Professor James Binney FRS

Abstract:

We re-examine the method of deprojection of proper motions, which has been used for finding the velocity ellipsoid of stars in the nearby Galaxy. This method is only legitimate if the lines of sight to the individual stars are uncorrelated with the stars' velocities. Very simple models are used to show that spurious results similar to ones recently reported are obtained when velocity dispersion decreases with galactocentric radius in the expected way. A scheme that compensates for this bias is proposed.

Abstract:

The Galaxy's stellar halo seems to be a tangle of disrupted systems that have been tidally stretched out into streams. Each stream approximately delineates an orbit in the Galactic force-field. In the first paper in this series we showed that all six phase-space coordinates of each point on an orbit can be reconstructed from the orbit's path across the sky and measurements of the line-of-sight velocity along the orbit. In this paper we complement this finding by showing that the orbit can also be reconstructed if we know proper motions along the orbit rather than the radial velocities. We also show that accurate proper motions of stream stars would enable distances to be determined to points on the stream that are independent of any assumption about the Galaxy's gravitational potential. Such "Galactic parallaxes" would be as fundamental as conventional trigonometric parallaxes, but measureable to distances ~70 times further.

Abstract:

Context. The RAVE spectroscopic survey for galactic structure and evolution obtains 8400-8800 Å spectra at 7500 resolving power at the UK Schmidt Telescope using the 6dF multi-fiber positioner. More than 300 000 9 ≤ I C ≤ 12 and |b|≥ 25° southern stars have been observed to date. Aims. This paper presents the first intrinsic examination of stellar spectra from the RAVE survey, aimed at evaluating their diagnostic potential for peculiar stars and at contributing to the general understanding of luminous blue variables (LBVs). Methods. We used the multi-epoch spectra for all seven LBVs observed, between 2005 and 2008, in the Large Magellanic Cloud (LMC) by the RAVE survey. Results. We demonstrate that RAVE spectra possess significant diagnostic potential when applied to peculiar stars and, in particular, LBVs. The behaviour of the radial velocities for both emission and absorption lines, and the spectral changes between outburst and quiescence states are described and found to agree with evidence gathered at more conventional wavelengths. The wind outflow signatures and their variability are investigated, with multi-components detected in S Doradus. Photoionisation modelling of the rich emission line spectrum of R 127 shows evidence of a massive detached ionised shell that was ejected during the 1982-2000 outburst. Surface inhomogeneities in the nuclear-processed material, brought to the surface by heavy mass loss, could have been observed in S Doradus, even if alternative explanations are possible. We also detect the transition from quiescence to outburst state in R 71. Finally, our spectrum of R 84 offers one of the clearest views of its cool companion. © ESO 2009.

Abstract:

In this study, the role of presence in the imitation of a virtual model was examined. Immersive virtual environment technology (IVET) was used to create photorealistic virtual representations of the self that were depicted eating food in a virtual world. Changes in the virtual environment (via a changing or unchanging body) were incorporated to create variance in perceived subjective presence. Based on previous research, presence was hypothesized to affect the relationship between the environmental manipulations and the behavioral outcome of imitating the avatar's eating behavior. Here we show that presence did indeed affect imitation, but that the effects varied for men and women in accordance with previous research on sex differences in eating behavior. Men who experienced high presence were more likely than low presence men to imitate the virtual model and eat candy, whereas women who experienced high presence were more likely than low presence women to suppress the behavior and not eat candy. © 2009 by the Massachusetts Institute of Technology.

Abstract:

We reanalyse the measurements of parallax, proper motion, and line-of-sight velocity for 18 masers in high mass star-forming regions presented by Reid et al. (2009). We use a likelihood analysis to investigate the distance of the Sun from the Galactic centre, R_0, the rotational speed of the local standard of rest, v_0, and the peculiar velocity of the Sun, vsol, for various models of the rotation curve, and models which allow for a typical peculiar motion of the high mass star-forming regions. We find that these data are best fit by models with non-standard values for vsol or a net peculiar motion of the high mass star-forming regions. We argue that a correction to vsol is much more likely, and that these data support the conclusion of Binney (2009) that V_sol should be revised upwards from 5.2 km/s to 11 km/s. We find that the values of R_0 and v_0 that we determine are heavily dependent on the model we use for the rotation curve, with model-dependent estimates of R_0 ranging from 6.7 \pm 0.5kpc to 8.9 \pm 0.9kpc, and those of v_0 ranging from 200 \pm 20 km/s to 279 \pm 33 km/s. We argue that these data cannot be thought of as implying any particular values of R_0 or v_0. However, we find that v_0/R_0 is better constrained, lying in the range 29.9-31.6 km/s/kpc for all models but one.