Matthew G. Walker

Himel Ghosh3
Jeffrey K J Fogel3
Charles Kuehn3
Takeo Minezaki3
Marianne Vestergaard3
3Himel Ghosh
3Jeffrey K J Fogel
3Charles Kuehn
3Takeo Minezaki
3Marianne Vestergaard
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Cooperative robotic systems provide design and implementation challenges that are not easy to solve. This paper describes a parallel implementation for evolving cooperative robotic behaviour using an island model based genetic program on a cluster computer system. The application domain is robot soccer in which two robots must cooperate to avoid collisions(More)
  • Louis E Strigari, James S Bullock, Manoj Kaplinghat, Joshua D Simon, Marla Geha, Beth Willman +1 other
  • 2008
The Milky Way has at least twenty-three known satellite galaxies that shine with luminosities ranging from about a thousand to a billion times that of the Sun. Half of these galaxies were discovered in the past few years in the Sloan Digital Sky Survey, and they are among the least luminous galaxies in the known Universe. A determination of the mass of(More)
We present a search for γ-ray emission from the direction of the newly discovered dwarf galaxy Reticulum II. Using Fermi-LAT Collaboration data, we detect a signal that exceeds expected backgrounds between ∼2-10  GeV and is consistent with annihilation of dark matter for particle masses less than a few ×10^{2}  GeV. Modeling the background as a Poisson(More)
  • Misty C Bentz, Kelly D Denney, Edward M Cackett, Matthias Dietrich, Jeffrey K J Fogel, Himel Ghosh +8 others
  • 2007
We describe results from a new ground-based monitoring campaign on NGC 5548, the best-studied reverberation-mapped AGN. We find that it was in the lowest luminosity state yet recorded during a monitoring program, namely L 5100 ¼ 4:7 ; 10 42 ergs s À1. We determine a rest-frame time lag between flux variations in the continuum and the H line of 6:3 þ2:6 À2:3(More)
  • Kelly D Denney, Misty C Bentz, Bradley M Peterson, Richard W Pogge, Edward M Cackett, Matthias Dietrich +8 others
  • 2006
We present new observations leading to an improved black hole mass estimate for the Seyfert 1 galaxy NGC 4593 as part of a reverberation-mapping campaign conducted at the MDM Observatory. Cross-correlation analysis of the H emission-line light curve with the optical continuum light curve reveals an emission-line time delay of cent ¼ 3:73 AE 0:75 days. By(More)
  • Misty C Bentz, Kelly D Denney, Edward M Cackett, Matthias Dietrich, Jeffrey K J Fogel, Himel Ghosh +8 others
  • 2006
We have undertaken a new ground-based monitoring campaign to improve the estimates of the mass of the central black hole in NGC 4151. We measure the lag time of the broad H line response compared to the optical continuum at 5100 8 and find a lag of 6:6 þ1:1 À0:8 days. We combine our data with the recent reanalysis of UVemission lines by Metzroth and(More)
In the standard cosmological model, the Universe consists mainly of two invisible substances: vacuum energy with constant mass-density ρv = Λ/(8πG) (where Λ is a 'cosmological constant' originally proposed by Einstein and G is Newton's gravitational constant) and cold dark matter (CDM) with mass density that is currently ρ DM,0 ∼ 0.3ρv. This 'ΛCDM' model(More)
Dark matter-only simulations of galaxy formation predict many more subhalos around a Milky Way-like galaxy than the number of observed satellites. Proposed solutions require the satellites to inhabit dark matter halos with masses 10(9)-10(10 )Msun at the time they fell into the Milky Way. Here we use a modelling approach, independent of cosmological(More)
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