High Energy Astrophysical Phenomena · Cross-listed from gr-qc
Structure and astrophysical properties of dark energy admixed neutron stars
Juan M. Z. Pretel, Sergio B. Duarte, Mariana Dutra et al. (+1 more)
The presence of a dark energy (DE) core, made of a Chaplygin dark fluid, is capable of influencing the diverse observable properties of
neutron stars (NSs). However, there is also the possibility that NSs could contain a mixture of ordinary nuclear matter and DE. In this perspective, we propose an equation of state (EoS) that includes both normal matter and DE, where a free parameter $f$ quantifies the ratio of DE density with respect to the total energy density. As expected, in the limit $f \rightarrow 0$ we recover the already known results corresponding to pure nuclear matter. Remarkably, increasing this fraction $f$ leads to a softer EoS and thus strongly favors the fulfillment of the causality condition. As a consequence of our mass–radius results, the central compact object in HESS J1731-347 can be satisfactorily described as a DE admixed NS. For sufficiently high stellar masses, our calculations further indicate that both the gravitational
redshift and the fundamental nonradial oscillation frequency increase significantly with an increasing DE fraction, whereas the opposite trend is observed for the total gravitational mass and tidal deformability. As is typical for compact
stars composed purely of ordinary matter, we find that in our DE admixed stellar models the central density corresponding to the maximum-mass configuration coincides with the point at which the squared radial vibration frequency vanishes. Moreover, higher DE concentrations lead to enhanced stability of these configurations.
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All authors Juan M. Z. Pretel, Sergio B. Duarte, Mariana Dutra, Odilon Lourenço
Earth and Planetary Astrophysics
Time-resolved JWST Retrieval Analysis of the Coldest Brown Dwarf: Temperature and Chemical Variations in WISE 0855-07
Harshil Kothari, Caroline V. Morley, Brittany E. Miles et al. (+12 more)
WISE J0855-07 is the coldest known brown dwarf (estimated Teff~250 K), offering a rare opportunity to probe atmospheric physics in the temperature and mass regime that overlaps directly with
exoplanets. At these temperatures, modest perturbations to the thermal structure and chemical abundances can produce measurable changes in the emergent mid-infrared spectrum, making time-resolved spectroscopy a powerful way to test whether the atmosphere is longitudinally and temporally homogeneous. Using James Webb Space
Telescope NIRSpec/G395M time-series spectra spanning ~3 to 5.2 {\mu}m over 11 hr, we analyze every third spectrum from the
dataset with a series of time-resolved atmospheric
retrievals using the Brewster
retrieval framework. Using this approach, we model epoch-to-epoch changes in the atmospheric state that drive the observed variability, including the thermal structure and key molecular abundances. From the time-series
retrievals, we find that the primary source of the observed spectral variability is driven by the variations in the thermal structure, which range from ~1 to <100 K from epoch to epoch, particularly between the pressures of ~0.4 and 10 bar. In addition, changes in the abundances of CO, and possibly PH3 and CO2, further modulate the spectrum within specific molecular features. These measurements provide a
retrieval-based view of atmospheric variability in an ultracold,
planet-like object, directly constraining how thermal and chemical structure evolve on observable timescales.
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All authors Harshil Kothari, Caroline V. Morley, Brittany E. Miles, Melanie J. Rowland, Natasha Batalha, Michael C. Cushing, Andrew J. Skemer, James Mang, Brianna Lacy, Johanna M. Vos, Channon Visscher, Adam C. Schneider, Genaro Suarez, Mikayla J. Wilson, Allison M. McCarthy
Cosmology and Nongalactic Astrophysics
A two-component profile of baryonic feedback: hydrostatic and diffuse gas
Kaitlyn Shavelle, Jared Siegel, Leah Bigwood et al. (+2 more)
Baryonic feedback processes redistribute gas within and beyond dark matter
halos, however, the resulting gas distribution remains highly uncertain, limiting predictions of the matter distribution for precision cosmology. We introduce a physically motivated approach to modelling the gas distribution that decomposes it into an approximately hydrostatic inner component and a diffuse outer component. This approach takes advantage of the growing observational landscape: X-ray measurements primarily probe the dense inner
halo, while the kinetic Sunyaev-Zel'dovich (kSZ) effect is sensitive to diffuse ionized gas extending to larger radii. We implement this two-component profile within the baryonification framework, though we note that it is applicable to any model of the large-scale gas distribution. We jointly fit X-ray gas-fraction measurements from the HSC-XXL and eROSITA samples with stacked kSZ effect measurements of BOSS CMASS
galaxies from the Atacama Cosmology
Telescope, demonstrating that the proposed profile retains sufficient flexibility. This proof-of-concept shows that a decomposition between hydrostatic and diffuse gas provides a simple, physically interpretable framework for connecting complementary observations of the gas distribution, and a foundation for future models of baryonic feedback.
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All authors Kaitlyn Shavelle, Jared Siegel, Leah Bigwood, Alexandra Amon, Romain Teyssier
Solar and Stellar Astrophysics
GIARPS simultaneous optical and infrared high-spectral-resolution observations of Cepheids I. Limb darkening from cross-correlated radial velocities
N. Nardetto, R. S. Rathour, M. C. Bailleul et al. (+17 more)
The Baade-Wesselink method, while theoretically applicable for calibrating the distance scale via Cepheids, is not currently employed in the
cosmic distance ladder. There are various versions of this method. In all these approaches, the projection factor used to convert the radial into the pulsation velocity remains the limiting quantity. By comparing for the first time simultaneous cross-correlated optical and H-band radial velocities of five Cepheids, we aim to better understand the
geometric part of the projection factor that is directly linked to the limb darkening of the
stars. The five Cepheids were observed with the HARPS-N and GIANO-B instruments mounted at the Telescopio Nazionale Galileo in the GIARPS configuration. A two-parameter linear fit was applied to the simultaneous radial velocity measurements of each
star in order to extract the amplitude ratio of both curves (fVH) as well as the difference in mean velocities. We find a mean value of fVH of 1.056 with a root mean square over the five
stars of 0.016, which means that the V-band radial velocity amplitudes are around 5% larger than the ones obtained in the H band. In addition, we find that the H-band radial velocity curves have an average (i.e., a gamma-velocity) of about 1 km/s blueshifted compared to the visible ones, except for one
star, X Cyg, which has a blueshift of 0.4 km/s. At first order, the fVH values are directly linked to the ratio of limb darkening coefficients in both bands (or equivalently the ratio of geometrical projection factors). The fVH values are found to be consistent with expectations from static stellar atmosphere models. This work shows that the differential limb darkening of Cepheids in visible and H bands, and consequently the geometrical part of the projection factor, follows what is expected from stellar atmosphere models.
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All authors N. Nardetto, R. S. Rathour, M. C. Bailleul, V. Hocdé, P. Kervella, G. Bras, W. Gieren, J. Storm, G. Pietrzynski, B. Zgirski, P. Wielgorski, A. Merand, A. Gallenne, E. Poretti, M. Rainer, L. Breuval, M. Duparc, B. Apostolova, W. Kiviaho, K. Sivkova
Astrophysics of Galaxies
Supernova origin of galactic turbulence revealed by superbubbles
Fanyi Meng, Chao-Wei Tsai, Jingwen Wu et al. (+13 more)
Supernovae (SNe) are among the leading candidates for powering galactic-scale
turbulence. SNe drive expanding shells of neutral atomic hydrogen (HI) known as superbubbles. Due to the lack of a sensitive, dynamically complete,
galaxy-wide census, superbubbles have not been used to quantify the galactic-scale turbulent energy budget. Here we present a combined Five-hundred-meter Aperture Spherical
radio Telescope (FAST) and Jansky Very Large Array HI survey of the Andromeda
galaxy (M31), the nearest giant spiral, with superior sensitivity and dynamical coverage. We identify 118 superbubbles across the entire disk of M31 with dynamical ages up to 40 Myr, consistent with the expected duration of SN activity in a
star cluster and extending the age coverage well beyond previous surveys. Inferred from these superbubbles, the kinetic energy injection rates ($10^{49}$–$10^{51.5}$ erg kpc$^{-3}$ Myr$^{-1}$) from SNe closely match the
turbulence dissipation rates derived independently from the same data, in both magnitude and spatial distribution. These results demonstrate that clustered SN feedback is sufficient to sustain galactic-scale
turbulence, which shapes disk structure and influences
galaxy evolution.
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All authors Fanyi Meng, Chao-Wei Tsai, Jingwen Wu, Sihan Jiao, Mordecai-Mark Mac Low, Zhi-Yu Zhang, Amélie Saintonge, Hui Li, Zongnan Li, Jie Wang, Lile Wang, Haitao Xu, Yanbin Yang, Kai Zhang, Rouyu Li, Di Li
Solar and Stellar Astrophysics
Orbital and stellar parameter determination of eclipsing $\beta$ Cep pulsators
C. I. Eze, G. Handler, F. Kahraman Aliçavuş et al. (+2 more)
Eclipsing binaries provide precise constraints on stellar properties and
evolution, making those hosting $\beta$ Cep pulsators particularly valuable for characterising massive pulsating
stars. In this paper, thirteen eclipsing binaries with massive primary components are spectroscopically and photometrically analysed to derive the orbital and stellar parameters, and infer their possible evolutionary status. The systems were spectroscopically observed using SALT HRS, HERMES, CHIRON and a spectrograph at Skalnate Pleso Observatory (SPO), and photometrically observed using TESS. Radial velocities and atmospheric parameters are determined, binary systems are modelled, and their absolute parameters are derived using appropriate modelling tools. The rotational properties, circularisation, and synchronisation of the systems are also investigated, and the general properties of the sample are discussed. The sample shows one slow rotator, two circularised and synchronised fast rotating systems, as well as five circular and five eccentric systems with asynchronous fast rotation. The systems are predominantly SB1 or SB2 with faint companions, resulting in dynamical mass estimates at $5$ – $12\%$ precision and radius estimates at $1.5$ – $3.9\%$ precision. The secondary components appear to cut across a wide mass spectrum ranging from low-mass to intermediate mass systems. The eccentricity of the systems shows certain trends with the projected rotational velocity ($v \sin i$) although there is no universal correlation between them. Also, there could be circularisation without co-rotation or synchronisation even for circularised short-period close binary systems.
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All authors C. I. Eze, G. Handler, F. Kahraman Aliçavuş, T. Pawar, P. De Cat
Cosmology and Nongalactic Astrophysics
Intrinsic Tidal Shear at the Largest Scales: Galaxy Multiplet Alignment in DESI DR2
C. Lamman, J. Aguilar, S. Ahlen et al. (+45 more)
We measure the intrinsic
alignment (IA) of
galaxy multiplets with the large-scale tidal field traced by
galaxy positions in DESI Data Release 2. Using the BGS, LRG, and ELG samples spanning $0.01 < z < 1.6$, we optimize the scales which define multiplets in each sample to minimize measurement noise. We measure multiplet tidal
alignment $\mathcal{E}_+$ on scales beyond 100 $h^{-1}$Mpc in all samples, and detect
alignment over 200 $h^{-1}$Mpc, up to 4.5$\sigma$ in the highest LRG
redshift bin. We additionally present the multiplet shape-shape autocorrelation, $\mathcal{E}_{++}$, which is independent of
galaxy bias and provides a consistency check of our NLA (nonlinear
alignment) model. We do not detect a baryon acoustic feature in the projected
estimator. We also find the
alignment strength of multiplets is correlated with
redshift and
galaxy morphology. Multiplet
alignment offers direct access to the tidal shear field in all
galaxy samples, even where individual
galaxy alignment cannot, and extends IA detection to the largest scales yet probed.
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All authors C. Lamman, J. Aguilar, S. Ahlen, A. Aviles, D. Bianchi, D. Brooks, A. Carnero Rosell, F. J. Castander, T. Claybaugh, A. de la Macorra, D. Eisenstein, A. Font-Ribera, J. E. Forero-Romero, C. Garcia-Quintero, E. Gaztañaga, G. Gutierrez, K. Honscheid, M. Ishak, S. Juneau, T. Karim, D. Kirkby, O. Lahav, M. Landriau, M. E. Levi, M. Manera, A. Meisner, R. Miquel, S. Nadathur, H. E. Noriega, N. Palanque-Delabrouille, W. J. Percival, M. Perdomo, F. Prada, I. Pérez-Ràfols, C. Ravoux, A. J. Ross, G. Rossi, R. Ruggeri, L. Samushia, E. Sanchez, C. Saulder, D. Schlegel, M. Schubnell, J. Silber, M. Siudek, G. Tarlé, R. Vaisakh, B. A. Weaver
Instrumentation and Methods for Astrophysics · Cross-listed from physics.ins-det
A Deep Neural Network based Level-1 Trigger for the Magnetic Monopole Search in the SCEP Experiment
Changqing Ye, Yunhan Wang, Yifan Qiao et al. (+4 more)
The Search for
Cosmic Exotic Particles (SCEP) experiment proposes a multilayer
magnetic monopole (MM) detection array with a target exposure of O(10^4) m^2 year. Continuously recording the raw waveforms at this scale would generate approximately O(10) EB of data per year, making full waveform storage impractical. A Level-1 trigger is therefore required to reduce the stored-data volume while retaining rare MM signals. MM waveforms vary with particle velocity and trajectory, so a single filter kernel cannot match all possible signals. A mismatch between the kernel and the signal waveform can reduce the detection probability. This work therefore develops a compact template-bank construction method for MM detection. Each incoming waveform is filtered with all kernels in the bank, and the best-matched kernel is identified from their responses. A multilayer perceptron (MLP) trigger is further developed to combine all template responses and improve signal detection. With a 31-sample window and a stored-data fraction of 10^(-3), the MLP increases the mean net acceptance P_net from 6.72% for the conventional template-bank trigger to 8.79%, a relative improvement of 30.8%. The network is then implemented on a Xilinx AC701 board equipped with a field-programmable gate array (FPGA) to process a 20-bit input waveform sampled at 1 MHz using 200 MHz trigger logic. At the target stored-data fraction, the fixed-point implementation reduces P_net by only 3/(3.2 x 10^6) relative to the floating-point reference. On-board tests reproduce the bit-accurate reference trigger outputs and sustain continuous 1 MHz processing without dropped input samples, verifying the functional correctness and real-time operation of the FPGA-based Level-1 trigger.
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All authors Changqing Ye, Yunhan Wang, Yifan Qiao, Zhe Cao, Beige Liu, Qing Lin, Lei Zhao
Solar and Stellar Astrophysics
SN 2026dix: a nearby, transitional Type IIb/Ib supernova consistent with a warm supergiant progenitor
Tamás Szalai, Schuyler D. Van Dyk, Dominik Bánhidi et al. (+20 more)
Understanding the final
evolution stages of (very) massive
stars and their explosive outcomes, stripped-envelope
supernovae (SESNe), represent a long-term challenge for astrophysics. The latest results support a continuous distribution within the traditional SESN subclasses (IIb, Ib, Ic). The nearby ($D \approx 17.5$ Mpc) SN 2026dix seems to be another member of the recently identified group of transitional Type IIb/Ib explosions. A point source is located at the SN position within the uncertainties on multiple pre-explosion HST images. Together with post-explosion photometry and spectroscopy, it provides a good opportunity to study a rare type of SN in detail. We carried out a thorough comparative light-curve (LC) and spectral analysis of SN 2026dix. We also constructed its bolometric LC and modeled it semi-analytically. In addition, we constructed the spectral energy distribution of the presumed progenitor and compared this to model stellar atmospheres and binary stellar
evolution tracks. We infer that SN 2026dix arose from an explosion in an interacting binary system, consistent with the properties of a warm ($T_\textrm{eff} \approx 6750-$7750 K; spectral type F2 to A7), luminous ($\log(L_{\rm bol}/L_{\odot})\approx 4.9-5.3$) supergiant primary and a less luminous, less massive hot dwarf companion. The nature of the identified progenitor closely resembles that of some other known cases of SNe IIb and also well aligns with both the results of our semi-analytical LC modeling and the comparison of the LCs and spectra of SN 2026dix with the output of radiative-transfer models of an exploding
star with $M_\textrm{ini}$ = 18 $M_{\odot}$.
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All authors Tamás Szalai, Schuyler D. Van Dyk, Dominik Bánhidi, Andrea P. Nagy, Réka Könyves-Tóth, Alexei V. Filippenko, Thomas G. Brink, WeiKang Zheng, Imre Barna Bíró, István Csányi, Zsófia Bora, Zsóka Horváth, Ágoston Horti-Dávid, András. P. Joó, Dávid Koller, Levente Kriskovics, Klára Lelkes, Katalin Nagy, Krisztián Sárneczky, Ádám Sódor, Róbert Szakáts, András Pál, József Vinkó
Earth and Planetary Astrophysics
JWST MEP - A World Under Spotty Starlight: Detection of CO2 and H2O in the Hot Saturn WASP-52b with JWST NIRSpec G395H
JWST GO 3969 Team: Yanbo Pan, Ryan J. MacDonald, Néstor Espinoza et al. (+20 more)
Exoplanets orbiting active
stars offer distinct challenges for atmospheric characterization with the JWST. Among such worlds, the hot Saturn WASP-52b (Teq $\sim$ 1300 K) orbits an active K-dwarf that complicates transmission spectroscopy via stellar contamination. Here, we present the first JWST NIRSpec G395H (2.8-5.2 $\mu$m) limb-averaged transmission spectrum of WASP-52b obtained through the JWST Morning/Evening Program (GO-3969), which aims to measure limb asymmetries across a sample of hot giant
exoplanets. Our spectrum reveals the first detection of CO2 in WASP-52b's atmosphere (ln B = 54 / >10$\sigma$), with a retrieved abundance of log CO2 = -5.09 (+1.09/-1.14), and confirmation of H2O (ln B = 5.9 / $\sim$3-4$\sigma$), with an abundance of log H2O = -3.41 (+1.04/-1.04). We find a steep near-infrared slope that cannot be explained solely by H2O absorption, necessitating unocculted starspots (ln B = 5.7 / $\sim$3-4$\sigma$), though with properties that vary across our data reductions. The shape and amplitude of the molecular bands additionally suggest high-altitude (<10 mbar) inhomogeneous clouds covering $\approx$40 $\pm$ 20% of the terminator (ln B = 1.9 / $\sim$2.5$\sigma$), which provides evidence for the morning-evening terminator differences that are consensus predictions of general circulation models. WASP-52b's atmospheric
metallicity can be sub-solar, solar, or super-solar, due to order-of-magnitude uncertainties in the molecular abundances caused by degeneracies between compositions, clouds, and starspots. However, chemical
equilibrium retrievals provide a similar statistical fit while favoring a tighter constraint with a super-solar
metallicity (M/H = 14.8 (+12.1/-5.9) $\times$ solar). These results highlight that chemical detections and aerosol properties may still be recovered for
planets orbiting active
stars via transmission spectroscopy.
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All authors JWST GO 3969 Team: Yanbo Pan, Ryan J. MacDonald, Néstor Espinoza, Bibiana Prinoth, Zafar Rustamkulov, Luis Welbanks, Daniel Kitzmann, Nicolas Crouzet, Anna Walde, Diana Powell, Eva-Maria Ahrer, Adam J. Burgasser, Duncan A. Christie, Wolf Cukier, Carlos Gascón, Måns Holmberg, Thomas Kennedy, Mercedes López-Morales, N. J. Mayne, Dominic Samra, Arjun B. Savel, Maria E. Steinrueck, Christopher P. Wirth
Cosmology and Nongalactic Astrophysics
FLUMEN: Neural Emulator of an Advanced Stochastic Weak Lensing Model
Galymzhan Baltabay and Ville Vaskonen
Weak gravitational
lensing by intervening structure magnifies distant sources and induces scatter in their luminosity distances. We develop an improved
stochastic model for the distribution of weak
lensing magnifications, $\textrm{d} P/\textrm{d}\mu$, that resolves individual lenses down to $10^7\,M_\odot$ and, besides field
halos and filaments, includes subhalos and large-scale clustering of the lens population. Both extensions broaden the distribution, and the resulting scatter in the luminosity distances agrees with the
halo-model prediction from the nonlinear matter power spectrum and exceeds that obtained from $N$-body ray tracing, which we attribute to the finite mass resolution and box size of the simulations. Building on this model, we develop FLUMEN, a conditional normalizing-flow emulator that predicts $\textrm{d} P/\textrm{d}\mu$ as a function of the source
redshift up to $z_s=12$ and six cosmological parameters $\{h,\Omega_M,\Omega_B,\sigma_8,n_s,z_{\rm eq}\}$. The emulator enforces the empty-beam cutoff and the fold-caustic power-law tail analytically, and reproduces the Monte Carlo distributions on held-out cosmologies with a median Kullback–Leibler divergence of $0.0048$ at negligible cost. Our results provide a fast and flexible framework for incorporating the full magnification distribution into cosmological analyses of standard sirens,
supernovae, and other point sources.
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Cosmology and Nongalactic Astrophysics
High Resolution Grid-based Simulations of the Warm-Hot Intergalactic Medium
Lile Wang and Renyue Cen
We present high-resolution cosmological hydrodynamic simulations of the Warm-Hot Intergalactic Medium (WHIM) using the GPU-optimized grid-based hydrodynamic code Kratos. Employing a uniform 4096^3 grid in a (100 h^-1 Mpc)^3 comoving volume, we achieve a spatial resolution of ~24.5 h^-1 kpc, sufficient to resolve the Jeans scale of gas at T ~ 10^4 K and n_H ~ 10^-3 to 10^-2 cm^-3. This calculation ranks among the largest grid-based cosmological hydrodynamic simulations performed to date. We find that ~23.4% of
cosmic baryons reside in the WHIM phase (T = 10^5 - 10^7 K) at z = 0, significantly below the 40-50% found in earlier, lower-resolution simulations. Through a suite of lower-resolution simulations, we demonstrate that spatial resolution plays a pivotal role in determining the WHIM fraction: resolving gas near its Jeans scale allows it to reach higher densities, where enhanced radiative cooling transfers a substantial fraction of baryons out of the WHIM temperature range. The remaining WHIM resides predominantly in filaments and
accretion-shock structures in the vicinity of
halos, where hierarchical structure formation and ongoing hydrodynamic
accretion provide continued shock heating. Synthetic observations of Lyman-alpha, O VI, O VII, and O VIII emission reveal distinct morphological and kinematic signatures, with O VI tracing filament-
halo interfaces and the X-ray lines probing hotter gas associated with massive
halos. These predictions underscore the importance of current and future missions such as XRISM, ATHENA, and HUBS for mapping WHIM thermodynamics and kinematics.
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Solar and Stellar Astrophysics
Stability Analysis of the Proton Hammerhead Distribution Observed by Parker Solar Probe: Linear Theory and Fully Kinetic Simulations under Idealised Conditions
L. Pezzini, J. L. Verniero, F. Bacchini et al. (+3 more)
The non-adiabatic heating of the slow Solar Wind (SW) remains an open problem, with wave–particle interactions as a primary candidate mechanism. Novel in situ Parker Solar Probe (PSP) observations reveal strongly perpendicular anisotropic velocity distribution functions (VDFs), called "hammerhead", correlated with intense wave activity. These VDFs are systematically measured at the Heliospheric Current Sheet (HCS), making the hammerhead an important kinetic signature of the slow SW. In this work, we employ a fully kinetic particle-in-
cell approach, complemented by a linear Vlasov solver to cross-validate the simulation results, to investigate the stability of these VDFs, the timescales over which they evolve, and their interaction with
plasma waves. Our main findings indicate that the hammerhead distribution is primarily susceptible to drift-type instabilities, while energy is nonlinearly transferred back to the
plasma through a combination of Landau and cyclotron resonances, resulting in net heating in the parallel direction, preferentially energizing the beam
proton population. Crucially, these nonlinear interactions do not drastically alter the morphology of the distribution. This suggests the possibility that the hammerhead may be generated locally within the HCS in the inner heliosphere and subsequently advected outward, where it is eventually measured by PSP. This work lays the ground for future investigations into the kinetic physics of the HCS.
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All authors L. Pezzini, J. L. Verniero, F. Bacchini, A. N. Zhukov, G. Arrò, R. A. Lòpez
High Energy Astrophysical Phenomena
Core-collapse supernovae 2022prr, 2023ucy, and 2024ljc in the luminous infrared galaxy NGC 6745
K. K. Matilainen, E. Kankare, T. Nagao et al. (+19 more)
The core-collapse
supernovae (CCSNe) 2022prr, 2023ucy, and 2024ljc exploded within the central regions of the nearby luminous infrared
galaxy (LIRG) NGC6745. We present our follow-up data with the aim to characterise the spectrophotometric
evolution of these CCSNe, determine their host-
galaxy extinction, and to define their physical nature. The presented spectrophotometric data set covers the optical and near-infrared region for our three
supernovae (SNe). The data are analysed and compared to other hydrogen-rich CCSNe, and a host-
galaxy extinction value Av is derived based on broadband photometry for each of the targets. A spectral energy distribution (SED) for the host
galaxy is constructed, and a combination of different galactic components are fitted to the SED to estimate the intrinsic CCSN rate and the age of the starburst of NGC6745. 2022prr is a SN2009ip-like event, whose light curve
evolution consists of two consecutive luminous events A and B with peak magnitudes of Mr = -14.8 and -18.3 mag, respectively. The high degree of V and R-band polarisation (P=2.8%) near maximum light suggests interaction with highly aspherical circumstellar material. The spectral
evolution of the SN is dominated by narrow Balmer emission lines, which have a complex
evolution over time. 2022prr joins the growing sample of SN2009ip-like events that show early `flash ionisation' features of CIII, NIII, and HeII. 2023ucy is found to be a normal Type IIP SN. However, 2024ljc is a rapidly evolving Type IIb SN with a post-maximum r-band decline of roughly 3.2 mag by +41 d whereas normal IIb SNe decline typically by 1.5+/-0.3 mag during the same timescale. While the events exploded in a LIRG, the SNe are obscured by only moderate V-band host extinctions ranging from 0 to 1 mag. Based on the SED modelling we estimate an age of the host starburst to be 40Myr, and the intrinsic CCSN rate to be 0.4+/-0.1 SN/year.
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All authors K. K. Matilainen, E. Kankare, T. Nagao, T. Reynolds, A. Efstathiou, S. Mattila, C. R. Angus, A. Reguitti, Y.-Z. Cai, M. Fraser, L. Galbany, M. González-Bañuelos, C. P. Gutiérrez, T. Kangas, T. L. Killestein, T. Kravtsov, P. Lundqvist, S. Moran, A. Pastorello, A. Popowicz, I. Salmaso, M. Stritzinger
High Energy Astrophysical Phenomena
Beyond Disk Truncation: X-ray Reverberation Signatures of an Outflowing Corona
Ke Qin, Bei You, Adam Ingram et al. (+1 more)
The corona in black hole X-ray binaries (BHXRBs) is likely dynamic during outbursts. A mildly relativistic outflowing corona has been proposed to explain hard spectra, weak disk reflection, and the higher than expected polarization degree observed in the hard state of X-ray binaries. In this work, we investigate the spectral and timing effects of coronal outflow using Monte Carlo radiative-transfer simulations. The model consists of a geometrically thin, optically thick truncated disk and an ellipsoidal corona with a prescribed bulk outflow velocity. We calculate the Comptonized continuum, the disk reflection component, and the lag-frequency spectra for different outflow velocities and disk truncation radii. We find that increasing the outflow velocity reduces the reflection fraction through relativistic beaming, because fewer Comptonized
photons irradiate the disk. For $\beta \lesssim 0.5$, the high-frequency soft lag is only weakly affected by the outflow velocity, whereas increasing the disk truncation radius shifts the zero-crossing frequency($\nu_0$) to substantially lower frequencies. Thus, timing properties can help distinguish the coronal-outflow scenario from the disk-truncation scenario. We further apply the model to MAXI J1820+070 and find that its unusual $R-\Gamma$ anti-correlation during the plateau phase is qualitatively consistent with a contracting corona accompanied by increasing bulk velocity. Disk recession alone would predict the opposite
evolution of $\nu_0$ under the assumptions of our model. Future polarization calculations will provide an additional test of extended outflowing-corona models.
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All authors Ke Qin, Bei You, Adam Ingram, Barbara De Marco
Earth and Planetary Astrophysics
Some challenges for the long-term survival of Naiad, Neptune's innermost moon
Harrison Agrusa, Matija Ćuk, David Nesvorný et al. (+1 more)
The Naiad-Thalassa 73:69 mean-motion resonance implies these moons have co-existed for $\gtrsim$1 Gyr, raising the question of how they survived to the present day. We examine three challenges to Naiad's long-term survival: tidal disruption, heliocentric bombardment, and runaway collisional erosion by planetocentric debris. We constrain Naiad's internal strength requirements from its nominal density and shape, compute present-day impact rates on Neptune's inner moons from heliocentric bombardment, and use $N$-body simulations to model the fate of ejecta produced by non-disruptive impacts. First, Naiad's nominal density of ${\sim}0.8\text{ g cm}^{-3}$ and elongated shape suggest it cannot be held together by self-
gravity alone, implying a cohesive strength of $\gtrsim10$ kPa to avoid tidal disruption, although this constraint is relaxed if Naiad has a higher density of ${\gtrsim}1.3\text{ g cm}^{-3}$. Second, we show that Naiad may have been disrupted in the last 1 Gyr by heliocentric bombardment, although this depends sensitively on the size-frequency distribution of Kuiper Belt objects at small sizes and on Naiad's catastrophic disruption threshold, both of which are poorly constrained. Third, and most notably, we find that even small, non-disruptive impacts can trigger runaway collisional erosion by planetocentric debris on extremely short timescales. Avoiding this “sesquinary catastrophe” requires that Naiad has a collisional strength of at least several MPa, which is difficult to reconcile with being a reaccumulated “rubble pile”, leftover from the capture of Triton and the subsequent cataclysm of Neptune's primordial satellite system. Together, these results suggest that Naiad may be a physically unusual object among small ring-moons – possibly a largely coherent, monolithic fragment – and that our understanding of Neptune's inner satellite system leaves much to be explained.
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All authors Harrison Agrusa, Matija Ćuk, David Nesvorný, David Minton
High Energy Astrophysical Phenomena
X-ray polarization of the Compton-thin Seyfert galaxy NGC 5506 with IXPE
Daniele Tagliacozzo, Alessandro Leonardo Lai, Andrea Gnarini et al. (+14 more)
We report on the observation of the Compton-thin Seyfert
galaxy NGC~5506 performed with the Imaging X-ray Polarimetry Explorer (IXPE). The observation, with a net observing time of 975~ks, was partly simultaneous with NuSTAR (52~ks) and XMM-Newton (37~ks). Using a simple baseline model with IXPE data only, we find an upper limit on the 2–8~keV polarization fraction at the $99\%$ confidence level: $\Pi<3.1\%$. We then performed a spectropolarimetric analysis combining data from the three X-ray observatories. While pure spectral modeling confirms the presence of both relativistic and cold distant reflection, in addition to the primary continuum power law, their contributions lead to somewhat different constraints on the coronal $\Pi$, depending on the specific assumptions. We also performed Monte Carlo simulations with the radiative transfer code MONK, exploring various coronal geometries. Comparing these results with the IXPE data, and assuming a radially extended corona, as suggested by previous observations of similar sources, the corresponding polarization upper limits require inclination angles below 40{\deg}.
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All authors Daniele Tagliacozzo, Alessandro Leonardo Lai, Andrea Gnarini, Giorgio Matt, Stefano Bianchi, Francesco Ursini, Andrea Marinucci, Alessia Tortosa, Sudip Chakraborty, Federico Ferretti, Vittoria Elvezia Gianolli, Elias Kammoun, Frédéric Marin, Herman Marshall, Riccardo Middei, Romana Mikusincova, Dawoon Kim
High Energy Astrophysical Phenomena
COBALT-BLUE: a fast and accurate model for gravitational self-lensing binary systems
Danny J. Dixon, Adam Ingram, Matthew J. Middleton et al. (+5 more)
We present COBALT-BLUE, a fast public model for the optical light curve of a luminous
star in a non-accreting binary with a compact object. The model includes gravitational self-
lensing, Doppler beaming, ellipsoidal variations, eccentric orbital geometry, and wavelength-dependent limb darkening. In sufficiently edge-on systems, it predicts sharp periodic self-
lensing flares together with phase-locked orbital modulation outside the
flare. We improve upon earlier models by including non-linear limb darkening laws based on stellar atmosphere simulations to calculate the self-
lensing flare profile. This enables light curves to be self-consistently calculated in multiple wavebands from one set of physical parameters, thus offering the prospect of constraining binary parameters such as compact object mass from photometry alone if multiple self-
lensing flares are observed. We also include the option to utilise simpler limb darkening prescriptions to save computational expense. As a proof of principle, we fit our model to ZTF data of 14 candidate self-
lensing sources. The model describes the
flare morphology well for most candidates, but we find that the best fitting parameters are not physically plausible. We conclude that the observed
flares are most likely stellar
flares and not self-
lensing events. In future, we plan to use the model to systematically search optical survey data for signatures of binary motion.
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All authors Danny J. Dixon, Adam Ingram, Matthew J. Middleton, Adam McMaster, Grzegorz Wiktorowicz, Hugh Dickinson, Allison Crossland, Eric C. Bellm
Earth and Planetary Astrophysics
Amit Reza, Ludmila Carone and Christiane Helling
With the rapid advancement of
telescopes like JWST and Ariel, there is an urgent need for efficient 3D
climate models to interpret observations of
exoplanet atmospheres. Traditional 3D general circulation models (GCMs) are computationally intensive, prompting the development of machine learning (ML) emulators to accelerate simulations. Recent work, such as that by Plaschzug et al. 2026 \cite{plaschzug2026accelerating}, uses a dense neural network (DNN) to predict local gas temperatures and winds from input parameters, including local gas pressure, spatial coordinates (longitude and latitude), and global temperature. However, this model relies on predicting individual temperature values (points) at specific grid points, which can be limited by the resolution and constraints of the training grid. In this work, we investigate a couple of alternative frameworks based on latent-space representations of local gas temperature ($\text{T}_{\text{gas}}$) to obtain a faithful, low-dimensional representation of these profiles. This represents the first step toward developing a latent space regression model, offering a structurally cohesive alternative to the existing point-wise prediction method \cite{plaschzug2026accelerating}. By capturing the optimal
embedding space of atmospheric data, our proposed framework can produce simulated profiles while maintaining computational efficiency, making it suitable for large-scale
exoplanet ensemble studies.
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Astrophysics of Galaxies
Morphology classification for galaxies in the Kilo Degree Survey using a label-efficient self-supervised learning framework
Xu Huang, Rui Li, Liang Gao et al. (+14 more)
Galaxy morphology classification is fundamental to understanding
galaxy formation and
evolution. The advent of large-scale sky surveys has produced an unprecedented volume of
galaxy images, making traditional manual classification impractical. Although supervised deep learning can achieve high accuracy, it requires large labeled
datasets that are time-consuming to construct. In contrast, unsupervised methods often show limited classification performance. To address this limitation, we propose a label-efficient self-supervised learning framework for
galaxy morphology classification. Our method first learns robust morphological representations from 305,583 unlabeled KiDS
galaxy images through contrastive learning, and then trains a classifier using only 5,000 human-labeled images. The classifier separates
galaxies into five categories: elliptical, spiral, lenticular-disk, irregular, and "other." Using a ResNet-50 model with a crop size of 64x64 pixels, our approach achieves an overall test accuracy of up to 91.0% (90.5% +/- 0.2% on average) on the human-classified catalog. The corresponding F1 scores for elliptical, spiral, irregular, lenticular-disk, and "other"
galaxies are 0.96, 0.86, 0.86, 0.95, and 0.92, respectively. We apply this pipeline to the Kilo-Degree Survey Data Release 5 and produce a publicly available morphology catalog of 310,583
galaxies. This is the first morphology catalog for KiDS
galaxies and provides a valuable resource for future studies of
galaxy evolution. Our results show that self-supervised learning can substantially reduce the need for manual labels while maintaining high classification accuracy, making it a promising and scalable approach for automated
galaxy morphology classification in the era of large-scale surveys.
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All authors Xu Huang, Rui Li, Liang Gao, Liqing Chen, Hui Li, Huijun Mu, Hao Su, Fucheng Zhong, Zhenping Yi, Xiaoyue Cao, Ran Li, Haicheng Feng, Nicola N. Napolitano, Yue Dong, Yida Deng, Sihan Li, Kang Jiao
Cosmology and Nongalactic Astrophysics
Lens Modeling and Cosmological Inference from an Impure Sample of Galaxy-Galaxy Strong Lenses
Philip Holloway, Aprajita Verma, Philip J. Marshall et al. (+7 more)
The start of the Legacy Survey of Space and Time marks a new era for strong
lensing science, where the number of strong lenses identified is expected to increase to $\mathcal{O}(10^5)$. In this paper we use a neural network to determine the precision with which lens parameters can be determined, using realistic simulated LSST lensed systems. We find that the Einstein radius can be measured with a mean precision of $3.7\%$ with calibrated uncertainties accurately reflecting the corresponding measurement error. Based on the performance of current strong lens classifiers, the $\sim 100,000$ detectable strong lenses are expected to be accompanied by a similar or larger number of false positives (non-lenses). In readiness for this we introduce a formalism, termed `
COSMIC-BEAMS', to infer cosmological parameters while accounting for contamination by false positives. As a proof-of-concept, using simulated LSST measurements of the Einstein radii of a realistic and impure sample of photometric lens systems, i.e. those without spectroscopic confirmation, we find that the cosmological parameters $\Omega_m$, $\Omega_\Lambda$, and $w$ can be measured to a precision of $0.1$, $0.03$ and $0.15$ respectively for a $w$CDM cosmology. We demonstrate that unbiased cosmological parameters can be inferred even in strong lens samples contaminated by $50\%$ false positives, and that the photometric
dataset of $100\,000$ strong lenses will provide equivalent $w$-precision to $2500-3500$ spectroscopic systems.
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All authors Philip Holloway, Aprajita Verma, Philip J. Marshall, Padmavathi Venkatraman, Sydney Erickson, Tian Li, Simon Birrer, Steven Dillmann, Thomas E. Collett, the LSST Dark Energy Science Collaboration
Instrumentation and Methods for Astrophysics
Bayesian classification of astronomical spectra with class uncertainties
Simon Barton, Martin Sahlén, Andreas Korn et al. (+1 more)
Context: We developed a probabilistic machine learning method with the aim of performing the O(10)-way classification of low- and high-resolution spectra of stellar and extragalactic targets for the upcoming 4MOST survey. In fulfilment of the survey requirements, this method should be able to express uncertainty in the input data as well as uncertainty introduced in its prediction. Aims: Four different methods are explored: (1) convolutional neural networks (CNNs), (2) the Dirichlet distribution, (3) Monte Carlo dropout (MCD), (4)
Bayesian neural Networks (BNNs) + variational inference (VI). Training and validation was performed using labelled spectra from the SDSS database and a custom 4MOST mock
dataset. All the methods were compared in terms of the same metrics: accuracy, area under the curve (AUC), expected calibration error (ECE), Shannon
entropy, negative log-likelihood (NLL), Brier score, training time, and inference time. Methods: A CNN with simple architecture and about 20,000 parameters was trained to achieve classification accuracies of 91.5% on SDSS data and 92.8% on 4MOST mock data. The direct Dirichlet prediction and VI models tested provide uncertainties on class membership probabilities, but they confuse classes more often. The MCD on a CNN is found to be the most suitable; it boosts the point-estimate accuracies to 92.6% and 93.9%, while still providing fast training and sufficiently fast inference. Compared to a standard CNN, the method additionally provides well-calibrated uncertainties at marginal extra cost.
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All authors Simon Barton, Martin Sahlén, Andreas Korn, Christian Glaser
Astrophysics of Galaxies
LenNet: Direct Detection and Localization of Strong Gravitational Lenses in Wide-Field Sky Survey Images
Pufan Liu, Hui Li, Ziqi Li et al. (+9 more)
Strong gravitational lenses are invaluable tools for addressing fundamental questions in astrophysics, from the nature of dark matter to the expansion of the universe. While current sky surveys have successfully identified thousands of lens candidates, the search methods employed face a critical challenge. The conventional approach relies on a "crop-and-classify" strategy, where small images are first cut out around billions of potential host
galaxies before being individually classified. This process creates a significant computational and storage bottleneck that is unsustainable for future large-scale surveys. To overcome this limitation, we propose LenNet, an object detection model that identifies lenses directly within large, original survey images. Our method completely bypasses the inefficient cropping step by framing the problem as a direct detection and localization task. We initially train LenNet on simulated data to learn the complex features of gravitational lenses and then use transfer learning to fine-tune the model on a limited set of real, labeled examples from the Kilo-Degree Survey (KiDS). Our experiments show that LenNet performs remarkably well on real survey data, validating its potential as a highly efficient and scalable solution for lens discovery in massive astronomical surveys.
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All authors Pufan Liu, Hui Li, Ziqi Li, Xiaoyue Cao, Rui Li, Hao Su, Ran Li, Nicola R. Napolitano, Léon V. E. Koopmans, Valerio Busillo, Crescenzo Tortora, Liang Gao
Instrumentation and Methods for Astrophysics
Identification of gravitational lenses obscured by foreground light in the KiDS dataset using U-Nets and ResNets
S. Liu, Rui Li, J. Jia et al. (+13 more)
*Context.* Many
lensing images are often obscured by foreground light from the central
galaxies, making them challenging to detect. *Aims.* To address the limitations of previous lens search efforts, particularly for samples with smaller $R_E$ or faint lensed images, we developed a composite convolutional neural network framework that utilizes both U-Net and ResNet architectures for feature extraction and classification. *Methods.* We propose a hybrid search method that combines U-Net and ResNet architectures to enhance the detection of foreground
galaxy-obscured lenses. Our approach consists of two main stages: first, the U-Net model separates the foreground
galaxy light from potential
lensing signals, creating residual images that highlight the
lensing features. Next, the ResNet module performs binary classification on these residual images to detect
lensing signals. *Results.* We evaluated the hybrid search method with real observational data to demonstrate its effectiveness, achieving a recall of 71.5% and a 4.5% false positive rate at a confidence threshold of 0.6. Applying this method to over 638,398
galaxy samples from the Kilo-Degree Survey Data Release 4 and conducting thorough inspections, we identify 88 Class A, 322 Class B, and 1,758 Class C candidates. *Conclusions.* This hybrid approach significantly enhances the completeness of existing strong gravitational
lensing searches and shows great potential for improving future astronomical surveys.
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All authors S. Liu, Rui Li, J. Jia, Hui Li, Liqing Chen, Xiaoyue Cao, Zizhao He, Valerio Busillo, Nicola N. Napolitano, Crescenzo Tortora, Fucheng Zhong, Hao Su, Haicheng Feng, Yue Dong, Ran Li, Liang Gao
Astrophysics of Galaxies
KiDS J1447-0149: The first spatially resolved spectroscopy of a relic galaxy beyond the local universe. An old high-dispersion core embedded in a compact rotating stellar structure
Johanna Hartke, Chiara Spiniello, Michele Cappellari et al. (+13 more)
Relic
galaxies are the descendants of high-
redshift compact quiescent systems. We present the first spatially resolved spectroscopic study of J1447-0149, a massive relic at $z=0.21$, observed with MUSE+AO. We characterize its kinematics and stellar population properties to probe its spatially resolved mass assembly history. We measured stellar kinematics with sub-kpc bin sizes, covering $\sim 1.4$ effective radii. We then used a coarser three-bin configuration informed by the kinematics to recover the higher-order velocity moments, $[\alpha/{\rm Fe}]$, stellar age and
metallicity. We reconstructed the
star formation history and computed the degree of relicness (DoR). MUSE data reveal a velocity gradient, showing that J1447-0149 is not purely pressure supported. The velocity-dispersion field displays a central peak, reaching $\sigma_\star=233\pm13\,{\rm km\,s^{-1}}$, substantially larger than previous seeing-limited measurements ($\sigma_{\star} =187 \pm 9\,{\rm km\,s^{-1}}$). The $h_3$–$V_\star$ anti-correlation and mildly positive $h_4$ values support a composite structure, with a rotating stellar component surrounding a compact dynamically hot core. This central, dispersion-dominated region is also the oldest and most metal-rich component. Its SFH rises rapidly, with the stellar mass assembled within $\sim2\,{\rm Gyr}$ after the Big Bang, and reaches ${\rm DoR}=0.9^{+0.1}_{-0.2}$. The two outer bins have a DoR value of ${\rm DoR}=0.8\pm0.2$, consistent with the central bin, but possibly indicating slightly longer formation times. Spatially resolved spectroscopy has been crucial to confirm the relic nature of J1447-0149, linking resolved morphology, kinematics, and stellar populations to constrain the early assembly of its central spheroid and surrounding disk.
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All authors Johanna Hartke, Chiara Spiniello, Michele Cappellari, Davide Bevacqua, Enrico Congiu, Anna Ferré-Mateu, Adriano Poci, Claudia Pulsoni, Magda Arnaboldi, Giuseppe D'Ago, Michalina Maksymowicz-Maciata, Paolo Saracco, Diana Scognamiglio, David A. Simon, Crescenzo Tortora, Petri Väisänen
High Energy Astrophysical Phenomena
Wave-particle acceleration during supernova explosions
Zaza N. Osmanov and S.M. Mahajan
We investigate particle acceleration during the early stages of a
supernova explosion via a resonant interaction between electromagnetic waves and
quantum waves associated with particles. For typical progenitor masses of $(8; 12; 20)\times M_s$, we find that this mechanism can accelerate
protons to energies of up to $3\times 10^{14}$ eV. Interestingly, despite the continuously declining luminosity, the particle energy initially increases, reaches a maximum, and subsequently decreases, reflecting the characteristic behavior of the resonant acceleration mechanism.
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High Energy Astrophysical Phenomena
A method for enhanced gamma-proton discrimination with imaging atmospheric Cherenkov telescopes
Jianling Liu and Hu Liu
Purpose: Very-high-energy gamma-ray astronomy is an important window to study the extreme astrophysical processes in the universe, and how to effectively distinguish between gamma
photons and background signals (mainly
protons) is a key technical challenge to realize very-high-energy gamma-ray detection. Spaceborne calorimeters record secondary particle spatial distributions, achieving a background rejection power of 10000-100000 near 1 TeV. Ground-based imaging Cherenkov
telescopes measure Cherenkov
photon angular distributions, yet they only reach a rejection factor of about 10 in this energy range, leaving substantial room for optimization. Methods: We use CORSIKA and sim_telarray to simulate H.E.S.S. detector responses.
Photon emission positions are reconstructed from Cherenkov shower images. Inspired by analysis techniques for space-borne calorimeter, we propose new observables derived from the transverse distribution of Cherenkov
photon emission positions to separate gamma-ray signals from
proton backgrounds. We employ a likelihood-ratio method to combine single-
telescope variables across multiple
telescopes and compare its performance with conventional Hillas-based analysis. Results: The results show that observables built from the transverse distribution of Cherenkov
photon emission positions are less sensitive to Cherenkov image size and outperform the Hillas width parameter for single-
telescope gamma-
proton discrimination. Furthermore, the likelihood ratio combining width yields substantially better performance than the conventional mean reduced scaled width: the improvement reaches roughly one order of magnitude near 1 TeV, and this enhancement remains above 50% for energies above 10 TeV.
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Instrumentation and Methods for Astrophysics
Combining astrometry with pulsar timing: the first joint analysis of very low frequency gravitational waves
Lorenzo Filipello, William Beordo, Volodymyr Akhmetov et al. (+2 more)
The pHz to sub-nHz GW regime remains largely unexplored but is crucial for mapping the early inspiral stage of SMBHBs and probing early-Universe physics. Astrometry and
pulsar timing offer orthogonal and deeply complementary secular observables to investigate this frequency band. We aim to present the first joint data analysis combining real astrometric proper motions with binary
pulsar timing, to search for and constrain continuous gravitational waves (CWs) sourced by SMBHBs in the ultra-low-frequency regime ($10^{-12} \le f_{GW} \le10^{-9} Hz$). We employ a
Bayesian model selection and upper limit estimation framework to combine apparent proper motion displacements of $\sim 1.5 \times 10^6$
quasars from the Gaia CRF3 catalog with the line-of-sight orbital period derivatives ($\dot{P}_b$) of 11 high-precision binary
pulsars. To prevent spurious detections, we heavily model instrumental and astrophysical systematics: we propagate the Galactic potential uncertainty for
pulsars via Monte Carlo simulations and perform a Vector Spherical Harmonics (VSH) decomposition up to the octupole order (l=3) for
quasars. We find no statistically significant evidence for a CWs signal in the joint analysis ($\ln B_{joint} = -0.42 \pm 0.03$). In the absence of detection, we set the tightest constraints to date on CW strain in the pHz band, yielding a 95% upper limit of $h_0\le6.4x10^{-11}$ at a reference frequency of $f_{ref} = 4 \times 10^{-10}$ Hz. The combined
dataset achieves full sky coverage and improves single-
dataset upper limits by 20%-30%. Combining orthogonal observables successfully breaks spatial degeneracies intrinsic to isolated searches. Furthermore, forecasts from inj.-rec. indicate that with the extended temporal baseline and reduced uncertainties of the upcoming Gaia DR4, this joint framework is poised to break the $h_0 < 10^{-11}$ upper limit barrier for sub-nHz CWs.
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All authors Lorenzo Filipello, William Beordo, Volodymyr Akhmetov, Mariateresa Crosta, Mario Gilberto Lattanzi
Astrophysics of Galaxies
ALMA Chemical Evolution (ACE) survey: an overview – extending dust and gas inference to low metallicities at cosmic noon
Irene Shivaei, Gergő Popping, Leindert A. Boogaard et al. (+13 more)
The baryon cycle governs the exchange of gas, metals, and dust between
galaxies and their environments, but simultaneous constraints on these constituents remain scarce beyond z~1. The ALMA Chemical
Evolution (ACE) survey is a Cycle 11 ALMA Large Program designed to address this by studying the molecular gas, dust, and metal content of sub-solar
metallicity at
cosmic noon. ACE consists of CO(3-2) and dust continuum observations of 25
galaxies at z=2.0-2.5 with robust gas-phase
metallicity measurements spanning ~35% to 83% of solar
metallicity. The survey approximately doubles the number of unlensed main-sequence
galaxies at z>1 with CO, dust-continuum and
metallicity measurements and extends such studies to almost an order of magnitude lower stellar masses and
metallicities than previous surveys. The ACE observations yield 17 CO detections and 17 Band 7 continuum (rest-frame ~270um) detections. CO detectability correlates most strongly with
metallicity and stellar mass, while dust continuum detectability is more closely linked to
star formation rate (SFR) and infrared luminosity. Using the ACE measurements, we derive a new empirical scaling relation linking CO(3-2) luminosity to stellar mass, SFR, and
metallicity, providing a practical
benchmark for estimating molecular gas content in low-mass, low-
metallicity galaxies. The survey reveals several particularly intriguing systems, including some of the lowest-
metallicity CO and dust detections currently known at z>1,
galaxies with extreme gas and dust fractions, and systems exhibiting offsets between stellar, dust, and molecular gas emission. ACE provides the first comprehensive view of the interplay between molecular gas, dust, metals, and
star formation in sub-solar
metallicity galaxies at
cosmic noon, enabling direct tests of models for baryon cycling, chemical enrichment, and dust
evolution during the peak epoch of
galaxy assembly.
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All authors Irene Shivaei, Gergő Popping, Leindert A. Boogaard, Alexandra Pope, Ivanna Langan, Roxana Popescu, Nikki N. Geesink, Manuel Solimano, Caitlin M. Casey, Maximilien Franco, Melanie Kaasinen, Bahram Mobasher, Desika Narayanan, Pablo G. Pérez-González, Naveen Reddy, Ryan Sanders
Astrophysics of Galaxies
Hierarchical Hub Formation in Mon~R2: Evidence for Cloud-to-core Gas Flows
L. K. Dewangan, O. R. Jadhav, A. K. Maity et al. (+2 more)
We present a multi-scale kinematic study of the hub-filament system in Mon R2 using JCMT $^{13}$CO(3–2) and ALMA C$^{18}$O(1–0) observations to investigate how molecular gas converges toward the central hub and connects across cloud-to-core scales. The $^{13}$CO data reveal several velocity-coherent filaments with diverse position angles converging toward the central region hosting massive
stars and stellar clusters, where distinct velocity components become spatially superposed. Two dominant velocity regimes at $\sim$8.8–10.2 and $\sim$10.4–11.8 km s$^{-1}$ are identified, with their velocity separation decreasing toward the central hub. The position–position–velocity and longitude–velocity maps of the $^{13}$CO emission exhibit a butterfly/X-shaped morphology, consistent with converging motions. A phenomenological rotating-and-infalling envelope model reproduces the longitude-velocity morphology, indicating that rotation and infall may contribute to the observed kinematics, although the model does not uniquely identify the underlying mechanism. At higher resolution, the ALMA C$^{18}$O observations resolve the molecular gas into multiple velocity-coherent filaments spanning $\sim$8–13 km s$^{-1}$, with distinct kinematic domains at $\sim$9–10.5, 10.5–11.5, and 12–13 km s$^{-1}$ converging toward the hub. The ALMA and JCMT position-velocity diagrams show consistent velocity structures across their respective spatial scales, with the ALMA-resolved features embedded within the broader molecular-gas velocity field traced by JCMT, demonstrating a multi-scale kinematic connection. These results support a hierarchical picture in which converging flows and filamentary
accretion contribute to hub growth and ongoing
star formation in Mon R2, while other dynamical processes may also contribute to the observed kinematics.
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All authors L. K. Dewangan, O. R. Jadhav, A. K. Maity, Saurabh Sharma, Ram K. Yadav