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Physics Astrophysics Cosmology and Nongalactic Astrophysics

astro-ph.CO Watch Cosmology and Nongalactic Astrophysics

Thursday 27 August

Cosmology and Nongalactic Astrophysics · Cross-listed from astro-ph.GA

The Limited Lifetime of Self-Gravitating Accretion Disks In Galactic Centers

Isaac Shlosman

Globally self-gravitating accretion disks in active galactic nuclei (AGN) have been frequently discussed in the literature, but never observed. Few dozen mega-masering accretion disks in AGN have been detected, which display a clear Keplerian rotation on scales of 0.1-1 pc, allowing to estimate their masses within the sphere of influence (SoI) of the central supermassive black holes (SMBHs) to be smaller by more than a factor of 10, compared with the parent SMBH masses. Furthermore, the stellar components, deep inside the SoI, are dwarfed by the SMBH masses of M_BH ~ few X 10^6 - few X 10^7 Mo. Theoretically, no limit exists on sizes and masses of gaseous disks in AGN, which in principle, can exceed masses of their central compact objects. We analyze instabilities which can operate in gaseous disks, i.e., fragmentation for a locally dominant self-gravity and spontaneous breaking of axial symmetry for the globally self-gravitating disks. We invoke the gas response to the latter instability which leads to gravitational collapse, leaving a negligible mass behind and dynamically stable remnants. Consequently, the characteristic timescale for globally self-gravitating disks to exist in AGN should not exceed few rotations, t_phi ~ 10^{3-4} yrs for M_BH ~ 10^{6-8} Mo. Disk rebuilding is expected to be > 10^7 yrs, meaning that probability of finding is < 10^{-3}, which explains their lack of detection. We conclude that observed sub-parsec disks in AGN, at least the Keplerian masering ones, can be remnants of globally self-gravitating accretion disks, and the instability timescale can be related to the duty cycle of AGN, t_duty ~ 10t_phi ~ 10^{4-5} yr.
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Cosmology and Nongalactic Astrophysics · Cross-listed from astro-ph.GA

Measuring Extragalactic Microlens Masses and Motions in Strongly Lensed Quasar Systems with Intensity Interferometry

Abigail Moran and Ken Van Tilburg

The direct measurement of masses and transverse motions of individual stars and compact objects in distant galaxies remains an outstanding challenge, leaving extragalactic stellar populations constrained only through model-dependent population fits. We show that time-resolved intensity interferometry of strongly lensed quasars, combined with flux-ratio photometry, can break the source-size, microlens-mass, and transverse-velocity degeneracies of conventional light-curve microlensing. Using the quadruply lensed quasar B1422+231 as a fiducial system and a next-generation interferometer ($\sim$800\,m$^2$ collecting area, spectral resolving power of 20,000, and few-picosecond timing), we forecast the precision on the quasar source size and on the mass, position, and transverse motion of an individual stellar-mass microlens in the lens galaxy. A single epoch determines the accretion disk size to $4\%$ in favorable geometries ($10\%$ for a typical detectable configuration) and the microlens mass to order unity for $m_l \gtrsim 0.1\,M_\odot$. An eight-year, 33-epoch campaign reaches $\lesssim1\%$ on the disk size, localizes the microlens' impact parameter to $\sim0.1$-$0.5,\mu\mathrm{as}$, and resolves its proper motion. Such observations would enable direct measurements of individual extragalactic compact-object masses and transverse motions at moderate redshift. They also yield sub-$\mu\mathrm{as}\,\mathrm{yr}^{-2}$ sensitivity to light-centroid acceleration, which can help separate stellar microlensing from dark matter substructure lensing, the subject of a companion paper.
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Cosmology and Nongalactic Astrophysics

TDCOSMO. XXVII. JWST-based Lens Models and H$_0$ Measurement of WFI2033, HE0435, and PG1115

D. M. Williams, T. Treu, D. P. Johnson et al. (+13 more)

Time-delay cosmography offers a one-step, distance-ladder-independent route to the Hubble-Lemaitre constant, H_0. We present new cosmography-grade lens models of three quadruply imaged quasars based on JWST-NIRCam/F115W imaging (WFI2033-4723, HE0435-1223, PG1115+080). We use the STARRED modeling technique, introduced in our previous analysis of WFI2033-4723, to reconstruct the complex JWST-NIRCam Point Spread Function at high fidelity. We combine NIRCam-based lens models with improved external convergence estimates, published time delays, and aperture-integrated stellar velocity dispersions from JWST NIRSpec to infer H_0. The analysis was carried out blindly for HE0435-1223 and PG1115+080, while it was not blind for WFI2033-4723, as we build upon the previous published model. For comparison with previous HST-based work, we limit our analysis to the case of no internal mass-sheet degeneracy ($\lambda_{\rm int}=1$). We quantify the impact of improved imaging, single-aperture kinematics, and environment measurements on central values and uncertainties. Within flat $\Lambda$CDM, assuming a uniform prior on $\Omega_{\rm m}$, we find H_0 = 71.8$_{-7.0}^{+9.2}$ $\lambda_{\rm int}$ km s$^{-1}$ Mpc$^{-1}$ for PG1115+080, 74.2$_{-4.2}^{+4.2}$ $\lambda_{\rm int}$ km s$^{-1}$ Mpc$^{-1}$ for HE0435-1223, and 73.4$_{-4.4}^{+3.4}$ $\lambda_{\rm int}$ km s$^{-1}$ Mpc$^{-1}$ for WFI2033-4723. Combining the three lenses yields H_0 = 73.5$_{-2.8}^{+2.7}$ $\lambda_{\rm int}$ km s$^{-1}$ Mpc$^{-1}$, consistent with HST-based results (73.6$_{-2.6}^{+2.6}$ $\lambda_{\rm int}$ km s$^{-1}$ Mpc$^{-1}$), but with reduced scatter between the three systems. These models will be incorporated in the TDCOSMO-2026 milestone paper with free $\lambda_{\rm int}$ in a hierarchical fashion. We close by outlining how 16 forthcoming JWST NIRCam targets will further tighten uncertainties toward percent-level precision on H_0.
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All authors D. M. Williams, T. Treu, D. P. Johnson, P. Mozumdar, S. Knabel, S. Birrer, C. D. Fassnacht, A. Galan, A. J. Shajib, K. C. Wong, M. Cappellari, F. Courbin, T. Morishita, V. Motta, D. Sluse, M. Stiavelli

Cosmology and Nongalactic Astrophysics

Discovering Substellar Dark Matter Halos with Astrometric Weak Lensing of Multiply Imaged Quasars

Ken Van Tilburg and David E. Kaplan

We propose time-domain astrometric weak lensing of multiply imaged quasars as a probe of substellar dark matter (DM) halos. In $\Lambda$CDM, each macro-image's light traverses many microhalos, producing a stochastic centroid motion with a calculable red power spectrum. Halos with crossing times longer than the survey impart a relative angular acceleration between image pairs. The response peaks at subhalo scale radii 0.005-2 pc and masses $3\times10^{-6}$-$10^2\,M_\odot$, 12-14 orders of magnitude below the smallest detected DM structures, down to the damping cutoffs of a 100 GeV thermal relic. We forecast the sensitivity of ten-year campaigns with 300 epochs for two benchmark systems: the galaxy-lensed quadruple B1422+231 at a 0.1 $\mu$as per-epoch precision forecast for extended-path intensity correlation, and the cluster-lensed triple SDSS J1029+2623 at 1 $\mu$as. The angular-acceleration channel reaches the standard $\Lambda$CDM microhalo population with a variance signal-to-noise ratio of order ten for the galaxy lens (order unity after stellar microlensing subtraction) and 0.35 for the cluster under the optimistic assumption that 10% of the projected mass density at the image positions resides in surviving microhalos. A positive detection would: raise universal lower bounds on the DM particle mass to $\gtrsim400$ keV for fermions and $\gtrsim10^{-12}$ eV for bosons; constrain the DM kinetic decoupling temperature to $\gtrsim 10$ MeV; and be sensitive to the running of the spectral tilt at the 0.01 level over 15-20 e-folds of the primordial curvature power spectrum. A robust null result across well-characterized lenses would constrain microhalo survival and/or imply violations of the above inequalities. These signatures motivate differential astrometric observations with extreme 0.1-1 $\mu$as light-centroiding precision on multiply imaged quasars. [Abridged]
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Cosmology and Nongalactic Astrophysics · Cross-listed from physics.ins-det

A microwave SQUID multiplexing concept for macro-cryogenic calorimeter arrays

N. Ferreiro Iachellini, P. Szypryt, L. Canonica et al. (+10 more)

Massive cryogenic calorimeters read out by transition-edge sensors (TES) can reach eV-scale baseline resolution, but the single-channel dc-SQUID readout conventionally used in rare-event searches, with one amplifier chain and several wires per detector, limits practical arrays to a few tens of channels. We propose to apply microwave SQUID multiplexing ($\mu$MUX), developed for fast X-ray and neutrino-mass microcalorimeters, to massive BGO (Bi$_4$Ge$_3$O$_{12}$) calorimeters operated at $\simeq 20$~mK; sapphire and TeO$_2$ absorbers are covered by the same framework. Using the established thermal and noise model for massive TES calorimeters, we derive a noise model for the multiplexed readout, including the HEMT, two-level-system and SQUID contributions, and its scaling with the multiplexing factor $N_{\rm mux}$. Since the slow thermal signals require only about a kHz of sampling per channel, the limiting requirement is not bandwidth but an input-coil sensitivity of $( 0.1$ to $1)\,\mu$A$/\Phi_0$, a factor of $10$ to $30$ beyond current $\mu$MUX devices, matched to the detector current noise of ($9$ to $10$)~pA$/\sqrt{\rm Hz}$, which is independent of the absorber mass. With a total flux noise of $\simeq$$1.2\,\mu\Phi_0/\sqrt{\rm Hz}$, the readout degrades the baseline resolution by less than $2\%$ up to $N_{\rm mux}=1000$, negligible compared with the TES-limited resolution. These results are implemented in a single-tower design: 52 BGO crystals of 100~g each and one HEMT amplifier. The tower is the unit of a multi-tower array of several kilograms aimed at CE$\nu$NS and dark matter searches.
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All authors N. Ferreiro Iachellini, P. Szypryt, L. Canonica, W. B. Doriese, M. Durkin, A. Giachero, J. A. B. Mates, A. Nucciotti, L. Pattavina, S. Quitadamo, C. Shiu, J. N. Ullom, M. R. Vissers

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

Detecting Axion-Like Particles With Coiled Optical Fibers I: Silica Fibers

Gia Dvali, Sebastian Zell and Tongxuan Zhang

We propose a new approach to axion-like particle (ALP) searches based on long, coiled optical fibers in an external magnetic field. We develop the theoretical framework required to describe photon-ALP conversion in this geometry by incorporating transverse boundary conditions and fiber bending. For solid silica fibers with refractive index considerably larger than unity, we show that the leading signal is a phase shift of the photon, with negligible loss due to ALP production. This setup has the potential to set new constraints in the regime of large ALP mass. We further identify parameter regions in which boundary effects become important, in particular for hollow-core fibers, where signals due to ALPs can be significantly enhanced.
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Cosmology and Nongalactic Astrophysics

The Atacama Cosmology Telescope: Constraints on the anisotropic screening and birefringence effects with DR6

Darby M. Kramer, Alexander van Engelen, Frank J. Qu et al. (+14 more)

While we have learned much from recent surveys of the mm-wave sky, many secondary anisotropies of the CMB remain under-explored. We consider two of these here: the anisotropic screening induced by Thomson scattering of CMB photons off free electrons, and cosmic birefringence, the rotation of CMB polarization due to parity-violating physics beyond the standard model. To measure these effects, we apply state-of-the-art estimators for statistical anisotropy to the ACT Data Release 6 CMB data and construct noisy maps and power spectra of both effects. For anisotropic screening, we find no significant detection with the baseline data, and place an upper limit on its power spectrum that is two orders of magnitude above predictions from current reionization models. We obtain evidence for some foreground contamination at one of our frequencies that is consistent with expectations from extragalactic simulations. For our anisotropic birefringence analysis, we also find no detection and place an upper limit on the signal that is consistent with previous analyses. We report a corresponding upper limit on the Chern-Simons coupling term $g_{a \gamma} < 4.9 \times 10^{-2} / H_\mathrm{I}$, with $H_\mathrm{I}$ the inflationary Hubble scale. These analyses pave the way toward obtaining improved constraints with the next generation of ground-based CMB surveys.
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All authors Darby M. Kramer, Alexander van Engelen, Frank J. Qu, Christopher Cain, Irene Abril-Cabezas, J. Richard Bond, Vera Gluscevic, Carlos Hervías-Caimapo, Niall MacCrann, Mathew S. Madhavacheril, Jeff McMahon, Toshiya Namikawa, Bruce Partridge, Emmanuel Schaan, Neelima Sehgal, Cristóbal Sifón, Ed Wollack

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

Quantum Selection of Classical Histories

Omer Guleryuz

Can a finite quantum episode populate a classical future that the same prepared state never reaches deterministically? We show that it can, using inflation as a cosmological laboratory. In our supergravity realization, two classical continuations already exist, but the prepared state reaches only one without noise. A stable entropy direction temporarily becomes light without a tachyonic instability, allowing mode-derived phase-space fluctuations to access the competing continuation. Finite-horizon first passage assigns it a \(0.33\)–\(0.40\) conditional weight across three nearby CMB-normalized realizations, while suppressing the stochastic source restores its exact deterministic zero. The entropy sector then becomes heavy again, and the selected histories continue classically. A finite quantum episode can thus leave a lasting redistribution among classical futures.
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Cosmology and Nongalactic Astrophysics

Near universality of nonlinear transverse and radial velocity responses in spherical collapse with arbitrary radial profiles

Valerio Marra

The nonlinear relation between density and expansion is usually formulated for a homogeneous spherical top hat, which has a single local Hubble rate. A smooth spherical profile instead expands differently along ($H_{\parallel}$) and across ($H_{\perp}$) the radial direction-a direct signature of radial inhomogeneity. We show that, for growing-mode pressureless matter with a cosmological constant, the complete shellwise response is nevertheless fixed by one top-hat function. Given the local density contrast $\delta(t,r)$ and the enclosed contrast $\Delta(t,r)$, a transverse response and its derivative determine $H_{\perp}$ and $H_{\parallel}$. The linear and second-order limits are algebraic maps whose only dynamical input is the usual growth rate $f$. An exact equal-age construction supplies the nonlinear response without integrating an evolution equation. We check that it reconstructs full $\Lambda$LTB profiles to numerical precision. We also provide a derivative-aware, cosmology-independent three-term symbolic fit that requires only $f$, $\delta$, and $\Delta$. Across a representative set of matter-curvature-redshift combinations and for a shell located in the compensated transition, the maximum relative errors are $0.3\%$ and $0.7\%$ in the transverse and radial responses, respectively. This compact formulation separates the production of a density profile from its expansion response and makes the effect of radial gradients explicit.
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Cosmology and Nongalactic Astrophysics

Bumpy inflation from explosive particle production

Kaloian D. Lozanov, Xavier Pritchard and Misao Sasaki

We present a first-principles derivation of an effective inflaton potential with a bumpy feature. We consider the coupling of a spectator field \chi to the inflaton \phi such that \chi is massive enough for almost all values of \phi, but becomes massless when the inflaton crossed the value \phi_\star. This gives rise to a burst of \chi-particle production at \phi=\phi_\star. By taking the backreaction of the particle production, we obtain a bumpy feature in the effective potential. We discover that for certain choices of the interaction constants and field scale relevant for particle production, the backreaction-induced bumpy effective potential can lead to a sizable enhancement in the curvature perturbation. In particular, the enhancement can be large enough to generate observationally relevant amounts of primordial black holes and stochastic gravitational wave backgrounds.
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Cosmology and Nongalactic Astrophysics

Derivative hierarchy as the origin of kernel-dependent trends in Gaussian process reconstructions of the hubble parameter

Afaq Maqsood

We perform a model independent reconstruction of the cosmic expansion history using Gaussian Process regression, investigating how the smoothness properties of covariance kernels influence the inferred Hubble parameter. Using 32 cosmic chronometer measurements, we reconstruct $H(z)$ with the Matérn $3/2$, $5/2$, $7/2$, $9/2$, and Squared Exponential kernels, which form a well-defined hierarchy of differentiability. Across this hierarchy, we observe a systematic and monotonic trend in which increasing kernel smoothness is associated with progressively lower reconstructed values of the present-day Hubble constant $H_0$, accompanied by reduced statistical uncertainties. Rather than indicating a statistical preference for a specific kernel, this behaviour reflects the sensitivity of non-parametric reconstructions to the assumed smoothness prior encoded in the covariance function. The same ordering is reflected in descriptive goodness-of-fit statistics and remains stable when incorporating recent DESI DR2 BAO measurements and performing jackknife resampling tests, demonstrating robustness against individual data points and dataset variations. Additional analysis of derivative reconstructions shows that differences in kernel differentiability propagate into the local slope of the expansion history, providing a consistent interpretation of the observed ordering in $H_0$. Our results highlight that kernel smoothness plays an important role in Gaussian Process reconstructions and should be carefully accounted for when interpreting non-parametric cosmological inferences.
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Cosmology and Nongalactic Astrophysics · Cross-listed from hep-ph

$\mu$DM: a new mechanism for the baryon-dark matter coincidence

Wen Yin

For a relativistically decoupled thermal relic, the dark-matter energy-to-entropy ratio scales as $\rho_{\rm DM}/s\sim 10^{-3}m_{\rm DM}$. This is the familiar hot-dark-matter abundance relation. Immediately after weak-sphaleron freeze-out, the baryon asymmetry can be parametrized as $\rho_{\rm baryon}/s\sim 10^{-4}|\mu_B|$. Here $\mu_B$ is the baryon-number chemical potential. We propose a new class of models, called chemical-potential-matched dark matter ($\mu$DM), in which $|\mu_B|\sim m_{\rm DM}$, thereby providing a new route to the baryon-dark matter coincidence. As a concrete example of $\mu$DM, we consider an Affleck-Dine field whose excitations constitute dark matter. We also briefly discuss spontaneous electroweak baryogenesis associated with axion-like-particle walls. In the absence of entropy dilution, this coincidence mechanism generically points to dark matter in the eV-keV mass range. Its momentum distribution can nevertheless be cold if thermal production is dominated by Bose-enhanced stimulated emission. Alternatively, entropy dilution after both the dark-matter and baryon yields are fixed allows masses up to the MeV scale.
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Cosmology and Nongalactic Astrophysics

ELUCID-DESI II. Revealing dark matter mass, tidal, and velocity (MTV) fields using galaxy group phase information

Qingyang Li, Xiaohu Yang, Wensheng Hong et al. (+24 more)

We introduce a novel method for reconstructing the cosmic mass, tidal, and velocity (MTV) fields over the redshift range $0 < z < 0.6$ using the phase information of galaxy groups. This approach replaces the explicit theoretical bias correction typically needed to relate galaxy groups to the underlying dark matter density field with a simulation-calibrated statistical mapping, reducing a major source of systematic uncertainty and making the method directly applicable to spectroscopic redshift surveys such as the DESI Bright Galaxy Survey (BGS). We evaluate the performance of our MTV reconstruction pipeline with mock redshift surveys that include a comprehensive set of observational selection effects. The galaxy groups used as tracers are identified with an extended halo-based group finder applied to the DESI mock galaxy catalogue with an apparent magnitude limit of $m_z < 19.65$, yielding a galaxy number comparable to that of the DESI BGS faint sample ($m_r < 20.175$). Our tests show that the reconstructed velocities are accurate and unbiased, with a residual dispersion of $\sim 120\ \mathrm{km\,s^{-1}}$ across the redshift bins. The recovered velocity field allows us to shift galaxy groups to their real-space positions, thereby correcting for the Kaiser effect. By iteratively applying this Kaiser correction to the galaxy groups, we further reconstruct the tidal field and the mass-density distribution. The reconstruction is stable with respect to the grid resolution. Overall, our results demonstrate that this group-based phase-space reconstruction provides a robust pathway to recovering the dark matter MTV fields, with strong prospects for application to DESI BGS data.
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All authors Qingyang Li, Xiaohu Yang, Wensheng Hong, Feng Shi, Youcai Zhang, Jiaqi Wang, Junde Li, Yiyang Guo, Yingxiao Song, Huiyuan Wang, Yan-Chuan Cai, Yizhou Gu, Chengze Liu, Jiaxin Han, Zhongxu Zhai, Yu Yu, Yipeng Jing, Houjun Mo, Yuyu Wang, Hao-Ran Yu, Yingjie Peng, Weiguang Cui, Qi Guo, Liang Gao, Xi Kang, Weipeng Lin, Jie Wang

Cosmology and Nongalactic Astrophysics

Approximating the peculiar velocity distribution of dark matter halos with Tsallis statistics

Jun Pan and Ming Li

Dark matter halos, which host galaxies and galaxy clusters, have peculiar velocities far from thermal equilibrium. Characterizing the nonlinear and non-Gaussian features of this velocity distribution improves our understanding of the gravitational evolution of the cosmic web and supports related cosmological applications. We endeavor to establish a connection between the peculiar velocity distribution of halos and nonequilibrium statistical mechanics, with the objective of obtaining a model that is both concise and accurate for practical applications. We extracted halo samples from large N-body simulations and performed maximum-likelihood fits to the peculiar velocity distributions using a two-parameter Tsallis model, derived from non-extensive statistical mechanics. On the theoretical side, we reformulated the halo distribution in the superstatistics framework by means of a generalized Gram-Charlier expansion based on the gamma distribution. For halo peculiar velocities below 1000 km/s, the Tsallis model achieves 5 percent accuracy over z=0-2, with performance improving toward lower redshifts. Our results show that the halo velocity distribution becomes increasingly non-Gaussian and departs further from equilibrium over time. The best-fit parameters depend only weakly on mass, though low-mass halos exhibit slightly stronger non-Gaussianity. The two parameters, especially the velocity dispersion, offer promising probes of cosmological parameters. Theoretically, we find that in general the halo peculiar velocity distribution function is expressible as a superposition of a series of Tsallis distribution functions, while simulation results demonstrate that the zeroth-order approximation, namely a single Tsallis function, already achieves sufficient accuracy.
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Cosmology and Nongalactic Astrophysics · Cross-listed from astro-ph.HE

FRB 121102: No supernova-like ejecta or magnetar power, hinting at a binary WD merger

Eli Waxman, Eran O. Ofek and Doron Kushnir

We use measurements of the time-dependent dispersion measure of the repeating FRB 121102, together with earlier radio observations of its associated persistent radio source (PRS), to derive stringent constraints on its underlying “engine.” The energy held by the relativistic PRS plasma is $>10^{49.5}$ erg, and its age is $\approx60$ yr, corresponding to an underlying source power exceeding $10^{40}$ erg s$^{-1}$. If the underlying source is a neutron star, this implies a rotational rather than a magnetic energy source, consistent with a $\sim10$ ms, $\sim10^{12.5}$ G neutron star. Alternatively, accretion may also be a viable energy source. The velocity and the kinetic energy of the cold plasma confining the relativistic PRS plasma are inconsistent with it being typical supernova ejecta (unless a significant fraction of the ejecta mass is carried by high-density clumps of $\approx10^{-2.5}$ fractional size)- its expansion speed is limited to a few hundred km/s, which also implies that it was ejected from the source more than $\approx 10^3$ yr preceding the onset of relativistic PRS plasma emission. These constraints may be satisfied by a white dwarf binary merger progenitor system, where a fraction of a solar mass was ejected at a slow speed during and after the merger, and a rapidly rotating neutron star was formed after $\sim10^3$ yr thermal evolution period of the merger remnant.
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Cosmology and Nongalactic Astrophysics

Revisiting the Hubble tension with an inverse power-law early dark energy

Quan Zhou and Sibo Zheng

We propose a new early dark energy with a potential that has an inverse power-law asymptotic tail to alleviate the Hubble tension. Fitting this model to the datasets of CMB+BAO+SN+H0DN, one obtains a 68$\%$ confidence-level value of $H_0\sim 70.20^{+0.60}_{-0.47}$ km s$^{-1}$Mpc$^{-1}$ and a best-fit value of $H_0\sim 70.56$ km s$^{-1}$Mpc$^{-1}$ for index $n=10$. We show that this model can be tested by future data of CMB and matter power spectra. Finally, we briefly discuss fine-tuning problems related to this model.
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Wednesday 26 August

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

Direct and Indirect searches for DM-electron interactions in sub-GeV DM models

Marco Cirelli, Arpan Kar, Antoine Letessier-Selvon et al. (+1 more)

We analyze the complementarity between direct detection (DD) and indirect detection (ID) searches of sub-GeV dark matter (DM) in the context of two realistic models: the vector-portal (dark photon) and scalar-portal (higgs-portal) models. For DD we focus on the latest constraints on the DM-electron scattering from the present DAMIC-M experiment as well as its future projection. For ID we consider several existing X-rays/gamma-rays and cosmic-ray ($e^\pm$) observations as well as the upcoming MeV telescope COSI to obtain the corresponding bounds and projections on the DM annihilation rate, which are then translated in terms of the DM-electron scattering cross-section and compared with the DD bounds/projections. We properly take into account astrophysical and galactic propagation uncertainties. We find that the complementarity between DAMIC-M and ID works best for the vector-portal model, especially for the case where the vector mediator is heavier than the DM particle: in this case, the present DAMIC-M bound becomes comparable to (or better than, for some astrophysical configurations) the combined ID limit for $3\,{\rm MeV} \lesssim m_{\rm DM} \lesssim 20\,{\rm MeV}$. For other cases and mass ranges, the ID is in general more constraining and can also, for some mass ranges, constrain the parameter space below the neutrino floor, which is inaccessible to DD experiments.
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All authors Marco Cirelli, Arpan Kar, Antoine Letessier-Selvon, Harrys Lumengo-Kidimbu

Cosmology and Nongalactic Astrophysics

Cross-simulator transfer with foundation model summaries: Towards robust SKA-era reionization inference

Yannic Pietschke, Caroline Heneka, Ayodele Ore et al. (+1 more)

Simulation-based inference (SBI) for parameter estimation is vulnerable to model misspecification: neural summaries and density estimators trained on a specific forward model typically fail when applied to data drawn from another model, or from real observations, and no training simulator can capture the full observational pipeline of a real measurement exactly. We show that a self-supervised Vision Transformer (ViT), pretrained label-free on a fast approximate simulator, produces transferable data summaries that generalize across simulators. Without retraining, it can be reused as a frozen encoder to infer astrophysical parameters from a completely different simulator that resolves the radiative transfer explicitly, on which it has never seen either data or parameters. As a concrete use case in 21cm cosmology, SKATR, a ViT pretrained with a Joint Embedding Predictive Architecture (JEPA), serves as a foundation model for reionization inference from upcoming SKA measurements: SKATR is pretrained once on 67k low-cost, noiseless semi-numerical 21cmFAST lightcones, then frozen and applied to hydrodynamical Loreli II lightcones, where a lightweight conditional flow matching head infers five astrophysical parameters; the encoder is never shown Loreli data, its parameters, or any noise. In our comparison, SKATR yields the most precise and best-calibrated posteriors across all five parameters, matching the accuracy of the fully-supervised in-domain baseline while requiring 2.6x fewer radiative-transfer simulations. Under realistic SKA AA* noise, only SKATR remains simultaneously accurate, informative, and calibrated, outperforming even a supervised baseline retrained from scratch on noisy data. Self-supervised pretraining on computationally efficient semi-numerical simulations is therefore a viable route to calibrated, simulator- and noise-agnostic reionization inference for the SKA-era.
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All authors Yannic Pietschke, Caroline Heneka, Ayodele Ore, Romain Meriot

Cosmology and Nongalactic Astrophysics

HOLISMOKES – XVIII. Cosmology with strongly lensed type II supernovae: Effects of instrumental setups on $H_0$

J. Grupa, S. Taubenberger, S. H. Suyu et al. (+3 more)

The upcoming Rubin Observatory and subsequent follow-up observations should improve the determination of the Hubble constant ($H_0$) via time-delay cosmography of strongly lensed type II supernovae (LSNe II), by enabling the detection of many more such events. In our previous work, we developed a method for determining the supernova (SN) phase from spectral absorption features. Because obtaining spectra of faint targets such as distant SN II is expensive, we examined how low-resolution spectra influence the precision of time-delay retrieval, and consequently the precision on $H_0$. We considered spectral resolutions $R = \frac{\lambda}{\Delta \lambda}$ between 100 and 250, and we investigated three signal-to-noise ratio ($S/N$) values of 10, 15, and 20, for each resolution. Furthermore, we forecast the precision on $H_{0}$ achievable with $S/N=10$ and compared the observing time required to reach it with ground-based and space-based facilities. We find that the time delay can be determined without bias and with uncertainties as low as 1.3 days for the investigated resolutions and $S/N$ values when we combine time-delay measurements of multiple absorption lines. For a typical LSN II system (absolute magnitude $\sim-$17 mag in the rest-frame V band, source redshift of \zs = 0.8), the required exposure times range from multiple hours for ground-based observations to a few minutes for space-based observations with the JWST. Our predictions on the precision of $H_0$ for a single lensed SN range from 14.2% for $R = 100$ and $S/N$ = 10 to 7.5% for $R = 250$ and $S/N$ = 20, enabling a 1% determination of $H_0$ from $\sim$20 lensed SNe in the coming years.
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All authors J. Grupa, S. Taubenberger, S. H. Suyu, D. Sluse, S. Huber, C. Vogl

Cosmology and Nongalactic Astrophysics · Cross-listed from astro-ph.IM

RadialPaths: Radial profiles in multi-centred astronomical structures

Rafael S. de Souza

Radial profiles are routinely used to locate structural changes within resolved astronomical systems, but they generally define radial position relative to a single centre. In interacting, clumpy, or otherwise multi-centred structures, the radial location assigned to a feature can depend on the adopted centre. We introduce a centre-conditioned radial representation for connected structures with multiple centres. Distances are measured through the observed source footprint rather than across excluded background, and can be viewed as arrival times of fronts propagating from the centres. Each location is associated with the centre reached first and described by two complementary coordinates: relative centre–boundary depth and normalized progression away from that centre. For an ideal centred circular source, both reduce exactly to the familiar normalized radius $r/R$; in folded, elongated, or tailed geometries they separate because proximity to a lateral boundary and progression through the structure represent different notions of “outward”. Synthetic examples show that single-centre and equivalent-area radial descriptions do not retain the association between localized features and individual centres, whereas centre-conditioned profiles do. In two JADES DR2 systems, the resulting F277W profiles remain stable under modest changes in the adopted source footprint and one-pixel centre shifts. The construction assumes neither a light-profile law nor an overlapping flux decomposition, and the same radial geometry can be applied to registered maps of continuum light, colour, emission lines, stellar-population properties, and line-of-sight kinematics. An accompanying Python package, RadialPaths, provides the reference implementation together with documentation and online tutorials at \href{https://rafaelsdesouza.com.br/radialpaths} {GitHub}.
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Cosmology and Nongalactic Astrophysics · Cross-listed from astro-ph.IM

The MegaWave Radio Surveyor

T. Joseph W. Lazio, Evgenya Shkolnik, James Aguirre et al. (+40 more)

Several Decadal-level questions in astrophysics, exoplanets, astrobiology, and cosmology can be addressed only at low radio frequencies inaccessible from Earth. The MegaWave Radio Surveyor would open this largely-unexplored region of the electromagnetic spectrum with a space-based interferometer to (1)~Track the space weather of other stars; (2)~Detect magnetically-generated emission from exoplanets to probe their interiors and assess magnetic shielding of their atmospheres; (3)~Probe the Universe's evolution during the Dark Ages via the highly-redshifted HI hyperfine line; and (4)~Assess the role of cosmic rays and magnetic fields in the cosmic web. An Astrophysics Strategic Technology & Research Accelerator (ASTRA) Initiative concept, the MegaWave Radio Surveyor's science objectives respond to the Pathways to Discovery Decadal Survey and three other National Academies studies, and it would serve as a Formative Era mission in the Enduring Quests, Daring Visions roadmap. Developments in U.S. space industries enable this observatory to be realized. The MegaWave Radio Surveyor would offer a versatile, scalable, and resilient architecture capable of sensitive and simultaneous observations below 45~MHz and unprecedented angular resolution at these frequencies. The concept builds upon NASA's Sun Radio Interferometer Space Experiment (SunRISE), Star-Planet Activity Research CubeSat (SPARCS), and Lunar Surface Electromagnetics Experiment (LuSEE-Night). The MegaWave Radio Surveyor could leverage multiple elements of the Artemis program, such as access to and beyond cislunar space and communications, and there are opportunities to infuse new autonomy/AI modes for mission operations. By opening one of the last windows in the electromagnetic spectrum and pioneering space interferometry at unprecedented scales, the MegaWave Radio Surveyor would establish a transformational capability.
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All authors T. Joseph W. Lazio, Evgenya Shkolnik, James Aguirre, Stuart D. Bale, Judd Bowman, Ruby Byrne, Joseph Callingham, Tracy E. Clarke, Ivey Davis, Tim Dolch, Peter Driscoll, Anastasia Fialkov, Steven Furlanetto, Simona Giacintucci, Ravit Helled, Jacqueline Hewitt, Phil Hopkins, Andrea Isella, Daniel Jacobs, Eloy de Lera Acedo, Melodie M. Kao, Mary Knapp, L.V.E. Koopmans, Nicholas Kern, Jasmina Lazendic-Galloway, Susan T. Lepri, R. O. Parke Loyd, James P. Lux, James P. Mason, Raul Monsalve, Miguel Morales, Julian B. Muñoz, Rachel Osten, J. Sebastian Pineda, Jonathan Pober, Sam B. Ponnada, Leslie A. Rogers, Saurabh Singh, Jake D. Turner, Jackie Villadsen, Philippe Zarka, John ZuHorne, Ellen Zweibel

Cosmology and Nongalactic Astrophysics

The Impact of Magnitude Uncertainties and K-corrections on Standard Siren Measurements of the Hubble Constant

M. Pálfi and P. Raffai

Gravitational-wave standard sirens provide an independent probe of the Hubble constant. Dark siren analyses that rely on galaxy catalogues are sensitive to catalogue-related uncertainties. While incompleteness, weighting schemes, and redshift errors have been studied extensively, the impact of magnitude uncertainties and K-corrections has received little attention so far. We assess how magnitude errors and K-corrections propagate into the Hubble constant inference, and compare their impact to that of realistic spectroscopic redshift errors to determine their relevance. We use a modified version of the gwcosmo Python package to construct line-of-sight redshift priors from a complete, volume-limited mock galaxy catalogue up to $z<0.2$. We simulate and analyse a sample of $\sim200$ binary black hole events with luminosity weighting in the $B$- and $K$-bands and test different uncertainty models for redshifts, magnitudes, and K-corrections. The choice of luminosity-weighting scheme has a substantial impact on the inferred Hubble constant posterior, with the direct $B$- and $K$-band comparison producing differences comparable to the largest uncertainty-induced changes. Spectroscopic redshift errors produce the largest integrated changes in the Hubble constant posterior among the tested uncertainty treatments. Photometric magnitude uncertainties lead to substantially smaller, band-dependent deviations. In the $K$-band, the tested K-correction treatments have only a minor impact in the present low-redshift mock analysis, with the empirical correction slightly reducing the integrated deviation relative to the no-correction case. In realistic, flux-limited catalogues with larger localization areas and photometric or mixed redshift errors, the relative impact of magnitude uncertainties is expected to be even smaller, indicating that they need not be prioritized in near-future dark siren analyses.
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Cosmology and Nongalactic Astrophysics

Paleo-Detectors as a Novel Probe of Dark Matter-Nucleus Effective Interactions

Dionysios P. Theodosopoulos

Paleo-detectors are a proposed approach to the direct detection of dark matter (DM) based on the observation of DM-induced nuclear recoils. Rather than relying on large detector masses required for conventional detectors, paleo-detectors exploit extremely long integration times, using small samples of naturally occurring minerals that have resided deep underground and accumulated damage tracks over geological timescales of order a gigayear. In this contribution, we review recent theoretical predictions for the sensitivity of paleo-detectors to WIMP-nucleus interactions within the framework of a Non-Relativistic Effective Field Theory (NREFT). We discuss both elastic and inelastic scattering processes and consider isoscalar couplings, taking into account backgrounds from neutrinos and radiogenic sources. We present projected sensitivities of paleo-detectors for different readout and exposure scenarios and compare the reach of paleo-detectors to that of conventional direct-detection experiments. For DM masses in the range $1\ \mathrm{GeV}/c^2$-$10\ \mathrm{GeV}/c^2$, paleo-detectors are expected to achieve sensitivities exceeding those of conventional experiments for WIMP-nucleus interactions mediated by all NREFT operators, with only a weak dependence on the read-out scenario or target mineral. For larger DM masses, $10\ \mathrm{GeV}/c^2$-$5\ \mathrm{TeV}/c^2$, paleo-detectors are projected to attain sensitivities comparable to or surpassing conventional experiments for interactions mediated by several NREFT operators, depending on the specific read-out scenario and choice of target mineral.
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Cosmology and Nongalactic Astrophysics

The host galaxies of 2003fg-like type Ia supernovae

Lluís Galbany, Chris Ashall, Jing Lu et al. (+19 more)

SN~2003fg-like events are a peculiar type Ia supernova (SN~Ia) subtype characterized by broader light curves, higher near-infrared luminosities, and stronger carbon absorptions at early times. Here we present observations of the largest compilation of 2003fg-like SN Ia host galaxies to date, obtained with Integral Field Spectroscopy (IFS). For 20 objects, we study both the global host-galaxy properties and, for the first time for a sizeable sample, the local environment at the SN position. Globally, 2003fg-like SNe~Ia occur in galaxies with lower stellar mass, lower oxygen abundance, and marginally higher specific star-formation rate (sSFR) than those of normal SNe~Ia, although their hosts are not as extreme in such properties as superluminous SNe, nor representative of metal-poor dwarf-galaxy samples. Locally, the SN positions show lower star-formation-rate, stellar-mass surface densities, and lower sSFR, than normal SN~Ia environments, consistent with a significant preference for the outskirts of their hosts, while their stellar age indicators are typical. The most distinctive local property is metallicity, with 2003fg-like SNe~Ia occupying the most metal-poor environments among SNe~Ia. We also find a tentative positive correlation between the light-curve width and the oxygen abundance for 2003fg-like events. Our results imply that 2003fg-like SNe~Ia arise from the merger of two white dwarfs (WDs) or the core-degenerate scenario, but disfavor the single, rapidly rotating super-M$_{ch}$ C-O WD progenitor, as this channel requires a young stellar population that we do not observe at the SN positions. The preference of 2003fg-like SNe~Ia for low-metallicity environments suggests that they may have been more common in the early Universe. (abridged)
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All authors Lluís Galbany, Chris Ashall, Jing Lu, Jason T. Hinkle, Willem B. Hoogendam, Benjamin J. Shappee, Alaa Alburai, Ramon Sanfeliu, Joseph P. Anderson, Eddie Baron, Chris Burns, Georgios Dimitriadis, Inma Domínguez, Peter Hoeflich, Eric Y. Hsiao, Hanindyo Kuncarayakti, Joseph D. Lyman, Nidia Morrell, Mark M. Phillips, Sebastián F. Sánchez, Maximilian D. Stritzinger, Nicholas B. Suntzeff

Cosmology and Nongalactic Astrophysics

$\texttt{SPINE}$: Symbolic Models to Predict the Evolution of the $\Lambda$CDM Nonlinear Power Spectrum

Manvi Chauhan, Daniel J. Farrow, Ariel G. Sánchez et al. (+3 more)

We present $\texttt{SPINE}$ and $\texttt{SPINEX}$, a pair of analytical emulators developed to predict the nonlinear power spectrum based on its linear counterpart and several essential cosmological parameters within the range of $0.01\;h\;\mathrm{Mpc}^{-1} <k< 2\;h\;\mathrm{Mpc}^{-1} $. The primary difference between the two models is their parameterisation. Our methodology is grounded in the mapping originally proposed by Peacock and Dodds (1996). Both models are defined by clear mathematical expressions derived from symbolic regression, a machine learning technique that utilises genetic programming to identify analytical equations that accurately represent the underlying data. This approach provides a more interpretable and efficient alternative to conventional numerical methods that should also exhibit superior extrapolation behaviour beyond the training range. The emulators have been trained on the $\Lambda$CDM Quijote Latin Hypercube simulations. We provide fits for both emulators across three distinct scenarios: cosmologies within 20$\sigma$ of the Planck-2018 observations, a designated fiducial cosmology, and a broader range of cosmologies sampled from the Quijote simulations. Our findings indicate that $\texttt{SPINE}$ and $\texttt{SPINEX}$ maintain an accuracy of better than 5% in the majority of cases. These emulators provide a rapid alternative to numerical methods, and future initiatives will focus on developing expressions that incorporate galaxy bias and redshift-space distortions. This advancement aims to enhance the modelling of redshift space power spectra across multiple redshifts, enabling their application in large-scale cosmological surveys.
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All authors Manvi Chauhan, Daniel J. Farrow, Ariel G. Sánchez, Kevin Pimbblet, Marika Asgari, David M. Benoit

Cosmology and Nongalactic Astrophysics

Assembly bias from nuisance to probe II: Salvaging linear clustering from DESI and SDSS data

Nelson Padilla, Dante Paz and Iván Lacerna

Galactic conformity links the properties of neighbouring galaxies and is usually interpreted as a signature of assembly-biased galaxy occupation. We study projected and redshift-space compensated conformity statistics in colour-selected DESI BGS and SDSS MGS samples. These combine correlations of related galaxy populations, suppressing shared nonlinear clustering contributions while retaining a differential large-scale response. We test whether this exposes the linear matter correlation-function shape where ordinary colour-selected clustering has a scale-dependent nonlinear response. We split galaxies into red and blue subsamples and measure ordinary correlations, conformity, and compensated combinations in projection and redshift-space monopoles, using central primaries by default. We fit linear matter templates, diagnose the response with effective kernels, and compare with MTNG, FLAMINGO, and MDPL2–SAG. Ordinary high-colour clustering broadly follows the linear templates but develops a scale-dependent small-scale response. In DESI, $\Delta f_0(s)$, projected $\Delta f(r_p)$, and $C_w(r_p)$ track the linear matter shape substantially further into the nonlinear regime, consistent with suppression of nonlinear clustering modes while leaving a linear-matter-like mode visible. The effect is stronger for central-primary and dense samples. Projected effective kernels are enhanced at low line-of-sight separations, helping the residual resemble $\xi_{\rm mm}^{\rm lin}(r_p)$ rather than $w_{\rm mm}^{\rm lin}(r_p)$. Simulations reproduce the qualitative behaviour with model-dependent amplitudes and residual scale dependence. These results suggest that assembly-sensitive population differences can filter nonlinear clustering modes, although surviving nonlinear contamination must be calibrated before precision cosmological use. (abridged)
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Cosmology and Nongalactic Astrophysics · Cross-listed from hep-ph

Getting Warmer: IceCube Nears Freeze Out

Mainak Mukhopadhyay and Gordan Krnjaic

IceCube has recently detected a diffuse population of high-energy neutrinos arising from the Milky Way. We use this high-significance detection to place new limits on dark matter (DM) annihilation to neutrinos with two complementary approaches. The first method uses the background-subtracted Galactic longitude distribution of shower events to place a conservative bound on the DM annihilation cross section that does not rely on any assumed Galactic cosmic ray emission model; the resulting limits on the velocity-averaged annihilation cross section improve upon existing bounds by factors of a few. The second method uses the template-dependent neutrino energy spectra from the Inner Galaxy, inferred under different Galactic cosmic ray emission models. This complementary approach shows that the inferred Galactic neutrino intensities are already sensitive to DM contributions near the thermal-relic benchmark for a range of TeV-scale DM masses, though this comparison is more model-dependent. Our results demonstrate that measurements of diffuse Galactic neutrino emission can be used as a powerful probe of DM annihilation into neutrinos. Future observations with IceCube-Gen2 and KM3NeT will substantially extend this sensitivity, potentially allowing a decisive test of the thermal freeze-out mechanism with Galactic neutrino observations.
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Cosmology and Nongalactic Astrophysics · Cross-listed from astro-ph.GA

Barren but not Empty: The Impact of Void Environments on Galaxy and Halo Populations

Anita M. Schiller, Benjamin A. Seidel, Rhea-Silvia Remus et al. (+2 more)

The combination of gravitational collapse and an accelerating expansion of the Universe drive an increasing fraction of volume toward becoming low-density voids across cosmic time. These regions present a unique environment due to their low density, which leads to them behaving similarly to "pocket universes" with modified cosmological parameters. Since the formation and evolution of galaxies is strongly tied to the environment, we aim to discern how voids alter halos and galaxies compared to the general population in the universe. We use the hydrodynamical cosmological simulation suite Magneticum Pathfinder and introduce a set of void halo mass functions (VHMFs), which trace the halo population as a function of void-centric distance. We find galactic halos in voids to be overall less massive than in the general simulation volume. This discrepancy between void and field halos evolves with time as the voids grow more underdense, while the populations are still very similar at cosmic dawn. Expanding on this, we evaluate whether specific properties of the voids affect the VHMFs. We find the only relevant parameter for the void halo population to be the core density, a measure of the strength of underdensity. To assess the impact of the density environment on the evolution of galaxies, we investigate whether there are any distinctions between void and field galaxies with regard to stellar properties. We compute the stellar-mass function, halo mass-stellar mass relation, as well as the star-forming main sequence using the same void-centric shells. Although voids contain overall less stellar mass, the distribution of galaxies along the stellar mass-halo mass follows that of other regions. This implies that SF proceeded "conventionally" in void regions, in agreement with more recent observations.
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All authors Anita M. Schiller, Benjamin A. Seidel, Rhea-Silvia Remus, Lucas C. Kimmig, Klaus Dolag

Cosmology and Nongalactic Astrophysics · Cross-listed from astro-ph.GA

Scatter, bias, and chaos of satellite orbits in triaxial dark matter haloes

Barry T. Chiang, Frank C. van den Bosch and Michael A. Keim

The pericentric distances of satellite galaxies govern their tidal stripping, quenching, and survival, yet their orbits are almost universally computed in spherical host haloes, whereas dark matter haloes are generically triaxial. We quantify, orbit by orbit, the error this simplification incurs. We integrate $10^6$ satellites, drawn from a cosmological infall distribution, in static NFW hosts of systematically varying triaxiality at fixed mass profile. Triaxiality leaves the population medians of pericentre, apocentre, and orbital period essentially unchanged. Instead, successive pericentres of an individual orbit scatter by 5-23% depending on host shape, irrespective of orbital energy; the minimum pericentre distance reached within a Hubble time shrinks systematically by up to 21%, enhancing the peak tidal mass loss. This triaxiality-driven orbital dephasing is overwhelmingly regular rather than chaotic; chaotic satellite orbits are common and dominate the near-centre pericentric passages in strongly flattened hosts, but diverge on time-scales far exceeding the Hubble time. Satellite orbits spherically reconstructed via direct backward integration in a truly triaxial host diverge by a tenth of the virial radius within 2-4 Gyr, with comparable uncertainties sourced separately by the unconstrained shape of the host and by its unknown absolute orientation. For the Milky Way dwarf Triangulum II, the unknown halo shape and orientation alone spread the inferred pericentre by ~50%, five times its reported uncertainty and more than ten times the LMC-induced shift, and bias it by 6-70%. This host-shape uncertainty can dominate satellite orbital error budgets and should be incorporated in future inferences.
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Cosmology and Nongalactic Astrophysics

Primordial Black Holes as Cosmic Architects: Imprints of an extended mass function

Alberto Magaraggia, Nico Cappelluti, Günther Hasinger et al. (+2 more)

Primordial black holes (PBHs) remain compelling dark-matter candidates and possible relics of early-Universe physics, with observable imprints across both cosmological structure formation and gravitational-wave astronomy. We investigate the consequences of a PBH population described by an extended, physically motivated mass function shaped by features in the thermal history of the early Universe. We compute the associated Poisson contribution to the matter power spectrum and propagate its effects to the halo mass function, the cosmic star-formation rate density, and the reionization history. The PBH component produces a moderate enhancement of small-scale power, leading to earlier low-mass halo formation and a correspondingly mild increase in the high-redshift star-formation rate density while remaining consistent with current constraints on the Thomson optical depth. We then evaluate the merger-rate distribution expected for current and future gravitational-wave detectors. In the stellar-mass regime, the predicted PBH binary population occupies the region probed by LIGO-Virgo-KAGRA and can contribute to the observed compact-object merger population. For LISA, the detectable signal is dominated by intermediate-mass binaries with component masses of $10^3$-$10^4\,M_\odot$, with cumulative rates of order a few events per year extending to redshifts as high as $z \sim 50$. The detection of such high-redshift intermediate-mass black hole mergers would constitute a distinctive signature of a primordial origin, providing evidence that PBHs contribute non-negligibly to the dark matter budget and may have served as early seeds for the supermassive black holes observed at later cosmic epochs.
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All authors Alberto Magaraggia, Nico Cappelluti, Günther Hasinger, Maël Gonin, Priyamvada Natarajan