Structure Formation by Fifth Force: Power Spectrum from N-Body Simulations (2009)
Zhao, HongSheng, Maccio', Andrea, Li, Baojiu, Hoekstra, Henk, Feix, Martin
We lay out the framework to numerically study nonlinear structure formation in the context of scalar-field-coupled cold dark matter models (phiCDM models) where the scalar field phi serves as...
Universality of galactic surface densities within one dark halo scale-length (2009)
Gentile, Gianfranco, Famaey, Benoit, Zhao, HongSheng, Salucci, Paolo
It was recently discovered that the mean dark matter surface density within one dark halo scale length - the radius within which the volume density profile of dark matter remains approximately flat -...
On the separation between baryonic and dark matter: evidence for phantom dark matter? (2009)
Knebe, Alexander, Llinares, Claudio, Wu, Xufen, Zhao, HongSheng
The recent years have seen combined measurements of X-ray and (weak) lensing contours for colliding galaxy clusters such as, for instance, the famous "Bullet" cluster. These observations have...
Kinematics at the Edge of the Galactic Bulge: Evidence for Cylindrical Rotation (2009)
Howard, Christian D., Rich, R. Michael, Clarkson, Will, Mallery, Ryan, Kormendy, John, De Propris, Roberto, ...
We present new results from BRAVA, a large scale radial velocity survey of the Galactic bulge, using M giant stars selected from the Two Micron All Sky Survey catalogue as targets for the Cerro...
Structure Formation by Fifth Force I: N-Body vs. Linear Simulations (2009)
We lay out the frameworks to numerically study the structure formation in both linear and nonlinear regimes in general dark-matter-coupled scalar field models, and give an explicit example where the...
A Realistic Cosmology Without Cold Dark Matter (2009)
We propose a new framework unifying cold dark matter (CDM) and Modified Newtonian Dynamics (MOND) to solve their respective problems on galactic scales and large scale structure formation. In our...
N-body simulations for testing the stability of triaxial galaxies in MOND (2009)
Wu, Xufen, Zhao, HongSheng, Wang, Yougang, Llinares, Claudio, Knebe, Alexander
We perform a stability test of triaxial models in MOdified Newtonian Dynamics (MOND) using N-body simulations. The triaxial models considered here have densities that vary with $r^{-1}$ in the center...
Physics of galactic colliders: high speed satellites in LCDM vs MONDian cosmology (2009)
Llinares, Claudio, Zhao, HongSheng, Knebe, Alexander
The statistics of high speed satellite galaxies, as reported in the recent literature, can be a powerful diagnosis of the depth of the potential well of the host halo, and hence discriminate between...
An ecological approach to problems of Dark Energy, Dark Matter, MOND and Neutrinos (2008)
Modern astronomical data on galaxy and cosmological scales have revealed powerfully the existence of certain dark sectors of fundamental physics, i.e., existence of particles and fields outside the...
Tian, Lanlan, Hoekstra, Henk, Zhao, Hongsheng
We study the amplitude of the weak gravitational lensing signal as a function of stellar mass around a sample of relatively isolated galaxies. This selection of lenses simplifies the interpretation...
Zhao, Hongsheng, Chang, Aimin, Wang, Yunlan
First principles study of structural, elastic, and electronic properties of the cubic perovskitetype BaHfO$_3$ has been performed using the plane wave ultrasoft pseudo-potential method based on...
Cosmological Structure Formation under MOND: a new numerical solver for Poisson's equation (2008)
Llinares, Claudio, Knebe, Alexander, Zhao, HongSheng
We present a novel solver for an analogue to Poisson's equation in the framework of modified Newtonian dynamics (MOND). This equation is highly non-linear and hence standard codes based upon tree...
The Galactic potential and the asymmetric distribution of hypervelocity stars (2008)
Perets, Hagai B., Wu, Xufen, Zhao, HongSheng, Famaey, Benoit, Gentile, Gianfranco, Alexander, Tal
In recent years several hypervelocity stars (HVSs) have been observed in the halo of our Galaxy. Such HVSs have possibly been ejected from the Galactic center and then propagated in the Galactic...
The Bulge Radial Velocity Assay (BRAVA): I. Sample Selection and a Rotation Curve (2008)
Howard, Christian D., Rich, R. Michael, Reitzel, David B., Koch, Andreas, De Propris, Roberto, Zhao, HongSheng
Results from the Bulge Radial Velocity Assay (BRAVA) are presented. BRAVA uses M giant stars, selected from the 2MASS catalog to lie within a bound of reddening corrected color and luminosity, as...
MOND plus classical neutrinos not enough for cluster lensing (2008)
Natarajan, Priyamvada, Zhao, Hongsheng
Clusters of galaxies offer a robust test bed for probing the nature of dark matter that is insensitive to the assumption of the gravity theories. Both Modified Newtonian Dynamics (MOND) and General...
Testing Alternative Theories of Dark Matter with the CMB (2008)
Li, Baojiu, Barrow, John D., Mota, David F., Zhao, HongSheng
We propose a method to study and constrain modified gravity theories for dark matter using CMB temperature anisotropies and polarization. We assume that the theories considered here have already...
Reinterpreting MOND: coupling of Einsteinian gravity and spin of cosmic neutrinos? (2008)
Several rare coincidences of scales in standard particle physics are needed to explain (i) why neutrinos have mass, (ii) why the negative pressure of the cosmological dark energy (DE) coincides with...
An analytic model for non-spherical lenses in covariant MOdified Newtonian Dynamics (2008)
Shan, HuanYuan, Feix, Martin, Famaey, Benoit, Zhao, HongSheng
Strong gravitational lensing by galaxies in MOdified Newtonian Dynamics (MOND) has until now been restricted to spherically symmetric models. These models were able to account for the size of the...
Empirical theories of Dark Matter like MOND gravity and of Dark Energy like f(R) gravity were motivated by astronomical data. But could these theories be branches rooted from a more general hence...
Milky Way potentials in CDM and MOND. Is the Large Magellanic Cloud on a bound orbit? (2008)
Wu, Xufen, Famaey, Benoit, Gentile, Gianfranco, Perets, Hagai, Zhao, HongSheng
We compute the Milky Way potential in different cold dark matter (CDM) based models, and compare these with the modified Newtonian dynamics (MOND) framework. We calculate the axis ratio of the...
An Uneven Vacuum Energy Fluid as $\Lambda$, Dark Matter, MOND and Lens (2008)
Various TeVeS-inspired and f(R)-inspired theories of gravity have added an interesting twist to the search for dark matter and vacuum energy, modifying the landscape of astrophysics day by day. These...
Galaxy Bulges As Tests of CDM vs MOND in Strong Gravity (2008)
Zhao, HongSheng, Xu, Bing-Xiao, Dobbs, Clare
The tight correlation between galaxy bulges and their central black hole masses likely emerges in a phase of rapid collapse and starburst at high redshift, due to the balance of gravity on gas with...
Self-consistent models of triaxial galaxies in MOND gravity (2008)
Wang, You-gang, Wu, Xufen, Zhao, HongSheng
The Bekenstein-Milgrom gravity theory with a modified Poisson equation is tested here for the existence of triaxial equilibrium solutions. Using the non-negative least square method, we show that...
Debris streams in the solar neighbourhood as relicts from the formation of the Milky Way (2007)
Amina Helmi Simon, Hongsheng Zhao
motions of typical halo stars 3 . A second dichotomy distinguished "dissipationless" galaxy formation, in which stars formed before collapse 4 , from "dissipative" models in which...
Halle, Anaelle, Zhao, HongSheng, Li, Baojiu
We propose a unified single-field description of the galactic Dark Matter and various uniform scalar fields for the inflation and cosmological constant. The two types of effects could originate from...
Kinematics and Composition of the Galactic Bulge: Recent Progress (2007)
Rich, R. Michael, Howard, Christian, Reitzel, David B., Zhao, HongSheng, De Propris, Roberto
We present recent results from a Keck study of the composition of the Galactic bulge, as well as results from the bulge Bulge Radial Velocity Assay (BRAVA). Culminating a 10 year investigation,...
Is Gravitational Lensing by Intercluster Filaments Always Negligible? (2007)
Feix, Martin, Xu, Dong, Shan, HuanYuan, Famaey, Benoit, Limousin, Marceau, Zhao, HongSheng, ...
Intercluster filaments negligibly contribute to the weak lensing signal in general relativity (GR), $\gamma_{N}\sim 10^{-4}-10^{-3}$. In the context of relativistic modified Newtonian dynamics (MOND)...
Coincidences of Dark Energy with Dark Matter -- Clues for a Simple Alternative? (2007)
A rare coincidence of scales in standard particle physics is needed to explain why $\Lambda$ or the negative pressure of cosmological dark energy (DE) coincides with the positive pressure $P_0$ of...
How to form bulges/ellipticals in dark halos as fast as central black holes? (2007)
Zhao, HongSheng, Xu, Bing-Xiao, Wu, Xue-Bing
Gravity is nearly a universal constant in the cusp of an NFW galaxy halo. Inside this external field an isothermal gas sphere will collapse and trigger a starburst if above a critical central...
The velocity distribution of SDSS satellites in MOND (2007)
Angus, Garry, Famaey, Benoit, Tiret, Olivier, Combes, Francoise, Zhao, HongSheng
The recent SDSS measured velocity distribution of satellite galaxies has been modelled in the context of MOND. We show that even when the extra constraint of adhering to the projected satellite...
Mapping the dark trajectory of the Bullet Cluster (2007)
We model the electrons/positrons produced by dark matter annihilations in the colliding galaxy cluster system 1E0657-56 (the bullet cluster). These charged particles, confined by the Magnetic field,...
Loss of mass and stability of galaxies in MOND (2007)
Wu, Xufen, Zhao, HongSheng, Famaey, Benoit, Gentile, G., Tiret, O., Combes, F., ...
The self-binding energy and stability of a galaxy in MOND-based gravity are curiously decreasing functions of its center of mass acceleration towards neighbouring mass concentrations. A tentative...
Vertical dynamics of disk galaxies in MOND (2007)
Nipoti, Carlo, Londrillo, Pasquale, Zhao, HongSheng, Ciotti, Luca
We investigate the possibility of discriminating between Modified Newtonian Dynamics (MOND) and Newtonian gravity with dark matter, by studying the vertical dynamics of disk galaxies. We consider...
We present semi-analytical constraint on the amount of dark matter in the merging bullet galaxy cluster using the classical Local Group timing arguments. We consider particle orbits in potential...
Famaey, Benoit, Bruneton, Jean-Philippe, Zhao, HongSheng
We present a new test of modified Newtonian dynamics (MOND) on galactic scales, based on the escape speed in the solar neighbourhood. This test is independent from other empirical successes of MOND...
Galaxy Bulge Formation: Interplay with Dark Matter Halo and Central Supermassive Black Hole (2007)
Xu, Bing-Xiao, Wu, Xue-Bing, Zhao, HongSheng
We present a simple scenario where the formation of galactic bulges was regulated by the dark halo gravity and regulated the growth of the central supermassive black hole. Assuming the angular...
Tidal Disruption of the First Dark Microhalos (2007)
Zhao, HongSheng, Hooper, Dan, Angus, Garry W., Taylor, James E., Silk, Joseph
We point out that the usual self-similarity in cold dark matter models is broken by encounters with individual normal galactic stars on a subparsec scale. Tidal heating and stripping must have...
An introduction to Gravitational Lensing in TeVeS gravity (2006)
Bekenstein's (2004) TeVeS theory has added an interesting twist to the search for dark matter and dark energy, modifying the landscape of gravity-related astronomy day by day. Built bottom-up rather...
The diffuse Galactic gamma-rays from dark matter annihilation (2006)
Bi, Xiao-Jun, Zhang, Juan, Yuan, Qiang, Zhang, Jian-Li, Zhao, HongSheng
The diffuse Galactic $\gamma$-rays from EGRET observation shows excesses above 1 GeV in comparison with the expectations from conventional Galactic cosmic ray (CR) propagation model. In the work we...
The Bulge Radial Velocity Assay (BRAVA): I. Techniques and a Rotation Curve (2006)
Rich, R. Michael, Reitzel, David B., Howard, Christian D., Zhao, HongSheng
We are undertaking a large scale radial velocity survey of the Galactic bulge which uses M giant stars selected from the 2MASS catalog as targets for the CTIO 4m Hydra multi-object spectrograph. The...
Insight into the baryon-gravity relation in galaxies (2006)
Famaey, Benoit, Gentile, Gianfranco, Bruneton, Jean-Philippe, Zhao, HongSheng
Observations of spiral galaxies strongly support a one-to-one analytical relation between the inferred gravity of dark matter at any radius and the enclosed baryonic mass. It is baffling that baryons...
Constraining TeVeS Gravity as Effective Dark Matter and Dark Energy (2006)
The phenomena customly described with the standard $\Lambda$CDM model are broadly reproduced by an extremely simple model in TeVeS, Bekenstein's (2004) modification of General Relativity motivated by...
On the Proof of Dark Matter, the Law of Gravity and the Mass of Neutrinos (2006)
Angus, Garry W., Shan, HuanYuan, Zhao, HongSheng, Famaey, Benoit
We develop a new method to predict the density associated with weak lensing maps of (un)relaxed clusters in a range of theories interpolating between GR and MOND (General Relativity and Modified...
Analysis of galactic tides and stars on CDM microhalos (2006)
Angus, Garry W., Zhao, HongSheng
A special purpose N-body simulation has been built to understand the tidal heating of the smallest dark matter substructures ($10^{-6}\msun$ and 0.01pc) from the grainy potential of the Milky Way due...
Strong lensing probability for testing TeVeS theory (2006)
Chen, Da-Ming, Zhao, HongSheng
We calculate the strong lensing probability as a function of the image-separation $\Delta\theta$ in TeVeS (tensor-vector-scalar) cosmology, which is a relativistic version of MOND (MOdified Newtonian...
Angus, Garry W., Famaey, Benoit, Zhao, HongSheng
A proper test of Modified Newtonian Dynamics (MOND) in systems of non-trivial geometries depends on modelling subtle differences in several versions of its postulated theories. This is especially...
Refining MOND interpolating function and TeVeS Lagrangian (2005)
Zhao, HongSheng, Famaey, Benoit
The phenomena customly called Dark Matter or Modified Newtonian Dynamics (MOND) have been argued by Bekenstein (2004) to be the consequences of a covariant scalar field, controlled by a free function...
Roche Lobe Shapes for testing MOND-like Modified Gravity (2005)
Dark Matter (DM) theories and mass-tracing-light theories like MOND are by construction nearly degenerate on galactic scales, but not when it comes to the predicted shapes of Roche Lobes of a...
Roche Lobe Sizes in Deep-MOND Gravity (2005)
MOdified Newtonian Dynamics (MOND) is evolving from an empirical to a decent theory respecting fundamental physics after Bekenstein (2004) showed that lensing and Hubble expansion can be modeled...
Testing Bekenstein's Relativistic MOND gravity with Lensing Data (2005)
Zhao, HongSheng, Bacon, David J., Taylor, Andy N., Horne, Keith
We propose to use multiple-imaged gravitational lenses to set limits on gravity theories without dark matter, specificly TeVeS (Bekenstein 2004), a theory which is consistent with fundamental...
A review on success and problem of MOND on globular cluster scale (2005)
Many past attempts to kill MOND have only strengthened the theory. Better data on galaxy velocity curves clearly favor MOND (without fine-tuning) over cold dark matter. The usual critism on the...
Tidal Destruction of The First Dark Microhalos (2005)
Zhao, HongSheng, Hooper, Dan, Angus, Garry W., Taylor, James E., Silk, Joseph
We point out that the usual self-similarity in cold dark matter models is broken by encounters with individual normal galactic stars on sub-pc scale. Tidal heating and stripping must have redefined...
Earth-mass dark halos are torn into dark mini-streams by stars (2005)
Zhao, HongSheng, Taylor, James E., Silk, Joseph, Hooper, Dan
The promising neutralino dark matter particles generically condense into numerous earth-mass dark halos with smaller substructures suppressed by free streaming\cite{berezinsky}. The recent {\it...
Mini-dark halos with intermediate mass black holes (2005)
We argue that the Milky Way (MW) contains thousands intermediate mass black holes (IMBHs) and minihalos with a fraction of IMBHs still being enshrouded in extremely dense mini-spikes of dark matter...
How fast a satellite decays its orbit depends on how slowly its mass is lost by tide. Motivated by inner halo satellite remnants like the Sgr and Omega Cen, we develop fully analytical models to...
Can satellites deliver substructures and black holes to inner halo by dynamical friction? (2003)
A fully analytical formulation is developed to make dynamical friction modeling more realistic. The rate for a satellite to decay its orbit in a host galaxy halo is often severely overestimated when...
Kinematic outliers in the LMC: constraints on star-star microlensing (2002)
Zhao, HongSheng, Ibata, Rodrigo, Lewis, Geraint, Irwin, Mike
Although a decade of microlensing searches towards the Large Magellanic Cloud (LMC) has detected 13-25 possible microlensing events, the nature and the location of the lenses, being either halo...
Isothermal models and other simple smooth models of dark matter halos of gravitational lenses often predict a dimensionless time delay $H_0\Delta t$ much too small to be comfortable with the observed...
A degeneracy in strong lens model is shown analytically. The observed time delays and quasar image positions might {\it not} uniquely determine the concentration and the extent of the lens galaxy...
Dynamical limits on galactic winds, halo machos and intergalactic globular clusters (2002)
We argue that any violent galactic winds following early epoch of star bursts would significantly weaken the potentials of galaxies, and leave lasting signatures such as a lowered dark halo density...
The Unique History of the Globular Cluster Omega Centauri (2002)
Gnedin, Oleg Y., Zhao, HongSheng, Pringle, J. E., Fall, S. Michael, Livio, Mario, Meylan, Georges
Using current observational data and simple dynamical modeling, we demonstrate that Omega Cen is not special among the Galactic globular clusters in its ability to produce and retain the heavy...
Feeding black holes at galactic centres by capture from isothermal cusps (2001)
Zhao, HongSheng, Haehnelt, Martin G., Rees, Martin J.
We estimate the rate at which stars are captured by supermassive black holes (BHs) in the centres of bulges and elliptical galaxies assuming that these initially had an isothermal cusp (rho ~ r^{-2}...
We simulate the result of orbital decay for a dwarf satellite galaxy in a disk galaxy potential. The peeling-off of the satellite by the strong tidal field within the disk of the host galaxy quickly...
Flux ratios as a probe of dark substructures in quadruple-image gravitational lenses (2001)
Metcalf, R. Benton, Zhao, HongSheng
We demonstrate that the flux ratios of 4-image lensed quasars provide a powerful means of probing the small scale structure of Dark Matter (DM) halos. A family of smooth lens models can precisely...
Klessen, Ralf, Zhao, HongSheng
The failure of standard cosmolocical models in accounting for the statistics of dwarf satellites and the rotation curve of gas-rich dwarf galaxies in detail has led us to examine whether earlier...
LCDM-based models for the Milky Way and M31 I: Dynamical Models (2001)
Klypin, Anatoly, Zhao, HongSheng, Somerville, Rachel S.
We apply standard disk formation theory with adiabatic contraction within cuspy halo models predicted by the standard LCDM cosmology. The resulting models score remarkably well when confronted with...
Maximum Feedback and Dark Matter Profiles of Dwarf Galaxies (2001)
Gnedin, Oleg Y., Zhao, HongSheng
The observed rotation curves of dark matter-dominated dwarf galaxies indicate low density cores, contrary to the predictions of CDM models. A possible solution of this problem involves stellar...
A Dark-Matter Spike at the Galactic Center? (2001)
Ullio, Piero, Zhao, HongSheng, Kamionkowski, Marc
The past growth of the central black hole (BH) might have enhanced the density of cold dark matter halo particles at the Galactic center. We compute this effect in realistic growth models of the...
Dark-matter spike at the galactic center? (2001)
Ullio, Piero, HongSheng Zhao, Kamionkowski, Marc
The past growth of the central black hole (BH) might have enhanced the density of cold dark matter halo particles at the Galactic center. We compute this effect in realistic growth models of the...
Dynamics of the Galactic Bulge using Planetary Nebulae (2000)
Beaulieu, Sylvie F., Freeman, Kenneth C., Kalnajs, Agris J., Saha, Prasenjit, Zhao, HongSheng
Evidence for a bar at the center of the Milky Way triggered a renewed enthusiasm for dynamical modelling of the Galactic bar-bulge. Our goal is to compare the kinematics of a sample of tracers,...
While the Hubble constant can be derived from observable time delays between images of lensed quasars, the result is often highly sensitive to assumptions and systematic uncertainties in the lensing...
Deprojection of light distributions of nearby systems: perspective effect and non-uniqueness (1999)
Deriving the 3-dimensional volume density distribution from a 2-dimensional light distribution of a system yields generally non-unique results. The case for nearby dust-free systems is studied,...
Debris streams in the solar neighbourhood as relicts from the formation of the Milky Way (1999)
Helmi, Amina, White, Simon D. M., De Zeeuw, P. Tim, Zhao, HongSheng
It is now generally believed that galaxies were built up through gravitational amplification of primordial fluctuations and the subsequent merging of smaller precursor structures. The stars of the...
Magnitude bias of microlensed sources towards the Large Magellanic Cloud (1999)
Zhao, HongSheng, Graff, David, Guhathakurta, Puragra
There are lines of evidence suggesting that some of the observed microlensing events in the direction of the Large Magellanic Cloud (LMC) are caused by ordinary star lenses as opposed to dark Machos...
Evolution of the Galactic Potential and Halo Streamers with Future Astrometric Satellites (1999)
Zhao, HongSheng, Johnston, Kathryn, Hernquist, Lars, Spergel, David
ESA's Global Astrometric Interferometer for Astrophysics (GAIA) holds the promise of mapping out the detailed phase space structure of the Galactic halo by providing unprecedented annual proper...
Extinction bias of microlensed stars towards the LMC and the fraction of machos in the halo (1999)
We study the effect of reddening on microlensed stars towards the LMC. If lenses are in the LMC disk, then the source stars should be at the far side or behind the LMC disk. Thus they should...
The pendulum dilemma of fish orbits (1999)
The shape of a galaxy is constrained both by mechanisms of formation (dissipational vs. dissipationless) and by the available orbit families (the shape and amount of regular and stochastic orbits)....
Reddening of microlensed LMC stars vs. the location of the lenses (1999)
We propose an observational test that can break the degeneracy of two main classes of microlensing models to the Magellanic Clouds: (a) the lenses are located in the Galactic halo, and (b) the lenses...
A Radial Velocity Survey for LMC Microlensed Sources (1999)
We propose a radial velocity survey with the aim to resolve the current dispute on the LMC lensing: in the pro-macho hypothesis the lenses are halo white dwarfs or machos in general; in the pro-star...
What Could the Machos Be? (1999)
If the Universe has a significant baryonic dark component in the form of compact objects in galaxy halos (machos), then there is a minute chance (about $10^{-7}$) that one of the Galactic machos...
Building galaxy models with Schwarzschild method and spectral dynamics (1999)
Tremendous progress has been made recently in modelling the morphology and kinematics of centers of galaxies. Increasingly realistic models are built for central bar, bulge, nucleus and black hole of...
Can galactic nuclei be non-axisymmetric? --- The parameter space of power-law discs (1999)
Zhao, HongSheng, Carollo, Marcella, De Zeeuw, Tim
The shape of a cusped galactic nucleus is constrained by the range of shapes of orbits in its gravitational potential. It is shown for scale-free non-axisymmetric discs that while a plausible...
Zhao, HongSheng, Johnston, Kathryn, Spergel, David, Hernquist, Lars
Future astrometric satellites, such as SIM (NASA's Space Interferometric Mission) and GAIA (ESA's Global Astrometric Interferometer for Astrophysics), hold the promise of mapping out the detailed...
Detecting Halo Streams with GAIA (1998)
Helmi, Amina, Zhao, HongSheng, De Zeeuw, P. Tim
We investigate what the proposed ESA astrometric satellite GAIA will reveal by observing the halo of the Milky Way. Specifically, we look for halo streams which are the signatures left by the...
Tidal Streams as Probes of the Galactic Potential (1998)
Johnston, Kathryn V., Zhao, HongSheng, Spergel, David N., Hernquist, Lars
We explore the use of tidal streams from Galactic satellites to recover the potential of the Milky Way. Our study is motivated both by the discovery of the first lengthy stellar stream in the halo...
The survival of the Sgr dwarf galaxy and the flatness of the rotation curve of the Galaxy (1998)
How has the ``fluffy'' core of the Sgr dwarf galaxy survived multiple strong shocks from the tidal force of the Galactic halo and disc since the formation of the core a Hubble time ago? A scenario...
The microlensing rate and mass function vs. dynamics of the Galactic bar (1997)
Zhao, HongSheng, De Zeeuw, P. Tim
With the steady increase of the sample size of observed microlenses towards the central regions of the Galaxy, the main source of the uncertainty in the lens mass will shift from the simple Poisson...
Gerhard, Ortwin, Binney, James, Zhao, HongSheng
We summarize recent work on the structure and dynamics of the Galactic bar and inner disk. Current work focusses on constructing a quantitative model which integrates NIR photometry, source count...
Density cusps: restrictions on non-axisymmetric models (1997)
Galactic nuclei are now generally thought to have density cusps in their centres, and the evidence is mounting that as a consequence they are unlikely to be triaxial. Self-consistent stellar...
Origin of non-unique deprojection of the Galactic bar (1997)
Non-uniqueness of deprojecting the integrated light distribution of a nearby or faraway triaxial body is reviewed in the context of deriving the volume density of the Galactic bar from the COBE/DIRBE...
Microlensing of tidal debris on the Magellanic great circle (1997)
Increasing evidences suggest that the Galactic halo is lumpy on kpc scales due to the accretion of at least a dozen small galaxies (LMC/SMC, Sgr, Fornax etc.). Faint stars in such lumpy structures...
The discovery of the Sgr dwarf galaxy (Ibata, Gilmore, Irwin 1994) shows that the Galactic halo contains large clumps which are not full viralized. Stars in such a clump can lense a background...
Analytical Dynamical Models for Double-Power-Law Galactic Nuclei (1996)
Motivated by the finding that the observed surface brightness profile of many galactic nuclei are well fit by double-power-laws, we explore a range of spherical self-consistent dynamical models with...
On the Microlensing Optical Depth of the Galactic Bar (1996)
The microlensing probability (optical depth $\tau$) toward the Galactic center carries information about the mass distribution of the Galactic bulge/bar, so can be used to constrain the very...
A Self-Consistent Dynamical Model for the COBE Detected Galactic Bar (1995)
A 3D steady state stellar dynamical model for the Galactic bar is constructed with 485 orbit building blocks using an extension of Schwarzschild technique. The weights of the orbits are assigned...
A Consistent Microlensing Model for the Galactic Bar (1995)
Zhao, HongSheng, Rich, R. M., Spergel, D. N.
We compute a microlensing map for the Galactic bar. The predicted event rate and event duration distribution are consistent with the $55$ events recently reported by the MACHO and OGLE...
New Parametrizations of Non-Gaussian Line-of-sight Velocity Distribution (1995)
Zhao, HongSheng, Prada, Francisco
A five-parameter fitting formula for the line-of-sight stellar velocity distributions of steady state systems is proposed. It can faithfully reproduce velocity distributions of theoretical models...
Analytical Models For Galactic Nuclei (1995)
I present a general family of dynamical models with simple analytical potential-density pairs suited to model galactic bulges and nuclei with double power-law radial density profiles and an optional...
A self-consistent stellar dynamical model for the Galactic bar is constructed from about 500 numerically computed orbits with an extension of the Schwarzschild technique. The model fits the {\sl...
Signatures of Bulge Triaxiality from Kinematics in Baade's Window/ (1994)
Zhao, HongSheng, Spergel, D. N., Rich, R. M.
We study a sample of 62 Baade's Window (1,-4) K giants that have published proper motions, radial velocity and metallicity. We construct the velocity ellipsoids for the metal rich stars and metal...
Microlensing by the Galactic Bar (1994)
Zhao, HongSheng, Spergel, David N., Rich, R. Michael
We compute the predicted optical depth and duration distribution of microlensing events towards Baade's window in a model composed of a Galactic disk and a bar. The bar model is a self-consistent...
Modelling the galactic bar--[microform] /--HongSheng Zhao. (1994)
Department: Astronomy