A5063753925- Radio Astronomy Observations and Technology
- Astronomy and Astrophysical Research
- Galaxies: Formation, Evolution, Phenomena
- Astrophysics and Cosmic Phenomena
- Planetary Science and Exploration
- Stellar, planetary, and galactic studies
- Astrophysical Phenomena and Observations
- Gamma-ray bursts and supernovae
- Astrophysics and Star Formation Studies
- Astronomical Observations and Instrumentation
- Scientific Research and Discoveries
- Space Science and Extraterrestrial Life
- Astro and Planetary Science
- Space Exploration and Technology
- Spacecraft Design and Technology
- Geophysics and Gravity Measurements
- Cosmology and Gravitation Theories
- History and Developments in Astronomy
- Solar and Space Plasma Dynamics
- Superconducting and THz Device Technology
- Antenna Design and Optimization
- Space exploration and regulation
- Radio Wave Propagation Studies
- Spacecraft and Cryogenic Technologies
- Ionosphere and magnetosphere dynamics
University of Colorado Boulder
2016-2025
Laboratory for Atmospheric and Space Physics
2016-2025
Lunar and Planetary Institute
2024
University of Colorado System
2002-2022
Ames Research Center
2011-2015
Solar System Exploration Research Virtual Institute
2009-2014
University of South Florida
2011
Florida College
2011
U.S. National Science Foundation
2009
Michigan State University
2009
A representative sample of 12 extended quasars from the 3CR catalog has been imaged at 4.9 GHz using VLA. These full synthesis observations typically achieve an rms noise 20 µJy per beam, a resolution (FWHM) 0.34" to 0.38". Jets are detected on least one side every source. The jets well collimated compared with those in less powerful sources, but spreading is most them. opening angles several not constant, show recollimation after initial regime rapid spreading. Many contain quasiperiodic...
view Abstract Citations (292) References (66) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The Radio Properties of cD Galaxies in Abell Clusters. I. an X-ray Selected Sample Burns, Jack O. radio and x-ray properties a sample 27 galaxies rich clusters are presented this paper. data consist 6 cm VLA maps at resolution 1-2 arcsec. images surface-brightness profiles from the Einstein IPC, derived quantities such as cooling times, mass-accretion rates, thermal...
view Abstract Citations (192) References (53) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Evaluation of Statistical Tests for Substructure in Clusters Galaxies Pinkney, Jason ; Roettiger, Kurt Burns, Jack O. Bird, Christina M. We use N-body simulations galaxy cluster mergers to evaluate new and published statistical tests substructure. These include 22 one-dimensional (normality) tests, four two-dimensional (spatial) five three-dimensional...
We present an observational analysis of the numerical simulations galaxy custer mergers. identify several signatures recent merger activity and quantitatively assess uncertainty introduced into cluster mass estimates when invoking commonly held assumptions hydrostatic equilibrium, virial spherical symmetry, isothermality. find that mergers result in multiple X-ray peaks, long-lived elongation emission, as well isophotal twisting centroid shifting to a degree consistent with observations....
We investigate empirical scaling relations between the thermal Sunyaev-Zeldovich effect (SZE) and cluster mass in simulated clusters of galaxies. The have been compiled from four different samples that differ only their assumed baryonic physics. show strength SZE integrated over a significant fraction virialized region is relatively insensitive to detailed heating cooling processes cores clusters, by demonstrating derived are nearly identical among considered. For our synthetic images,...
We present new results characterizing cosmological shocks within adaptive mesh refinement N-Body/hydrodynamic simulations that are used to predict non-thermal components of large-scale structure. This represents the first study using refinement. propose a modified algorithm for finding from those on unigrid reduces shock frequency low Mach number by factor ~3. then apply our technique large, (512 Mpc/h)^3, volume and (M) distribution as function pre-shock temperature, density, redshift....
Abstract Most of the current Global 21 cm experiments include ground screens that help moderate effects from Earth. In this paper, we report on a possible systematic artifact within plane may produce broad absorption features in spectra observed by these experiments. Using analytical approximations and numerical modeling, origin its impact sky-averaged spectrum are described. The publicly released EDGES data set, which 78 MHz feature was recently suggested, is used to probe for potential...
Non-thermal radio emission from cosmic-ray electrons in the vicinity of merging galaxy clusters is an important tracer cluster merger activity, and result complex physical processes that involve magnetic fields, particle acceleration, gas dynamics, radiation. In particular, objects known as relics are thought to be shock-accelerated that, when embedded a field, emit synchrotron radiation wavelengths. order properly model this emission, we utilize adaptive mesh refinement simulation...
We present a numerical model for the extended steep-spectrum radio sources and elongated X-ray structure in A3667 based on new three-dimensional MHD/N-body simulations. The optical analyses of indicate that it has undergone recent subcluster merger event. believe Mpc-scale identified are also consequence merger. Our previous simulations show mergers often produce large-scale shocks turbulence capable both magnetic field amplification situ reacceleration relativistic particles. suggests these...
We present results from three-dimensional numerical simulations of head-on mergers between two clusters galaxies using a hybrid hydro/N-body code. In these simulations, the gaseous intracluster medium (ICM) is evolved as massless fluid within changing gravitational potential defined by collisionless dark matter component. The ICM represented equations hydrodynamics which are solved an Eulerian, finite-difference method. cluster component N-body particle distribution. A series have been...
We present initial results from the first three-dimensional numerical magnetohydrodynamical (MHD) simulations of magnetic field evolution in merging clusters galaxies. Within framework idealized conditions similar to our previous work, we look at gas dynamics and during a major merger event order examine suggestion that shocks turbulence generated cluster/subcluster can produce amplification relativistic particle acceleration and, as such, may play role formation cluster-wide radio halos....
view Abstract Citations (194) References (58) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The inner radio structure of Centaurus A : clues to the origin thejet X-ray emission. Burns, J. O. ; Feigelson, E. D. Schreier, Multifrequency (1.4 and 4.9 GHz) observations jet lobes nearby galaxy (= NGC 5128) were made with VLA. These data used construct maps total intensity polarization at resolutions 31arcsec×10arcsec 3arcsec.6×1arcsec.1. distributions surface...
Flux-limited X-ray samples indicate that about half of rich galaxy clusters have cool cores. Why do only some cores while others not? In this paper, cosmological N-body + Eulerian hydrodynamic simulations, including radiative cooling and heating, are used to address question as we examine the formation evolution core (CC) non-cool (NCC) clusters. These adaptive mesh refinement simulations produce both CC NCC in same volume. They a peak resolution 15.6 h^{-1} kpc within (256 Mpc)^3 box. Our...
view Abstract Citations (153) References (10) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Numerical Simulations of a Magnetically Confined Jet Clarke, David A. ; Norman, Michael L. Burns, Jack O. Preliminary results two-dimensional, axisymmetric numerical simulations propagating jet which possesses dominating toroidal magnetic field are presented. Unlike its pure hydrodynamical (HD) counterpart, the magnetohydrodynamical (MHD) presented here no...
Recently, Suzaku has produced temperature and entropy profiles, along with profiles of gas density, fraction, mass, for multiple galaxy clusters out to ~r_200 (~= virial radius). In this paper, we compare these novel X-ray observations results from N-body + hydrodynamic adaptive mesh refinement cosmological simulations using the Enzo code. There is excellent agreement in temperature, between a sample 27 mostly substructure-free massive simulated volume observed clusters. This supports our...
We investigate the predicted present-day temperature profiles of hot, X-ray-emitting gas in galaxy clusters for two cosmological models—a current best-guess ΛCDM model and a standard cold dark matter (SCDM) model. Our numerically simulated catalogs are derived from high-resolution (15 h-1 kpc) simulations which make use sophisticated, Eulerian-based, adaptive mesh-refinement code that faithfully captures shocks essential correctly modeling cluster temperatures. show structure on Mpc scales...
view Abstract Citations (128) References (17) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The Coma Cluster after Lunch: Has a Galaxy Group Passed through the Core? Burns, Jack O. ; Roettiger, Kurt Ledlow, Michael Klypin, Anatoly We propose that cluster has recently undergone collision with NGC 4839 galaxy group. ROSAT X-ray morphology, radio halo, presence of poststarburst galaxies in bridge between and 4839, usually high velocity dispersion for group,...
view Abstract Citations (165) References (46) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS What bends 3C 465 ? Eilek, J. A. ; Burns, O. O'Dea, C. P. Owen, F. N. This paper studies the interaction of prototypical wide-angle tailed radio source with ambient cluster gas. is attached to dominant D galaxy NGC 7720 in Abell 2634. New VLA maps are presented which reveal an inner jet and a rapid change structure at hot spots beginning each tail. X-ray gas also...
Cosmological shocks are a critical part of large-scale structure formation, and responsible for heating the intracluster medium in galaxy clusters. In addition, they capable accelerating non-thermal electrons protons. this work, we focus on acceleration at shock fronts, which is thought to be radio relics—extended features vicinity merging By combining high-resolution adaptive mesh refinement/N-body cosmological simulations with an accurate shock-finding algorithm model electron...
Abstract The redshifted 21 cm monopole is expected to be a powerful probe of the epoch first stars and galaxies ( <?CDATA $10\lt z\lt 35$?> ). global signal sensitive thermal ionization state hydrogen gas thus provides tracer sources energetic photons—primarily hot accreting black holes—which ionize heat high redshift intergalactic medium (IGM). This paper presents strategy for observations spectrum with realizable instrument placed in low-altitude lunar orbit, performing night-time 40–120...
The sky-averaged (global) highly redshifted 21-cm spectrum from neutral hydrogen is expected to appear in the VHF range of $\sim20-200$ MHz and its spectral shape strength are determined by heating properties first stars black holes, nature duration reionization, presence or absence exotic physics. Measurements global signal would therefore provide us with a wealth astrophysical cosmological knowledge. However, has not yet been detected because it must be seen through strong foregrounds...
The assumptions inherent to global 21-cm signal analyses are rarely delineated. In this paper, we formulate a general list of suppositions underlying given claimed detection the signal. Then, specify form these for two different analyses: 1) one performed by EDGES team showing an absorption trough in brightness temperature that they modeled separately from sky foreground and 2) new, so-called Minimum Assumption Analysis (MAA), makes most conservative possible We show fits using analysis on...