arXiv subjects

E. Maiorano

Publications and source records attributed to E. Maiorano.

At least 55 records · Page 3Linked to original sources

arXiv2025

Discovery and Analysis of Afterglows from Poorly Localised GRBs with the Gravitational-wave Optical Transient Observer (GOTO) All-sky Survey

Gamma-ray bursts (GRBs), particularly those detected by wide-field instruments such as the Fermi/GBM, pose a challenge for optical follow-up due to their large initial localisation regions, leaving many GRBs without identified afterglows. The Gravitational-wave Optical Transient Observer (GOTO), with its wide field of view, dual-site coverage, and robotic rapid-response capability, bridges this gap by rapidly identifying and localising afterglows from alerts issued by space-based facilities, including Fermi, SVOM, Swift, and EP, providing early optical positions for coordinated multiwavelength follow-up. In this paper, we present optical afterglow localisation and multiband follow-up of five Fermi/GBM (240619A, 240910A, 240916A, 241002B, and 241228B) and two MAXI/GSC (240122A and 240225B) triggered long GRBs (LGRBs) discovered by GOTO in 2024. Spectroscopy for six GRBs (no spectroscopic data for GRB 241002B) with VLT/X-shooter and GTC/OSIRIS yields precise redshifts spanning $z\approx0.40-$3.16 and absorption-line diagnostics of host and intervening systems. Radio detections for four events confirm the presence of long-lived synchrotron emission. Prompt-emission analysis with Fermi and MAXI data reveals a spectrally hard population, with two bursts lying $>3σ$ above the Amati relation. Although their optical afterglows resemble those of typical LGRBs, the prompt spectra are consistently harder than the LGRBs' average. Consistent modelling of six GOTO-discovered GRB afterglows yields jet half-opening angles of a few degrees and beaming-corrected kinetic energies ($E_{jet}\sim10^{51-52}$)erg, consistent with the canonical LGRB population. These findings suggest that optical discovery of poorly localised GRBs may be subject to observational biases favouring luminous events with high spectral peak energy, while also providing insight into jet microphysics and central engine diversity.

astro-ph.HE↗

arXiv2025

Euclid: Quick Data Release (Q1)- The connection between galaxy close encounters and radio activity

Using the large statistics provided by both Euclid and the LOFAR surveys, we present the first large-scale study of the connection between radio emission, its morphology, and the merging properties of the hosts of radio sources up to z=2. By dividing the radio sample into active galactic nuclei (AGN) and star-forming galaxies, we find that radio-emitting AGN show a clear preference to reside within galaxies undergoing a merging event. This is more significant for AGN that present extended and/or complex radio emission: indeed, about half of them are associated with merging systems, while only 15% are hosted by an isolated galaxy. The observed trend is primarily driven by AGN residing at z < 1, especially in the case of high - P144MHz > 10^24 W Hz-1 sr-1 - radio luminosities (60% in mergers versus 10% isolated regardless of radio appearance). The situation is reversed in the case of radio-emitting star-forming galaxies, which are preferentially associated with isolated systems. This is more significant as we move towards low radio-luminosity/star-formation objects (P144MHz < 10^23 W Hz-1 sr-1) for which we find 40% in isolated systems versus 20% in mergers. These values hold regardless of redshift. We interpret the above result for AGN with their need to accrete outer gas from local encounters in order to trigger (radio) activity, especially in the case of extended radio emission such as hot-spots and lobes. This is mostly observed at z < 1, since in the local Universe galaxies are more gas deprived than their higher-redshift counterparts. Internal gas reservoirs instead seem sufficient to trigger star formation within the majority of galaxies, which indeed prefer to be associated with isolated systems at all redshifts probed. (abridged)

astro-ph.GA↗

arXiv2025

Euclid: Quick Data Release (Q1) -- Secondary nuclei in early-type galaxies

Massive early-type galaxies (ETGs) are believed to form primarily through mergers of less massive progenitors, leaving behind numerous traces of violent formation histories, such as stellar streams and shells. A particularly striking signature of these mergers is the formation of supermassive black hole (SMBH) binaries, which can create depleted stellar cores through interactions with stars on radial orbits - a process known as core scouring. The secondary SMBH in such systems may still carry a dense stellar envelope and thereby remain observable for some time as a secondary nucleus, while it is sinking towards the shared gravitational potential of the merged galaxy. We leverage Euclid's Q1 Early Release data to systematically search for secondary nuclei in ETGs. We present a preliminary sample of 666 candidate systems distributed over 504 hosts (some of which contain multiple secondary nuclei). The vast majority of these fall at separations of 3 kpc to 15 kpc, indicative of normal mergers. 44 fall at projected separations of less than 2 kpc. We argue those candidates at very close angular separations are unlikely to be a consequence of chance alignments. We show that their stellar masses are mostly too large for them to be globular clusters and that a significant subset are unresolved even at Euclid's spatial resolution, rendering them too small to be dwarf galaxies. These may represent the highest-density nuclei of a previously merged galaxy, currently sinking into the centre of the new, common gravitational potential and thus likely to host a secondary SMBH. We then demonstrate that convolutional neural networks offer a viable avenue to detect multiple nuclei in the thirty-times larger sky coverage of the future Euclid DR1. Finally, we argue that our method could detect the remnants of a recoil event from two merged SMBHs.

astro-ph.GA↗

arXiv2025

Euclid Quick Data Release (Q1). Spectroscopic unveiling of highly ionised lines at z = 2.48-3.88

This study explores a rare population of sources in a currently uncharted region of spectroscopic redshift space in the Euclid Quick Data Release (Q1), and is intended potentially to support upcoming spectroscopic studies. Our goal is to identify and investigate a population of sources characterised by highly ionised emission lines in their spectra, which are indicative of active galactic nucleus activity, extreme shock phenomena, or Wolf--Rayet stars. A comprehensive visual inspection of spectra is conducted to ensure the reliability of the sample, focusing on the simultaneous detection of both NeV and OII emission-line measurements, a condition that restricts the Euclid spectroscopic redshift range to z=2.48--3.88. To characterise this population, we analysed the morpho-spectrophotometric properties of their host galaxies. This allowed for a direct comparison with control sources that exhibit similar OII properties and spectroscopic redshifts, but not NeV lines. We identify sources solely based on spectroscopic criteria in the redshift range beyond the Halpha regime. Encompassing 65 potential NeV candidates, the resulting sample delivers the first systematic probe of these NeV candidate emitters at high redshift. We found a good agreement, within 1$σ$, between the spectral measurements calculated using both direct integration and Gaussian fitting methodologies. The NeV candidates exhibit colours similar to bright QSOs, with only a few in the tail of very red quasars. We observed a higher stellar mass content, a lower continuum around the 4000A break, and a similar Sérsic index distribution compared to the control sample. This unique sample paves the way for a wide range of scientific investigations, which will be pursued in the forthcoming data releases.

astro-ph.GA↗

arXiv2025

Euclid preparation: The flat-sky approximation for the clustering of Euclid's photometric galaxies

We compare the performance of the flat-sky approximation and Limber approximation for the clustering analysis of the photometric galaxy catalogue of Euclid. We study a 6 bin configuration representing the first data release (DR1) and a 13 bin configuration representative of the third and final data release (DR3). We find that the Limber approximation is sufficiently accurate for the analysis of the wide bins of DR1. Contrarily, the 13 bins of DR3 cannot be modelled accurately with the Limber approximation. Instead, the flat-sky approximation is accurate to below $5\%$ in recovering the angular power spectra of galaxy number counts in both cases and can be used to simplify the computation of the full power spectrum in harmonic space for the data analysis of DR3.

astro-ph.CO↗

arXiv2025

Euclid Quick Data Release (Q1). Active galactic nuclei identification using diffusion-based inpainting of Euclid VIS images

Light emission from galaxies exhibit diverse brightness profiles, influenced by factors such as galaxy type, structural features and interactions with other galaxies. Elliptical galaxies feature more uniform light distributions, while spiral and irregular galaxies have complex, varied light profiles due to their structural heterogeneity and star-forming activity. In addition, galaxies with an active galactic nucleus (AGN) feature intense, concentrated emission from gas accretion around supermassive black holes, superimposed on regular galactic light, while quasi-stellar objects (QSO) are the extreme case of the AGN emission dominating the galaxy. The challenge of identifying AGN and QSO has been discussed many times in the literature, often requiring multi-wavelength observations. This paper introduces a novel approach to identify AGN and QSO from a single image. Diffusion models have been recently developed in the machine-learning literature to generate realistic-looking images of everyday objects. Utilising the spatial resolving power of the Euclid VIS images, we created a diffusion model trained on one million sources, without using any source pre-selection or labels. The model learns to reconstruct light distributions of normal galaxies, since the population is dominated by them. We condition the prediction of the central light distribution by masking the central few pixels of each source and reconstruct the light according to the diffusion model. We further use this prediction to identify sources that deviate from this profile by examining the reconstruction error of the few central pixels regenerated in each source's core. Our approach, solely using VIS imaging, features high completeness compared to traditional methods of AGN and QSO selection, including optical, near-infrared, mid-infrared, and X-rays.

astro-ph.GA↗

arXiv2025

Euclid: Exploring observational systematics in cluster cosmology -- a comprehensive analysis of cluster counts and clustering

This study explores the impact of observational and modelling systematic effects on cluster number counts and cluster clustering and provides model prescriptions for their joint analysis, in the context of the \Euclid survey. Using 1000 \Euclid-like cluster catalogues, we investigate the effect of systematic uncertainties on cluster summary statistics and their auto- and cross-covariance, and perform a likelihood analysis to evaluate their impact on cosmological constraints, with a focus on the matter density parameter $Ω_{\rm m}$ and on the power spectrum amplitude $σ_8$. Combining cluster clustering with number counts significantly improves cosmological constraints, with the figure of merit increasing by over 300\% compared to number counts alone. We confirm that the two probes are uncorrelated, and the cosmological constraints derived from their combination are almost insensitive to the cosmology dependence of the covariance. We find that photometric redshift uncertainties broaden cosmological posteriors by 20--30\%, while secondary effects like redshift-space distortions (RSDs) have a smaller impact on the posteriors -- 5\% for clustering alone, 10\% when combining probes -- but can significantly bias the constraints if neglected. We show that clustering data below $60\,h^{-1}\,$Mpc provides additional constraining power, while scales larger than acoustic oscillation scale add almost no information on $Ω_{\rm m}$ and $σ_8$ parameters. RSDs and photo-$z$ uncertainties also influence the number count covariance, with a significant impact, of about 15--20\%, on the parameter constraints.

astro-ph.CO↗

arXiv2025

Euclid preparation. XLI. Galaxy power spectrum modelling in real space

We investigate the accuracy of the perturbative galaxy bias expansion in view of the forthcoming analysis of the Euclid spectroscopic galaxy samples. We compare the performance of an Eulerian galaxy bias expansion, using state-of-art prescriptions from the effective field theory of large-scale structure (EFTofLSS), against a hybrid approach based on Lagrangian perturbation theory and high-resolution simulations. These models are benchmarked against comoving snapshots of the Flagship I N-body simulation at $z=(0.9,1.2,1.5,1.8)$, which have been populated with H$α$ galaxies leading to catalogues of millions of objects within a volume of about $58\,h^{-3}\,{\rm Gpc}^3$. Our analysis suggests that both models can be used to provide a robust inference of the parameters $(h, ω_{\rm c})$ in the redshift range under consideration, with comparable constraining power. We additionally determine the range of validity of the EFTofLSS model in terms of scale cuts and model degrees of freedom. From these tests, it emerges that the standard third-order Eulerian bias expansion can accurately describe the full shape of the real-space galaxy power spectrum up to the maximum wavenumber $k_{\rm max}=0.45\,h\,{\rm Mpc}^{-1}$, even with a measurement precision well below the percent level. In particular, this is true for a configuration with six free nuisance parameters, including local and non-local bias parameters, a matter counterterm, and a correction to the shot-noise contribution. Fixing either tidal bias parameters to physically-motivated relations still leads to unbiased cosmological constraints. We finally repeat our analysis assuming a volume that matches the expected footprint of Euclid, but without considering observational effects, as purity and completeness, showing that we can get consistent cosmological constraints over this range of scales and redshifts.

astro-ph.CO↗

arXiv2025

Euclid: Methodology for derivation of IPC-corrected conversion gain of nonlinear CMOS APS

We introduce a fast method to measure the conversion gain in Complementary Metal-Oxide-Semiconductors (CMOS) Active Pixel Sensors (APS), which accounts for nonlinearity and interpixel capacitance (IPC). The standard 'mean-variance' method is biased because it assumes pixel values depend linearly on signal, and existing methods to correct for nonlinearity are still introducing significant biases. While current IPC correction methods are prohibitively slow for a per-pixel application, our new method uses separate measurements of the IPC kernel to make an almost instantaneous calculation of gain. Validated using test data from a flight detector from the ESA Euclid mission, the IPC correction recovers the results of slower methods within 0.1% accuracy. Meanwhile the nonlinearity correction ensures an estimation of the gain that is independent of signal, correcting a bias of more than 2.5% on gain estimation.

physics.ins-det↗

arXiv2025

Euclid: Forecasts on $Λ$CDM consistency tests with growth rate data

The large-scale structure (LSS) of the Universe is an important probe for deviations from the canonical cosmological constant $Λ$ and cold dark matter ($Λ$CDM) model. A statistically significant detection of any deviations would signify the presence of new physics or the breakdown of any number of the underlying assumptions of the standard cosmological model or possible systematic errors in the data. In this paper, we quantify the ability of the LSS data products of the spectroscopic survey of the Euclid mission, together with other contemporary surveys, to improve the constraints on deviations from $Λ$CDM in the redshift range $0<z<1.75$. We consider both currently available growth rate data and simulated data with specifications from Euclid and external surveys, based on $Λ$CDM and a modified gravity (MoG) model with an evolving Newton's constant (denoted $μ$CDM), and carry out a binning method and a machine learning reconstruction, based on genetic algorithms (GAs), of several LSS null tests. Using the forecast Euclid growth data from the spectroscopic survey in the range $0.95<z<1.75$, we find that in combination with external data products (covering the range $0<z<0.95$), Euclid will be able to improve on current constraints of null tests of the LSS on average by a factor of eight when using a binning method and a factor of six when using the GAs. Our work highlights the need for synergies between Euclid and other surveys, but also the usefulness of statistical analyses, such as GAs, in order to disentangle any degeneracies in the cosmological parameters. Both are necessary to provide tight constraints over an extended redshift range and to probe for deviations from the $Λ$CDM model.

astro-ph.CO↗

arXiv2025

Euclid: Early Release Observations of diffuse stellar structures and globular clusters as probes of the mass assembly of galaxies in the Dorado group

Deep surveys reveal tidal debris and associated compact stellar systems. Euclid's unique combination of capabilities (spatial resolution, depth, and wide sky coverage) will make it a groundbreaking tool for galactic archaeology in the local Universe, bringing low surface brightness (LSB) science into the era of large-scale astronomical surveys. Euclid's Early Release Observations (ERO) demonstrate this potential with a field of view that includes several galaxies in the Dorado group. In this paper, we aim to derive from this image a mass assembly scenario for its main galaxies: NGC 1549, NGC 1553, and NGC 1546. We detect internal and external diffuse structures, and identify candidate globular clusters (GCs). By analysing the colours and distributions of the diffuse structures and candidate GCs, we can place constraints on the galaxies' mass assembly and merger histories. The results show that feature morphology, surface brightness, colours, and GC density profiles are consistent with galaxies that have undergone different merger scenarios. We classify NGC 1549 as a pure elliptical galaxy that has undergone a major merger. NGC 1553 appears to have recently transitioned from a late-type galaxy to early type, after a series of radial minor to intermediate mergers. NGC 1546 is a rare specimen of galaxy with an undisturbed disk and a prominent diffuse stellar halo, which we infer has been fed by minor mergers and then disturbed by the tidal effect from NGC 1553. Finally, we identify limitations specific to the observing conditions of this ERO, in particular stray light in the visible and persistence in the near-infrared bands. Once these issues are addressed and the extended emission from LSB objects is preserved by the data-processing pipeline, the Euclid Wide Survey will allow studies of the local Universe to be extended to statistical ensembles over a large part of the extragalactic sky.

astro-ph.GA↗

arXiv2025

Euclid VI. NISP-P optical ghosts

The Near-Infrared Spectrometer and Photometer (NISP) onboard Euclid includes several optical elements in its path, which introduce artefacts into the data from non-nominal light paths. To ensure uncontaminated source photometry, these artefacts must be accurately accounted for. This paper focuses on two specific optical features in NISP's photometric data (NISP-P): ghosts caused by the telescope's dichroic beamsplitter, and the bandpass filters within the NISP fore-optics. Both ghost types exhibit a characteristic morphology and are offset from the originating stars. The offsets are well modelled using 2D polynomials, with only stars brighter than approximately 10 magnitudes in each filter producing significant ghost contributions. The masking radii for these ghosts depend on both the source-star brightness and the filter wavelength, ranging from 20 to 40 pixels. We present the final relations and models used in the near-infrared (NIR) data pipeline to mask these ghosts for Euclid's Quick Data Release (Q1).

astro-ph.IM↗

arXiv2025

Euclid preparation. Full-shape modelling of 2-point and 3-point correlation functions in real space

We investigate the accuracy and range of validity of the perturbative model for the 2-point (2PCF) and 3-point (3PCF) correlation functions in real space in view of the forthcoming analysis of the Euclid mission spectroscopic sample. We take advantage of clustering measurements from four snapshots of the Flagship I N-body simulations at z = {0.9, 1.2, 1.5, 1.8}, which mimic the expected galaxy population in the ideal case of absence of observational effects such as purity and completeness. For the 3PCF we consider all available triangle configurations given a minimal separation. First, we assess the model performance by fixing the cosmological parameters and evaluating the goodness-of-fit provided by the perturbative bias expansion in the joint analysis of the two statistics, finding overall agreement with the data down to separations of 20 Mpc/h. Subsequently, we build on the state-of-the-art and extend the analysis to include the dependence on three cosmological parameters: the amplitude of scalar perturbations As, the matter density ωcdm and the Hubble parameter h. To achieve this goal, we develop an emulator capable of generating fast and robust modelling predictions for the two summary statistics, allowing efficient sampling of the joint likelihood function. We therefore present the first joint full-shape analysis of the real-space 2PCF and 3PCF, testing the consistency and constraining power of the perturbative model across both probes, and assessing its performance in a combined likelihood framework. We explore possible systematic uncertainties induced by the perturbative model at small scales finding an optimal scale cut of rmin = 30 Mpc/h for the 3PCF, when imposing an additional limitation on nearly isosceles triangular configurations included in the data vector. This work is part of a Euclid Preparation series validating theoretical models for galaxy clustering.

astro-ph.CO↗

arXiv2025

Euclid: Quick Data Release (Q1) -- Watching ICM-selected galaxy clusters with Euclid eyes -- prospects of Euclid data in the context of large SZ and X-ray based surveys

Galaxy clusters detected through their X-ray emission or Sunyaev--Zeldovich effect (SZE), both produced by the intra-cluster medium (ICM), are key probes in cosmological and astrophysical studies. To maximise the scientific return of such surveys, complementary data are required for cluster confirmation and redshift estimation. This is typically provided by wide-field optical and infrared surveys, which are increasingly challenged by ongoing and future ICM-selected samples. In particular, at high redshifts ($z>1$) probed by upcoming SZE-selected samples, current large surveys may be insufficient for reliable confirmation. Deep, high-resolution infrared surveys like Euclid will thus be essential for confirming most high-redshift clusters. We present an analysis of the first sizeable Euclid dataset (Q1), overlapping with several ICM-selected cluster samples. We apply an adaptation of the MCMF cluster confirmation tool to estimate key properties, including redshift and richness, and to predict Euclid's capabilities for high-redshift cluster confirmation. We find promising performance, particularly at high redshifts, while richness estimates at low redshifts ($z<0.4$) are currently limited by Q1 data quality but should improve with future releases. Using MCMF runs on random lines of sight, we predict that Euclid will confirm clusters at $1<z<2$ as effectively as current optical surveys at $z<0.6$, significantly enhancing high-redshift confirmation. SZE-selected samples will thus greatly benefit from Euclid overlap. Among five known high-$z$ SZE clusters in Q1, we identify the highest-redshift jellyfish galaxy candidate to date, EUCLJ035330.86$-$504347.6 in SPT-CLJ0353$-$5043 ($z=1.32$), two massive star-forming galaxies near ACT-CLJ0350.0$-$4819 ($z=1.46$), and strong lensing features in SPT-CLJ0353$-$5043 and SPT-CLJ0421$-$4845.

astro-ph.CO↗

arXiv2025

EP 250108a/SN 2025kg: Observations of the most nearby Broad-Line Type Ic Supernova following an Einstein Probe Fast X-ray Transient

With a small sample of fast X-ray transients (FXTs) with multi-wavelength counterparts discovered to date, the progenitors of FXTs and their connections to gamma-ray bursts (GRBs) and supernovae (SNe) remain ambiguous. Here, we present photometric and spectroscopic observations of SN 2025kg, the supernova counterpart to the FXT EP 250108a. At $z=0.17641$, this is the closest known SN discovered following an Einstein Probe (EP) FXT. We show that SN 2025kg's optical spectra reveal the hallmark features of a broad-lined Type Ic SN. Its light curve evolution and expansion velocities are also comparable to those of GRB-SNe, including SN 1998bw, and several past FXT SNe. We present JWST/NIRSpec spectroscopy taken around SN 2025kg's maximum light, and find weak absorption due to He I $λ1.0830, λ2.0581$ $μ$m and a broad, unidentified feature at $\sim$ 4-4.5 $μ$m. Further, we observe clear evidence for broadened H$α$ in optical data at 42.5 days that is not detected at other epochs, indicating interaction with hydrogen-rich material. From its light curve, we derive a $^{56}$Ni mass of 0.2 - 0.6 $M_{\odot}$. Together with our companion paper (Eyles-Ferris et al. 2025), our broadband data of EP 250108a/SN 2025kg are consistent with a trapped or low energy ($\lesssim 10^{51}$ ergs) jet-driven explosion from a collapsar with a zero-age main sequence mass of 15-30 $M_{\odot}$. Finally, we show that the sample of EP FXT SNe support past rate estimates that low-luminosity jets seen through FXTs are more common than successful (GRB) jets, and that similar FXT-like signatures are likely present in at least a few percent of the brightest Ic-BL SNe.

astro-ph.HE↗

arXiv2025

Euclid: Relativistic effects in the dipole of the 2-point correlation function

Gravitational redshift and Doppler effects give rise to an antisymmetric component of the galaxy correlation function when cross-correlating two galaxy populations or two different tracers. In this paper, we assess the detectability of these effects in the Euclid spectroscopic galaxy survey. We model the impact of gravitational redshift on the observed redshift of galaxies in the Flagship mock catalogue using a Navarro-Frenk-White profile for the host haloes. We isolate these relativistic effects, largely subdominant in the standard analysis, by splitting the galaxy catalogue into two populations of faint and bright objects and estimating the dipole of their cross-correlation in four redshift bins. In the simulated catalogue, we detect the dipole signal on scales below $30\,h^{-1}{\rm Mpc}$, with detection significances of $4\,σ$ and $3\,σ$ in the two lowest redshift bins, respectively. At higher redshifts, the detection significance drops below $2\,σ$. Overall, we estimate the total detection significance in the Euclid spectroscopic sample to be approximately $6\,σ$. We find that on small scales, the major contribution to the signal comes from the nonlinear gravitational potential. Our study on the Flagship mock catalogue shows that this observable can be detected in Euclid Data Release 2 and beyond.

astro-ph.CO↗

arXiv2025

Euclid: Early Release Observations -- The surface brightness and colour profiles of the far outskirts of galaxies in the Perseus cluster

The Perseus field captured by Euclid as part of its Early Release Observations provides a unique opportunity to study cluster environment ranging from outskirts to dense regions. Leveraging unprecedented optical and near-infrared depths, we investigate the stellar structure of massive disc galaxies in this field. This study focuses on outer disc profiles, including simple exponential (Type I), down- (Type II) and up-bending break (Type III) profiles, and their associated colour gradients, to trace late assembly processes across various environments. Type II profiles, though relatively rare in high dense environments, appear stabilised by internal mechanisms like bars and resonances, even within dense cluster cores. Simulations suggest that in dense environments, Type II profiles tend to evolve into Type I profiles over time. Type III profiles often exhibit small colour gradients beyond the break, hinting at older stellar populations, potentially due to radial migration or accretion events. We analyse correlations between galaxy mass, morphology, and profile types. Mass distributions show weak trends of decreasing mass from the centre to the outskirts of the Perseus cluster. Type III profiles become more prevalent, while Type I profiles decrease in lower-mass galaxies with cluster centric distance. Type I profiles dominate in spiral galaxies, while Type III profiles are more common in S0 galaxies. Type II profiles are consistently observed across all morphological types. While the limited sample size restricts statistical power, our findings shed light on the mechanisms shaping galaxy profiles in cluster environments. Future work should extend observations to the cluster outskirts to enhance statistical significance. Additionally, 3D velocity maps are needed to achieve a non-projected view of galaxy positions, offering deeper insights into spatial distribution and dynamics.

astro-ph.GA↗

arXiv2025

Euclid preparation LXXI. Simulations and nonlinearities beyond $\mathsfΛ$CDM. 3. Constraints on $f(R)$ models from the photometric primary probes

We study the constraint on $f(R)$ gravity that can be obtained by photometric primary probes of the Euclid mission. Our focus is the dependence of the constraint on the theoretical modelling of the nonlinear matter power spectrum. In the Hu-Sawicki $f(R)$ gravity model, we consider four different predictions for the ratio between the power spectrum in $f(R)$ and that in $Λ$CDM: a fitting formula, the halo model reaction approach, ReACT and two emulators based on dark matter only $N$-body simulations, FORGE and e-Mantis. These predictions are added to the MontePython implementation to predict the angular power spectra for weak lensing (WL), photometric galaxy clustering and their cross-correlation. By running Markov Chain Monte Carlo, we compare constraints on parameters and investigate the bias of the recovered $f(R)$ parameter if the data are created by a different model. For the pessimistic setting of WL, one dimensional bias for the $f(R)$ parameter, $\log_{10}|f_{R0}|$, is found to be $0.5 σ$ when FORGE is used to create the synthetic data with $\log_{10}|f_{R0}| =-5.301$ and fitted by e-Mantis. The impact of baryonic physics on WL is studied by using a baryonification emulator BCemu. For the optimistic setting, the $f(R)$ parameter and two main baryon parameters are well constrained despite the degeneracies among these parameters. However, the difference in the nonlinear dark matter prediction can be compensated by the adjustment of baryon parameters, and the one-dimensional marginalised constraint on $\log_{10}|f_{R0}|$ is biased. This bias can be avoided in the pessimistic setting at the expense of weaker constraints. For the pessimistic setting, using the $Λ$CDM synthetic data for WL, we obtain the prior-independent upper limit of $\log_{10}|f_{R0}|< -5.6$. Finally, we implement a method to include theoretical errors to avoid the bias.

astro-ph.CO↗