A5075316431- Galaxies: Formation, Evolution, Phenomena
- Radio Astronomy Observations and Technology
- Astrophysics and Cosmic Phenomena
- Cosmology and Gravitation Theories
- Astronomy and Astrophysical Research
- Gamma-ray bursts and supernovae
- Astrophysics and Star Formation Studies
- Stellar, planetary, and galactic studies
- Dark Matter and Cosmic Phenomena
- Pulsars and Gravitational Waves Research
- Astrophysical Phenomena and Observations
- Superconducting and THz Device Technology
- Adaptive optics and wavefront sensing
- History and Developments in Astronomy
- Solar and Space Plasma Dynamics
- Antenna Design and Optimization
- Geophysics and Gravity Measurements
- Superconducting Materials and Applications
- Statistical and numerical algorithms
- Particle physics theoretical and experimental studies
- Particle Accelerators and Free-Electron Lasers
- Computational Physics and Python Applications
- Scientific Research and Discoveries
- Spectroscopy and Laser Applications
- Astro and Planetary Science
University of Washington
2015-2024
Seattle University
2016-2018
Institute for Advanced Study
2018
University of Cincinnati
2018
Berkeley College
2011-2015
University of California, Berkeley
2009-2015
Max Planck Institute for Radio Astronomy
2015
Max Planck Society
2015
Albert Einstein College of Medicine
2012
Center for Astrophysics Harvard & Smithsonian
2005-2011
Pinpointing a single fast radio burst Fast bursts (FRBs) are flashes of emission from distant astronomical sources. Two FRBs known to have repeated, but most last just few milliseconds and never seen again. Most telescopes that sensitive poor angular resolutions, so the FRB host galaxies remain unknown. Bannister et al. used dedicated observing mode on interferometer detect localize nonrepeating 180924, then followed up with optical telescope observations (see Perspective by Petroff). They...
A number of radio interferometers are currently being planned or constructed to observe 21 cm emission from reionization. Not only will such measurements provide a detailed view that epoch, but, since the also traces distribution matter in Universe, this signal can be used constrain cosmological parameters at 6 < z 20. The sensitivity an interferometer information may depend on how precisely angular dependence 3-D power spectrum measured. Utilizing analytic model for reionization, we...
It is possible that the properties of HII regions during reionization depend sensitively on many poorly constrained quantities (the nature ionizing sources, clumpiness gas in IGM, degree to which photo-ionizing feedback suppresses abundance low mass galaxies, etc.), making it extremely difficult interpret upcoming observations this epoch. We demonstrate actual situation more encouraging, using a suite radiative transfer simulations, post-processed outputs from 1024^3, 94 Mpc N-body...
The bulk of cosmic matter resides in a dilute reservoir that fills the space between galaxies, intergalactic medium (IGM). history this is intimately tied to histories structure formation, star and supermassive black hole accretion. Our models for IGM at intermediate redshifts (2
A number of experiments are currently working toward a measurement the 21 cm signal from epoch reionization (EoR). Whether or not these deliver detection cosmological emission, their limited sensitivity will prevent them providing detailed information about astrophysics reionization. In this work, we consider what types measurements be enabled by next generation larger EoR telescopes. To calculate type constraints that possible with such arrays, use simple models for instrument, foreground...
The total contribution of diffuse halo gas to the galaxy baryon budget strongly depends on its dominant ionization state. In this paper, we address physical conditions in highly ionized circumgalactic medium (CGM) traced by OVI absorption lines observed COS-Halos spectra. We analyze ionic column densities, absorption-line widths and relative velocities, along with ratios NV/OVI for 39 fitted Voigt profile components OVI. compare these quantities predictions given a wide range models....
We present results from a large volume simulation of hydrogen reionization. combine 3D radiative transfer calculations and an N-body simulation, describing structure formation in the intergalactic medium, to detail growth H II regions around high-redshift galaxies. Our tracks 10243 dark matter particles, box comoving side length 65.6 Mpc h-1. This allows us accurately characterize size distribution throughout most reionization process. At same time, our resolves many small galaxies likely...
There is growing interest in using 3-dimensional neutral hydrogen mapping with the redshifted 21 cm line as a cosmological probe. However, its utility depends on many assumptions. To aid experimental planning and design, we quantify how precision which parameters can be measured broad range of assumptions, focusing signal from $6<z<20$. We cover assumptions related to modeling ionization power spectrum, specifications like array layout detector noise, uncertainties reionization history,...
Observations of the intergalactic medium (IGM) suggest that quasars reionize He ii in IGM at z ≈ 3. We have run a set 190 and 430 comoving Mpc simulations being reionized by to develop an understanding nature reionization its potential impact on observables. find heats regions as much 25, 000 K above temperature is expected otherwise, with volume-averaged increasing ∼12, large fluctuations ∼50 scales. Much this heating occurs far from photons long mean free path. temperature–density equation...
We show that observations of high-redshift Lyα emitters (LAEs) have the potential to provide definitive evidence for reionization in near future. Using 200-Mpc radiative transfer simulations, we calculate effect patchy has on line profile, luminosity function, and, most interestingly, clustering several realistic models reionization. Reionization increases measured emitters, and this enhancement would be essentially impossible attribute anything other than Our results motivate looking...
We compare the predictions of four different algorithms for distribution ionized gas during Epoch Reionization. These are all used to run a 100 Mpc h−1 simulation reionization with same initial conditions. Two state-of-the-art ray-tracing radiative transfer codes that use disparate methods calculate ionization history. The other two fast but more approximate schemes based on iterative applications smoothing filter underlying source and density fields. these algorithms' resulting 21-cm fields...
Telescopes aiming to measure 21cm emission from the Epoch of Reionization must toe a careful line, balancing need for raw sensitivity against stringent calibration requirements removing bright foregrounds. It is unclear what optimal design achieving both these goals. Via pedagogical derivation an interferometer's response power spectrum reionization fluctuations, we show that even under optimistic scenarios, first-generation arrays will yield low-SNR detections, and different compact array...
Recently, Thornton and coworkers (2013) confirmed a class of millisecond radio bursts likely extragalactic origin that is well-suited for estimating dispersion measures (DMs). We calculate the probability distribution DM(z) in different models how cosmic baryons are distributed (both analytically with cosmological simulations). show DM quite sensitive to whether "missing" lie around virial radius 10^11-10^13 Msun halos or further out, which not easily constrained other observational...
We forecast the sensitivity with which Murchison Widefield Array (MWA) can measure 21 cm power spectrum of cosmic hydrogen, using radiative transfer simulations to model reionization and signal. The MWA is sensitive roughly a decade in scale (wavenumbers k ~ 0.1 - 1 h Mpc^{-1}), foreground contamination precluding measurements on larger scales, thermal detector noise limiting small sensitivity. This amounts primarily constraints two numbers: amplitude slope scales probed. find, however, that...
We study the properties of self-shielding intergalactic absorption systems and their implications for ionizing background. find that cosmological simulations post-processed with detailed radiative transfer calculations generally are able to reproduce observed abundance Lyman-limit systems, we highlight possible discrepancies between observations simulations. This comparison tests at overdensities ∼100. Furthermore, show in these simulations, simple semianalytic arguments, as suggested by...
Probing a galaxy halo with radio burst Fast bursts (FRBs) are millisecond flashes of emission from distant galaxies. It has only recently become possible to locate single precisely enough determine the host galaxy. Prochaska et al. have observed and localized FRB using interferometer. The line sight coincidentally passes through outskirts closer foreground By analyzing propagation FRB, authors put constraints on density magnetization gas in technique provides complementary information...
Recent observations have shown that the scatter in opacities among coeval segments of Lyman-alpha forest increases rapidly at z > 5. In this paper, we assess whether large can be explained by fluctuations ionizing background post-reionization intergalactic medium. We find matching observed ~ 5.5 requires a short spatially averaged mean free path < 15 comoving Mpc/h, factor 3 shorter than direct measurements 5.2. argue such rapid evolution is difficult to reconcile with our global H I...
ABSTRACT We measure the effective optical depth of He ii Ly α absorption <?CDATA ${\tau }_{\mathrm{eff},\mathrm{He}{\rm{II}}}$?> at $2.3\lt z\lt 3.5$?> in 17 UV-transmitting quasars observed with UV spectrographs on Hubble Space Telescope . The median values increase gradually from 1.95 $z=2.7$?> to $5.17$?> $z=3.4$?> , but a strong sightline-to-sightline variance. Many $\simeq 35$?> comoving Mpc regions $z\gt 3$?> intergalactic medium (IGM) remain transmissive (...
We examine the constraints on soft X-ray emissions from reionization era. It has generally been assumed that Universe was reionized by ultraviolet photons massive stars. However, it argued associated with death of these stars would have contributed ~10% to total ionizations via several channels. The parameter space for a significant component cosmological be sourced X-rays is limited few observations. revisit unresolved background constraint and show significantly limits contribution...
We investigate how well the redshift distribution of a population extragalactic objects can be reconstructed using angular cross-correlations with sample whose redshifts are known. derive minimum variance quadratic estimator, which has simple analytic representations in very applicable limits and is significantly more sensitive than earlier proposed estimation procedures. This estimator straightforward to apply observations, it robustly finds likelihood maximum, conveniently selects scales...
Many recent studies have highlighted certain failures of the standard Eulerian-space cosmological perturbation theory (SPT). Its problems include (1) not capturing large-scale bulk flows [leading to an ( 1) error in 1-loop SPT prediction for baryon acoustic peak correlation function], (2) assuming that Universe behaves as a pressureless, inviscid fluid, and (3) treating fluctuations on scales are non-perturbative if they were. Recent successes Lagrangian space or theories solve equations...
The axion, motivated as a solution to the strong $CP$ problem, is also viable dark matter candidate. axion field takes random values in causally disconnected regions if symmetry breaking that establishes particle occurs after inflation, leading white-noise density fluctuations at low wave numbers and forming dense minihalos with sub-planetary masses subsequently. There have been two recent proposals appear capable of testing this scenario, namely using pulsar timing arrays studying...
The authors propose a novel method to probe potential Dark Matter substructures by means of Fast Radio Burst (FRB) observations. They discuss two observational scenarios, as well experimental setups and challenges.
During the epoch of reionization, local variations in ionized fraction (patchiness) imprint arcminute-scale temperature anisotropies CMB through kinetic Sunyaev-Zel'dovich (kSZ) effect. We employ an improved version analytic model reionization devised by Furlanetto and coworkers to calculate kSZ anisotropy from patchy reionization. This uses extended Press-Schechter theory determine distribution evolution H II bubbles produces qualitatively similar histories those seen recent numerical...