Cosmology and Nongalactic Astrophysics · Cross-listed from hep-ph
Z' portal dark matter from post-inflationary reheating: WIMPs, FIMPs, and UFOs
Stephen E. Henrich, Yann Mambrini and Keith A. Olive
We investigate the production of dark matter (DM) via a heavy $Z'$ mediator during the post-inflationary reheating epoch. In particular, we study production from three mechanisms which are smoothly connected to one another: WIMP-like freeze-out, FIMP-like freeze-in, and ultra-relativistic freeze-out (UFO). This is the first systematic study of $Z'$ portal DM which includes UFO. We find that much of the available parameter space for keV to TeV DM lies in the UFO regime for $ 1 \text{ TeV}\lesssim M_{Z'} \lesssim 1 \text{ PeV}$. When the mediator mass $M_{Z'}$ is greater than both the DM mass and the reheating temperature, UFO is a robust mechanism for producing cold DM. Although UFO DM is initially "hot" after freeze-out, it can easily become cold before structure formation if freeze-out occurs during post-inflationary reheating. Compared to standard freeze-in, UFO can accommodate significantly stronger interaction strengths (stronger couplings and/or smaller mediator masses).
Read the full abstract ▾
Instrumentation and Methods for Astrophysics
LEBS Toolkit for Addressing Development Challenges through Astronomy
Joyful E. Mdhluli
The LEBS Toolkit provides a comprehensive framework for astronomers and natural scientists to address development challenges through their field. The toolkit aligns with the Sustainable Development Goals (SDGs) and offers practical actions to achieve development outcomes. It emphasises the importance of effective communication between astronomy and development, highlighting four key components: Leadership, Externalities, Break Barriers to Entry and Support Functioning
Markets & Institutions (LEBS). Using these components, scientists can promote accurate information dissemination, encourage positive community impacts, overcome monopolistic barriers, and improve
market efficiency and institutional settings. The LEBS Toolkit serves as a guide for the scientific community in bridging the gap between scientific knowledge and practical development actions, ultimately contributing to global development goals.
Read the full abstract ▾
Cosmology and Nongalactic Astrophysics
Confronting cosmic shear astrophysical uncertainties: DES Year 3 revisited
Leah Bigwood, Jamie McCullough, Jared Siegel et al. (+19 more)
Cosmology from weak gravitational
lensing has been limited by astrophysical uncertainties in baryonic feedback and intrinsic
alignments. By calibrating these effects using external data, we recover non-linear information, achieving a 2% constraint on the clustering amplitude, $S_8$, resulting in a factor of two improvement on the $\Lambda$CDM constraints relative to the fiducial Dark Energy Survey Year 3 model. The posterior, $S_8=0.832^{+0.013}_{-0.017}$, shifts by $1.5\sigma$ to higher values, in closer agreement with the
cosmic microwave background result for the standard six-parameter $\Lambda$CDM cosmology. Our approach uses a
star-forming 'blue'
galaxy sample with intrinsic
alignment model parameters calibrated by direct spectroscopic measurements, together with a baryonic feedback model informed by observations of X-ray gas fractions and kinematic Sunyaev-Zel'dovich effect profiles that span a wide range in
halo mass and
redshift. Our results provide a blueprint for next-generation surveys: leveraging
galaxy properties to control intrinsic
alignments and external gas probes to calibrate feedback, unlocking a substantial improvement in the precision of weak
lensing surveys.
Read the full abstract ▾
All authors Leah Bigwood, Jamie McCullough, Jared Siegel, Alexandra Amon, George Efstathiou, David Sanchez-Cid, Elisa Legnani, Daniel Gruen, Jonathan Blazek, Cyrille Doux, Aurelio Carnero Rosell, Marco Gatti, Eric Huff, Niall MacCrann, Anna Porredon, Judit Prat Marti, Marcelle Soares dos Santos, Justin Myles, Simon Samuroff, Masaya Yamamoto, Boyan Yin, Joe Zuntz
Astrophysics of Galaxies
A Black-Hole Envelope Interpretation for Cosmological Demographics of Little Red Dots
Hiroya Umeda, Kohei Inayoshi, Yuichi Harikane et al. (+1 more)
Little red dots (LRDs) newly discovered with JWST are active
galactic nuclei (AGN) that may represent black hole (BH) growth at the earliest
cosmic epochs. These sources show puzzling features unlike typical AGNs, including red optical continua, weak hot-
dust emission, and a lack of detectable X-rays. Previously, LRDs have often been interpreted as
dust-reddened AGNs, leading to severe inconsistencies with the luminosity and BH mass densities inferred for previously known AGNs over $0<z<5$. The BH-envelope (BHE) model has been proposed to explain these characteristics, in which an accreting BH is enshrouded by a dense, optically thick gaseous envelope. In this Letter, we reanalyze the SEDs of $\sim 400$ photometric LRDs in the COSMOS-Web survey using the BHE model and reassess their implications for cosmological BH
evolution. We find that the optical-NIR spectra of LRDs are well reproduced by blackbody emission with an effective temperatures of $4000-6000~\K$. Within the BHE framework, the inferred bolometric luminosities decrease by $\gtrsim1-2$ orders of magnitude compared to
dust-reddened AGN assumptions. As a result, the revised luminosity function, BH
accretion density, and BH mass function become consistent with those of AGNs at $z<5$. The
stellar masses of LRD hosts are estimated by attributing the UV excesses to
star formation. Although the resulting $M_{\rm BH}/M_\star$ ratio remains higher than the local empirical value, the excess is modest. Overall, the BHE model not only resolves the spectral features of LRDs but also brings their statistical properties into agreement with the broader cosmological BH population.
Read the full abstract ▾
All authors Hiroya Umeda, Kohei Inayoshi, Yuichi Harikane, Kohta Murase
High Energy Astrophysical Phenomena · Cross-listed from nucl-th
Nucleon Short-Range Correlations and High-Momentum Dynamics: Implications on the Equation of State of Dense Matter
Bao-Jun Cai, Bao-An Li and Yu-Gang Ma
Nucleon short-range correlations (SRCs) and their high-momentum tails (HMTs) encode key short-range dynamics in
nuclei and dense matter. This review provides a concise overview of SRC features relevant to the Equation of State (EOS) of isospin-asymmetric
nuclear matter. We summarize empirical and theoretical properties of the single-nucleon momentum distribution $n(k)$, emphasizing the role of the
neutron–
proton tensor force, the dominance of correlated np pairs, and the enhancement of minority-species HMTs. Links to nucleon effective E-masses, quasi-deuteron components, and orbital
entanglement are briefly noted. We examine how SRC-induced HMTs modify kinetic and potential contributions to the EOS in both non-relativistic and relativistic frameworks, including the softening of the kinetic
symmetry energy and departures from the isospin
parabolic approximation of asymmetric
nuclear EOS. Sensitivity to high-momentum components and generalizations to arbitrary dimensions are also highlighted. Implications for heavy-ion reactions are summarized, including effects on particle yields, collective flows, deeply sub-threshold particle production and hard
photon emission, driven by modified initial nucleon momentum distributions and abundant high relative-momentum np pairs during the reaction. Finally, we outline SRC-HMT consequences for
neutron-
star matter, covering
proton fractions,
tidal deformabilities, $Z$-factors, cooling, and the core–crust transition, as well as possible connections to dark-matter interactions in dense environments.
Read the full abstract ▾
Instrumentation and Methods for Astrophysics
Machine Phenomenology: A Simple Equation Classifying Fast Radio Bursts
Yang Liu, Yuhao Lu, Rahim Moradi et al. (+4 more)
This work shows how human physical
reasoning can guide machine-driven symbolic regression toward discovering empirical laws from observations. As an example, we derive a simple equation that classifies fast
radio bursts (FRBs) into two distinct Gaussian distributions, indicating the existence of two physical classes. This human-AI workflow integrates feature selection, dimensional analysis, and symbolic regression: deep learning first analyzes CHIME Catalog 1 and identifies six independent parameters that collectively provide a complete description of FRBs; guided by Buckingham-$\pi$ analysis and correlation analysis, humans then construct dimensionless groups; finally, symbolic regression performed by the machine discovers the governing equation. When applied to the newer CHIME Catalog, the equation produces consistent results, demonstrating that it captures the underlying physics. This framework is applicable to a broad range of scientific domains.
Read the full abstract ▾
All authors Yang Liu, Yuhao Lu, Rahim Moradi, Bo Yang, Bing Zhang, Wenbin Lin, Yu Wang
Cosmology and Nongalactic Astrophysics
The impact of strong feedback on galaxy group scaling relations
D. Eckert, R. Seppi, J. Braspenning et al. (+16 more)
Feedback from active supermassive black holes alters the distribution of matter in the Universe by injecting energy in the neighbouring hot gaseous medium, which leads to ejection of gas from the
halos of
galaxy groups and massive
galaxies. Recent cosmological simulations such as FLAMINGO calibrate their feedback model on the
baryon fractions of
galaxy groups to tune the efficiency of gas ejection. However, recent observational constraints from optically selected groups and the kinetic Sunyaev-Zel'dovich effect yield lower
baryon fractions than previous studies, which indicates that feedback may be more ejective than previously thought. Here we show that models involving highly ejective feedback are inconsistent with the scaling relations of local
galaxy groups in the mass range $10^{13}-10^{14}M_\odot$. We study the X-ray luminosity-temperature relation in a sample of 44
galaxy groups with high-quality XMM-Newton observations. We show that highly ejective models under-predict the luminosity of
galaxy groups at fixed mass at high significance ($5.7\sigma$). This conclusion is robust against selection effects and is obtained from directly measurable and minimally correlated quantities. We point out that turning observable quantities into gas fraction estimates is challenging, especially in the context of stacking large samples of heterogeneous systems. We argue that calibrating feedback models on
baryon fractions is prone to systematic uncertainties and that observable scaling relations are better suited for this task.
Read the full abstract ▾
All authors D. Eckert, R. Seppi, J. Braspenning, A. Finoguenov, F. Gastaldello, L. Lovisari, E. O'Sullivan, S. Ettori, B. D. Oppenheimer, M. A. Bourne, D.-W. Kim, M. Sun, H. Khalil, G. Gozaliasl, Y. E. Bahar, V. Ghirardini, W. Cui, K. Kolokythas, S. McGee
Astrophysics of Galaxies
Warped & Hooked: Mapping the Magellanic Clouds in 3D using Red Clump stars
Slater J. Oden, David L. Nidever, Joshua Povick et al. (+18 more)
The Large and Small Magellanic Clouds (LMC and SMC) are the Milky Way's nearest interacting
galaxy pair, offering a unique laboratory for studying
tidal effects on
galactic disks. Despite extensive survey efforts, the three-dimensional geometry of the Clouds, particularly the putative warp of the LMC, remains poorly constrained due to incompleteness in their crowded centers and the low
stellar density of their peripheries, which demand wide-field coverage. Using red-clump (RC)
stars as standard candles, corrected for age- and
metallicity-dependent population effects with empirically calibrated color-magnitude relations and spatially resolved
star-formation histories, we construct the most detailed distance map of the Magellanic System to date. Based on $\sim$2.3 million RC
stars from
Gaia DR3 combined with modern reddening maps, we measure median heliocentric distances of $50.62 \pm 2.32$~kpc for the LMC (to $\sim$23$^{\circ}$) and $60.75 \pm 2.85$~kpc for the SMC (to $\sim$12$^{\circ}$). The maps reveal substructures including the LMC Northern Arm, southern hooks, the Magellanic Bridge, and SMC peripheral over-densities, with refreshed distance estimates. Fitting the LMC disk within $7^{\circ}$ yields a global inclination of $i = 25.32^{\circ} \pm 0.10^{\circ}$ and line-of-nodes position angle of $\theta = 142.34^{\circ} \pm 0.21^{\circ}$. Most strikingly, we find the LMC periphery is warped azimuthally into a U-shaped structure reaching vertical amplitudes of $\sim$7~kpc at radii of $\sim$15~kpc. We interpret this warp as a
tidal response to the most recent close passage of the SMC $\sim$300 Myr ago, providing new constraints on the orbital history and dynamical
evolution of the Magellanic Clouds.
Read the full abstract ▾
All authors Slater J. Oden, David L. Nidever, Joshua Povick, Pol Massana, Yumi Choi, Roeland P. van der Marel, Maria-Rosa L. Cioni, Joanna Sakowska, Knut A. G. Olsen, Lara Cullinane, J. A. Carballo-Bello, D. Crnojević, P. S. Ferguson, C. E. Martínez-Vázquez, G. E. Medina, B. Mutlu-Pakdil, M. Navabi, A. B. Pace, A. H. Riley, Guy S. Stringfellow, A. K. Vivas
Cosmology and Nongalactic Astrophysics
Primordial Black Holes from Inflation with a Spectator Field
Dario L. Lorenzoni, Sarah R. Geller, David I. Kaiser et al. (+1 more)
How is the production of
primordial black holes (PBHs) in single-field models of inflation impacted by the presence of additional scalar fields? We consider the effect of a spectator field - a free scalar field with sub-Hubble mass and no direct coupling to the inflaton and which makes a subdominant contribution to the total energy density - in the context of single-field models of inflation featuring a transient phase of ultra-slow-roll
evolution. Despite the modest title, a spectator field can have a dramatic impact: the slow-roll
evolution of the spectator prevents the combined inflaton-and-spectator system from entering into ultra-slow-roll, which naively might be expected to preclude the production of PBHs. However, we demonstrate that the growth of perturbations is maintained or enhanced by the spectator, through the rich interplay of
curvature and isocurvature perturbations. We show in a model-independent way that the single-field phase of ultra-slow-roll is replaced by two turns in field space encompassing a phase of tachyonic instability for the isocurvature perturbations and a transfer of power from isocurvature to
curvature modes. Furthermore, we highlight a degeneracy between the fine-tuning of the feature in the inflaton potential and the parameters of the spectator, leading to an overall resilience of model predictions to parameter variations. This makes it easier for the underlying PBH model to accommodate both high-precision
cosmic microwave background constraints and production of PBHs in the asteroid-mass range.
Read the full abstract ▾
All authors Dario L. Lorenzoni, Sarah R. Geller, David I. Kaiser, Evan McDonough
Astrophysics of Galaxies
Stellar Bars in Jellyfish Galaxies: Statistical Insights into the Combined Role of Bars and Environment
Osbaldo Sánchez-García, Bernardo Cervantes Sodi, Jacopo Fritz et al. (+3 more)
Recent observational studies suggest that the interplay between internal and environmental mechanisms, in particular, the combined action of
stellar bars and ram pressure stripping (RPS) may influence central
star formation activity in jellyfish
galaxies. However, current evidence relies on small samples, leaving open whether bars play a significant role during stripping. In this study, we analyse a sample about five times larger than those used in previous works, comprising 176
galaxies identified as RPS candidates based on optical morphological indicators such as asymmetries, debris tails, and displaced
star-forming regions. To assess the impact of these processes, we examine radial $u-r$ colour profiles from SDSS imaging as tracers of the specific
star formation rate (sSFR). We classify
galaxies by bar presence and RPS signatures, and construct comparison samples through stepwise matching in
stellar mass and environment to disentangle the individual and combined effects of bars and RPS on
stellar population gradients. Our results show that central rejuvenation signals emerge in RPS candidate
galaxies, becoming most evident when bars and RPS act together. Barred RPS
galaxies are systematically bluer at all radii than their non-RPS counterparts, while unbarred systems display only mild or no central differences, suggesting that the observable outcome of RPS depends on the stripping stage. Furthermore, barred
galaxies exhibit flatter central colour profiles than unbarred ones – a robust signature across all matched configurations. These findings highlight the key role of bars in amplifying environmental effects on the
stellar populations of jellyfish
galaxies, underscoring how internal structures can modulate the observable signatures of environmental processes in
galaxies.
Read the full abstract ▾
All authors Osbaldo Sánchez-García, Bernardo Cervantes Sodi, Jacopo Fritz, Karín Menéndez-Delmestre, Jacob P. Crossett, Yasmin Cavalcante-Coelho
Earth and Planetary Astrophysics
Fractal Aggregate Aerosols in the Virga Cloud Code II: Exploring the Effects of Key Cloud Parameters in Warm Neptune, Hot Jupiter and Brown Dwarf Atmospheres
Matt G. Lodge, Sarah E. Moran, Hannah R. Wakeford et al. (+2 more)
Aerosols and clouds are expected to be ubiquitous in
exoplanet and brown
dwarf atmospheres, where they can have a significant impact on transmission and emission spectra. The cloud code Virga is capable of quickly modeling cloud particle sizes as a function of altitude, and has recently been updated to include functionality for aggregates (ranging from very fluffy chains to compact fractals). We analyze the effect that these aggregates have on transmission spectra for typical warm Neptune and hot Jupiter environments, as well as their effect on emission spectra for an L-type brown
dwarf, over the wavelength range 0.3 - 15 um. We find significant, measurable differences in spectra when particle shape is changed (particularly the shortest wavelengths where particle morphology strongly affects the scattering slope). We provide some intuitive rules for how non-absorbing aggregates impact spectra: when particle sizes are small compared to the wavelength of light, the most elongated and chain-like particles have the highest opacities. When particles are large, the inverse is true (the most compact shapes have the highest opacities). We present an explanation for these effects in terms of the dynamics of how the particles form and move through the atmosphere, as well as in terms of fundamental optics theory. Given the significant impact that particle shape can have on spectra, we strongly encourage the community to include shape as a free parameter in future case studies, atmospheric models, and
retrievals.
Read the full abstract ▾
All authors Matt G. Lodge, Sarah E. Moran, Hannah R. Wakeford, Zoe M. Leinhardt, Mark S. Marley
Astrophysics of Galaxies
A bottleneck for star formation: the importance of magnetic fields during the formation of cold gas in galaxies
Ryan McGuiness, Rowan J. Smith and David Whitworth
Using a high-resolution simulation of a
dwarf galaxy, we quantify the energetic importance of
magnetic fields within the different phases of its interstellar medium (ISM) on parsec scales. We show that, whilst overall the
magnetic field is only energetically dominant for a small fraction of the ISM, it becomes important in the thermally unstable regime (45.2% of the mass is magnetically dominated), and in the majority of the cold neutral medium (66.1% of the mass). In the molecular gas, the
magnetic field dominates more of the total mass budget (39.8%) than thermal energy, turbulent kinetic energy, or gas self-gravitating potential energy. However, much of this gas will be CO-dark. This suggests that
magnetic forces are non-negligible during the formation of cold dense gas, which will slow its collapse and lead to an increase in the fraction of cold atomic, and molecular gas in the ISM. Consequently,
star-forming clouds may be surrounded by a larger reservoir of cold gas than would otherwise be expected.
Read the full abstract ▾
High Energy Astrophysical Phenomena
The dispersion in pulsar $\gamma$-ray efficiency
Daniel Íñiguez-Pascual, Daniele Viganò and Diego F. Torres
The observational efficiency of
pulsars, defined as the ratio of the observationally derived isotropic-equivalent luminosity, $4\pi d_{obs}^2 F_{obs}$, where $F_{obs}$ is the average pulsed energy flux of a
pulsar and $d_{obs}$ is its estimated distance, to its energy budget, shows a wide range of values. This dispersion is believed to be a combination of beaming effects, different geometries, and case-by-case variability of the emission mechanism efficiency, but it is not clear in what proportion. In this work we focused on the gamma-ray range and analysed the four main ingredients that likely contribute to this dispersion: the geometrical term arising from the anisotropic emission (beaming), viewing and inclination angles, the uncertainty on the
pulsar distance, the uncertainty on the moment of inertia, and the intrinsic efficiency of the mechanism producing the gamma-ray emission. Estimating the expected ranges of the moment of inertia and the distance errors, and considering a geometrical and spectral model that we have recently used to fit the light curves and spectra of the entire gamma-ray
pulsar population, we estimate the a priori distribution of the first three ingredients in order to obtain the a posteriori distribution of the intrinsic efficiency of the mechanism. We found the latter to peak at $\sim 5-15 \%$ and to have a dispersion of around one order of magnitude. That is, we found the intrinsic efficiency of the mechanism to be the leading factor in the observed dispersion. In addition, we found little sensitivity of these results on different distributions of the estimated
pulsar distance errors, and saw that the weak, alleged correlation with the
spin-down power can only explain part of the observed dispersion. This methodology can be easily applied to other geometrical models of the emission, to test the sensitivity of these results on the beaming distribution.
Read the full abstract ▾
Astrophysics of Galaxies
Eight New Ultramassive Black Hole Masses confirm Best Correlation with Galaxy Core Sizes
Stefano de Nicola, Jens Thomas, Roberto P. Saglia et al. (+3 more)
We analyse black-hole scaling relations at the high-mass end, focusing in particular on the regime of ultra-massive black holes, $\mathrm{M}_\mathrm{BH} > 10^{10}\,\mathrm{M}_\odot$ (UMBHs). In a sample of 16 Brightest Cluster
Galaxies (BCGs) without previous black-hole mass measurements we discover 8 UMBHs based on direct dynamical detections with triaxial Schwarzschild models. This first sample of triaxial black-hole mass determinations increases the number of known UMBHs by a factor of two and dramatically increases the constraints for BH mass scaling relations at the high-mass end. We find that BCGs are outliers in the canonical BH - $\sigma$ relation, while the size of their depleted cores - the central light-deficient region - is a much better unbiased predictor of the black hole mass and should be used as a proxy at the high-mass end. BCGs smoothly join the trend already established for massive core
galaxies in previous studies. This also holds for tight correlations between core size and sphere-of-influence radius and core size and core density. All these relations strongly support the black-hole binary model for the formation of the centers of the most massive
galaxies.
Read the full abstract ▾
All authors Stefano de Nicola, Jens Thomas, Roberto P. Saglia, Matthias Kluge, Jan Snigula, Ralf Bender
Cosmology and Nongalactic Astrophysics · Cross-listed from hep-th
Inflation with a Growing Fifth Dimension
Rashmish K. Mishra, Michael Nee and Lisa Randall
Inflation generally assumes a field with nonzero potential that leads to inflationary expansion happening at arbitrarily early times. We demonstrate potentially observable consequences of inflation with a finite initial time in a model in five-dimensional warped anti-de Sitter space, with both a UV and an IR brane present during inflation. Considering an inflaton with an approximately flat potential localized on the UV brane, we derive the resulting brane motion in the bulk and the 4D effective action describing the dynamics. A concrete model allows us to evaluate possible consequences of a starting point of inflation. The background
evolution is driven by the fast roll of the radion at early times and the slow roll of the inflaton at late times. We find that the action has the form of a two-field
hyperbolic inflation model, the two fields being the radion and the inflaton, both of which have a time-dependent background solution. This setup is holographically dual to an inflaton coupled to a strongly coupled confining sector in which the ratio of the confinement scale to the 4D Planck scale evolves cosmologically. Focusing on the period when the equation of state becomes that of inflation, we find that the presence of the IR brane leads to deviations from the approximate de Sitter background in addition to those from the slow-roll parameters of the inflaton potential. We quantify the effect of the presence of the IR brane on the two point function of the adiabatic scalar perturbations and tensor perturbations. The dominant deviations occur at large scales: the adiabatic power spectrum has a blue tilt, while the tensor power spectrum shows oscillatory features. We present numerical fits to the shape of the adiabatic power spectrum, and discuss the implications for
cosmic microwave background (CMB) analysis.
Read the full abstract ▾
Cosmology and Nongalactic Astrophysics · Cross-listed from hep-ph
Electroweak phase transition in SMEFT: Gravitational wave and collider complementarity
Sahabub Jahedi, Indrajit Saha and Abhik Sarkar
We study the first-order electroweak phase transition (FO-EWPT) within the Standard Model Effective Field Theory (SMEFT) framework induced by dimension-6 operators. Such phenomena can be probed independently via di-
Higgs production at the
collider experiments as well as via the detection of gravitational waves (GW). There are three (one) dimension-6 SMEFT operators that simultaneously modify the
Higgs potential at tree (1-loop) level and contribute to the di-
Higgs production at the
hadron colliders. With di-
Higgs production being suppressed at current LHC runs, we aim to probe this production at high luminosity (HL) and high energy (HE) runs of the LHC to achieve better sensitivity of dimension-6 SMEFT operators. The correlations among these operators are analyzed in the context of probing FO-EWPT, emphasizing the complementarity between future GW observations and upgraded LHC searches.
Read the full abstract ▾
Cosmology and Nongalactic Astrophysics · Cross-listed from gr-qc
Popcorn EMRIs: Transient Gravitational Wave Signals and Their Analysis in Schwartz Space
Pau Amaro Seoane and Kostas Tzanavaris
We investigate extreme-mass ratio inspirals (EMRIs) with orbital periods exceeding the observational timescale of mHz gravitational wave observatories. In their early, highly eccentric phases, these systems generate transient gravitational wave bursts during pericentre passages, separated by long quiescent intervals; we designate these signals “popcorn EMRIs.” We utilize a steady-state analytical model based on the continuity equation in phase space to estimate the population in a Milky Way-like
galaxy. The normalization of this model is linked to the solution of the Fokker-Planck equation describing
stellar relaxation. Adopting a conservative one-year observation baseline ($P>1$ year), we estimate the steady-state population of popcorn EMRIs. We forecast an observable burst rate of 5 to 44 events per year. The low duty cycle ($\sim 10^{-4}$) confirms their manifestation as isolated transients. Individual bursts from the
Galactic Centre exhibit high detectability. Analyzing these intrinsically transient signals demands a rigorous mathematical framework, as standard windowing techniques distort burst morphology. We establish an analytical foundation using standard smoothing techniques commonly used in real analysis. This yields the mathematically correct definition for the
Fourier transform of transient signals, justifying the use of the direct
Fourier transform without ad hoc windowing and ensuring the integrity of spectral analysis.
Read the full abstract ▾
Astrophysics of Galaxies
JWST Confirmation of a Runaway Supermassive Black Hole via its Supersonic Bow Shock
Pieter van Dokkum, Connor Jennings, Imad Pasha et al. (+6 more)
We present JWST/NIRSpec IFU observations of a candidate runaway supermassive black hole at the tip of a 62 kpc-long linear feature at z=0.96. The JWST data show a sharp kinematic discontinuity at the tip, with a radial velocity change of $\approx 600$ km/s across 0.1” (1 kpc). The velocity gradient, together with the projected post-shock flow velocity of $\approx 300$ km/s, is well described by a simple shock-compression model of a supersonic object, with a velocity of $v_{BH} = 954^{+110}_{-126}$ km/s and an inclination $i=29^{+6}_{-3}$ deg. The previously puzzling kinematics along the linear feature, with the observed radial velocity decreasing from $\approx 300$ km/s near the tip to $\approx 100$ km/s closer to the former host
galaxy, are naturally explained as gradual downstream mixing of shocked gas with the circumgalactic medium through turbulent entrainment. The bow shock interpretation is further supported by the morphology of the gas at the tip of the wake and an analysis of the [OIII]/H$\alpha$, [NII]/H$\alpha$, [SII]/H$\alpha$, and [SIII]/[SII] line ratios. The line ratios are consistent with fast radiative shocks and rapid cooling, with best-fit shock velocities that are in agreement with expectations from the black hole velocity and the shock geometry. Energy conservation over the lifetime of the wake suggests a SMBH mass of $M_{BH} \gtrsim 10^7$ M$_{\odot}$. These results confirm that the wake is powered by a supersonic runaway supermassive black hole, a long-predicted consequence of gravitational-wave
recoil or multi-body ejection from
galactic nuclei.
Read the full abstract ▾
All authors Pieter van Dokkum, Connor Jennings, Imad Pasha, Charlie Conroy, Ish Kaul, Roberto Abraham, Shany Danieli, Aaron J. Romanowsky, Grant Tremblay
Astrophysics of Galaxies
Galactic bars are already mature at Cosmic Noon: bar strength and flatness at z ~ 1.5
Boris S. Kalita, Luis C. Ho, John D. Silverman et al. (+6 more)
In this work, we explore the nature of $z>1$
galactic bars. Once thought to be highly transient, our results demonstrate otherwise. Our sample consists of nine massive ($>10^{10.5}\,\rm M_{\odot}$)
star-forming barred-spiral
galaxies at $z_{\rm spec} \sim 1.5$. Using rest-frame near-IR (F444W) JWST/NIRCam imaging, we apply ellipse fitting along with 1D and 2D morphological modeling to directly measure bar properties. We find that five
galaxies host flat surface brightness profiles (bar Sérsic index $<0.4$), indicative of highly evolved, "mature" bars. By contrast, only two
galaxies show exponential profiles, characteristic of young bars, and these are also shorter in absolute length than the flat bars. We therefore conclude that a large fraction of bars at this epoch have already matured, thereby indicating the presence of well-settled disks required to facilitate bar formation and sustained
evolution well before $z\sim1.5$. To assess the gravitational impact of the bars, we calculate the maximum transverse-to-radial force ratio ($Q_{b}$). We find that $Q_{b}$ values are comparable to, or weaker than, those of bars in the local Universe, Seven of the nine bars show only a marginal increase in strength with maturity (from exponential to flat bars). Contrarily however, the remaining two bars are flat, but have the lowest $Q_{b}$ values in our sample. We hence propose that the mature bars at $z\sim 1.5$ may experience phases of weakening due to rapid gas inflows and/or minor mergers. In conclusion, our work sheds light on the rapidly evolving nature of high-z bars and paves the way for larger statistical studies.
Read the full abstract ▾
All authors Boris S. Kalita, Luis C. Ho, John D. Silverman, Frédéric Bournaud, Miroslava Dessauges-Zavadsky, Emanuele Daddi, Annagrazia Puglisi, Xuheng Ding, Si-Yue Yu
Earth and Planetary Astrophysics
Tighter constraints on the atmosphere of GJ 436 b from combined high-resolution CARMENES and CRIRES$^+$ observations
A. Peláez-Torres, A. Sánchez-López, L. Nortmann et al. (+23 more)
We aim to study the atmospheric properties of the warm Neptune GJ 436 b by combining a set of five transit events observed with the CARMENES spectrograph with one transit from CRIRES$^+$ so as to provide the most constrained results possible at high resolution. We removed telluric and
stellar signals from the data using SysRem and potential planetary signals were investigated using the cross-correlation technique. Following standard procedures for undetected species, we performed injection recovery tests and
Bayesian retrievals to place constraints on the detectability of the main near-infrared absorbers. In addition, we simulated ELT/ANDES observations by computing end-to-end in silico
datasets with EXoPLORE. No molecular signals were detected in the atmosphere of GJ 436 b, which is consistent with previous studies. Combined CARMENES-CRIRES$^+$ injection-recovery and
Bayesian retrieval analyses show that the atmosphere is likely covered by high-altitude clouds ($\sim$ $1$ mbar) at low and intermediate
metallicities or, alternatively, is very metal-rich ($\gtrsim$ $900\times$
solar), which would suppress spectral features without invoking clouds. Simulations of ELT/ANDES observations suggest a boost by nearly an order of magnitude to the upper limit in the
photon-limited regime, reaching $0.1$ mbar at $10$-$300\times$
solar metallicities. The joint analysis of all useful transit observations from CARMENES and CRIRES$^+$ provides the most stringent constraints to date on the atmospheric properties of GJ 436 b. Complementary CCF-based and
retrieval approaches consistently indicate that the atmosphere is either cloudy or highly metal enriched. Any weak near-infrared absorption lines, if present, are likely to be below current detection limits. However, according to our simulations, these features may be revealed with ELT/ANDES even in single-transit observations.
Read the full abstract ▾
All authors A. Peláez-Torres, A. Sánchez-López, L. Nortmann, M. López-Puertas, E. González-Álvarez, H. M. Tabernero, C. Jiang, D. Revilla, G. Morello, J. Orell-Miquel, E. Pallé, P. J. Amado, J. A. Caballero, I. Ribas, A. Reiners, A. Quirrenbach, D. Cont, S. Dreizler, A. Fernández-Martín, A. P. Hatzes, Th. Henning, F. Lesjak, D. Montes, A. Schweizer, T. Trifonov, F. Yan
Cosmology and Nongalactic Astrophysics · Cross-listed from hep-ph
A new connection between WIMP dark matter and the hierarchy problem
Maximilian Detering, Thomas Steingasser and Tevong You
This work proposes a direct link between the hierarchy problem and Weakly Interacting Massive Particles (WIMPs): we suggest that the small mass of the
Higgs boson arises from being dynamically driven to the scale of the WIMP. Such a special electroweak
vacuum is singled out by lying close to the critical boundary of a phase transition, as recently explored in a new class of cosmological solutions to the hierarchy problem. They generically predict the
Higgs potential to be destabilised just above the weak scale. Intriguingly, the requirement for new physics to achieve this coincides with two independently well-motivated expectations: a split spectrum of light
fermions and heavy
bosons, as anticipated from naturalness, and the so-called "WIMP miracle". A WIMP with mass around the weak scale not only happens to have the correct thermal relic abundance to be the dark matter (DM), it can also give rise to the necessary critical boundary at the TeV scale through its Yukawa couplings to the
Higgs. We use a higgsino-like singlet-doublet model to illustrate our
Higgs-DM criticality scenario and show that if this WIMP DM mass is observed to be greater than ~1.2 TeV then it necessarily implies a strong bound on the
Higgs mass and an upper bound on the scale of heavy new physics that restores
vacuum stability. It can be thoroughly probed in direct detection experiments, astrophysical signals and future
collider searches, further motivating a comprehensive exploration of the remaining heavy WIMP parameter space.
Read the full abstract ▾
Astrophysics of Galaxies
The DREAMS Project: Disentangling the Impact of Halo-to-Halo Variance and Baryonic Feedback on Milky Way Dark Matter Speed Distributions
Ethan Lilie, Jonah C. Rose, Mariangela Lisanti et al. (+14 more)
Direct detection experiments require information about the local dark matter speed distribution to produce constraints on dark matter candidates, or infer their properties in the event of a discovery. In this paper, we analyze how the uncertainty in the dark matter speed distribution near the Sun is affected by baryonic feedback,
halo-to-
halo variance, and
halo mass. To do so, we harness the statistical power of the new DREAMS Cold Dark Matter simulation suite, which is comprised of 1024 zoom-in Milky Way-mass
halos with varied initial conditions as well as cosmological and astrophysical parameters. Applying a normalizing flows emulator to these simulations, we find that the uncertainty in the local DM speed distribution is dominated by
halo-to-
halo variance and, to a lesser extent, uncertainty in host
halo mass. Uncertainties in
supernova and black hole feedback (from the IllustrisTNG model in this case) are negligible in comparison. Using the DREAMS suite, we present a state-of-the-art prediction for the DM speed distribution in the Milky Way. Although the Standard
Halo Model is contained within the uncertainty of this prediction, individual
galaxies may have distributions that differ from it. Lastly, we apply our DREAMS results to the XENON1T experiment and demonstrate that the astrophysical uncertainties are comparable to the experimental ones, solidifying previous results in the literature obtained with a smaller sample of simulated Milky Way-mass
halos.
Read the full abstract ▾
All authors Ethan Lilie, Jonah C. Rose, Mariangela Lisanti, Alex M. Garcia, Paul Torrey, Kassidy E. Kollmann, Jiaxuan Li, Olivia Mostow, Bonny Y. Wang, Stephanie O'Neil, Xuejian Shen, Alyson M. Brooks, Arya Farahi, Nitya Kallivayalil, Lina Necib, Andrew B. Pace, Mark Vogelsberger
Cosmology and Nongalactic Astrophysics
Testing warm dark matter with kinematics of the smallest galaxies
M. Sten Delos, Niusha Ahvazi and Andrew Benson
Every dark matter
halo forms with a $\rho\propto r^{-1.5}$ density cusp at its center. For warm dark matter (WDM), these
prompt cusps can be massive enough to influence the kinematics of
dwarf galaxies. By implementing
prompt cusps in the Galacticus
galaxy formation model, we show that the measured velocity dispersions of Tucana V and Triangulum II are serious outliers for
dwarf galaxies arising in WDM models. For thermal-relic dark matter, the three faintest Milky Way satellites together constrain the particle mass to be $m_\chi>5.8$ keV at 95 percent confidence or $m_\chi>9.4$ keV at 90 percent confidence. Improved velocity dispersion measurements for these systems could greatly refine this constraint, as could identification and kinematic characterization of more such
galaxies.
Read the full abstract ▾
Earth and Planetary Astrophysics
Resolving the terrestrial planet-forming region of HD 172555 with ALMA: I. Post-impact dust distribution
Zoe Roumeliotis, Luca Matrà, Grant M. Kennedy et al. (+5 more)
Giant impacts between planetary embryos are a natural step in the terrestrial
planet formation process and are expected to create disks of warm debris in the terrestrial regions of their
stars. Understanding the gas and
dust debris produced in
giant impacts is vital for comprehending and constraining models of planetary collisions. We reveal the distribution of millimeter grains in the
giant impact debris disk of HD 172555 for the first time, using new ALMA 0.87 mm observations at $\sim$80 mas (2.3 au) resolution. We modeled the interferometric visibilities to obtain basic spatial properties of the disk, and compared it to the disk's
dust and gas distributions at other wavelengths. We detect the
star and
dust emission from an inclined disk out to $\sim$9 au and down to 2.3 au (on-sky) from the central
star, with no significant asymmetry in the
dust distribution. Radiative transfer modeling of the visibilities indicates the disk surface density distribution of millimeter grains most likely peaks around $\sim$5 au, while the width inferred remains model-dependent at the S/N of the data. We highlight an outward radial offset of the small grains traced by scattered light observations compared to the millimeter grains, which could be explained by the combined effect of gas drag and radiation pressure in the presence of large enough gas densities. Furthermore, SED modeling implies a size distribution slope for the millimeter grains consistent with the expectation of collisional
evolution and flatter than inferred for the micron-sized grains, implying a break in the grain size distribution and confirming an overabundance of small grains.
Read the full abstract ▾
All authors Zoe Roumeliotis, Luca Matrà, Grant M. Kennedy, Sebastian Marino, Kate Y.L. Su, David J. Wilner, Mark C. Wyatt, Alan P. Jackson
Solar and Stellar Astrophysics
The evolutionary history of ultra-compact accreting binaries. I. Chemical abundances and formation channel of the eclipsing AM CVn system ZTF J225237.05-051917.4 from HST spectroscopy
W. Yu, A. F. Pala, T. Kupfer et al. (+33 more)
AM Canum Venaticorum (AM CVn)
stars are ultra-compact binary systems composed of a white
dwarf (WD) primary accreting from a H-deficient donor. They are important as potential progenitors of Type Ia
supernovae and laboratories for gravitational-wave studies, yet their evolutionary history remains unsolved. Three formation channels have been proposed: the WD channel, the He-
star channel, and the cataclysmic variable (CV) channel. We aim to provide the first accurate measurements of the fundamental parameters of the accretor in ZTFJ225237.05-051917.4, including the abundances of key elements such as C, N, and Si, by analysing UV spectra obtained with the Hubble Space
Telescope. These measurements provide new insight into the system's evolutionary history and establish it as a
benchmark to develop our pipeline for application to a larger sample of AM CVns. We determine the binary parameters from photometric modelling and constrain the atmospheric parameters of the WD accretor, including Teff, logg, and chemical abundances, by fitting the UV spectrum with synthetic spectral models. We then infer the system's formation channel by comparing our results with theoretical evolutionary models. We measure a Teff=23300$\pm$600K and a surface
gravity of logg=8.4$\pm$0.3, which implies an accretor mass of 0.86$\pm$0.16
solar masses. We find a high N/C abundance ratio by mass of >153. The accretor is significantly hotter than previous estimates based on simplified blackbody fits to the spectral energy distribution, underscoring the importance of detailed spectral modelling for determining accurate system parameters. Our results show that UV spectroscopy is well-suited to constraining the formation channels of AM CVn systems. We conclude that the He-
star channel can be excluded based on the high N/C ratio, while the WD and CV channels remain consistent with the observations.
Read the full abstract ▾
All authors W. Yu, A. F. Pala, T. Kupfer, B. T. Gänsicke, D. Koester, D. Belloni, T. L. S. Wong, M. R. Schreiber, J. van Roestel, A. J. Brown, E. O. Waagen, J.-L. González-Carballo, S. Bednarz, K. Bernacki, D. De Martino, E. Fernández Mañanes, R. González Farfán, M. J. Green, P. J. Groot, F.-J. Hambsch, C. Knigge, J.-L. Martin-Velasco, M. Morales-Aimar, G. Myers, R. Naves Nogues, R. Poggiani, A. Popowicz, G. Ramsay, E. Reina-Lorenz, P. Rodríguez-Gil, J.-L. Salto-González, E. M. Sion, D. Steeghs, P. Szkody, O. Toloza, G. Tovmassian
Instrumentation and Methods for Astrophysics
Minuet: A Diffusion Autoencoder for Compact Semantic Compression of Multi-Band Galaxy Images
Alexander T. Gagliano, Yunyi Shen and V. A. Villar
The Vera C. Rubin Observatory is slated to observe nearly 20 billion
galaxies during its decade-long Legacy Survey of Space and Time. The rich imaging data it collects will be an invaluable resource for probing
galaxy evolution across
cosmic time, characterizing the host
galaxies of transient phenomena, and identifying novel populations of anomalous systems. While machine learning models have shown promise for extracting
galaxy features from multi-band astronomical imaging, the large dimensionality of the learned latent space presents a challenge for mechanistic interpretability studies. In this work, we present Minuet, a low-dimensional
diffusion autoencoder for multi-band
galaxy imaging. Minuet is trained to reconstruct 72x72-pixel $grz$ image cutouts of 6M
galaxies within $z<1$ from the Dark Energy Camera Legacy Survey using only five latent dimensions. By using a
diffusion model conditioned on the
transformer-based autoencoder's output for image reconstruction, we achieve semantically-meaningful latent representations of
galaxy images while still allowing for high-fidelity, probabilistic reconstructions. We train a series of binary classifiers on Minuet's latent features to quantify their connection to morphological labels from
Galaxy Zoo, and a conditional flow to produce posterior distributions of SED-derived
redshifts,
stellar masses, and
star-formation rates. We further show the value of Minuet for nearest neighbor searches in the learned latent space. Minuet provides strong evidence for the low intrinsic dimensionality of
galaxy imaging, and introduces a class of astrophysical models that produce highly compact representations for diverse science goals.
Read the full abstract ▾
Solar and Stellar Astrophysics
Pleiades Binary Fraction Revisited
Dmitry Chulkov
One of the nearest and best studied open clusters, Pleiades is an important cornerstone of
stellar astrophysics. Despite its role as reference coeval
stellar population, its multiplicity properties remain vaguely determined. The combined use of
Gaia DR3 multiband photometry, astrometric parameter RUWE, non-single
star solutions along with available ground-based spectroscopic, high angular resolution, and polarimetric observations enable more robust constraints on the binary
star population in the cluster. Several conclusions may have broader implications for other
stellar populations. Twin binaries, with mass ratio close to $q\sim 1$, tend to have lower RUWE, increasing their membership selection probability, relative to $q\sim 0.5$ systems that are disfavored. The frequently observed peak in mass ratio distribution for $q\sim 1$ binaries may be partially attributed to this bias. Photometrically fitted mass ratio is underestimated for double-lined spectroscopic binaries in agreement with other authors. Differential extinction photometrically mimics
stellar binarity. An area of enlarged absorption is traced by increased polarization south of the Merope
star and excluded from the analysis to avoid this bias. The fraction of systems with $q>0.6$ companions is measured to be $f=16.4\%^{+2.6}_{-0.6}$ for $m>0.5~M_\odot$
stars, which is larger than recent
Gaia-based estimates, but compatible with the pre-
Gaia values for Pleiades and the field population. Binary fraction shows no steady increase with
stellar mass in the 0.5 $-$ 1.2 $M_\odot$ range, while mass ratio has a bimodal distribution with a minimum near $q\sim 0.7$.
Read the full abstract ▾
Cosmology and Nongalactic Astrophysics
Controlled Tension Forecasting: Quantifying Cross-Probe Biases in $\omega_0\omega_a$CDM
Seokcheon Lee
Recent analyses combining DESI DR2 BAO, Planck CMB, and Pantheon+ SNe have reported mild deviations from the \LambdaCDM model. A central challenge is to determine whether these deviations reflect genuine dark-energy
evolution or instead arise from cross-probe inconsistencies, prior choices, or mismatches in likelihood construction. Previous work demonstrated that imposing a biased
supernova-motivated prior on \Omega_{m0} can artificially displace the BAO-inferred (w_0,w_a) values from the \LambdaCDM expectation. A complementary pedagogic study further showed that differing degeneracy geometries among BAO, CMB, and SNe can generate apparent dark-energy
evolution even when the underlying cosmology is exactly \LambdaCDM. Here we present a controlled tension-injection framework designed as a simplified mock-based diagnostic tool for studying how selected probe-level inconsistencies propagate into inferred dark-energy parameters. Self-consistent BAO, CMB, and SNe mock
datasets are augmented with parameterized shifts in (\Omega_{m0}, H_0),
supernova absolute calibration, and the BAO sound-horizon scale r_d. The resulting
datasets are analyzed through a unified MCMC pipeline, enabling a direct assessment of how these controlled tensions propagate into biases in (w_0,w_a) and the pivot equation-of-state parameter w_p. The results should be interpreted within the restricted setup adopted here: the late-time sector is described in the CPL parametrization and the CMB is represented through compressed distance priors. In this sense, the framework is intended primarily as an illustrative and diagnostic device for identifying probe combinations and degeneracy directions that are more vulnerable to tension-induced dynamical-dark-energy-like shifts, rather than as a parametrization-independent or fully realistic prediction tool.
Read the full abstract ▾
Solar and Stellar Astrophysics · Cross-listed from physics.hist-ph
Questions related to the Deflection of Light by Gravity determined by Soldner, Einstein and Schwarzschild
Klaus Wilhelm, Bhola N. Dwivedi and Karsten Muller
Before we discuss the deflection of light in a gravitational field, we give a brief overview of some basic physical formulas on
photon properties, generation and propagation. The much debated problems of the
redshift and the
photon propagation in a gravitational field is then considered and applied to the calculation of the speed of light. Many citations are given in direct quotations to avoid any misunderstandings. If the quotations are in German, an English translation is provided. Based on this speed, calculated and measured results are recalled on the deflection of light, with emphasis on the deflection near the Sun. We conclude that the speed of light and the deflection angle can be determined by energy and momentum conservation principles.
Read the full abstract ▾
High Energy Astrophysical Phenomena · Cross-listed from gr-qc
Screening of dipolar emission in two-scale Gauss-Bonnet gravity
Farid Thaalba, Leonardo Gualtieri, Thomas P. Sotiriou et al. (+1 more)
We study black holes in shift-symmetric scalar Gauss-Bonnet
gravity extended by a cubic Galileon interaction with a distinct energy scale. Introducing this hierarchy profoundly modifies the theory's phenomenology. The cubic interaction allows for smaller black holes, and can generate a screening mechanism near the horizon, making large Gauss-Bonnet couplings consistent with gravitational-wave bounds. Observable quantities such as the scalar charge, the innermost stable circular orbit, and its frequency are most affected for small black holes. The resulting multi-scale effective field theory remains technically natural and offers new avenues to probe
gravity in the strong-field regime.
Read the full abstract ▾
All authors Farid Thaalba, Leonardo Gualtieri, Thomas P. Sotiriou, Enrico Trincherini