The clustering of C IV and Si IV at the end of reionisation: A perspective from the E-XQR-30 survey
arXiv:2509.03585v1 Announce Type: new
Abstract: We aim to study the clustering of metal absorption lines and the structures that they arise in as a function of cosmic time. We focus on C IV and Si IV absorption features that are identified along a given quasar sightline. We exploit the two-point correlation function (2PCF) to investigate the clustering of these structures as a function of their separation. We utilise the E-XQR-30 data to perform a novel analysis at z>5. We also draw on literature surveys (including XQ-100) of lower redshift quasars to investigate the possible evolution of this clustering towards cosmic noon (i.e., z~2-3). We find no significant evolution with redshift when considering the separation of absorbers in velocity space. Since we are comparing data across a large interval of cosmic time, we also consider the separation between absorbers in the reference frame of physical distances. In this reference frame, we find that the amplitude of the clustering increases with cosmic time for both C IV and Si IV on the scales of <1500 physical kpc. For the first time, we assess the 2PCF of C IV and Si IV close to the epoch of reionisation utilising the absorber catalogue from the E-XQR-30 survey. We compare this with lower redshift data and find that, on small scales, the clustering of these structures grows with cosmic time. We compare these results to the clustering of galaxies in the GAEA simulations. It appears that the structures traced by C IV are broadly comparable to the galaxies from the considered simulations. The clustering is most similar to that of the galaxies with virial masses M~10^10.5 M_sun. We require tailor-made simulations to investigate the full range of factors contributing to the observed clustering. Future ground-based spectrographs will further facilitate surveys of absorbers at this epoch with increased sensitivity.
Was a blob of dark matter spotted in the Milky Way?
Science, Volume 389, Issue 6764, Page 962-963, September 2025.
Improving cosmological reach of a gravitational wave observatory using Deep Loop Shaping
Science, Volume 389, Issue 6764, Page 1012-1015, September 2025.
Should it be space-time or spacetime – and why does it matter anyway?
Seeking endorsements for her new book, Chanda Prescod-Weinstein finds herself staring at fundamental questions of space, time – and grammar
Comparison of Halo Model and Simulation Predictions for Projected-Field Kinematic Sunyaev-Zel'dovich Cross-Correlations
arXiv:2509.03458v1 Announce Type: new
Abstract: The kinematic Sunyaev-Zel'dovich (kSZ) effect in the cosmic microwave background (CMB) is a powerful probe of gas physics and large-scale structure (LSS) in our universe. We consider the "projected-field" kSZ estimator, which involves cross-correlating a foreground-cleaned, filtered, squared CMB temperature map with an LSS tracer, and requires no individual tracer redshifts. We compare $\verb|class_sz|$ halo model calculations of projected-field kSZ cross-correlations with measurements of these signals from the Websky numerical simulations. We cross-correlate halo density maps from Websky with various CMB secondary signals. We first validate our halo model by comparing its predictions for thermal SZ (tSZ) and patchy screening ($\tau$) cross-correlations to measurements of these signals from Websky. We consider three different halo redshift ranges in our comparisons. We also construct our own kSZ, tSZ, and $\tau$ maps to validate the form of the relevant profiles. Following the tSZ and $\tau$ validation, we compare projected-field kSZ calculations between the halo model and the simulations. We use filters constructed for $\textit{Planck}$ and the Simons Observatory (SO) to assess the accuracy of the halo-model kSZ predictions for experiments of differing sensitivity. Overall, we find good agreement, particularly at $\textit{Planck}$ sensitivity. However, we find an $\approx$ 20$\%$ difference between our halo model and the simulations for SO, which significantly exceeds the predicted error bars. We note that our halo model includes only the dominant expected term in the projected-field kSZ signal; the magnitude of the difference between our model and the simulations is consistent with previous predictions for terms arising from other contractions in the theory calculation. These terms will need to be included to obtain unbiased inference from upcoming projected-field kSZ measurements.
GRB 250704B: An Off-axis Short GRB with a Long-Lived Afterglow Plateau
arXiv:2509.02769v1 Announce Type: new
Abstract: We present a detailed multi-wavelength afterglow study of the short GRB 250704B, extensively monitored in optical and near-infrared bands. Its afterglow displays an unusually long-duration plateau followed by an achromatic break and a steep decline, deviating from canonical GRB afterglows. While long plateaus are often explained by central engine activity, we find that for GRB 250704B, an energy injection model requires unreasonable parameters. The afterglow is better explained by an off-axis power-law structured jet with a narrow core ($\theta_c \approx 0.7^{\circ}$) viewed at a modest angle ($\theta_v \approx 1.9^{\circ}$). A comparison with GRB 170817A shows that both events are consistent with the off-axis structured jet scenario, where the shape of the light curve is governed primarily by the geometry of the jet and the viewing angle rather than the energetics, microphysical parameters, or external density. Our results underscore the importance of incorporating the jet structure in GRB modeling.
Euclid Quick Data Release (Q1). First detections from the galaxy cluster workflow
arXiv:2503.19196v2 Announce Type: replace
Abstract: The first survey data release by the Euclid mission covers approximately $63\,\mathrm{deg^2}$ in the Euclid Deep Fields to the same depth as the Euclid Wide Survey. This paper showcases, for the first time, the performance of cluster finders on Euclid data and presents examples of validated clusters in the Quick Release 1 (Q1) imaging data. We identify clusters using two algorithms (AMICO and PZWav) implemented in the Euclid cluster-detection pipeline. We explore the internal consistency of detections from the two codes, and cross-match detections with known clusters from other surveys using external multi-wavelength and spectroscopic data sets. This enables assessment of the Euclid photometric redshift accuracy and also of systematics such as mis-centring between the optical cluster centre and centres based on X-ray and/or Sunyaev--Zeldovich observations. We report 426 joint PZWav and AMICO-detected clusters with high signal-to-noise ratios over the full Q1 area in the redshift range $0.2 \leq z \leq 1.5$. The chosen redshift and signal-to-noise thresholds are motivated by the photometric quality of the early Euclid data. We provide richness estimates for each of the Euclid-detected clusters and show its correlation with various external cluster mass proxies. Out of the full sample, 77 systems are potentially new to the literature. Overall, the Q1 cluster catalogue demonstrates a successful validation of the workflow ahead of the Euclid Data Release 1, based on the consistency of internal and external properties of Euclid-detected clusters.
Inferring the pair-instability mass gap from gravitational wave data
arXiv:2506.09154v2 Announce Type: replace
Abstract: We use hierarchical Bayesian inference with non-parametric Gaussian process models to investigate the effective inspiral spin parameter, $\chi_{\rm eff}$, as a function of primary black hole mass in the third gravitational-wave transient catalog (GWTC-3). Our analysis reveals a transition in the population at a primary mass of $46^{+7}_{-5}\,M_\odot$. Beyond this mass, the $\chi_{\rm eff}$ distribution broadens, becomes consistent with being symmetric around zero, and has a median of $-0.03^{+0.36}_{-0.59}$ (90\% credibility). These results are consistent with the presence of a pair-instability mass gap that is repopulated by black holes that are the remnant of a previous merger, formed in dense star clusters. However, asymmetric distributions skewed toward positive $\chi_{\rm eff}$ are not excluded by current data. Below the inferred transition mass, we constrain the fraction of second-generation black holes to be $\lesssim 10\%$. These results provide model-independent support for a high-mass and high-spin population of black holes in the data, consistent with earlier work using parametric models. Imminent gravitational-wave data releases will be essential to sharpen constraints on spin symmetry and clarify the origin of the black holes.
Premature supermassive black hole mergers in cosmological simulations of structure formation
arXiv:2504.17549v2 Announce Type: replace
Abstract: The co-evolution of massive black holes (BHs) and their host galaxies is well-established within the hierarchical galaxy formation paradigm. Large-scale cosmological simulations are an ideal tool to study the repeated BH mergers, accretion and feedback that conspire to regulate this process. While such simulations are of fundamental importance for understanding the complex and intertwined relationship between BHs and their hosts, they are plagued with numerical inaccuracies at the scale of individual BH orbits. To quantify this issue, taking advantage of the $(100 \, h^{-1}\,\text{cMpc})^3$ FABLE simulation box, we track all individual BH mergers and the corresponding host galaxy mergers as a function of cosmic time. We demonstrate that BH mergers frequently occur prematurely, well before the corresponding merger of the host galaxies is complete, and that BHs are sometimes erroneously displaced from their hosts during close galaxy encounters. Correcting for these artefacts results in substantial macrophysical delays, spanning over several Gyrs, which are additional to any microphysical delays arising from unresolved BH binary hardening processes. We find that once the macrophysical delays are accounted for, high-mass BH merger events are suppressed, affecting the predictions for the BH population that may be observable with LISA and pulsar timing arrays. Furthermore, including these macrophysical delays leads to an increase in the number of observable dual active galactic nuclei, especially at lower redshifts, with respect to FABLE. Our results highlight the pressing need for more accurate modelling of BH dynamics in cosmological simulations of galaxy formation as we prepare for the multi-messenger era.
Quasar Radiative Feedback May Suppress Galaxy Growth on Intergalactic Scales at $z = 6.3$
arXiv:2509.00153v1 Announce Type: new
Abstract: We present observational evidence that intense ionizing radiation from a luminous quasar suppresses nebular emission in nearby galaxies on intergalactic scales at $z=6.3$. Using JWST/NIRCam grism spectroscopy from the SAPPHIRES and EIGER programs, we identify a pronounced decline in [O III] $\lambda5008$ luminosity relative to the UV continuum ($L_{5008}/L_{1500}$) among galaxies within $\sim$10 comoving Mpc (cMpc) of the quasar J0100$+$2802, the most UV-luminous quasar known at this epoch ($M_{1450}=-29.26$). While $L_{1500}$ remains roughly constant with transverse distance, $L_{5008}$ increases significantly, suggesting suppression of very recent star formation toward the quasar. The effect persists after controlling for completeness, local density, and UV luminosity, and correlates with the projected photoionization-rate profile $\Gamma_{\mathrm{qso}}$. A weaker but directionally consistent suppression in $L_{5008}/L_{1500}$ is also observed along the line of sight. The transverse suppression radius ($\sim$8-10 cMpc) implies a recent radiative episode with a cumulative duration $\sim$4.5 Myr, shorter than required for thermal photoheating to dominate and thus more naturally explained by rapid H$_2$ photodissociation and related radiative processes. Environmental effects alone appear insufficient to explain the signal. Our results provide direct, geometry-based constraints on large-scale quasar radiative feedback and recent quasar lifetimes.
Unifiying gravity and quantum theory requires better understanding of time
Nature, Published online: 02 September 2025; doi:10.1038/d41586-025-02756-8
Textbooks give strange, imprecise explanations of where things happen in quantum mechanics. Consistency with gravity needs a fresh approach.Fri 26 Sep 11:30: The curious case of metal-poor DLAs at cosmic noon
The curious case of metal-poor DLAs at cosmic noon
Abstract not available
- Speaker: Louise Welsh (Durham)
- Friday 26 September 2025, 11:30-12:30
- Venue: Ryle Seminar Room, KICC + online.
- Series: Galaxies Discussion Group; organiser: Sandro Tacchella.
A direct black hole mass measurement in a Little Red Dot at the Epoch of Reionization
arXiv:2508.21748v1 Announce Type: new
Abstract: Recent discoveries of faint active galactic nuclei (AGN) at the redshift frontier have revealed a plethora of broad \Halpha emitters with optically red continua, named Little Red Dots (LRDs), which comprise 15-30\% of the high redshift broad line AGN population. Due to their peculiar spectral properties and X-ray weakness, modeling LRDs with standard AGN templates has proven challenging. In particular, the validity of single-epoch virial mass estimates in determining the black hole (BH) masses of LRDs has been called into question, with some models claiming that masses might be overestimated by up to 2 orders of magnitude, and other models claiming that LRDs may be entirely stellar in nature. We report the direct, dynamical BH mass measurement in a strongly lensed LRD at $z = 7.04$. The combination of lensing with deep spectroscopic data reveals a rotation curve that is inconsistent with a nuclear star cluster, yet can be well explained by Keplerian rotation around a point mass of 50 million Solar masses, consistent with virial BH mass estimates from the Balmer lines. The Keplerian rotation leaves little room for any stellar component in a host galaxy, as we conservatively infer $M_{\rm BH}/M_{*}>2$. Such a ''naked'' black hole, together with its near-pristine environment, indicates that this LRD is a massive black hole seed caught in its earliest accretion phase.
JWST Spectroscopic Insights Into the Diversity of Galaxies in the First 500 Myr: Short-Lived Snapshots Along a Common Evolutionary Pathway
arXiv:2508.21708v1 Announce Type: new
Abstract: We investigate the nature and spectroscopic diversity of early galaxies from a sample of 40 sources at z>10 with JWST/NIRSpec prism observations, the largest of its kind thus far. We compare the properties of strong UV line emitters, as traced by intense CIV emission, with those of more "typical" sources with weak or undetected CIV. The more typical (or "CIV-weak") sources reveal significant scatter in their CIII] line strengths, UV continuum slopes, and physical sizes, spanning CIII] equivalent widths of ~1-51 \r{A}, UV slopes of $\beta$~-1.6 to -2.6, and half-light radii of ~50-1000 pc. In contrast, CIV-strong sources generally occupy the tail of these distributions, with CIII] EWs of 16-51 \r{A}, UV slopes $\beta$<-2.5, compact morphologies ($r_{50}$<100 pc), and elevated star formation surface densities ($\Sigma_{SFR}$>100 $M_{\odot}yr^{-1}kpc^{-2}$). Collectively these properties are consistent with concentrated starbursts that temporarily outshine the extended structure of the galaxy. Comparing average properties from composite spectra, we find the diversity of the sample is primarily driven by bursts and lulls of star formation on very short timescales (<3 Myr), where strong CIV emitters are observed at the apex of these phases and sources devoid of emission lines represent periods of relative inactivity. An apparent association between strong CIV and enhanced nitrogen abundance suggests both features may be modulated by the same duty cycle and reflect a generic mode of star formation. We show that AGN are unlikely to be a significant contributor to this duty cycle based on a comparison of UV line diagnostics to photoionisation models, although some non-thermal activity cannot be fully ruled out. Our results support a unified evolutionary picture whereby transient bursts and lulls can explain the spectral diversity and early growth of bright galaxies in the first 500 Myr.
The Science of the Einstein Telescope
arXiv:2503.12263v2 Announce Type: replace-cross
Abstract: Einstein Telescope (ET) is the European project for a gravitational-wave (GW) observatory of third-generation. In this paper we present a comprehensive discussion of its science objectives, providing state-of-the-art predictions for the capabilities of ET in both geometries currently under consideration, a single-site triangular configuration or two L-shaped detectors. We discuss the impact that ET will have on domains as broad and diverse as fundamental physics, cosmology, early Universe, astrophysics of compact objects, physics of matter in extreme conditions, and dynamics of stellar collapse. We discuss how the study of extreme astrophysical events will be enhanced by multi-messenger observations. We highlight the ET synergies with ground-based and space-borne GW observatories, including multi-band investigations of the same sources, improved parameter estimation, and complementary information on astrophysical or cosmological mechanisms obtained combining observations from different frequency bands. We present advancements in waveform modeling dedicated to third-generation observatories, along with open tools developed within the ET Collaboration for assessing the scientific potentials of different detector configurations. We finally discuss the data analysis challenges posed by third-generation observatories, which will enable access to large populations of sources and provide unprecedented precision.
How does feedback affect the star formation histories of galaxies?
arXiv:2508.21152v1 Announce Type: new
Abstract: Star formation in galaxies is regulated by the interplay of a range of processes that shape the multiphase gas in the interstellar and circumgalactic media. Using the CAMELS suite of cosmological simulations, we study the effects of varying feedback and cosmology on the average star formation histories (SFHs) of galaxies at $z\sim0$ across the IllustrisTNG, SIMBA and ASTRID galaxy formation models. We find that galaxy SFHs in all three models are sensitive to changes in stellar feedback, which affects the efficiency of baryon cycling and the rates at which central black holes grow, while effects of varying AGN feedback depend on model-dependent implementations of black hole seeding, accretion and feedback. We also find strong interaction terms that couple stellar and AGN feedback, usually by regulating the amount of gas available for the central black hole to accrete. Using a double power-law to describe the average SFHs, we derive a general set of equations relating the shape of the SFHs to physical quantities like baryon fraction and black hole mass across all three models. We find that a single set of equations (albeit with different coefficients) can describe the SFHs across all three CAMELS models, with cosmology dominating the SFH at early times, followed by halo accretion, and feedback and baryon cycling at late times. Galaxy SFHs provide a novel, complementary probe to constrain cosmology and feedback, and can connect the observational constraints from current and upcoming galaxy surveys with the physical mechanisms responsible for regulating galaxy growth and quenching.
The Atacama Cosmology Telescope: DR6 Sunyaev-Zel'dovich Selected Galaxy Clusters Catalog
arXiv:2507.21459v2 Announce Type: replace
Abstract: We present the results of a search for galaxy clusters in the Atacama Cosmology Telescope (ACT) Data Release 6 (DR6) microwave sky maps covering 16293 square degrees in three frequency bands, using data obtained over the lifetime of the project (2008-2022). We report redshifts and mass estimates for 10040 clusters detected via their Sunyaev-Zel'dovich (SZ) effect with signal-to-noise greater than 4 at a 2.4 arcminute filter scale. The catalog includes 1171 clusters at redshifts greater than 1, and 123 clusters at redshifts greater than 1.5. Using a relation between cluster SZ signal and mass that is consistent with recent weak-lensing measurements, we estimate that clusters detected with signal-to-noise greater than 5 form a sample which is 90% complete for clusters with masses greater than $5 \times 10^{14}$ MSun (measured within a spherical volume with mean density 500 times the critical density). El Gordo, a cluster found in an initial ACT survey of 755 square degrees, remains the most extreme cluster in mass and redshift; we find no cluster with a mass and redshift combination high enough to falsify the standard LCDM cosmology with Gaussian initial perturbations. We make public a variety of data products, including the full cluster candidate list, noise maps, and sky masks, along with our software for cluster detection and instructions for reproducing our cluster catalogs from the public ACT maps.
Fri 24 Oct 11:30: Learning galaxy properties with machine learning and simulation based inference
Learning galaxy properties with machine learning and simulation based inference
Abstract not available
- Speaker: Michele Ginolfi (Florence)
- Friday 24 October 2025, 11:30-12:30
- Venue: Ryle Seminar Room, KICC + online.
- Series: Galaxies Discussion Group; organiser: Sandro Tacchella.
Constraints on Primordial Magnetic Fields from the Lyman-{\alpha} forest
arXiv:2501.06299v2 Announce Type: replace
Abstract: We present the first constraints on primordial magnetic fields from the Lyman-$\alpha$ forest using full cosmological hydrodynamic simulations. At the scales and redshifts probed by the data, the flux power spectrum is extremely sensitive to the extra power induced by primordial magnetic fields in the linear matter power spectrum, at a scale that we parametrize with $k_{\rm peak}$. We rely on a set of more than a quarter million flux models obtained by varying thermal, reionization histories and cosmological parameters. We find a hint of extra power that is well fitted by the PMF model with $B\sim 0.2$ nG, corresponding to $k_{\rm peak}\sim 20$ Mpc$^{-1}$. However, when applying very conservative assumptions on the modelling of the noise, we obtain a 3$\sigma$ C.L. lower limit $k_{\rm peak}> 30$ Mpc$^{-1}$ which translates into the tightest bounds on the strength of primordial intergalactic magnetic fields: $B < 0.30$ nG (for fixed, nearly scale-invariant $n_{\rm B}=-2.9$).
Constraining Mixed Dark Matter models with high redshift Lyman-alpha forest data
arXiv:2504.06367v2 Announce Type: replace
Abstract: This study sets new constraints on Cold+Warm Dark Matter (CWDM) models by leveraging the small-scale suppression of structure formation imprinted in the Lyman-$\alpha$ forest. Using the Sherwood-Relics suite, we extract high-fidelity flux power spectra from simulated Lyman-$\alpha$ forest data, spanning a broad range of cosmologies and thermal histories. This enables precise constraints on the warm dark matter (WDM) fraction, $f_{\mathrm{WDM}}$, and the mass of the WDM particle, $m_{\mathrm{WDM}}$. A key advancement of our analysis is the integration of a neural network emulator directly at the likelihood level, significantly accelerating Bayesian parameter inference. With new observations of high-redshift ($z$ = 4.2$-$5.0) quasar spectra from UVES and HIRES, we establish stringent upper limits: for $m_{\mathrm{WDM}}$ = 1 keV, we find $f_{\mathrm{WDM}} < 0.16$ (2$\sigma$), with constraints loosening to 35\%, 50\%, and 67\% for $m_{\mathrm{WDM}}$ = 2, 3, and 4 keV, respectively. Our results for pure WDM reaffirm the lower bounds of previous work. Crucially, we account for the fixed resolution of simulations and the impact of patchy reionization, demonstrating their minimal influence on mixed dark matter constraints. This robustness paves the way for tighter bounds with improved statistical samples in the future. Our findings suggest that CWDM models can naturally accommodate mild suppression of matter clustering in the high redshift Lyman-$\alpha$ forest 1D flux power, potentially offering a resolution to some of the ongoing cosmological tensions at low redshifts, namely the $S_{8}$ tension.
