The remnants of galaxy formation from a panoramic survey of the region around M31 (2009)
McConnachie, Alan W., Irwin, Michael J., Ibata, Rodrigo A., Dubinski, John, Widrow, Lawrence M., Martin, Nicolas F., ...
In hierarchical cosmological models, galaxies grow in mass through the continual accretion of smaller ones. The tidal disruption of these systems is expected to result in loosely bound stars...
Martin, Nicolas F., McConnachie, Alan W., Irwin, Mike, Widrow, Lawrence M., Ferguson, Annette M. N., Ibata, Rodrigo A., ...
We present the discovery of two new dwarf galaxies, Andromeda XXI and Andromeda XXII, located in the surroundings of the Andromeda and Triangulum galaxies (M31 and M33). These discoveries stem from...
Power spectrum for the small-scale Universe (2009)
Widrow, Lawrence M., Elahi, Pascal J., Thacker, Robert J., Richardson, Mark, Scannapieco, Evan
The first objects to form in a cold dark matter universe present a daunting challenge for models of structure formation. In the ultra small-scale limit, CDM structures form nearly simultaneously...
Dynamical Models for Disk Galaxies with Triaxial Halos (2008)
We construct self-consistent dynamical models for disk galaxies with triaxial, cuspy halos. We begin with an equilibrium, axisymmetric, disk-bulge-halo system and apply an artificial acceleration to...
Dynamical Blueprints for Galaxies (2008)
Widrow, Lawrence M., Pym, Brent, Dubinski, John
We present an axisymmetric, equilibrium model for late-type galaxies which consists of an exponential disk, a Sersic bulge, and a cuspy dark halo. The model is specified by a phase space distribution...
The Vcirc-sigma0 Relation of Galaxies (2007)
Courteau, Stephane, McDonald, Michael, Widrow, Lawrence M.
Courteau et al. (2007a) reported on the dependence of the ratio of a galaxy's maximum circular velocity, Vcirc, to its central velocity dispersion, sigma0, on morphology, or equivalently total light...
Courteau, Stephane, McDonald, Michael, Widrow, Lawrence M., Holtzman, Jon
We explore the dependence of the ratio of a galaxy's circular velocity, Vcirc, to its central velocity dispersion, sigma_0, on morphology, or equivalently total light concentration. Such a dependence...
Substructure around M31 : Evolution and Effects (2006)
Gauthier, Jean-Rene, Dubinski, John, Widrow, Lawrence M.
We investigate the evolution of a population of 100 dark matter satellites orbiting in the gravitational potential of a realistic model of M31. We find that after 10 Gyr, seven subhalos are...
On Universal Halos and the Radial Orbit Instability (2006)
MacMillan, Joseph D., Widrow, Lawrence M., Henriksen, Richard N.
The radial orbit instability drives dark matter halos toward a universal structure. This conclusion, first noted by Huss, Jain, and Steinmetz, is explored in detail through a series of numerical...
MACHOs in M31? Absence of evidence but not evidence of absence (2005)
Widrow, Lawrence M., Cseresnjes, Patrick, Kuijken, Konrad, Crotts, Arlin P. S., Bergier, Alexander, ...
We present results of a microlensing survey toward the Andromeda Galaxy (M31) carried out during four observing seasons at the Isaac Newton Telescope (INT). This survey is part of the larger...
HST Imaging of MEGA Microlensing Candidates in M31 (2005)
Cseresnjes, Patrick, Crotts, Arlin P. S., Bergier, Alex, Baltz, Edward A., Gyuk, Geza, ...
We investigate $HST$/ACS and WFPC2 images at the positions of five candidate microlensing events from a large survey of variability in M31 (MEGA). Three closely match unresolved sources, and two...
Equilibrium Disk-Bulge-Halo Models for the Milky Way and Andromeda Galaxies (2005)
Widrow, Lawrence M., Dubinski, John
We describe a new set of self-consistent, equilibrium disk galaxy models that incorporate an exponential disk, a Hernquist model bulge, an NFW halo and a central supermassive black hole. The models...
First Microlensing Events From The MEGA Survey Of M31 (2003)
Kuijken, Konrad H., Crotts, Arlin P. S., Sackett, Penny D., Sutherland, Will J., Uglesich, Robert R., ...
We present the first M31 candidate microlensing events from the Microlensing Exploration of the Galaxy and Andromeda (MEGA) survey. MEGA uses several telescopes to detect microlensing towards the...
Fine Structure of Dark Matter Halos and its Effect on Terrestrial Detection Experiments (2003)
Stiff, David, Widrow, Lawrence M.
Terrestrial dark matter detection experiments probe the velocity-space distribution of dark matter particles in the vicinity of the Earth. We present a novel method, to be used in conjunction with...
Disk-Bulge-Halo Models for the Andromeda Galaxy (2003)
Widrow, Lawrence M., Perrett, Kathryn M., Suyu, Sherry H.
We present a suite of semi-analytic disk-bulge-halo models for the Andromeda galaxy (M31) which satisfy three fundamental conditions: (1) internal self-consistency; (2) consistency with observational...
Origin of Galactic and Extragalactic Magnetic Fields (2002)
A variety of observations suggest that magnetic fields are present in all galaxies and galaxy clusters. These fields are characterized by a modest strength (10^{-7}-10^{-5} G) and huge spatial scale...
Multiresolution Analysis of Substructure in Dark Matter Halos (2000)
Seymour, Michael D., Widrow, Lawrence M.
Multiresolution analysis is applied to the problem of halo identification in cosmological N-body simulations. The procedure makes use of a discrete wavelet transform known as the algorithme a trous...
Semi-Analytic Models for Dark Matter Halos (2000)
Various analytic expressions have been proposed for the density profile of dark matter halos. We consider six of these expressions for which the density profile has a power-law fall-off rho...
The First Magnetic Fields (1999)
Davies, George, Widrow, Lawrence M.
We demonstrate that the Biermann battery mechanism for the creation of large scale magnetic fields can arise in a simple model protogalaxy. Analytic calculations and numerical simulations follow...
An Observational Test of Dark Matter as Cold Fractal Clouds (1999)
Irwin, Judith A., Widrow, Lawrence M., English, Jayanne
Using the VLA, we have performed the first observational test of dark matter in the form of cold, primordial fractal clouds, as envisioned by Pfenniger, Combes, & Martinet (1994) and Pfenniger &...
Relaxing and Virializing a Dark Matter Halo (1998)
Henriksen, Richard N., Widrow, Lawrence M.
Navarro, Frenk, and White have suggested that the density profiles of simulated dark matter halos have a ``universal'' shape so that a given halo can be characterized by a single free parameter which...
Searching for Machos (and other Dark Matter Candidates) in a Simulated Galaxy (1997)
Widrow, Lawrence M., Dubinski, John
We conduct gravitational microlensing experiments in a galaxy taken from a cosmological N-body simulation. Hypothetical observers measure the optical depth and event rate toward hypothetical LMCs and...
Self-Similar Approach to Violent Relaxation (1996)
Henriksen, Richard, Widrow, Lawrence M.
We consider the evolution of an initially cold, spherically symmetric system of self-gravitating particles. At early times the system undergoes self-similar collapse of the type described by Fillmore...
Davies, George, Widrow, Lawrence M.
The Schr\"odinger Method is a novel approach for modeling numerically self-gravitating, collisionless systems that may have certain advantages over N-body and phase space methods. In particular,...
Modeling Collisionless Matter in General Relativity: A New Numerical Technique (1996)
We propose a new numerical technique for following the evolution of a self-gravitating collisionless system in general relativity. Matter is modeled as a scalar field obeying the coupled Klein-Gordon...
Microlensing By a Prolate All-Macho Halo (1995)
Holder, Gilbert P., Widrow, Lawrence M.
It is widely believed that dark matter halos are flattened, that is closer to oblate than prolate. The evidence cited is based largely on observations of galaxies which do not look anything like our...
Measuring Hubble's Constant in our Inhomogeneous Universe (1995)
Shi, Xiangdong, Widrow, Lawrence M., Dursi, L. Jonathan
Recent observations of Cepheids in the Virgo cluster have bolstered the evidence that supports a Hubble constant in 70-90 km/s/Mpc range. This evidence, by and large, probes the expansion of the...
Large Scale Structure Tests of Warm Dark Matter (1995)
Colombi, Stephane, Dodelson, Scott, Widrow, Lawrence M.
Warm dark matter (WDM) is an intriguing model of structure formation from the point of view of both cosmology and particle physics. We consider a one-parameter family of WDM models. The linear power...
On Stationary, Self-Similar Distributions of a Collisionless, Self-Gravitating, Gas (1994)
Henriksen, R. N., Widrow, Lawrence M.
We study systematically stationary solutions to the coupled Vlasov and Poisson equations which have `self-similar' or scaling symmetry in phase space. In particular, we find analytically {\it all}...
Hydrogen Clouds and the MACHO/EROS Events (1994)
Henriksen, Richard N., Widrow, Lawrence M.
We propose that the recently reported MACHO/EROS events correspond to gravitational amplification by dark clouds rather than compact objects. These clouds must be very dense with $M\sim 0.1 ~M_\odot$...
Sterile Neutrinos as Dark Matter (1993)
Dodelson, Scott, Widrow, Lawrence M.
The simplest model that can accomodate a viable nonbaryonic dark matter candidate is the standard electroweak theory with the addition of right-handed or sterile neutrinos. We reexamine this model...