A5033360598- Cosmology and Gravitation Theories
- Astronomy and Astrophysical Research
- Dark Matter and Cosmic Phenomena
- Gamma-ray bursts and supernovae
- Galaxies: Formation, Evolution, Phenomena
- Stellar, planetary, and galactic studies
- Astrophysics and Cosmic Phenomena
- Adaptive optics and wavefront sensing
- Pulsars and Gravitational Waves Research
- Black Holes and Theoretical Physics
- Gaussian Processes and Bayesian Inference
- Solar and Space Plasma Dynamics
- Computational Physics and Python Applications
- Scientific Research and Discoveries
- Particle physics theoretical and experimental studies
- History and Developments in Astronomy
- Radio Astronomy Observations and Technology
- Advanced Thermodynamics and Statistical Mechanics
- Cultural Differences and Values
- Data Quality and Management
- Statistical Methods and Inference
- Astro and Planetary Science
- Probability and Statistical Research
- Geological and Geophysical Studies
- Pacific and Southeast Asian Studies
University of California, Merced
2022-2024
Korea Astronomy and Space Science Institute
2019-2023
Korea University of Science and Technology
2022
University of California, Irvine
2014-2020
UC Irvine Health
2015
Abstract Gaussian processes have been widely used in cosmology to reconstruct cosmological quantities a model-independent way. However, the validity of adopted mean function and hyperparameters, dependence results on choice not well explored. In this paper, we study effects underlying hyperparameter selection reconstruction distance moduli from type Ia supernovae. We show that an arbitrary affects reconstruction: zero leads unphysical best-fit ΛCDM biased reconstructions. propose marginalize...
Self-interacting dark matter (SIDM) models have been proposed to solve the small-scale issues with collisionless cold paradigm. We derive equilibrium solutions in these SIDM for halo density profile including gravitational potential of both baryons and matter. Self-interactions drive be isothermal this ties core sizes shapes halos spatial distribution stars, a radical departure from previous expectations predictions. Compared predictions SIDM-only simulations, are smaller densities higher,...
We make the case that there can be no low-redshift solution to ${H}_{0}$ tension. To robustly answer this question, we use a very flexible parametrization for dark energy equation of state such every cosmological distance still allowed by data exists within prior volume. then whether satisfactory tension comprehensive parametrization, constrained parametric form using different partitions Planck cosmic microwave background, SDSS-IV/eBOSS DR16 baryon acoustic oscillation, and Pantheon...
Abstract Absolute distances from strong lensing can anchor Type Ia Supernovae (SNe Ia) at cosmological giving a model-independent inference of the Hubble constant ( H 0 ). Future observations could provide time-delay with source redshifts up to z ≃ 4, which are much higher than maximum redshift SNe observed so far. In order make full use measured redshifts, we quasars as complementary cosmic probe measure beyond those and method determine . this work, demonstrate model-independent, joint...
The extended excess toward the Galactic Center (GC) in gamma rays inferred from Fermi-LAT observations has been interpreted as being due to dark matter (DM) annihilation. Here, we perform new likelihood analyses of GC and show that, when including templates for stellar galactic nuclear bulges, shows no significant detection a DM annihilation template, even after generous variations diffuse emission models wide range halo profiles. We include with combinations three-dimensional inverse...
We determine the Hubble constant $H_0$ precisely ($2.3\%$ uncertainty) in a manner independent of cosmological model through Gaussian process regression, using strong lensing and supernova data. Strong gravitational variable source can provide time-delay distance $D_{\Delta t}$ angular diameter to lens $D_{\rm{d}}$. These absolute distances anchor Type Ia supernovae, which give an excellent constraint on shape distance-redshift relation. Updating our previous results use H0LiCOW program's...
Our current understanding of the Universe is established through pristine measurements structure in cosmic microwave background (CMB) and distribution shapes galaxies tracing large scale (LSS) Universe. One key ingredient that underlies cosmological observables field sources observed assumed to be initially Gaussian with high precision. Nevertheless, a minimal deviation from Gaussianityis perhaps most robust theoretical prediction models explain Universe; itis necessarily present even...
Inflation may provide unique insight into the physics at highest available energy scales that cannot be replicated in any realistic terrestrial experiment. Features primordial power spectrum are generically predicted a wide class of models inflation and its alternatives, observationally one most overlooked channels for finding evidence non-minimal inflationary models. Constraints from observations cosmic microwave background cover widest range feature frequencies, but sensitive constraints...
We test the mutual consistency between baryon acoustic oscillation measurements from eBOSS SDSS final release, as well Pantheon supernova compilation in a model independent fashion using Gaussian process regression. also their joint with $\Lambda$CDM model, fashion. use regression to reconstruct expansion history that is preferred by these two datasets. While this methodology finds no significant preference for flexibility beyond $\Lambda$CDM, we are able generate number of reconstructed...
ABSTRACT The flux ratios of gravitationally lensed quasars provide a powerful probe the nature dark matter. Importantly, these are sensitive to small-scale structure, irrespective presence baryons. This sensitivity may allow us study halo mass function even below scales where galaxies form observable stars. For accurate measurements, it is essential that quasar’s light emitted from physical region quasar with an angular scale milliarcseconds or larger; this minimizes microlensing effects by...
A ``crisis in cosmology'' is lurking recent measurements of the Hubble constant ${H}_{0}$ (the current expansion rate Universe), caused by a tension between direct observations through distance and an inferred value, computed with standard model cosmology ($\mathrm{\ensuremath{\Lambda}}$CDM) from CMB data. The latter involves approx. 13 billion years time evolution. authors use statistical methods to analyze different available data sets kind that carry information about moments evolution...
We incorporate Milky Way dark matter halo profile uncertainties, as well an accounting of diffuse gamma-ray emission uncertainties in annihilation models for the Galactic Center Extended excess (GCE) detected by Fermi Gamma Ray Space Telescope. The range particle rate and masses expand when including these unknowns. However, two most precise empirical determinations halo's local density leave signal region to be considerable tension with searches from combined dwarf galaxy analyses...
The hot dense environment of the early universe is known to have produced large numbers baryons, photons, and neutrinos. These extreme conditions may also other long-lived species, including new light particles (such as axions or sterile neutrinos) gravitational waves. effects any such relics can be observed through their unique imprint in cosmic microwave background (CMB), large-scale structure, primordial element abundances, are important determining initial universe. We argue that future...
We explore the implications of a rapid appearance dark energy between redshifts ($z$) one and two on expansion rate growth perturbations. Using both Gaussian process regression parameteric model, we show that this is preferred solution to current set low-redshift ($z<3$) distance measurements if $H_0=73~\rm km\,s^{-1}\,Mpc^{-1}$ within 1\% high-redshift history unchanged from $\Lambda$CDM inference by Planck satellite. Dark was effectively non-existent around $z=2$, but its density close...
In this paper, we present a model-independent approach to calibrate the largest quasar sample. Calibrating samples is essentially constraining parameters of linear relation between $\log$ ultraviolet (UV) and X-ray luminosities. This calibration allows quasars be used as standardized candles. There strong correlation characterizing luminosity cosmological distances inferred from using We break degeneracy by Gaussian process regression model-independently reconstruct expansion history...
In this paper we explore the existing tensions in local cosmological expansion rate, ${H}_{0}$, and amplitude of clustering large-scale structure at $8{h}^{\ensuremath{-}1}\text{ }\text{ }\mathrm{Mpc}$, ${\ensuremath{\sigma}}_{8}$, as well models that claim to alleviate these tensions. We consider seven models: evolving dark energy ($w\mathrm{CDM}$), extra radiation (${N}_{\mathrm{eff}}$), massive neutrinos, curvature, primordial magnetic fields (PMF), self-interacting neutrino models, early...
Gravitationally lensed supernovae (glSNe) are a powerful tool for exploring the realms of astronomy and cosmology. Time-delay measurements lens modeling glSNe can provide robust independent method constraining expansion rate universe. The study unresolved light curves presents unique opportunity utilizing small telescopes to investigate these systems. In this work, we diverse observational strategies initial detection using 7-Dimensional Telescope (7DT), multi-telescope system composed...
The study of dark matter substructure through strong gravitational lensing has shown enormous promise in probing the properties on sub-galactic scales. This approach already been used to place constraints a wide range models including self-interacting matter, fuzzy and warm matter. A major source degeneracy exists between suppression low mass halos due novel physics strength tidal stripping experienced by subhalos. We theoretical predictions for statistical subhalos lenses using...
In this study, we use a flexible parametrization of the equation state dark energy to explore its possible evolution with datasets from Dark Energy Spectroscopic Instrument (DESI), Planck cosmic microwave background, and either 5-year Survey (DES) or Pantheon+ (PP) supernova (SN) compilation. This parametrization, called transitional energy, allows for rapid changes in but also like that Chevallier-Polarski-Linder parametrization. We find 3.8{\sigma} preference evolving over {\Lambda}CDM DES...
Strongly lensed quasar systems with time delay measurements provide "time distances", which are a combination of three angular diameter distances and serve as powerful tools to determine the Hubble constant $H_0$. However, current results often rely on assumption $\Lambda$CDM model. Here we use model-independent method based Gaussian process directly constrain value By using regression, can generate posterior samples unanchored supernova independent any cosmological model anchor them strong...
We explore a class of primordial power spectra that can fit the observed anisotropies in cosmic microwave background well and predicts value for Hubble parameter consistent with local measurement $H_0 = 74$ km/s/Mpc. This spectrum consists continuous deformation between best-fit law derived from modified Richardson-Lucy deconvolution algorithm applied to $C_\ell$s spectrum. find linear interpolation half-way fits Planck data better than $\Lambda$CDM by $\Delta\log\mathcal{L} 2.5$. In effect,...
ABSTRACT This is the second in a series of papers which we use JWST Mid Infrared Instrument multiband imaging to measure warm dust emission sample 31 multiply imaged quasars, be used as probe particle nature dark matter. We present measurements relative magnifications strongly lensed nine systems. The region compact and sensitive perturbations by populations haloes down masses $\sim 10^6$ M$_{\odot }$. Using these flux-ratio combination with five previous narrow-line measurements, constrain...
ABSTRACT Accurate estimation of the Hubble constant, and other cosmological parameters, from distances measured by cosmic gravitational wave sirens requires sufficient allowance for dark energy evolution. We demonstrate how model-independent statistical methods, specifically Gaussian process regression, can remove bias in reconstruction H(z), be combined to model independently with supernova distances. This allows stringent tests both H0 Λ cold matter, detect unrecognized systematics. also...
We have developed a frequentist approach for model selection which determines the consistency between any cosmological and data using distribution of likelihoods from iterative smoothing method. Using this approach, we shown how confidently can conclude whether support given without comparison to different one. In current work, compare our with conventional Bayesian based on estimation evidence nested sampling. use simulated future Roman (formerly WFIRST)-like type Ia supernovae in analysis....