Cosmology and Nongalactic Astrophysics · Cross-listed from hep-ph
Stochastic gravitational waves from narrow-band cosmological magnetic fields
Abdias Aires and Tatsuya Daniel
We calculate the spectrum of gravitational waves generated by a cosmological
magnetic field with a narrow-band power spectrum. For a spectrum narrowly peaked at a comoving wavenumber $k_c$, we find that the gravitational wave signal peaks at $2k_c$ and has a sharp cutoff at this scale. We apply this result to an ultralight dark matter model of magnetogenesis operating around recombination, in which an
axion-
photon coupling generates a helical
magnetic field by parametric resonance. We determine the conditions for the resulting gravitational waves to enter the frequency range of
pulsar timing experiments. Although the required frequency can be reached for sufficiently large coupling, the corresponding amplitude is below the experimental sensitivity for physically allowed energy densities of the
magnetic field. We generalize this conclusion to models of magnetogenesis operating at other epochs, estimating as $T \simeq 160 \mathrm{MeV}$ the temperature of a magnetogenesis process assumed to be the source of the
stochastic gravitational wave background suggested by
pulsar timing arrays. We place the lower bound $T \gtrsim 1$-$10 \mathrm{MeV}$ on such viable models.
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Cosmology and Nongalactic Astrophysics
Narrowing down the Hubble constant value by exploiting the extended surface brightness of the supernova Refsdal host galaxy
S. Schuldt, C. Grillo, S. H. Suyu et al. (+7 more)
We present the first inference of the Hubble constant and matter density parameter from a strongly lensed
supernova by exploiting the mass model of a
galaxy cluster enhanced by an extended surface brightness reconstruction. Building upon the recent mass model of the
galaxy cluster MACS J1149.5+2223, relying on the identified image positions only, we include the surface brightness distribution of the SN Refsdal host, to infer some cosmological parameter values within a flat LCDM framework. We consider two cosmological parameterizations, with either H0 and {\Omega}m or H0 alone treated as free parameters, acknowledging the milder dependency on {\Omega}m when incorporating additional constraints from the SN host. We explore four different mass-model realizations to assess some of the systematic uncertainties associated with the constraint weighting and source reconstruction. Although known as one of the main possible systematic effects, including influences from the external convergence, we deliberately keep the cluster total mass parametrization fixed to that of the previously published point-like mass model to enable a fair comparison. This reveals that incorporating 77,000 HST pixels reduces the uncertainty on the inferred value of the Hubble constant by a factor of 2.0, while all model realizations remain mutually consistent. Our final measurements are $H_0 = 65.0^{+2.0}_{-1.8}$ km/s/Mpc and $\Omega_m = 0.30^{+0.08}_{-0.09}, in agreement with previous results. This corresponds to a substantially improved precision, reaching a remarkable 3.0% uncertainty on the value of H0 given our cluster total mass parameterization. The contributions of the uncertainties on the lens total mass and on the measured time delays to the final H0 error are now comparable, indicating that future improvements in cluster-scale time-delay cosmography will increasingly depend on (abridged version).
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All authors S. Schuldt, C. Grillo, S. H. Suyu, A. Acebron, L. Bazzanini, P. Bergamini, G. Di Rosa, A. Halkola, A. Mercurio, P. Rosati
Cosmology and Nongalactic Astrophysics
The road to $H_0$, $\Omega_m$, and $w$ with a global neutrino-telescope network
Pavel Zhelnin, Gonzalo Herrera, Nicholas Kamp et al. (+1 more)
The newly measured correlation between the
neutrino and X-ray luminosities of Seyfert
galaxies has yielded the first
neutrino-based measurement of the Hubble constant. Building on this result, we forecast the reach of a global
neutrino-
telescope network by 2030, utilizing full-sky IceCube exposures combined with KM3NeT-ARCA and Baikal-GVD. We find that this 2030 configuration sharpens the
neutrino-measured Hubble constant from today's $H_0 = 66^{+44}_{-37}$ to $H_0 =66^{+15}_{-13}$ km s$^{-1}$ Mpc$^{-1}$. Additionally, we project that the disk-corona slope of the
neutrino X-ray luminosity relation ($L_\nu\propto L_X^\beta$) will reach $\beta=0.72\pm0.04$, enabling a $\geq \!5\sigma$ exclusion of the calorimetric value $\beta=1$. Finally, we show that, if a high-
redshift population of
neutrino sources, such as JWST's "little red dots," is identified and obeys the same luminosity relation, we can obtain a new independent measurement of the matter density $\Omega_m$ and the dark energy equation-of-state parameter $w$.
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All authors Pavel Zhelnin, Gonzalo Herrera, Nicholas Kamp, Carlos A. Argüelles
Cosmology and Nongalactic Astrophysics · Cross-listed from hep-ph
Seeing in the Dark: Gravitational Waves from Resonant Production of Dark Photon Dark Matter
Yanou Cui, Pankaj Saha and Evangelos I. Sfakianakis
Ultralight dark
photons (DPs) are well-motivated dark matter candidates. A promising yet underexplored mechanism for their relic abundance is parametric resonance in the Abelian-
Higgs model that generates the DP mass. We advance previous analytical studies through dedicated 3D
lattice simulations that capture important nonlinear effects, including backreaction and relic partitioning between the dark
Higgs and DPs. We further predict the associated
stochastic gravitational-wave (GW) signal, which can be within reach of a broad range of detectors, opening a new avenue to probe ultralight DP dark matter.
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Cosmology and Nongalactic Astrophysics
A Burst of Reionization in the Dark Ages
Neal Weiner, Soubhik Kumar, Wenzer Qin et al. (+3 more)
Primordial overdensities at small scales can be significantly larger than those observed at large scales. As a result, they can collapse much earlier, at
redshifts $z \sim 100$. In these collapsed
halos,
stars and black holes can form, where they can then contribute to an early reionization of the universe. If this epoch is temporary, the free electrons will recombine yielding a low level of ionization leading into
cosmic dawn. This contributes to the optical depth of the universe, and adds more weakly to low-$\ell$ polarization signals of ionization compared to later sources. We study the effects of a
redshift-localized source of reionization $\Delta \tau_{burst}$ in the context of a broad suite of cosmological data to constrain this scenario, finding a preference of approximately $\sim 2-2.5\sigma$ for a new contribution. Regardless of Planck reprocessing used (PR3 - SRoll2+plik or PR4 - LoLLiPoP+CamSpec/HiLLiPoP), the results are consistent, favoring a new contribution $\Delta \tau_{burst} \sim 0.012$ ($0.001 < \Delta \tau_{burst} < 0.022$ at 95%) and a similar total optical depth $\tau \sim 0.073$. The precise era of reionization is somewhat discrepant depending on the higher-$\ell$ reprocessing used, with HiLLiPoP favoring $z\sim 45$, CamSpec $z\sim 100$ and plik $z\sim 165$. If such a source is present at $40\lesssim z\lesssim150$, LiteBIRD should be able to detect it, while Simons Observatory should also constrain it.
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All authors Neal Weiner, Soubhik Kumar, Wenzer Qin, Zilu Zhou, Yacine Ali-Haïmoud, Hector Afonso G. Cruz
Cosmology and Nongalactic Astrophysics · Cross-listed from hep-ph
A scalar-extended ${\rm U(1)_{L_{\mu}-L_{\tau}}}$ explanation of the LUX-ZEPLIN 248 keV excess
Dipankar Pradhan and Abhik Sarkar
The recently observed dark matter (DM) nuclear recoil event at an energy of $248 \pm 23\,(\text{stat.}) \pm 23\,(\text{syst.})\,\text{keV}$ at the LUX-ZEPLIN (LZ) experiment, favoring an inelastic scattering interpretation, has motivated various beyond the Standard Model (BSM) scenarios aimed at explaining the observed excess. In particular, this provides an opportunity to probe models that naturally accommodate inelastic DM scattering. In this work, we explore one such possibility by extending the $\rm U(1)_{L_{\mu}-L_{\tau}}$ model with two complex scalar fields, $\Phi$ and $S$, carrying charges $-1$ and $+2$, respectively, under the $\rm U(1)_{L_{\mu}-L_{\tau}}$ gauge
symmetry. These charge assignments allow a trilinear interaction between the two scalar fields, which is crucial for generating the DM mass splitting. Following the spontaneous breaking of the $\rm U(1)_{L_{\mu}-L_{\tau}}$
symmetry, with $S$ acquiring a
vacuum expectation value and generating a mass for the BSM gauge
boson $Z_{\mu\tau}$, the real and imaginary components of $\Phi$ acquire a mass splitting. This naturally gives rise to an inelastic DM scattering scenario that can accommodate the LZ excess. We perform a likelihood-based assessment of the sensitivity of the model parameters to the observed event while consistently accounting for other relevant phenomenological constraints. Finally, we discuss the prospects for probing the viable parameter space at future experiments.
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Cosmology and Nongalactic Astrophysics
Cosmic topology. Part IId. Eigenmodes and correlation matrices of lens spaces
Mikel Martin Barandiaran, Catherine Petretti, Stefano Anselmi et al. (+16 more)
The global
topology of the Universe is a longstanding open question. In this work, we examine the statistical signatures of a positively curved universe with a Friedmann–Lemaitre–Robertson–Walker metric and the
topology of a lens space $L(p,q)$. Since these
manifolds are generally statistically anisotropic and inhomogeneous, their
cosmic microwave background (CMB) covariance
matrices contain non-zero off-diagonal entries that depend on observer location. We compute these full harmonic-space covariance
matrices for scalar perturbations for arbitrary lens spaces and observer position. Using the Kullback–Leibler divergence, we assess the distinguishability of these spaces from a simply connected three-sphere with the same
curvature. The results show that topological signatures can still be significant in a
cosmic-variance-limited regime even when the length, $d_{\rm NC}$, of the shortest loop around the Universe through the observer exceeds the diameter, $d_{\rm LSS}$, of the last-scattering surface by up to $10\%$. This distinguishability depends on the
curvature, the lens space and the observer position mainly through the ratio $d_{\rm NC}/d_{\rm LSS}$, which is set not only by the
curvature radius but also by $p$, $q$ and the observer location. Therefore, for any value of the spatial
curvature, however small, there are lens spaces and observer positions for which $0.985\,d_{\rm LSS}<d_{\rm NC}<1.1\,d_{\rm LSS}$. Such observers would find no matched circles in the CMB large enough to have been detected to date, yet the
topology would remain potentially discoverable through its statistical signatures.
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All authors Mikel Martin Barandiaran, Catherine Petretti, Stefano Anselmi, Deyan P. Mihaylov, Anna Negro, Glenn D. Starkman, Andrius Tamosiunas, Yashar Akrami, George Alestas, Javier Carrón Duque, Craig J. Copi, Fernando Cornet-Gomez, Linn Htat Lu, Andrew H. Jaffe, Arthur Kosowsky, José Javier Ortega Gómez, Ricardo G. Rodrigues, Amirhossein Samandar, Cynthia Trendafilova
Cosmology and Nongalactic Astrophysics · Cross-listed from gr-qc
A Pairwise Surrogate for Gravitational-Wave Spectra from Highly Relativistic Vacuum Bubble Collisions
Malte Buschmann and Toby Opferkuch
Gravitational waves from
vacuum first-order phase transitions probe the nonlinear dynamics of relativistic bubble collisions. Predicting their spectrum requires resolving Lorentz-contracted scalar bubble walls throughout a volume containing many bubbles, making the large-boost regime prohibitively expensive for direct
lattice simulations. We develop a simulation-based pairwise surrogate that separates the microscopic collision dynamics from the geometry of the multi-bubble transition. This utilizes
symmetry-reduced $(1+1)$-dimensional scalar-field simulations to build a library of two-bubble gravitational-wave spectra, including the nonlinear post-collision
evolution. These spectra are combined with
geometric weights that account for screening by other bubbles. We test the two-bubble spectra and the reconstructed spectra of three- and many-bubble systems against full $(3+1)$-dimensional
lattice simulations. Not only can the surrogate be orders of magnitude cheaper computationally, but it also provides access to highly relativistic collisions beyond the practical reach of direct many-bubble simulations. This provides a route to studying how the spectral amplitude and shape depend on the collision boost and scalar potential.
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Cosmology and Nongalactic Astrophysics · Cross-listed from astro-ph.IM
Opening the Black Box: What Neural Networks Learn from Pulsar Timing Array Data
James Alvey, Andrea Mitridate, Mauro Pieroni et al. (+1 more)
In recent years, simulation-based inference (SBI) methods have been proposed to address several data-analysis challenges faced by existing and planned gravitational-wave experiments. For example, SBI classification has recently been shown to significantly improve the prospects for detecting anisotropies in
pulsar timing array (PTA) data. In this work, we use a simple toy model of a PTA to provide a more pedagogical explanation of how, and under which circumstances, SBI-based detection can improve on classical detection statistics for gravitational-wave background anisotropies.
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All authors James Alvey, Andrea Mitridate, Mauro Pieroni, Joseph D. Romano
Cosmology and Nongalactic Astrophysics
An analytical model for non-local stochastic field-level galaxy bias on the sphere
Maximilian von Wietersheim-Kramsta, Nicolas Tessore, Benjamin Joachimi et al. (+3 more)
We present the `Bias of Overdensities in Large-scale Tracers on the Sphere' (BOLTS) model, a novel analytic
galaxy bias model for projected fields on the sphere that incorporates stochasticity and non-locality already at linear order while enforcing physicality and statistical isotropy. Rather than as a deterministic transfer function, we model
galaxy bias as a statistically isotropic random field, allowing stochasticity to enter through fluctuations in the bias itself. The construction yields an explicit decomposition into a linear, non-local
stochastic and deterministic components in harmonic space. We fit the model parameters to the projected power spectra measured in large-volume hydrodynamical simulations (FLAMINGO), enabling sampling of
galaxy populations from simulated matter fields while conditioning on
galaxy properties such as
halo mass or
redshift. By construction, the model reproduces the two-point statistics down to the simulation resolution, and without being calibrated on it, BOLTS recovers the equilateral bispectrum within the sample variance of the simulation down to comoving scales of $\mathcal{O}(10 \, \mathrm{Mpc})$ for
halo masses $ M_{\rm{h}} > 10^{11.5}\,\rm{M}_{\odot} $ over
redshifts $0 < z < 3$. Relative to local bias prescriptions, it more accurately captures amplitude-phase correlations and mode coupling in the measured wavelet phase harmonics wherever the stochasticity of the tracers exceeds their discreteness, including low
redshifts and lower
halo masses $M_{\rm{h}} = 10^{11.5}\,\rm{M}_{\odot}$ where non-linearities become important. This model enables efficient field-level forward modelling for simulation-based inference and model comparison with large
datasets from forthcoming
galaxy surveys including Euclid, Rubin LSST, and Roman, while improving the accuracy of
galaxy bias modelling with respect to standard linear deterministic models.
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All authors Maximilian von Wietersheim-Kramsta, Nicolas Tessore, Benjamin Joachimi, Qianjun Hang, Niall Jeffrey, Joop Schaye
Cosmology and Nongalactic Astrophysics · Cross-listed from astro-ph.GA
Modeling CO Line Luminosity Using FIRE Simulations: I. Methodology and Validation of Molecular Gas and CO Abundance
Doğa Tolgay, Norman W. Murray, Dongwoo Chung et al. (+5 more)
We present a post-processing pipeline that predicts CO line luminosities, molecular hydrogen masses, and CO abundances for
galaxies in the Feedback in Realistic Environments (FIRE-2) simulations, as a first step toward CO response functions for line intensity mapping mocks. SKIRT gives the radiation field reaching each gas
cell. CLOUDY, tabulated on a five-parameter grid (
metallicity, density, turbulent velocity, radiation field, cloud scale) and interpolated, gives $L'_{\rm CO(1-0)}$ and the $\rm H_2$ and CO masses. In this first of three papers we validate the pipeline against observations. For Milky Way (MW) molecular clouds, the predicted $L'_{\rm CO(1-0)}$ rises sharply at $A_V\sim1$ and matches the observed values above that column. For a uniform $3\,Z_\odot$ the summed luminosity is within 35% of the observed total. A factor of three increase in
metallicity changes the total $L'_{\rm CO(1-0)}$ by an order of magnitude. Along MW sight lines, the predicted $N_{\rm CO}/N_{\rm H_2}$ reproduces the observed upturn within 0.3 dex in $N_{\rm H_2}$ but falls below the data at higher columns. At $z=0$ our molecular gas masses agree with xCOLD GASS for ${\rm SFR}\gtrsim0.3\,M_\odot\,yr^{-1}$ and are converged across our simulation resolutions. At $z\gtrsim1$ observed gas masses exceed ours at fixed stellar mass, though selection effects and conversion-factor assumptions limit this comparison. CO luminosities are compared with extragalactic observations in Paper II. Capturing the
metallicity-dependent dust shielding of CO from photodissociation is essential for modeling CO emission in low-mass and high-
redshift galaxies.
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All authors Doğa Tolgay, Norman W. Murray, Dongwoo Chung, J. Richard Bond, Nathan J. Carlson, Robert Feldmann, Andrew Wetzel, Guochao Sun
Cosmology and Nongalactic Astrophysics
HI intensity mapping with MeerKAT: A measurement of the 21-cm auto-spectrum on cosmological scales
MeerKLASS Collaboration, Matilde Barberi-Squarotti, José L. Bernal et al. (+16 more)
We report a direct measurement of the 21-cm signal from neutral hydrogen (HI) via the intensity mapping technique at
redshift $z = 0.42$ through its power spectrum at cosmological scales $0.095\,h\,{\rm Mpc}^{-1}<k<0.245\,h\,{\rm Mpc}^{-1}$. We analyse intensity maps observed in the frequency range $971.2\,{\rm MHz}<\nu<1023.6\,{\rm MHz}$ during the 2021 observational campaign of the MeerKAT Large Area Synoptic Survey (MeerKLASS) spanning an area of approximately $236\,{\rm deg}^2$. Capitalising on the depth of this survey, we divide the data set into multiple observationally independent subsets. After performing blind contaminant separation independently on each subset, we exploit internal cross-correlations to suppress the instrumental noise plateau and isolate the cosmological signal from residual systematics. Although the subsets' auto-spectra show the presence of excess power that we deem linked to still unresolved systematics, the cross-spectra measurements satisfactorily pass a battery of null and robustness tests. We introduce a multi-subset formalism to infer the amplitude of the HI auto-spectrum from our internal cross-spectra measurements while marginalising the potential signal loss that occurs during data processing, reaching a detection with signal-to-noise ratio of 6.2. We constrain the clustering amplitude of the signal in terms of the HI
cosmic abundance and its linear bias, measuring $10^3\,\Omega_{\rm HI} b_{\rm HI}=1.271^{+1.080}_{-0.598}$. This direct measurement marks a milestone in demonstrating the effectiveness of the HI intensity mapping technique for future surveys with the SKA Observatory, of which MeerKAT is a precursor.
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All authors MeerKLASS Collaboration, Matilde Barberi-Squarotti, José L. Bernal, Philip Bull, Stefano Camera, Isabella P. Carucci, Zhaoting Chen, Steven Cunnington, Brandon N. Engelbrecht, José Fonseca, Keith Grainge, Wenkai Hu, Melis O. Irfan, Yichao Li, Mário G. Santos, Marta Spinelli, Jingying Wang, Amadeus Witzemann, Laura Wolz
Cosmology and Nongalactic Astrophysics · Cross-listed from astro-ph.GA
Too many or too bright? Status and perspectives in the study of the UV Luminosity Function at z>10
A. Fontana, H. Atek, V. Bromm et al. (+20 more)
The finding that
galaxies in the first 500Myr were much more numerous and/or brighter than expected is often cited as one of the main discoveries of the James Webb Space
Telescope in its first four years of operation. This result is now solidly based on an impressive number of surveys that have detected, spectroscopically confirmed, and characterized a relatively large sample of
galaxies up to z=14.44, the
redshift of the most distant
galaxy currently known. This finding has motivated the introduction of additional physical mechanisms into theoretical models to reproduce the observed numbers and luminosities. These results contrast with the failure, despite ongoing efforts, to confirm any
galaxy candidate beyond this
redshift. This review summarizes the status of the search for and characterization of
galaxies at z>9, focusing on the
evolution of the UV Luminosity Function (UVLF), which is the main statistical description of the
galaxy population that can be obtained at these
redshifts. We first provide a comprehensive overview of the full set of JWST data obtained so far. We perform a 'meta–analysis' on the entire data set and provide a simple yet effective description of the global
evolution of the UVLF, averaging over the various surveys. We also compare these results extensively with theoretical models that were developed to match the new JWST observations and that explore different physical mechanisms able to drive the observed
evolution. We conclude with a summary of the contrasting results regarding the search for
galaxy candidates at z>15, and outline the requirements for future surveys aimed at breaking this barrier.
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All authors A. Fontana, H. Atek, V. Bromm, A. J. Bunker, M. Castellano, P. Dayal, F. D'Eugenio, D. Elbaz, A. Ferrara, S. L. Finkelstein, S. Fujimoto, M. Giavalisco, Y. Harikane, C. Kobayashi, F. Pacucci, P. G. Pérez-González, P. Rosati, A. Trinca, R. Tripodi, P. Santini, E. Vanzella, A. Venditti, A. Weibel
Cosmology and Nongalactic Astrophysics
A New Era for Supernova Science with the James Webb Space Telescope
Justin Pierel, David Coulter, Christa DeCoursey et al. (+17 more)
Supernovae (SNe) are excellent probes of the physical, chemical, and cosmological context of
galaxies across the history of the Universe. The James Webb Space
Telescope (JWST ) has a truly unique combination of wavelength, sensitivity, and resolution, providing a new window into SN physics, progenitors, dust production,
redshift evolving stellar populations, and cosmology since its launch. Here we summarize the astounding observations JWST has made of SNe in its first few years of operations, as well as the corresponding advancements in our understanding of the Universe. This includes detailed views of nearby SNe, the first spectroscopic samples of high-z SNe, and a significant number of gravitationally lensed SNe valuable for both cosmological inference and high signal-to-noise (S/N) spectroscopy. While the upcoming Nancy Grace Roman Space
Telescope is expected to revolutionize space-based time-domain astronomy, JWST and its unique capabilities will continue to play a complementary role by providing high-precision spectroscopic and photometric data for a broad range of SN science cases.
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All authors Justin Pierel, David Coulter, Christa DeCoursey, James DerKacy, Ori Fox, Melissa Shahbandeh, Matthew Siebert, Michael Engesser, Conor Larison, Thomas Moore, Armin Rest, Rodrigo Angulo, Michael Dulude, Eiichi Egami, Massimo Griggio, Mitchell Karmen, Xiaolong Li, Estefania Padilla Gonzalez, Koji Shukawa, Louis-Gregory Strolger
Cosmology and Nongalactic Astrophysics · Cross-listed from gr-qc
Holographic dark energy from generalized entropies and extended infrared cut-offs
Ke Chen, Simone D'Onofrio, Sergei D. Odintsov et al. (+1 more)
We study holographic dark energy models constructed from generalized
entropy functionals and local infrared cut-offs. Three
entropies (Barrow and the three and five-parameter generalized
entropies) are each combined with the Granda-Oliveros (GO) cut-off and two extensions, one adding a $\gamma H^{-2}$ term and one a $\gamma \ddot{H}/H$ term, the latter raising the dark-energy
evolution equation to second order. The nine resulting models are constrained against DESI DR2 BAO, Pantheon+ and a Planck compressed CMB likelihood through an MCMC analysis, and compared using the Akaike and
Bayesian information criteria. The Hubble constant is stable across all models. The $H^{-2}$ term is unconstrained in every case, as it becomes relevant only in the far future, and never improves on the GO cut-off. The $\ddot{H}/H$ term, instead, is tightly constrained for Barrow and $S_5$, where it improves the fit substantially, but not for $S_3$. The best fit is obtained for Barrow
entropy with the $\ddot{H}/H$ cut-off, yet the Barrow exponent remains compatible with zero in all cases. The data thus favour a higher-order infrared cut-off, while showing no significant evidence for a departure from the Bekenstein-Hawking area law. We also investigate the dark energy equation of state (EoS) of $S_3$ and $S_5$, discovering quintessence-like behavior and phantom crossing.
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All authors Ke Chen, Simone D'Onofrio, Sergei D. Odintsov, Tanmoy Paul
Cosmology and Nongalactic Astrophysics
Pinpointing the cosmic web between massive galaxy clusters I. The incidence of HI and OVI as WHIM tracers
Karen Martínez-Acosta, Nicolas Tejos, Ismael Pessa et al. (+6 more)
At
redshift z<1, the $\Lambda$CDM paradigm predicts that $\sim$40-50% of baryons reside in the warm-hot intergalactic medium (WHIM) within
cosmic web filaments. Characterizing the physical state and distribution of this dominant baryonic component is crucial for a complete picture of baryon
evolution in the low-
redshift Universe. However, directly observing the WHIM has been challenging due to its low density and high temperature and ionization state. Absorption-line spectroscopy offers a promising approach, particularly through analyses of broad Ly-$\alpha$ absorbers (BLAs; Doppler parameter b>40 km/s) and OVI absorbers. This work focuses on probing WHIM signatures by analyzing the incidence rates of these tracers in and around putative
cosmic web filaments connecting massive
galaxy clusters. We use far-ultraviolet (FUV) absorption spectroscopy from HST/COS along ten QSO sightlines at z<1, selected for their proximity in projected distance and velocity to cluster pairs. We focus on absorption features of WHIM tracers (BLAs and OVI) and cold-gas tracers (narrow Ly-$\alpha$ absorbers, or NLAs; b<40 km/s), which are used as a control sample for colder gas. We measure excess incidence rates for total HI, NLAs, BLAs, and OVI within a rest-frame $\Delta v=\pm1000$ km/s and an impact parameter $\Delta d<3$ Mpc relative to the field expectation, and find that the excesses of BLAs and OVI are about twice those of NLAs. Additionally, the covering fractions of BLAs and OVI appear larger by factors of $\sim$1.7 and 1.8, respectively, than in a random field control sample, whereas the NLA covering fraction is consistent with the random expectation. The larger relative excess of WHIM tracers compared to cold-gas tracers near independent cluster pairs indicates the prevalence of warm-hot gas in these environments, representing a potential signature of WHIM detection in inter-cluster filaments.
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All authors Karen Martínez-Acosta, Nicolas Tejos, Ismael Pessa, J Xavier Prochaska, Joseph Burchett, Britton Smith, Jessica Werk, Nelson Padilla, Sebastián López
Cosmology and Nongalactic Astrophysics · Cross-listed from hep-ph
Implications of tachyonic phase transition in classically scale invariant general $U(1)_{X}$ models
Arindam Das, Katsuya Hashino, Yuta Orikasa et al. (+1 more)
We investigate the complementarity between
collider searches and gravitational-wave (GW) observations in the classically scale-invariant general $U(1)_X$ extension of the Standard Model. The $U(1)_X$ scale is generated radiatively through the Coleman-Weinberg mechanism, while the electroweak scale is induced through the
Higgs portal, without explicit mass terms in the scalar potential. Three right-handed
neutrinos are introduced to ensure anomaly cancellation and acquire Majorana masses upon $U(1)_X$
symmetry breaking, which also generates the mass of the neutral gauge
boson $Z'$. In the strongly supercooled regime, a tachyonic $U(1)_X$ phase transition can produce a
stochastic GW background. Assuming three heavy Majorana
neutrinos, we study their effects on the phase-transition dynamics and reheating, and estimate the resulting GW signals. We identify the regions of the $U(1)_X$ gauge coupling and $Z'$ mass accessible to future GW observatories, including LISA and DECIGO, and compare them with existing LEP and LHC constraints. We find that GWs from tachyonic phase transitions can probe regions with small gauge couplings and heavy $Z'$
bosons that are difficult to access through
collider searches, demonstrating the complementarity of these probes.
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All authors Arindam Das, Katsuya Hashino, Yuta Orikasa, Masanori Tanaka
Cosmology and Nongalactic Astrophysics
Galaxy Clustering Can Reveal Host-Galaxy Properties of Binary Black Hole Mergers
Daiki Watarai, Hayato Imafuku and Fumihiro Chuman
Galaxy clustering encodes information about the host
galaxies of binary black hole (BBH) mergers even when individual hosts remain unidentified, because the distribution of neighboring
galaxies depends statistically on the host-
galaxy population. We construct event-level host-type likelihoods from host-conditioned
galaxy-count distributions within gravitational-wave localization regions and combine them to infer the fractions of BBH mergers hosted by different
galaxy populations. The framework applies to common and rare
galaxy populations without prescribing formation efficiencies or merger delay-time distributions. Using measured
star-forming and quenched
galaxy clustering, idealized one-year forecasts assuming all mergers occur in quenched
galaxies yield median one-sided 90% lower credible limits of 0.19, 0.48, and 0.92 on the quenched-host fraction for O5, post-O5, and third-generation networks. These forecasts illustrate the potential for host-
galaxy population inference before the third-generation detector era.
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