Solar and Stellar Astrophysics
Revisiting the Galactic age-metallicity relation from wide white dwarf-main-sequence binaries
Alberto Rebassa-Mansergas, Iset Tejero-Gómez and Roberto Raddi
The age-
metallicity relation (AMR) is a fundamental observational constraint for understanding the chemical
evolution of the
Galaxy. As reliable cosmochronometers, white
dwarfs in binary systems with main sequence companions (WD+MS binaries) provide excellent laboratories to study this relation, since both components are expected to be coeval. We construct a sample of widely separated WD+MS binaries using data from the third data release of the
Gaia mission in order to investigate the AMR of the
Galactic disk. The sample is identified using photometric measurements and parallaxes of both components. White
dwarf ages are derived by interpolating their
Gaia absolute G magnitudes and BP-RP colours within state-of-the art white
dwarf evolutionary sequences. We compile publicly available [Fe/H] abundances for the main sequence companions from the literature and combine them using different statistical approaches to obtain representative
metallicity values for each system. We derive the AMR from several sub-samples of WD+MS that use independent measurements of [Fe/H] abundances and consistently find a large dispersion in [Fe/H] at all ages. This behaviour agrees with previous determinations of the AMR based on both WD+MS binaries and samples of isolated
stars. Our results reinforce the observational evidence that the AMR in the
Galactic disk exhibits substantial intrinsic scatter, likely reflecting the combined effects of multiple mechanisms such as radial migration, inhomogeneous chemical enrichment, and variations in the
star formation history.
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Cosmology and Nongalactic Astrophysics
Inferring Halo Mass and Scale Radius of Galaxy Clusters Using Convolutional Neural Networks and Uchuu-UniverseMachine Catalogs
Hirobumi Tominaga, Asuka Nakamura, Tomoaki Ishiyama et al. (+1 more)
We investigate the ability of machine learning to infer the virial mass ($M_{\rm vir}$) and the scale radius ($r_{\rm s}$) of
galaxy clusters from their observables. Using the Uchuu–UniverseMachine
galaxy catalog at $z=0.093$, we generate mock cluster observations that include interlopers, and we encode each cluster as an image representing the two-dimensional joint probability distribution of member
galaxies' projected position and line-of-sight velocity. We train two architectures: a baseline convolutional neural network (CNNb) following a previous approach, and an extended model (CNNr) that appends richness as an additional scalar input. We further compare the performance of networks trained on the all cluster sample and on a dynamically relaxed subsample. Across the test ranges $10^{13.7}\leq M_{\rm vir}\leq10^{15.3}$ Msun/h and $10^{1.7}\leq r_{\rm s}\leq10^{2.7}$ kpc/h, all configurations yield nearly unbiased absolute median residuals (within 0.01 dex). For the
halo mass, adding richness narrows the residual distribution, reducing the standard deviation from 0.133 to 0.122 dex for the all sample, and from 0.124 to 0.111 dex for the relaxed sample. For the scale radius, restricting the training to relaxed clusters improves the performance more than adding richness. The standard deviation decreases from 0.180 to 0.154 dex for CNNb and from 0.175 to 0.148 dex for CNNr, while the inclusion of richness yields only a modest improvement of 0.005 dex. These results demonstrate that machine learning is a powerful tool to infer the mass and internal mass distribution of clusters, providing a new window for cosmological inferences and understanding
galaxy formation processes.
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All authors Hirobumi Tominaga, Asuka Nakamura, Tomoaki Ishiyama, Mohamed H. Abdullah
Astrophysics of Galaxies
The Reaction between Atomic Carbon and Molecular Nitrogen as a Source of Cyanamide and Carbodiimide on Interstellar Ices
Kevin M. Hickson, Jean-Christophe Loison and Audrey Coutens
Reactions occurring on the ice-covered surfaces of interstellar
dust grains are considered to be among the most important sources of complex species in the interstellar medium. Despite this, molecules such as cyanamide, NH2CN, are largely underpredicted by current astrochemical models suggesting that the network of reactions currently used to describe this species and its tautomer carbodiimide, HNCNH, are incomplete. Here, we performed a theoretical investigation of the reaction of ground state atomic carbon C(3P) with molecular nitrogen N2 in both the gas-phase and on the surface of amorphous solid water (ASW) clusters to examine its potential importance in the formation of NH2CN and HNCNH. We show that the reaction of gas-phase C-atoms with N2 molecules already present on the ASW surface results in the barrierless formation of CNN. Following exothermic hydrogenation reactions, the N-N bond of the C-N-N bearing intermediates is broken allowing the formation of molecules with N-C-N backbones through cyclic intermediates over low barriers. To test the importance of these processes to NH2CN and HNCNH formation, these reactions were included in a three-phase astrochemical model of low-mass protostellar
evolution employing a reaction network that was updated to better describe the formation and destruction pathways of related small nitrogen bearing molecules. These simulations demonstrate that the ice surface reaction between C and N2 represents by far the dominant source of NH2CN and HNCNH in protostellar environments and in dense clouds.
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Earth and Planetary Astrophysics
Beyond the mass-radius plane: Integrated radiative-convective and interior structure simulations of the exoplanet continuum
Harrison Nicholls, Oliver Shorttle, Tim Lichtenberg et al. (+1 more)
Static structure models, which map mass-radius constraints to bulk
planet composition, are frequently used to categorise
exoplanets due to their computational efficiency and the high-level insight they offer into planetary properties. However, static structure models typically have simplified atmospheric treatments, which may introduce systematic biases when interpreting the structures - and therefore the climates - of sub-Neptunes and super-Earths. We present a framework for recovering
exoplanet properties using static structure models that accounts for necessary physical-chemical complexity in their atmospheres. We produce a comprehensive library of 504,000
exoplanet simulations that unify deep planetary interior structure with radiative-convective-chemical
climate calculations. From these models we demonstrate that a
planet's envelope mass fraction - a critical parameter to infer - is frequently degenerate with its instellation flux and atmospheric
metallicity, and sensitive to the treatment of gravitational acceleration at the mbar level. Such uncertainties have significant implications for inferring planetary processes, as our modelling shows that habitable-zone sub-Neptunes readily host supercritical surfaces or deep magma oceans, despite their temperate irradiation regime. To marginalise over these uncertainties, we introduce a
Bayesian retrieval tool that uses our library of self-consistent models. By applying this
Bayesian approach to case-studies of pi Men c and TOI-421 b, we show that robust physical interpretations are achievable through whole-
planet mass-radius
retrievals. While new data from JWST, Ariel, and PLATO will expand our observational horizon, physically-consistent modelling provides the means to transition from categorical interpretations toward a comprehensive picture of the
exoplanet continuum.
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All authors Harrison Nicholls, Oliver Shorttle, Tim Lichtenberg, Flavia Pascal
High Energy Astrophysical Phenomena · Cross-listed from gr-qc
Gravitational-wave astronomy requires population-informed parameter estimation
Matthew Mould, Rodrigo Tenorio and Davide Gerosa
Gravitational-wave events are interpreted in terms of
Bayesian posteriors for their source properties inferred under unphysical reference priors. Though these parameter estimates are important intermediate data products for downstream analyses, we demonstrate that they are generically biased and therefore should not be used for astrophysical interpretation directly, as is common. Hierarchical parameter estimation is the solution, as joint analysis of the entire catalog of observations reduces statistical uncertainties and actually informs the correct prior, with population-informed event parameters now appropriate for astrophysical interpretation. As an example, we show how the most extreme measurements from a catalog can be derived and used to identify exceptional events from previous and ongoing observing runs, pointing out they are more informative about the population than any individual event. Using LIGO-Virgo-KAGRA data, we thus demonstrate that population inference is not optional to interpret gravitational-wave observations.
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Solar and Stellar Astrophysics
PISP: Projected-Space Inference of Stellar Parameters
Jun-Chao Liang, Yin-Bi Li, A-Li Luo et al. (+12 more)
To improve the accuracy and efficiency of high-dimensional
stellar parameter inference in large spectroscopic
datasets, we propose a projection-assisted parameter-inference framework – Projected-Space Inference of
Stellar Parameters (PISP). PISP constructs an orthonormal basis and optimizes in the projected space, reducing the impact of parameter correlations on inference. The basis is constructed using either principal component analysis (PCA) or the active-subspace (AS) method and is combined with two inference strategies – Non-L1, which optimizes the projection coefficients for a user-specified projected dimensionality, and L1, which introduces L1 regularization in the full projected space to adaptively select projection directions – yielding four strategies: PCA-Non-L1, AS-Non-L1, PCA-L1, and AS-L1. For different computational scenarios, we implement two versions: PISP-CurveFit for fast single-spectrum inference and PISP-Adam for large-scale GPU-parallel inference. Using a fully connected neural network and a residual network as spectral emulators, we evaluate PISP on Kurucz synthetic spectra and on $722{,}896$ APOGEE DR$17$ observed spectra. Compared to the baseline strategy, PISP improves inference accuracy for multiple parameters across all emulator-optimizer combinations. In synthetic data, PCA-L1 performs best, reducing the standard deviation of differences ($\sigma(\Delta)$) by at least $0.01$ dex for $12$ of $20$ elemental abundances, with [N/H], [O/H], [Na/H], [Co/H], [P/H], [V/H], [Cu/H] showing $0.05$–$0.72$ dex reductions. In observed data, PCA-Non-L1 reduces $\sigma(\Delta)$ by $>30$ K for effective temperature and by at least $0.01$ dex for $9$ of $17$ elemental abundances, with [O/H], [Na/H], [V/H] showing $0.05$–$0.20$ dex reductions, while achieving a $\sim$$4\times$ efficiency gain, slightly outperforming PCA-L1.
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All authors Jun-Chao Liang, Yin-Bi Li, A-Li Luo, Shuo Li, Xiao-Xiao Ma, Hai-Ling Lu, Shu-Guo Ma, Ming-Hui Jia, Shuo Ye, Hao Zeng, Ke-Fei Wu, Zhi-Hua Zhong, Xiao Kong, Li-Li Wang, Hugh R. A. Jones
Earth and Planetary Astrophysics
Benchmarking Two Chemical Networks used in General Circulation Models of Hot Jupiters
D. A. Christie, M. Zamyatina, E. Hébrard et al. (+7 more)
Chemical kinetics is becoming an increasingly vital component of hot Jupiter general circulation models (GCMs). Here we simulate the hot Jupiter WASP-96b using two chemical networks, a reduced chemical network frequently used in the GCM literature (which we refer to as V19) and a more recent effective network making use of tables of net reactions (MiniCHEM), coupled to the same GCM in order to provide a robust
benchmark. We find a numerical escape criterion used by the Unified Model chemical kinetics solver to stop integration for the duration of the chemical timestep, independent of the chemical network, results in artificial quenching, overestimating of HCN, CH$_4$, and NH$_3$ abundances by factors of 1.5 to 3. With this criterion disabled, agreement between the two networks is improved, except for HCN and NH$_3$, where different reaction rates and included species results in lower abundances in the V19 network. While many rates differ between the networks, the lower quenched NH$_3$ abundances in the V19 simulations are, in particular, due to the choice of NH$_2$ + NH$_3$ $\rightarrow$ N$_2$H$_3$ + H$_2$ reaction rate, which is poorly constrained in the literature. This reaction also impacts the quenching of HCN, which is additionally affected by the lack of CH$_2$NH$_2$ in the V19 network. While there are reasons to favour the MiniCHEM HCN and NH$_3$ abundances, ultimately, improved experimental and theoretical determination of reaction rates are needed to address the uncertainties and better characterize the quenching behaviour.
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All authors D. A. Christie, M. Zamyatina, E. Hébrard, T. M. Evans-Soma, N. J. Mayne, E. K. H. Lee, S.-M. Tsai, D. E. Sergeev, R. Veillet, K. Kohary
Earth and Planetary Astrophysics
A gem system with a lava world and a habitable zone sub-Neptune orbiting TOI-1752
A. Peláez-Torres, F. J. Pozuelos, G. Morello et al. (+47 more)
The Transiting
Exoplanet Survey Satellite (TESS) has delivered a large number of transiting
planet candidates around nearby
stars by identifying periodic decreases in
stellar brightness. Establishing the planetary nature of these signals and determining their fundamental properties is a necessary step toward detailed studies of their internal structure, atmospheres, and formation pathways. In this work, we investigate the planetary nature of the TOI-1752 system (M1 V, $103.02\pm0.34$ pc), which hosts two TESS candidates: TOI-1752 b, a short-period object consistent with a lava-world scenario, and TOI-1752 c, a sub-Neptune-size
planet candidate located in the optimistic habitable zone. We obtained ground-based multi-color photometric follow-up observations of TOI-1752, which we combined with TESS photometry to assess the nature of both signals. We performed a formal statistical validation using the TRICERATOPS framework, while independently vetting the candidates with the neural-network-based classifier WATSON-Net, which provides a machine-learning assessment of their planetary likelihood based on light-curve morphology, centroid diagnostics, and auxiliary vetting features. We validate TOI-1752 b as a bona fide
planet with a radius of $1.69\pm0.07 R_{\oplus}$ and an orbital period of $0.935186^{+0.000001}_{-0.000002}$ days, and TOI-1752 c with a radius of $2.29^{+0.13}_{-0.14} R_{\oplus}$ and an orbital period of $32.7144\pm0.0004$ days. The combined analysis confirms TOI-1752 as a new planetary system, places TOI-1752 c within the optimistic habitable zone of its host
star, and identifies TOI-1752 b as a promising target for atmospheric characterization, with an estimated emission spectroscopy metric (ESM) of up to $\sim8$.
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All authors A. Peláez-Torres, F. J. Pozuelos, G. Morello, M. Dévora-Pajares, K. Barkaoui, L. Gkouvelis, E. Pallé, K. A. Collins, B. V. Rackham, S. Geraldía-González, M. Centenera-Merino, R. Varas, E. Esparza-Borges, Z. Parlapani, J. Flores, J. Aceituno, P. J. Amado, A. Burdanov, Y. Calatayud-Borras, D. R. Ciardi, B.-O. Demory, T. Gan, S. Giacalone, M. Gillon, Y. Gómez Maqueo Chew, K. Kawauchi, A. Khandelwal, J. Korth, M. Lendl, J. P. de Leon, J. Livingston, N. Morales, F. Murgas, N. Narita, J. L. Ortiz, H. Parviainen, M. Pichardo Marcano, I. Plauchu-Frayn, D. Queloz, D. Rapetti, J. Saito, A. Sánchez-López, A. B. Savel, R. P. Schwarz, U. Schroffenegger, M. Serra-Ricart, C. Stockdale, A. H. M. J. Triaud, J. de Wit, F. Zong Lang
Earth and Planetary Astrophysics
Asteroid modelling by starlight diffraction: The shape of Dimorphos, the satellite of (65803) Didymos
P. Tanga, K. Tsiganis, D. Souami et al. (+17 more)
The DART spacecraft impacted Dimorphos, the satellite of (65803) Didymos, in September 2022. Evidence of crater formation and possible global reshaping has been obtained indirectly from spacecraft and ground-based data. Since the impact, several
stellar occultations by Didymos have been observed, but only one in particular, on January 21, 2023, can provide useful constraints on the size and shape of Dimorphos. We modelled the diffraction signatures recorded on multiple occultation chords to constrain the projected shape and size of Dimorphos, assuming an ellipsoidal model. This is the first time diffraction observed simultaneously on several chords of a single event has been used for such a purpose. The projected shape at the epoch of the event is well constrained and consistent with recent post-DART determinations. When extended to a full three-dimensional ellipsoidal solution, the result remains compatible with previous studies, suggesting an equatorially elongated post-impact shape.
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All authors P. Tanga, K. Tsiganis, D. Souami, R. Anderson, E. Barbotin, A. Cazaux, F. Colas, J. Hanuš, F. Marchis, J-L. Dauvergne, G. Langin, A. Leroy, B. Lott, A. Manna, L. Rousselot, A. Siakas, S. Sposetti, Ch. Vigna, F. Weber, A. Wünche
High Energy Astrophysical Phenomena
Induced Scattering of Strong Waves in Pair Plasmas
Masanori Iwamoto and Kunihito Ioka
We study induced (stimulated) scattering of linearly polarized, strong electromagnetic waves in pair
plasmas, which is crucial for understanding the propagation of fast
radio bursts (FRBs). Magnetars are the most promising progenitors of FRBs, and FRBs propagate through the magnetar wind and successfully escape before being significantly scattered. We revisit the steady-state solution of linearly polarized electromagnetic waves in pair
plasmas with arbitrary amplitude, and demonstrate that the nonlinearity is characterized by the nonlinearity parameter $a_0\omega_{pe}/\omega_0$ rather than the dimensionless amplitude $a_0$, where $\omega_{pe}$ is the electron
plasma frequency and $\omega_0$ is the wave frequency. We follow the time
evolution of the steady-state solution for the linear regime $a_0\omega_{pe}/\omega_0 \ll 1$ by performing one-dimensional particle-in-
cell simulations, and show that the conventional linear analysis of induced scattering assuming $a_0 \ll 1$ is applicable even for $a_0 > 1$ when the Lorentz boost due to the
plasma motion in the incident wave is considered. The saturation level is controlled by $a_0\omega_0/\omega_{pe}$, which corresponds to the ratio of the wave energy to the
plasma energy, and the incident wave is hardly scattered for $a_0\omega_0/\omega_{pe} \gg 1$. We discuss the application of our results to FRBs.
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Cosmology and Nongalactic Astrophysics
Inverting Fisher biases for fast systematics exploration
Biancamaria Sersante, Christos Georgiou and Nora Elisa Chisari
Upcoming cosmological surveys will achieve increasingly precise constraints in cosmological parameter estimation. To guarantee the robustness of cosmological analyses, it is essential to account for and model systematic effects that can bias cosmological constraints, shifting the best fit parameters away from their fiducial values. It is possible to approximately infer the biases that un-modelled systematic effects might introduce in cosmological parameter estimation by means of the Fisher
matrix formalism. In this paper, we introduce a new application of this formalism, where by inverting the process, we investigate whether a specific missing or mis-modelled systematic effect can explain away a given tension between two different probes or experiments. We showcase the proposed methodology by examining two representative systematics:
galaxy intrinsic
alignments and baryonic feedback. As the method is agnostic to the systematic effect and can be applied to a wider range of scenarios, we discuss more possible future applications. While the proposed approach is accurate in the limit of small offsets in the cosmological parameters, where the likelihood can be considered linear in both the cosmological parameters and the systematics, in practice, the region of validity depends on the systematic effect. In general, even beyond this region, the approach still provides a useful test that helps indicate the magnitude and direction of potential biases from systematic effects in data.
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Instrumentation and Methods for Astrophysics · Cross-listed from gr-qc
Mechanical Long Baseline Differential Gradiometers as Low Frequency Gravitational Wave Detectors
Enrico Calloni, Annalisa Allocca, Antonino Chiummo et al. (+12 more)
We present a new differential mechanical gradiometer for the detection of low-frequency Gravitational Waves. The frequency range is 0.05 to 1 Hz, a frequency gap not covered either by future space-based detectors such as LISA or by ground-based observatories such as Einstein
Telescope or
Cosmic Explorer. The proposed detection principle is similar to
antennas based on torsion pendulums but solves the problem of physical confinement of these
antennas by operating vertically and by having a counterweight at one end of each bar and a mass suspended from a long wire at the other. With this configuration, we enlarge the gravitational force acting on the system without changing the moment of inertia of the system, so that we move from a signal $\Delta \theta$ of the order of $\Delta \theta = h$, where h is the amplitude of the gravitational wave, to a signal of the order $\Delta \theta = h\frac{L}{D}$, where D is the length of the arm and L is the length of the wire suspending the test mass. This configuration is a further
evolution of the recent development of tiltmeters and balances with double suspended arms and interferometric read-out, where the main working principles are already tested. The expected sensitivity will be discussed with respect to the proposed parameters and the present technology.
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All authors Enrico Calloni, Annalisa Allocca, Antonino Chiummo, Rosario De Rosa, Luciano Errico, Marina Esposito, Edoardo Imparato, Bruno Mantice, Luigi Rosa, Paolo Ruggi, Alessandra Ruggiero, Valeria Sequino, Daniela Stornaiuolo, Vittorio Tortorella, Lucia Trozzo
High Energy Astrophysical Phenomena · Cross-listed from gr-qc
Geometrically Regular Black Holes with Hedgehog Scalar Hair
Sebastian Bahamonde
We study a simple theory based on general relativity, minimally coupled to a constrained scalar triplet and to an auxiliary non-propagating three-form sector. Within a spherically symmetric hedgehog ansatz, the theory admits a continuous exact family of asymptotically flat geometrically regular black holes. For a simple choice of kinetic function, the solutions possess a de Sitter core and approach Schwarzschild with the first correction appearing only at order $r^{-4}$. We analyse their horizon structure, thermodynamics, and main strong-field properties. The black holes carry topological scalar hair and a continuous secondary parameter, but no scalar charge. The regularity established here is
geometric: the
curvature invariants remain finite, although the matter sector is not completely smooth at the centre.
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High Energy Astrophysical Phenomena
A universal relationship between the variability timescale and black hole mass in black hole jetted and non-jetted accreting systems
Yongyun Chen, Qiusheng Gu, Junhui Fan et al. (+4 more)
A long-term variability study spanning a range of black hole mass systems, from microquasars hosting
stellar-mass black holes to active
galactic nuclei (AGNs) harboring supermassive black holes, provides new insights into the physics of relativistic jets. In this work, we investigate the optical variability of both jetted and nonjetted AGNs. We apply a
stochastic process known as the Damped Random Walk (DRW) to model light curves from the Zwicky Transient Facility (ZTF) DR23. Our results show that the mass-scaled characteristic timescales across the black hole mass exhibit a linear relationship with a slope of 0.35-0.50. This analysis confirms a previously observed correlation between the damping timescales and black hole mass and extends it by incorporating 125 newly identified non-jetted AGNs selected from the Burst Alert
Telescope (BAT) AGN catalogue. The derived slope of the relation between the damping timescales and black hole mass aligns with recent theoretical predictions, supporting the presence of a universal
accretion mechanism in AGNs across different mass scales. Furthermore, our findings suggest a novel implication: the properties and production mechanisms of relativistic jets may be largely independent of black hole mass.
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All authors Yongyun Chen, Qiusheng Gu, Junhui Fan, Dingrong Xiong, Xiaoling Yu, Xiaogu Zhong, Xiaotong Guo
Astrophysics of Galaxies
A New Cloud-Cloud Collision Source N68 toward the G35 Molecular Cloud Complex
En Chen and Xi Chen
Bubble N68 in the G35 complex shows clear cloud-cloud collision (CCC) signatures. Its semi-ring-like morphology harbors many significant massive
star formation tracers: 6 HII regions, 4 6.7 GHz masers, 5 Midcourse Space Experiment sources, 9
radio peaks, and nearly 10 O/B-type
stars. We also identified 163 young
stellar objects (45 Class I, 5 Flat, 113 Class II), indicating active
star formation toward N68. Our molecular study with CO reveals two distinct molecular clouds (N68a: 47-56 km s$^{-1}$; N68b: 56-64 km s$^{-1}$), with broad bridge features and complementary distributions at their borders, indicating an ongoing CCC.
Star formation in N68 is collectively driven by collect-and-collapse (CC), radiation-driven implosion (RDI), and CCC mechanisms. However, compared with the CC and RDI mechanisms, the CCC mechanism does not enhance the
star formation efficiency; instead, it tends to trigger the formation of massive
stars. N68, along with bubbles N65 and N61, constructs a $\sim100$ pc scale CCC system in the G35 complex.
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Solar and Stellar Astrophysics
Radiation-driven stellar winds at the fast-slow transition: new hydrodynamic solutions
M.C. Fernandez, R.O.J. Venero, L.S. Cidale et al. (+2 more)
Radiation-driven winds of massive
stars can be described within the modified CAK theory, which parametrises the radiation force through three key quantities: $\alpha$, $\delta$, and $k$. Different combinations of these parameters, together with rotation, result in three types of stationary solutions, namely fast (or classical), $\delta$-slow, and $\Omega$-slow solutions. The primary objective of this work is to model radiation-driven winds inside the gap region between the fast and $\delta$-slow regimes, where stationary solutions have proven elusive. In addition, we compute synthetic line profiles of H I, He I, and Si IV to illustrate the morphology of different wind regimes. We employ the time-dependent hydrodynamic code ZEUS-3D, capable of obtaining stationary solutions by progressing through an initial solution. Then we compute the line profiles solving the transfer equation for an expanding atmosphere, assuming spherical
symmetry in the comoving frame, under non-local thermodynamic
equilibrium (NLTE) conditions. We found new stationary solutions in the gap region, alongside their corresponding line profiles, for a typical B supergiant
star model. In this model, the new solutions are stable, and some of them present a kink in the velocity profile at a fixed distance from the
star, depending on the $\delta$ value. Perturbations in the wind ionisation may trigger transitions between different hydrodynamic regimes and offer a plausible explanation for structured and variable winds. A systematic investigation of these effects will be the subject of future work. Furthermore, we investigate the resulting line profiles from different hydrodynamic solutions and compare them with those predicted by a velocity profile given by a $\beta$-law using the same global wind parameters.
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All authors M.C. Fernandez, R.O.J. Venero, L.S. Cidale, I. Araya, M. Curé
High Energy Astrophysical Phenomena
Circular polarization images of Sgr A* for different magnetic field geometries
Hao Yin, Songbai Chen and Jiliang Jing
Sgr A* exhibits a persistent negative circular polarization (CP) at 230\,GHz, offering a powerful probe of the
magnetic field geometry in its
accretion flow. Using a stationary semi-analytic radiatively inefficient
accretion flow (RIAF) model in Kerr spacetime with polarized radiative transfer, we systematically analyze CP images for six poloidal
magnetic field configurations across varying black hole
spins, inclinations, and field polarities. We find that CP production is dominated by Faraday conversion in radial,
parabolic, quadrupole, and combined geometries, but by intrinsic emission in dipole and vertical fields. The radial and
parabolic configurations produce the polarity-invariant net CP, while dipole and vertical fields yield the polarity-sensitive one. As the
accretion disk is prograde with respect to the black hole
spin, the CP production across all six field geometries is found to be lower at high
spin case, while the situation is more complicated in the retrograde case. Moreover, the net CP observed from edge-on views $V_{\rm net} \approx 0$ except for the quadrupole geometry. Comparing with ALMA data, the reversed-field model is excluded at high inclinations and then the
magnetic field geometry of Sgr A* is constrained.
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Astrophysics of Galaxies
Distances to molecular clouds in the Galactic longitude l=10-20 deg from the MWISP 12CO 1-0 survey
Juan Mei, Zhiwei Chen, Min Fang et al. (+3 more)
We present distances to 56 molecular clouds within $10\degr \leq l \leq 20\degr$ and $|b| \leq 5.25\degr$ from the Milky Way Imaging Scroll Painting (MWISP) $^{12}$CO survey, 47 of which are first-time determinations. The molecular clouds were identified using the DBSCAN
algorithm, and their distances were measured with the model-calibrated color-distance method using $J-K{_s}$ colors and the distances provided by 2MASS and
Gaia EDR3. The distances range from $\sim$275 pc to $\sim$2118 pc. We also derived the physical properties of molecular clouds and found a moderate correlation between the
dust extinction and the $^{12}$CO integrated intensity.
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All authors Juan Mei, Zhiwei Chen, Min Fang, Miaomiao Zhang, Shiyu Zhang, Zhibo Jiang
Astrophysics of Galaxies
The Impact of the Bar on Dense Gas and Star Formation in M83
Tianyi GU and Yoshimasa Watanabe
Although the relationship between molecular gas content and the
star formation rate (SFR) has been extensively studied in nearby
galaxies, it remains controversial whether the
star formation efficiency (SFE) depends on
galactic structure. In particular, whether the SFE is suppressed in the bar region compared with other structures, and the physical origin of this suppression, remain poorly understood. In this study, we investigate variations in the SFE and its physical drivers in the bar region of the nearby spiral
galaxy M83, using multi-wavelength observations toward the bar and spiral arm regions on a scale of 200 pc observed with ALMA. From the molecular gas surface density derived from $^{12}$CO($J=2-1$) and $^{13}$CO($J=1-0$), the dense molecular gas surface density derived from HCN ($J = 1-0$), and the
star formation rate surface density determined from extinction-corrected H$\alpha$, we find that the SFEs in the bar region are roughly a factor of two lower than those in the spiral arm, indicating that the SFE is systematically suppressed in the bar. Moreover, we find that the SFEs of dense gas are lower in the bar than in the arm by a factor of about 0.35. These results suggest that not only the efficiency of converting bulk molecular gas into
stars reduced in the bar, but the efficiency of
star formation from dense gas is also lower. In addition, the CO line widths are systematically larger in the bar region and exhibit a negative correlation with both the SFE and the dense-gas SFE, consistent with the interpretation that enhanced turbulent motions hinder
star formation. Although the analysis is limited to small regions of M83, our results suggest that the suppression of the SFE is related to large-scale dynamical effects on the molecular gas, such as strong shocks induced by cloud-cloud collisions and/or shear, both driven by non-circular motions in the bar.
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