A5047799971- Galaxies: Formation, Evolution, Phenomena
- Astronomy and Astrophysical Research
- Cosmology and Gravitation Theories
- Stellar, planetary, and galactic studies
- Dark Matter and Cosmic Phenomena
- Scientific Research and Discoveries
- Pulsars and Gravitational Waves Research
- Astrophysics and Star Formation Studies
- Gamma-ray bursts and supernovae
- History and Developments in Astronomy
- Relativity and Gravitational Theory
- Radio Astronomy Observations and Technology
- Astrophysical Phenomena and Observations
- Mathematical and Theoretical Analysis
- Spacecraft and Cryogenic Technologies
- Remote Sensing in Agriculture
- Psychology, Coaching, and Therapy
- Child and Adolescent Psychosocial and Emotional Development
- Corporate Management and Leadership
- History and Theory of Mathematics
- Astro and Planetary Science
- Astrophysics and Cosmic Phenomena
- Family Caregiving in Mental Illness
- Black Holes and Theoretical Physics
- Bone fractures and treatments
Universitätsklinik Balgrist
2024
Kavli Institute for Theoretical Sciences
2012-2014
Peking University
2013-2014
University of Michigan–Ann Arbor
2008-2013
University of California, Santa Cruz
2008-2009
Michigan United
2009
ETH Zurich
2005-2007
University of Zurich
2005-2006
University of Bern
1989
[abridged] We present a detailed comparison of fundamental dark matter halo properties retrieved by substantial number different finders. These codes span wide range techniques including friends-of-friends (FOF), spherical-overdensity (SO) and phase-space based algorithms. further introduce robust (and publicly available) suite test scenarios that allows finder developers to compare the performance their against those presented here. This set includes mock haloes containing various levels...
We perform a series of simulations Galactic mass dark matter halo at different resolutions, our largest uses over three billion particles and has resolution 1000 M_sun. quantify the structural properties inner distribution study how they depend on numerical resolution. can measure density profile to distance 120 pc (0.05% R_vir) where logarithmic slope is -0.8 -1.4 (0.5% R_vir). propose new two parameter fitting function that linearly varying gradient which fits GHALO VL2 profiles extremely...
The dark matter dominated Fornax dwarf spheroidal has five globular clusters orbiting at ~1 kpc from its centre. In a cuspy CDM halo the globulars would sink to centre their current positions within few Gyrs, presenting puzzle as why they survive undigested present epoch. We show that solution this timing problem is adopt cored halo. use numerical simulations and analytic calculations that, under these conditions, sinking time becomes many Hubble times; effectively stall core radius....
The velocity distribution function of dark matter particles is expected to show significant departures from a Maxwell-Boltzmann distribution. This can have profound effects on the predicted - nucleon scattering rates in direct detection experiments, especially for models which sensitive high tail distribution, such as inelastic (iDM) or light (few GeV) (LDM), and experiments that require energy recoil events, many directionally experiments. Here we determine functions two highest resolution...
The Milky Way contains several distinct old stellar components that provide a fossil record of its formation. We can understand their spatial distribution and kinematics in hierarchical formation scenario by associating the proto-galactic fragments envisaged Searle Zinn (1978) with rare peaks able to cool gas cold dark matter density field collapsing at redshift z>10. use structure simulations explore these early star-forming structures galaxy haloes today. Most proto-galaxies rapidly...
We resolve the inner region of a massive cluster forming in cosmological Λ cold dark matter (CDM) simulation with mass resolution 2 × 106 M⊙ and before z= 4.4 even 3 105 M⊙. This is billion times less than cluster's final virial substantial increase over current ΛCDM simulations. achieve this using new multimass refinement procedure are now able to probe halo density profile down 0.1 per cent radius. The well fitted by power law ρ∝r−γ smallest resolved scale. An roughly constant logarithmic...
The ever increasing size and complexity of data coming from simulations cosmic structure formation demands equally sophisticated tools for their analysis. During the past decade, art object finding in these has hence developed into an important discipline itself. A multitude codes based upon a huge variety methods techniques have been spawned yet question remained as to whether or not they will provide same (physical) information about structures interest. Here we summarize extent previous...
A basic property of objects, such as galaxies and halos that form in cosmological structure formation simulations, is their shape. Here, we critically investigate shape determination methods are commonly used the literature. It found using an enclosed integration volume weight factors r−2 r−2ell (elliptical radius) for contribution each particle or element tensor leads to biased axis ratios smoothing details when calculating local a function distance from center. To determine matter...
We study the detailed structure of galaxies at redshifts z > 2 using cosmological simulations with improved modeling interstellar medium and star formation. The follow formation dissociation molecular hydrogen, include only in cold gas. gas is more concentrated towards center than atomic gas, as a consequence, resulting stellar distribution very compact. For halos total mass above 10^{11} Mo, median half-mass radius disks 0.8 kpc = 3. vertical disk much thinner that neutral Relative to...
We use the recently completed one billion particle Via Lactea II LambdaCDM simulation to investigate local properties like density, mean velocity, velocity dispersion, anisotropy, orientation and shape of dispersion ellipsoid, as well structure in space dark matter haloes. show that at same radial distance from halo centre, these can deviate by orders magnitude canonical, spherically averaged values, a variation only be partly explained triaxiality presence subhaloes. The mass density...
Merging compact binaries are the most viable and best studied candidates for gravitational wave (GW) detection by fully operational network of ground-based observatories. In anticipation first detections, expected distribution GW sources in local universe is considerable interest. Here we investigate full phase space coalescing at $z = 0$ using dark matter simulations structure formation. The fact that these binary systems acquire large barycentric velocities birth ("kicks") results merger...
Several general trends have been identified for equilibrated, self-gravitating collisionless systems, such as density or anisotropy profiles. These are integrated quantities which naturally depend on the underlying velocity distribution function (VDF) of system. We study this VDF through a set numerical simulations, allow us to extract both radial and tangential VDFs. find that shape is universal, in sense it depends only two things: namely dispersion (radial tangential) local slope density....
Our recently completed one billion particle Via Lactea II simulation of a Milky Way-sized dark matter halo resolves over 50,000 gravitationally bound clumps orbiting today within the virialized region main host. About 2,300 these subhalos have or more "progenitors" above 1e6 Msun at redshift 11, i.e. massive enough for their gas to cooled via excitation H2 and fragmented prior epoch cosmic reionization. We count 4,500 such progenitors: if were able convert fraction content into very...
We investigate the transition from primordial Population III (Pop III) star formation to normal Pop II in first galaxies using new cosmological hydrodynamic simulations. find that while stars seed their host with metals, they cannot sustain significant outflows enrich intergalactic medium, even assuming a top-heavy initial mass function. This means could potentially continue until z~6 different unenriched regions of universe, before being ultimately shut off by cosmic reionization. Within an...
It is a clear and unique prediction of the cold dark matter paradigm cosmological structure formation that galaxies form hierarchically are embedded in massive, extended halos teeming with self-bound substructure, or 'subhalos.' The amount spatial distribution subhalos around their host provide information clues on galaxy assembly process nature matter. Here we present results from Via Lactea INCITE simulation, one billion particle, million CPU-hour simulation evolution galactic halo its...
It is common practice to describe formal size and mass scales of dark matter halos as spherical overdensities with respect an evolving density threshold. Here, we critically investigate the evolutionary effects several such commonly used definitions compare them halo evolution within fixed physical well other intrinsic properties halos. shown that, in general, traditional way characterizing sizes masses dramatically overpredicts degree last 10 Gyr, especially for low-mass This...
We present a simple and efficient method to set up spherical structure models for N-body simulations with multimass technique. This technique reduces by substantial factor the computer run time needed in order resolve given scale as compared single-mass models. It therefore allows smaller scales time. Here, we several an effective resolution of 1.68 x 10^9 particles within their virial radius which are stable over cosmologically relevant time-scales. As application, confirm theoretical...
We revisit the formation and evolution of first galaxies using new hydrodynamic cosmological simulations with adaptive refinement tree code. Our feature a recently developed model for H2 dissociation, star recipe that is based on molecular rather than atomic gas. Here, we develop implement metal-free Population III (Pop III) stars in galaxy-scale resolve primordial clouds sufficiently high density. base our results prior zoom-in resolved protostellar collapse pre-galactic objects. find epoch...
Merging compact binaries are the one source of gravitational radiation so far identified. Because short-period systems which will merge in less than a Hubble time have already been observed as binary pulsars, they important both wave sources for observatories such LIGO but also progenitors short gamma-ray bursts (SGRBs). The fact that these must large systemic velocities implies by merge, be from their formation site. locations merging sites depend sensitively on potential galaxy host, until...
We present a new time-stepping criterion for N-body simulations that is based on the true dynamical time of particle. This allows us to follow orbits particles correctly in all environments since it has better adaptivity than previous criteria used simulations. Furthermore, requires far fewer force evaluations low-density regions simulation and no dependence artificial parameters such as, example, softening length. can be orders magnitude faster conventional ad hoc methods employ...
The coalescence of a massive black hole (MBH) binary leads to the gravitational-wave recoil system and its ejection from galaxy core. We have carried out N-body simulations motion MBH = 3.7 × 106 M☉ remnant in "Via Lactea I" simulation, Milky Way-sized dark matter halo. receives velocity Vkick 80, 120, 200, 300, 400 km s−1 at redshift 1.5, orbit is followed for over 1 Gyr within "live" host halo, subject only gravity dynamical friction against background. show that, owing asphericities...