Searching Arxiv, refresh for possibly better results.

Results for "C. A. M. van den Bosch"

total 395293took 0.18s
The Formation of Disk-Bulge-Halo Systems and the Origin of the Hubble SequenceMay 08 1998We investigate the formation of disk-bulge-halo systems by including bulges in the Fall & Efstathiou theory of disk formation. This allows an investigation of bulge dominated disk galaxies, such as S0s and disky ellipticals. The aim of this paper is to ... More
Dissecting the Evolution of Dark Matter Subhaloes in the Bolshoi SimulationNov 08 2016We present a comprehensive analysis of the evolution of dark matter subhaloes in the cosmological Bolshoi simulation. We identify a complete set of 12 unique evolution channels by which subhaloes evolve in between simulation outputs, and study their relative ... More
The Impact of Cooling and Feedback on Disc GalaxiesDec 31 2001We present detailed, analytical models for the formation of disc galaxies to investigate the impact that cooling and feedback have on their structural properties. In particular, we investigate which observables extracted directly from the models are best ... More
The Origin of the Density Distribution of Disk Galaxies: A New Problem for the Standard Model of Disk FormationJul 11 2001We present new models for the formation of disk galaxies that improve upon previous models by following the detailed accretion and cooling of the baryonic mass, and by using realistic distributions of specific angular momentum. Under the assumption of ... More
Constraints on Galaxy Formation from the Tully-Fisher RelationSep 30 1999New models for the formation of disk galaxies are presented. I discuss the contraints on galaxy formation that follow from fitting the model to the near-infrared Tully-Fisher (TF) relation, with an emphasis on reproducing the small amount of scatter observed. ... More
Inside-Out Bulge Formation and the Origin of the Hubble SequenceJan 29 1999A simple, inside-out formation scenario for bulges is presented. Stability arguments are used to suggest that bulges form out of the low-angular momentum baryons that cool inside a virialized dark halo: a self-regulating mechanism transforms part of the ... More
New Problems for the Formation of Disk GalaxiesAug 29 2002The standard picture for the formation of disk galaxies has come to face a number of problems related to angular momentum. Numerical simulations produce disks that are too small, and analytical models predict too much low angular momentum compared to ... More
The Universal Mass Accretion History of CDM HaloesMay 09 2001Dec 28 2001We use the extended Press-Schechter formalism to investigate the rate at which cold dark matter haloes accrete mass. We discuss the shortcomings of previous methods that have been used to compute the mass accretion histories of dark matter haloes, and ... More
Semi-Analytical Models for the Formation of Disk Galaxies: I. Constraints from the Tully-Fisher RelationSep 16 1999We present new semi-analytical models for the formation of disk galaxies with the purpose of investigating the origin of the near-infrared Tully-Fisher (TF) relation. The models assume that disks are formed by cooling of the baryons inside dark halos ... More
On the Uncertainties of the Central Density in Axisymmetric Galaxies due to DeprojectionNov 19 1996The deprojection of the surface brightness of axisymmetric galaxies is indeterminate unless the galaxy is seen edge-on. In practice, this problem is often circumvented by making ad hoc assumptions about the density distribution. However, one can redistribute ... More
Measuring the Virial Masses of Disk GalaxiesJan 02 2002I present detailed models for the formation of disk galaxies, and investigate which observables are best suited as virial mass estimators. Contrary to naive expectations, the luminosities and circular velocities of disk galaxies are extremely poor indicators ... More
The Central Mass Distribution in Dwarf and Low Surface Brightness GalaxiesOct 07 2002We present Halpha rotation curves for a sample of 15 dwarf and LSB galaxies. From these, we derive limits on the slopes of the central mass distributions. Assuming the density distributions of dark matter halos follow a power-law at small radii, rho(r)~r^(-alpha), ... More
The dependence of low redshift galaxy properties on environmentJan 17 2011We review recent results on the dependence of various galaxy properties on environment at low redshift. As environmental indicators, we use group mass, group-centric radius, and the distinction between centrals and satellites; examined galaxy properties ... More
The Origin of the Correlation between the Spin Parameter and the Baryon Fraction of Galactic DisksFeb 01 2002The puzzling correlation between the spin parameter lambda of galactic disks and the disk-to-halo mass fraction fdisk is investigated. We show that such a correlation arises naturally from uncertainties in determining the virial masses of dark matter ... More
On the Origin of the Galaxy Star-Formation-Rate Sequence: Evolution and ScatterDec 11 2009Mar 24 2010We use a semi-analytic model for disk galaxies to explore the origin of the time evolution and small scatter of the galaxy SFR sequence -- the tight correlation between star-formation rate (SFR) and stellar mass (M_star). The steep decline of SFR from ... More
The Tully-Fisher Zero Point ProblemJan 09 2008A long standing problem for hierarchical disk galaxy formation models has been the simultaneous matching of the zero point of the Tully-Fisher relation and the galaxy luminosity function (LF). We illustrate this problem for a typical disk galaxy and discuss ... More
The angular momentum of disc galaxies: implications for gas accretion, outflows, and dynamical frictionAug 02 2011Jan 07 2012We combine constraints on the galaxy-dark matter connection with structural and dynamical scaling relations to investigate the angular momentum content of disc galaxies. For haloes with masses in the interval 10^{11.3} < M_vir/M_sun < 10^{12.7} we find ... More
The Impact of Feedback on Disk Galaxy Scaling RelationsJan 19 2010We use a disk formation model to study the effects of galactic outflows (a.k.a. feedback) on the rotation velocity - stellar mass - disk size, gas fraction - stellar mass, and gas phase metalicity - stellar mass scaling relations of disk galaxies. We ... More
The Impact of Feedback on Disk Galaxy Scaling RelationsOct 28 2008May 04 2009We use a disk galaxy evolution model to investigate the impact of mass outflows (a.k.a. feedback) on disk galaxy scaling relations. Our model follows the accretion, cooling, star formation and ejection of baryonic mass inside growing dark matter haloes, ... More
Dwarf Galaxy Rotation Curves and the Core Problem of Dark Matter HalosJun 05 2000Feb 28 2001The standard cold dark matter (CDM) model has recently been challenged by the claim that dwarf galaxies have dark matter halos with constant density cores. Consequently, numerous alternative dark matter candidates have recently been proposed. In this ... More
The Angular Momentum Content of Dwarf Galaxies: New Challenges for the Theory of Galaxy FormationMay 04 2001We compute the specific angular momentum distributions of a sample of low mass disk galaxies observed by Swaters. We compare these distributions to those of dark matter haloes obtained by Bullock et al. from high resolution N-body simulations of structure ... More
Evidence for a massive BH in the S0 galaxy NGC 4342May 26 1998We present axisymmetric dynamical models of the edge-on S0 galaxy NGC 4342. A combination of observations from the ground and with the Hubble Space Telescope (HST) has shown that NGC 4342 rotates rapidly and has a strong central increase in velocity dispersion. ... More
Evidence for a Massive Black Hole in the S0 Galaxy NGC 4342Nov 11 1998We have constructed axisymmetric dynamical models of the edge-on S0 galaxy NGC 4342: simple two-integral Jeans models as well as fully general, three-integral models using a modified version of Schwarzschild's orbit superposition technique. The two-integral ... More
Comprehensive Assessment of the Too-Big-to-Fail ProblemAug 11 2015We use a semi-analytical model for the substructure of dark matter haloes to assess the too-big-to-fail (TBTF) problem. The model accurately reproduces the average subhalo mass and velocity functions, as well as their halo-to-halo variance, in N-body ... More
Bar driven evolution of S0s: the edge-on galaxy NGC 4570Apr 03 1998We present circumstantial evidence that the central region of the edge-on S0 galaxy NGC 4570, which harbors a 150 pc scale nuclear disc in addition to its main outer disc, has been shaped under the influence of a small (approx. 500pc) bar. This is based ... More
A Nuclear Disk and massive BH in NGC 4342Nov 19 1996We discuss photometric and spectroscopic data of the E/S0 galaxy NGC 4342, obtained with the Hubble Space Telescope (HST). This galaxy harbors, in addition to its outer disk, a very small, stellar disk in its nucleus. Jeans-modeling suggests the presence ... More
New Constraints on the Efficiencies of Ram-Pressure Stripping and the Tidal Disruption of Satellite GalaxiesJan 11 2008Feb 22 2008Using data from the Sloan Digital Sky Survey (SDSS) it has recently been shown that the red fraction of satellite galaxies increases with stellar mass. Semi-analytical models, however, predict red satellite fractions that are independent of stellar mass, ... More
Statistics of Dark Matter Substructure: I. Model and Universal Fitting FunctionsMar 26 2014We present a new, semi-analytical model describing the evolution of dark matter subhaloes. The model uses merger trees constructed using the method of Parkinson et al. (2008) to describe the masses and redshifts of subhaloes at accretion, which are subsequently ... More
Generating Merger Trees for Dark Matter Haloes: A Comparison of MethodsNov 20 2013Halo merger trees describe the hierarchical mass assembly of dark matter haloes, and are the backbone for modeling galaxy formation and evolution. Merger trees constructed using Monte Carlo algorithms based on the extended Press-Schechter (EPS) formalism ... More
Nuclear stellar discs in early-type galaxies --- II. Photometric propertiesJun 04 1998Hubble Space Telescope images of two early-type galaxies harboring both nuclear and outer stellar discs are studied in detail. By means of a photometric decomposition, the images of NGC 4342 and NGC 4570 are analyzed and the photometric properties of ... More
Statistics of Dark Matter Substructure: III. Halo-to-Halo VarianceOct 07 2016We present a study of unprecedented statistical power regarding the halo-to-halo variance of dark matter substructure. Using a combination of N-body simulations and a semi-analytical model, we investigate the variance in subhalo mass fractions and subhalo ... More
Statistics of Dark Matter Substructure: II. Comparison of Model with Simulation ResultsMar 26 2014We compare subhalo mass and velocity functions obtained from different simulations with different subhalo finders among each other, and with predictions from the new semi-analytical model of Jiang & van den Bosch (2014). We find that subhalo mass functions ... More
The Angular Momentum of Gas in Proto-Galaxies I. Implications for the Formation of Disk GalaxiesJan 07 2002May 06 2002We use non-radiative N-body/SPH simulations of structure formation in a LCDM cosmology to compare the angular momentum distributions of dark matter and gas in a large sample of halos. We show that the two components have identical spin parameter distributions ... More
Unification of the Fundamental Plane and Super-Massive Black Holes MassesJun 03 2016Jun 22 2016According to the Virial Theorem, all gravitational systems in equilibrium sit on a plane in the 3D parameter space defined by their mass, size and second moment of the velocity tensor. While these quantities cannot be directly observed, there are suitable ... More
Giant Memcapacitance in Topotactic Redox InterfacesMay 14 2019The possibility to develop neuromorphic computing devices able to mimic the extraordinary data processing capabilities of biological systems spurs the research on memristive systems. Memristors with additional functionalities such as robust memcapacitance ... More
Stellar Velocity Profiles and Line-Strengths out to Four Effective Radii in the Early-Type Galaxy NGC 3379Nov 18 2008We describe a new technique to measure stellar kinematics and line-strengths at large radii in nearby galaxies. Using the integral-field spectrograph SAURON as a 'photon-collector', we obtain spectra out to four effective radii (Re) in the early-type ... More
Recovering the intrinsic shape of early-type galaxiesNov 21 2008Jul 09 2009We investigate how well the intrinsic shape of early-type galaxies can be recovered when both photometric and two-dimensional stellar kinematic observations are available. We simulate these observations with galaxy models that are representative of observed ... More
Evidence for a 3 x 10^8 solar mass black hole in NGC 7052 from HST observations of the nuclear gas diskApr 20 1998We present an HST study of the nuclear region of the E4 radio galaxy NGC 7052, which has a nuclear disk of dust and gas. The WFPC2 was used to obtain B, V and I broad-band images and an H_alpha+[NII] narrow-band image. The FOS was used to obtain H_alpha+[NII] ... More
Dynamics of the nuclear gas & dust disc in the E4 radio galaxy NGC 7052Dec 12 1994We present high spatial resolution ground-based broad-band imaging, H-alpha +[NII] narrow-band imaging and long-slit spectroscopy for the E4 radio galaxy NGC 7052, which has a nuclear dust disc. We detect ionized gas with a LINER spectrum, residing also ... More
Modelling the line-of-sight contribution in substructure lensingOct 13 2017Jan 26 2018We investigate how Einstein rings and magnified arcs are affected by small-mass dark-matter haloes placed along the line-of-sight to gravitational lens systems. By comparing the gravitational signature of line-of-sight haloes with that of substructures ... More
The Dependence of Galaxy Type on Host Halo MassJul 26 2006We examine the relation between galaxy properties and environment in the SDSS DR2, quantifying environment in terms of the mass of the host halo, which is obtained with a new iterative group finder. We find that galaxy type fractions scale strongly and ... More
Origin of the Joint Distribution of Structural Parameters in Disc GalaxiesJan 13 2005We use a simple model of disc-galaxy formation in the LCDM cosmology to simultaneously reproduce the slopes, zero-points, scatter and uncorrelated residuals in the observed velocity-luminosity (VL) and radius-luminosity (RL) relations. Observed I-band ... More
The Kinematic Connection Between Galaxies and Dark Matter HaloesApr 26 2010Using estimates of dark halo masses from satellite kinematics, weak gravitational lensing, and halo abundance matching, combined with the Tully-Fisher and Faber-Jackson relations, we derive the mean relation between the optical, V_opt, and virial, V_200, ... More
Are Brightest Halo Galaxies Central Galaxies?Jan 25 2010Jul 22 2011It is generally assumed that the central galaxy in a dark matter halo, that is, the galaxy with the lowest specific potential energy, is also the brightest halo galaxy (BHG), and that it resides at rest at the centre of the dark matter potential well. ... More
Properties of Galaxy Groups in the SDSS: I.-- The Dependence of Colour, Star Formation, and Morphology on Halo MassSep 06 2005Using a large galaxy group catalogue constructed from the SDSS, we investigate the correlation between various galaxy properties and halo mass. We split the population of galaxies in early types, late types, and intermediate types, based on their colour ... More
Concentration, Spin and Shape of Dark Matter Haloes as a Function of the Cosmological Model: WMAP1, WMAP3 and WMAP5 resultsMay 14 2008Oct 01 2008We investigate the effects of changes in the cosmological parameters between the WMAP 1st, 3rd, and 5th year results on the structure of dark matter haloes. We use a set of simulations that cover 5 decades in halo mass ranging from the scales of dwarf ... More
A Revised Model for the Formation of Disk Galaxies: Low Spin and Dark-Halo ExpansionApr 27 2006Jan 09 2007We use observed rotation velocity-luminosity (VL) and size-luminosity (RL) relations to single out a specific scenario for disk galaxy formation in the LCDM cosmology. Our model involves four independent log-normal random variables: dark-halo concentration ... More
The Mass Function and Average Mass Loss Rate of Dark Matter SubhaloesSep 08 2004Mar 01 2005We present a simple, semi-analytical model to compute the mass functions of dark matter subhaloes. The masses of subhaloes at their time of accretion are obtained from a standard merger tree. During the subsequent evolution, the subhaloes experience mass ... More
Natural Downsizing in Hierarchical Galaxy FormationMay 01 2006Oct 20 2006Stellar-population analyses of today's galaxies show "downsizing", where the stars in more massive galaxies tend to have formed earlier and over a shorter time span. We show that this phenomenon is not necessarily "anti-hierarchical" but rather has its ... More
Semi-Analytical Models for the Formation of Disk Galaxies II. Dark Matter versus Modified Newtonian DynamicsDec 01 1999We present detailed semi-analytical models for the formation of disk galaxies both in a Universe dominated by dark matter (DM), and in one for which the force law is given by modified Newtonian dynamics (MOND). We tune the models to fit the observed near-infrared ... More
Disk Galaxies as Cosmological Benchmarks: Cold Dark Matter versus Modified Newtonian DynamicsJul 10 2000We discuss a comparison of models for the formation of disk galaxies both in a Universe dominated by cold dark matter (CDM) and one in which the force law is given by modified Newtonian dynamics (MOND). Our main aim is to address the claim made by McGaugh ... More
Satellite Kinematics I: A New Method to Constrain the Halo Mass-Luminosity Relation of Central GalaxiesJul 28 2008Satellite kinematics can be used to probe the masses of dark matter haloes of central galaxies. In order to measure the kinematics with sufficient signal-to-noise, one uses the satellite galaxies of a large number of central galaxies stacked according ... More
The subhalo - satellite connection and the fate of disrupted satellite galaxiesAug 19 2008Nov 14 2008In the standard paradigm, satellite galaxies are believed to be associated with the population of dark matter subhalos. In this paper, we use the conditional stellar mass functions of {\it satellite galaxies} obtained from a large galaxy group catalogue ... More
Towards Cosmological Concordance on Galactic ScalesJan 07 2003Dec 09 2003We use the observed abundance and clustering of galaxies from the 2dFGRS to determine the matter density Omega_m and the linear amplitude of mass fluctuations sigma_8. We use a method based on the conditional luminosity function, which allows straightforward ... More
The Galaxy Dark Matter ConnectionDec 01 2004What galaxy lives in what halo? The answer to this simple question holds important information regarding galaxy formation and evolution. We describe a new statistical technique to link galaxies to their dark matter haloes, or light to mass, using the ... More
On the Origin of the Dichotomy of Early-Type Galaxies: The Role of Dry Mergers and AGN FeedbackApr 06 2007Using a semi-analytical model for galaxy formation, combined with a large N-body simulation, we investigate the origin of the dichotomy among early-type galaxies. We find that boxy galaxies originate from mergers with a progenitor mass ratio $n < 2$ and ... More
The Angular Momentum of Gas in Proto-Galaxies: II -- The Impact of PreheatingAug 07 2003We examine the effect of preheating of the intergalactic medium on galaxy formation using cosmological hydrodynamical simulations. By performing simulations both with and without a simple model for preheating, we analyse and compare the angular momentum ... More
Disk Assembly and the M_BH-sigma Relation of Supermassive Black HolesJan 12 2013Recent Hubble Space Telescope (HST) observations have revealed that a majority of active galactic nuclei (AGN) at z ~ 1-3 are resident in isolated disk galaxies, contrary to the usual expectation that AGN are triggered by mergers. Here we develop a new ... More
Galaxy Groups in the SDSS DR4: II. halo occupation statisticsOct 26 2007Dec 20 2007We investigate various halo occupation statistics using a large galaxy group catalogue constructed from the SDSS DR4 with an adaptive halo-based group finder. The conditional luminosity function (CLF) is measured separately for all, red and blue galaxies, ... More
Constraining Galaxy Formation and Cosmology with the Conditional Luminosity Function of GalaxiesJul 01 2002We use the conditional luminosity function (CLF), which gives the number of galaxies with luminosities in the range [L, L+dL] that reside in a halo of mass M, to link the distribution of galaxies to that of dark matter haloes. We seek the CLF that reproduces ... More
The Gas-Phase Metallicity of Central and Satellite Galaxies in the SDSSJun 15 2012We exploit the SDSS galaxy groups catalogue of Yang et al. to study how the gas-phase metallicities of star-forming galaxies depend on environment. We find that satellite and central galaxies follow a qualitatively similar stellar mass (M_*) - gas-phase ... More
Estimating Black Hole Masses in Triaxial GalaxiesOct 05 2009Most of the super massive black hole mass estimates based on stellar kinematics use the assumption that galaxies are axisymmetric oblate spheroids or spherical. Here we use fully general triaxial orbit-based models to explore the effect of relaxing the ... More
Linking Early and Late Type Galaxies to their Dark Matter HaloesOct 22 2002Dec 09 2003(Abridged) Using data from the 2dFGRS we compute the conditional luminosity functions (CLFs) of early- and late-type galaxies. These functions give the average number of galaxies with luminosity L that reside in a halo of mass M, and are a powerful statistical ... More
Dozens of compact and high velocity-dispersion early-type galaxies in Sloan Digital Sky SurveyMar 17 2015Apr 18 2015Aims. We aim at finding candidates of potential survivors of high-redshift compact galaxies in SDSS, as targets for more detailed follow-up observations. Methods. From the virial theorem it is expected that for a given mass, compact galaxies have stellar ... More
Orbit-based dynamical models of the Sculptor dSph galaxyMay 21 2012Aug 06 2013We have developed spherically symmetric dynamical models of dwarf spheroidal galaxies using Schwarzschild's orbit superposition method. This type of modelling yields constraints both on the total mass distribution (e.g. enclosed mass and scale radius) ... More
The Population of Dark Matter Subhaloes: Mass Functions and Average Mass Loss RatesDec 10 2007Using a cosmological N-Body simulation and a sample of re-simulated cluster-like haloes, we study the mass loss rates of dark matter subhaloes, and interpret the mass function of subhaloes at redshift zero in terms of the evolution of the mass function ... More
Self-Consistent, Axisymmetric Two_Integral Models of Elliptical Galaxies with embedded Nuclear DiscsJul 05 1996Recently, observations with the Hubble Space Telescope have revealed small stellar discs embedded in the nuclei of a number of ellipticals and S0s. In this paper we construct two-integral axisymmetric models for such systems. We calculate the even part ... More
The Isophotal Structure of Early-Type Galaxies in the SDSS: Dependence on AGN Activity and EnvironmentApr 06 2007We study the dependence of the isophotal shape of early-type galaxies on their absolute B-band magnitude, their dynamical mass, and their nuclear activity and environment, using an unprecedented large sample of 847 early-type galaxies identified in the ... More
Observational Evidence for an Age Dependence of Halo BiasSep 21 2005Jan 11 2006We study the dependence of the cross-correlation between galaxies and galaxy groups on group properties. Confirming previous results, we find that the correlation strength is stronger for more massive groups, in good agreement with the expected mass dependence ... More
Galaxy Groups in the SDSS DR4: III. the luminosity and stellar mass functionsAug 05 2008Jan 14 2009Using a large galaxy group catalogue constructed from the Sloan Digital Sky Survey Data Release 4 (SDSS DR4) with an adaptive halo-based group finder, we investigate the luminosity and stellar mass functions for different populations of galaxies (central ... More
Triaxial orbit based galaxy models with an application to the (apparent) decoupled core galaxy NGC 4365Dec 03 2007We present a flexible and efficient method to construct triaxial dynamical models of galaxies with a central black hole, using Schwarzschild's orbital superposition approach. Our method is general and can deal with realistic luminosity distributions, ... More
Schwarzschild models of the Sculptor dSph galaxyOct 21 2011We have developed a spherically symmetric dynamical model of a dwarf spheroidal galaxy using the Schwarzschild method. This type of modelling yields constraints both on the total mass distribution (e.g. enclosed mass and scale radius) as well as on the ... More
Dusty Nuclear Disks and Filaments in Early Type GalaxiesFeb 16 2001We examine the dust properties of a nearby distance-limited sample of early type galaxies using the WFPC2 of the Hubble Space Telescope. Dust is detected in 29 out of 67 galaxies (43%), including 12 with small nuclear dusty disks. In a separate sample ... More
Weak Lensing by Galaxies in Groups and Clusters: I.--Theoretical ExpectationsJul 25 2006Sep 22 2006Galaxy-galaxy lensing is rapidly becoming one of the most promising means to accurately measure the average relation between galaxy properties and halo mass. In order to obtain a signal of sufficient signal-to-noise, one needs to stack many lens galaxies ... More
Discrete dynamical modelling of omega CentauriAug 22 2013We present a new framework for modelling discrete kinematic data. Current techniques typically involve binning. Our approach works directly with the discrete data and uses maximum-likelihood methods to assess the probability of the dataset given model ... More
The clustering of SDSS galaxy groups: mass and color dependenceNov 28 2007Jul 15 2008We use a sample of galaxy groups selected from the SDSS DR 4 with an adaptive halo-based group finder to probe how the clustering strength of groups depends on their masses and colors. In particular, we determine the relative biases of groups of different ... More
Concentration, Spin and Shape of Dark Matter Haloes: Scatter and the Dependence on Mass and EnvironmentAug 07 2006Apr 02 2007We use a series of cosmological N-body simulations for a flat LCDM cosmology to investigate the properties of dark matter haloes in the mass range 3.0e9-3.0e13 Msun. These properties include the concentration parameter (c), the spin parameter (lambda) ... More
Spatial and kinematic alignments between central and satellite halosJun 02 2007Dec 18 2007Based on a cosmological N-body simulation we analyze spatial and kinematic alignments of satellite halos within six times the virial radius of group size host halos (Rvir). We measure three different types of spatial alignment: halo alignment between ... More
The Cross-Correlation between Galaxies and Groups: Probing the Galaxy Distribution in and around Dark Matter HaloesApr 21 2005Jun 27 2005We determine the cross-correlation function between galaxies and galaxy groups, using both the Two-Degree Field Galaxy Redshift Survey (2dFGRS) and the Sloan Digital Sky Survey (SDSS). We study the cross-correlation as a function of group mass, and as ... More
The Phase-Space Parameters of Brightest Halo GalaxiesFeb 23 2005Mar 01 2005The brightest galaxy in a dark matter halo is expected to reside at rest at the center of the halo. In this paper we test this `Central Galaxy Paradigm' using group catalogues extracted from the 2dFGRS and the SDSS. For each group we compute a parameter, ... More
Towards Precision Supermassive Black Hole Masses using Megamaser DisksJan 04 2016Jun 04 2016Megamaser disks provide the most precise and accurate extragalactic supermassive black hole masses. Here we describe a search for megamasers in nearby galaxies using the Green Bank Telescope (GBT). We focus on galaxies where we believe that we can resolve ... More
Properties of Galaxy Groups in the SDSS: II.- AGN Feedback and Star Formation TruncationJun 19 2006Successfully reproducing the galaxy luminosity function and the bimodality in the galaxy distribution requires a mechanism that can truncate star formation in massive haloes. Current models of galaxy formation consider two such truncation mechanisms: ... More
Stellar populations across the black hole mass - velocity dispersion relationSep 19 2016Coevolution between supermassive black holes (BHs) and their host galaxies is universally adopted in models for galaxy formation. In the absence of feedback from active galactic nuclei, simulated massive galaxies keep forming stars in the local Universe. ... More
The VIRUS-P Exploration of Nearby Galaxies (VENGA): Radial Gas Inflow and Shock Excitation in NGC 1042Mar 25 2016NGC 1042 is a late type bulgeless disk galaxy which hosts a low luminosity Active Galactic Nuclei (AGN) coincident with a massive nuclear star cluster. In this paper, we present the integral-field-spectroscopy (IFS) studies of this galaxy, based on the ... More
On the Evolution of the Velocity-Mass-Size Relations of Disk-Dominated Galaxies over the Past 10 Billion YearsJun 17 2010Sep 14 2010We study the evolution of the scaling relations between maximum circular velocity, stellar mass and optical half-light radius of star-forming disk-dominated galaxies in the context of LCDM-based galaxy formation models. Using data from the literature ... More
Stellar velocity profiles and line strengths out to four effective radii in the early-type galaxies NGC 3379 and NGC 821May 29 2009We use the integral-field spectrograph SAURON to measure the stellar line-of-sight velocity distribution and absorption line strengths out to four effective radii (Re) in the early-type galaxies NGC 3379 and NGC 821. With our newly developed observing ... More
The low dark matter content of the lenticular galaxy NGC 3998May 16 2016We observed the lenticular galaxy NGC 3998 with the Mitchell Integral-Field Spectrograph and extracted line-of-sight velocity distributions out to 3 half-light radii. We constructed collisionless orbit models in order to constrain NGC 3998's dark and ... More
On the Orbital Decay of Globular Clusters in NGC1052-DF2: Testing a Baryon-Only Mass ModelFeb 15 2019The dark matter content of the ultra diffuse galaxy NGC1052-DF2, as inferred from globular cluster (GC) and stellar kinematics, carries a considerable amount of uncertainty, with current constraints also allowing for the complete absence of dark matter. ... More
Nuclear stellar discs in early-type galaxies -- I. HST and WHT observationsAug 04 1997We present multi-colour (U, V and I) photometry obtained with the second Wide Field and Planetary Camera (WFPC2) on the Hubble Space Telescope (HST), and spectra taken with the William Herschel Telescope (WHT) and the HST Faint Object Spectrograph (FOS), ... More
Cold Filamentary Accretion and the Formation of Metal Poor Globular Clusters and Halo StarsNov 24 2017Jan 11 2019We propose that cold filamentary accretion in massive galaxies at high redshift can lead to the formation of star-forming clumps in the halos of these galaxies without the presence of dark matter sub-structure. In certain cases, these clumps can be the ... More
Radial velocities in the globular cluster omega CentauriSep 08 2005We have used the ARGUS multi-object spectrometer at the CTIO 4m Blanco telescope to obtain 2756 radial velocity measurements for 1966 individual stars in the globular cluster omega Centauri brighter than blue photographic magnitude of about 16.5. Of these, ... More
Recovery of the internal orbital structure of galaxiesDec 03 2007Jan 03 2008We construct axisymmetric and triaxial galaxy models with a phase-space distribution function that depends on linear combinations of the three exact integrals of motion for a separable potential. These Abel models, first introduced by Dejonghe & Laurent ... More
Cosmological simulations of the circumgalactic medium with 1 kpc resolution: enhanced HI column densitiesAug 13 2018Oct 05 2018The circumgalactic medium (CGM), i.e. the gaseous haloes around galaxies, is both the reservoir of gas that fuels galaxy growth and the repository of gas expelled by galactic winds. Most cosmological, hydrodynamical simulations focus their computational ... More
Mass growth and mergers: direct observations of the luminosity function of LRG satellite galaxies out to z=0.7 from SDSS and BOSS imagesAug 05 2011Feb 03 2012We present a statistical study of the luminosity functions of galaxies surrounding luminous red galaxies (LRGs) at average redshifts <z>=0.34 and <z>=0.65. The luminosity functions are derived by extracting source photometry around more than 40,000 LRGs ... More
On the Orbital Decay of Globular Clusters in NGC1052-DF2: Testing a Baryon-Only Mass ModelFeb 15 2019Apr 23 2019The dark matter content of the ultra diffuse galaxy NGC1052-DF2, as inferred from globular cluster (GC) and stellar kinematics, carries a considerable amount of uncertainty, with current constraints also allowing for the complete absence of dark matter. ... More
Self-Adjointness of two dimensional Dirac operators on corner domainsFeb 13 2019We study the self-adjointenss of the two-dimensional Dirac operator with Quantum-dot and Lorentz-scalar $\delta$-shell boundary conditions, on piecewise $C^2$ domains with finitely many corners. For both models, we prove the existence of a unique self-adjoint ... More
Do not forget: Full memory in memory-based learning of word pronunciationJan 26 1998Memory-based learning, keeping full memory of learning material, appears a viable approach to learning NLP tasks, and is often superior in generalisation accuracy to eager learning approaches that abstract from learning material. Here we investigate three ... More
Intermediate model between Majority voter PCA and its Mean Field modelOct 03 2013Probabilistic Cellular Automata (PCA) are simple models used to study dynamical phase transitions. There exist mean field approximations to PCA that can be shown to exhibit a phase transition. We introduce a model interpolating between a class of PCA, ... More
Nonexistence in Thomas-Fermi-Dirac-von Weizsäcker theory with small nuclear chargesMar 23 2016We study the ionization problem in the Thomas-Fermi-Dirac-von Weizs\"acker theory for atoms and molecules. We prove the nonexistence of minimizers for the energy functional when the number of electrons is large and the total nuclear charge is small. This ... More
The central dark matter distribution of NGC 2976Oct 27 2011We study the mass distribution in the late-type dwarf galaxy NGC 2976 through stellar kinematics obtained with the VIRUS-P integral-field spectrograph and anisotropic Jeans models as a test of cosmological simulations and baryonic processes that putatively ... More