Shrinking binary and planetary orbits by Kozai cycles with tidal friction

At least two arguments suggest that the orbits of a large fraction of binary stars and extrasolar planets shrank by 1-2 orders of magnitude after formation: (i) the physical radius of a star shrinks by a large factor from birth to the main sequence, yet many main-sequence stars have companions orbiting only a few stellar radii away, and (ii) in current theories of planet formation, the region within ~0.1 AU of a protostar is too hot and rarefied for a Jupiter-mass planet to form, yet many "hot Jupiters" are observed at such distances. We investigate orbital shrinkage by the combined effects of secular perturbations from a distant companion star (Kozai oscillations) and tidal friction. We integrate the relevant equations of motion to predict the distribution of orbital elements produced by this process. Binary stars with orbital periods of 0.1 to 10 days, with a median of ~2 d, are produced from binaries with much longer periods (10 d to 10^5 d), consistent with observations indicating that most or all short-period binaries have distant companions (tertiaries). We also make two new testable predictions: (1) For periods between 3 and 10 d, the distribution of the mutual inclination between the inner binary and the tertiary orbit should peak strongly near 40 deg and 140 deg. (2) Extrasolar planets whose host stars have a distant binary companion may also undergo this process, in which case the orbit of the resulting hot Jupiter will typically be misaligned with the equator of its host star.Comment: Submitted to ApJ; 18 pages, 10 figure

Bar-Halo Friction in Galaxies II: Metastability

It is well-established that strong bars rotating in dense halos generally slow down as they lose angular momentum to the halo through dynamical friction. Angular momentum exchanges between the bar and halo particles take place at resonances. While some particles gain and others lose, friction arises when there is an excess of gainers over losers. This imbalance results from the generally decreasing numbers of particles with increasing angular momentum, and friction can therefore be avoided if there is no gradient in the density of particles across the major resonances. Here we show that anomalously weak friction can occur for this reason if the pattern speed of the bar fluctuates upwards. After such an event, the density of resonant halo particles has a local inflexion created by the earlier exchanges, and bar slowdown can be delayed for a long period; we describe this as a metastable state. We show that this behavior in purely collisionless N-body simulations is far more likely to occur in methods with adaptive resolution. We also show that the phenomenon could arise in nature, since bar-driven gas inflow could easily raise the bar pattern speed enough to reach the metastable state. Finally, we demonstrate that mild external, or internal, perturbations quickly restore the usual frictional drag, and it is unlikely therefore that a strong bar in a galaxy having a dense halo could rotate for a long period without friction.Comment: 13 pages, 11 figures, to appear in Ap

The luminosities of the brightest cluster galaxies and brightest satellites in SDSS groups

We show that the distribution of luminosities of Brightest Cluster Galaxies in an SDSS-based group catalog suggests that BCG luminosities are just the statistical extremes of the group galaxy luminosity function. This latter happens to be very well approximated by the all-galaxy luminosity function (restricted to Mr<-19.9), provided one uses a parametrization of this function that is accurate at the bright end. A similar analysis of the luminosity distribution of the Brightest Satellite Galaxies suggests that they are best thought of as being the second brightest pick from the same luminosity distribution of which BCGs are the brightest. I.e., BSGs are not the brightest of some universal satellite luminosity function, in contrast to what Halo Model analyses of the luminosity dependence of clustering suggest. However, we then use mark correlations to provide a novel test of these order statistics, showing that the hypothesis of a universal luminosity function (i.e. no halo mass dependence) from which the BCGs and BSGs are drawn is incompatible with the data, despite the fact that there was no hint of this in the BCG and BSG luminosity distributions themselves. We also discuss why, since extreme value statistics are explicitly a function of the number of draws, the consistency of BCG luminosities with extreme value statistics is most clearly seen if one is careful to perform the test at fixed group richness N. Tests at, e.g., fixed total group luminosity Ltot, will generally be biased and may lead to erroneous conclusions.Comment: 12 pages, 9 figures; v2 -- Revised to match version accepted in MNRAS. Includes a new section on using mark correlations to test extreme value statistic

Gas flow and dark matter in the inner parts of early-type barred galaxies

This paper presents the dynamical simulations run in the potential derived from the light distribution of 5 late-type barred spiral galaxies. The aim is to determine whether the mass distribution together with the hydrodynamical simulations can reproduce the observed line-of-sight velocity curves and the gas morphology in the inner regions of the sample barred galaxies. The light distribution is obtained from the $H$-band and the $I$-band combined together. The M/L is determined using population synthesis models. The observations and the methodology of the mass distribution modelling are presented in a companion paper. The SPH models using the stellar mass models obtained directly from the $H$-band light distributions give a good representation of the gas distribution and dynamics of the modelled galaxies, supporting the maximum disk assumption. This result indicates that the gravitational field in the inner region is mostly provided by the stellar luminous component. When 40% of the total mass is transferred to an axisymmetric dark halo, the modelled kinematics clearly depart from the observed kinematics, whereas the departures are negligible for dark mass halos of 5% and 20% of the total mass. This result sets a lower limit for the contribution of the luminous component of about 80%, which is in agreement with the maximum disk definition of the stellar mass contribution to the rotation curve (about 85%$\pm$10).Comment: 28 pages, 30 figures. Accepted for publication in A&A on 17/05/2004. High resolution figures on publicatio

Supermassive Black Holes and the Evolution of Galaxies

Black holes, an extreme consequence of the mathematics of General Relativity, have long been suspected of being the prime movers of quasars, which emit more energy than any other objects in the Universe. Recent evidence indicates that supermassive black holes, which are probably quasar remnants, reside at the centers of most galaxies. As our knowledge of the demographics of these relics of a violent earlier Universe improve, we see tantalizing clues that they participated intimately in the formation of galaxies and have strongly influenced their present-day structure.Comment: 20 pages, - This is a near-duplicate of the paper in Nature 395, A14, 1998 (Oct 1

Quantifying the fast outflow in the luminous Seyfert galaxy PG1211+143

We report two new XMM-Newton observations of PG1211+143 in December 2007, again finding evidence of the fast outflow of highly ionised gas first detected in 2001. Stacking the new spectra with those from two earlier XMM-Newton observations reveals strong and broad emission lines of FeXXV and OVIII, indicating the fast outflow to be persistent and to have a large covering factor. This finding confirms a high mass rate for the ionised ouflow in PG1211+143 and provides the first direct measurement of a wide angle, sub-relativistic outflow from an AGN transporting mechanical energy with the potential to disrupt the growth of the host galaxy. We suggest PG1211+143 may be typical of an AGN in a rapid super-Eddington growth phase.Comment: Accepted for publication in MNRAS. Extended version with new figures and table

A Model To Measure Supination And Pronation Of The Foot Over Different Levels Of Physiological Stress Using An In-Shoe Force Monitoring System

The purpose of this study was to create a diagnostic model of supination and pronation of the foot using vertical ground reaction forces. A size adjustable capacitive transducer retaining 960 individual pressure cells was used to assess orthopaedic parameters of gait cyale timing and vertical ground reaction forces. A pilot sample of five males were used for this model. The subjects were exposed to six experimental conditions. These being; a) a walk, b) jog, c) walk on treadmill, and d) three levels of perceived exertion (mild, moderate and hard running). Perceived exertion was measured with the Borg (RPE) scale. All subjects were measured in the same brand of athletic shoe to control for intershoe differences. The ptonation/supination model was determined by medial/lateral force and timing measurements of the calcaneus, forefoot prominence, arch, the first and fifth metatarsal heads and the toe off (end of gait cycle). Results indicated bi-Iateral differences in the medial and lateral force measurements of the calcaneus. Timing in this area was slightly different. Medial to lateral timing pronation was evidenced in the treadmill walking and moderate running condition. As well, the loading of the first and fifth metatarsal heads as a percentage of the gait cycle did not change over the running conditions. The preliminary results of five subjects provides for limited support of a vertical ground reaction model to assess pronation and supination. Further research with techniques such as high speed photography will allow for clarification of this model

Nuclear recoil measurements in Superheated Superconducting Granule detectors

The response of Superheated Superconducting Granule (SSG) devices to nuclear recoils has been explored by irradiating SSG detectors with a 70Me$\!$V neutron beam. In the past we have tested Al SSG and more recently, measurements have been performed with Sn and Zn detectors. The aim of the experiments was to test the sensitivity of SSG detectors to recoil energies down to a few ke$\!$V. In this paper, the preliminary results of the neutron irradiation of a SSG detector made of Sn granules 15-20$\mu$m in diameter will be discussed. For the first time, recoil energy thresholds of $\sim$1ke$\!$V have been measured.Comment: 7pages in Latex format, Preprint Bu-He 93/6 (University of Berne, Switzerland), four figures available upon request via [email protected] or [email protected]

DYNAMIC MEASUREMENT OF FORCE WITHIN THE SHOE DURING CONDITIONS OF PERCEIVED EXERTION

INTRODUCTION Athletics and recreation are becoming a very large component of modem day society. Now, more than ever, more people are becoming very active and involved in recreational pursuits that include aerobics and running/jogging. The resultant increase in activity has lead to a noted increase in injuries (Nigg, 1985; Mckenzie et al., 1985). James et al (cited in Cavanagh, 1990), in a study of 180 injured runners identified three categories of running injury problem areas. These areas being: a) training errors; b)anatomic factors (biomechanics); and c) shoes and surfaces. Two thirds of these injuries were accounted for by training errors (increased mileage or increased intensity). Training errors concerning sudden increases in mileage or intensity tend to subject the body to new or greater than expected physiological stressors. Voloshin and Wosk (1981), have investigated the relationship between heel strike shock wave transmission and joint degeneration in walking subjects. Taken one step further, the implications of damage to the muscle-skeletal system by running is noted by Cavanagh (1990). This combined with the Nigg et al. (1983) data that suggests a relationship between the hardness of the athletic (running) surface and the incidence of injury has serious implications for the recreational runner/athlete. Clarke et al. (1985) have highlighted the possible injurious force involved in tibial accelerations that are the result of the runner taking longer strides. Since most people retain a constant stride frequency, as velocity increases, the athlete tends to increase their stride length. The resultant increase in stride length increases impact forces at the joint. This combined with the increase of ground reaction forces with higher running speeds (Munro et al., 1987) identifies high impact forces as a major factor to be considered when investigating the causal nature of running injuries. Research into the type of shoe and ground reaction forces has been equivocal. Nigg and Bahlsen (1988) have stated that shoes with the hardest mid soles elicit the lowest maximal vertical forces. Conversely other research has indicated that shoe hardness is related to higher (vertical) loading rates. Listed above are a number of factors involved in the prediction of running injuries. Further research is needed to discover the causative factors involved in etiology of sport medicine running injuries. An analysis of running shoes, in particular the vertical ground reaction forces, may account for dynamic patterns of gait. Running at different levels of perceived exertion may elicit clues as to the biomechanics patterns that may be injurious to runners. For example, the gait of a runner at the beginning of the run may be markedly different from the gait at the end of the run. Variables such as intensity and distance will greatly affect the athlete's form as they become more tired. Thus, the number of running injuries (2/3 of Clarke's population) as a result of improper training may be the function of bad form (gait mechanics). An analysis under different levels of exertion will identify patterns of pressure with the foot that may have implications for the construction and design of athletic footwear as well as training methods for runners. This study was an attempt to understand the dynamic of in-shoe vertical ground reaction forces within the shoe under differing levels of perceived exertion. Research in the area of running shoe forces may lead to the development of a better product that will decrease the rate and type of running injuries

The masses of active neutrinos in the nuMSM from X-ray astronomy

In an extention of the Standard Model by three relatively light right-handed neutrinos (the nuMSM model) the role of the dark matter particle is played by the lightest sterile neutrino. We demonstrate that the observations of the extragalactic X-ray background allow to put a strong upper bound on the mass of the lightest active neutrino and predict the absolute values of the mass of the two heavier active neutrinos in the nuMSM, provided that the mass of the dark matter sterile neutrino is larger than 1.8 keV.Comment: 6 pages. revtex