Radiation Pressure Feedback in Galaxies

We evaluate radiation pressure from starlight on dust as a feedback mechanism in star-forming galaxies by comparing the luminosity and flux of star-forming systems to the dust Eddington limit. The linear LFIR--L'HCN correlation provides evidence that galaxies may be regulated by radiation pressure feedback. We show that star-forming galaxies approach but do not dramatically exceed Eddington, but many systems are significantly below Eddington, perhaps due to the "intermittency" of star formation. Better constraints on the dust-to-gas ratio and the CO- and HCN-to-H2 conversion factors are needed to make a definitive assessment of radiation pressure as a feedback mechanism.Comment: To appear in "Conditions and impact of star formation: New results with Herschel and beyond", Proceedings of the 5th Zermatt ISM symposium. 2 pages, 2 figure

A longitudinal study into science learning environments in Dunedin secondary schools

Science learning environments have been studied in secondary schools around the world. There is a long history of this going back over 30 years. The study presented here is unique in that it observes a single cohort in six schools in one city over a period of three years starting from when the students began high school and following them to their first external assessment.The students were surveyed using the Science Learning Environment Inventory and a short attitude and self efficacy questionnaire. The surveys were carried out late in the year for the first two years and about mid year in the third year. The students’ total credits in NCEA science were also collected as they became available. The total data set was collated so that each student’s data set was assigned an identifying number.The data were analysed using SPSS and comparisons made between each year and the relationships between the variables such as learning environment and NCEA achievement and variation in attitude against year level.The most striking finding was that year 10 presents as an anomaly and shows result in almost all variables, which do not sit between year 9 and year 11. This does show some correlation with the anecdotal evidence of teachers that this year is the most difficult group to teach but nevertheless warrants much more investigation

Direct Numerical Simulation of Radiation Pressure-Driven Turbulence and Winds in Star Clusters and Galactic Disks

[abridged] The pressure exerted by the radiation of young stars may be an important feedback mechanism in forming star clusters and the disks of starburst galaxies. However, there is great uncertainty in how efficiently radiation couples to matter in these high optical depth environments. In particular, it is unclear what levels of turbulence the radiation can produce, and whether the infrared radiation trapped by the dust opacity can give rise to heavily mass-loaded winds. In this paper we report a series of two-dimensional flux-limited diffusion radiation-hydrodynamics calculations performed with the code ORION in which we drive strong radiation fluxes through columns of dusty matter confined by gravity. We consider both systems where the radiation flux is sub-Eddington throughout the gas column, and where it is super-Eddington at the midplane but sub-Eddington in the atmosphere. In the latter, we find that the radiation-matter interaction gives rise to radiation-driven Rayleigh-Taylor instability, which drives supersonic turbulence at a level sufficient to fully explain the turbulence seen in Galactic protocluster gas clouds, and to make a non-trivial contribution to the turbulence observed in starburst galaxy disks. However, the instability also produces a channel structure in which the radiation-matter interaction is reduced because the radiation field is not fully trapped. For astrophysical parameters relevant to forming star clusters and starburst galaxies, we find that this effect reduces the net momentum deposition rate in the dusty gas by a factor of ~2-6 compared to simple analytic estimates, and that in steady state the Eddington ratio reaches unity and there are no strong winds. We provide an approximation formula, appropriate for implementation in analytic models and non-radiative simulations, for the force exerted by the infrared radiation field in this regime.Comment: 20 pages, 11 figures, emulateapj format, accepted to ApJ. This version has extra discussion, but the results are unchanged. For movies of simulation results, see http://www.ucolick.org/~krumholz/downloads.htm

Emotion monitoring online system: EMOSYS

This paper outlines the development, deployment and initial testing of a learning space environmental monitoring system. This system has been developed to monitor several environmental conditions including Temperature, Humidity, Sound Levels, Lighting levels and CO2 levels. The paper presents some initial testing with the system and discusses initial findings on the emotional wellbeing of students from learning spaces that have been monitored

The Ionization State of Sodium in Galactic Winds

Roughly 80% of Ultraluminous Infrared Galaxies (ULIRGs) show blue shifted absorption in the resonance lines of neutral sodium, indicating that cool winds are common in such objects, as shown by Rupke et al and by Martin. The neutral sodium (NaI) columns indicated by these absorption lines are ~ 10^{13}-3x10^{14}/cm^2, while the bolometric luminosity varies by a factor of only four. We show that the gas in ULIRG outflows is likely to be in photoionization equilibrium. The very small ULIRG sample of Goldader et al. demonstrates that the ratio of ultraviolet flux to far infrared flux varies by a factor $\sim100$ from object to object. While the Goldader sample does not overlap with those of Rupke et al. and Martin, we show that such a large variation in ultraviolet flux will produce a similar variation in the column of neutral sodium for a fixed mass flux and density. However, if the cold gas is in pressure equilibrium with a hot outflow with a mass loss rate similar to the star formation rate, the range of ionization state is significantly smaller. Measurements of the UV flux for objects in the Martin and Rupke et al. catalogs will definitively determine if photoionization effects are responsible for the wide variation seen in the sodium columns. If they are, a determination of the gas density and mass loss rate in the cool winds will follow, with attendant improvements in our understanding of wind driving mechanisms and of the effects of galaxies on their surroundings.Comment: 14 pages, 5 figures, submitted to Ap

Physiological correlates of performance in international-standard squash players

Tactical, technical and fitness factors are important for success in elite squash. While tactical and endurance fitness aspects have been explored, altered demands that have resulted from rule changes and absence of specific tests of high-intensity exercise capabilities have prevented identification of elements of fitness that correlate with performance in elite-standard players. Accordingly, the purpose of this study was to investigate relationships between test scores and player rank in such players. With institutional ethics approval, 31 players from the England Squash performance programme participated (11 women and 20 men, mean±SD body mass 62.4±5.5 kg and 73.1±7.5 kg respectively). After habituation, participants completed countermovement and drop-jump tests, squash-specific tests of change-of-direction speed and multiple-sprint ability and the multistage fitness test in one test session. Short recoveries were allowed between tests. World rank at the time of testing was obtained from the Professional Squash Association website. In men, change-of-direction speed (??=?0.59, p?=?0.02, n?=?14) multiple-sprint ability (??=?0.78, p<0.01, n?=?13) and fastest sprint from the multiple-sprint test (??=?0.86, p<0.01, n?=?13) correlated with world rank. In women, only fastest repetition from the multiple-sprint test correlated with world rank (??=?0.65, p?=?0.04, n?=?10). Measures of high-intensity exercise capability correlated with world rank in elite-standard men and women players. Endurance capability did not relate to rank in either the men or women. The results suggest that high-intensity, variable-direction exercise capabilities are important for success in elite squash