Enrique Martinez-Gonzalez

The Cosmic Microwave Background (CMB) carries crucial information about the origin and evolution of the Universe, with its polarization patterns providing potential evidence of primordial gravitational waves. Achieving the precision required for these measurements demands highly accurate calibration methods. This study presents the development of a reference signal source to be integrated as the payload of LEO-CalSat, a Low-Earth Orbit satellite designed to serve as an artificial, far-field calibration tool for ground-based CMB polarization experiments. The system aims both to validate the technological readiness of a compact calibration payload for future L2 missions and to provide reference signals in the W-band (75–110 GHz) for current observatories. The calibration source, integrated within the volume of a CubeSat’s 2 U, was designed to balance miniaturization with performance, incorporating key components such as a frequency multiplier with a Voltage-Controlled Oscillator, horn antenna, and polarizer. Laboratory tests demonstrated fully polarized emission with output powers up to 6 dBm and a signal-to-noise ratio of approximately 30 dB, confirming the feasibility of precise polarization calibration. The reduced mass and power consumption (1 kg, 9 W) ensure compatibility with CubeSat constraints. The results validate the core concept and readiness of LEO-CalSat for space operation, representing a significant step toward establishing standardized, space-based calibration for future CMB missions and advancing precision cosmology.

Upcoming cosmic microwave background (CMB) experiments aim to detect primordial gravitational waves with unprecedented sensitivity. Effective foreground removal is essential to avoid biases in the measurement of the tensor-to-scalar ratio ( r ) in this high-precision regime. Recent analyses highlight the unexpected complexity of synchrotron emission at low frequencies, underscoring the need for more sensitive low-frequency data. To address this challenge, the European Low-Frequency Survey (ELFS) initiative and the Simons Array collaboration propose installing two European low-frequency receivers on one of the Simons Array telescopes. These receivers will enable measurements in the Southern Hemisphere between 6 and 20 GHz, complementary to those of current and proposed experiments targeting the measurement of cosmological gravitational waves. In this work, we study the benefits of combining these low-frequency observations with a representative future CMB experiment operating from the Southern Hemisphere. We find that the extra information can improve the knowledge of the underlying synchrotron spectral energy distribution (SED), with positive impacts on the robustness of measurement of the tensor-to-scalar ratio, r , against the complexity of low-frequency foregrounds.

Anomalous Microwave Emission (AME) is a diffuse microwave component thought to arise from spinning dust grains, though it remains poorly understood. We analyzed AME in 144 Galactic clouds by combining low-frequency maps from S-PASS (2.3 GHz), C-BASS (4.76 GHz), and QUIJOTE (10–20 GHz) with 21 ancillary maps. Using aperture photometry and parametric spectral energy distribution (SED) fitting via Markov chain Monte Carlo methods without informative priors, we measured AME emissivity, peak frequency, and spectral width. We achieved peak frequency constraints nearly three times tighter than previous work and identify 83 new AME sources. The AME spectra are generally broader than predicted by spinning dust models for a single phase of the interstellar medium, suggesting either multiple spinning dust components along the line of sight or incomplete representation of the grain size distribution in current models. However, the narrowest observed widths match theoretical predictions, supporting the spinning dust hypothesis. The AME amplitude correlates most strongly with the thermal dust peak flux and radiance, showing ∼30% scatter and sublinear scaling, which suggests reduced AME efficiency in regions with brighter thermal dust emission. The AME peak frequency increases with thermal dust temperature in a trend current theoretical models do not reproduce, indicating that spinning dust models must incorporate dust evolution and radiative transfer in a self-consistent framework where environmental parameters and grain properties are interdependent. Polycyclic aromatic hydrocarbon tracers correlate with AME emissivity, supporting a physical link to small dust grains. Finally, a log-Gaussian function provides a good empirical description of the AME spectrum across the sample, given current data quality and frequency coverage.

We introduce a novel approach to estimate the spectral index, β _s , of polarised synchrotron emission, combining the moment expansion of Cosmic Microwave Background foregrounds and the constrained Internal Linear Combination method. We reconstructed the maps of the first two synchrotron moments, combining multi-frequency data, and applied the ‘T-T plot’ technique between two moment maps to estimate the synchrotron spectral index. This approach offers a new technique for mapping the foreground spectral parameters, complementing the model-based parametric component separation methods. Applying this technique, we derived a new constraint on the spectral index of polarised synchrotron emission using QUIJOTE MFI wide-survey 11 and 13 GHz data, Wilkinson Microwave Anisotropy Probe data at K and Ka bands, and Planck LFI 30 GHz data. In the Galactic plane and North Polar Spur regions, we obtained an inverse-variance-weighted mean synchrotron index of β _s = −3.11 with a standard deviation of 0.21 due to intrinsic scatter, consistent with previous results based on parametric methods using the same dataset. We find that the inverse-variance-weighted mean spectral index, including both statistical and systematic uncertainties, is β _s ^plane = −3.05 ± 0.01 in the Galactic plane and β _s ^high-lat = −3.13 ± 0.02 at high latitudes, indicating a moderate steepening of the spectral index from low to high Galactic latitudes. Our analysis indicates that, within the current upper limit on the Anomalous Microwave Emission polarisation fraction, our results are not subject to any appreciable bias. Furthermore, we infer the spectral index over the entire QUIJOTE survey region, partitioning the sky into 21 patches. This technique can be further extended to constrain the synchrotron spectral curvature by reconstructing higher-order moments when better-quality data become available.

We investigate the capability of the J-PAS survey to constrain the primordial power spectrum using a non-parametric Bayesian method. Specifically, we analyze simulated power spectra generated by an oscillatory primordial feature template motivated by non-standard inflation. The feature is placed within the range of scales where the signal-to-noise ratio is maximized, and we restrict the analysis to k ∈ [0.02,0.2] h Mpc ^-1 , set by the expected J-PAS coverage and the onset of non-linear effects. Each primordial power spectrum is reconstructed by linearly interpolating N knots in the {log k , log P _Rscr; ( k )} plane, which are sampled jointly with the cosmological parameters { H ₀ ,Ω _b h ² , Ω _c h ² } using PolyChord. To test the primordial features, we apply two statistical tools: the Bayes factor and a hypothesis test that localizes the scales where features are detected. We assess the recovery under different J-PAS specifications, including redshift binning, tracer type, survey area, and filter strategy. Our results show that combining redshift bins and tracers allows the detection of oscillatory features as small as 2%.

Various so-called anomalies have been found in both the WMAP and Planck cosmic microwave background (CMB) temperature data that exert a mild tension against the highly successful best-fit 6 parameter cosmological model, potentially providing hints of new physics to be explored. That these are real features on the sky is uncontested. However, given their modest significance, whether they are indicative of true departures from the standard cosmology or simply statistical excursions due to a mildly unusual configuration of temperature anisotropies on the sky which we refer to as the “fluke hypothesis” cannot be addressed further without new information. No theoretical model of primordial perturbations has to date been constructed that can explain all of the temperature anomalies. Therefore, we focus in this paper on testing the fluke hypothesis, based on the partial correlation between the temperature and E -mode CMB polarisation signal. In particular, we compare the properties of specific statistics in polarisation, built from unconstrained realisations of the ΛCDM cosmological model as might be observed by the LiteBIRD satellite, with those determined from constrained simulations, where the part of the E -mode anisotropy correlated with temperature is constrained by observations of the latter. Specifically, we use inpainted Planck 2018 SMICA temperature data to constrain the E -mode realisations. Subsequent analysis makes use of masks defined to minimise the impact of the inpainting procedure on the E -mode map statistics. We find that statistical assessments of the E -mode data alone do not provide any evidence for or against the fluke hypothesis. However, tests based on cross-statistical measures determined from temperature and E modes can allow this hypothesis to be rejected with a moderate level of probability.

The origin of small deviations from statistical isotropy in the Cosmic Microwave Background (CMB) — the so-called CMB anomalies — remains an open question in modern cosmology. In this work, we test statistical isotropy in Planck Data Release 4 (PR4) by estimating the temperature and E -mode power spectra across independent sky regions. We find that the directions with higher local bandpower amplitudes in intensity are clustered for multipoles between 200 and 2000 with clustering probabilities consistently below 1% for all these scales when compared to end-to-end (E2E) Planck simulations; notably, this range extends beyond that reported in Planck Data Release 3 (PR3). On the other hand, no significant clustering is observed in the polarisation E -modes. In a complementary analysis, we search for dipolar variations in cosmological parameters fitted using the previously computed power spectra. When combining temperature and polarisation power spectra, we identify a potential anomaly in the amplitude of the primordial power spectrum, A _s , with only 5 out of 600 simulations exhibiting a dipole amplitude as large as that observed in the data. Interestingly, the dipole direction aligns closely with the known hemispherical power asymmetry, suggesting a potential link between these anomalies. All other cosmological parameters remain consistent with ΛCDM expectations. Our findings highlight the need to further investigate these anomalies and understand their nature and potential implications for better understanding of the early Universe.

Recent observations have indicated a Cosmic Microwave Background (CMB) temperature decrement in the direction of local galaxies within the 2MASS Redshift Survey. We investigate this detection by analyzing its frequency dependence and sensitivity to component separation methods, suggesting that Galactic foregrounds are unlikely to be the cause. Contrary to previous studies, we find that the decrement is independent of galaxy type, indicating a possible correlation between the CMB and the overall matter density field. To test this hypothesis, we employ three analytical approaches: cross-correlation analysis, template fitting, and Bayes Factor calculation. Our analyses consistently reveal a moderate correlation (with significance levels in the 1% – 5% range) between the CMB and the 2MASS Redshift Survey projected matter density at distances below 50 Mpc/h. Importantly, we do not detect this signal beyond 50 Mpc/h, which constrains potential physical interpretations and suggests caution regarding possible look-elsewhere effects in our analysis. We discuss that the physical origin of this correlation could potentially be linked to the dark matter distribution in the halos of galaxies. Further investigation is required to confirm and understand this intriguing connection between the CMB and local matter distribution.

The presence of astrophysical emissions in microwave observations forces us to perform component separation to extract the Cosmic Microwave Background (CMB) signal. However, even in the most optimistic cases, there are still strongly contaminated regions, such as the Galactic plane or those with emission from extragalactic point sources, which require the use of a mask. Since many CMB analyses, especially the ones working in harmonic space, need the whole sky map, it is crucial to develop a reliable inpainting algorithm that replaces the values of the excluded pixels by others statistically compatible with the rest of the sky. This is especially important when working with Q and U sky maps in order to obtain E- and B-mode maps which are free from E-to-B leakage. In this work we study a method based on Gaussian Constrained Realizations (GCR), that can deal with both intensity and polarization. Several tests have been performed to asses the validation of the method, including the study of the one-dimensional probability distribution function (1-PDF), E- and B-mode map reconstruction, and power spectra estimation. We have considered two scenarios for the input simulation: one case with only CMB signal and a second one including also Planck PR4 semi-realistic noise. Even if we are limited to low resolution maps, N_side = 64 if T, Q and U are considered, we believe that this is a useful approach to be applied to future missions such as LiteBIRD, where the target are the largest scales.