Engineering topics

Ruiz-Lapuente, Pilar

Publications and source records attributed to Ruiz-Lapuente, Pilar.

4 records

DOE OSTI2025

Union through UNITY: Cosmology with 2000 SNe Using a Unified Bayesian Framework

Type Ia supernovae (SNe Ia) were instrumental in establishing the acceleration of the Universe’s expansion. By virtue of their combination of distance reach, precision, and prevalence, they continue to provide key cosmological constraints, complementing other cosmological probes. Individual SN surveys cover only over about a factor of 2 in redshift, so compilations of multiple SN data sets are strongly beneficial. We assemble an up-to-date “Union” compilation of 2087 cosmologically useful SNe Ia from 24 data sets (“Union3”). We take care to put all SNe on the same distance scale and update the light-curve fitting with SALT3 to use the full rest-frame optical. Over the next few years, the number of cosmologically useful SNe Ia will increase by more than a factor of 10, and keeping systematic uncertainties subdominant will be more challenging than ever. We discuss the importance of treating outliers, selection effects, light-curve shape/color populations/standardization relations, unexplained dispersion, and heterogeneous observations simultaneously. We present an updated Bayesian framework, called UNITY1.5 (Unified Nonlinear Inference for Type-Ia cosmologY), that incorporates significant improvements in our ability to model selection effects, standardization, and systematic uncertainties compared to earlier analyses. As an analysis byproduct, we also recover the posterior of the SN-only peculiar-velocity field, although we do not interpret it in this work. We compute updated cosmological constraints with Union3 and UNITY1.5, finding weak 1.7σ–2.6σ tension with flat cold dark matter and possible evidence for thawing dark energy (w0 > − 1, wa < 0). We release our SN distances, light-curve fits, and UNITY1.5 framework to the community.

Rubin, David↗

DOE OSTI2021

The growth of density perturbations in the last ~10 billion years from tomographic large-scale structure data

In order to investigate the origin of the ongoing tension between the amplitude of matter fluctuations measured by weak lensing experiments at low redshifts and the value inferred from the cosmic microwave background anisotropies, we reconstruct the evolution of this amplitude from z ~ 2 using existing large-scale structure data. To do so, we decouple the linear growth of density inhomogeneities from the background expansion, and constrain its redshift dependence making use of a combination of 6 different data sets, including cosmic shear, galaxy clustering and CMB lensing. We analyze these data under a consistent harmonic-space angular power spectrum-based pipeline. We show that current data constrain the amplitude of fluctuations mostly in the range 0.2 < z < 0.7, where it is lower than predicted by . This difference is mostly driven by current cosmic shear data, although the growth histories reconstructed from different data combinations are consistent with each other, and we find no evidence of systematic deviations in any particular experiment. In spite of the tension with , the data are well-described by the model, albeit with a lower value of S 8 ≡ σ 8 (Ω m /0.3) 0.5 . As part of our analysis, we find constraints on this parameter of S 8 = 0.7781 ± 0.0094 (68% confidence level), reaching almost percent-level errors comparable with CMB measurements, and 3.4σ away from the value found by .

79 ASTRONOMY AND ASTROPHYSICS↗

DOE OSTI2020

Gamma-Rays from Kilonovae and the Cosmic Gamma-Ray Background

The recent detection of the gravitational-wave event GW170817, produced by the coalescence of two neutron stars, and of its optical–infrared counterpart, powered by the radioactive decay of r-process elements, has opened a new window onto gamma-ray astronomy: the direct detection of photons coming from such decays. In this work, we calculate the contribution of kilonovae to the diffuse gamma-ray background in the MeV range, using recent results on the spectra of the gamma-rays emitted in individual events, and we compare it with that from other sources. We find that the contribution from kilonovae is not dominant in such an energy range, but within current uncertainties, and its addition to other sources might help to fit the observational data.

59 BASIC BIOLOGICAL SCIENCES↗

NASA NTRS1994

SN 1991T: Reflections of past glory

We have obtained photometry and spectra of SN 1991T which extend more than 1000 days past maximum light, by far the longest of SN Ia has been followed. Although SN 1991T exhibited nearly photometric behavior in the first 400 days following maximum, by 600 days its decline had slowed, and by 950 days the supernova brightness was consistent with a constant apparent magnitude of m(sub B) = 21.30. Spectra near maximum showed minor variations on the SN Ia theme which grew less conspicuous during the exponential decline. At 270 days the nebular spectrum was composed of Fe and Co lines common to SN Ia. However, by 750 days past maximum light, these lines had shifted in wavelength, and were superposed on a strong blue continuum. The luminosity of SN 1991T at 950 days is more than (9.0 x 10(exp 38)(D/13 Mpc)(2) ergs/s with a rate of decline of less than 0.04 mag per 100 days. We show that this emission is likely to be light that was emitted by SN 1991T near maximum light which has reflected from foreground dust, much like the light echos observed around SN 1987A.

Schmidt, Brian P.↗