. We find evidence for a harder ionizing spectrum at $z\sim 3.5$ compared to $z\sim 2$ at fixed gas-phase metallicity, resulting in a pronounced shift in the star-forming galaxy locus on the [N II]/H$\alpha$ BPT diagram and the O32 vs. R23 diagram. At $z\gtrsim 3.5$, star-forming galaxies occupy a common locus, indicating that ISM ionizing conditions at fixed gas-phase metallicity do not evolve strongly at these early cosmic times. There is a connection between ISM ionizing conditions and the chemical abundance patterns (i.e., $\alpha$/Fe) in massive stars providing the ionizing radiation field. Therefore, the lack of evolution in ISM ionizing conditions at $z\gtrsim 3.5$, followed by evolution towards a softer ionizing spectrum at fixed nebular metallicity as cosmic time proceeds to $z\sim 2$ and lower redshift mirrors the chemical abundance patterns in Milky Way stars as a function of iron abundance. Our results highlight the diagnostic power of emission-line diagrams in the era of JWST to further our understanding of the ISM conditions into the Epoch of Reionization.
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All authors Leonardo Clarke, Natalie Lam, Alice E. Shapley, Michael W. Topping, Gabriel B. Brammer, Ryan L. Sanders, Naveen A. Reddy, Shreya Karthikeyan

Solar and Stellar Astrophysics

Magnetic Topology and Loop Statistics in Observed Coronal Holes Using Potential Field Modeling

Stephan G. Heinemann, Jens Pomoell and Manuela Temmer

Potential Field Source Surface (PFSS) models are widely used to study the solar corona and form the basis for solar wind forecasting, yet often fail to reproduce observed properties of coronal holes. We analyze 702 observed coronal holes between 2010 and 2019 and compute corresponding PFSS magnetic field extrapolations to examine their magnetic topology and loop statistics, comparing them with quiet Sun regions. Our goal is to determine how observed coronal holes are represented in a PFSS model and to identify sources of known discrepancies. We find that low-lying loops covering the weak, balanced background field in coronal holes are statistically smaller and narrower than in quiet Sun regions, with a median height strongly correlated to the coronal holes mean magnetic flux density (cc_Pearson = 0.81). This suggests that at low altitudes, the coronal hole magnetic topology is primarily governed by its flux density, unlike in quiet Sun regions. Coronal holes also contain loops extending much higher into the corona than typical quiet Sun loops, although it is unclear if these are truly closed or reflect source surface height limitations. Overall, differences in modeled magnetic structures of coronal holes and quiet Sun regions are evident, even when the PFSS model does not indicate any open fields. These results suggest that observed coronal holes correspond to distinct photospheric magnetic structures, and that discrepancies with PFSS models reflect modeling limitations rather than the absence of coronal holes.
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