Results for "Arjen van Elteren"

total 23239took 0.17s
Simulations of Dense Stellar Systems with the AMUSE Software ToolkitNov 16 2011We describe AMUSE, the Astrophysical Multipurpose Software Environment, a programming framework designed to manage multi-scale, multi-physics simulations in a hierarchical, extensible, and internally consistent way. Constructed as a collection of individual ... More
Multi-physics simulations using a hierarchical interchangeable software interfaceOct 12 2011We introduce a general-purpose framework for interconnecting scientific simulation programs using a homogeneous, unified software interface. Our framework is intrinsically parallel, and conveniently separates all components in memory. It performs unit ... More
The signatures of the parental cluster on field planetary systemsNov 03 2017Nov 23 2017Due to the high stellar densities in young clusters, planetary systems formed in these environments are likely to have experienced perturbations from encounters with other stars. We carry out direct $N$-body simulations of multi-planet systems in star ... More
Multi-physics simulations using a hierarchical interchangeable software interfaceApr 25 2012Sep 17 2012We introduce a general-purpose framework for interconnecting scientific simulation programs using a homogeneous, unified interface. Our framework is intrinsically parallel, and conveniently separates all component numerical modules in memory. This strict ... More
The influence of dense gas rings on the dynamics of a stellar disk in the Galactic centerDec 08 2015The Galactic center hosts several hundred early-type stars, about 20% of which lie in the so-called clockwise disk, while the remaining 80% do not belong to any disks. The circumnuclear ring (CNR), a ring of molecular gas that orbits the supermassive ... More
The consequences of a nearby supernova on the early Solar SystemFeb 12 2018If the Sun was born in a relatively compact open cluster (half-mass radius ~3pc) with ~10^3 stars, it is quite likely that a massive (>10MSun) star was nearby when it exploded in a supernova. The repercussions of a supernova can be rather profound, and ... More
The survivability of planetary systems in young and dense star clustersFeb 12 2019We perform a simulation using the Astrophysical Multipurpose Software Environment of the Orion Trapezium star cluster in which the evolution of the stars and the dynamics of planetary systems are taken into account. The initial conditions are selected ... More
The consequences of a nearby supernova on the early Solar SystemFeb 12 2018Apr 11 2018If the Sun was born in a relatively compact open cluster, it is quite likely that a massive (10MSun) star was nearby when it exploded in a supernova. The repercussions of a supernova can be rather profound, and the current Solar System may still bear ... More
Survivability of planetary systems in young and dense star clustersFeb 12 2019Mar 11 2019We perform a simulation using the Astrophysical Multipurpose Software Environment of the Orion Trapezium star cluster in which the evolution of the stars and the dynamics of planetary systems are taken into account. The initial conditions from earlier ... More
A mass-dependent slope of the galaxy size-mass relation out to z~3: further evidence for a direct relation between median galaxy size and median halo massJan 15 2019We reassess the galaxy size-mass relation out to z~3 using a new definition of size and a sample of >29,000 galaxies from the 3D-HST, CANDELS, and COSMOS-DASH surveys. Instead of the half-light radius r_50 we use r_80, the radius containing 80% of the ... More
The dynamic importance of nodes is poorly predicted by static topological featuresApr 14 2019One of the most central questions in network science is: which nodes are most important? Often this question is answered using topological properties such as high connectedness or centrality in the network. However it is unclear whether topological connectedness ... More
An Absence of Radio-Loud Active Galactic Nuclei in Geometrically Flat Quiescent Galaxies: Implications for Maintenance-Mode Feedback ModelsFeb 01 2019Feb 05 2019Maintenance-mode feedback from low-accretion rate AGN, manifesting itself observationally through radio-loudness, is invoked in all cosmological galaxy formation models as a mechanism that prevents excessive star-formation in massive galaxies (M$_*$ $\gtrsim$ ... More
Rejuvenation in $z\sim0.8$ quiescent galaxies in LEGA-CMay 18 2019We use reconstructed star-formation histories (SFHs) of quiescent galaxies at $z=0.6-1$ in the LEGA-C survey to identify secondary star-formation episodes that, after an initial period of quiescence, moved the galaxies back to the star-forming main sequence ... More
Cosmogenic photons strongly constrain UHECR source modelsSep 12 2016With the newest version of our Monte Carlo code for ultra-high-energy cosmic ray (UHECR) propagation, CRPropa 3, the flux of neutrinos and photons due to interactions of UHECRs with extragalactic background light can be predicted. Together with the recently ... More
Fast and slow paths to quiescence: ages and sizes of 400 quiescent galaxies from the LEGA-C surveySep 04 2018Oct 11 2018We analyze stellar age indicators (D$_n$4000 and EW(H$\delta$)) and sizes of 467 quiescent galaxies with $M_\ast \geq 10^{10} M_\odot$ at $z\sim0.7$ drawn from DR2 of the LEGA-C survey. Interpreting index variations in terms of equivalent single stellar ... More
The evolution of galaxy shapes in CANDELS: from prolate to oblateMay 31 2018We model the projected b/a-log a distributions of CANDELS main sequence star-forming galaxies, where a (b) is the semi-major (semi-minor) axis of the galaxy images. We find that smaller-a galaxies are rounder at all stellar masses M and redshifts, so ... More
Determining neutrino absorption spectra at Ultra-High EnergiesJan 22 2008Apr 16 2008A very efficient method to measure the flux of Ultra-high energy (UHE) neutrinos is through the detection of radio waves which are emitted by the particle shower in the lunar regolith. The highest acceptance is reached for radio waves in the frequency ... More
Multi-scale and multi-domain computational astrophysicsFeb 19 2014Astronomical phenomena are governed by processes on all spatial and temporal scales, ranging from days to the age of the Universe (13.8,Gyr) as well as from km size up to the size of the Universe. This enormous range in scales is contrived, but as long ... More
PeV Neutrinos from Ultra-High-Energy Cosmic RaysJul 24 2014We investigate the possibility that the recently detected TeV-PeV neutrino events by IceCube can originate from extragalactic ultra-high-energy cosmic ray interactions with the cosmic microwave background or the UV/optical/IR background. This is done ... More
IMAGINE: A comprehensive view of the interstellar medium, Galactic magnetic fields and cosmic raysMay 07 2018Sep 06 2018In this white paper we introduce the IMAGINE Consortium and its scientific background, goals and structure. Our purpose is to coordinate and facilitate the efforts of a diverse group of researchers in the broad areas of the interstellar medium, Galactic ... More
1D Kinematics from stars and ionized gas at $z\sim0.8$ from the LEGA-C spectroscopic survey of massive galaxiesNov 19 2018We present a comparison of the observed, spatially integrated stellar and ionized gas velocity dispersions of $\sim1000$ massive ($\log M_{\star}/M_{\odot}\gtrsim\,10.3$) galaxies in the Large Early Galaxy Astrophysics Census (LEGA-C) survey at $0.6\lesssim\,z\lesssim1.0$. ... More
Galaxy Structure as a Driver of the Star Formation Sequence Slope and ScatterAug 19 2015It is well established that (1) star-forming galaxies follow a relation between their star formation rate (SFR) and stellar mass (M$_{\star}$), the "star-formation sequence", and (2) the SFRs of galaxies correlate with their structure, where star-forming ... More
CLASH: Three Strongly Lensed Images of a Candidate z ~ 11 GalaxyNov 15 2012We present a candidate for the most distant galaxy known to date with a photometric redshift z = 10.7 +0.6 / -0.4 (95% confidence limits; with z < 9.5 galaxies of known types ruled out at 7.2-sigma). This J-dropout Lyman Break Galaxy, named MACS0647-JD, ... More
ALMA Spectroscopic Survey in the Hubble Ultra Deep Field: Molecular gas reservoirs in high-redshift galaxiesJul 22 2016Sep 12 2016We study the molecular gas properties of high-$z$ galaxies observed in the ALMA Spectroscopic Survey (ASPECS) that targets a $\sim1$ arcmin$^2$ region in the Hubble Ultra Deep Field (UDF), a blind survey of CO emission (tracing molecular gas) in the 3mm ... More
Spatially Resolved Stellar Kinematics of Field Early-Type Galaxies at z=1: Evolution of the Rotation RateApr 26 2008Jun 20 2008We use the spatial information of our previously published VLT/FORS2 absorption line spectroscopy to measure mean stellar velocity and velocity dispersion profiles of 25 field early-type galaxies at a median redshift z=0.97 (full range 0.6<z<1.2). This ... More
Generalization of the event-based Carnevale-Hines integration scheme for integrate-and-fire modelsMay 12 2008An event-based integration scheme for an integrate-and-fire neuron model with exponentially decaying excitatory synaptic currents and double exponential inhibitory synaptic currents has recently been introduced by Carnevale and Hines. This integration ... More
A simple rule for axon outgrowth and synaptic competition generates realistic connection lengths and filling fractionsJun 03 2009Neural connectivity at the cellular and mesoscopic level appears very specific and is presumed to arise from highly specific developmental mechanisms. However, there are general shared features of connectivity in systems as different as the networks formed ... More
Checking the Quality of Clinical Guidelines using Automated Reasoning ToolsJun 02 2008Requirements about the quality of clinical guidelines can be represented by schemata borrowed from the theory of abductive diagnosis, using temporal logic to model the time-oriented aspects expressed in a guideline. Previously, we have shown that these ... More
ALMA Spectroscopic Survey in the Hubble Ultra Deep Field: Survey DescriptionJul 22 2016We present the rationale for and the observational description of ASPECS: The ALMA SPECtroscopic Survey in the Hubble Ultra-Deep Field (UDF), the cosmological deep field that has the deepest multi-wavelength data available. Our overarching goal is to ... More
PeV neutrinos from the propagation of ultra-high energy cosmic raysSep 18 2012Jan 23 2013We discuss the possibility that the PeV neutrinos recently observed by IceCube are produced by the interactions of extragalactic cosmic rays during their propagation through the radiation backgrounds. We show that the fluxes resulting from the decays ... More
ALMA spectroscopic survey in the Hubble Ultra Deep Field: CO luminosity functions and the evolution of the cosmic density of molecular gasJul 22 2016Sep 12 2016In this paper we use ASPECS, the ALMA Spectroscopic Survey in the {\em Hubble} Ultra Deep Field (UDF) in band 3 and band 6, to place blind constraints on the CO luminosity function and the evolution of the cosmic molecular gas density as a function of ... More
The Astrophysical Multipurpose Software EnvironmentJul 11 2013We present the open source Astrophysical Multi-purpose Software Environment (AMUSE, www.amusecode.org), a component library for performing astrophysical simulations involving different physical domains and scales. It couples existing codes within a Python ... More
The Relation between Galaxy Structure and Spectral Type: Implications for the Buildup of the Quiescent Galaxy Population at 0.5<z<2.0Jan 11 2016We present the relation between galaxy structure and spectral type, using a K-selected galaxy sample at 0.5<z<2.0. Based on similarities between the UV-to-NIR spectral energy distributions, we classify galaxies into 32 spectral types. The different types ... More
Determining the fraction of cosmic-ray protons at ultra-high energies with cosmogenic neutrinosJan 07 2019Cosmogenic neutrinos are produced when ultra-high-energy cosmic rays (UHECRs) interact with cosmological photon fields. Limits on the diffuse flux of these neutrinos can be used to constrain the fraction of protons arriving at Earth with energies $E_{p} ... More
Modelling honey bee colonies in winter using a Keller-Segel model with a sign-changing chemotactic coefficientFeb 22 2019Thermoregulation in honey bee colonies during winter is thought to be self-organised. We added mortality of individual honey bees to an existing model of thermoregulation to account for elevated losses of bees that are reported worldwide. The aim of analysis ... More
CANDELS: Constraining the AGN-Merger Connection with Host Morphologies at z~2Sep 12 2011Using HST/WFC3 imaging taken as part of the Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey (CANDELS), we examine the role that major galaxy mergers play in triggering active galactic nuclei (AGN) activity at z~2. Our sample consists of ... More
The Detection of a Red Sequence of Massive Field Galaxies at z~2.3 and its Evolution to z~0Apr 28 2008The existence of massive galaxies with strongly suppressed star formation at z~2.3, identified in a previous paper, suggests that a red sequence may already be in place beyond z=2. In order to test this hypothesis, we study the rest-frame U-B color distribution ... More
On the Masses of Galaxies in the Local UniverseSep 08 2010We compare estimates of stellar mass, Mstar, and dynamical mass,Mdyn,for a sample of galaxies from the Sloan Digital Sky Survey (SDSS). We assume dynamical homology (i.e., Mdyn = dispersion**2 * Reff, and we find a tight but strongly non-linear relation: ... More
A New View of the Size-Mass Distribution of Galaxies: Using $r_{20}$ and $r_{80}$ instead of $r_{50}$Jan 15 2019When investigating the sizes of galaxies it is standard practice to use the half-light radius, $r_{50}$. Here we explore the effects of the size definition on the distribution of galaxies in the size -- stellar mass plane. Specifically, we consider $r_{20}$ ... More
A constant limiting mass scale for flat early-type galaxies from z=1 to z=0: density evolves but shapes do notAug 30 2011Sep 01 2011We measure the evolution in the intrinsic shape distribution of early-type galaxies from z~1 to z~0 by analyzing their projected axis-ratio distributions. We extract a low-redshift sample (0.04 < z < 0.08) of early-type galaxies with very low star-formation ... More
Secondary neutrino and gamma-ray fluxes from SimProp and CRPropaJan 04 2019Jan 11 2019The interactions of ultra-high-energy cosmic rays (UHECRs) with background photons in extragalactic space generate high-energy neutrinos and photons. Simulations of UHECR propagation require assumptions about physical quantities such as the spectrum of ... More
Secondary neutrino and gamma-ray fluxes from SimProp and CRPropaJan 04 2019Apr 18 2019The interactions of ultra-high-energy cosmic rays (UHECRs) in extragalactic space with photons of the cosmic microwave background (CMB) and extragalactic background light (EBL) can generate high-energy neutrinos and photons. Simulations of UHECR propagation ... More
The Physical Origins of The Morphology-Density Relation: Evidence for Gas Stripping from the SDSSApr 02 2010Apr 26 2010We provide a physical interpretation and explanation of the morphology-density relation for galaxies, drawing on stellar masses, star formation rates, axis ratios and group halo masses from the Sloan Digital Sky Survey. We first re-cast the classical ... More
The similar stellar populations of quiescent spiral and elliptical galaxiesSep 25 2011Jul 18 2012We compare the stellar population properties in the central regions of visually classified non-starforming spiral and elliptical galaxies from Galaxy Zoo and SDSS DR7. The galaxies lie in the redshift range $0.04<z<0.1$ and have stellar masses larger ... More
Comparing Dynamical and Photometric Mass Estimates of Low- and High-Redshift Galaxies: Random and Systematic UncertaintiesJul 28 2006We determine the importance of redshift-dependent systematic effects in the determination of stellar masses from broad band spectral energy distributions (SEDs), using high quality kinematic and photometric data of early-type galaxies at z~1 and z~0. ... More
Spontaneous Charging and Crystallization of Water Droplets in OilJul 29 2008Jul 31 2008We study the spontaneous charging and the crystallization of spherical micron-sized water-droplets dispersed in oil by numerically solving, within a Poisson-Boltzmann theory in the geometry of a spherical cell, for the density profiles of the cations ... More
M/L and Color Evolution for A Deep Sample of M* Cluster Galaxies at z~1: The Formation Epoch and the Tilt of the Fundamental PlaneSep 22 2010Oct 08 2010We have measured velocity dispersions for a sample of 36 galaxies with J < 21.2 or Mr < -20.6 mag in MS1054-03, a massive cluster of galaxies at z = 0.83. Our data are of uniformly high quality down to our selection limit, our 16-hour exposures typically ... More
Effects of uncertainties in simulations of extragalactic UHECR propagation, using CRPropa and SimPropAug 07 2015Dec 13 2015The results of simulations of the extragalactic propagation of ultra-high energy cosmic rays (UHECRs) have intrinsic uncertainties due to poorly known physical quantities and approximations used in the codes. We quantify the uncertainties in the simulated ... More
Secondary neutrino and gamma-ray fluxes from SimProp and CRPropaJan 04 2019Mar 08 2019The interactions of ultra-high-energy cosmic rays (UHECRs) in extragalactic space with photons of the cosmic microwave background (CMB) and extragalactic background light (EBL) can generate high-energy neutrinos and photons. Simulations of UHECR propagation ... More
Realisation of a Frustrated 3D Magnetic Nanowire LatticeDec 06 2018Patterning nanomagnets in three-dimensions presents a new paradigm in condensed matter physics and allows access to a plethora of fundamental phenomena including robust spin textures, magnetic metamaterials that are home to defects carrying magnetic charge ... More
Stellar Masses and SFRs for 1M Galaxies from SDSS and WISEJun 01 2015We combine SDSS and WISE photometry for the full SDSS spectroscopic galaxy sample, creating SEDs that cover lambda=0.4-22 micron for an unprecedented large and comprehensive sample of 858,365 present-epoch galaxies. Using MAGPHYS we then model simultaneously ... More
Ultra-High-Energy Cosmic Rays from Radio GalaxiesJan 24 2017Mar 08 2018Radio galaxies are intensively discussed as the sources of cosmic rays observed above about $3\,{\times}\,10^{18}\,\text{eV}$, called ultra-high energy cosmic rays (UHECRs). We present a first, systematic approach that takes the individual characteristics ... More
On the Size and Comoving Mass Density Evolution of Early-Type GalaxiesMar 27 2009Apr 24 2009We present a simple, empirically motivated model that simultaneously predicts the evolution of the mean size and the comoving mass density of massive early-type galaxies from z=2 to the present. First we demonstrate that some size evolution of the population ... More
Major Merging: The Way to Make a Massive, Passive GalaxyOct 21 2009Nov 10 2009We analyze the projected axial ratio distribution, p(b/a), of galaxies that were spectroscopically selected from the Sloan Digital Sky Survey (DR6) to have low star-formation rates. For these quiescent galaxies we find a rather abrupt change in p(b/a) ... More
The Pair Fraction of Massive Galaxies at 0 < z < 3Sep 13 2011Using a mass-selected ($M_{\star} \ge 10^{11} M_{\odot}$) sample of 198 galaxies at 0 < z < 3.0 with HST/NICMOS $H_{160}$-band images from the COSMOS survey, we find evidence for the evolution of the pair fraction above z ~ 2, an epoch in which massive ... More
Recent Structural Evolution of Early-Type Galaxies: Size Growth from z=1 to z=0Aug 01 2008Oct 02 2008Strong size and internal density evolution of early-type galaxies between z~2 and the present has been reported by several authors. Here we analyze samples of nearby and distant (z~1) galaxies with dynamically measured masses in order to confirm the previous, ... More
CRPropa 2.0 -- a Public Framework for Propagating High Energy Nuclei, Secondary Gamma Rays and NeutrinosJun 14 2012Version 2.0 of CRPropa is public software to model the extra-galactic propagation of ultra-high energy nuclei of atomic number Z<26 through structured magnetic fields and ambient photon backgrounds taking into account all relevant particle interactions. ... More
Smart Grid Co-Simulation with MOSAIK and HLA: A Comparison StudyNov 15 2018Evaluating new technological developments for energy systems is becoming more and more complex. The overall application environment is a continuously growing and interconnected cyber-physical system so that analytical assessment is practically impossible ... More
On the Dearth of Compact, Massive, Red Sequence Galaxies in the Local UniverseJul 27 2009Using data from the Sloan Digital Sky Survey (SDSS; data release 7), we have conducted a search for local analogs to the extremely compact, massive, quiescent galaxies that have been identified at z > 2. We show that incompleteness is a concern for such ... More
A Wide-Field Study of the z~0.8 Cluster RX J0152.7-1357: the Role of Environment in the Formation of the Red-SequenceDec 10 2008Jan 27 2009[ABRIDGED] We present the first results from the largest spectroscopic survey to date of an intermediate redshift galaxy cluster, the z=0.834 cluster RX J0152.7-1357. We use the colors of galaxies, assembled from a D~12 Mpc region centered on the cluster, ... More
A New Method for Wide-Field Near-IR Imaging with the Hubble Space TelescopeMar 01 2016We present a new technique for wide and shallow observations using the near-infrared channel of Wide Field Camera 3 (WFC3) on the Hubble Space Telescope (HST). Wide-field near-IR surveys with HST are generally inefficient, as guide star acquisitions make ... More
The UVJ Selection of Quiescent and Star Forming Galaxies: Separating Early and Late-Type Galaxies and Isolating Edge-on SpiralsJul 15 2011We utilize for the first time HST ACS imaging to examine the structural properties of galaxies in the rest-frame U-V versus V-J diagram (i.e., the UVJ diagram) using a sample at 0.6<z<0.9 that reaches a low stellar mass limit (log M/Msun>10.25). The use ... More
Weakly nonlocal irreversible thermodynamics - the Guyer-Krumhansl and the Cahn-Hilliard equationsJun 27 2001Oct 18 2001Examples of irreversible thermodynamic theory of nonlocal phenomena are given, based on generalized entropy current. Thermodynamic currents and forces are identified to derive the Guyer-Krumhansl and Cahn-Hilliard equations. In the latter case Gurtin's ... More
Weakly nonlocal irreversible thermodynamics - the Ginzburg-Landau equationNov 16 2001Dec 12 2001The variational approach to weakly nonlocal thermodynamic theories is critically revisited in the light of modern nonequilibrium thermodynamics. The example of Ginzburg-Landau equation is investigated in detail.
A number theoretic question arising in the geometry of plane curves and in billiard dynamicsMar 25 2011We prove that if $\rho\neq1/2$ is a rational number between zero and one, then there is no integer $n>1$ such that $$ n\tan(\pi\rho)=\tan(n\pi\rho). $$ This has interpretations both in the theory of bicycle curves and that of mathematical billiards.
Shape Evolution of Massive Early-Type Galaxies: Confirmation of Increased Disk Prevalence at z>1Nov 09 2012We use high-resolution K-band VLT/HAWK-I imaging over 0.25 square degrees to study the structural evolution of massive early-type galaxies since z~1. Mass-selected samples, complete down to log(M/M_sun)~10.7 such that `typical' L* galaxies are included ... More
Sum-product estimates via directed expandersMay 04 2007Let $\F_q$ be a finite field of order $q$ and $P$ be a polynomial in $\F_q[x_1, x_2]$. For a set $A \subset \F_q$, define $P(A):=\{P(x_1, x_2) | x_i \in A \}$. Using certain constructions of expanders, we characterize all polynomials $P$ for which the ... More
A structural approach to subset-sum problemsApr 20 2008We discuss a structural approach to subset-sum problems in additive combinatorics. The core of this approach are Freiman-type structural theorems, many of which will be presented through the paper. These results have applications in various areas, such ... More
High Redshift Massive Quiescent Galaxies are as Flat as Star Forming Galaxies: The Flattening of Galaxies and the Correlation with Structural Properties in CANDELS/3D-HSTJan 07 2019We investigate the median flattening of galaxies at $0.2<z<4.0$ in all five CANDELS/3D-HST fields via the apparent axis ratio $q$. We separate the sample into bins of redshift, stellar-mass, s\'ersic index, size, and UVJ determined star-forming state ... More
An Over-Massive Black Hole in the Compact Lenticular Galaxy NGC1277Nov 27 2012All massive galaxies likely have supermassive black holes at their centers, and the masses of the black holes are known to correlate with properties of the host galaxy bulge component. Several explanations have been proposed for the existence of these ... More
The Luminosity-Size and Mass-Size Relations of Galaxies out to z~3Jul 01 2003Dec 16 2003The luminosity-size and stellar mass-size distributions of galaxies out to z~3 is presented. We use very deep near-infrared images of the Hubble Deep Field South in the J_s, H, and K_s bands, taken as part FIRES at the VLT, to follow the evolution of ... More
Spectroscopic Confirmation of a Substantial Population of Luminous Red Galaxies at Redshifts z>2Mar 07 2003We confirm spectroscopically the existence of a population of galaxies at z>~2 with rest-frame optical colors similar to normal nearby galaxies. The galaxies were identified by their red near-infrared colors in deep images obtained with ISAAC on the Very ... More
The Number Density Evolution of Extreme Emission Line Galaxies in 3D-HST: Results from a Novel Automated Line Search Technique for Slitless SpectroscopyAug 04 2016The multiplexing capability of slitless spectroscopy is a powerful asset in creating large spectroscopic datasets, but issues such as spectral confusion make the interpretation of the data challenging. Here we present a new method to search for emission ... More
Morphologies of low-redshift AGN host galaxies: what role does AGN luminosity play?Mar 08 2013Mergers of galaxies have been suspected to be a major trigger of AGN activity for many years. However, when compared to carefully matched control samples, AGN host galaxies often show no enhanced signs of interaction. A common explanation for this lack ... More
The merger-driven evolution of massive galaxiesFeb 22 2010Jun 29 2010We explore the rate and impact of galaxy mergers on the massive galaxy population using the amplitude of the two-point correlation function on small scales for M > 5e10 M_sun galaxies from the COSMOS and COMBO-17 surveys. Using a pair fraction derived ... More
CRPropa 3 - a Public Astrophysical Simulation Framework for Propagating Extraterrestrial Ultra-High Energy ParticlesMar 23 2016May 24 2016We present the simulation framework CRPropa version 3 designed for efficient development of astrophysical predictions for ultra-high energy particles. Users can assemble modules of the most relevant propagation effects in galactic and extragalactic space, ... More
Relations Between the Sizes of Galaxies and their Dark Matter Halos at Redshifts $0 < z < 3$Jan 15 2017Mar 22 2017We derive relations between the effective radii $R_{\rm{eff}}$ of galaxies and the virial radii $R_{200c}$ of their dark matter halos over the redshift range $0 < z < 3$. For galaxies, we use the measured sizes from deep images taken with \emph{Hubble ... More
Emergence of steady and oscillatory localized structures in a phytoplankton-nutrient modelSep 16 2010Aug 26 2011Co-limitation of marine phytoplankton growth by light and nutrient, both of which are essential for phytoplankton, leads to complex dynamic behavior and a wide array of coherent patterns. The building blocks of this array can be considered to be deep ... More
Central limit theorems for random polytopes in a smooth convex setMar 24 2005Let $K$ be a smooth convex set with volume one in $\BBR^d$. Choose $n$ random points in $K$ independently according to the uniform distribution. The convex hull of these points, denoted by $K_n$, is called a {\it random polytope}. We prove that several ... More
A simple SVD algorithm for finding hidden partitionsApr 15 2014Finding a hidden partition in a random environment is a general and important problem, which contains as subproblems many famous questions, such as finding a hidden clique, finding a hidden coloring, finding a hidden bipartition etc. In this paper, we ... More
Singular vectors under random perturbationApr 12 2010Computing the first few singular vectors of a large matrix is a problem that frequently comes up in statistics and numerical analysis. Given the presence of noise, exact calculation is hard to achieve, and the following problem is of importance: \vskip2mm ... More
Measuring the Average Evolution of Luminous Galaxies at z<3: The Rest-frame Optical Luminosity Density, Spectral Energy Distribution, and Stellar Mass DensityJun 21 2006(Abridged) We present the evolution of the volume averaged properties of the rest-frame optically luminous galaxy population to z~3, determined from four disjoint deep fields with optical to near-infrared wavelength coverage. We select galaxies above ... More
CRPropa 3.0 - a Public Framework for Propagating UHE Cosmic Rays through Galactic and Extragalactic SpaceJul 10 2013The interpretation of experimental data of ultra-high energy cosmic rays (UHECRs) above 10^17 eV is still under controversial debate. The development and improvement of numerical tools to propagate UHECRs in galactic and extragalactic space is a crucial ... More
The dynamics of disappearing pulses in a singularly perturbed reaction-diffusion system with parameters that vary in time and spaceFeb 08 2018We consider the evolution of multi-pulse patterns in an extended Klausmeier equation with parameters that change in time and/or space. We formally show that the full PDE dynamics of a $N$-pulse configuration can be reduced to a $N$-dimensional dynamical ... More
The Rest-Frame Optical Luminosity Density, Color, and Stellar Mass Density of the Universe from z=0 to z=3Jul 08 2003Sep 09 2003We present the evolution of the rest-frame optical luminosity density, of the integrated rest-frame optical color, and of the stellar mass density for a sample of Ks-band selected galaxies in the HDF-S. We derived the luminosity density in the rest-frame ... More
A Significant Population of Red, Near-IR Selected High Redshift GalaxiesMar 07 2003We use very deep near-infrared photometry of the Hubble Deep Field South taken with ISAAC/VLT to identify a population of high redshift galaxies with rest- frame optical colors similar to those of nearby galaxies. The galaxies are chosen by their infrared ... More
The Majority of Compact Massive Galaxies at z~2 are Disk DominatedJan 12 2011Mar 10 2011We investigate the stellar structure of massive, quiescent galaxies at z~2, based on Hubble Space Telescope/WFC3 imaging from the Early Release Science program. Our sample of 14 galaxies has stellar masses of M* > 10^{10.8} Msol and photometric redshifts ... More
Stellar and Molecular Gas Rotation in a Recently-Quenched Massive Galaxy at z~0.7Apr 26 2018The process by which massive galaxies transition from blue, star-forming disks into red, quiescent galaxies remains one of the most poorly-understood aspects of galaxy evolution. In this investigation, we attempt to gain a better understanding of how ... More
First Results from the TNG50 Simulation: The evolution of stellar and gaseous disks across cosmic timeFeb 14 2019We present a new cosmological, magnetohydrodynamical simulation for galaxy formation: TNG50, the third and final installment of the IllustrisTNG project. TNG50 evolves 2x2160^3 dark-matter particles and gas cells in a volume 50 comoving Mpc across. It ... More
An Algebraic Framework for Discrete Tomography: Revealing the Structure of DependenciesJun 03 2009Jul 30 2009Discrete tomography is concerned with the reconstruction of images that are defined on a discrete set of lattice points from their projections in several directions. The range of values that can be assigned to each lattice point is typically a small discrete ... More
Weakly nonlocal continuum physics - the Ginzburg-Landau equationOct 18 2002May 13 2003Some peculiarities of the exploitation of the entropy inequality in case of weakly nonlocal continuum theories are investigated and refined. As an example it is shown that the proper application of the Liu procedure leads to the Ginzburg-Landau equation ... More
Weakly nonlocal continuum theories of granular media: restrictions from the Second LawOct 22 2003Nov 07 2003The classical continuum mechanical model of granular media of rational thermodynamics results in a Coulomb-Mohr type equilibrium stress-strain relation. The proof is based on a two component material model introducing a scalar internal variable. Here ... More
Weakly nonlocal irreversible thermodynamicsDec 12 2001Jan 10 2003Weakly nonlocal thermodynamic theories are critically revisited. A relocalized, irreversible thermodynamic theory of nonlocal phenomena is given, based on a modified form of the entropy current and new kind of internal variables, the so called current ... More
A Massive Galaxy in its Core Formation Phase Three Billion Years After the Big BangJun 12 2014Most massive galaxies are thought to have formed their dense stellar cores at early cosmic epochs. However, cores in their formation phase have not yet been observed. Previous studies have found galaxies with high gas velocity dispersions or small apparent ... More
Exploring the chemical link between local ellipticals and their high-redshift progenitorsOct 25 2013We present Keck/MOSFIRE K-band spectroscopy of the first mass-selected sample of galaxies at $z\sim2.3$. Targets are selected from the 3D-HST Treasury survey. The six detected galaxies have a mean [NII]$\lambda$6584/H$\alpha$ ratio of $0.27\pm0.01$, with ... More
Real-Time Simulation and Hardware-in-the-Loop Approaches for Integrating Renewable Energy Sources into Smart Grids: Challenges & ActionsOct 06 2017The integration of distributed renewable energy sources and the multi-domain behaviours inside the cyber-physical energy system (smart grids) draws up major challenges. Their validation and roll out requires careful assessment, in term of modelling, simulation ... More
Shock Waves in Weakly Compressed Granular MediaApr 23 2013We experimentally probe nonlinear wave propagation in weakly compressed granular media, and observe a crossover from quasi-linear sound waves at low impact, to shock waves at high impact. We show that this crossover grows with the confining pressure $P_0$, ... More
Cosmic ray propagation with CRPropa 3Oct 20 2014Solving the question of the origin of ultra-high energy cosmic rays (UHECRs) requires the development of detailed simulation tools in order to interpret the experimental data and draw conclusions on the UHECR universe. CRPropa is a public Monte Carlo ... More
Design of experiments aided holistic testing of cyber-physical energy systemsFeb 01 2019The complex and often safety-critical nature of cyber-physical energy systems makes validation a key challenge in facilitating the energy transition, especially when it comes to the testing on system level. Reliable and reproducible validation experiments ... More
Optical probes of electron correlations in solidsJul 21 2008Classically the interaction between light and matter is given by the Maxwell relations. These are briefly reviewed and will be used as a basis to discuss several techniques that are used in optical spectroscopy. We then discuss the quantum mechanical ... More