José Luis Bernal

¿Qué buscas cuando vas al cine? Que no te quepa duda, buscas emocionarte. Y no importa si vas a ver una película de terror, una comedia romántica, o una película de acción con explosiones. TODAS (con mayúsculas) las películas transmiten emociones, que pueden ir desde el miedo, la tristeza y el aburrimiento, hasta la sorpresa o la alegría. Si ahora te digo que todas las películas tienen ciencia, es muy probable que tu primer pensamiento sea «todas, todas… igual no». TODAS. Créeme. En El Padrino podemos hablar —por ejemplo— de la ciencia en las armas de fuego, o de la biología de los gatos. En Cantando bajo la lluvia, una película musical, tenemos para elegir entre las ondas sonoras y el ciclo del agua. ¿Titanic? Anda que no hay ciencia en un barco... o en el iceberg que lo hundió. Hasta en Ratatouille encontramos ciencia entre los fogones. El cine es un medio fantástico para descubrir cosas que desconocemos, para ver conexiones que nunca nos habríamos planteado. Así, en cada capítulo de este libro partimos de una película para contar un relato sobre la ciencia a la que nos dedicamos. Las películas elegidas son La ventana indiscreta (1954), Contact (1997), Her (2013), Interstellar (2014), Big Hero 6 (2014), Ant-Man (2015), Figuras ocultas (2016), y Tenet (2020). Disfruta.

We present a measurement of the Ly α intensity mapping power spectrum from the Hobby-Eberly Telescope Dark Energy Experiment (HETDEX). We measure the cross-power spectrum of the Ly α intensity and Ly α -emitting galaxies (LAEs) in a redshift range of 1.9 ≤ z ≤ 3.5. We calculate the intensity from HETDEX spectra that do not contain any detected LAEs above a signal-to-noise ratio of 5.5. To produce a power spectrum model and its covariance matrix, we simulate the data using lognormal mocks for the LAE catalog and Ly α intensity in redshift space. The simulations include the HETDEX sensitivity, selection function, and mask. The measurements yield the product of the LAE bias, the intensity bias, the mean intensity of undetected sources, and the ratio of the actual and fiducial redshift-space distortion parameters, b g b I 〈 I 〉 F ¯ RSD / F ¯ RSD fid = (6.7 ± 3.1), (11.7 ± 1.4), and (8.3 ± 1.5) × 10 ⁻²² erg s ⁻¹ cm ⁻² arcsec ⁻² Å ⁻¹ in three redshift bins centered at z ¯ = 2.1 , 2.6, and 3.2, respectively. The results are reasonably consistent with cosmological hydrodynamical simulations that include Ly α radiative transfer. They are, however, significantly smaller than previous results from cross-correlations of quasars with Ly α intensity. These results demonstrate the statistical power of HETDEX for Ly α intensity mapping and pave the way for a more comprehensive analysis. They will also be useful for constraining models of Ly α emission from galaxies used in modern cosmological simulations of galaxy formation and evolution.

Removing contaminants is a delicate, yet crucial step in neutral hydrogen (H I ) intensity mapping and often considered the technique’s greatest challenge. Here, we address this challenge by analysing H I intensity maps of about 100 deg ² at redshift z ≈ 0.4 collected by the MeerKAT radio telescope, an SKA Observatory (SKAO) precursor, with a combined 10.5-hour observation. Using unsupervised statistical methods, we removed the contaminating foreground emission and systematically tested, step-by-step, some common pre-processing choices to facilitate the cleaning process. We also introduced and tested a novel multiscale approach: the data were redundantly decomposed into subsets referring to different spatial scales (large and small), where the cleaning procedure was performed independently. We confirm the detection of the H I cosmological signal in cross-correlation with an ancillary galactic data set, without the need to correct for signal loss. In the best set-up we achieved, we were able to constrain the H I distribution through the combination of its cosmic abundance (Ω _{H  I} ) and linear clustering bias ( b _{H  I} ) up to a cross-correlation coefficient ( r ). We measured Ω _{H  I} b _{H  I} r = [0.93 ± 0.17] × 10 ⁻³ with a ≈6 σ confidence, which is independent of scale cuts at both edges of the probed scale range (0.04 ≲ k ≲ 0.3 h Mpc ⁻¹ ), corroborating its robustness. Our new pipeline has successfully found an optimal compromise in separating contaminants without incurring a catastrophic signal loss. This development instills an added degree of confidence in the outstanding science we can deliver with MeerKAT on the path towards H I intensity mapping surveys with the full SKAO.

We present a novel analysis of observational systematics through the emission-line stacking of the MeerKLASS L-band deep-field intensity maps, following the detection in MeerKLASS Collaboration et al. A stacking signal is obtained by stacking the 21 cm intensity map cubelets around the galaxy positions from the GAMA survey at 0.39 ≲ z ≲ 0.46. An extensive simulation framework is built to study the viability of the stacking detection, the covariance estimation, and the model inference, which are then applied to the data. The statistical significance of the detection is 8.66σ when averaged into an angular map, and 7.45σ when averaged into a spectrum. The stacked spectrum exhibits an oscillating component of systematics, and we provide evidence that these systematics are a convolutional effect on the map data. The oscillation frequency matches the diffraction from the secondary reflector into the primary beam of the MeerKAT telescope. Bayesian inference can be used to constrain the systematics and the average H i emission of the galaxies. The fitting of the parameters gives a constraint on the systematics frequency ν sys [ MHz ] = 17.9 0 − 4.27 + 6.53 . The posterior of the systematics amplitude reaches the wide prior and gives A sys = 0.5 0 − 0.33 + 0.33 . A tentative measurement of the average H i mass of the sources is achieved at log 10 [ 〈 M H I 〉 / M ⊙ ] = 9.8 4 − 0.59 + 0.48 , which is an underestimation limited by the narrow redshift bin, the strong degeneracy with the systematics, and the low-density galaxy sample. These shortfalls will be resolved for future MeerKLASS data to enable accurate measurements of the H i density through stacking of intensity maps.

Erratum: “SIMPLE: Simple Intensity Map Producer for Line Emission” (2023, ApJ, 958, 4), Lujan Niemeyer, Maja, Bernal, José Luis, Komatsu, Eiichiro Erratum: “SIMPLE: Simple Intensity Map Producer for Line Emission” (2023, ApJ, 958, 4), Lujan Niemeyer, Maja, Bernal, José Luis, Komatsu, Eiichiro