A5003918379- Galaxies: Formation, Evolution, Phenomena
- Stellar, planetary, and galactic studies
- Astronomy and Astrophysical Research
- Astrophysics and Star Formation Studies
- Astro and Planetary Science
- Gamma-ray bursts and supernovae
- Cosmology and Gravitation Theories
- Astrophysical Phenomena and Observations
- Scientific Research and Discoveries
- Planetary Science and Exploration
- Dark Matter and Cosmic Phenomena
- Astrophysics and Cosmic Phenomena
- Astronomical Observations and Instrumentation
- Solar and Space Plasma Dynamics
- Distributed and Parallel Computing Systems
- Radio Astronomy Observations and Technology
- Geophysics and Gravity Measurements
- Parallel Computing and Optimization Techniques
- Computational Physics and Python Applications
- Pulsars and Gravitational Waves Research
- Black Holes and Theoretical Physics
- Advanced Data Storage Technologies
- Spacecraft and Cryogenic Technologies
- Adaptive optics and wavefront sensing
- Algorithms and Data Compression
University of Washington
2015-2024
Lawrence Livermore National Laboratory
2024
University of Oslo
2021
Planetary Science Institute
2018-2020
Polar (Finland)
2018-2020
Max Planck Institute for Astronomy
2019
Max Planck Society
2019
NASA Astrobiology Institute
2015-2018
University of California, Berkeley
2002-2016
Seattle University
1997-2015
We use numerical simulations to examine the substructure within galactic and cluster mass halos that form a hierarchical universe. Clusters are easily reproduced with steep spectrum of thousands clumps closely matches observations. However, survival dark matter also occurs on scales, leading remarkable result galaxy appear as scaled versions clusters. The model predicts virialized extent Milky Way's halo should contain about 500 satellites circular velocities larger than Draco Ursa Minor...
We describe the algorithm that selects main sample of galaxies for spectroscopy in Sloan Digital Sky Survey from photometric data obtained by imaging survey. Galaxy properties are measured using Petrosian magnitude system, which measures flux apertures determined shape surface brightness profile. The metric aperture used is essentially independent cosmological dimming, foreground extinction, sky brightness, and galaxy central brightness. consists with r-band r < 17.77 half-light 24.5...
We show that a universe dominated by cold dark matter fails to reproduce the rotation curves of galaxies, one key problems it was designed resolve. perform numerical simulations formation haloes, each containing ≳106 particles and resolved 0.003 times virial radius, allowing an accurate comparison with curve data. A good fit both Galactic cluster-sized haloes can be achieved using density profile ρ(r)∝[(rrs)1.5(1+(rrs)1.5)]−1, where rs is scale radius. This has steeper asymptotic slope,...
Using a catalog of 147,986 galaxy redshifts and fluxes from the Sloan Digital Sky Survey (SDSS), we measure luminosity density at z = 0.1 in five optical bandpasses corresponding to SDSS shifted match their rest-frame shape 0.1. We denote bands 0.1u, 0.1g, 0.1r, 0.1i, 0.1z with λeff (3216, 4240, 5595, 6792, 8111 Å), respectively. To estimate function, use maximum likelihood method that allows for general form fits simple number evolution, incorporates flux uncertainties, accounts limits...
We investigate the mass profile of LambdaCDM halos using a suite numerical simulations spanning five decades in halo mass, from dwarf galaxies to rich galaxy clusters. Our analysis confirms proposal Navarro, Frenk & White (NFW) that shape profiles differs strongly power law and depends little on mass. The logarithmic slope spherically-averaged density profile, as measured by beta=-dln(rho)/dln(r), decreases monotonically towards center becomes shallower than isothermal (beta<2) inside...
We present a comprehensive set of convergence tests which explore the role various numerical parameters on equilibrium structure simulated dark matter halo. report results obtained with two independent, state-of-the-art, multi-stepping, parallel N-body codes: pkdgrav and gadget. find that convergent mass profiles can be for suitable choices gravitational softening, time-step, force accuracy, initial redshift, particle number. For softenings chosen so discreteness effects are negligible, in...
We examine the effects of mass resolution and force softening on density profiles cold dark matter halos that form within cosmological N-body simulations. As we increase resolution, resolve progenitor collapse at higher redshifts have very high densities. At our highest nearly 3×106 particles virial radius, which is several orders magnitude more than previously used, can 1000 surviving this single virialized system. The halo become steeper in central regions, may not achieved convergence to...
In the course of its commissioning observations, Sloan Digital Sky Survey (SDSS) has produced one largest redshift samples galaxies selected from CCD images. Using 11,275 complete to r* = 17.6 over 140 deg2, we compute luminosity function in band a range -23 < M -16 (for h 1). The result is well-described by Schechter with parameters ϕ* (1.46 ± 0.12) × 10-2 h3 Mpc-3, M* -20.83 0.03, and α -1.20 0.03. implied density j ≈ (2.6 0.3) 108h L⊙ Mpc-3. We find that surface brightness selection...
We used fully cosmological, high resolution N-body + SPH simulations to follow the formation of disk galaxies with rotational velocities between 135 and 270 km/sec in a Lambda CDM universe. The include gas cooling, star formation, effects uniform UV background physically motivated description feedback from supernovae. host dark matter halos have spin last major merger redshift typical galaxy sized as measured recent large scale N--Body simulations. simulated form rotationally supported disks...
The ACS Nearby Galaxy Survey Treasury (ANGST) is a systematic survey to establish legacy of uniform multi-color photometry resolved stars for volume-limited sample nearby galaxies (D < 4 Mpc).The volume encompasses 69 in diverse environments, including close pairs, small & large groups, filaments, and truly isolated regions.The include nearly complete range morphological types spanning factor ∼ 10 luminosity star formation rate.The data consists images taken with the Advanced Camera Surveys...
We examine the evolution of inner dark matter (DM) and baryonic density profile a new sample simulated field galaxies using fully cosmological, Λ cold (ΛCDM), high-resolution SPH+N-Body simulations. These simulations include explicit H2 metal cooling, star formation (SF) supernovae-driven gas outflows. Starting at high redshift, rapid, repeated outflows following bursty SF transfer energy to DM component significantly flatten originally 'cuspy' central mass with present-day stellar masses in...
We examine the properties of dark matter haloes within a rich galaxy cluster using high-resolution simulation that captures cosmological context cold universe. The mass and force resolution permit 150 with circular velocities larger than 80 km s−1 virial radius 2 Mpc (with Hubble constant H0 = 50 Mpc−1). This enables an unprecedented study statistical large sample evolving in dense environment. cumulative fraction attached to these varies from close zero per cent at 200 kpc 13 radius. Even...
The authors present the results of numerical simulations origin and evolution solar system comet cloud. They assume that comets formed in outer planetary region their orbits evolved to current state through perturbations, stellar encounters, galactic tide. is followed using a hybrid integration scheme which directly integrates regularized equations motion for cometary with large semimajor axes, while solving an energy-diffusion equation more tightly bound orbits. Stellar encounters are...
We compare the results of thirteen cosmological gasdynamical codes used to simulate formation a galaxy in LCDM structure paradigm. The various runs differ their hydrodynamical treatment (SPH, moving-mesh and AMR) but share same initial conditions adopt latest published model cooling, star feedback. Despite common halo assembly history, we find large code-to-code variations stellar mass, size, morphology gas content at z=0, due mainly different implementations Compared with observation, most...
Can dissipationless N-body simulations be used to reliably determine the structural and substructure properties of dark matter halos? A large simulation a galaxy cluster in cold universe is increase force mass resolution current "high-resolution simulations" by almost an order magnitude examine convergence important physical quantities. The contains ~5 million particles within final virial radius, Rvir ≃ 2 Mpc (with H0 = 50 km s-1 Mpc-1), simulated using 1.0 kpc (≡0.05% Rvir); 4.3 × 1014 M☉,...
We introduce the Making Galaxies in a Cosmological Context (MaGICC) program of smoothed particle hydrodynamics (SPH) simulations. describe parameter study galaxy formation simulations an L* that uses early stellar feedback combined with supernova to match mass--halo mass relationship. While alone can reduce star enough relationship, forms too many stars before z=2 evolution seen using abundance matching. Our is purely thermal and thus operates like UV ionization source as well providing some...
view Abstract Citations (343) References (19) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The Origin of Short-Period Comets Duncan, M. ; Quinn, T. Tremaine, S. authors present the key results an extensive series numerical simulations evolution comet orbits due to gravitational perturbations giant planets. show that inclination distribution comets with large perihelion (q ≤ 30 AU) evolve observable (i.e., those q 1.5 is approximately preserved. Thus,...
Stars in disks of spiral galaxies are usually assumed to remain roughly at their birth radii. This assumption is built into decades modelling the evolution stellar populations our own Galaxy and external systems. We present results from self-consistent high-resolution $N$-body + Smooth Particle Hydrodynamics simulations disk formation, which stars migrate across significant galactocentric distances due resonant scattering with transient arms, while preserving circular orbits. investigate...