The age of weak lensing surveys

• Alex Amon (online)

I will present the cosmological weak lensing results from the Dark Energy Survey (DES) using its first three years of data taken using the Dark Energy Camera on the 4m Blanco telescope at CTIO. This analysis spans the full DES footprint, more than 4000 sq. deg. of sky, with the final shear catalogue containing more than 100 million galaxies in riz photometric bands, constituting the most powerful weak lensing dataset to date. The comparison of DES cosmological constraints on dark matter and dark energy from WL and LSS in the low-redshift Universe to CMB constraints provides an unprecedented test of the standard cosmological model, across high and low redshift. I will detail the main challenges that our analysis is susceptible to, and summarise the approach to account for these and deliver robust cosmological constraints. Finally, I’ll summarise new developments necessary to exploit future datasets.

The last 10 billion years of cosmic structure growth

• Carlos Garcia-Garcia (University of Oxford)

The current constraints on the S_8 parameter are subject of debate. Cosmic shear observations show a lower value than that predicted by Planck. For instance, KiDS finds results 3\sigma away from Planck's value and data from DESY1 also points in the same direction. In this talk I will show the data driven reconstruction of the evolution of the S_8(z) parameter from a combination of 6 different data sets that include galaxy clustering, weak lensing and CMB lensing (with DESY1 and KiDS-1000 among them). I will show that these data constrain the amplitude of fluctuations in the range 0.2 \lesssim z \lesssim 2 and give consistent growth histories. Furthermore, I will show that in the range 0.2 \lesssim z \lesssim 0.7 current data prefer a lower value than that predicted by Planck and that it is mostly driven by cosmic shear observations.

Cosmology with the largest cosmic structures: new ISW and lensing results from the Dark Energy Survey and the eBOSS quasar data set

• Andras Kovacs (Instituto de Astrofisica de Canarias (IAC))

Dark energy leaves a weak yet characteristic integrated Sachs-Wolfe (ISW) imprint in the cosmic microwave background on the largest scales. Formally, these additional hot and cold spots serve as a consistency test for the standard model that has a definite prediction for the ISW signal relying on precise constraints from other probes. An interesting aspect is that stronger-than-expected imprints aligned with superclusters and supervoids have been observed from the SDSS/BOSS and the DES Year-3 data sets at 0.2<z<0.9, which are hard to explain in the LCDM model and its typical alternatives. Here I present the first detection of additional high-z ISW anomalies from hundreds of supervoids in the eBOSS DR16 quasar catalog which yet again provides corroborating evidence against the LCDM model’s ISW expectation. I will also describe our efforts to use the Planck CMB lensing map to study the origin of these puzzling signals from super-structures, and how the problem of the CMB Cold Spot and its new mapping by the Dark Energy Survey's state-of-the-art dark matter mass maps is related to the ISW anomalies. Taken the recalcitrant evidence at face value, I outline how the low-z and high-z ISW anomalies are related to the H0 and S8 tensions.

First data from the Dark Energy Spectroscopic Instrument (DESI)

• Andreu Font-Ribera (IFAE - Barcelona)

The Dark Energy Spectroscopic Instrument (DESI) started its main survey in May 2021. Over 5 years, it will measure the spectra and redshifts of about 35 millions galaxies and quasars over 14,000 square degrees. This 3D map will be used to reconstruct the expansion history of the universe up to z=3.5, and measure the growth rate of structure in the redshift range 0.7-1.6 with unequaled precision. In this presentation, I will show some preliminary results from the first months of observation. I will also review the forecasted performance of the DESI survey, and show how it will dramatically improve our understanding of dark energy, inflation, and the mass of the neutrinos.

The CMB Lensing Imprint of Cosmic Voids

• Umut Emek Demirbozan (online) (IFAE - BCN)

Cosmic voids gravitationally lens the cosmic microwave background(CMB). This weak lensing shows itself as negative convergence(kappa) imprint on the CMB lensing map. We use one of the largest available sky surveys(Dark Energy Survey Y3) and Planck 2018 CMB lensing map along with a simulated CMB lensing convergence map from the MICE N-body simulation to calibrate our detection. We stack void centre positions on the CMB map and use a matched filtered approach(that has been used before for BOSS spectroscopic voids) to further optimise our S/N. By using 2 different void types, we measure the lensing imprint of CMB by voids up to S/N =4.56𝜎 for DES Y3. We find that both types of voids show slightly weaker CMB lensing signal than Lambda-CDM expectations as calibrated by MICE N-body simulation. Our result is consistent with another DES Y3 study which uses another method(Kovacs et al, in prep) and also with DESI Imaging Survey DR8 study( Hang et al,2021). We discuss possible reasons for this finding.

Bridging the divide between theoretical and observational cosmology: ShapeFit results from the BOSS+eBOSS legacy

• Samuel Brieden (ICC - University of Barcelona)

Since the ~90's, there is an ongoing discussion in the community on how to analyse large spectroscopic galaxy survey maps. In a nutshell, there are two very different approaches on how to gain cosmological information from the 3D galaxy density distribution: i) model the galaxy 2-point correlation functions and directly fit them to the data as it is done for the Cosmic Microwave Background observations leading to optimal constraints for cosmological model parameters or ii) use templates of the 2-point correlation function to infer robust, model-agnostic constraints on the expansion and growth of structures history of the universe and hence deliver an important cross check of our model assumptions as done in the BOSS and eBOSS surveys. In this talk I will explain how our new ShapeFit approach can bring these two "philosophies" together via an additional ‘shape’ parameter capturing the broadband slope of the power spectrum. I will present cosmological results from BOSS+eBOSS legacy data using ShapeFit and discuss their implications for the current status. Finally, I will emphasize the importance of model-agnosticism in ongoing surveys such as DESI.

Dwarf spheroidals heated by Fuzzy Dark Matter fluctuations

• Riccardo Della Monica (Universidad de Salamanca)

Dwarf spheroidal galaxies (dSph) have been observed to possess multiple stellar populations with different chemical, kinematical and dynamical properties. In particular, metal-rich (younger) stars have a more centrally concentrated, less extended and less oblate spatial distribution and show colder kinematics than the metal-poor (older) stars. Different mechanisms have been proposed to explain the apparent differences in older vs. younger stellar populations in these systems. We have studied numerically a heating process that could naturally develop energy and momentum transfer between the peculiar granularities of ultralight Fuzzy Dark Matter and a stellar population moving in the potential generated by the halo. This mechanism could explain the observed differences between stellar populations over time-scales of ~ 10 Gyrs.

Cosmology from Weak Lensing Non-Gaussian Statistics

• Marco Gatti (UPenn )

The statistical analysis of lensed galaxies is a powerful tool to study the dark matter distribution of the Universe. For instance, the distortion of galaxy shapes induced by the large scale structure of the Universe can be used to reconstruct the projected matter density along the line-of-sight (mass maps). Mass maps are useful as they provide a wealth of information that goes beyond and complements the more traditional two-point statistics used in Cosmology. During this talk, I will present the mass map obtained using the first three years of data (Y3) of the Dark Energy Survey (DES), which is the largest curved-sky galaxy weak lensing mass map to date. I will then show the constraints on cosmological parameters from two independent analyses using non Gaussian statistics applied to the DES Y3 mass maps: moments and peaks. The constraints from these analyses are compatible with and tighter than the ones from the fiducial DES Y3 cosmic shear analysis, which only relies on two-point statistics. These results showcase the potential of non Gaussian statistics in terms of cosmological constraining power and as independent consistency check with ordinary two-point statistics.

Cosmology and Clusters with the Atacama Large Aperture Submm Telescope (AtLAST)

• Tony Mroczkowski (online) (European Southern Observatory (ESO))

AtLAST will be a 50-meter-class telescope operating over the frequency range 30-950 GHz high in the Atacama Desert. The design goal is to achieve a field of view (FoV) 1-2 degrees in diameter. AtLAST will be the first telescope with an aperture larger than 10 meters to feature a FoV > 0.5 degrees, covering mm/submm wavelengths with good aperture efficiency up to 1 THz. It will be sited in the Atacama Desert in northern Chile at an elevation > 5000 meters above sea level and will deliver a throughput greater than that of CCAT-p/FYST, and with >8 times higher resolution. In the cosmological context< AtLAST will be able to probe the thermal, kinetic, and relativistic SZ effects on scales from 10” to 1 degree, measure the primary CMB at ell~20000, measure the multiple phases (i.e. the cold, warm, and hot) of the circumgalactic medium of galaxies, and provide resolved tomography of the dusty high-z universe to a confusion limit 2 orders of magnitude lower than any 6-10 meter class survey experiments planned or currently under construction. I will provide an overview of the project and science cases relevant to cosmology.

L-σ relation of Giant HII Regions and HII Galaxies as tracers of the Hubble expansion.

• David Fernandez Arenas (Instituto Nacional de Astrofísica, Óptica y Electrónica (INAOE))

The relationship between the integrated Hβ line luminosity and the velocity dispersion of the ionized gas of HII galaxies (HIIGs) and giant HII regions (GHIIRs) has been known for a long time as the L-σ relation (Terlevich et. al. 1981 and more recently Bordallo & Telles 2011 and Chavez et. al. 2014). The scatter in the relation is small enough that it can be used to determine cosmic distances independently of redshift and represents an interesting distance estimator that, in principle, can be used up to redshifts z ∼ 4. Locally it can be used to obtain high precision measurements of the local Hubble parameter. This can be done using a sample of nearby (z ≤ 0.1) HIIGs galaxies and, crucially, an anchor sample of GHIIRs in nearby galaxies for which distances via primary indicators are available. I will be presenting our recent results of the use of the L-σ relation to measure the local value of the Hubble constant (Fernández et. al. 2018) and to constrain the Dark Energy equation of State Parameter (w) (González-Morán et. al. 2020,2021).

Lyman-alpha correlations from early DESI data

• Calum Gordon (IFAE - Barcelona)

The Dark Energy Spectroscopic Survey (DESI) will during its operation observe the spectra of 10s of millions of galaxies and quasars. Already, the largest ever 3D map of the universe has been created from combined Survey Validation (SV) and Main Survey data. Around one third of the total quasar sample will be observed at redshifts greater than ~2, where we can use the Lyman-alpha (Lya) forest (a region of strong absorption between the Lyman-beta and Lya emission lines) to measure baryon acoustic oscillations (BAO) at an effective redshift of z ~ 2.3. In my talk I will briefly detail how we go from raw quasar spectra to the 3D correlation functions used in Lya BAO measurements. These include the Lya auto correlation, where Lya forest pixels from different lines-of-sight are correlated, and the Lya-quasar cross correlation, where pixels in the Lya forest are correlated with quasars at all redshifts. I will also present results from the most recent stable DESI data release, used to form the basis of the first Lyman-alpha Woking Group main paper of which I am a lead author.

Blind Observers of the Sky

• Hector Gil-Marin (ICCUB - Barcelona)

I will present the novel technique for blinding redshift-spectroscopic data and avoiding the human bias towards the established state-of-the-art models, such as LCDM. The blinding technique relies on a theoretically-motivated shift of the radial distances (or redshift) of spectroscopically detected galaxies, in such a way that the sample effectively behaves as if its underlying cosmology were different from the actual one, both in background and perturbation signals. The approach is validated on BOSS data and mocks, for both BAO and RSD type of analyses. This is the actual blinding approach addopted by the on-going DESI survey, which will deliver its firts cosmology results by summer 2023.

Strong Blended Lyman alpha absorbers as a new BAO tracer

• Ignasi Pérez-Ràfols (online) (IFAE - Barcelona)

The standard Lyman alpha BAO analysis includes the Lyman alpha autocorrelation and its cross-correlation with quasars. One of the main contaminants, that we mask whenever possible, are DLAs and, in general, galaxies in absorption. However, one can take these galaxies, detected also as Strong Blended Lyman alpha absorbers, and use them as BAO tracers. I will present the first BAO measurement using these tracers and discuss the necessary steps to include them to the standard Lyman alpha BAO analysis, improving the constraints by at least aournd 10%

Optimization of Spectroscopic Tests of Fundamental Physics: from ESPRESSO to the ELT

• Catarina Marques (online) (CAUP/FCT-NOVA)

Studying the dark universe and fundamental physics is one of the science and design drivers of the ArmazoNes high Dispersion Echelle Spectrograph (ANDES). We have developed computational tools that can optimize the scientific return of fundamental physics tests using redshift drift and fine structure constant measurements for this instrument, separately or in combination, and also quantify the scientific impact of possible instrument configurations. This is an important result for the ANDES Phase B, making it possible to identify the key parameters for the necessary scientific trade-offs, and will ultimately lead to the definition of an optimized observing strategy. We will illustrate our analysis with some representative examples.

A Sample of Dust Attenuation Laws for DES Galaxies

• João Duarte (online) (CENTRA, IST, Universidade de Lisboa)

Type Ia supernovae (SNe Ia) are useful distance indicators in cosmology, provided their luminosity is standardized by applying empirical corrections based on light-curve properties. One factor motivating these corrections is dust extinction, accounted for in the beta color-luminosity relation of the standardization. As the role of dust in both supernova and extra-galactic astronomy is still poorly understood, this $\beta$ relation is assumed to be universal, which can introduce systematics into the standardization. The ``mass-step'' observed for SNe Ia Hubble residuals has been suggested as one such systematic. In this work we seek a more complete view of dust attenuation properties for a sample of 162 SN Ia host galaxies and to ascertain whether the ``mass-step'' is linked to these same properties. We propose an alternative approach to infer dust attenuation laws towards host galaxies, from both global and local (4 kpc) Dark Energy Survey photometry. Simple Stellar Population models are fitted to this photometry and used to map dust properties. We find a relation between the attenuation slope and the optical depth, best explained by varying star/dust geometry with galaxy orientation. This relation is shown to be very different from the extinction slope/optical depth relation found directly for SNe. Analyzing the Tripp standardization, we find evidence for a two dimensional ``dust-step'', which, although comparable to the ``mass-step'', is not completely analogous to it. We study an alternative SNe Ia standardization, in which the extinction contribution to the color-luminosity correction is fixed using the previously obtained host attenuation. This proves a worse fit of the data, exacerbating the ``mass-step''. We conclude that dust properties vary greatly across different galaxies, meaning a universal $R_V=3.1$ or a universal SN Ia correction cannot be assumed. We also conclude that the ``mass-step'' cannot be fully accounted for using host galaxy dust data, either using an alternative SN standardization with extinction approximated by host attenuation or a ``dust-step'' approach.

Testing the homogeneity of Type Ia Supernovae in the Near-infrared for accurate distance estimations

• Tomás Müller (online) (Institute of Space Sciences (ICE))

Since the discovery of the accelerating expansion of the universe more than two decades ago, type Ia supernovae (SNe Ia) have been extensively used as standardizable candles in the optical. However, SNe Ia have shown to be more homogeneous in the near-infrared (NIR), where the effect of dust extinction is also attenuated. In this work, we explore the possibility of using a low number of NIR observations for accurate distance estimations, given their homogeneity at these wavelengths. We found that 1 epoch in J and/or H band, plus good gr-band coverage, gives an accurate estimation of Jmax and Hmax, and only introduces an additional scatter of ~0.04-0.05 mag for NIR epochs around optical peak. We also tested the effect of cadence and signal-to-noise in the estimation of \tmax and its uncertainty propagation to the NIR peak magnitudes, where we constrained the introduced scatter to <0.02 mag in Jmax and <0.01 in Hmax, considering in extreme cases. However, the effect of these are expected to be negligible, provided of data quality comparable to those usually obtained for observations of close-by SNe (z < 0.1). Following these results, we initiated the FLOWS project with the aim of using SNeIa with public ZTF optical light curves and few NIR epochs to map out the peculiar velocity field of the local universe. This will allow us to determine the distribution of dark matter in our own supercluster, Laniakea, and test the standard cosmological model by measuring the growth rate of structure parameterized by fD and H0.

Redshift Calibration of Lens Samples in DESY3 from the combination of SOMPZ and clustering

• Giulia Giannini (online) (IFAE)

Biased redshift calibration is one of the limiting factors of wide-field imaging surveys. Cosmological constraints from weak gravitational lensing suffer particularly from this misestimation, since they rely on the redshift distributions of both the lens and source galaxies. Lens catalogues are generally constructed by selecting galaxies with optimal quality redshifts (i.e. redMaGiC), but this results in samples with low number density. Instead, the Dark Energy Survey (DES) built MagLim, an alternative lens catalogue for the Year 3 (Y3) analysis, with bright magnitude limits at each tomographic bin imposed to reduce photo-z error at maximum density. In this work we present an alternative calibration of the MagLim lens sample redshift distributions. This is based on a combination of a Self-Organising Maps scheme and clustering redshifts to estimate redshift distributions and inherent uncertainties, which is expected to be more accurate than the original DES Y3 redshift calibration of the lens sample. We describe in detail the methodology, we validate it on simulations and discuss the main effects dominating our error budget. The new calibration is found to be in fairly agreement with the fiducial DES Y3 calibration, with only mild differences in the means and widths of the distributions. We study the impact of this new calibration on cosmological constraints, analysing DES Y3 galaxy clustering and galaxy-galaxy lensing measurements, assuming a ΛCDM cosmology. The ~0.4σ shift in the main matter density and clustering amplitude plane compared to the fiducial DES Y3 results, highlights the importance of the redshift calibration of the lens sample in multi-probe cosmological analyses.

Observational measurements of the dark matter halo abundance through the submillimeter galaxy magnification bias: a tomographic approach

• Marcos Muñiz Cueli (online) (Departamento de Física, Universidad de Oviedo)

The gravitational lensing effect of magnification bias can manifest itself through a nonzero measurement of the cross-correlation between two samples of galaxies with nonoverlapping redshift distributions. Given the dependance of the magnification bias signal on cosmology and since submillimeter galaxies are an optimal background sample for this kind of study, this work makes use of galaxy samples from the H-ATLAS and GAMA II catalogs to measure the cross-correlation between them. By means of a halo model description of the signal, observational restrictions on the dark matter halo mass function are obtained under a Planck cosmology, both in a nontomographic and a tomographic setting. Whereas results are only compatible with those from numerical simulations for the former case, mainly due to the large error bars, a tomography-based approach provides a remarkable improvement regarding uncertainties. In fact, compared to N-body results, our approach predicts a higher number density of dark matter halos for masses below 10^13 solar masses and a steeper fall for masses above 10^14.5 solar masses.

Measuring Intrinsic Alignments with PAUS data

• David Navarro Girones (online) (Institute of Space Sciences (ICE-CSIC))

The intrinsic alignment of galaxies due to the local tidal fields during the galaxy formation and evolution are a fundamental quantity to consider in ongoing and future weak lensing analysis. They can mimic the signal of gravitational lensing and be a dominant systematic in its measurement and, thus, on the inference of cosmological parameters. Determining accurate redshifts is another key component in these analysis. The Physics of the Accelerating Universe Survey (PAUS) is a photometric survey with 40 narrow bands in the range between 4500 A ̊ and 8500A ̊, that scanned 1.5 million galaxies down to i-magnitude < 23 in the∼45 deg2 area of the W1 and W3 fields of CFHTLenS and of the W2 field of KiDS. PAUS data perfectly fills gaps to both problems, both IA and photo-z, as we will discuss in this talk. Photometric redshifts computed via a template-based code called BCNz will be presented, with improvement implemented in the calibration allowing to compute photometric redshifts in fields where no information of spectroscopic redshifts is available. Projected two-point correlation measurements will be performed using these high-quality photometric redshifts, and shape measurements from CFHTLS and KiDS but doubling the area of observation and reaching to fainter magnitudes with respect to previous PAUS studies (Johnston, Harry et al. A&A 2021, 646, A147).

An overview on cosmological tensions

• Eleonora Di Valentino

The scenario that has been selected as the standard cosmological model is the Lambda Cold Dark Matter (ΛCDM), which provides a remarkable fit to the bulk of available cosmological data. However, discrepancies among key cosmological parameters of the model have emerged with different statistical significance. While some portion of these discrepancies may be due to systematic errors, their persistence across probes can indicate a failure of the canonical ΛCDM model. I will review these tensions, showing some interesting extended cosmological scenarios that can alleviate them.

Model-independent constraints on Ωm and H(z) from the link between geometry and growth

• Jaime Ruiz Zapatero (University of Oxford)

In the light of the S8 and Hubble tensions, Gaussian processes have gained a great degree of popularity among cosmologist as tools to perform model-independent analyses. However, there's not a well-established consensus on how or when to deploy these methods yet. In this talk I will discuss the methodology and results of our recent work https://arxiv.org/abs/2201.07025. In this paper we constrain the expansion history of the Universe and the cosmological matter density fraction in a model-independent way by exclusively making use of the relationship between background and perturbations under a minimal set of assumptions. We do so by employing a Gaussian process to model the expansion history of the Universe from present time to the recombination era. I will focus on the difficulties posed by the Hubble rate and other similar functions to Gaussian processes and how we tackled them in this work while remaining as independent from the LCDM model as possible. I will also present the results of our work in the context of the different cosmic tensions and the promising future of model-independent analyses as the quality of data increases over time.

Gravitational waves in bimetric gravity

• Araceli Soler (University of the Basque Country (UPV/EHU))

We study the propagation of gravitational waves in bimetric gravity in a homogeneous and isotropic cosmological background with non-zero spatial curvature. In particular, we focus on the evolution of sub-horizon and super-horizon tensor modes in the limit of small interactions and for a background with a general equation of state. We also study in detail the transitions between different cosmic eras. To keep our analysis as general as possible, we do not assume any specific values for the parameters of the theory in the derivation of analytical solutions.

Numerical formation of PBHs during the QCD phase transition

• Albert Escrivà (University of Brussels (ULB))

Primordial Black Holes (PBHs) could have been formed in the very early universe due to the collapse of large curvature fluctuations after inflation. PBHs are nowadays one of the most attractive and fascinating research areas in cosmology for their possible theoretical and observational implications. In this talk, I will review the physical process of PBH formation and I will give some new results regarding the formation of PBHs during the QCD phase transition.

Forecasting F(Q) cosmology with LCDM background using standard sirens

• José Ferreira (Instituto de Astrofísica e Ciências do Espaço)

Forecast constraints for a Symmetric Teleparallel Gravity model with a $\Lambda$CDM background are made using forthcoming ground and space based gravitational waves observatories. A Bayesian analysis resorting to generated mock catalogs shows that LIGO is not expected to be able to distinguish this model from $\Lambda$CDM, while both LISA and the ET will, with the ET outperforming LISA. We also show that low redshift events are favored in order to improve the quality of the constrains.

Binary systems as gravitational wave detectors

• Diego Blas (UAB/IFAE)

The passage of gravitational waves (GWs) through a binary perturbs the trajectories of the two bodies, potentially causing observable changes to their orbital parameters. In the presence of a stochastic GW background (SGWB) these changes accumulate over time, causing the binary orbit to execute a random walk through parameter space. In this talk I will present a new formalism for calculating the full statistical evolution of a generic binary system in the presence of a SGWB, capturing all six of the binary's orbital parameters. I will show how this formalism can be applied to timing of binary pulsars and lunar laser ranging, thereby setting novel upper limits on the SGWB spectrum in a frequency band that is currently inaccessible to all other GW experiments.

Testing freeze-in with Z’ bosons

• Catarina Cosme (IFIC, U. València)

The freeze-in production of Feebly Interacting Massive Particle (FIMP) dark matter in the early universe is an appealing alternative to the well-known — and constrained — Weakly Interacting Massive Particle (WIMP) paradigm. Although challenging, the phenomenology of FIMP dark matter has been receiving growing attention and is possible in a few scenarios. In this talk, I will discuss a model of a Z’ portal to fermionic dark matter, with the Z’ having both vector and axial couplings to ordinary and dark fermions and a mass ranging from MeV up to PeV. I will show how the parameter space of this model can be constrained with bounds from direct detection, atomic parity violation, leptonic anomalous magnetic moments, neutrino-electron scattering, collider, and beam dump experiments.

The stochastic gravitational wave background from close hyperbolic encounters of primordial black holes in dense clusters

• Santiago Jaraba (IFT UAM-CSIC)

The inner part of dense clusters of primordial black holes is an active environment where multiple scattering processes take place. Some of them give rise from time to time to bounded pairs, and the rest ends up with a single scattering event. The former eventually evolves to a binary black hole (BBH) emitting periodic gravitational waves (GWs), while the latter with a short distance, called close hyperbolic encounters (CHE), emits a strong GW burst. We make the first calculation of the stochastic GW background originating from unresolved CHE sources. Unlike the case for BBH, the low-frequency tail of the SGWB from CHE is sensitive to the redshift dependence of the event rate, which could help distinguish the astrophysical from the primordial black hole contributions. We find that there is a chance that CHE can be tested by third-generation ground-based GW detectors such as Einstein Telescope and Cosmic Explorer.

Contrasting predictions of Loop Quantum Cosmology with observations

• Rita Neves (Universidad Complutense de Madrid)

It has been shown that Loop Quantum Cosmology (LQC) has the potential to alleviate anomalies related to large scale power suppression and the lensing amplitude present in observations of the CMB. As a consequence of the pre-inflationary dynamics, some modes reach the onset of inflation in an excited state with respect to the Bunch-Davies vacuum, resulting in a scale dependence of the primordial power spectrum for large scales. However, the choice of vacuum state in the pre-inflationary regime and free parameters of the theory impact the concrete predictions. In this ongoing work we perform an MCMC analysis of the hybrid LQC model, contrasting with observations from the CMB, in order to obtain constraints on its free parameters and investigate whether the alleviation of some anomalies is prevalent.

Reconstructing the inflaton's speed of sound using Cosmological data

• Guadalupe Cañas Herrera (Leiden University)

Observations of Planck's CMB favours a canonical slow-roll single-field scenario for inflation. However, simple multi-field extensions can also explain the current data, and on top some of the existing anomalies not accounted for by the canonical scenario. We present our search for multi-field-motivated extra degrees of freedom in the context of an effective single field theory with a varying speed of sound 𝑐𝑠 of the adiabatic mode. Transient reductions in 𝑐𝑠 produce deviations (or "features") in the primordial power spectrum of scalar perturbations. Features of sufficient intensity may be observed in the CMB angular power spectrum (T and E), and in the power spectrum of galaxy clustering and weak lensing. Moreover, our theory predicts also correlated features in higher-order correlators (e.g. the bispectrum). We present a standard methodology based on Gaussian Processes for general Bayesian reconstruction of primordial dynamics that imprint primordial features, accounting for theoretical priors in a natural way, and show some results when we reconstruct the reduction of the speed of sound using cosmological data.

Can late-time extensions solve the $H_0$ and $\sigma_8$ tensions?

• Hector Villarrubia-Rojo (Max Planck Institute for Gravitational Physics (AEI))

The Hubble tension poses a significant threat to the, otherwise extremely successful, LCDM model. The mismatch between the value of H0 inferred from the CMB and the independent local measurements has become increasingly worrying, to the point where we may need to start looking for alternatives. Many LCDM extensions have been proposed to address this problem. However, many of them seem to alleviate the $H_0$ tension at the cost of increasing the tension with other cosmological parameters, like the clustering amplitude $\sigma_8$. In our work we study, analytically and in a model-independent way, the conditions that any late-time extension to LCDM must met to simultaneously solve both the $H_0$ and the $\sigma_8$ tension. We obtain a set of necessary conditions that can be applied to a generic model. As a particular application, we derive conditions on the equation of state of a dark energy model.

Probing the substructure of dark matter with gravitational wave lensing

• Juan Urrutia (IFAE - Barcelona)

As the number of events that gravitational wave detectors detect increases, the expectation of finding lensed events increases. We will consider the implications of different dark matter models to this and show that the lensing of gravitational waves is going to be a powerful and complementary tool to microlensing of light to constrain dark matter models.

Coupled Quintessence in a Closed Universe

• Elsa Teixeira (online) (University of Sheffield)

Understanding what drives the accelerated expansion of the Universe is one of the most important open questions in Cosmology. This phenomenon is generally attributed to "dark energy", a matter/energy source whose nature is still not well understood and that, in the simplest ΛCDM scenario, is characterised by an energy density that remains constant with the expansion. While it provides for an impressive fit to a wide range of astrophysical data, significant statistical discrepancies between observations seem to indicate unreconcilable cracks in the standard theory, when faced with increasingly precise experiments. In this talk we will show how relaxing the usual flat geometry condition, and generalising dark energy to quintessence - a dynamical scalar field - may help understand and possibly address the observational tensions.

Constraining a simple parametrisation for varying alpha

• Victor da Fonseca (online) (Instituto de Astrofísica e Ciências do Espaço)

One of the main science drivers of the high-resolution spectrograph ESPRESSO concerns the stability of physical constants, in particular the fine-structure constant on which strong bounds are provided by local experiments in short time-scales. Thanks to the more precise measurements of distant spectra quasars, ESPRESSO strengthens the limits on the variation of $\alpha$ in astrophysical time-scales. Even null results with increased accuracy would be beneficial to test cosmological models that predict a varying $\alpha$. The model we test assumes that the electromagnetic sector is coupled to the scalar field responsible for the dark energy accelerating the Universe. We parametrise the resulting variation of the fine-structure constant by introducing two extra degrees of freedom beyond the concordance model. The first parameter drives the cosmological evolution of the quintessence component while the second one represents its coupling with the electromagnetic field. We perform a Bayesian analysis to constrain our parametrisation by comparing its predictions with observations. The datasets are composed of astrophysical measurements of QSO spectra, including the latest ESPRESSO data point, as well as Planck data on the cosmic microwave background. We combine them with local results from atomic clocks and the MICROSCOPE experiment. The constraints obtained on the parameter driving the quintessence evolution are consistent with a null variation of the field, i.e. compatible with a $\Lambda$CDM cosmology, while those on the coupling to the electromagnetic sector are dominated by the Eötvös parameter local bound.

Can Modified Gravity challenge LCDM?

• Noemi Frusciante (online) (IA/FCUL)

The late time cosmic acceleration is one of the most puzzling phenomena in modern cosmology. Its modeling within General Relativity (GR) through the cosmological constant (L) results in the LCDM scenario. Although the latter gives a precise description of the Universe, it is known that it still contains a number of unresolved problems. These lead researchers to look for modified gravity models, for example by including additional degrees of freedom. In this talk I will present the phenomenology and the cosmological bounds of theories consistent with the gravitational-wave event GW170817. In particular I will discuss models which solve the Hubble tension between Planck and local measurements and for which data show a statistically significant preference over LCDM.

Evaporating primordial black holes, the string axiverse, and hot dark radiation

• Marco Calza (online) (University of Coimbra)

We show that primordial black holes (PBHs) develop non-negligible spins through Hawking emission of the large number of axion-like particles generically present in string theory compactifications. This is because scalars can be emitted in the monopole mode (l = 0), where no angular momentum is removed from the BH, so a sufficiently large number of scalars can compensate for the spin-down produced by fermion, gauge boson, and graviton emission. The resulting characteristic spin distributions for 10^8-10^12 kg PBHs could potentially be measured by future gamma-ray observatories, provided that the PBH abundance is not too small. This yields a unique probe of the total number of light scalars in the fundamental theory, independent of how weakly they interact with known matter. The present local energy density of hot, MeV-TeV, axions produced by this Hawking emission can possibly exceed ρCMB. Evaporation constraints on PBHs are also somewhat weakened.

Primordial magnetic field generation in theories of gravity with non-minimal coupling between curvature and matter

• Maria Margarida Lima (online) (ISCAP - Instituto Politécnico do Porto)

The existence of magnetic fields in the universe is unmistakable. They are observed at all scales from stars to galaxy clusters. However, the origin of these fields remains enigmatic. It is believed that magnetic field seeds may have emerged, under conditions, from inflation. This possibility is analised in the context of an alternative theory of gravity with non-minimal coupling between curvature and matter.

Can f(Q) gravity challenge LCDM?

• Luis Atayde (online) (IA/FCUL)

Despite the Lambda CDM's overall success, there are still some theoretical and observational problems. Looking beyond LCDM is thus a priority. Here we show an alternative scenario of the non-metricity f(Q)-gravity which reproduces an exact Lambda CDM background expansion history while modifying the evolution of linear perturbations. I will present the phenomenology and the observational constraints employing Markov chain Monte Carlo (MCMC) methods with the Cosmic Microwave Background (CMB) radiation, baryonic acoustic oscillations (BAO), redshift-space distortions (RSD), supernovae type Ia (SNIa), galaxy clustering (GC) and weak gravitational lensing (WL) measurements. I show the constraints on the parameter of the model controlling the modifications to the gravitational interaction at the linear perturbation level and how and why the model is statistically preferred by data over the LCDM.

Axion-like particles from primordial black holes shining through the Universe

• Francesco Capozzi (online) (Instituto de Fisica Corpuscular)

We consider a cosmological scenario in which the very early Universe experienced a transient epoch of matter domination due to the formation of a large population of primordial black holes (PBHs) with masses M < 10^9 g, that evaporate before Big Bang nucleosynthesis. In this context, Hawking radiation would be a non-thermal mechanism to produce a cosmic background of axion-like particles (ALPs). We assume the minimal scenario in which these ALPs couple only with photons. In the case of ultralight ALPs (m < 10^-9 eV) the cosmic magnetic fields might trigger ALP-photon conversions, while for masses m > 10 eV spontaneous ALP decay in photon pairs would be effective. We investigate the impact of these mechanisms on the cosmic X-ray background, on the excess in X-ray luminosity in Galaxy Clusters, and on the process of cosmic reionization.

Cosmology in the machine learning era

• Francisco Villaescusa Navarro (Simons Foundation & Princeton University )

Recent advances in deep learning are triggering a revolution across fields in science. In this talk I will show how these techniques can also benefit cosmology. I will present a new approach whose final goal is to extract every single bit of information from cosmological surveys, discussing all the complications involved on it. I will start showing the large amount of cosmological information that is embedded on small, non-linear, scales; information that cannot be retrieved using the traditional power spectrum. I will then show how neural networks can learn the optimal estimator needed to extract that information. I will discuss the role played by baryonic effects and point out how neural networks can automatically learn to marginalize over them even at the field level. From volumes covering Gigaparsec scales to individual galaxies, I will show how accurately the value of the cosmological parameters can be constrained. I will show how this approach requires combining machine learning techniques with numerical simulations. Along the talk, I will present the simulations we are using in this program: the Quijote and the CAMELS simulations. These two suites contain thousands of N-body and state-of-the-art (magneto-)hydrodynamic simulations covering a combined volume larger than the entire observable Universe (Quijote) and sampling the largest volume in parameter space for astrophysics models to-date (CAMELS).

Improving broad-band photo-z with narrow-band data and multi-task learning

• Laura Cabayol García (IFAE)

Current and future imaging surveys require estimating photometric redshifts of millions of galaxies. Improving the photo-z quality is a major challenge to advance our understanding of cosmology. In this work, we have explored how the synergies between narrow-band photometric data and large imaging surveys can be exploited to improve broad-band photometric redshifts. We use a multi-task learning network to improve broad-band photo-z estimates by simultaneously predicting the broad-band photo-z and the narrow-band photometry from the broad-band photometry. The narrow-band photometry is only required in the training field, which enables better photo-z predictions also for the galaxies without narrow-band photometry in the wide field. This technique is tested with data from the Physics of the Accelerating Universe Survey (PAUS) in the COSMOS field. We find that the method predicts photo-z that are 14\% more precise down to magnitude i_{AB}<23 while reducing the outlier rate by 40% with respect to photo-z estimated solely from broad bands. Furthermore, MTL significantly reduces the photo-z bias for high-redshift galaxies, improving the redshift distributions for tomographic bins with z>1. We have also studied the effects of extending the training sample with photometric galaxies using PAUS high-precision photo-z, which further reduces the photo-z scatter.

CoLoRe: fast cosmological realisations over large volumes with multiple tracers

• César Ramírez-Pérez (IFAE)

We present CoLoRe, a public software package to efficiently generate synthetic realisations of multiple cosmological surveys. CoLoRe can simulate the growth of structure with different degrees of accuracy, with the current implementation supporting lognormal fields, first, and second order Lagrangian perturbation theory. CoLoRe simulates the density field on an all-sky light-cone up to a desired maximum redshift, and uses it to generate multiple 2D and 3D maps: galaxy positions and velocities, lensing (shear, magnification, convergence), integrated Sachs-Wolfe effect, line intensity mapping, and line of sight skewers for simulations of the Lyman-α forest.

Primordial Non-Gaussianities and their imprints in the Large Scale Structure

• Adrián Gutiérrez Adame (UAM / IFT)

Measuring the level of Primordial Non-Gaussianities (PNGs) would give us some tight constraints on the inflation model landscape. The deviations from the Gaussianity are usually quantified by the fNL parameter. In the next few years, we will have available data from the Stage-IV galaxy surveys, such as DESI, EUCLID, LSST and SKA. These experiments are expected to constrain the fNL parameter to σ (fNL) ∼1. This would improve the strongest current constraints from the CMB measurements and it would be particularly interesting as this could rule out some models of single/multi - field inflation. In this talk, I will discuss the imprints left by the local PNGs on the Large Scale Structure: the enhancement/suppression of the formation of heavy dark matter halos, and the scale-dependent bias. On one hand, the effect of local PNGs can be observed in the halo mass function. By using a large set of numerical simulations, I will show this effect and how to model it. On the other hand, galaxy clustering is also affected by this type of PNGs, in particular at the largest scales, where it induces a scale-dependence in the bias relation between the dark matter and galaxies. In order to study this effect, I will introduce one of the most advanced state-of-the-art N-body simulations with PNGs, the PNG-UNITSim suite, with 4096^3 DM particles. Then, I will talk about how we are using this simulation to constrain the parameters of the galaxy/halo bias induced by the PNGs. Constraining these parameters will be necessary for an accurate measurement of fNL by future galaxy surveys, which is key for understanding inflation.

The genetic algorithms and their cosmological applications

• Savvas Nesseris (online) (IFT UAM/CSIC)

Machine learning algorithms have revolutionized the way we interpret data, as they can remove biases due to a priori chosen theoretical models. In this talk, I will give a brief overview of the Genetic Algorithms (GA), a particular machine learning approach, and then I will present specific applications to cosmology. In particular, I will show how the GA can be applied to cosmological data (type Ia supernovae, BAO, Cosmic Chronometers, growth rate data etc) in order to obtain model independent, theory agnostic and non-parametric reconstructions without assuming any dark energy model or a flat Universe. I will also briefly present some related Euclid forecasts but also an application of the GA to improved fits of the sound horizon at the drag redshift, which is of interest for BAO analyses.

HIR4: Cosmology from the cross-correlation of extragalactic radio and optical surveys with simulated neutral hydrogen full sky using Horizon Run 4

• Jacobo Asorey (CIEMAT)

We are currently living a blooming era of wide field optical cosmological surveys, either spectroscopic such as Dark Energy Spectroscopic Instrument (DESI) or photometric such as the ongoing Dark Energy Survey (DES), the future Large Synoptic Survey Telescope (LSST) or the future imaging component survey of EUCLID. By analyzing the distribution of matter clustering, we can use the growth of structure, in combination with measurements of the expansion of the Universe, to understand dark energy or to test different models of gravity. Radio surveys will map the matter distribution at high redshifts, especially covering the current redshift dessert between early and late expansion, crucial to discriminate between current cosmological theoretical models. The distribution of cosmological neutral hydrogen will provide a new window into the large-scale structure of the Universe with the next generation of radio telescopes and surveys. The observation, through 21cm line emission, is confused by instrumental noise and foreground emission. I will introduce the simulated neutral hydrogen full sky catalogues that we have created, using the Horizon run 4 simulations (HIR4). The simulations HI intensity maps include realistic foregrounds and expected noise for Tianlai, one of the SKA Observatory (SKAO) precursors. In particular, I will show the prospects of measuring the growth rate of structures with only HI intensity mapping information around redshift z=1 and how by cross-correlating the neutral hydrogen information with optical galaxy catalogues, such as DESI, helps us by alleviating the effects of noise and foregrounds.

Using enhanced simulations to reach accurate cosmology: applications to Primordial Non-Gaussianities

• Santiago Avila (Instituto de Física Teórica (UAM-CSIC))

Numerical simulations constitute a key ingredient in cosmological analysis, especially in the field of Large-Scale Structure. In particular, they have been widely used to inform, validate, compare and improve models of galaxy clustering. However, their use on those aspects is limited by their intrinsic variance, determined by the simulated volume, limited by computational resources at fixed mass resolution. In the past, Fixed and Paired simulations (Angulo & Pontzen, 2016) have been proposed to reduce the variance, increasing the effective volume. Additionally, if we simulate two cosmologies with the same initial phases, their intrinsic noise is correlated and we are able to cancel out most of it. For the first time, we show how to explicitly use the reduction of variance induced by both techniques to significantly increase the capability of model testing of simulations. We apply these techniques to test the standard modeling of halo clustering in the presence of local Primordial Non-Gaussianities (PNG) (Dalal et al. 2008). PNG has been shown to induce a characteristic scale-dependent bias that increases the clustering at very large scales. This is a very promising observable to constrain inflationary models, parameterized with fnl (being fnl=0 in a Gaussian cosmology). We show that the techniques presented here can reduce the inferred errorbar on fnl by a factor of ~7, this means that we increase by a factor of 7 the accuracy that we can probe on our model. Equivalently, these techniques represent an increment of the effective simulated volume by a factor of ~50, or a reduction of a factor ~300 in the computing resources. These are powerful promising techniques that will allow us to reach the era of subpercent precision –but also accuracy– cosmology.

Massive galaxy mock production and the use of Big Data frameworks

• Ismael Ferrero (ITA (University of Oslo) )

The extraction of cosmological parameters from big galaxy surveys is a very complex task. It is indispensable for the creation of synthetic universes to learn how to deal with massive data. The volume needed to be sampled makes it very challenging to implement galaxy formation simulations. Therefore, one solution possible is populating halos from huge dark matter-only simulations with empirical recipes. In this work, I will present the galaxy mocks created for the Euclid consortium. I will detail the different recipes used in the process of assigning properties to galaxies, crucial for testing the robustness of theoretical models. Emphasis will be placed on the big data frameworks that are necessary to generate mocks and data sets of this large magnitude.

Exploring the binomial distribution function in the context of Halo Occupation Distribution models

• Bernhard Vos Ginés (Instituto de Física Teórica (IFT))

Lots of resources and human efforts have been dedicated to constrain the nature of dark matter and dark energy with stage IV cosmological surveys. In particular, galaxies will be used as biased tracers of the total matter present in the Universe. In this work, we use a Halo Occupation Distribution (HOD) model to populate dark matter-only simulations with galaxies adapted to eBOSS Emission-Line Galaxies (ELG) clustering data. Then, we establish a connection between numerical simulations and observations using galaxy clustering, in which those galaxies are used as our dark matter biased tracers. The HOD model makes different assumptions for the distribution of galaxies in haloes, in particular for satellite galaxies. One of these assumptions is the probability to find a given number of satellite galaxies in a halo, that is, its Probability Distribution Function (PDF). In general, a Poisson distribution is assumed but some studies show that for some galaxy samples their PDF may be different. In this work we cover the entire possible range of standard deviations adding the binomial distribution to the set of functions previously used. Furthermore, we also want to measure if the HOD parameters depend on the simulations that we use (in particular, taking into account its different assumed cosmologies). For this purpose we implement our improved HOD model to populate the UNIT (1000Mpc/h side + mp, Planck cosmology) and OuterRim (3000Mpc/h side +mp, WMAP cosmology) DM-only simulations with galaxies. Finally, we use eBOSS ELG clustering data in order to constrain the values of the parameters of our HOD models.

Accelerating theory-based Galaxy Clustering Analysis

• Benjamin Camacho-Quevedo (online) (Institute of Space Sciences (ICE-CSIC))

The study of the large scale structure of the Universe is one of the most robust methods to constrain the current cosmological model. In the very near future we need to be ready to analyse more and better data, from DESI and Euclid surveys. In parallel, the theoretical predictions have also improved to be in line with the quality of data. When it comes to galaxy clustering, the models based on perturbation theory have shown a great performance determining cosmological parameters. Their drawback is that they involve solving complex expressions, which represents a bottleneck in computing time to make statiscal analysis that explore cosmological parameters and test alternative models to LCDM. In order to turn around this difficulties, we have constructed an machine-learning emulator based on the most recent perturbation theory models together with a set of key ideas to minimize the emulation parameter space, while simultaneously keeping the emulator highly flexible, as well as applicable to arbitrary fiducial background cosmologies and a continuous range of redshifts. In this talk we will briefly describe these ideas as well as the design choices. Moreover, we will discuss the achieved precision and summarise some of the most recent results when applying it to measurements of the power spectrum multipoles performed on mock catalogs.

Unveiling the nature of SgrA* with the geodesic motion of S-stars

• Ivan de Martino (Universidad de Salamanca)

We have used publicly available astrometric and spectroscopic measurements of the S0-2 star to constrain the metric around the supermassive object without finding any evidence either favouring or ruling out the wormhole nature. Secondly, we have designed a mock catalogue of future observations of the S0-2 star mirroring the accuracy and precision of GRAVITY. Afterwards, we firstly tested our methodology showing that our procedure recovers the input model, and subsequently we demonstrated that the constraining power of such a dataset is not enough to distinguish between black hole and wormhole. Finally, we built some toy models representing stars orbiting much closer to the central object than S0-2. We used these toy models to investigate which are the ideal orbital features and observational strategies to achieve our aim of unveiling the fundamental nature of the central supermassive object, demonstrating that a star with a period of the order of ~ 5 years and a pericentre distance of ~ 5 AU could identify the nature of the central object at almost 5σ accuracy.

Sudden singularities in f(R,T) gravity

• Tiago Gonçalves (online) (Instituto de Astronomia e Astrofísica e Ciências do Espaço)

Might the universe, one day, undergo a Big Crunch, Big Freeze, Big Rip, or some other singularity? A "sudden singularity" occurs if the energy density, the scale factor and the Hubble function remain finite while there is a divergence in higher derivatives of the scale factor which could be accompanied by a pressure divergence. We investigate whether sudden singularities could arise in the f(R,T) theory of modified gravity. We find that the conservation of matter can prevent sudden singularities in this theory. However, due to matter-geometry couplings, f(R,T) gravity does not require matter conservation. Thus, we investigate a particular model where there is a sudden singularity in the third time derivative of the scale factor.

Robert Hooke's Contributions to a Theory of Universal Gravitation

• Isadora Monteiro (online) (Faculdade de Ciências da Universidade de Lisboa)

Robert Hooke contributed decisively to the development of science in the 17th century. He left us a legacy in astronomy, mechanics, geology, chemistry and even meteorology. This author was forgotten for several decades, partly to the prominence that Isaac Newton, his peer, acquired. The controversy between these two scientists concerning the creation of the Law of Universal Gravitation has been the subject of several studies. In this paper we will revisit the legacy of Robert Hooke, focusing on his contributions for the study of the gravitational force before the Principia were published and known as the masterpiece of science of the seventeenth century.

Announcement of IberiCos 2023 and farewell

• Martin Crocce & Carlos Martins