Astrophysics of Galaxies
No evolution in the number density of little red dots from cosmic dawn to cosmic noon
Federica Loiacono, Roberto Gilli, Marco Mignoli et al. (+24 more)
We present our search for little red dots (LRDs) in the "J1030 field", a region of the sky around the $z\sim 6.3$
quasar SDSS J1030+0524, observed by the JWST EIGER program. Over 154 point-like sources selected in a JWST-based photometric catalog, we find five broad line emitters (with $FWHM \gtrsim 1000\ \rm km s^{-1}$) that are red ($F200W - F356W > 0$) and are undetected in the X-rays. We use these sources to derive the bolometric luminosity function (LF) of LRDs at $z = 2.4$ and $z = 4.5$. At $z = 2.4$, the space density of LRDs is only a factor of $\sim 2$ lower than that of all pre-JWST active
galactic nuclei (AGNs) with bolometric luminosity $L_{\rm bol} \gtrsim 3 \times 10^{44}\ \rm erg\ s^{-1}$. At $z = 4.5$, our estimate is consistent with those derived for LRDs based on larger areas of the sky. A similar behaviour is observed in the black hole mass function. More importantly, we study the number density of LRDs from
cosmic dawn to
cosmic noon. We find that there is no significant
evolution in the abundance of LRDs with $L_{\rm bol} \gtrsim 3 \times 10^{44}\ \rm erg\ s^{-1}$ at $z > 2$. We speculate that the drop at $z < 4$ seen by other studies is due to their sampling of only the bright-end of the LRDs LF. At
cosmic noon, the abundance of LRDs is $n = 3.4^{+5.6}_{-2.4} \times 10^{-5}\ \rm Mpc^{-3}$, which is a factor of $\sim 350$ larger than recent model predictions and is comparable with that of X-ray selected AGNs with similar bolometric luminosity. Our result may imply that, if LRDs are the early, rapid stages of supermassive black hole growth, as suggested by some models, then the formation of black hole seeds can be efficient down to epochs as recent as
cosmic noon. Alternatively, LRDs may simply be a high-
accretion phase in already mature black holes.
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All authors Federica Loiacono, Roberto Gilli, Marco Mignoli, Marcella Brusa, Francesco Calura, Marco Chiaberge, Andrea Comastri, Quirino D'Amato, Roberto Decarli, Ivan Delvecchio, Kazushi Iwasawa, Ignas Juodžbalis, Giorgio Lanzuisi, Roberto Maiolino, Stefano Marchesi, Giovanni Mazzolari, Colin Norman, Alessandro Peca, Isabella Prandoni, Matteo Sapori, Matilde Signorini, Paolo Tozzi, Eros Vanzella, Cristian Vignali, Fabio Vito, Gianni Zamorani, Anita Zanella
Cosmology and Nongalactic Astrophysics
Cosmology with Multi-Wavelength Line Intensity Mapping Synergies in the SKAO Era
Debanjan Sarkar, Suman Majumdar, Chandra Shekhar Murmu et al. (+21 more)
Line intensity mapping (LIM) has emerged as a powerful tool for surveying the large-scale structure of the Universe across
cosmic time by measuring spatial fluctuations in the cumulative emission of spectral lines from unresolved sources or the intergalactic medium. Besides the most abundant 21-cm hyperfine line of neutral hydrogen, there are bright far-infrared fine-structure lines like [CII] 158 $\mu$m, [OIII] 88 $\mu$m, [NII] 122/205 $\mu$m, and [OI] 63 $\mu$m, as well as mid-/high-$J$ CO rotational transitions, hydrogen Ly$\alpha$ and H$\alpha$ as potential LIM probes. A key opportunity lies in combining and cross-correlating 21-cm intensity maps from SKAO with other line intensity maps, targeted by a range of ongoing and forthcoming LIM experiments that probe overlapping
cosmic volumes. Cross-correlation between 21-cm maps and other line tracers mitigates uncorrelated systematics and enhances sensitivity to the underlying matter distribution, while multi-line analyses help disentangle cosmological and astrophysical parameters. Beyond cross-power spectra, higher-order and morphological statistics – such as cross-bispectra, marked correlations, and morphological measures – capture non-Gaussian features and the environmental dependence of structure formation. This chapter explores the synergies that can be achieved by combining SKAO observations with other line-intensity mapping experiments, demonstrating how such joint analyses can unlock new insights into
galaxy evolution and cosmology.
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All authors Debanjan Sarkar, Suman Majumdar, Chandra Shekhar Murmu, Leon Noble, Manas Mohit Dosibhatla, Vishrut Pandya, José Luis Bernal, Yashrajsinh Mahida, Mohd Kamran, Caroline S. Heneka, Anshuman Tripathi, Samit Kumar Pal, Gabriella De Lucia, Fabio Fontanot, Matteo Viel, Marta Spinelli, Parth Kothari, Sarah Libanore, Abinash Kumar Shaw, Martin Sahlen, José Fonseca, Abhirup Datta, Ziad Sakr, Wenkai Hu
Instrumentation and Methods for Astrophysics
Improving Beam Quality in Gravitational-Wave Interferometers Illuminated by Higher-Order Laguerre-Gaussian Modes
Liu Tao, Yuefan Guo, Alberto Gatto et al. (+5 more)
Higher-order Laguerre-Gaussian (LG)
laser modes have been proposed to reduce test-mass thermal noise in
laser interferometric gravitational-wave detectors, owing to their more homogeneous intensity profiles compared to the currently employed fundamental Gaussian beam. However, LG beams such as the LG$_{3,3}$ mode suffer significant beam quality degradation in Fabry-Perot arm cavities in GW detectors with realistic state-of-the-art mirror surface figure errors, due to scattering into degenerate modes of the same order, which are resonantly enhanced by shared cavity resonance conditions. In this work, we investigate an alternative ”donut-shaped” LG$_{0,\ell}$-like mode, specifically the LG$_{0,6}$ mode, and demonstrate strategies to improve its performance. These include the introduction of a tailored circular mirror mask with anti-reflective coating in the central region, which selectively increases the losses of parasitic degenerate modes while minimally impacting the LG$_{0,6}$ mode due to its limited overlap with the masked area. We further assess the marginal benefits of anticipated improvements in mirror surface figure errors and the potential reduction of cavity finesse. We demonstrate that these strategies can reduce the average contrast defect by more than two orders of magnitude and lower the mode loss by nearly a factor of five, achieving performance at or below the typical values observed in current detectors. This work opens up new research and development pathways for employing LG$_{0,\ell}$-type modes that achieve significant thermal noise reduction while maintaining beam quality and optical performance comparable to current gravitational-wave interferometers.
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All authors Liu Tao, Yuefan Guo, Alberto Gatto, Eleonora Capocasa, Jérome Degallaix, Massimo Granata, Matteo Tacca, Matteo Barsuglia
Instrumentation and Methods for Astrophysics
Operational capabilities and on-sky performance of SAMOS at the completion of science commissioning
Massimo Robberto, Stephen A. Smee, Robert H. Barkhouser et al. (+9 more)
We present the operational capabilities and on-sky performance of the SOAR Adaptive Module Optical Spectrograph (SAMOS) at the completion of its science commissioning phase. SAMOS is a Digital Micromirror Device (DMD)-based multi-object spectrograph and imager installed behind the SOAR Adaptive Module (SAM) ground-layer adaptive optics system. The instrument relays the full 3 x 3 arcmin AO-corrected field onto a large-format DMD, where each micromirror can direct light to either a spectroscopic or a parallel imaging channel. This architecture enables programmable slit-mask patterns that can be generated and reconfigured within seconds. SAMOS provides low-resolution spectroscopy over the 4000-10000 A wavelength range at resolving power R ~ 2500 and high-resolution spectroscopy (R ~ 10,000) in the 4500-5150 A and 6 000-7000 A bands. We summarize the operational workflow established during commissioning, including target acquisition, astrometric registration, DMD slit-mask generation, simultaneous imaging and spectroscopy, and automated data reduction. Science-verification observations demonstrate accurate target acquisition, reliable programmable slit-mask operation, multiplexed spectroscopy of crowded
stellar fields, wavelength-calibration accuracy of about 0.3 A, and end-to-end spectrophotometric calibration through the combination of imaging and spectroscopic data. These results establish SAMOS as a unique facility instrument that combines adaptive-optics-assisted imaging, programmable multi-object spectroscopy, and rapid slit-mask reconfiguration for efficient spectroscopic surveys, transient follow-up, and studies of crowded
stellar populations.
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All authors Massimo Robberto, Stephen A. Smee, Robert H. Barkhouser, Stephen C. Hope, John J. Piotrowski, Dana Koeppe, Mario Gennaro, Zoran Ninkov, Megan E. Donahue, Andrei Tokovinin, Randolph P. Hammond, Albert J. Harding
Cosmology and Nongalactic Astrophysics
Cosmology with Intensity Mapping via Statistics Beyond the Power Spectrum in the SKAO Era
Suman Majumdar, Debanjan Sarkar, Leon Noble et al. (+38 more)
The cosmological distribution of neutral hydrogen (HI) during the post-reionization era is highly non-Gaussian due to the underlying non-linear structure formation, complex
galaxy biasing, and potential
primordial non-Gaussianity. One needs higher-order (beyond two-point) statistics to maximally extract the non-Gaussian information out of the 21-cm intensity maps. This chapter summarizes the potential of several higher-order statistics, including voxel intensity distribution, emission line stacking, probability density functions, $\ell_1$-norm, bispectrum, and various marked statistics. Additionally, image-based morphological descriptors, such as the Largest Cluster Statistic, local dimensions, and Minkowski functionals, etc., can potentially characterize the morphology and geometry of the
cosmic web encoded in the 21-cm intensity maps. This chapter presents forecasts of the detectability of these higher-order statistics in the context of the future SKAO observations. These forecasts incorporate instrumental noise, observational effects, and, in some cases, foreground removal in their analyses. With its unprecedented sensitivity, the future SKAO 21-cm observations will enable us to measure these higher-order statistics more precisely, possibly helping to break degeneracies between astrophysical and cosmological parameters, and maximizing the science outcome from these surveys.
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All authors Suman Majumdar, Debanjan Sarkar, Leon Noble, Manas Mohit Dosibhatla, Zhaoting Chen, Bernhard Vos-Ginés, Vishrut Pandya, Mohd Kamran, Sourav Pal, Chandra Shekhar Murmu, Cora Uhlemann, Pauline Gorbatchev, Jean-Luc Starck, José Luis Bernal, Marta Spinelli, Caroline S. Heneka, Matteo Viel, Gabriella De Lucia, Fabio Fontanot, Stefano Camera, Steve Cunnington, Benedetta Spina, Dionysis Karagiannis, Samit Kumar Pal, Anshuman Tripathi, Sarah Libanore, Abinash Kumar Shaw, Rajesh Mondal, Yashrajsinh Mahida, Yashar Akrami, Philip Bull, Chris Clarkson, Abhirup Datta, José Fonseca, Yin-Zhe Ma, Roy Maartens, Liantsoa F. Randrianjanahary, Martin Sahlen, Xin Wang, Yougang Wang, Jochen Weller
Instrumentation and Methods for Astrophysics
Radiation effects and noise evolution in NewAthena WFI flight-production sensors
Valentin Emberger, Johannes Müller-Seidlitz, Luisa Ostler et al. (+7 more)
The Wide Field Imager (WFI), one of the two instruments on ESA's next large X-ray observatory NewAthena, is designed for imaging spectroscopy in the 0.2-15 keV range, combining a large field of view with high count-rate capability. Its focal plane is equipped with back-illuminated DEPFET (Depleted p-channel field-effect transistor) sensors that offer high radiation tolerance and provide near Fano-limited energy resolution. Achieving this performance requires an exceptionally low readout noise, with about 3 electrons ENC expected at beginning of life. Consequently, the devices are highly sensitive to radiation-induced changes in noise behavior. In this work, we investigate the impact of both total non-ionizing dose (TNID) and total ionizing dose (TID) on the relevant noise components, including their temperature dependence. A detector module containing a 64x64-pixel sensor from a flight-production wafer was irradiated with 62.4 MeV
protons at the MedAustron accelerator facility in Wiener Neustadt to a total dose equivalent to 2.6 $\cdot$ 10$^9$ 10-MeV-
protons/cm$^2$. The detector was fully biased and operated throughout the irradiation and subsequent measurements, maintaining the nominal operating temperature of 213 K. To study short-term annealing behavior at low temperature, a second, identical module was exposed to a comparable
proton dose within a much shorter timescale by exploiting the available high beam flux. TID effects were investigated separately by irradiating another device with 17.4 keV Mo-K_alpha X-rays to a total dose of 15 Gy. We report the resulting changes in readout noise, dark current, and threshold voltage, and compare them with results from an earlier irradiation campaign using pre-flight sensors. Implications for the instrument's required operating temperature and its expected end-of-life performance are discussed.
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All authors Valentin Emberger, Johannes Müller-Seidlitz, Luisa Ostler, Wolfgang Treberer-Treberspurg, Robert Andritschke, Annika Behrens, Günter Hauser, Peter Lechner, Astrid Mayr, Leonie Sommer
Instrumentation and Methods for Astrophysics
Spectroscopic performance of the electrical functional models for the eXTP SFA-T detectors
Alexander Altmann, Robert Andritschke, Valeria Antonelli et al. (+11 more)
The Spectroscopy Focusing Array (SFA) is one of the three instruments on the eXTP satellite. It consists of six
telescopes plus focal plane cameras, where five are equipped with a Silicon Drift Detector (SDD) array. These five SFA-T (T stands for timing) instruments are used for observations with high time resolution (better than 10 microseconds), high throughput (dead time less than 5 % when observing a 1 Crab source), and good energy resolution (better than 180 eV at 6 keV). This paper presents the spectroscopic performance of the Electrical Functional Modules (EFM) for SFA-T that are assembled and tested at the Max Planck Institute for Extraterrestrial Physics (MPE). A focus lies on the energy resolution at the planned sensor operating temperature of -45 {\deg}C. Additionally, the use of a baffle that covers the pixel edges is studied.
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All authors Alexander Altmann, Robert Andritschke, Valeria Antonelli, Thomas Bechteler, Vadim Burwitz, David Fink, Carlo Fiorini, Max Goretti, Pia Knopp, Peter Lechner, Norbert Meidinger, Jonas Muegge, Christian Sandow, Rafael Strecker
Earth and Planetary Astrophysics
CO snow lines are stabilised by the vertical transport of volatiles
Alfie Robinson, James E. Owen and Richard A. Booth
Volatile
evolution in protoplanetary discs determines the compositional
evolution of forming
planets. Below their sublimation temperatures, volatiles freeze out from the vapour phase onto
dust grains in the disc and transition to being dynamically-coupled to the
dust component as opposed to the gas. The boundary between the ice and vapour phases is referred to as the snow line, when thought of as the mid-plane radius at which the phase transition occurs, or the snow surface, when viewed as a 2D (radial and vertical) structure in the disc. We investigate whether the CO snow line (and therefore snow surface) is thermally unstable and therefore liable to changes in its location during disc
evolution using the disc
evolution code cuDisc, to which we have added an ice-vapour chemistry solver. We find that the instability does lead to there being two steady-state stable
equilibrium solutions for the snow surface when including the vertical structure. However, in dynamically-evolving simulations, the disc does not enter a limit-cycle - as seen in previous 1D models - due to the shape of the 2D snow surface and the vertical transport of volatiles. We therefore expect that dynamically
evolution of snow lines due to instability is limited to transient,
stochastic events rather than oscillatory behaviour with a regular period. However, we also expect the snow surface to evolve substantially during the disc lifetime solely due to changes in the thermal structure driven by
evolution of the
dust spatial structure and grain-size distribution - this we will explore in future models.
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Cosmology and Nongalactic Astrophysics · Cross-listed from gr-qc
Wave Optics Effects from Gravitational Wave Propagation Through Dark Matter Halos
Annamalai P. Shanmugaraj, Roland Haas, Erik Schnetter et al. (+1 more)
Gravitational wave (GW) propagation is usually studied under the
geometric optics approximation. But when GWs propagate through structures of sizes similar to their wavelength, this approximation breaks down. Going beyond the
geometric optics approximation allows us to explore the wave optics effects in curved background that appear in such cases. In this work, we present a scheme for numerically evolving linearised plane GWs through stationary, spherical astrophysical structures in both weak and strong
gravity regimes. Our simulations evolve the full Einstein equations (with all 10 components) for Gaussian, NFW and Burkert potentials, although in simplified form for the two latter. Our simulations show that the scattering of the GWs depends not only on the mass of the lens but also strongly on the gravitational potential distribution of the lens. We isolate the effects of diffraction by setting the wavelength of GW to be less than the Schwarzschild radius of the structure. Among our most important results, we find that the GWs do not propagate along null geodesics when propagating through the Gaussian density, neither in the strong nor weak
gravity setting. We also find that for the Burkert potential, the convexity of the plane wave is flipped when leaving the structure, in the strong
gravity case. We compare our results with the linearized scalar wave predictions and find that the difference between these and the exact GW modes are of order one when the wave is inside the central potential. However, the difference reduces to only a few percent when the wave has passed through the structure. Although these effects are small, future GW detectors and
Pulsar Timing Arrays (PTAs) could be sensitive to these signals which could thus potentially help in constraining the structure of dark matter spikes or
halos.
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All authors Annamalai P. Shanmugaraj, Roland Haas, Erik Schnetter, Sofie Marie Koksbang
High Energy Astrophysical Phenomena
Joint population and strong-lensing inference for resolved gravitational-wave events probes the black-hole merger rate beyond the peak of star formation
Matthew Mould
Gravitational waves can be lensed by intervening potentials of various scales. Strong
lensing leads to underestimated distances and overestimated masses, biasing astrophysical results if not accounted for. I present a novel analysis of the LIGO-Virgo-KAGRA catalog of binary black-hole mergers, simultaneously inferring (1) whether or not each event is strongly lensed, (2) their magnifications if so, and (3) the underlying merger population, using both parametric and nonparametric population models as well as two models for the
lensing optical depth. Posterior
lensing probabilities do not exceed 1% for any event, so population constraints are consistent with those assuming nondetection of strong
lensing or that
lensing never occurs. This includes multiple subpopulations over black-hole mass and a component with high aligned
spins. Compared to standard analyses, however, there are reductions of order 10% in uncertainty on the
redshift at which the merger rate peaks and an order of magnitude in high-
redshift rate upper limits. Though modest, these are the first constraints using only resolved events at
redshifts where current ground-based gravitational-wave detectors are usually insensitive, at and beyond the peak of
star formation.
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High Energy Astrophysical Phenomena
Optimising transient discovery with Swift-XRT
S. Srivastava, P. A. Evans, M. R. Goad et al. (+1 more)
The Living Swift-XRT Point Source Catalogue (LSXPS) enables near real-time searches for X-ray transients. Many detected candidates are faint, often near the XRT detection limit, and are classed as "low significance," as it is often unclear whether their apparent brightening reflects a genuine transient or a statistical fluctuation. Some of these sources are affected by Eddington bias, a statistical effect that inflates measured fluxes near the detection threshold. We present a simulation-based
Bayesian framework that corrects for this bias and provides more accurate probabilities for each source being truly transient, i.e. that its true intensity exceeds the historical 3$\sigma$ upper limit. Applied to LSXPS data, this method yields more reliable classifications, recovering over 500 transients above this threshold – more than an eight-fold increase over the original confirmed sample. Using extensive simulations based on real Swift-XRT images, we validate the robustness of this approach, showing that it remains stable across varying exposure times and background conditions. These results demonstrate that the LSXPS transient probabilities, corrected for Eddington bias, provide a reliable and internally consistent framework for real-time X-ray transient identification.
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All authors S. Srivastava, P. A. Evans, M. R. Goad, R. A. J. Eyles-Ferris
Solar and Stellar Astrophysics
Far-ultraviolet flux distribution in Orion and its relation to stellar accretion
Rossella Anania, Andrew J. Winter, Miguel Vioque et al. (+8 more)
Orion is the closest region hosting active
star formation and young OBA
stars. Computing far-ultraviolet (FUV) fluxes at its
stars is essential to connect
stellar and protoplanetary disc properties to the environment. We (1) accurately estimated the FUV flux at a large sample of
stars in Orion by statistically accounting for the uncertainty in parallax measurements, and (2) investigated the relation between
stellar accretion and external FUV flux by comparing observations and disc
evolution models. We selected a large
stellar population in Orion, assigned sub-cluster memberships and used 2D dimensional sub-cluster geometry to infer 3D separations from OBA
stars and compute the FUV flux at
stellar positions. We studied the
accretion luminosities Lacc inferred from Ha emission in
Gaia XP spectra of Orion sources and determined their detection fraction as a function of age and FUV flux. We compared the results with population synthesis models of viscous discs experiencing external photoevaporation. We provided a publicly available table of FUV fluxes at ~8600
stars in Orion. Most of the
stellar population is weakly irradiated <10^{2} G0, ~35% is intermediately irradiated 10^{2}-10^{4} G0, and ~5% has FUV fluxes >10^{4} G0.
Gaia-based Lacc decreases with age, and Ha detection fraction declines more rapidly in regions with strong FUV fluxes than in regions exposed to weaker FUV fluxes, broadly consistent with the model. This may suggest that external photoevaporation efficiently depletes strongly FUV-irradiated
accretion discs, but it is not sufficient to reliably confirm this conclusion. The provided tools for computing FUV fluxes at Orion
stars will be essential for future observations aimed at assessing the role of external photoevaporation on discs. We encourage measurements of
stellar and disc properties in Orion, covering FUV fluxes 1-10^5 G0.
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All authors Rossella Anania, Andrew J. Winter, Miguel Vioque, Giovanni P. Rosotti, Giacomo Beccari, Giuseppe Lodato, Lorenzo A. Malanga, Lara Piscarreta, Alice Somigliana, Leonardo Testi, Claudia Toci
Astrophysics of Galaxies
The Impact of Non-Gaussian Line Spread Functions on Stellar Kinematic Recovery: Consequences for Dynamical Models
David A. Simon
The line spread function (LSF) of a spectrograph encodes the inherent broadening of a single spectral line. It is typically reported as a single number, the resolving power $R = \lambda/\Delta\lambda$ with $\Delta \lambda$ the FWHM of the LSF. In standard pipelines for extracting
stellar kinematics the LSF is assumed to be a wavelength dependent Gaussian. However, detailed LSF measurements from real integral field spectrographs reveal a variety of shapes, some close to Gaussian, others with large wings or that appear boxy. I have studied the impact that these non-Gaussian LSF profiles have on the recovery of the
stellar kinematics of a mock spectrum based on MUSE ($\sigma_{\rm inst} = 51 $ km s$^{-1}$) and find that even in the high dispersion case of 300 km s$^{-1}$, there is up to a 7 percent bias in the dispersion due to non-Gaussian LSF profiles. Additionally, higher order Gauss-Hermite moments $h_3$ and $h_4$ can be biased by up to $\pm$0.1. To resolve this bias, I developed a method to match the LSF of the template spectra to the LSF of a target spectrum when the LSF of either one or both is non-Gaussian and show that it can reduce bias in the dispersion to less than a percent down to the instrumental resolution. A Python implementation of this method has been made publicly available.
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Cosmology and Nongalactic Astrophysics · Cross-listed from hep-th
Gravitational Duals from Equations of State II: Large Hierarchies and False Vacua
Raul Jimenez, David Mateos, Pavlos Protopapas et al. (+3 more)
We investigate the reconstruction of
holographic duals for strongly coupled
quantum field theories in regimes characterized by large hierarchies and the presence of false
vacua. Within the gauge/
gravity duality, these features translate into non-trivial thermodynamic behaviour and exotic renormalization group flows, including skipping flows between non-adjacent fixed points. Building on previous work based on Physics-Informed Neural Networks (PINNs), we extend the
holographic inverse problem of reconstructing the bulk scalar potential from boundary thermodynamic data into this new regime. This setting presents a variety of conceptual and numerical challenges, such as near-degenerate states, large hierarchies of energy scales, and regions of the potential that are not directly probed by the input data. We develop a set of methodological advances that overcome these obstacles, thereby improving the established PINNs-based methodology and extending it to new physical regimes of interest that were previously out of reach. Applying the developed framework, we demonstrate accurate reconstruction of scalar potentials deep into the false
vacuum regime, achieving robust agreement with the physical features of the underlying thermodynamics despite significant numerical stiffness. Our results extend the bridge between holography and machine learning, and suggest that data-driven approaches can provide new insights into the structure of strongly coupled systems.
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All authors Raul Jimenez, David Mateos, Pavlos Protopapas, Pau Solé-Vilaró, Pedro Tarancón-Álvarez, Pablo Tejerina-Pérez
Solar and Stellar Astrophysics
Asymmetric nightside CO2 features, inefficient heat transport, and precise evolutionary constraints: Spectroscopic phase curves reveal the past and present of a white dwarf-brown dwarf binary
Daphne Broski-Laing, Yifan Zhou, Joshua D. Lothringer et al. (+10 more)
We present the first JWST phase curve of a white
dwarf-brown
dwarf binary, a NIRSpec PRISM observation of ZTFJ0038+2030. Short-period white
dwarf-brown
dwarf binaries provide unique laboratories to probe substellar atmospheres.
Tidal locking drives hot Jupiter-like atmospheric dynamics in the brown
dwarf. The system's formation history offers a window into planetary systems around post-main-sequence
stars. We obtain a full-orbit phase curve of ZTF0038, including a total eclipse of the white
dwarf, which enables us to separate the two components' emission throughout the entire orbit, and we model the brown
dwarf's phase-resolved emission spectra using substellar atmosphere forward models and atmospheric
retrievals. The PRISM spectrum covers ~80% of the brown
dwarf's bolometric emission, enabling a nearly model-independent energy balance calculation, which yields a day-to-nightside heat transport efficiency of <10%. Inefficient heat redistribution is further supported by the phase curve shape and the nightside spectrum closely resembling non-irradiated mid-to-late T
dwarfs. The spectroscopic phase curves reveal a stark nightside asymmetry associated with a strong CO2 absorption feature at 4.2 um, while the retrieved abundances indicate a longitudinally homogeneous distribution of CO2 as well as all other key species detected in the atmosphere. The precise internal luminosity measurement of the brown
dwarf informs both the age of the WD-BD system (7.5-8.8 Gyr) and indicates a low common-envelope ejection efficiency. These data illustrate the exquisite opportunity to probe the three-dimensional processes of substellar atmospheres, connect substellar and
exoplanet atmospheres, and probe the
evolution of post-main-sequence planetary systems using WD-BDs.
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All authors Daphne Broski-Laing, Yifan Zhou, Joshua D. Lothringer, Daniel Apai, Jenni R. French, Sarah L. Casewell, L. C. Mayorga, Lael Shin, Ben W. P. Lew, Xianyu Tan, Vivien Parmentier, Siyi Xu, Mark S. Marley
Cosmology and Nongalactic Astrophysics · Cross-listed from hep-ph
Dynamical criterion for biased domain-wall formation
Wen-Yuan Ai
In the presence of a bias term, the conventional condition for forming a domain-wall network is $p_{\rm fv}>p_c\simeq 0.31$, with $p_{\rm fv}/(1-p_{\rm fv})=\exp(-\Delta V(0)/V_b(0))$, where $p_{\rm fv}$ is the false-
vacuum fraction immediately after the phase transition, $\Delta V(0)$ is the zero-temperature energy splitting between the false and true
vacua and $V_b(0)$ is the zero-temperature barrier height measured from the true
vacuum. This criterion, however, cannot be generally valid, since it is insensitive to the dynamics of the phase transition. In this work, we derive a dynamical criterion for domain wall formation in the presence of a bias term. We evaluate $p_{\rm fv}$ at the freeze-out temperature of the false-
vacuum correlation volumes $T_{\rm fo}$, obtaining a substantially stricter criterion. The same dynamical picture also yields a necessary consistency condition for applying scaling-regime gravitational-wave estimates, $T_{\rm fo}>T_{\rm ann}$, where $T_{\rm ann}$ is the annihilation temperature inferred from the scaling-regime dynamics.
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Astrophysics of Galaxies
Projection Is All You Need: Interpreting Polarization Measurements in the Orion Clouds with Sub-Alfvénic MHD Simulations
Feiyu Quan, Yitao Xu, Keping Qiu et al. (+2 more)
Dust polarization observations are widely used to diagnose the relative importance of
magnetic fields and
turbulence in
star forming molecular clouds, often through summary statistics such as the mean polarization direction $\mu$ and dispersion $\sigma$. Recent multi-scale polarization observations of the Orion Integral-Shaped Filament (ISF) reveal substantial diversity in polarization morphology among its dense cores, raising questions about the underlying Alfvénic nature of the cloud. In this work, we develop a statistical framework to compare polarization-based summary statistics from observations with those derived from projected three dimensional MHD simulations, explicitly accounting for projection effects. Using globally sub-Alfvénic simulations that naturally produce slightly super-Alfvénic dense cores, we show that modest deviations of core-scale
magnetic fields from the parent cloud field, when combined with projection, can generate a wide range of plane-of-sky polarization dispersions. Applying hypothesis testing, we find that the observed $(\mu, \sigma)$ values in the Orion ISF are statistically consistent with sub-Alfvénic cloud models over a broad range of viewing angles. This broad degeneracy implies that $\mu$ and $\sigma$ alone cannot provide precise information about the three-dimensional
magnetic-field distribution, and hence the Alfvén Mach number, of an individual cloud. While the observations can provide evidence against certain projection geometries, we demonstrate that polarization statistics based solely on $(\mu, \sigma)$ are insufficient to provide evidence against sub-Alfvénic cloud models. Our results highlight the necessity of explicitly incorporating projection effects when interpreting polarization observations of molecular clouds.
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All authors Feiyu Quan, Yitao Xu, Keping Qiu, Xiaodan Fan, Hua-bai Li
Astrophysics of Galaxies
Lighting Up the CGM: Strong, Jet-Aligned $H\alpha$ Emission around Radio Galaxies
Namrata Roy, Sanchayeeta Borthakur, Timothy Heckman et al. (+1 more)
A primary question within
galaxy evolution is how active
galactic nuclei (AGN) feedback modifies the circumgalactic medium (CGM). We present a search for faint H$\alpha$ emission from the cool ionized CGM ($T\sim 10^4$ K) around
radio galaxies by stacking background-
quasar spectra from DESI sightlines. We take into account the projected distance and position angle of each
quasar sightline relative to the
radio jet axis, and test whether jet–CGM coupling is anisotropic. We detect a strong H$\alpha$ excess at $>5\sigma$ along the collimated
radio jet axis ($\theta<20^\circ$) with a mean integrated flux of $1.19\times10^{-17}\ {\rm erg\ cm^{-2}\ s^{-1}}$. In contrast, the azimuthally averaged stack over all 324 sightline angles yields no detection ($<2\sigma$), indicating that this excess emission is very localized along the
radio jet. We also find that the jet-aligned H$\alpha$ signal is radially structured, where the strongest emission occurs near the host
galaxy just outside the optical half-light radius, and rising again near the projected
radio-lobe region. The jet-aligned stacks reveal H$\alpha$ signal that is roughly 100 times brighter than normal
halos. In the same sightlines however, Mg II absorption shows no difference in incidence between jet-aligned and off-axis directions, with broadly similar equivalent widths, column densities, and line widths. This striking contrast shows that while Mg II traces the ambient, clumpy cool CGM reservoir, the H$\alpha$ emission directly captures localized, low-covering-fraction clouds whose density, pressure, or ionization level has been dramatically boosted by the propagating jet. These results deliver clear evidence of localized jet-CGM interaction in
radio-jetted AGNs.
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All authors Namrata Roy, Sanchayeeta Borthakur, Timothy Heckman, Tanmay Singh
Cosmology and Nongalactic Astrophysics
Compaction function in stochastic inflation: a FOREST of type I and II primordial black holes
Chiara Animali, Pierre Auclair, Baptiste Blachier et al. (+2 more)
We show how to compute the compaction function within
stochastic inflation, by solving the random field dynamics on
stochastic binary trees. In this framework, the compaction function is directly related to the ratio of the volumes emerging from the sibling and child branches of a given node. This construction also determines whether or not the areal radius of a perturbation increases monotonically with the radial coordinate, thereby distinguishing between type-I and type-II fluctuations. As an application, we investigate
primordial black hole (PBH) formation in a single-field toy model with a constant potential slope, using
stochastic-tree realizations generated with the public code FOREST. In the classical regime, where
quantum diffusion is subdominant, the PBH mass function is narrowly distributed and type-II fluctuations are strongly suppressed relative to type I. By contrast, in the
quantum and near-critical (i.e. close to eternal inflation) regimes, the PBH mass distribution spans several orders of magnitude, the overall PBH abundance is enhanced, and type-II fluctuations outnumber type I. In that case cloud-in-cloud effects are also important, highlighting the need for a better understanding of the
evolution and collapse of type-II fluctuations in order to obtain robust PBH predictions when
stochastic effects are significant.
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All authors Chiara Animali, Pierre Auclair, Baptiste Blachier, Eemeli Tomberg, Vincent Vennin
Astrophysics of Galaxies
Strong Stellar Diffusion from Wave DM Cosmological Simulation and Potential Unified Origin for dSphs, UFGs, and UDGs
A. Pozo, T. Broadhurst, J. Zhang et al. (+6 more)
Our $\psi$DM simulations predict that
stars diffuse throughout dark matter
halos over the Hubble time through a random walk driven by the wave perturbations intrinsic to $\psi$DM. The resulting
stellar distribution locally follows a Gaussian profile (Sersic index $n=0.5$), as expected from the central limit
theorem, expanding as $R_{1/2}(t)\simeq(\hbar/m_\psi)^{0.5}\sqrt{t}$, in good agreement with the core–
halo profiles of typical $\psi$DM
dwarf spheroidal
galaxies. The strength of this
diffusion depends on
halo mass and the corresponding
soliton, naturally producing progressively more diffuse
stellar systems in more massive
halos. The observed continuity from faint
dwarfs and compact
dwarf spheroidals to ultra-diffuse
galaxies can therefore be interpreted as an age sequence, with later-forming
dwarfs experiencing less
diffusion and thus remaining smaller and brighter.
Stellar scattering arises from the random walk of the
soliton, gradually transporting
stars from the dense central core into the outer
halo, creating the extended
stellar envelopes observed around Local Group
dwarfs. Rather than being unique to Ultra-Diffuse
Galaxies (UDGs), this wave-driven
stellar diffusion may provide a unified mechanism explaining
galaxy structure across a vast mass range, from ultra-faint
dwarfs to the most massive UDGs, without requiring distinct formation channels or "failed
galaxy" scenarios. The diffuse
stellar halos and globular cluster distributions recently revealed by Euclid may therefore represent direct observational signatures of the granular dynamics of wave dark matter.
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All authors A. Pozo, T. Broadhurst, J. Zhang, M. Oguri, K. Umetsu, R. Emami, L. Hernquist, P. Mocz, M. Vogelsberger
Cosmology and Nongalactic Astrophysics · Cross-listed from gr-qc
Physical nonviability of $f(\mathbb{Q})$ in the scalar-tensor representation
Jose Beltrán Jiménez, Alejandro Jiménez Cano and Tomi S. Koivisto
We show the known pathological character of $f(\mathbb{Q})$
gravity in its scalar-tensor representation.
Instrumentation and Methods for Astrophysics
ESOFinder: an LLM-powered tool to help users navigate ESO documentation
P. Sánchez-Sáez, C. Reinero, M. Vioque et al. (+6 more)
The large amount and diversity of documentation available for users of the European Southern Observatory (ESO), spanning the full observing lifecycle from proposal preparation and observation planning to data reduction and archival access, makes it increasingly challenging for the astronomical community to efficiently find relevant information. To address this, we have developed ESOFinder, an in-house chatbot powered by Large
Language Models (LLMs) and
Retrieval Augmented Generation (RAG). ESOFinder integrates public information from instrument manuals, phase 1/2/3 documentation, data reduction pipeline manuals, the ESO Knowledge Base, and key web resources (spanning more than 3500 links and over 100 manuals) to provide concise, context-aware, and reference-linked answers to user queries about proposal or observation preparation, data
retrieval, and data processing. Built on open-source LLMs, running on a local server, ESOFinder ensures data
privacy, transparency, and complete control over the knowledge base. Its multi-step architecture allows verification of retrieved documents and generated answers, reducing the risk of
hallucinations and improving the reliability of responses compared to commercial tools. The current version of ESOFinder is being tested internally at ESO to evaluate its performance, assess its integration with internal workflows, and identify limitations in coverage and accuracy. These tests will guide further improvements, including the incorporation of additional documentation, and enhanced
retrieval strategies. Ultimately, ESOFinder aims to become an interface for users to navigate ESO's complex documentation ecosystem and to support both staff and community astronomers in their daily tasks.
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All authors P. Sánchez-Sáez, C. Reinero, M. Vioque, M. Wittkowski, M. Rejkuba, M. Romaniello, A. Barnes, J. Pritchard, M. Marsset
Astrophysics of Galaxies
Probing Magnetic Fields In and Around Galaxies Near and Far
S. A. Mao, Rainer Beck, Aritra Basu et al. (+14 more)
In order to understand the magnetization of
galaxies and the role of
magnetic fields in feedback processes that govern
star formation and
galaxy evolution, it is essential to have a comprehensive census of
magnetic fields in and around
galaxies from the nearby Universe to high
redshifts. In this chapter, we outline the science goals, strategies, techniques, and observational requirements with SKA AA4 for (1) a homogeneous polarimetric survey of nearby
galaxies - mapping both the diffuse polarized emission as well as producing a dense RM grid within the virial radius; (2) a survey of the interstellar
magnetic fields in distant
galaxies targeting strong
lensing systems with polarized lensed
quasars, as well as a general statistical back-illumination survey to probe the
redshift evolution of
magnetic fields in the CGM. These proposed observations will serve as a major step towards understanding the co-
evolution of
galaxies and their
magnetic fields over
cosmic time and provide constraints on
galactic dynamo theories.
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All authors S. A. Mao, Rainer Beck, Aritra Basu, Lerato Baidoo, Andrea Bracco, Ralf-Jürgen Dettmar, Volker Heesen, Cathy Horellou, Timea O. Kovacs, Kohei Kurahara, Yu-Qing Lou, Yik Ki Ma, Rikuto Omae, Rosita Paladino, Amit Seta, Fatemeh Tabatabaei, Theresa Wiegert
Earth and Planetary Astrophysics
ASTEP confirmation of a pair of long-period Jupiter-sized planets with extremely low densities transiting TOI-791
Georgina Dransfield, Antoine C. Petit, Amaury H.M.J. Triaud et al. (+45 more)
Gas
giant planets with periods $20~<~P~<~300~\rm days$ orbiting Sun-like
stars are a relatively uncommon outcome of planetary formation, and key questions about the nature and formation of this sub-population remain unanswered. Theoretical models for the location of their formation (in- or ex-situ) and for their subsequent migration predict different outcomes in terms of
planet masses and eccentricities, indicating that observations have a key role to play in disentangling their histories. In this work we present the discovery and confirmation of a pair of long-period Jupiter-sized
planets transiting an F7
star: TOI-791 b is a $0.993\pm0.033\rm~R_{Jup}$
planet on a $139.29931_{-0.00012}^{+0.00011}~\rm day$ orbit, and TOI-791 c, a $1.155\pm0.040\rm ~R_{Jup}$
planet on a $232.01570_{-0.00071}^{+0.00067}~\rm day$ orbit. The two
planets are within 0.07% of a second-order 5:3 period commensurability leading to transit timing variations (TTVs) of up to 50 minutes. We confirm their planetary nature using ground-based photometry, including multiple full detections of the $>11~\rm hr$ transits of both TOI-791 b and c from Antarctica with ASTEP, making these the longest-duration transits ever observed in their entirety from the ground. Our detailed analysis of the TTV signal allows us to measure dynamical masses for both
planets, which yield densities of $\rho_{\rm b}=0.038\pm0.008 \rm ~g~cm^{-3}$ and $\rho_{\rm c}=0.047\pm0.006 \rm ~g~cm^{-3}$, indicating that TOI-791~b and c are two of the lowest density
giant planets ever detected. While these measurements are robust, further follow-up is needed to fully characterise the TTV signal and the architecture of the system.
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All authors Georgina Dransfield, Antoine C. Petit, Amaury H.M.J. Triaud, Tristan Guillot, François-Xavier Schmider, Lyu Abe, Abdelkrim Agabi, Khalid Barkaoui, Thomas A. Baycroft, Philippe Bendjoya, Rafael Brahm, Karen A. Collins, Billy Edwards, Phil Evans, Alix V. Freckelton, Nolan Grieves, Steve B. Howell, Franco Mallia, Djamel Mekarnia, Angelica Psaridi, Daniel Sebastian, Keivan G. Stassun, Chris Stockdale, Amalie Stokholm, Olga Suarez, Thiam-Guan Tan, Mathilde Timmermans, Cristilyn N. Watkins, Carl Ziegler, Abderahmane Soubkiou, François Bouchy, Marion Cointepas, Vincent Deloupy, Maximilian N. Günther, Michaël Gillon, Giovanni Isopi, Emmanuel Jehin, Jon M. Jenkins, Andrés Jordán, Martin B. Nielsen, Sara Seager, Avi Shporer, Julia V. Seidel, Michal Steiner, Trifon Trifonov, Joseph D. Twicken, Joshua N. Winn, Aldo Zapparata
Solar and Stellar Astrophysics
Multi-height Identification of Sausage and Fluting Eigenmodes in a Solar Pore
Shahin Jafarzadeh, David B. Jess, Marco Stangalini et al. (+34 more)
Magnetic pores are compact, strongly magnetised waveguides in the lower
solar atmosphere and therefore provide favourable conditions for identifying magnetohydrodynamic (MHD) wave modes. Earlier seeing-free observations revealed concurrent sausage, kink, and fluting modes in photospheric pores, but only at a single sampled layer. In this Letter, we exploit the dense spectral sampling of the near-ultraviolet 327-329 nm window observed by the Sunrise-III UV Spectropolarimeter and Imager (SUSI) to investigate how pore wave modes behave across multiple photospheric and low-chromospheric heights spanning roughly 500 km. We analyse ~75 min of a Sunrise-III/SUSI time series containing a small
solar pore. From eight selected spectral lines sampling different estimated formation heights, we identify the pore boundary at each line and time step and apply proper orthogonal decomposition (POD) to the boundary oscillations. In all eight lines, the first POD mode is consistently identified as an axisymmetric sausage mode, with dominant power at ~1-2 mHz, and carries the dominant normalised
eigenvalue fraction, typically about 66-86%, while the second mode is a fluting mode with azimuthal wave number m = 2, dominant at ~2-3.5 mHz, and contributes about 4-10%. Cross-line wavelet phase analysis of the temporal coefficients shows that the sausage mode remains close to zero phase difference across the sampled heights, consistent with standing or near-standing behaviour, whereas the fluting mode displays a modest but systematic increase in phase with height, reaching about 50 degrees, indicative of an upward-propagating component. These observations provide the first multi-height identification and phase characterisation of sausage and fluting modes inferred from pore-boundary oscillations.
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All authors Shahin Jafarzadeh, David B. Jess, Marco Stangalini, Luiz A. C. A. Schiavo, Timothy J. Duckenfield, Suzana S. A. Silva, Gary Verth, Viktor Fedun, Sami K. Solanki, H. N. Smitha, Andreas Lagg, Achim Gandorfer, Alex Feller, Francisco A. Iglesias, Tino L. Riethmüller, Bianca Grauf, Johannes Hoelken, Yukio Katsukawa, Pietro Bernasconi, Thomas Berkefeld, Alberto Álvarez-Herrero, Masahito Kubo, David Orozco Suárez, Michael Carpenter, Alexander Bell, Valentín Martínez Pillet, Francisco Javier Bailén, Julian Blanco Rodríguez, Juan Sebastián Castellanos Durán, Edvarda Harnes, Ryohtaroh T. Ishikawa, Yusuke Kawabata, Takuma Matsumoto, Takayoshi Oba, Azaymi L. Siu-Tapia, Hanna Strecker, Dušan Vukadinović
Astrophysics of Galaxies
Kinematics of the Weak Cool-Core Cluster A3571 Observed with XRISM: Low Cooling Rate Balanced by Low Heating Rate?
Hannah McCall, Irina Zhuravleva, Kyoko Matsushita et al. (+10 more)
Most XRISM
galaxy cluster observations to date have focused on AGN feedback or actively merging systems. The weak cool-core cluster A3571 was observed in four XRISM Cycle 1 pointings, enabling the study of gas kinematics in a relaxed, AGN-feedback-free system. We present measurements of the velocity dispersion and bulk velocity in the core regions of A3571, out to $120$ kpc. The velocity dispersion is relatively uniform across all regions ($\sim100-120 ~\mathrm{km~s^{-1}}$), except in the northern gas sloshing elongation, where a $68\%$ upper limit of $68~\mathrm{km~s^{-1}}$ is obtained. The core Mach number and non-thermal pressure fraction of A3571 are lower than in the extremely relaxed cluster A2029 and below predictions from cosmological simulation suites. Despite relatively low velocity dispersion values, the derived turbulent heating rate (under the assumption of isotropic Kolmogorov
turbulence) is sufficient to offset cooling losses within the considerable uncertainties in all studied regions. This suggests that sloshing motions may contribute significantly to the heating budget. Comparing XRISM observations of merging and relaxed clusters, we find that mergers exhibit an average Mach number of $0.29\pm0.07$, nearly twice that of the relaxed sample, which is consistent with predictions from non-radiative cosmological simulations. A3571 is a promising target for resonant scattering studies; however, simulations indicate that deeper observations are required to obtain reliable turbulent velocities via the $z/w$ line ratio.
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All authors Hannah McCall, Irina Zhuravleva, Kyoko Matsushita, Annie Heinrich, Congyao Zhang, Eugene Churazov, William Forman, Ildar Khabibullin, Kotaro Fukushima, Daniele Rogantini, Itsuki Aihara, Christine Jones, Kazunori Suda
Solar and Stellar Astrophysics
Non-thermal Sources from Stereoscopic Hard X-ray and Earth-based Microwave Observations in a Data-Constrained Magnetohydrodynamic Simulation
Keitarou Matsumoto, Satoshi Inoue, Meiqi Wang et al. (+5 more)
We analyze the X7.1
flare on 2024 October 1 from NOAA AR 13842 using hard X-ray (HXR) imaging, microwave observations by the Expanded Owens Valley
Solar Array (EOVSA), and a three-dimensional Magnetohydrodynamic (MHD) simulation. The
flare was observed from two vantage points, with
Solar Orbiter/Spectrometer
Telescope for Imaging X-rays viewing the
flare near the limb and Advanced Space-based
Solar Observatory/Hard X-ray Imager and EOVSA observing it on the disk. We carried out a data-constrained MHD simulation using a nonlinear force-free field extrapolation as the initial condition and constrained the height of the non-thermal looptop source from stereoscopic HXR and microwave observations. The height is consistent between the stereoscopic analysis and the MHD simulation. A secondary non-thermal microwave source aligned with a southward
plasma ejection corresponds to an elongated current sheet. Although the current sheet grows in multiple directions, the secondary microwave emission is observed only from the southern segment. This localization suggests reconnection in regions with different
magnetic field strengths. Reconnection in strong-field regions produces
flare arcades with dominant looptop emission, whereas reconnection in weaker southern regions gives rise to secondary microwave emission at higher altitudes. The height of the secondary source is consistent between the stereoscopic analysis and the MHD simulation. Microwave spectral fitting suggests a higher low-energy cutoff for non-thermal electrons in the secondary microwave source than in the main looptop source. This may reflect the transport of electrons pre-accelerated near the looptop source by the southward
plasma ejection.
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All authors Keitarou Matsumoto, Satoshi Inoue, Meiqi Wang, Bin Chen, Muriel Zoë Stiefel, Säm Krucker, Satoshi Masuda, Haimin Wang
Solar and Stellar Astrophysics
MSFA-Net: An Advanced Deep Learning Model for Identifying Blue Horizontal-Branch Stars from LAMOST DR12
Mingyuan Wang, Xiaoming Kong, Jie Ju et al. (+2 more)
Blue horizontal-branch (BHB)
stars are low-mass, core helium-burning objects with nearly constant luminosities, making them powerful tracers of old, metal-poor populations and valuable standard candles for mapping the
Galactic halo. However, robustly identifying BHB
stars from low-resolution spectra remains challenging. We present MSFA-Net, a two-stage framework developed for the Large Sky Area Multi-Object Fiber Spectroscopic
Telescope (LAMOST) DR12. By combining multi-scale convolutions with a soft frequency
attention mechanism, MSFA-Net learns discriminative representations in both the wavelength domain and the
Fourier-frequency domain. On the test set, the framework achieves a precision of 94.67% in the initial multiclass screening and 98.07% in the subsequent binary refinement. Applying the pipeline to LAMOST DR12, we retrieve 27,853 BHB candidate spectra. After spectral deduplication and removal of previously known objects, we identify 3583 new BHB
stars, confirmed via Balmer-line profile fitting. We further estimate atmospheric parameters (Teff, log g, and [Fe/H]) using the machine-learning-based SLAM model and examine their distributions. A non-negligible subset shows unusually high log g and/or
metallicities, which we interpret primarily as inference-related systematics rather than intrinsic properties. Photometric cross-matching with
Gaia DR3 and color-magnitude diagrams provide an additional consistency check for the sample. The resulting catalog substantially enlarges the spectroscopically confirmed BHB sample from LAMOST and offers a homogeneous data set for studies of
Galactic-
halo structure and
stellar populations.
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All authors Mingyuan Wang, Xiaoming Kong, Jie Ju, Yude Bu, Yuchen Liang
Cosmology and Nongalactic Astrophysics
High-Redshift Signatures from the Cosmic Dawn and the Epoch of Reionization
Rennan Barkana, Oliver Basquette, Ankita Bera et al. (+22 more)
In this chapter, we provide a comprehensive overview of the astrophysical and cosmological processes that shape the 21-cm signal during
Cosmic Dawn and the Epoch of Reionization. We investigate both standard and exotic signatures potentially observable with SKA-Low. Standard signatures are those expected within the $\Lambda$CDM framework, including contributions from the first
stars,
galaxies, and black holes. Exotic signatures are more speculative indicating new physics, such as
primordial black holes, modifications to the dark matter sector, non-standard
primordial fluctuations, or strongly emitting
radio galaxies. The effects of these different sources or scenarios are evaluated in the context of the expected sensitivity of SKA-Low, considering the AA* and AA4 configurations. The chapter aims to provide an overview of the theoretical landscape of 21-cm signatures and to highlight how the forthcoming SKA-Low observations will improve our understanding of astrophysical processes at early times and may open the door towards new physics beyond the $\Lambda$CDM framework.
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All authors Rennan Barkana, Oliver Basquette, Ankita Bera, Jennifer Yik Ham Chan, Pravabati Chingangbam, Hector Afonso G. Cruz, Saswata Dasgupta, Kanan K. Datta, Anastasia Fialkov, Sambit K. Giri, Qin Han, Ilian T. Iliev, Bohua Li, Teppei Minoda, Shikhar Mittal, Julian B. Muñoz, Suvedha Suresh Naik, Janakee Raste, Aurel Schneider, Sudipta Sikder, Kinwah Wu, Yidong Xu, Bin Yue, Meng Zhang, Meng-Lin Zhao
Astrophysics of Galaxies
Pristine composition or size evolution: Can current dust models reproduce emissivities observed in nearby protostars?
M.-A. Carpine, A. Maury, N. Ysard et al. (+1 more)
Interstellar
dust is a crucial asset in many astronomical observations. Characterising grains present in the dense gas and in
star-forming environments is also key to constrain the pristine conditions for planetary formation. However,
dust properties remain poorly characterised and are still debated: low
dust emissivities observed in nearby protostars are not completely explained to this day. In this study, we aim to determine whether it is possible to retrieve the
dust properties from multi-wavelength observations of the
dust emission towards embedded protostars, and the extent to which current
dust models can reproduce the observed values of the
dust emissivity index in young protostars. We perform radiative transfer computations of the thermal
dust emission from a model protostellar envelope, considering different
dust optical properties commonly used in the community. This allows us to explore the effects of
dust composition on the spectral index, to try and explain the variation in the emissivity index in nearby protostars observations. We find large variations in the spectral index as the sole result of different
dust models, without the need for
dust grain size
evolution. However, our work does not allow us to reproduce the lowest emissivity index values found in some protostellar envelopes without including unexpectedly large millimetre-sized processed grains. We show that appropriate methods permits to measure the
dust emissivity from observations of the spectral index at millimetre wavelengths with very little uncertainty. Variation in emissivity index between the different observed sources and the
dust models most commonly used by the community implies that the intrinsic composition of
dust is not sufficient to explain the lowest spectral index values. Thus, early
dust evolution producing larger
dust grains may have to be taken into account to obtain a complete picture.
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All authors M.-A. Carpine, A. Maury, N. Ysard, L. Cacciapuoti