RR Lyrae Variables in M33. I. Evidence For a Field Halo Population

We present observations of RR Lyrae variables in the Local Group late-type spiral galaxy M33. Using the Advanced Camera for Surveys on the Hubble Space Telescope, we have identified 64 ab-type RR Lyraes in M33. We have estimated reddenings for these stars based on their minimum light V-I colors and metallicities based on their periods. From the distributions of these properties, we conclude that the RR Lyraes belong to two populations - one associated with the halo of M33 and the other with its disk. Given that RR Lyraes are produced by populations older than ~10 Gyr, this suggests that not only does the field halo of M33 contain an old component, but so does its disk. This is one of the best pieces of evidence for the existence of a halo field component in M33. Using a relation between RR Lyrae absolute magnitude and metallicity (Mv(RR) = 0.23[Fe/H] + 0.93), we estimate a mean distance modulus of = 24.67 +/- 0.08 for M33. This places M33 approximately 70 kpc beyond M31 in line-of-sight distance.Comment: 20 pages, 17 figures, accepted for publication in The Astronomical Journa

Solid-state diffusion in amorphous zirconolite

his research utilised Queen Mary's MidPlus computational facilities, supported by QMUL Research-IT and funded by EPSRC grant EP/K000128/1. We are grateful to E. Maddrell for discussions and to CSC for support

Counter Rotating Open Rotor Animation using Particle Image Velocimetry

This article describes the two accompanying fluid dynamics videos for the "Counter rotating open rotor flow field investigation using stereoscopic Particle Image Velocimetry" presented at the 64th Annual Meeting of the APS Division of Fluid Dynamics in Baltimore, Maryland, November 20-22, 2011.Comment: Videos are include

Temporal Oscillation of Conductances in Quantum Hall Effect of Bloch Electrons

We study a nonadiabatic effect on the conductances in the quantum Hall effect of two-dimensional electrons with a periodic potential. We found that the Hall and longitudinal conductances oscillate in time with a very large frequencies due to quantum fluctuation.Comment: 8 pages, 4 figure

The Richness of the Globular Cluster System of NGC 3923: Clues to Elliptical Galaxy Formation

We present new data on the globular cluster system of the elliptical galaxy NGC 3923 which show that it has the most globular clusters per unit luminosity of any non-cluster elliptical yet observed, with $S_N=6.4 \pm1.4$. NGC 3923 is also among the brightest ellipticals outside of a galaxy cluster for which the number of globular clusters has been determined. Our observation of a large number of clusters per unit luminosity (high $S_N$ value) for a bright elliptical in a sparse environment is consistent with the suggestion of Djorgovski \& Santiago that the number of globular clusters is a power law function of the luminosity with an exponent greater than one. We relate this higher specific frequency of globular clusters in more luminous galaxies to other observations which indicate that the physical conditions within elliptical galaxies at the time of their formation were dependent on galaxy mass.Comment: 13 pages + 3 figures, uuencoded postscript, to appear in ApJ Letters, UC-BERK-9